Allowable movement of wavefront-guided contact lens corrections in normal and keratoconic eyes

PURPOSE

The goal was to use SyntEyes modelling to estimate the allowable alignment error of wavefront-guided rigid contact lens corrections for a range of normal and keratoconic eye aberration structures to keep objectively measured visual image quality at or above average levels of well-corrected normal eyes. Secondary purposes included determining the required radial order of correction, whether increased radial order of the corrections further constrained the allowable alignment error and how alignment constraints vary with keratoconus severity.

METHODS

Building on previous work, 20 normal SyntEyes and 20 keratoconic SyntEyes were fitted with optimised wavefront-guided rigid contact lens corrections targeting between three and eight radial orders that drove visual image quality, as measured objectively by the visual Strehl ratio, to near 1 (best possible) over a 5-mm pupil for the aligned position. The resulting wavefront-guided contact lens was then allowed to translate up to ±1 mm in the x- and y-directions and rotate up ±15°.

RESULTS

Allowable alignment error changed as a function of the magnitude of aberration structure to be corrected, which depends on keratoconus severity. This alignment error varied only slightly with the radial order of correction above the fourth radial order. To return the keratoconic SyntEyes to average levels of visual image quality depended on maximum anterior corneal curvature (Kmax). Acceptable tolerances for misalignment that returned keratoconic visual image quality to average normal levels varied between 0.29 and 0.63 mm for translation and approximately ±6.5° for rotation, depending on the magnitude of the aberration structure being corrected.

CONCLUSIONS

Allowable alignment errors vary as a function of the aberration structure being corrected, the desired goal for visual image quality and as a function of keratoconus severity.

Comparative evaluation of biomechanical changes and aberration profile following accelerated collagen cross-linking using hypo-osmolar and iso-osmolar riboflavin: A prospective study

PURPOSE

To compare the changes encountered in corneal biomechanics and aberration profile following accelerated corneal collagen cross-linking (CXL) using hypo-osmolar and iso-osmolar riboflavin in corneal thicknesses of <400 and >400 microns, respectively.

METHODS

This is a prospective, interventional, comparative study involving 100 eyes of 75 patients with progressive keratoconus. Eyes were divided into two groups based on corneal thickness: group 1 included eyes with a corneal thickness of <400 microns who underwent hypo-osmolar CXL, and group 2 included eyes with a corneal thickness of >400 microns who underwent iso-osmolar CXL. Corneal biomechanical and aberration profiles were evaluated and compared between groups.

RESULTS

In group 1, all higher-order aberrations (HOA) except secondary astigmatism significantly decreased from baseline; however, in group 2, only coma and trefoil decreased. The corneal resistance factor and corneal hysteresis significantly improved in both groups, which was significantly greater in group 2 than in group 1. The change in inverse radius, deformation amplitude, and tomographic biomechanical index was significantly improved in group 2 as compared to group 1.

CONCLUSION

Improvement in corrected distance visual acuity and decrease in HOA were significantly better in the hypo-osmolar CXL group; however, the improvement in biomechanical strength of the cornea was significantly better in the iso-osmolar group.

Optical Quality in Keratoconus Is Associated With Corneal Biomechanics

PURPOSE

To evaluate the correlations between corneal biomechanical indices from dynamic Scheimpflug assessment and optical quality assessed as higher-order aberrations (HOAs) using a Hartmann-Shack ocular wavefront sensor in patients with keratoconus (KC).

METHODS

In this prospective, observational case series, the eyes with KC or KC suspect (KCS) from Osaka University Hospital, Osaka, Japan, were analyzed. Corneal biomechanical assessment was performed using Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany), and ocular wavefront aberrations were measured using the KR-1W (Topcon Corp, Tokyo, Japan). Correlations between the biomechanical indices and ocular HOAs were assessed. Corneal biomechanical indices included the deformation amplitude ratio within 2 mm, integrated radius, stiffness parameter at the first applanation, and the linear Corvis Biomechanical Index. Wavefront data of the central 4-mm region were expanded up to the sixth order of Zernike polynomials. The magnitudes of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were calculated by Zernike vector analysis and then used as ocular HOA parameters along with total HOAs.

RESULTS

Thirty-four KC eyes and 37 KCS eyes were included. KC eyes showed significant correlations between ocular HOAs and biomechanics, whereas there were few significant correlations in KCS eyes. In KC eyes, deformation amplitude ratio within 2 mm, integrated radius, and Corvis Biomechanical Index beta showed stronger correlations with coma among the wavefront parameters.

CONCLUSIONS

Corneal biomechanical indices correlated with ocular HOAs in patients with KC. In particular, there was a strong association with the increase in coma caused by inferosuperior asymmetry of the shape of the cornea in patients with KC.

The Relationship Between Preoperative Anterior Corneal Higher Order Aberrations and Topography-Guided Excimer Ablation Depth

PURPOSE

To determine the correlation and relative contribution of preoperative anterior corneal Zernike coefficients to higher order aberration ablation depth (HOA-AD) with topography-guided excimer laser correction.

METHODS

Retrospective study of 46,271 consecutive preoperative virgin eyes. Anterior corneal Zernike coefficients (C6 to C27) and HOA-AD data on a 6.5-mm optical zone were analyzed from the Contoura (Alcon Laboratories, Inc) treatment software. Pearson correlations were performed to assess the relationship between Zernike coefficients and HOA-AD.

RESULTS

A strong direct relationship was found between the total root mean square (RMS) anterior corneal HOA and HOA-AD (R = 0.84; P < .001). The 3rd order HOAs (C6 to C9) accounted for most of the HOA-AD (R = 0.83; P < .001). Zernike orders 4, 5, and 6 had significantly weaker correlations (4th order: R = 0.30; 5th order: R = 0.38; 6th order: R = 0.29). Vertical coma was the individual HOA with the highest correlation (R = 0.59; P < .001). Combining vertical and horizontal coma as total RMS coma increased the correlation significantly (R = 0.76; P < .001). The average HOA-AD increased by 1.5 µm for each additional 0.1-µm increment of total RMS coma.

CONCLUSIONS

Anterior corneal Zernike coefficients directly and strongly correlate to the HOA-AD, with anterior corneal coma having the greatest contribution to HOA-AD. [J Refract Surg. 2020;36(8):506-510.].

Spherical Aberration Customization to Extend the Depth of Focus With a Clinical Adaptive Optics Visual Simulator

PURPOSE

To evaluate the use of the VAO adaptive optics visual simulator (Voptica SL, Murcia, Spain) for customization of spherical aberration to increase depth of focus.

METHODS

Through-focus visual acuity with both high- and low-contrast letters from +1.00 to -3.00 diopters (D) was measured in 17 dilated eyes with three different induced amounts of spherical aberration for a 4.5-mm pupil diameter: control (0 µm), -0.15 µm, and -0.30 µm.

RESULTS

The defocus curves followed the same behavior with both values of contrast, but the visual acuity was 0.2 logMAR lower with low contrast. The mean values of high-contrast logMAR visual acuity at far, intermediate (67 cm), and near (40 cm) were -0.10, 0.11, and 0.37 for control, 0.04, 0.00, and 0.15 for -0.15 µm, and 0.23, 0.00, and 0.06 for -0.30 µm conditions. The 95% confidence interval ranged from ±0.14 to ±0.45 logMAR and the middle 50% of the distribution was approximately 0.2 logMAR.

CONCLUSIONS

Negative values of spherical aberration extend the depth of focus in different ways depending on each patient. The VAO is a new instrument that allows the visual customization of spherical aberration to enhance depth of focus. [J Refract Surg. 2020;36(4):223-229.].

Comparison of the Distribution of Lenticule Decentration Following SMILE by Pupil Center or Tear Film Mark Centration

PURPOSE

To investigate lenticule decentration following small incision lenticule extraction (SMILE) via the pupil center or tear film mark centration method and compare induction of corneal higher order aberrations (HOAs) between the two methods.

METHODS

This study analyzed decentration values obtained from tangential topography difference maps of 100 eyes (100 patients) undergoing SMILE with the pupil center (n = 50) or tear film mark (n = 50) centration method. Total HOAs and component aberrations were measured preoperatively and 6 months postoperatively. Relationships between the magnitudes of decentration and induced corneal HOAs were assessed.

RESULTS

Both vertical and total decentered displacement were significantly different (P < .001) between the two centration groups. A significant relationship between the preoperative pupillary offset and decentration was noted in the pupil center group (P < .001), but not in the tear film mark group (P = .530). Significantly greater induction of total HOAs, coma, and vertical coma (all P < .001), as well as horizontal coma (P = .001) and spherical aberration (P = .023), were observed in the pupil center group. Association between the total decentered displacement and induced total HOAs (P < .001), as well as all other significantly increased phenomena, was also significant in the pupil center group. Differences in decentered displacement and induced corneal HOAs were significant for preoperative pupillary offset (angle kappa) greater than 200 µm, but not for angle kappa less than 200 µm.

CONCLUSIONS

SMILE with tear film mark centration can yield improved treatment centration and less induction of total HOAs, coma, and spherical aberrations. [J Refract Surg. 2020;36(4):239-246.].

An Alternative Wavefront Reconstruction Method for Human Eyes

PURPOSE

To expand upon and clinically demonstrate the results of a new polynomial decomposition method.

METHODS

To discuss the theoretical considerations comparing the qualitative and quantitative information produced by the Zernike coefficients and a new polynomial decomposition basis, in a comparative series of theoretical and clinical case studies.

RESULTS

These comparative studies validate the novel polynomial basis that decomposes the wavefront, with clear segregation of the higher and lower aberrations. There is no artifactual reduction of some of the higher order aberration coefficients, providing a more clinically relevant retinal image quality prediction.

CONCLUSIONS

Some of the inherent limitations of the Zernike polynomials in clinical ophthalmic applications can be solved by a novel set of polynomials forming an alternative higher order basis. The new basis provides a clear separation between modes containing lower order terms versus higher order terms and offers clinicians a more clinically realistic wavefront analysis. [J Refract Surg. 2020;36(2):74-81.].

Effect of Anterior Corneal Higher-Order Aberration Ablation Depth on Primary Topography-Guided LASIK Outcomes

PURPOSE

To investigate the contribution of anterior corneal higher-order aberration ablation depth (HOA-AD) to topography-guided outcomes.

METHODS

This was a retrospective comparative analysis of 9,722 consecutive eyes undergoing laser in situ keratomileusis (LASIK) treated on the clinically measured refractive cylinder with Contoura software (Alcon Laboratories, Inc., Fort Worth, TX). Outcomes of the 3,246 eyes with the shallowest HOA-AD (first tercile: 5.4 ± 0.9 µm) were compared to the 3,362 eyes with the deepest HOA-AD (last tercile: 11.0 ± 1.7 µm).

RESULTS

The HOA-AD followed a left-skewed normal distribution (R² = 0.98) with a mean ± standard deviation of 8.02 ± 3.00 µm, with 1.8% of eyes greater than 15 µm. The efficacy index of shallow versus deep HOA-AD eyes was identical (0.98 ± 0.07 vs 0.98 ± 0.09; P = .99), with a similar percentage having spherical equivalent within ±0.50 diopters (D) (95.2% vs 95.0%; P = .71) and within ±0.75 D (98.9% vs 98.7%; P = .46) of intended target. The safety index (1.00 ± 0.03 vs 1.00 ± 0.04; P = .19) and Alpins correction index (1.00 ± 0.39 vs 1.01 ± 0.43; P = .53) were also identical. The mean postoperative refractive astigmatism difference between the shallow (0.15 D) and deep (0.20 D) groups was 0.05 D. The 3-month laser re-treatment rate was greater in the deep group (0.83% vs 0.37%; P = .02), but less than 1% for both groups.

CONCLUSIONS

The contribution of topography-guided HOA-AD to clinical outcomes in most virgin eyes is negligible, with excellent efficacy, accuracy, and safety in both the deep and shallow ablation groups. Eyes with deep HOA-AD greater than 15 µm trend to lesser outcomes, but should not be excluded from topography-guided surgery. [J Refract Surg. 2019;35(12):754-762].

Relating wavefront error to visual acuity in pre- and post-LASIK eyes: a comparison of methods

Contrast threshold and visual Strehl ratio methods are used to predict visual acuity from wavefront error for a sample population of pre- and post-LASIK patients. Relative error (in logMAR) between predicted and measured visual acuity values are computed for each method and compared using paired t-tests. Differences in aberration data between pre- and post-LASIK eyes are then evaluated. The visual acuity prediction using visual Strehl proved to be more accurate for pre-LASIK patients than contrast threshold. However, both methods are comparable for post-LASIK patients.

Do Polymer Coatings Change the Aberrations of Conventional and Wavefront-guided Scleral Lenses?

SIGNIFICANCE

The findings of this study indicate that patients could simultaneously be offered the individualized optical correction of wavefront-guided (WFG) lenses and the superior comfort afforded by polymer coatings. This could be helpful to patients with ectasia suffering ocular dryness or dependent on scleral lenses for lengthy periods of wear.

PURPOSE

Wavefront-guided scleral lenses target lower- and higher-order aberrations of individual eyes using submicrometer-level contours in the anterior lens surface. Hydrophilic polyethylene glycol (PEG) polymer coatings applied to lens surfaces improve comfort and wettability. This study aimed to quantify aberration changes (e.g., masking) when applying polymer coatings to WFG and conventional scleral lenses.

METHODS

Two control lenses (remained uncoated) and 14 experimental lenses (two repeated builds of seven aberration designs: one spherical, two coma, four full WFG [second- to fifth-order aberrations]) were manufactured, and aberrations were measured (mean of three) by two operators before and after coating. Root mean square (RMS) and visual image quality (logVSX) differences were calculated for 6-mm diameters.

RESULTS

Median RMS aberration change due to coating was 0.012 μm (range, 0.008 to 0.057 μm). Maximum logVSX change due to coating was 0.073, predicting an approximately one letter change in acuity. Instrument sensitivity was 0.002 μm. Acute instrument and operator variabilities (standard deviations of individual [second- to fifth-order Zernikes] were all <0.027 μm). Longitudinal variability (control lenses) was low: all less than 0.017 μm. Although RMS of differences between repeated builds of all lenses was less than 0.25 D and not statistically significant, relatively, manufacture constituted the major variability, and RMS difference between repeated builds was at least four times greater than the effect of coating (median, 0.167 μm; range, 0.088 to 0.312 μm).

CONCLUSIONS

Application of polymer coatings caused measurable changes in aberrations of WFG and conventional scleral lenses; however, these were clinically and statistically insignificant and within variability of repeated lens manufacture. In their current states, WFG lenses and polymer coatings could be used simultaneously.

Peripheral refraction and spherical aberration profiles with single vision, bifocal and multifocal soft contact lenses

PURPOSE

To compare the peripheral refraction and spherical aberration profiles along three visual field meridians of 16 commercial single vision (SV), bifocal (BF) and multifocal (MF) test contact lenses with a single vision control.

METHOD

Forty-four participants [24.2±2.4 years, SE: -0.50 to -4.50D] were randomly fitted, contra-laterally, with 6 SV's [Air Optix Aqua (control), Acuvue Oasys, Biofinity, Clariti, Night & Day and Proclear], 3 BF's [Acuvue Bifocal low and high add, MiSight] and 8 MF's [Proclear D & N in 1.5 and 2.5D adds; AirOptix, PureVision low & high adds]. Peripheral refraction was performed across horizontal, oblique and vertical meridians, with lenses on eye using the BHVI-EyeMapper. The power vectors M, J₀, J₄₅ and the spherical aberration coefficient were analysed. The peripheral refraction and aberration profiles of the test lenses were compared with the profiles of the control lens using curvature and slope coefficients.

RESULTS

Compared to the control, a relative peripheral hyperopic shift (M), a less negative J₀ curvature coefficient along the horizontal meridian, a less positive J₀ curvature coefficient along the vertical meridian, a less negative J₄₅ curvature coefficient along the oblique meridian and a more positive spherical aberration curvature coefficient along most meridians was seen with the Acuvue Bifocal and all center-near multifocal lenses. For the center-distance multifocal lenses the direction of the curvature coefficients of the same refraction and aberration components was opposite to that of the center-near lenses. The greatest differences in the slope coefficients when compared to the control were found for the Acuvue Bifocal lenses and all multifocal contact lenses for the refractive component M and the spherical aberration coefficient along the horizontal visual field meridian, with the Acuvue Bifocal and the center-near multifocal lenses having more positive coefficients and the center-distance lenses having more negative coefficients.

CONCLUSION

When worn on eye, different commercially available lens types produce differences in the direction and magnitude of the peripheral refraction and spherical aberration profiles along different visual field meridians. This information may be relevant to refractive development and myopia control.

Predictors of Visual Acuity Improvement and Supernormal Vision After Refined Single-Step Transepithelial Photorefractive Keratectomy

PURPOSE

To investigate predicting factors of visual acuity improvement and achieving uncorrected (UDVA) or corrected (CDVA) distance visual acuity supernormal vision (⩾ 15/10; Snellen 20/13) 1 year after refined transepithelial photorefractive keratectomy (TransPRK).

METHODS

In this retrospective case series, a total of 155 eyes with myopia (mean ± standard deviation = -3.53 ± 1.81 diopters) with and without astigmatism (range = 0.25 to 4.50 diopters) were recruited and observed for 1 year. Patients underwent refined single-step TransPRK using the SCHWIND AMARIS 500 laser (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). The main predicting factors of postoperative supernormal vision and visual acuity improvements were sought by statistical modeling.

RESULTS

Logistic models showed mesopic contrast sensitivity, high laser fluence, and coma higher-order aberration (HOA) as predicting factors for both UDVA and CDVA super-normal vision. Myopia, astigmatism, dynamic cyclotorsion correction, optical zone, and transitional zone showed associations only in simple models and were not retained in multivariable models. According to the linear regression models, CDVA, mesopic contrast sensitivity, coma HOA, and keratometry were common predictors of both postoperative UDVA and CDVA improvement compared to preoperative UDVA. Astigmatism, optical and transitional zones, and high laser fluence were common predictors only in simple regression models.

CONCLUSIONS

Through statistical modeling, preoperative CDVA, mesopic contrast sensitivity, coma HOA, and simulated keratometry were found to be the main factors that predicted improvement of both postoperative CDVA and UDVA compared to preoperative CDVA. Furthermore, mesopic contrast sensitivity, coma HOA, and high laser fluence were the common predictors of achieving both CDVA and UDVA supernormal vision 1 year after refined single-step TransPRK. [J Refract Surg. 2019;35(12):771-780.].

Status of Residual Refractive Error, Ocular Aberrations, and Accommodation After Myopic LASIK, SMILE, and TransPRK

PURPOSE

To analyze residual refractive error, ocular aberrations, and visual acuity (VA) during accommodation simultaneously with ocular aberrometry in eyes after laser-assisted in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), and transepithelial photorefractive keratectomy (TransPRK).

METHODS

Ocular aberrometry (Tracey Technologies, Houston, TX) was performed 3 months after LASIK (n = 95), SMILE (n = 73), and TransPRK (n = 35). While measuring the aberrations, VA was measured at distance (20 ft), intermediate (60 cm), and near (40 cm) targets. The examinations were done monocularly. A parallel group of age-matched normal eyes (n = 50) with 20/20 Snellen distance VA also underwent aberrometry.

RESULTS

Distribution of residual spherical error of LASIK eyes matched the normal eyes the best, followed by SMILE and TransPRK. However, the distribution of cylindrical error of the SMILE eyes was distinctly different from the rest (P < .05). The SMILE eyes tended to be undercorrected by approximately 0.25 diopters (D) on average at all reading targets compared to LASIK eyes (P < .05). The undercorrection was greater when the magnitude of the preoperative cylinder exceeded 0.75 D (P < .05). The VA of LASIK and SMILE eyes was similar to normal eyes at all targets, but the TransPRK eyes were marginally inferior (P < .05). Only the ocular defocus changed differentially between the study groups during accommodation and the magnitude of change was least for TransPRK eyes (P < .05). However, postoperative near and intermediate accommodation of LASIK eyes were similar to normal eyes, followed by SMILE eyes and then TransPRK eyes.

CONCLUSIONS

The refractive and aberrometric status of the LASIK eyes was closest to the normal eyes. The SMILE procedure may benefit from slight overcorrection of the preoperative refractive cylinder. [J Refract Surg. 2019;35(10):624-631.].

Comparison of Wavefront-Optimized Ablation and Topography-Guided Contoura Ablation With LYRA Protocol in LASIK

PURPOSE

To compare the refractive outcomes and aberration data analysis of wavefront-optimized (WFO) ablation and topography-guided Contoura ablation (TGCA) (Contoura on the WaveLight laser; WaveLight GmbH, Erlangen, Germany) in patients who had laser-assisted in situ keratomileusis (LASIK) for myopia or myopic astigmatism.

METHODS

In this comparative contralateral eye study, patients who underwent LASIK with TGCA in one eye and with WFO ablation in the fellow eye were analyzed. Aberration measurements and corneal topography were analyzed using the WaveLight Oculyzer II diagnostic device (Alcon Laboratories, Inc., Fort Worth, TX). Total corneal higher order aberrations (HOAs) including vertical and oblique astigmatism (Z² ₂, Z² _-2), coma (Z³ ₁, Z³ _-1), trefoil (Z³ ₃, Z³ _-3), spherical aberration, and Q value were analyzed. These measurements were taken preoperatively and 3 months postoperatively.

RESULTS

This study comprised 32 patients. There were no significant differences between both procedures according to postoperative uncorrected and corrected distance visual acuity values, refractive errors, and manifest refraction spherical equivalents within ±0.50 diopters (D) of emmetropia (P > .05). The preoperative corneal HOAs and Q values were also similar between the groups (P > .05). At 3 months postoperatively, the vertical and horizontal coma values in the WFO ablation group were statistically significantly higher compared to the TGCA group (P = .013 and .020, respectively). Less stromal tissue was ablated in the TGCA group compared to the WFO ablation group (P < .001).

CONCLUSIONS

Although WFO ablation and TGCA protocols had statistically similar visual outcomes, the TGCA protocol was associated with a significantly lower induction in vertical and horizontal coma and smaller amount of tissue ablation compared to WFO ablation. [J Refract Surg. 2019;35(4):222-229.].

Functional Optical Zone and Centration Following SMILE and LASIK: A Prospective, Randomized, Contralateral Eye Study

PURPOSE

To compare centration and functional optical zone (FOZ) after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK).

METHODS

In this prospective, randomized, single-masked, paired-eyed, clinical trial, 70 patients received SMILE in one eye and LASIK in the other eye for myopia and myopic astigmatism. FOZ was calculated using custom software on 3-month postoperative refractive power maps (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany). Programmed treatment area was defined as the total area of the programmed OZ plus the transition zone. Centration was evaluated by the linear distance between FOZ centroid and the pupil center and the corneal apex.

RESULTS

The average preoperative spherical equivalent (-5.38 ± 1.65 vs -5.45 ± 1.61 diopters [D]), postoperative spherical equivalent (0.05 ± 0.39 vs 0.06 ± 0.39 D), uncorrected distance visual acuity (0.01 ± 0.13 vs 0.00 ± 0.08 logMAR), and corrected distance visual acuity (-0.07 ± 0.10 vs -0.07 ± 0.10 logMAR) were comparable in SMILE- and LASIK-treated eyes of the 60 patients with complete datasets (P > .419). Postoperative increase in spherical aberration was lower in SMILE than in LASIK (0.08 ± 0.16 vs 0.17 ± 0.18 µm, P = .002). The FOZ area was significantly larger in SMILE than in LASIK (30.25 ± 3.60 vs 29.21 ± 3.72 mm²), despite the smaller programmed OZ diameter (6.48 ± 0.08 vs 6.52 ± 0.11 mm) and smaller programmed treatment area (33.87 ± 0.81 vs 46.30 ± 2.61 mm², P < .037). Pupil centration (0.43 ± 0.21 vs 0.41 ± 0.22 mm) and apex centration (0.48 ± 0.24 vs 0.48 ± 0.22 mm) were comparable between SMILE and LASIK (P > .694).

CONCLUSIONS

SMILE created a larger FOZ than LASIK, despite the smaller programmed OZ. This may be due to a difference in the biomechanical response between the two procedures. Visual outcome and centration were comparable between SMILE and LASIK. [J Refract Surg. 2019;35(4):230-237.].

Adjustment of Spherical Equivalent Correction According to Cap Thickness for Myopic Small Incision Lenticule Extraction

PURPOSE

To evaluate the amount of spherical equivalent correction for three different cap thicknesses (120, 130, and 140 µm) during myopic small incision lenticule extraction (SMILE) and determine the association between the amount of spherical equivalent correction and several variables in each cap thickness group.

METHODS

In this retrospective, comparative, observational case series study, the authors compared refractive errors, keratometric values, laser setting (sphere correction, cylinder correction, spherical equivalent correction, optical zone, and cap diameter), and spherical aberration measured preoperatively and at 3 months postoperatively between three different cap thickness groups: 120 µm (n = 554), 130 µm (n = 377), and 140 µm (n = 90). Multiple linear regression analyses were used to determine the associations between the amount of spherical equivalent correction and several variables, including age, preoperative spherical equivalent, optical zone diameter, central corneal thickness, preoperative mean keratometric values, and preoperative corneal asphericity.

RESULTS

According to cap thickness, attempted correction is adjusted to achieve the same refractive outcomes for different cap thicknesses. There were significant differences in the amount of sphere correction and spherical equivalent correction, as well as lenticule thickness, among subgroups. Changes in keratometric values, corneal asphericity, and spherical aberration were also significantly different among subgroups (all P < .001). Changes in keratometric values, corneal asphericity, and spherical aberration significantly increased as cap thickness increased. Preoperative spherical equivalent mainly influenced the amount of spherical equivalent correction in each group.

CONCLUSIONS

Dioptric adjustment of spherical equivalent correction according to cap thickness is essential to obtain similar refractive outcomes in myopic SMILE procedures. [J Refract Surg. 2019;35(3):153-160.].

Effect of Crystalline Lens Aberrations on Adaptive Optics Simulation of Intraocular Lenses

PURPOSE

To evaluate the impact of the lens aberrations on the adaptive optics visual simulation of pseudophakic intraocular lens (IOL) profiles.

METHODS

In 20 right phakic eyes, lens higher order aberrations (HOAs) were calculated as the whole eye minus the corneal aberrations. Visual simulation using low and high contrast corrected distance visual acuity (CDVA) testing was carried out with the VAO instrument (Voptica, SL, Murcia, Spain), considering three optical conditions of the lens: removing HOA (no lens-HOA), removing spherical aberration (no lens-SA), and with lens HOA (natural condition). In addition, a through-focus visual simulation of a trifocal diffractive IOL profile with high contrast CDVA was also measured in two conditions: no lens-HOA and natural condition. Three different pupil sizes (3, 4.5, and 6 mm) were tested for all conditions.

RESULTS

There were no significant intersubject differences between the three optical conditions and in the IOL simulation for all pupil sizes (P > .05). For 4.5- and 6-mm pupils, mean VA values of the no-lens SA and no lens-HOA conditions were similar and slightly worse than those of the natural condition. Individual differences between the no lens-HOA condition and the other two optical conditions, estimated as 95% limits of agreement, were acceptable for 3-mm pupil but worse as pupil diameter increased.

CONCLUSIONS

The effect of lens aberrations on visual simulation is imperceptible for a small pupil diameter of 3 mm. Although the increment of pupil size increases the probability of patients with significant visual impact of lens HOAs, the mean intersubject VA differences are negligible. [J Refract Surg. 2019;35(2):126-131.].

Longitudinal Chromatic Aberration and Polychromatic Image Quality Metrics of Intraocular Lenses

PURPOSE

To measure longitudinal chromatic aberration (LCA) of various intraocular lenses (IOLs) and to assess LCA effects on polychromatic image quality with a focus on multifocal IOL designs.

METHODS

The LCA values of four multifocal IOL models (three diffractive models: AT LARA 829MP and AT LISA 809M [both from Carl Zeiss Meditec AG, Jena, Germany] and Restor SN6AD1 [Alcon Laboratories, Inc., Fort Worth, TX] and one refractive model [Mini Well Ready; SIFI Medtech, Sant'Antonio, Italy]) were compared with that of their monofocal counterparts. Optical properties were assessed using an optical bench device with spectral filters. LCA was calculated as a difference of a lens power at 480 and 644 nm. The optical quality was evaluated objectively by means of modulation transfer function metrics.

RESULTS

At far, LCA of an aphakic model eye (1.04 diopters [D]) increased with the AT Lisa, Restor, and Mini Well IOLs to 1.40, 1.91, and 1.27 D, respectively, but decreased to 0.78 D with the AT Lara IOL. The AT Lisa and Restor IOLs showed comparable results with their monofocal platforms. A near-focus LCA decreased only in the diffractive IOLs. At far, the polychromatic modulation transfer function was reduced in all IOLs, but LCA effects were attenuated at near.

CONCLUSIONS

Multifocal IOLs and their monofocal counterparts show similar material dispersion. Multifocal diffractive IOLs proved effective in reducing LCA, but the efficiency of the LCA correction differed depending on the optical design. LCA adversely affects the polychromatic image quality. [J Refract Surg. 2018;34(12):832-838.].

A novel method in correcting aberropia using pin hole soft contact lenses: A case report

Aberropia leads to decrease in image quality due to higher order aberrations (HOA). Correction of these HOA poses a great challenge to clinicians. A case report is presented here where a 30 year old male visited with complaints of cloudy vision, diplopia in reduced illumination along with inferior vertical elongation of light during night time in the right eye since 6 years. The unaided visual acuity was found to be 0.0 Log MAR units and near acuity was N6. The patient did not accept any correction in subjective refraction. The aberrometry findings revealed vertical trefoil and vertical coma of -0.33 μm and 0.53 μm in the right eye and -0.07 μm and 0.12 μm in the left eye. Orbscan revealed a difference of 30 μm and 25 μm between the anterior and posterior float for the right and left eye respectively. Due to the significant increase in irregular astigmatism, vertical coma and vertical trefoil in the right eye, rigid gas permeable lenses and Rose K lenses were tried, but the symptoms did not reduce. This was due to the increase in posterior corneal astigmatism as the posterior float was more than 25 μm in the right eye which led to a diagnosis of early keratoconus. As the decrease in pupil size reduces HOA, a pin hole (2.5 mm pupil) soft contact lens was tried which reduced the symptoms. Hence a novel method is proposed to eliminate HOA which corrects aberropia by using pin hole soft contact lenses.

Age-Related Changes in Corneal Spherical Aberration

PURPOSE

To analyze the age-related changes in corneal spherical aberration (CSA) and higher order aberrations (HOAs) and to develop a novel model to estimate the change in CSA with age.

METHODS

This was a cross-sectional study of the right eyes of 3,769 patients. Anterior corneal spherical aberration (ASA), posterior corneal spherical aberration (PSA), total corneal spherical aberration (TSA), and the root mean square of corneal HOAs were measured using a Scheimpflug tomographer. Smoothed fitting curves were plotted as a function of age and the average change in spherical aberration was calculated for different ages.

RESULTS

The mean magnitude of ASA, PSA, TSA, and HOAs (6 and 4 mm) were 0.270 ± 0.111, -0.144 ± 0.031, 0.228 ± 0.120, 0.453 ± 0.194, and 0.141 ± 0.075 µm, respectively. All parameters showed a statistically significant non-linear change with age. The age after which the aberrations increased at a faster rate, namely the turning points of age, were 39 years for ASA, PSA, TSA, and 6-mm HOAs (95% confidence interval [CI]: 35 to 42, 36 to 41, 36 to 42, and 35 to 56 years, respectively) and 46 years for 4-mm HOAs (95% CI: 36 to 56 years). There were significant increases in increment rates after the turning points. The average change of TSA was -0.013 µm/10 years from 18 to 39 years and 0.057 µm/10 years after 39 years. There were statistically significant correlations between ASA and TSA (r = 0.976, P < .001) and PSA and TSA (r = 0.192, P < .001), but not between ASA and PSA (r = -0.003, P = .835).

CONCLUSIONS

CSA and HOAs increased non-linearly with age and became more positive after 39 and 46 years of age, respectively. Based on the increment rates and turning points of age, a novel model is provided to help calculate the value required to compensate for the increasing CSA associated with the aging cornea. [J Refract Surg. 2018;34(11):760-767.].

Comparison of Single-Step Transepithelial Photorefractive Keratectomy With or Without Mitomycin C in Mild to Moderate Myopia

PURPOSE

To compare efficacy and safety of single-step transepithelial photorefractive keratectomy (PRK) with or without mitomycin C (MMC) in patients with mild to moderate myopia.

METHODS

Patients with mild to moderate myopia (≤ -5.50 diopters [D]) underwent single-step transepithelial PRK using the Amaris laser (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). Total ablation depth (epithelium and stroma) was 160 μm or less. The right eye of each patient was treated with 0.02% MMC for 10 seconds, whereas the left eye did not receive any MMC. Corneal haze, endothelial cell indices, refraction, visual acuity, contrast sensitivity, and higher order aberrations were assessed preoperatively and postoperatively.

RESULTS

In this comparative case series, 71 patients (16 men and 55 women; 142 eyes) were enrolled. Mean patient age was 27.97 ± 5.74 years. Mean preoperative spherical equivalent of patients' right and left eyes were -3.20 ± 1.20 and -3.30 ± 1.20 diopters, respectively (P = .70); other preoperative visual parameters were also comparable. Incidence of 2+ grade of haze was detected in 1 (2.5%) right and 2 (5.0%) left eyes (P > .99) 3 to 6 months postoperatively. Incidence of 1+ degree of haze was also comparable. No eye developed 3+ degrees or more of haze. One year postoperatively, both eyes achieved comparable refraction, visual acuity, contrast sensitivity, and higher order aberrations, and no greater than trace haze was detected. MMC-treated eyes suffered a greater loss of endothelial cell density (P < .001) and showed higher variance in cell size (P = .001).

CONCLUSIONS

Single-step transepithelial PRK with or without MMC showed similar efficacy and incidence of haze in eyes with mild to moderate myopia with total ablation depths of 160 μm or less. However, MMC-treated eyes showed a worse profile of endothelial cell indices. Applications of MMC in this subgroup of patients may be reconsidered. [J Refract Surg. 2018;34(6):400-407.].

First results with a new intraocular lens design for the individual correction of spherical aberration

PURPOSE

To assess the feasibility of individual compensation of corneal spherical aberration with a custom intraocular lens (IOL).

SETTING

Department of Ophthalmology, Rudolf Virchow Klinikum Glauchau, Glauchau, Germany.

DESIGN

Prospective case series.

METHODS

Cataract patients were randomized to receive an individual aberration-correcting IOL (Invidua-aA; Group A) or a standard aspheric aberration-free IOL of otherwise identical design (Aspira-aA; Group B). In Group A, the IOL was designed according to preoperative calculation of the corneal spherical aberration Z(4,0). The aim was to achieve an overall postoperative ocular spherical aberration close to zero. Four weeks and 3 months postoperatively, the refraction, visual acuity (far, intermediate, and near distance), photopic and mesopic contrast sensitivities (with and without glare), defocus curve, corneal and ocular spherical aberration, and pupil size were measured.

RESULTS

Group A, 57 eyes of 42 patients and Group B, 29 eyes of 27 patients. Preoperatively, there was no difference in corneal spherical aberration between groups (P > .05). Three months postoperatively, residual ocular spherical aberration Z(4,0) was significantly lower in Group A (P < .001). Photopic and mesopic contrast sensitivities (with and without glare) were significantly higher in Group A at most spatial frequencies. Monocular defocus curve and distance, intermediate, and near visual acuity outcomes did not differ significantly between groups.

CONCLUSIONS

Implantation of a custom monofocal aspheric IOL effectively reduced overall ocular spherical aberration. Clinical outcomes indicate that IOLs with an individual spherical aberration correction improve functional vision, especially contrast sensitivity, compared with standard aberration-free IOLs.

The effect of spherical aberration on visual performance and refractive state for stimuli and tasks typical of night viewing

PURPOSE

The aim of this work was to examine the impact of Seidel spherical aberration (SA) on optimum refractive state for detecting and discriminating small bright lights on a dark background.

METHODS

An adaptive-optics system was used to correct ocular aberrations of cyclopleged eyes and then systematically introduce five levels of Seidel SA for a 7-mm diameter pupil: 0,±0.18, and±0.36diopters (D)mm-2. For each level of SA, subjects were required to detect one or resolve two points of light (0.54 arc min diameter) on a dark background. Refractive error was measured by adjusting stimulus vergence to minimize detection and resolution thresholds. Two other novel focusing tasks for single points of light required maximizing the perceived intensity of a bright point's core and minimizing its overall perceived size (i.e. minimize starburst artifacts). Except for the detection task, luminance of the point of light was 1000cdm-2 on a black background lower than 0.5cdm-2.

RESULTS

Positive SA introduced myopic shifts relative to the best subjective focus for dark letters on a bright background when there was no SA, whereas negative SA introduced hyperopic shifts in optimal focus. The changes in optimal focus were -1.7, -2.4, -2.0, and -9.2D of focus per Dmm-2 of SA for the detection task, resolution task, and maximization of core's intensity and minimization of size, respectively.

CONCLUSION

Ocular SA can be a significant contributor to changes in refractive state when viewing high-contrast point sources typically encountered in nighttime environments.

Repeatability of a Commercially Available Adaptive Optics Visual Simulator and Aberrometer in Normal and Keratoconic Eyes

PURPOSE

To evaluate the repeatability of aberration measurement obtained by a Hartmann-Shack aberrometer combined with a visual adaptive optics simulator in normal and keratoconic eyes.

METHODS

One hundred fifteen normal eyes and 92 eyes with grade I and II keratoconus, as per the Amsler-Krumeich classification, were included in the study. To evaluate the repeatability, three consecutive measurements of ocular aberrations were obtained by a single operator. Zernike analyses up to the 5th order for a pupil size of 4.5 mm were performed. Statistical analyses included the intraclass correlation coefficient (ICC) and within-subject standard deviation (SD).

RESULTS

For intrasession repeatability, the ICC value for sphere and cylinder was 0.94 and 0.93 in normal eyes and 0.98 and 0.97 in keratoconic eyes, respectively. The ICC for root mean square of higher order aberrations (HOA_RMS) was 0.82 in normal and 0.98 in keratoconic eyes. For 3rd order aberrations (trefoil and coma), the ICC values were greater than 0.87 for normal eyes and greater than 0.92 for keratoconic eyes. The ICC for spherical aberration was 0.92 and 0.90 in normal and keratoconic eyes, respectively.

CONCLUSIONS

Visual adaptive optics provided repeatable aberrometry data in both normal and keratoconic eyes. For most of the parameters, the repeatability in eyes with early keratoconus was somewhat better than that for normal eyes. The repeatability of the Zernike terms was acceptable for 3rd order (trefoil and coma) and spherical aberrations. Therefore, visual adaptive optics was a suitable tool to perform repeatable aberrometric measurements. [J Refract Surg. 2017;33(11):769-772.].

Ocular higher-order aberrations and axial eye growth in young Hong Kong children

This retrospective longitudinal analysis aimed to investigate the association between ocular higher-order aberrations (HOAs) and axial eye growth in Hong Kong children. Measures of axial length and ocular HOAs under cycloplegia were obtained annually over a two-year period from 137 subjects aged 8.8 ± 1.4 years with mean spherical equivalent refraction of -2.04 ± 2.38 D. A significant negative association was observed between the RMS of total HOAs and axial eye growth (P = 0.03), after adjusting for other significant predictors of axial length including age, sex and refractive error. Similar negative associations with axial elongation were found for the RMS of spherical aberrations ([Formula: see text] and [Formula: see text] combined) (P = 0.037). Another linear mixed model also showed that greater levels of vertical trefoil [Formula: see text], primary spherical aberration [Formula: see text] and negative oblique trefoil [Formula: see text] were associated with slower axial elongation and longer axial length (all P < 0.05). These findings support the potential role of HOAs, image quality and a vision-dependent mechanism in childhood eye growth.

Evaluation of the True Wavefront Aberrations in Eyes Implanted With a Rotationally Asymmetric Multifocal Intraocular Lens

PURPOSE

Standard evaluation of aberrations from wavefront slope measurements in patients implanted with a rotationally asymmetric multifocal intraocular lens (IOL), the Lentis Mplus (Oculentis GmbH, Berlin, Germany), results in large magnitude primary vertical coma, which is attributed to the intrinsic IOL design. The new proposed method analyzes aberrometry data, allowing disentangling the IOL power pupillary distribution from the true higher order aberrations of the eye.

METHODS

The new method of wavefront reconstruction uses retinal spots obtained at both the near and far foci. The method was tested using ray tracing optical simulations in a computer eye model virtually implanted with the Lentis Mplus IOL, with a generic cornea or with anterior segment geometry obtained from custom quantitative spectral-domain optical coherence tomography in a real patient. The method was applied to laser ray tracing aberrometry data at near and far fixation obtained in a patient implanted with the Lentis Mplus IOL.

RESULTS

Higher order aberrations evaluated from simulated and real retinal spot diagrams following the new reconstruction approach matched the nominal aberrations (approximately 98%). Previously reported primary vertical coma in patients implanted with this IOL lost significance with the application of the proposed reconstruction.

CONCLUSIONS

Custom analysis of ray tracing-based retinal spot diagrams allowed decoupling of the true higher order aberrations of the patient's eye from the power pupillary distribution of a rotationally asymmetric multifocal IOL, therefore providing the appropriate phase map to accurately evaluate through-focus optical quality. [J Refract Surg. 2017;33(4):257-265.].

Effect of a contact lens on mouse retinal in vivo imaging: Effective focal length changes and monochromatic aberrations

For in vivo mouse retinal imaging, especially with Adaptive Optics instruments, application of a contact lens is desirable, as it allows maintenance of cornea hydration and helps to prevent cataract formation during lengthy imaging sessions. However, since the refractive elements of the eye (cornea and lens) serve as the objective for most in vivo retinal imaging systems, the use of a contact lens, even with 0 Dpt. refractive power, can alter the system’s optical properties. In this investigation we examined the effective focal length change and the aberrations that arise from use of a contact lens. First, focal length changes were simulated with a Zemax mouse eye model. Then ocular aberrations with and without a 0 Dpt. contact lens were measured with a Shack-Hartmann wavefront sensor (SHWS) in a customized AO-SLO system. Total RMS wavefront errors were measured for two groups of mice (14-month, and 2.5-month-old), decomposed into 66 Zernike aberration terms, and compared. These data revealed that vertical coma and spherical aberrations were increased with use of a contact lens in our system. Based on the ocular wavefront data we evaluated the effect of the contact lens on the imaging system performance as a function of the pupil size. Both RMS error and Strehl ratios were quantified for the two groups of mice, with and without contact lenses, and for different input beam sizes. These results provide information for determining optimum pupil size for retinal imaging without adaptive optics, and raise critical issues for design of mouse optical imaging systems that incorporate contact lenses.

A Three-Year Observation of Corneal Backscatter After Small Incision Lenticule Extraction (SMILE)

PURPOSE

To investigate changes in corneal backscatter after small incision lenticule extraction (SMILE).

METHODS

One eye was randomly selected from 34 patients who underwent SMILE procedures. Corneal backscatter was analyzed using Scheimpflug technology before surgery and at postoperative 1 day, 1 week, 1 month, 3, 6, and 12 months, and 3 years. Three different corneal depths (the anterior 120 µm, the center, and the posterior 60 µm) and three concentric radial zones (0 to 2, 2 to 6, and 6 to 10 mm) were analyzed. Another 40 eyes of 40 patients who underwent femtosecond laser-assisted LASIK (FS-LASIK) were examined before surgery and at postoperative 1 day and 3 years as the control group.

RESULTS

At postoperative day 1, a significant increase in corneal backscatter was detected in the SMILE group compared to preoperative values in the central 0 to 6 mm zone of the anterior layer and the 0 to 2 mm zone of the central layer (all P < .01). This increase was higher than the increase in the FS-LASIK group in the central 0 to 6 mm zone of the anterior and central layers (all P < .01). No significant differences in corneal backscatter were detected between preoperative values and the 1-week, and 1-, 3-, 6-, and 12-month follow-up visits in the SMILE group (all P > .05). Moreover, a significant decrease in corneal backscatter was detected in the three zones of all three layers in the two groups at 3 years postoperatively compared to preoperative values (all P < .001) and no significant difference was found between the two groups (all P < .05).

CONCLUSIONS

Corneal backscatter peaks and declines to the baseline in the early period after SMILE and corneal transparency achieves an improvement within 3 years postoperatively. [J Refract Surg. 2017;33(6):377-382.].

A Prospective Study to Compare Visual Outcomes Between Wavefront-optimized and Topography-guided Ablation Profiles in Contralateral Eyes With Myopia

PURPOSE

To analyze refractive outcomes of wavefront-optimized (WFO) ablation and topography-guided custom ablation (TCAT) profiles using the Allegretto Wave excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX) in the treatment of myopia.

METHODS

Sixty eyes of 30 patients who underwent LASIK were included in this prospective interventional study. WFO ablation was performed in one eye (WFO group) and TCAT in the fellow eye (TCAT group). The WaveLight FS200 femtosecond laser (Alcon Laboratories, Inc.) was used to create the flap and Allegretto Wave excimer laser (Alcon Laboratories, Inc.) was used for photoablation. The Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Allegretto Topolyzer (Alcon Laboratories, Inc.) were used to measure the corneal aberrations. Refractive visual outcomes were also compared.

RESULTS

Accuracy, safety, and efficacy were similar in the two groups. The total root mean square (RMS) and RMS of lower order aberrations were significantly better in eyes that underwent TCAT (P < .05). There was a decrease in individual higher order aberrations in the TCAT group, with a statistically significant difference in the spherical aberrations (P = .02). The corneal asphericity (Q value) was not significantly different between the WFO (0.6 ± 0.1) and TCAT (0.51 ± 0.09) groups. The postoperative total RMS of higher order aberrations was lower in the TCAT group, but this was not statistically significant (P > .05). There was a more positive change in Q value and spherical aberrations in the WFO group, but this was not statistically significant.

CONCLUSIONS

TCAT and WFO ablation provided essentially equivalent outcomes after myopic LASIK, with induction of fewer lower order aberrations and higher order aberrations following TCAT ablation. [J Refract Surg. 2017;33(1):6-10.].

Changes to Corneal Aberrations and Vision After Monovision in Patients With Hyperopia After Using a Customized Aspheric Ablation Profile to Increase Corneal Asphericity (Q-factor)

PURPOSE

To evaluate the visual outcomes and fourth-order Zernike spherical aberrations induced with a customized change in corneal asphericity (ΔQ) correction of presbyopia combined with monovision for hyperopic patients.

METHODS

Consecutive hyperopic patients who underwent presbyopic LASIK between September 2013 and July 2014 were included. For the non-dominant eyes, the aspheric ablation profile associated with a myopic refraction was planned using the Custom-Q nomogram (Alcon Laboratories, Inc., Fort Worth, TX). Uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), spherical equivalent refraction, ΔQ, and change in corneal spherical aberration coefficient (ΔC₄⁰) were analyzed. Postoperative data were collected at 1, 3, and 6 months.

RESULTS

Sixty-five patients were included. The mean age was 56.5 ± 5.7 years (range: 47 to 70 years). At the 6-month follow-up, the spherical equivalent refraction for non-dominant and dominant eyes was -1.07 ± 0.74 and 0.32 ± 0.55 diopters (D), respectively. The mean binocular UDVA was 0.01 ± 0.04 logMAR (range: -0.12 to 0.30 logMAR); 91% of patients achieved 20/20 or better binocular UDVA and 83% of patients had Jaeger 3 (Parinaud 4) or better binocular UNVA. The ΔQ for non-dominant and dominant eyes was -0.61 ± 0.15 and -0.33 ± 0.25, respectively, for a 6-mm pupil diameter and was significantly higher for non-dominant eyes (P < .0001). The achieved ΔC₄⁰ was -0.49 ± 0.23 µm for non-dominant eyes (for a theoretical ideal value of -0.40 µm) and -0.30 ± 0.18 µm for dominant eyes. For non-dominant eyes, the attempted ΔQ (-0.60) was close to the achieved value (-0.61 ± 0.15).

CONCLUSIONS

For hyperopic patients, combining the customized corneal aspheric ablation profile with monovision is safe, effective, and reproducible, inducing intended changes in corneal spherical aberrations. [J Refract Surg. 2016;32(11):734-741.].

Small-Aperture Intraocular Lens Implantation in a Patient With an Irregular Cornea

PURPOSE

To report a small-aperture intraocular lens (IOL) implantation after corneal trauma.

METHODS

Case report.

RESULTS

A 17-year-old boy with corneal scars, iris defect, and aphakia after perforating trauma in the right eye was scheduled for small-aperture IOL (IC-8; AcuFocus, Irvine, CA) implantation under general anesthesia. No intraoperative complications were observed. Six months after surgery, the uncorrected distance and near visual acuity increased significantly. Furthermore, reduced photopic phenomena were reported.

CONCLUSIONS

The small-aperture IOL is a new and promising option to treat patients suffering from the effects of corneal irregularities. [J Refract Surg. 2016;32(10):706-708.].

Interaction of aberrations, diffraction, and quantal fluctuations determine the impact of pupil size on visual quality

Our purpose is to develop a computational approach that jointly assesses the impact of stimulus luminance and pupil size on visual quality. We compared traditional optical measures of image quality and those that incorporate the impact of retinal illuminance dependent neural contrast sensitivity. Visually weighted image quality was calculated for a presbyopic model eye with representative levels of chromatic and monochromatic aberrations as pupil diameter was varied from 7 to 1 mm, stimulus luminance varied from 2000 to 0.1  cd/m², and defocus varied from 0 to -2 diopters. The model included the effects of quantal fluctuations on neural contrast sensitivity. We tested the model's predictions for five cycles per degree gratings by measuring contrast sensitivity at 5  cyc/deg. Unlike the traditional Strehl ratio and the visually weighted area under the modulation transfer function, the visual Strehl ratio derived from the optical transfer function was able to capture the combined impact of optics and quantal noise on visual quality. In a well-focused eye, provided retinal illuminance is held constant as pupil size varies, visual image quality scales approximately as the square root of illuminance because of quantum fluctuations, but optimum pupil size is essentially independent of retinal illuminance and quantum fluctuations. Conversely, when stimulus luminance is held constant (and therefore illuminance varies with pupil size), optimum pupil size increases as luminance decreases, thereby compensating partially for increased quantum fluctuations. However, in the presence of -1 and -2 diopters of defocus and at high photopic levels where Weber's law operates, optical aberrations and diffraction dominate image quality and pupil optimization. Similar behavior was observed in human observers viewing sinusoidal gratings. Optimum pupil size increases as stimulus luminance drops for the well-focused eye, and the benefits of small pupils for improving defocused image quality remain throughout the photopic and mesopic ranges. However, restricting pupils to <2  mm will cause significant reductions in the best focus vision at low photopic and mesopic luminances.

Corneal-Wavefront guided transepithelial photorefractive keratectomy after corneal collagen cross linking in keratoconus

PURPOSE

To evaluate the efficacy and safety of Corneal-Wavefront guided transepithelial photorefractive keratectomy (TransPRK) after corneal collagen cross linking (CXL) in keratoconic patients.

METHODS

In this retrospective, non-comparative, consecutive case series, 39 keratoconic eyes underwent Corneal-Wavefront guided TransPRK for the correction of aberrations at least 4 months after conventional CXL at SEKAL Rovigo Microsurgery Centre, Rovigo, Italy. Two eyes (5%) underwent a secondary laser retreatment for the improvement of post-operative visual acuity and were not included in this retrospective analysis. The mean age of the patients was 35±12 years (19-64 years) at the time of the surgery. Keratron-Scout (Optikon) topographer was used for diagnostic tests and a flying-spot laser (AMARIS; SCHWIND eye-tech-solutions) was used for the refractive surgery. Complete ophthalmic examinations were performed before and after the surgery (4-36 months postoperatively with a mean follow up time of 10±8 months).

RESULTS

Preoperatively, eyes showed irregular astigmatism up to 8D. At last postoperative follow-up, 21 eyes (57%) had UDVA better than 20/40, and six eyes (16%) had UDVA of 20/20. Twenty-three eyes (62%) were within 1.50D of attempted correction in spherical equivalent (mean deviation from target was +1.09±2.36D, range -2.50 to +7.38D). No eye lost 2 Snellen lines of CDVA, and 15 eyes (41%) had an increase of more than 2 lines.

CONCLUSIONS

Corneal-Wavefront guided transepithelial PRK ablation profiles after conventional CXL yields to good visual, optical, and refractive results. These treatments are safe and efficacious for the correction of refracto-therapeutic problems in keratoconic patients.

Effect of Limbal Relaxing Incisions on Corneal Aberrations

PURPOSE

To study the effect of limbal relaxing incisions on corneal aberrations after phacoemulsification with aspheric intraocular lens (IOL) implantation.

METHODS

Forty-five eyes underwent microincision cataract surgery with on-axis phacoemulsification incision. These eyes were divided into two groups: limbal relaxing incision group (23 eyes) and control group (22 eyes). In the limbal relaxing incision group, a single limbal relaxing incision was performed on the steepest meridian of corneal topography and the degrees of arc were determined using the DONO-Donnenfeld nomogram. The eyes in the control group were operated on by microincision cataract surgery without limbal relaxing incision. Corneal topography and wavefront analysis over 6-mm pupil size were performed preoperatively and 1 month postoperatively in both groups. Target induced astigmatism vector, surgically induced astigmatism vector, difference vector, magnitude of error, flattening effect, and torque were analyzed using the Alpins vectorial method.

RESULTS

The limbal relaxing incision group showed significant reduction in topographic astigmatism by 51.87% of preoperative topographical astigmatism (P < .0001). The mean surgically induced astigmatism of limbal relaxing incision was 1.29 ± 0.71 diopters (D), which was close to the mean target induced astigmatism (1.33 ± 0.20 D), whereas the control group did not show a significant change in topographic astigmatism (0.17 ± 0.11 D; P = .73). Higher order aberrations of the cornea did not show significant change in either group except quatrefoil aberration, which significantly increased in the limbal relaxing incision group but not in the control group, with no significant difference between the two groups regarding corneal aberrations.

CONCLUSIONS

Limbal relaxing incision is an effective method in reducing corneal astigmatism with neutral effect on corneal aberrations.

Comparison of Visual Quality After SMILE and LASEK for Mild to Moderate Myopia

PURPOSE

To compare the objective and subjective quality of vision after femtosecond laser-assisted small incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for mild to moderate myopia.

METHODS

This prospective, comparative study included 65 eyes of 33 patients in the SMILE group, with a mean spherical equivalent (SE) of -4.16 ± 0.82 diopters, and 50 eyes of 25 patients in the LASEK group, with a mean SE of -3.81 ± 0.97 diopters. Visual acuity, corneal topography, contrast sensitivity, and wavefront aberrations were recorded preoperatively and compared with postoperative measurements. A quality of vision questionnaire was scored and analyzed 3 months postoperatively.

RESULTS

Three months postoperatively, the SMILE group had fewer (P < .05) higher-order aberrations (HOAs) (0.390 ± 0.175 µm), including spherical aberration (SA) (0.262 ± 0.242 µm), than the LASEK group (HOAs = 0.479 ± 0.148 µm, SA = 0.576 ± 0.287 µm, trefoil = 0.465 ± 0.248 µm). There was no significant difference in the amount of coma and trefoil between the two groups after surgery. Analysis of the scores of glare and halos in the quality of vision questionnaire revealed that SMILE (night glare = 1.25 ± 1.22, halos = 0.97 ± 1.12) provided a better quality of vision (P < .05) than LASEK (night glare = 2.32 ± 1.99, halos = 1.96 ± 1.77). The two groups demonstrated no significant difference in contrast sensitivity 3 months postoperatively. No vision-threatening complications were noted at any stage in either group.

CONCLUSIONS

Both SMILE and LASEK are safe and effective surgical procedures in the correction of myopia. SMILE has a lower induction rate of HOAs and a higher degree of patient satisfaction than LASEK at 3 months postoperatively.

Control of Induced Spherical Aberration in Moderate Hyperopic LASIK by Customizing Corneal Asphericity

PURPOSE

To compare differences in induced aberrations and visual acuity after wavefront-optimized LASIK and aspheric-customized LASIK for the treatment of hyperopia.

METHODS

Forty consecutive eyes underwent uneventful LASIK for treatment of moderate hyperopia (+3.82 ± 0.63 diopters [D] [+2.75; +5.125]). A standard procedure was performed in the wavefront-optimized LASIK group (n = 24), whereas a postoperative Q-factor equal to zero was scheduled in the aspheric-customized LASIK group (n = 16).

RESULTS

At 6 months, mean spherical aberration for a 6-mm pupil diameter was -0.39 ± 0.23 µm (range: -0.76 to 0.01 µm) and Q-factor was -0.52 ± 0.22 (range: -1.00 to -0.12 µm) in the wavefront-optimized group and 0.04 ± 0.18 µm (range: -0.34 to 0.29 µm) and -0.04 ± 0.25 (range: -0.64 to 0.40 µm) in the aspheric-customized LASIK group (P ≤ .05). All remaining outcomes showed no significant differences between groups. UDVA was 20/18.69 ± 0.15 (range: 0.80 to 1.20) in the wavefront-optimized LASIK group and 20/20 ± 0.17 (range: 0.50 to 1.20) in the aspheric-customized LASIK group. One patient in the wavefront-optimized LASIK group lost two or more lines of CDVA and no lines were lost in the aspheric-customized LASIK group.

CONCLUSIONS

The results in this small cases series suggest that using an aspheric-customized ablation profile with a target Q-factor equal to 0 in moderate hyperopic LASIK is statistically compatible with a diminishing induced spherical aberration without altering procedural safety when the WaveLight Allegretto 400-Hz excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX) is used.

A Comparative Study of Higher order Aberrations between Pterygium and Non-Pterygium Eyes

BACKGROUND

Pterygium may induce pressure and distortion on the corneal surface leading to ocular aberrations.

OBJECTIVE

To evaluate higher order aberrations in pterygium eyes.

MATERIAL AND METHOD

Thirty-two patients with unilateral primary pterygium were enrolled. Wavefront analysis technique was used to determine the higher order aberrations in pterygium eyes and normal fellow eyes in individuals. Higher order aberration values were compared between both eyes with paired t-test. Pearson correlation was used to assess the correlations of higher order aberration values with pterygium size.

RESULTS

Of the 32 patients, there were 15 males (47%) and 17 females (53%), mean age was 48.9±12.2 years. The average horizontal size of pterygium was 2.6+0.9 millimeters. For pterygium eyes, the mean of coma, trefoil, spherical aberration, and quadrafoil were 0.87±1.01, 1.45±1.55, 0.28±0.27, and 0.79±0.94 micrometers, respectively. And those of normal fellow eyes were 0.46±0.37, 0.80±0.71, 0.15±0.33, and 0.39±0.47 micrometers, respectively. Comparing between pterygium and contralateral normal eyes, a significant difference was present in all parameters (paired t-test, p<0.05). Coma, trefoil, and quadrafoil of pterygium eyes had a significant relationship with pterygium size (Pearson correlation, p<0.05) except for spherical aberration.

CONCLUSION

The findings suggest that higher order aberrations have a tendency to increase in pterygium eyes compared to contralateral normal eyes, and most have a correlation with pterygium size.

Visual Outcomes and Optical Quality After Femtosecond Laser Small Incision Lenticule Extraction: An 18-Month Prospective Study

PURPOSE

To investigate the long-term visual outcomes and optical quality after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction.

METHODS

Fifty-four patients (37 women, 17 men) who underwent SMILE were enrolled in this prospective clinical study. Patient ages ranged from 18 to 40 years, with a mean spherical equivalent of -6.50 ± 1.64 diopters. Data including refractive parameters, retinal image quality, intraocular scattering, and aberrations were collected at 6 and 18 months after surgery. Patient satisfaction was also evaluated.

RESULTS

At 18 months after surgery, both the mean safety index and the efficacy index were 1.23 ± 0.23 (range: 0.80 to 1.50); there was no significant difference with indices measured at 6 months (P > .05). No patient lost two or more lines of corrected distance visual acuity. Total higher-order aberrations (HOAs) and coma significantly increased after SMILE (P < .05), whereas total spherical aberrations and trefoil changed only slightly. The mean modulation transfer function cutoff frequency was 36.66 ± 8.54 cycles per degree (cpd) before surgery and 37.81 ± 6.89 cpd at 18 months postoperatively; the mean objective scatter index was 0.62 ± 0.33 before surgery and 0.71 ± 0.38 at 18 months postoperatively. No significant difference was found between the three time points (P > .05). Mean patient satisfaction was 9.31 ± 0.64 (with a maximum score of 10).

CONCLUSIONS

SMILE showed good safety, efficacy, and stability in correcting moderate to high myopia, and patients were highly satisfied. HOAs increased after SMILE, mainly due to the increase of coma, whereas retinal image quality and intraocular scattering barely changed.

Femtosecond Laser-assisted Wavefront-guided LASIK Using a Newer Generation Aberrometer: 1-Year Results

PURPOSE

To evaluate long-term outcomes of wavefront-guided LASIK with a new advanced aberrometer.

METHODS

Fifty eyes of 25 LASIK candidates with myopia and/or astigmatism underwent aberrometry (iDesign Advanced WaveScan; Abbott Medical Optics, Santa Ana, CA), femtosecond laser-assisted flap creation, and excimer ablation. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SEQ), and astigmatism outcomes were measured at 1, 3, 6, and 12 months postoperatively.

RESULTS

The sphere, cylinder, and SEQ were -4.29 ± 1.94, -0.75 ± 0.76, and -4.67 ± 2.01 diopters (D), respectively, preoperatively and 0.03 ± 0.13, -0.09 ± 0.13, and -0.02 ± 0.14 D, respectively, 12 months postoperatively (P < .001). The postoperative log-MAR CDVA (-0.07 ± 0.09) and UDVA (-0.04 ± 0.09) were better than the preoperative logMAR CDVA (0.07 ± 0.10) (P < .01). Ninety-four percent achieved a 12-month logMAR UDVA of 0.0 or less (20/20 or better Snellen) and 100% achieved 0.3 or less (20/40 or better Snellen), compared to a preoperative logMAR CDVA of 0.0 or worse in 54% and 0.3 or less in 100%. Postoperative SEQ was within ±0.50 D in 98%. The regression plot for achieved (y) vs intended (x) correction at 12 months was (y = 0.98 × - 0.09, R(2) = 0.99, P < .001). No cases lost CDVA. The target and 12-month surgically induced astigmatisms (TIA and SIA) were 0.91 ± 0.75 and 0.82 ± 0.70, respectively. The regression plot between them was SIA = 0.91 × TIA - 0.01 (R(2) = 0.95, P < .001). The angle of error was -0.29° ± 12.6° and index of success was 0.13 ± 0.25. There was only a mild, nonsignificant increase of higher-order aberrations after surgery, and the postoperative wavefront was stable on follow-up.

CONCLUSIONS

Wavefront-guided LASIK with iDesign aberrometry appears to be safe and effective in this long-term, consecutive case series.

Corneal Transplantation in Disease Affecting Only One Eye: Does It Make a Difference to Habitual Binocular Viewing?

BACKGROUND

Clarity of the transplanted tissue and restoration of visual acuity are the two primary metrics for evaluating the success of corneal transplantation. Participation of the transplanted eye in habitual binocular viewing is seldom evaluated post-operatively. In unilateral corneal disease, the transplanted eye may remain functionally inactive during binocular viewing due to its suboptimal visual acuity and poor image quality, vis-à-vis the healthy fellow eye.

METHODS AND FINDINGS

This study prospectively quantified the contribution of the transplanted eye towards habitual binocular viewing in 25 cases with unilateral transplants [40 yrs (IQR: 32-42 yrs) and 25 age-matched controls [30 yrs (25-37 yrs)]. Binocular functions including visual field extent, high-contrast logMAR acuity, suppression threshold and stereoacuity were assessed using standard psychophysical paradigms. Optical quality of all eyes was determined from wavefront aberrometry measurements. Binocular visual field expanded by a median 21% (IQR: 18-29%) compared to the monocular field of cases and controls (p = 0.63). Binocular logMAR acuity [0.0 (0.0-0.0)] almost always followed the fellow eye's acuity [0.00 (0.00 --0.02)] (r = 0.82), independent of the transplanted eye's acuity [0.34 (0.2-0.5)] (r = 0.04). Suppression threshold and stereoacuity were poorer in cases [30.1% (13.5-44.3%); 620.8 arc sec (370.3-988.2 arc sec)] than in controls [79% (63.5-100%); 16.3 arc sec (10.6-25.5 arc sec)] (p<0.001). Higher-order wavefront aberrations of the transplanted eye [0.34 μ (0.21-0.51 μ)] were higher than the fellow eye [0.07 μ (0.05-0.11 μ)] (p<0.001) and their reduction with RGP contact lenses [0.09 μ (0.08-0.12 μ)] significantly improved the suppression threshold [65% (50-72%)] and stereoacuity [56.6 arc sec (47.7-181.6 arc sec)] (p<0.001).

CONCLUSIONS

In unilateral corneal disease, the transplanted eye does participate in gross binocular viewing but offers limited support to fine levels of binocularity. Improvement in the transplanted eye's optics enhances its participation in binocular viewing. Current metrics of this treatment success can expand to include measures of binocularity to assess the functional benefit of the transplantation process in unilateral corneal disease.

Image Quality Analysis of Eyes Undergoing LASER Refractive Surgery

Laser refractive surgery for myopia increases the eye’s higher-order wavefront aberrations (HOA’s). However, little is known about the impact of such optical degradation on post-operative image quality (IQ) of these eyes. This study determined the relation between HOA’s and IQ parameters (peak IQ, dioptric focus that maximized IQ and depth of focus) derived from psychophysical (logMAR acuity) and computational (logVSOTF) through-focus curves in 45 subjects (18 to 31yrs) before and 1-month after refractive surgery and in 40 age-matched emmetropic controls. Computationally derived peak IQ and its best focus were negatively correlated with the RMS deviation of all HOA’s (HORMS) (r≥-0.5; p<0.001 for all). Computational depth of focus was positively correlated with HORMS (r≥0.55; p<0.001 for all) and negatively correlated with peak IQ (r≥-0.8; p<0.001 for all). All IQ parameters related to logMAR acuity were poorly correlated with HORMS (r≤|0.16|; p>0.16 for all). Increase in HOA’s after refractive surgery is therefore associated with a decline in peak IQ and a persistence of this sub-standard IQ over a larger dioptric range, vis-à-vis, before surgery and in age-matched controls. This optical deterioration however does not appear to significantly alter psychophysical IQ, suggesting minimal impact of refractive surgery on the subject’s ability to resolve spatial details and their tolerance to blur.

Refractive Outcomes, Contrast Sensitivity, HOAs, and Patient Satisfaction in Moderate Myopia: Wavefront-Optimized Versus Tissue-Saving PRK

PURPOSE

To compare refractive outcomes, contrast sensitivity, higher-order aberrations (HOAs), and patient satisfaction after photorefractive keratectomy for correction of moderate myopia with two methods: tissue saving versus wavefront optimized.

METHODS

In this prospective, comparative study, 152 eyes (80 patients) with moderate myopia with and without astigmatism were randomly divided into two groups: the tissue-saving group (Technolas 217z Zyoptix laser; Bausch & Lomb, Rochester, NY) (76 eyes of 39 patients) or the wavefront-optimized group (WaveLight Allegretto Wave Eye-Q laser; Alcon Laboratories, Inc., Fort Worth, TX) (76 eyes of 41 patients). Preoperative and 3-month postoperative refractive outcomes, contrast sensitivity, HOAs, and patient satisfaction were compared between the two groups.

RESULTS

The mean spherical equivalent was -4.50 ± 1.02 diopters. No statistically significant differences were detected between the groups in terms of uncorrected and corrected distance visual acuity and spherical equivalent preoperatively and 3 months postoperatively. No statistically significant differences were seen in the amount of preoperative to postoperative contrast sensitivity changes between the two groups in photopic and mesopic conditions. HOAs and Q factor increased in both groups postoperatively (P = .001), with the tissue-saving method causing more increases in HOAs (P = .007) and Q factor (P = .039). Patient satisfaction was comparable between both groups.

CONCLUSIONS

Both platforms were effective in correcting moderate myopia with or without astigmatism. No difference in refractive outcome, contrast sensitivity changes, and patient satisfaction between the groups was observed. Postoperatively, the tissue-saving method caused a higher increase in HOAs and Q factor compared to the wavefront-optimized method, which could be due to larger optical zone sizes in the tissue-saving group.

Hydrogel Inlay for Presbyopia: Objective and Subjective Visual Outcomes

PURPOSE

To evaluate changes in visual performance and ocular optical quality after implantation of a corneal hydrogel inlay as a treatment for presbyopia.

METHODS

A Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, CA) was implanted monocularly on the stromal bed of a femtosecond laser-assisted generated corneal flap of non-dominant eyes of 22 patients with emmetropic presbyopia (preoperative spherical equivalent range: -0.50 to 1.00 diopters). Efficacy was determined by measuring near and distance visual acuities and ocular aberrations, and satisfaction was assessed by a patient questionnaire.

RESULTS

The preoperative monocular uncorrected near visual acuity of the inlay inserted eye was 20/129 ± 1 Snellen (range: 20/135 to 20/61 Snellen) and improved to 20/35 ± 2 Snellen (range: 20/61 to 20/20 Snellen) (P < .01) at 6 months postoperatively. The monocular uncorrected distance visual acuity of the eye receiving the inlay was 20/25 ± 2 Snellen (range: 20/50 to 20/20 Snellen) preoperatively and 20/25 ± 1 Snellen (range: 20/50 to 20/20 Snellen) at 6 months postoperatively (P =.257). According to the questionnaire responses, 82% of patients were satisfied. This was despite near glasses needs remaining in 13.6% of the cohort and the presence of glare and a decrease in night vision in approximately 40% of patients. The primary spherical aberration coefficient Z4(0) changed from positive to negative values in all patients (P < .01). However, the point spread function showed no significant change.

CONCLUSIONS

Hydrogel corneal inlays improve uncorrected near visual acuity in patients with presbyopia with only moderate effect on visual quality. However, the satisfaction with this therapy was relatively lower in these Korean patients than that reported previously in Western patients.

Clinical Outcomes and Capsular Bag Stability of a Four-Point Haptic Bitoric Intraocular Lens

PURPOSE

To evaluate the visual, refractive, and aberrometric outcomes of a bitoric intraocular lens (IOL) and its stability and alignment within the capsular bag.

METHODS

A retrospective study including 41 eyes of 24 patients with preexisting corneal astigmatism of 0.75 diopters or greater undergoing cataract surgery with implantation of the bitoric IOL AT TORBI 709M (Carl Zeiss Meditec, Jena, Germany). Visual and refractive outcomes were evaluated during a 3-month follow-up period. The misalignment between intended and real axis and the levels of corneal, internal, and ocular aberrations (KR-1W; Topcon, Tokyo, Japan) were also evaluated.

RESULTS

A total of 76% and 97% of eyes had a postoperative spherical equivalent within ± 0.50 and ± 1.00 diopters of emmetropia, respectively. Likewise, a total of 86% and 95% of eyes had a postoperative absolute value of refractive cylinder of 0.50 or less and 1.00 or less diopters, respectively. Mean postoperative corrected distance visual acuity was 0.00 logMAR (20/20 Snellen). Mean values of postoperative monocular and binocular uncorrected distance visual acuity were 0.10 and 0.00 logMAR (20/25 and 20/20 Snellen), respectively. The aberrometric analysis confirmed that the magnitude of ocular higher-order aberrations was mainly due to corneal optics and that the corneal astigmatism correction was sufficient with the toric IOL. Mean absolute IOL misalignment was 3.5° with values ranging from 0° to 10°.

CONCLUSIONS

The bitoric IOL AT TORBI 709M is able to provide a predictable correction of corneal astigmatism with low postoperative levels of ocular higher-order aberrations.

The Optical Performance of Spherical and Aspheric Intraocular Lenses in Pediatric Eyes: A Comparative Study

PURPOSE

To compare the optical performance of aspheric intraocular lenses (IOLs) designed to correct the corneal spherical aberration versus spherical IOLs in pediatric eyes after cataract surgery.

METHODS

In this prospective study, 40 eyes of patients 6 to 16 years old with developmental cataract were randomly assigned to receive a spherical IOL or an aspheric IOL after pediatric cataract surgery. At 3 months postoperatively, the outcomes compared between the two groups were best-corrected visual acuity, contrast sensitivity, and wavefront aberrometry.

RESULTS

The mean best-corrected visual acuity was 0.32 ± 0.19 logMAR in the spherical IOL group and 0.28 ± 0.16 logMAR in the aspheric IOL group (P = .179). The aspheric IOL group showed better contrast sensitivity at 1.5, 3, and 6 cycles per degree than the spherical IOL group (P < .05). Total ocular aberrations, higher-order aberrations, and spherical aberrations were significantly lower in the aspheric IOL group (P < .05).

CONCLUSIONS

The results suggest that aspheric IOLs compensate for the spherical aberration of pediatric eyes. In comparison to spherical IOLs, eyes with aspheric IOLs had decreased ocular aberrations, particularly spherical aberration, which contributed to better contrast sensitivity in these eyes. Further studies are required to evaluate the role of aspheric IOLs in children.

Effect of Intraocular Forward Scattering and Corneal Higher-Order Aberrations on Visual Acuity after Descemet's Stripping Automated Endothelial Keratoplasty

Purpose

To assess the relationship of intraocular forward scattering and corneal higher-order aberrations (HOAs) with best spectacle corrected visual acuity (BSCVA) after Descemet’s stripping automated endothelial keratoplasty (DSAEK), and to compare these parameters between DSAEK and non-Descemet’s stripping automated endothelial keratoplasty (n-DSAEK) groups.

Methods

This retrospective study enrolled thirty eyes of 30 consecutive patients who underwent standard DSAEK, and who underwent successful phacoemulsification with intraocular lens implantation before DSAEK. The mean age at the time of surgery was 71.7 ± 10.4 years. We quantitatively evaluated the objective scattering index (OSI) using the double-pass instrument (OQAS II, Visiometrics) and corneal HOAs using Hartmann-Shack aberrometry (KR-9000PW, Topcon) 3 months postoperatively.

Results

The mean OSI, corneal HOAs, and logMAR BSCVA 3 months after DSAEK were 7.91 ± 3.58, 0.43 ± 0.27 μm, and 0.32 ± 0.25, respectively. We found a significant correlation between the OSI and logMAR BSCVA (Spearman correlation coefficient r=0.714, p<0.001), but no significant association between corneal HOAs and logMAR BSCVA 3 months postoperatively (r=0.209, p=0.267). We found no significant differences in any postoperative parameters between the DSAEK and n-DSAEK groups (p>0.05).

Conclusions

Our pilot study demonstrated that the postoperative corrected visual acuity was significantly correlated with intraocular forward scattering, but not with corneal HOAs in post-DSAEK eyes, suggesting that intraocular forward scattering plays a more essential role in postoperative visual performance than corneal aberrations after DSAEK. The detailed visual performance, such as HOAs and intraocular scattering, after n-DSAEK appears to be essentially equivalent to that after DSAEK.

Corneal High-Order Aberrations and Backscatter in Fuchs' Endothelial Corneal Dystrophy

PURPOSE

Suboptimal visual acuity after endothelial keratoplasty has been attributed to increased anterior corneal high-order aberrations (HOAs). In this study, we determined anterior and posterior corneal HOAs over a range of severity of Fuchs' endothelial corneal dystrophy (FECD).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 108 eyes (62 subjects) with a range of severity of FECD and 71 normal eyes (38 subjects).

METHODS

All corneas were examined by using slit-lamp biomicroscopy to determine the severity of FECD versus normality. Fuchs' endothelial corneal dystrophy corneas were categorized as mild, moderate, or advanced according to the area and confluence of guttae and the presence of clinically visible edema. Normal corneas were devoid of any guttae. Wavefront errors from the anterior and posterior corneal surfaces were derived from Scheimpflug images and expressed as Zernike polynomials through the sixth order over a 6-mm diameter optical zone. Backscatter from the anterior 120 μm and posterior 60 μm of the cornea also was measured from Scheimpflug images and was standardized to a fixed scatter source. Variables were compared between FECD and control eyes by using generalized estimating equation models to adjust for age and correlation between fellow eyes.

MAIN OUTCOME MEASURES

High-order aberrations, expressed as root mean square of wavefront errors, and backscatter of the anterior and posterior cornea.

RESULTS

Total anterior corneal HOAs were increased in moderate (0.61±0.27 μm, mean ± standard deviation; P = 0.01) and advanced (0.66±0.28 μm; P = 0.01) FECD compared with controls (0.47±0.16 μm). Total posterior corneal HOAs were increased in mild (0.22±0.09 μm; P = 0.017), moderate (0.22±0.08 μm; P < 0.001), and advanced (0.23±0.09 μm; P < 0.001) FECD compared with controls (0.16±0.03 μm). Anterior and posterior corneal backscatter were higher for all severities of FECD compared with controls (P ≤ 0.02, anterior; P ≤ 0.001, posterior).

CONCLUSIONS

Anterior and posterior corneal HOAs and backscatter are higher than normal even in early stages of FECD. The early onset of HOAs in FECD might contribute to the persistence of HOAs and incomplete visual rehabilitation after endothelial keratoplasty.