Evaluation of crystalline lens and intraocular lens tilt using a swept-source optical coherence tomography biometer

Change in refractive errors with changes in IOL parameters

This study considered two questions associated with intraocular lens (IOL) power and refraction: (1) Given a refraction with a particular IOL in the eye, what will be the refraction for the IOL or another IOL if located differently with regard to tilt or anterior-posterior position? (2) For a target refraction, what is the power of another IOL if located differently with regard to tilt or position? A thin lens technique was developed to address these questions. For the first question, light was traced through the initial correcting spectacle lens to the cornea, refracted at the cornea, transferred to the position of the initial IOL, refracted at this IOL, transferred to the position of a new IOL (which may be the same IOL but with a different position and/or tilt), refracted backwards through the new IOL, transferred to the cornea and refracted out of the eye to give a new correcting spectacle lens power. For the second question, light was traced through the initial correcting spectacle lens to the cornea, refracted at the cornea, transferred to the position of the initial IOL, refracted at the initial IOL and transferred to the position of a new IOL. Light was also traced through the second correcting spectacle lens, refracted at the cornea and transferred to the position of the second IOL. The difference between the reduced image vergence for the first raytrace and the reduced object vergence for the second raytrace gave the effective power of the second IOL, and from this, the power of the second IOL was determined. Examples are presented for different situations, including a case report.

Effect of decentration and tilt on the in vitro optical quality of monofocal and trifocal intraocular lenses

PURPOSE

To evaluate and compare the effect of decentration and tilt on the optical quality of monofocal and trifocal intraocular lenses (IOL).

METHODS

Optical quality of a monofocal IOL (AcrySof IQ SN60WF; Alcon Laboratories, Inc., USA) and a trifocal IOL (AcrySof IQ PanOptix; Alcon Laboratories, Inc., USA) was assessed using an in vitro optical bench (OptiSpheric IOL R&D; Trioptics GmbH, Germany). At apertures of 3.0 mm and 4.5 mm, modulation transfer function (MTF) at spatial frequency of 50 lp/mm, MTF curve and the United States Air Force (USAF) resolution test chart of the two IOLs were measured and compared at their focus with different degrees of decentration and tilt. Optical quality at infinity, 60 cm and 40 cm and the through-focus MTF curves were compared when the two IOLs were centered at apertures of 3.0 mm and 4.5 mm. Spectral transmittance of the two IOLs was measured by the UV-visible spectrophotometer (UV 3300 PC; MAPADA, China).

RESULTS

The SN60WF and the PanOptix filtered blue light from 400 to 500 nm. Both IOLs at the far focus and the PanOptix at the intermediate focus showed a decrease in optical quality with increasing decentration and tilt. The PanOptix demonstrated enhanced optical quality compared to the previous gradient at the near focus at a decentration range of 0.3-0.7 mm with a 3.0 mm aperture, and 0.5 mm with a 4.5 mm aperture, whereas other conditions exhibited diminished optical quality with increasing decentration and tilt at the focus of both IOLs. When the two IOLs were centered, the SN60WF had better optical quality at infinity, while the PanOptix had better optical quality at 60 cm and 40 cm defocus. The optical quality of the SN60WF exceeded that of the PanOptix at far focus, with a 3 mm aperture decentration up to 0.7 mm and a 4.5 mm aperture decentration up to 0.3 mm; this observation held true for all tilts, irrespective of aperture size. As both decentration and tilt increased, the optical quality of the SN60WF deteriorated more rapidly than that of the PanOptix at the far focal point.

CONCLUSIONS

The SN60WF showed a decrease in optical quality with increasing decentration and tilt. Optical quality of the PanOptix at the near focus increased in some decentration conditions and decreased in some conditions, while it showed a decrease at the other focuses with increasing decentration. While tilt only had a negative effect on optical quality. When both IOLs were centered, the PanOptix provided a wider range of vision, while the SN60WF provided better far distance vision. At the far focus, the SN60WF has better resistance to tilt than the PanOptix, but the optical quality degrades more quickly when decentered and tilted.

Comparison of intraocular lens tilt after capsular sutured scleral fixation with capsular segments versus uneventful cataract surgery

PURPOSE

To evaluate and compare intraocular lens (IOL) tilt between uneventful phacoemulsification with in-the-bag IOL implantation and sutured scleral fixation (SSF) of the lens bag with a capsular tension segment (type 6 D / Morcher) using a Sheimpflug camera.

SETTING

Clinical Practice, Hospital. Barcelona and A Coruña, Spain.

DESIGN

Retrospective, comparative multicenter study.

METHODS

IOL tilt was compared between patients who underwent sutured scleral fixation with a capsular tension segment in a single eye (SSF group, n = 15) with patients who underwent uneventful IOL implantation (control group, n = 12) that were matched by biometric measurements. Post-operative refractive accuracy of biometric formulas by means of mean absolute error (MAE) was also reported. All patients underwent a general ophthalmic evaluation, anterior segment photography, and postoperative optical biometry (Zeiss IOLMaster® 500). In addition, IOL tilt was measured with a Scheimpflug camera (Pentacam R, Oculus Optikgerate Gmbh).

RESULTS

Mean vertical tilt was similar in both groups (2.20+/-2.47° SSF vs 1.97 +/- 1.79° control; p = 0.836) but mean horizontal tilt tended to higher values in the SSF series (2.09 +/- 2.74° vs 0.94 +/- 1.17°; p = 0.139). Considering post-operative refractive error in diopters by MAE calculations, there was an underestimation of IOL power in the SSF group which was only statistically significant for Barrett Universal II (1.07 vs 0.32; p = 0.028) and Hill-RBF (0.95 vs 0.26; p = 0.024) formulas, but not for SRK/T (0.99 vs 0.42; p = 0.285) and Kane (0.96 vs 0.33; p = 0.083).

CONCLUSION

Sutured scleral fixation of capsular tension segments in the presence of zonular instability does not seem to induce clinically significant IOL tilt compared to uneventful cataract extraction cases.

Refractive errors occurring with tilt of intraocular lenses

A thin lens technique was developed to determine how the effective powers of toric monofocal intraocular lenses (IOLs) are influenced by tilt and the refractive errors associated with the tilt. A series of steps determined the effective power of the cornea at the IOL, the IOL power, the effective power of the tilted IOL, the correction required at the front of the eye and the power of an IOL that would compensate for the tilt. The correction was determined by starting at the ideal reduced image vergence at the IOL, backwards raytracing to obtain a reduced image vergence at the cornea, and subtracting the cornea power from this reduced image vergence. Examples are presented for different situations where the IOL is either tilted about the vertical or an oblique axis. Raytracing with a thick lens verified the accuracy of the technique.

Postoperative intraocular lens stability following cataract surgery with or without primary posterior continuous curvilinear capsulorrhexis: an intra-individual randomized controlled trial

PURPOSE

To evaluate the effect of primary posterior continuous curvilinear capsulorrhexis (PPCCC) on the positional stability of IOLs.

METHODS

This study is a prospective intra-individual comparative randomized controlled trial including 31 patients (62 eyes). Eyes of the same patient were randomly assigned to the PPCCC group (18 right eyes and 13 left eyes) or group without PPCCC (NPCCC group). Eyes in both groups were implanted with a one-piece foldable hydrophobic acrylic IOL via routine cataract surgery. Patients in the PPCCC group underwent additional manual PPCCC before IOL implantation. Examinations were performed 1 day, 1 week, 1 month and 3 months postoperatively. IOL tilt (x, y), decentration (x, y), anterior chamber depth (z) and refractive prediction error data were collected and analyzed with Pentacam.

RESULTS

Postoperatively, the range of IOL position change over 3 months in PPCCC group was comparable to NPCCC group, which indicated smaller value in every tilt and decentration index. PPCCC eyes showed comparable tilt and decentration with NPCCC eyes in this study endpoint: mean tilt (x, y), decentration (x, y) and anterior chamber depth (ACD) were 1.04 ± 0.56°, 0.90 ± 0.64°, 0.239 ± 0.140 mm, 0.233 ± 0.133 mm and 4.01 ± 0.32 mm, respectively, in the PPCCC group vs. 1.09 ± 0.76°, 1.10 ± 0.82°, 0.252 ± 0.153 mm, 0.244 ± 0.155 mm and 4.01 ± 0.38 mm, respectively, in the NPCCC group. Refractive prediction error in the PPCCC group demonstrated a mild hyperopic shift vs. the NPCCC group (0.13 ± 0.50 vs. 0.05 ± 0.39; p = 0.208), and corrected distance visual acuity (CDVA) did not differ between the two groups (0.027 ± 0.014 vs. 0.059 ± 0.185; p = 0.377).

CONCLUSIONS

Comparable IOL tilt, decentration, ACD and refractive prediction error were observed in PPCCC eyes with that underwent routine cataract surgery. Little IOL position fluctuation and good visual acuity were shown in PPCCC group over time.

TRAIL REGISTRATION

The study was registered at the Chinese Clinical Trial Register Center on May 27th, 2020 (protocol code ChiCTR2000033304, 27/05/2020).

Analysis of the relationship between lens morphology and aberrations in patients with myopia: a cross-sectional study

PURPOSE

To investigate the relationship between lens morphology and aberrations in patients with myopia.

METHODS

This cross-sectional study included 155 patients with myopia in their right eyes. Spherical power and cylindrical power were achieved by cycloplegic autorefraction. The eyes were divided into three groups for analysis based on their spherical equivalent (SE) values. The 4 mm and 6 mm ocular and internal aberrations were measured using the OPD-scan III. Lens parameters were measured using CASIA2, including lens thickness (LT), radius of anterior/posterior lens surface curvature (RAL/RPL), lens decentration (DEC), and lens tilt (TILT). The differences of lenticular parameters and aberration parameters among the three groups analyzed with ANOVA or Kruskal Wallis test. Pearson correlation or Spearman correlation analysis was performed to evaluate the relationships between the lens parameters and aberrations. A p value < 0.05 indicated statistical significance.

RESULTS

The difference in LT, RAL, DEC and TITL among the three groups was statistically significant (p < 0.05). And there were differences among differences in internal high-order aberrations, spherical aberration, and coma aberration(p < 0.05).Spherical power was positively correlated with LT and TITL (p < 0.05) and negatively correlated with DEC, RAL, and RPL (p < 0.05). Cylindrical power was positively correlated with LT (p < 0.05) and negatively correlated DEC (p < 0.05); The lenticular parameters (LT, RAL, DEC, and TILT) were mainly correlated with the ocular and internal spherical aberration. LT and DEC were correlated with ocular and internal higher-order aberrations and coma aberration.

CONCLUSION

DEC and LT were the main factors affecting aberrations in patients with myopia.

Imaging analysis of the biological parameters of the lens in patients with cortical age-related cataracts using ultrasound biomicroscopy

BACKGROUND

The spatial position of the lens in patients with cortical age-related cataract (CARC) is unclear. We investigated a basis for the assessment of visual quality after cataract surgery by analysing the ultrasound biomicroscopic characteristics of the biological parameters of the lens in patients with CARC.

METHODS

In this retrospective study, 119 patients (50 males and 69 females, totalling 238 eyes) with CARC who underwent simple cataract surgery were selected. The lens thickness (LT), axial length (AL), anterior chamber depth (ACD), lens vault (LV), trabecular-iris angle (TIA), iris-lens angle (ILA), iris-lens contact distance (ILCD) were measured by A-scan ultrasound and ultrasound biomicroscopy. The corresponding lens position (LP) and relative lens position (RLP) were calculated.

RESULTS

LP was greater in men than in women (P < 0.05), LV was smaller in men than in women (P = 0.002), ILA and ILCD were not statistically significant (P = 0.072 and P = 0.854, respectively). There were significant differences in TIA, ILA, and ILCD in the four quadrants (all P < 0.05), with a trend in the distribution of TIA: superior < inferior < nasal < temporal, ILA: nasal < inferior < temporal < superior, and ILCD: superior < temporal < inferior < nasal.

CONCLUSIONS

The lens protrudes more obviously in females than in males and the lens tilts to a certain extent with the increase of age and tends to be more upward and temporal in the supine position. Therefore, trends in lens-related parameters in patients with CARC should be taken seriously.

Influence of a multifocal intraocular lens centration and eye angles on light distortion and ocular scatter index

PURPOSE

To assess how eye axes and multifocal intraocular lens (MIOL) centration may impact the light distortion index (LDI) and ocular scatter index (OSI).

METHODS

Fifty-eight subjects implanted with the trifocal MIOL Q-Flex M 640PM or Liberty 677MY (Medicontur) were included in this retrospective analysis. The following variables were collected with the Pentacam Wave (Oculus) considering the vertex normal as the coordinates center: chord-mu to the center of the pupil, chord-alpha to the geometrical center of the cornea, and chord-MIOL to the center of the diffractive ring. These measurements were correlated with OSI (HD Analyzer, Visiometrics) and LDI (light distortion analyzer, CEORLab).

RESULTS

Chord-MIOL centroid was 0.12 mm at 62°, chord-mu was 0.09 mm at 174°, and chord-alpha was 0.38 mm at 188°. A relationship was found between OSI and LDI, rho = 0.58, p < 0.0005). No relationships were found between chord-mu or chord-alpha and the LDI or OSI, neither for the total magnitude, nor the decomposition in orthogonal components (p > 0.05). The LDI was significantly correlated with the temporal centration of the MIOL versus the vertex normal (rho = 0.32, p = 0.02).

CONCLUSIONS

As opposed to what has been previously described, the temporal centration of the MIOL was related to a decrease in the LDI. Future studies with extreme values of the included variables are required to establish cut-offs for considering these variables as exclusion criteria in the implantation of a MIOL.

Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes

PURPOSE

In short eyes, to compare the predictive accuracy of newer intraocular lens (IOL) power calculation formulas using traditional and segmented axial length (AL) measurements.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas and East Valley Ophthalmology, Mesa, Arizona.

DESIGN

Multi-center retrospective case series.

METHODS

Measurements from an optical biometer were collected in eyes with AL <22 mm. IOL power calculations were performed with 15 formulas using 2 AL values: (1) machine-reported traditional AL (Td-AL) and (2) segmented AL calculated with the Cooke-modified AL nomogram (CMAL). 1 AL method and 7 formulas were selected for pairwise analysis of mean absolute error (MAE) and root mean square absolute error (RMSAE).

RESULTS

The study comprised 278 eyes. Compared with the Td-AL, the CMAL produced hyperopic shifts without differences in RMSAE. The ZEISS AI IOL Calculator (ZEISS AI), K6, Kane, Hill-RBF, Pearl-DGS, EVO, and Barrett Universal II (Barrett) formulas with Td-AL were compared pairwise. The ZEISS AI demonstrated smaller MAE and RMSAE than the Barrett, Pearl-DGS, and Kane. K6 had a smaller RMSAE than the Barrett formula. In 73 eyes with shallow anterior chamber depth, the ZEISS AI and Kane had a smaller RMSAE than the Barrett.

CONCLUSIONS

ZEISS AI outperformed Barrett, Pearl-DGS, and Kane. The K6 formula outperformed some formulas in selected parameters. Across all formulas, use of a segmented AL did not improve refractive predictions.

Rotational stability of a new toric intraocular lens with an advanced optical profile

PURPOSE

To examine the rotational stability of a new toric intraocular lens (IOL), the TECNIS Eyhance Toric II, over a course of 3 months.

SETTING

Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective unmasked single-center study.

METHODS

50 eyes of 50 patients with cataract and regular corneal astigmatism ≥0.75 diopters (D) were included. The TECNIS Eyhance Toric II IOL was implanted in 1 eye of each study patient. Images of the alignment axis of the IOL were taken intraoperatively, as well as at 1 hour, 1 week, and 3 months postoperatively. For the measurement of toric IOL rotation, images were superimposed on the basis of ocular landmarks. Uncorrected and corrected distance (4 m) and intermediate (66 cm) visual acuities were assessed at the 3-month visit.

RESULTS

There was no significant difference in the rotational position between the intraoperative and 3 month timepoints, with a mean rotation of 1.34 ± 1.46 degrees, in 27 examined eyes. ( P = 0.313). No patients had to undergo repositioning of the toric IOL. A significant reduction of refractive cylinder occurred from preoperatively 1.8 ± 1.1 to 0.40 ± 0.42 D at the 3-month visit ( P = .001; n = 43). The corrected distance visual acuity improved significantly from 0.28 ± 0.16 logMAR preoperatively to -0.01 ± 0.13 logMAR at 3 months postoperatively ( P = .001; n = 43).

CONCLUSIONS

The TECNIS Eyhance Toric II showed a good visual performance with no significant rotation over a course of 3 months and, therefore, an excellent rotational stability. The intraocular lens showed a good safety profile with no adverse events.

Building prediction models of clinically significant intraocular lens tilt and decentration for age-related cataract

PURPOSE

To explore the risk factors and construct nomogram models to predict the risks of clinically significant intraocular lens (IOL) tilt and decentration after cataract surgery in patients with age-related cataract.

SETTING

Zhongshan Ophthalmic Center, Guangzhou, China.

DESIGN

Prospective cohort study.

METHODS

207 patients (207 eyes) who underwent phacoemulsification combined with IOL implantation were enrolled in the study. Casia2 was used to measure the tilt and decentration of crystalline lenses and IOLs before and 3 months after surgery. Univariate and multivariate logistic regression analyses were used to determine the risk factors of clinically significant IOL tilt and decentration, and nomogram prediction models were constructed according to the results of the multivariate logistic regression analysis.

RESULTS

Two hundred and seven patients were included in analysis. 24 eyes (11.59%) and 16 eyes (7.73%) had clinically significant IOL tilt and decentration at 3 months after cataract surgery. Multivariate logistic regression analysis revealed that preoperative crystalline lens tilt and decentration were the risk factors for clinically significant IOL tilt (odds ratio [OR], 3.519, P < .001) and decentration (OR, 410.22, P = .001), respectively. Axial length was another association factor for clinically significant IOL decentration (OR, 2.155, P = .019). The risk models demonstrated good calibrations and discriminations for the predictions of clinically significant IOL tilt (receiver operating characteristic [ROC] area = 0.833, cutoff value = 6.5) and decentration (ROC area = 0.757, cutoff value = 0.08).

CONCLUSIONS

The good performances of our models suggested that they may be useful risk prediction tools for postoperative IOL tilt and decentration. The measurement of preoperative crystalline lens tilt and decentration should be one of the routine examinations before cataract surgery, especially for toric and multifocal IOLs.

Effects of Modified Haptics on Surgical Outcomes and Rotational Stability of Toric Intraocular Lens Implantation

PURPOSE

To assess the rotational stability of a new toric intraocular lens (IOL), TECNIS toric II (toric II), which is a modified version of the TECNIS toric IOL (toric I) with frosted haptics (Johnson & Johnson).

METHODS

A total of 101 eyes of 101 patients who had been treated with phacoemulsification and toric IOL implantation were included. Before and 1 day, 1 week, and 1 month after surgery, uncorrected (UDVA) and corrected (CDVA) distance visual acuity were measured. Preoperative corneal astigmatism and postoperative manifest refractive astigmatism at 1 day and 1 month were analyzed. At 1 day and 1 month postoperatively, the amount of IOL axis misalignment from the intended orientation, tilt, and decentration were measured using anterior segment optical coherence tomography.

RESULTS

Fifty-one eyes received the toric I IOL and 50 eyes received the toric II IOL. Toric I IOLs showed a significantly larger amount of axis misalignment than toric II IOLs at both 1 day (9.6 ± 7.6° vs 5.4 ± 4.8°, P = .003) and 1 month (9.1 ± 7.8° vs. 4.7 ± 4.2°, P = .003) postoperatively.The proportion of eyes with misalignment greater than 10° was significantly larger with toric I than toric II IOLs (P < .001). There were no significant differences between IOLs in the amount of residual astigmatism, UDVA, CDVA, and amount of tilt and decentration at 1 day and 1 month postoperatively.

CONCLUSIONS

The TECNIS toric II IOL with frosted haptics has significantly improved rotational stability compared to its previous model. [J Refract Surg. 2022;38(10):648-653.].

Leftover Astigmatism: The Missing Link Between Measured and Calculated Posterior Corneal Astigmatism

PURPOSE

To quantify the total eye astigmatism that is not accounted for by measurement of anterior corneal astigmatism and posterior corneal astigmatism and knowledge of intraocular lens (IOL) astigmatism and assess whether it is correlated with candidate sources of or correlates with leftover astigmatism.

METHODS

Vector subtraction of anterior corneal, posterior corneal, and IOL astigmatism from total eye astigmatism as represented by spectacle astigmatism to yield a value of "leftover" astigmatism that is neither corneal nor lenticular. This value was derived in a series of eyes following cataract surgery. This novel entity was examined for correlation with candidate sources of or correlates with leftover astigmatism.

RESULTS

In 103 pseudophakic eyes with known IOL toricity, mean leftover astigmatism was 0.71 ± 0.43 diopters. This was significantly correlated with against-the-rule anterior corneal astigmatism (P < .001).

CONCLUSIONS

Leftover astigmatism is clinically substantial. Because it is included in IOL cylinder power calculations based on refractive outcome, it may explain why methods of IOL cylinder power calculation using refractive outcome-based adjustments to anterior corneal astigmatism (previously described as adjustments for "posterior corneal astigmatism") are more successful than adjustment on the basis of measured posterior corneal astigmatism. [J Refract Surg. 2022;38(9):559-564.].

Risk factors associated with intraocular lens decentration after cataract surgery

PURPOSE

To identify risk factors associated with intraocular lens (IOL) decentration after uneventful phacoemulsification with IOL implantation.

DESIGN

A prospective cohort study METHODS: All patients underwent a general ophthalmologic examination. One month postoperatively, the magnitude and orientation of IOL decentration relative to the visual axis center were assessed using an OPD-Scan III aberrometer, and the vertical and horizontal decentration values were determined. Univariate and multivariate linear regression analyses were performed to evaluate the association between the IOL decentration and ocular biometric parameters.

RESULTS

In total, 143 eyes of 143 patients were enrolled. The mean decentration magnitude was 0.27±0.15 mm, and the decentration axis appeared at any orientation, with no orientation tendency. The horizontal and vertical decentration were -0.02±0.22 mm and 0.01±0.22 mm, respectively. Multivariate regression analysis showed that the white-to-white distance (WTW) and the magnitude of angle α were positively associated with the decentration magnitude (P<0.001, adj. R²=0.121), the horizontal angle κ and horizontal angle α were positively associated with the horizontal decentration (P<0.001, adj. R²=0.209), and the anterior chamber depth (ACD) and vertical angle κ were positively associated with the vertical decentration (P<0.001, adj. R²=0.152).

CONCLUSIONS

The IOL decentration magnitude was greater in patients with a larger WTW and a larger angle α, the horizontal decentration was greater in patients with a larger horizontal angle κ and a larger horizontal angle α, and the vertical decentration was greater in patients with a deeper ACD and a larger vertical angle κ. In these patients, premium IOLs should be implanted cautiously.

Clinically Significant Intraocular Lens Decentration and Tilt in Highly Myopic Eyes: A Swept-Source Optical Coherence Tomography Study

PURPOSE

To investigate the occurrence and risk factors of clinically significant intraocular lens (IOL) decentration and tilt in highly myopic eyes using swept-source anterior segment optical coherence tomography (SS-AS-OCT).

DESIGN

Cross-sectional study.

METHODS

This study included 334 participants (334 eyes) with high myopia, defined as axial length (AL) ≥26 mm, who underwent phacoemulsification with IOL implantation. Decentration and tilt of IOL were assessed by SS-AS-OCT. Clinically significant IOL decentration and tilt was defined as decentration ≥0.4 mm and tilt ≥7°. Routine preoperative and postoperative examinations included visual acuity, refraction, biometric measurement using IOLMaster 700 (Carl Zeiss Meditec), and objective visual quality evaluated by OPD-Scan III (Nidek Technologies).

RESULTS

Among the 334 highly myopic participants, 71 (21.3%) had clinically significant IOL decentration, and 26 (7.78%) had clinically significant IOL tilt. The proportion of clinically significant IOL decentration (37.1% vs 14.0%, P < .001) and tilt (16.2% vs 3.90%, P < .001) in those with AL ≥30 mm was significantly higher than in those with AL <30 mm. The multivariable logistic regression model showed only AL ≥30 mm was associated with clinically significant IOL decentration (odds ratio, 1.65; P = .002). AL ≥30 mm (odds ratio, 2.09; P = .001) was an independent risk factor for clinically significant IOL tilt after adjusting for confounders. AL ≥30.3 mm could effectively predict IOL decentration ≥0.6 mm (area under the curve, 0.802).

CONCLUSIONS

Participants with AL >30 mm have a higher risk of clinically significant IOL decentration and tilt, thus caution should be taken to implant multifocal or toric IOL for these patients.

Influence of angle alpha on visual quality after implantation of extended depth of focus intraocular lenses

Background

To assess postoperative changes in angle alpha, and to evaluate the postoperative visual quality of patients with different angle alpha values after implantation of extended depth of focus (EDOF) intraocular lenses (IOLs).

Methods

Seventy-nine eyes of 79 patients who had phacoemulsification with EDOF IOLs implantation were enrolled. A cut-off value of 0.3 mm, 0.4 mm, and 0.5 mm in preoperative angle alpha was chosen to divide eyes into groups. Distance, intermediate, and near visual acuities, modulation transfer function (MTF), and aberrations were recorded during a 6-month follow-up. A patient questionnaire was completed.

Results

There were no significant differences in angle alpha postoperatively compared to preoperatively. No significant differences were found in visual acuity and MTF between all groups. With 5 mm pupil diameter, there were significant differences of higher-order aberrations and spherical aberration in ocular aberration and internal aberration between angle alpha<0.4 mm and angle alpha≥0.4 mm. Additionally, significant differences of coma were also added in cut-off value of 0.5 mm. When the value of angle alpha is 0.4 mm or higher, there were significant differences in the score of halos and glare.

Conclusions

Angle alpha did not affect visual acuity, but the value of 0.4 mm or higher in angle alpha affected the visual quality under scotopic conditions and occurrence of halos and glare. For patients with 0.4 mm or higher in angle alpha, the choice to implant a EDOF IOL should be carefully considered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02302-4.

Comparison of corneal surgically induced astigmatism calculations based on keratometry measurements made by 2 biometric devices

PURPOSE

To compare calculated corneal surgically induced astigmatism (SIA) by means of anterior-based keratometry (K) and total keratometry (TK) measurements made by 2 biometric devices.

SETTING

Ophthalmology Department, Shaare Zedek Medical Center, Jerusalem, Israel.

DESIGN

Retrospective, consecutive case series.

METHODS

The medical records of patients who had undergone cataract surgery through a 2.4 mm temporal clear corneal incision by a single surgeon between March 2018 and November 2020 were retrospectively reviewed. Patients for whom there were preoperative and postoperative K measurements assessed by 2 biometric devices, optical low-coherence reflectometry (OLCR) (Lenstar LS900, Haag-Streit, software v. eye suite i/9.1.0.0) and swept-source optical coherence tomography (SS-OCT) (IOLMaster700, Carl Zeiss Meditec AG, software v. 1.80.6.60340), were identified. Corneal SIA (mean vector value) was calculated by vector analysis for 3 groups: SS-OCT(K), SS-OCT(TK), and OLCR(K). Bivariate analyses were applied for comparisons.

RESULTS

147 eyes of 123 patients (73 right eyes and 74 left eyes) were enrolled in the study. The right eye corneal SIA values were 0.09 diopters (D) @ 136 degrees, 0.09 D @ 141 degrees, and 0.07 D @ 123 degrees for the SS-OCT(K), SS-OCT(TK), and OLCR, respectively. The corresponding left eye corneal SIA values were 0.13 D @ 120 degrees, 0.11 D @ 123 degrees, and 0.08 D @ 120 degrees. There were no statistically significant differences between the mean vector value and variance of the corneal SIA for the right (P = .78 and P = .65) and the left (P = .75 and P = .37) eyes of the 3 groups.

CONCLUSIONS

Corneal SIA values were low (0.07 to 0.13 D) and similar for the SS-OCT and the OLCR biometric devices with standard K measurements. TK measurements yielded similar corneal SIA values compared with anterior corneal-based measurements.

Preoperative Factors Affecting Visual Acuity Following the Implantation of Diffractive Multifocal Intraocular Lenses

PURPOSE

To investigate the preoperative factors affecting visual acuity after the implantation of a diffractive multifocal intraocular lens.

METHODS

This study evaluated 774 eyes of 774 patients who underwent cataract surgery with TECNIS Multifocal ZLB00 lens (Johnson & Johnson Surgical Vision) implantation. Anterior segment optical coherence tomography (CASIA2; Tomey Corporation) was performed as a part of the preoperative eye examination. Sex, age, axial length, and CASIA2 parameters, such as crystalline lens diameter and lens tilt relative to the corneal topographic axis, were investigated. The eyes considered were classified into good (20/20 or better) or poor (worse than 20/20) far vision groups based on corrected distance visual acuity, and good (20/25 or better) or poor (worse than 20/25) near vision groups based on distance-corrected near visual acuity, respectively. Preoperative characteristics of both groups were compared to determine factors affecting postoperative visual acuity.

RESULTS

Multivariate logistic regression analysis revealed that older age (P < .001), a short axial length (P = .010), and a large lens tilt (P < .001) were associated with poor near vision. There was no significant difference between the two far vision groups. There was a significant negative correlation between lens tilt and axial length (r = -0.513, P < .001).

CONCLUSIONS

The results of this study suggest that age, axial length, and lens tilt to the corneal topographic axis may predict poor visual acuity after the implantation of a diffractive multifocal intraocular lens. Eyes with a short axial length tended to have a large degree of lens tilt and should be considered particularly carefully. [J Refract Surg. 2021;37(10):674-679.].

Distributions of crystalline lens tilt and decentration and associated factors in age-related cataract

PURPOSE

To investigate the characteristics and factors associated with crystalline lens tilt and decentration measured by CASIA2 anterior segment optical coherence tomography.

SETTING

Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.

DESIGN

Cross-sectional study.

METHODS

1097 eyes of 1097 patients who planned to undergo cataract surgery were enrolled. All patients underwent a general ophthalmologic examination. Lens thickness (LT), front curvature radius (FCR), back curvature radius, lens equator diameter (LED), tilt, and decentration of preoperative crystalline lenses were measured by CASIA2. Univariate and multivariate regression analyses were performed to evaluate the relationships between the tilt and decentration of crystalline lens with related factors.

RESULTS

The natural crystalline lenses showed a mean tilt of 5.16 degrees toward the inferotemporal direction and a mean decentration of 0.22 mm toward the temporal direction. Of the total 1097 eyes, 119 eyes (10.85%) had a tilt greater than 7 degrees, and 89 eyes (8.11%) had a decentration more than 0.4 mm. Multivariate regression analysis showed that larger decentration, thicker LT, shorter axial length (AL), and FCR were associated with greater lens tilt (P < .001, P = .007, P = .006, and P = .003, respectively). In addition, greater tilt, older and thinner LT were correlated with larger decentration (all P < .001).

CONCLUSIONS

Preoperative crystalline lens had a certain degree of tilt and decentration in age-related cataract. The greater tilt of the crystalline lens was, the larger decentration of it was. In addition, AL, FCR, LT, and age also correlated with tilt and decentration.

Stability of Intraocular Lens With Different Haptic Design: A Swept-Source Optical Coherence Tomography Study

Purpose: To investigate the stability of intraocular lens (IOLs) with different haptics by swept-source anterior-segment optical coherence tomography (AS-OCT).

Methods: Sixty-eight eyes from 55 patients received the implantation of Rayner 920H (Closed C-loop Group), Zeiss 509M (Plate Group) or Lenstec SOFTEC HD (C-loop Group) IOLs. The tilt and decentration of IOLs were evaluated using AS-OCT at least 1 month postoperatively.

Results: Mean decentration and tilt of IOLs were 0.18 ± 0.12 mm (range 0.02 to 0.59 mm) and 5.63 ± 1.65° (range 2.2 to 9.6°) respectively. Decentration was significantly smaller in the plate haptic group (0.12 ± 0.06 mm) as compared to the C-loop group (0.22 ± 0.13 mm, P = 0.02). The tilt of IOL was also significantly smaller in the plate haptic group (4.96 ± 0.89°) as compared to the C-loop group (6.28 ± 1.83°, P = 0.01). There was marginal difference between the Closed C-loop group (5.52 ± 1.74°) and C-loop group (6.28 ± 1.83°, P = 0.07).

Conclusions: The Plate-haptic IOLs should have better stability for the decentration and tilt than the C-loop design IOLs.

Three-Dimensional Reconstruction and Swept-Source Optical Coherence Tomography for Crystalline Lens Tilt and Decentration Relative to the Corneal Vertex

Purpose

To investigate crystalline lens tilt and decentration with respect to the corneal vertex (CV) using swept-source optical coherence tomography (SS-OCT) combined with three-dimensional (3D) reconstruction.

Methods

Thirty consecutive patients with cataract (30 right eyes) were included in this prospective, observational, pilot case series study. SS-OCT anterior segment images and 3D reconstructions were used for data analysis.

Results

The mean distance between the central points of crystalline lens plane and limbus plane was approximately 0.33 ± 0.18 mm. The distance of the center of the limbus plane relative to the CV was approximately 0.31 ± 0.14 mm, which approximated the distance of the center of the crystalline lens plane relative to the CV at 0.33 ± 0.20 mm (P = 0.354). However, the centers of the limbus and crystalline planes were not in the same quadrant in 80% of eyes (24/30). Moreover, the crystalline lens tilted by approximately 4.16° ± 1.97° relative to the CV.

Conclusions

The center of the limbus plane was not consistent with that of the crystalline lens plane. The tilt and decentration of the crystalline lens were natural phenomena.

Translational Relevance

The SS-OCT technology combined with 3D reconstruction was useful for quantifying the tilt and decentration of the crystalline lens. The definition of angle alpha used for premium IOL screening should be updated.

Distribution of angle α and angle κ in a population with cataract in Shanghai

PURPOSE

To describe the distribution of angle α and angle κ in a population with cataract in Shanghai.

SETTING

Eye and Ear, Nose, Throat Hospital, Fudan University, Shanghai, China.

DESIGN

Hospital-based, cross-sectional study.

METHODS

Angle α, angle κ, and other ocular biometric parameters were determined by IOLMaster 700. The distributions of angle α and angle κ and their associations with systemic and ocular parameters were assessed.

RESULTS

This study included 15 127 eyes of 15 127 cataract patients. The mean angle α and angle κ values were 0.45 ± 0.21 mm and 0.30 ± 0.18 mm, respectively. Angle α and angle κ were both predominantly located temporal to the visual axis. A greater angle α or angle κ was associated with older age, lower corneal power, shorter white-to-white distance, and shallower anterior chamber depth (all P < .05). Angle α correlated positively with angle κ. With increasing axial length (AL), angle α gradually decreased in a nonlinear way and shifted to the nasal side of the visual axis, whereas angle κ decreased in eyes with AL less than 27.5 mm but increased again in eyes with longer AL.

CONCLUSIONS

Angle α and angle κ, both predominantly located temporal to the visual axis, were influenced by multiple anterior segment parameters. As AL increased, the changes in angle α and angle κ were nonlinear, and their locations gradually shifted from the temporal to the nasal side of the visual axis.

Characteristics and factors associated with intraocular lens tilt and decentration after cataract surgery

PURPOSE

To analyze the characteristics and factors associated with intraocular lens (IOL) tilt and decentration after uneventful phacoemulsification with IOL implantation.

SETTING

Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.

DESIGN

Cross-sectional study.

METHODS

All patients underwent a general ophthalmologic examination and anterior segment photography. IOL tilt and decentration were measured with a second-generation anterior segment optical coherence tomography (Casia2). Univariate and multivariate regression analyses were performed to assess the association between IOL tilt and decentration with ocular biometric and systemic parameters, and the visual acuity.

RESULTS

A total of 196 eyes of 196 patients were enrolled in this study. IOLs showed a mean tilt of 4.8 degrees toward the inferotemporal direction, and the mean decentration was 0.21 mm. Both eyes presented a mirror symmetry relationship. Twenty-two eyes (11.22%) had a tilt greater than 7 degrees, and 21 eyes (10.72%) had a decentration more than 0.4 mm. Multivariate regression analysis showed previous pars plana vitrectomy (PPV) and short axial length (AL) were associated with greater IOL tilt (P = .014 and P < .001). In addition, long AL, thicker lens, and less capsulorhexis-IOL overlap were positively correlated with decentration (P < .001, P = .029, and P = .026). Corrected distance visual acuity did not directly correlate with IOL tilt and decentration (P = .417 and P = .550).

CONCLUSIONS

PPV history and short AL were associated with greater IOL tilt, whereas longer AL, thicker lens, and overlarge capsulorhexis contribute to greater decentration. Implantation of toric and multifocal IOLs in these patients should be cautious.

Prospective comparison of apex-centered vs standard pupil-centered femtosecond laser-assisted capsulotomy in cataract surgery

PURPOSE

To compare the lens tilt after apex-centered capsulotomy with standard pupil-centered capsulotomy.

SETTING

Clinical practice.

DESIGN

Prospective, randomized, investigator-masked trial.

METHODS

This prospective, randomized, investigator masked study included 40 patients with age-related cataract scheduled for femtosecond laser-assisted cataract surgery (FLACS) in both eyes. The main outcome was the tilt of the intraocular lens (IOL), measured with the IOLMaster 700.

RESULTS

The study enrolled 80 eyes of 40 patients. The mean distance from the center of the apex-centered capsulotomy to the pupil-centered capsulotomy was 175.8 ± 97.2 μm. The amount of IOL tilt was not significantly reduced with the new technique (P > .05). Tilt orientation was more stable in eyes treated with apex-centered capsulotomy.

CONCLUSIONS

Centration of the capsulotomy on the lens apex in FLACS does not influence the amount of IOL tilt but the orientation stability. The clinical importance of this finding has to be further elucidated.

The role of posterior corneal power in 21st century biometry: A review

PURPOSE

Intraocular lens (IOL) calculation and biometry have evolved significantly in recent decades. However, present outcomes are still suboptimal. Our objective is to summarize the results reported in the literature with regard to a new variable, the value of the relationship between anterior and posterior corneal curvature in the biometric calculation of IOL power.

METHODS

We have created a narrative revision of the existing evidence regarding the posterior to anterior corneal curvature ratio in IOL calculation.

RESULTS

The corneal posterior/anterior ratio (P/A ratio), also called Gullstrand ratio, has a standard deviation of 2.4% in normal people, hence causing a possible IOL power miscalculation error of up to 0.75 diopters (D). This error is magnified in pathological corneas or in those with previous refractive surgery. Including the P/A ratio in the IOL formula reduces errors in the calculation of IOL power.

CONCLUSIONS

Measurement of the posterior corneal surface should be recommended prior to IOL calculation, given the demonstrated results regarding the P/A ratio for IOL power calculation. Regarding toric IOL calculation, we suggest incorporation of all internal astigmatic vectors, for instance, posterior corneal surface, IOL tilt induced toricity, and retinal astigmatism. All of these factors may improve surgical outcomes.

Anterior segment optical coherence tomography imaging and ocular biometry in cataract patients with open angle glaucoma comorbidity

BACKGROUND

Anterior chamber angle anatomy in perspective of ocular biometry may be the key element to intraocular pressure (IOP) reduction, especially in glaucoma patients. We aim to investigate anterior chamber angle and biometrical data prior to cataract surgery in patients with and without glaucoma comorbidity.

MATERIALS AND METHODS

This prospective comparative case-control study included 62 subjects (38 with cataract only and 24 with cataract and glaucoma). A full ophthalmic examination including, Goldmann applanation tonometry, anterior chamber swept source optical coherence tomography (DRI OCT Triton plus (Ver.10.13)) and swept source optical biometry (IOL Master 700 v1.7) was performed on all participants.

RESULTS

We found that ocular biometry parameters and anterior chamber parameters were not significantly different among groups. However, when we added cut-off values for narrow angles, we found that glaucoma group tended to have more narrow angles than control group. IOP was higher in glaucoma group despite all glaucoma patients having medically controlled IOP. In all subjects, anterior chamber parameters correlated well with lens position (LP), but less with relative lens position, while LP cut-off value of 5.1 mm could be used for predicting narrow anterior chamber angle parameters.

CONCLUSIONS

Cataract patients tend to develop narrow anterior chamber angles. Anterior chamber angle parameters have a positive moderate to strong relationship with lens position. LP may be used predicting narrow angles.

Age-related Changes in Crystalline Lens Tilt and Decentration: A Swept-source Optical Coherence Tomography Study

Purpose

To investigate the age-related tilt and decentration of crystalline lenses using a swept-source optical coherence tomography biometer (Casia 2, TOMEY, Japan).

Setting

Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China.

Design

Cross-sectional study.

Methods

The direction and magnitude of the crystalline lens were evaluated in 230 participants with ages ranging from 7 to 90 years using swept-source optical coherence tomography. The participants were divided into four age groups, and the differences among the groups were analyzed. Multiple linear regression was used to investigate the main factors influencing crystalline lens tilt and decentration.

Results

The natural crystalline lens tilted towards the inferotemporal direction with a mean magnitude of 4.3+/-1.5[degrees] (range 0.7-8.95[degrees]). The average decentration toward the superotemporal direction was 0.17+/-0.12 mm (range 0.03-1.15 mm). There was mirror symmetry between the right and left eyes. There were significant differences in the crystalline lens tilt and decentration among the age groups. Multiple linear regression showed that changes in crystalline lens tilt depended on angle [alpha] (p<.01) and anterior chamber depth (ACD; P=.008), while crystalline lens decentration depended on angle [kappa] (P=.003), age (P<.01), and angle [alpha] (P=.002).

Conclusions

Although there was a significant difference in crystalline lens tilt and decentration among age groups, the variation in the crystalline lens position was partially affected by age. The crystalline lens tilt was greater in eyes with wider angle [alpha] and shallower ACD, while crystalline lens decentration was greater in younger eyes with wider angles [kappa] and [alpha].

Rotational stability of modified toric intraocular lens

We evaluated the rotational stability of a new toric intraocular lens (IOL), HOYA XY-1 toric IOL that is an improved version of HOYA 355 toric IOL, with longer overall length (13.0 mm vs. 12.5 mm), shortened unfolding time, and texture processing of the surface of haptics. Data from 193 eyes of 165 patients (76.4 ± 8.3 years old) with preoperative corneal astigmatism exceeding 0.75 diopters who had undergone phacoemulsification and toric IOL implantation were collected and analyzed. Corneal astigmatism, refractive astigmatism, and uncorrected (UDVA) and corrected distance visual acuity (CDVA) were evaluated before and 1 day, 1 week, and 1 month after surgery. The degree of IOL decentration, IOL tilt, and toric axis misalignment was assessed at 1 day and 1 month postoperatively. Fifty eyes received AcrySof toric IOL, 51 eyes TECNIS toric IOL, 46 eyes HOYA 355 toric IOL, and 46 eyes HOYA XY-1 toric IOL. The amount of axis misalignment from the intended axis was significantly different among IOLs (p = 0.004, one-way ANOVA), and HOYA XY-1 showed significantly less amount of axis misalignment than TECNIS (p = 0.020, Tukey’s multiple comparison) and HOYA 355 (p = 0.010). The proportion of eyes that showed axis misalignment <10° at 1 month postoperatively was significantly higher with HOYA XY-1 toric IOL than with other toric IOLs (χ² test, p = 0.020). HOYA XY-1 toric IOL, the modified version of HOYA 355 toric IOL, showed excellent rotational stability in comparison with other models of toric IOLs.

Angle alpha orientation and magnitude distribution in a cataract surgery population

PURPOSE

To report normative angle alpha orientation and magnitude distribution in a cataract surgery patient population.

SETTING

U.S. academic medical center.

DESIGN

Retrospective review.

METHODS

A total of 11 871 wavefront aberrometer/corneal topographer angle alpha measurements were performed over 40 months, yielding 8773 bilateral measurements (73.9%) with zero bad wavefront datapoints. The analysis was limited to the first right-eye scan for 3382 unique patients. The angle alpha magnitudes (millimeters) and orientations (degrees) were analyzed for these unique right eyes.

RESULTS

For the 3,382 unique patients, the mean angle alpha magnitude was 0.44 ± 0.15 mm (median, 0.44 mm; 25th and 75th percentiles 0.34 mm, 0.53 mm). Angle alpha orientation was predominantly horizontal (P < .01), with a mean of 186 ± 32 degrees. The expected point of intraocular lens (IOL) centration (EPIC) based on the geometric center of the corneal limbus was temporal to the visual axis in 3212 eyes (95%), nasal in 92 eyes (2.7%), inferior in 56 eyes (1.7%), and superior in 22 eyes (0.6%). The mean angle alpha magnitude was 0.3 mm or less in 607 eyes (18%) and 0.5 mm or greater in 1089 eyes (32%).

CONCLUSIONS

Angle alpha is a predominantly horizontal phenomenon with a mean EPIC of 0.44 mm temporal to the visual axis. This information may assist in determining eligibility for patients in multifocal IOL implantation.

Misalignment and tilt effect on aspheric intraocular lens designs after a corneal refractive surgery

PURPOSE

To numerically evaluate and compare the tolerance to misalignment and tilt of aspheric intraocular lenses (IOLs) designed for three eyes: with standard cornea and with simulated corneas after myopic and hyperopic laser ablation surgery.

METHODS

Three aspheric IOLs of +20.00 diopter (D) with different spherical aberration (SA) ([Formula: see text]) values have been designed using a theoretical model eye. Drastic changes on the theoretical eye anterior corneal asphericity have been performed to simulate myopic and hyperopic refractive surgeries. The effect of IOL misalignment and tilt on the image quality has been evaluated using a commercial optical software design for the three eye models. Image quality was assessed from the modulation transfer function (MTF), root mean square (RMS) values of defocus, astigmatism, coma and spherical aberration ([Formula: see text]), and retinal images obtained from a visual simulator using an aleatory optotype of 0.00 LogMar visual acuity (VA).

RESULTS

IOL misalignment and tilt reduced MTF values in general, and increased wavefront aberrations errors. Aberration-free IOLs maintained best the MTF values when misalignments were applied, together with good on-axis optical quality. IOLs with negative SA ([Formula: see text]) correction decreased the MTF value under 0.43 for misalignments values higher than 0.50 mm with the three corneas. The effect of misalignment on RMS astigmatism and coma was correlated with the IOL SA ([Formula: see text]) and with the three corneas.

CONCLUSIONS

This theoretical study shows that the largest degradation in image quality arises for the IOL with the highest amount of spherical aberration ([Formula: see text]). Moreover, it has been found that the aspherical design has a more influential role in misalignment tolerance than in tilt tolerance.

A Geometric Theory Integrating Human Binocular Vision With Eye Movement

A theory of the binocular system with asymmetric eyes (AEs) is developed in the framework of bicentric perspective projections. The AE accounts for the eyeball's global asymmetry produced by the foveal displacement from the posterior pole, the main source of the eye's optical aberrations, and the crystalline lens' tilt countering some of these aberrations. In this theory, the horopter curves, which specify retinal correspondence of binocular single vision, are conic sections resembling empirical horopters. This advances the classic model of empirical horopters as conic sections introduced in an ad hoc way by Ogle in 1932. In contrast to Ogle's theory, here, anatomically supported horopteric conics vary with the AEs' position in the visual plane of bifoveal fixations and their transformations are visualized in a computer simulation. Integrating horopteric conics with eye movements can help design algorithms for maintaining a stable perceptual world from visual information captured by a mobile robot's camera head. Further, this paper proposes a neurophysiologically meaningful definition for the eyes' primary position, a concept which has remained elusive despite its theoretical importance to oculomotor research. Finally, because the horopteric conic's shape is dependent on the AE's parameters, this theory allows for changes in retinal correspondence, which is usually considered preformed and stable.

Comparison of the Stability of Two Intraocular Lenses in Primary Angle-Closure Glaucoma after Phacoemulsification

Objective. To observe the stability of intraocular lenses (IOLs) in primary angle-closure glaucoma by ultralong scan depth spectral-domain optical coherence tomography (UL-OCT) after phacoemulsification. Methods. A prospective, randomized study. 73 patients (82 eyes) with primary closed-angle glaucoma and age-related cataract were included in the study. 42 eyes were implanted with ZCB00, while 40 eyes were implanted with Softec HD after phacoemulsification. The tilt, decentration, and space between IOL and posterior capsule (IOL-PC space) were analyzed using UL-OCT at 1 week, 1 month, and 3 months after surgery. The intergroup difference was compared with the paired t-test. Result. The difference of decentration and tilt was not statistically significant (both $P>0.05$ ) both in the horizontal and vertical positions at 1 week, 1 month, and 3 months postoperatively. The horizontal IOL-PC space is 0.111 ± 0.091 mm2, 0.044 ± 0.066 mm2, and 0.055 ± 0.055 mm2 in the Softec HD group and 0.458 ± 0.488 mm2, 0.497 ± 0.363 mm2, and 0.492 ± 0.441 mm2 in the ZCB00 group. The vertical IOL-PC space is 0.102 ± 0.061 mm2, 0.037 ± 0.052 mm2, and 0.053 ± 0.079 mm2 in the Softec HD group and 0.692 ± 0.815 mm2, 0.510 ± 0.415 mm2, and 0.691 ± 0.635 mm2 in the ZCB00 group. The difference was statistically significant ( $P<0.05$ ) both in the horizontal and vertical positions except for the first week on the horizon. The Softec HD group is smaller than the ZCB00 group. Conclusion. There is no difference in the stability of the IOL although the IOL-PC space is different. The thickness of IOL may affect the IOL-PC space.

The Structure of the Lens and Its Associations with the Visual Quality

In humans, the lens is the organ with the ability to change morphology and refractive power, designated as accommodation, to focus light from various distances and obtain clear retinal image. The accommodative ability of the lens depends on its structure and biological parameters. The lens grows throughout the life, forming specific lens sutures and a unique gradient refractive index, and possesses regenerative ability under certain circumstances. Minimally invasive lens surgery that preserves endogenous lens epithelial stem/progenitor cells (LECs) can achieve functional lens regeneration in humans. The lens is the main source of intraocular aberration, especially intraocular higher-order aberrations (IHOAs) which is found to be binocularly symmetrical in phakic eyes. There is a compensation mechanism between corneal aberrations and lens aberrations. Therefore, the structure and the biological parameters of the lens, the binocular relationship of the lens and the correlation between the lens and cornea affect visual quality. This paper summarises the above findings and their current and potential applications in refractive surgeries, providing a comprehensive understanding of the lens as a strong determinant of visual quality in the optical system.

Determinants of intraocular lens tilt and decentration after cataract surgery

Background

To identify the main determinants of intraocular lens (IOL) tilt and decentration after cataract surgery using a novel anterior segment optical coherence tomography (AS-OCT) method.

Methods

Fifty-six patients who underwent phacoemulsification with IOL implantation in one eye were continuously enrolled in this cohort study. Axial length (AL) was measured with IOL Master 700. The tilt and decentration of patients’ preoperative crystalline lenses and postoperative IOLs, as well as crystalline lens thickness (LT), were measured using AS-OCT before surgery and 1 week after surgery.

Results

The mean tilt and decentration of the patients’ preoperative crystalline lenses were 4.90°±1.81° and 0.21±0.02 mm, and the mean tilt and decentration of IOLs were 4.75°±1.66° and 0.21±0.02 mm, respectively. There were no significant differences in magnitude, direction of tilt, or decentration between crystalline lenses and IOLs. The strongest determinant of IOL tilt was preoperative crystalline lens tilt (R²=0.512, P<0.001), followed by AL (R²=0.154, P=0.003). Additionally, crystalline lens decentration and AL explained 54.6% of the variability in IOL decentration. AL was the factor most highly associated with IOL decentration (R²=0.332, P<0.001), rather than crystalline lens decentration (R²=0.214, P<0.001).

Conclusions

The position of the preoperative crystalline lens and AL were the critical determinants of IOL tilt and decentration. The tilt and decentration of IOLs will be greater in patients with larger tilt and decentration of crystalline lenses, or shorter and longer AL.

Effect of Intraocular Lens Tilt and Decentration on Visual Acuity, Dysphotopsia and Wavefront Aberrations

Tilt and decentration of intraocular lenses (IOL) may occur secondary to a complicated cataract surgery or following an uneventful phacoemulsification. Although up to 2–3° tilt and a 0.2–0.3 mm decentration are common and clinically unnoticed for any design of IOL, larger extent of tilt and decentration has a negative impact on the optical performance and subsequently, the patients’ satisfaction. This negative impact does not affect various types of IOLs equally. In this paper we review the methods of measuring IOL tilt and decentration and focus on the effect of IOL tilt and decentration on visual function, in particular visual acuity, dysphotopsia, and wavefront aberrations. Our review found that the methods to measure the IOL displacement have significantly evolved and the available studies have employed different methods in their measurement, while comparability of these methods is questionable. There has been no universal reference point and axis to measure the IOL displacement between different studies. A remarkably high variety and brands of IOLs are used in various studies and occasionally, opposite results are noticed when two different brands of a same design were compared against another IOL design in two studies. We conclude that <5° of inferotemporal tilt is common in both crystalline lenses and IOLs with a correlation between pre- and postoperative lens tilt. IOL tilt has been noticed more frequently with scleral fixated compared with in-the-bag IOLs. IOL decentration has a greater impact than tilt on reduction of visual acuity. There was no correlation between IOL tilt and decentration and dysphotopsia. The advantages of aspheric IOLs are lost when decentration is >0.5 mm. The effect of IOL displacement on visual function is more pronounced in aberration correcting IOLs compared to spherical and standard non-aberration correcting aspherical IOLs and in multifocal versus monofocal IOLs. Internal coma has been frequently associated with IOL tilt and decentration, and this increases with pupil size. There is no correlation between spherical aberration and IOL tilt or decentration. Although IOL tilt produces significant impact on visual outcome in toric IOLs, these lenses are more sensitive to rotation compared to tilt.

Changes in ocular biometric measurements after vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment repair

Background

To observe the changes in ocular biometric measurements after vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment (RRD) repair.

Methods

Sixty-three phakic, macula-off RRD eyes underwent vitrectomy with silicone oil tamponade but not lens extraction were included in this retrospective study. Measurements of axial length (AL), anterior chamber depth (ACD), lens thickness (LT) using the new Zeiss IOLMaster 700 and derivative lens position (LP), relative lens position (RLP) and lens-retina distance (LRD) were compared and analyzed between preoperative and postoperative in phakic, macula-off eyes with RRD.

Results

Preoperative AL, ACD, LT, LP, RLP and LRD were 24.94 ± 1.82 mm, 3.45 ± 0.42 mm, 4.34 ± 0.16 mm, 5.55 ± 0.41 mm, 0.22 ± 0.01 and 19.52 ± 1.82 mm. After a mean 4.85-month duration of silicone oil tamponade, postoperative AL, ACD, LT, LP, RLP and LRD were 25.42 ± 2.20 mm, 3.30 ± 0.41 mm, 4.43 ± 0.21 mm, 5.46 ± 0.40 mm, 0.22 ± 0.02 and 20.17 ± 2.36 mm, respectively. The differences in all measurements are significant (all P < 0.05). Preoperative AL and LRD are positively while RLP is negatively correlated with change in LRD. Change in AL but not in LT or LP is correlated with change in LRD. Biometric measurements except LT between preoperative and postoperative were in close agreement.

Conclusion

The underestimation of AL and anterior shifting of lens in phakic, macula-off eyes with RRD after vitrectomy with silicone oil tamponade.

Impact of vitrectomy and air tamponade on aspheric intraocular lens tilt and decentration and ocular higher-order aberrations: phacovitrectomy versus cataract surgery

PURPOSE

To evaluate the impact of vitrectomy and air tamponade on aspheric intraocular lens (IOL) tilt and decentration and postoperative internal higher-order aberrations (HOAs) in combined cataract surgery and vitrectomy (phacovitrectomy).

STUDY DESIGN

Prospective comparative observational study.

METHODS

Forty-five eyes that underwent phacovitrectomy using aspheric IOLs and 18 eyes that only underwent cataract surgery also using aspheric IOLs were prospectively evaluated. The subjects were divided into three groups: phacovitrectomy without fluid-air exchange (F/Ax) or with F/Ax and cataract surgery alone (Groups A, B, and C, respectively) Surgery-induced changes in lens tilt and decentration and internal HOAs were compared between each pair of groups. Subgroup analysis was conducted for cases with largely tilted (> 7°) or decentered (> 0.40 mm) IOLs 1 month postoperatively.

RESULTS

Surgery-induced changes in lens tilt in Group B were significantly more pronounced than those in Group C at 1 week, 1 month, and 3 months postoperatively (P = 0.007, 0.009, and 0.043, respectively), while there was no significant difference in surgery-induced changes in lens decentration among the groups. IOLs in Group B were tilted and decentered toward the inferonasal direction. In contrast, there was no significant difference in internal HOAs among the groups at any postoperative visit. Only Group B included cases with largely decentered IOLs, and the internal total HOAs in these cases were significantly larger than those in the others (P = 0.015).

CONCLUSION

Although largely decentered IOLs were occasionally found in Group B, aspheric IOLs could be effectively used in phacovitrectomy.

Measurement of crystalline lens tilt in high myopic eyes before cataract surgery using swept-source optical coherence tomography

Background

To measure the crystalline lens tilt in eyes with various degrees of myopia before cataract surgery using swept-source optical coherence tomography (SS-OCT).

Methods

We used SS-OCT (IOLMaster 700) to scan 131 emmetropic eyes (axial length < 24.5 mm), 25 mild/moderate myopic eyes (axial length 24.5-26 mm), and 123 high myopic eyes (52, 29, and 42 eyes with axial lengths of 26-28, 28-30, and > 30 mm, respectively) as part of the routine preoperative examination before cataract surgery. SS-OCT involved B-scans along six meridians. The data were analyzed to assess the magnitude and orientation of the lens tilt and their correlation with other optical biometric parameters.

Result

The mean tilt was 3.36 ± 0.98° in emmetropic eyes, 3.07 ± 1.04° in mild/medium myopic eyes, and 2.35 ± 1.01° in high myopic eyes. Tilt correlated significantly and inversely with axial length (Pearson's r = - 0.427, P < 0.001). The crystalline lens tilt predominantly faced the upper outer quadrant relative to the visual axis, symmetrically in both eyes, with mean angles of 24.32° and 147.36° in the right and left eyes, respectively. The variability in the lens tilt direction increased with increasing axial length (χ² test, P < 0.001).

Conclusion

The magnitude of crystalline lens tilt decreased with increasing axial length. The direction of tilt was predominantly towards the upper outer quadrant in both eyes. The variability in the tilt orientation increased with increasing axial length.

Trial registration

NIH (clinicaltrial.gov), NCT03062085. Registered 23 February 2017.

Changes in angle kappa and angle alpha before and after cataract surgery

PURPOSE

To observe the distributions and changes in angle kappa and angle alpha preoperatively and postoperatively in patients with cataract who were implanted with a multifocal intraocular lens (mIOL).

SETTING

The First Affiliated Hospital of Northwest University, Shaanxi, China.

DESIGN

Prospective nonrandomized noncomparative case series.

METHODS

Eyes that underwent phacoemulsification were included. The magnitudes and orientations of angle kappa and angle alpha preoperatively and postoperatively were compared, respectively.

RESULTS

The study comprised 81 eyes of 70 patients. The magnitude of angle kappa significantly decreased after phacoemulsification. No significant differences were observed between preoperative and postoperative angle kappa in orientation, as well as between preoperative and postoperative angle alpha. The correlations between preoperative and postoperative angle kappa and angle alpha were significant. There were displacement vectors for angle kappa (0.15 ± 0.10) and angle alpha (0.12 ± 0.12) after phacoemulsification. Locations of angle kappa of right and left eyes were scattered mostly in the temporal side of corneal light reflection, whereas locations of angle alpha were well organized in the horizontal position on temporal sides of corneal light reflection.

CONCLUSIONS

The distribution of angle alpha was more organized compared with angle kappa. Angle kappa may change after phacoemulsification. During preoperative evaluation for patients with cataract planning for mIOLs implanted angle alpha may be a more reliable and stable factor compared with angle kappa.