Is randomisation necessary for measuring defocus curves in pre-presbyopes?

BCLA CLEAR Presbyopia: Evaluation and diagnosis

It is important to be able to measure the range of clear focus in clinical practice to advise on presbyopia correction techniques and to optimise the correction power. Both subjective and objective techniques are necessary: subjective techniques (such as patient reported outcome questionnaires and defocus curves) assess the impact of presbyopia on a patient and how the combination of residual objective accommodation and their natural DoF work for them; objective techniques (such as autorefraction, corneal topography and lens imaging) allow the clinician to understand how well a technique is working optically and whether it is the right choice or how adjustments can be made to optimise performance. Techniques to assess visual performance and adverse effects must be carefully conducted to gain a reliable end-point, considering the target size, contrast and illumination. Objective techniques are generally more reliable, can help to explain unexpected subjective results and imaging can be a powerful communication tool with patients. A clear diagnosis, excluding factors such as binocular vision issues or digital eye strain that can also cause similar symptoms, is critical for the patient to understand and adapt to presbyopia. Some corrective options are more permanent, such as implanted inlays / intraocular lenses or laser refractive surgery, so the optics can be trialled with contact lenses in advance (including differences between the eyes) to better communicate with the patient how the optics will work for them so they can make an informed choice.

Comparison of visual outcomes in patients implanted with Tecnis Eyhance ICB00 and 1-Piece ZCB00 monofocal intraocular lenses

PURPOSE

To compare the visual outcomes and monocular defocus curve of a new monofocal Tecnis Eyhance IOL (Tecnis ICB00) with Tecnis 1 single piece (ZCB00).

METHODS

Eighty patients diagnosed with cataract were divided into two groups: Tecnis ICB00 (n = 40) and ZCB00 (n = 40). The visual outcome was evaluated using the following parameters: uncorrected distance visual acuity (UDVA), uncorrected intermediate visual acuity (UIVA), uncorrected near visual acuity (UNVA), corrected distance visual acuity (CDVA), distance corrected intermediate visual acuity (DCIVA), corrected near visual acuity (CNVA), uncorrected visual acuity contrast sensitivity (UVACS), best-corrected visual acuity contrast sensitivity (BCVACS), manifest refraction, and defocus curve and was compared at the 6th week and 3 months after surgery.

RESULTS

The UIVA and UNVA were significantly (P < 0.05) better in ICB00 as compared with ZCB00 at 6 weeks and 3 months postoperative. The DCIVA was significantly better in ICB00 as compared with ZCB00 at 3 months postoperative (-0.015 ± 0.04 vs. 0.01 ± 0.020; P = 0.01). Regarding contrast sensitivity, UVACS and BCVACS were significantly better in ICB00 as compared with ZCB00 at 6 weeks and 3 months postoperative (P < 0.05). The defocus curves showed that the mean visual acuity of the ICB00 group was significantly better than that of the ZCB00 group at between - 0.5 D and - 2.50 D of defocus.

CONCLUSION

In patients undergoing cataract surgery, Eyhance ICB00 provided better intermediate vision as compared with ZCB00.

2022 Glenn A. Fry Award lecture: Enhancing clinical assessment for improved ophthalmic management

ABSTRACT

Detailed clinical assessment is critical to allow sensitive evaluation of the eye and its management. As technology advances, these assessment techniques can be adapted and refined to improve the detection of pathological changes of ocular tissue and their impact on visual function. Enhancements in optical medical devices including spectacle, contact, and intraocular lenses have allowed for a better understanding of the mechanism and amelioration of presbyopia and myopia control. Advancements in imaging technology have enabled improved quantification of the tear film and ocular surface, informing diagnosis and treatment strategies. Miniaturized electronics, large processing power, and in-built sensors in smartphones and tablets capacitate more portable assessment tools for clinicians, facilitate self-monitoring and treatment compliance, and aid communication with patients. This article gives an overview of how technology has been used in many areas of eye care to improve assessments and treatment and provides a snapshot of some of my studies validating and using technology to inform better evidence-based patient management.

Comparison of dynamic defocus curve on cataract patients implanting extended depth of focus and monofocal intraocular lens

BACKGROUND

The aim of the study was to compare the dynamic defocus curve on patients post-implantation of the extended depth-of-focus (EDOF) and monofocal intraocular lens (IOL).

METHODS

A total of 62 age-related cataract patients receiving phacoemulsification with implantation of TECNIS Symfony (ZXR00) or monofocal IOLs were enrolled. The binocular static and dynamic defocus curves with corrected distance visual acuity were evaluated at one month postoperatively.

RESULTS

The ZXR00 group achieved significantly better intermediate (P = 0.044) and near (P = 0.017) visual acuity (VA) than the monofocal group. Two groups had similar uncorrected and corrected distance VA (P > 0.05, respectively). The dynamic defocus curve revealed a smoother decline from 0.0 D to - 2.0 D in the ZXR00 group. Defocused dynamic VA in the ZXR00 group was significantly better (P < 0.05) except at 0.0 D (P = 0.724) and - 0.5 D (P = 0.176). The area under the curve (P = 0.002) and corrected dynamic vision accommodation (P = 0.001) derived from the dynamic defocus curves were better in the ZXR00 group. A positive correlation was observed between defocused dynamic and static VA in both groups (P < 0.001). Multiple linear regression analysis indicated that defocused static VA and corrected dynamic vision accommodation were significant influential factors for the defocused dynamic VA from - 1.0 D to - 3.0 D (P < 0.05).

CONCLUSIONS

The EDOF IOL provided similar distance vision, better intermediate and near vision, and a better overall dynamic defocus curve than the monofocal IOL. The dynamic defocus curve may be comprehensively applied to evaluate the all-distance dynamic visual performance post-cataract surgery.

Optimising curve fitting techniques to look for standardisation of the analysis of defocus curves derived from multifocal intraocular lenses

Introduction

To establish the most appropriate curve fitting method to allow accurate comparison of defocus curves derived from intraocular lenses (IOLs).

Methods

Defocus curves were plotted in five IOL groups (monofocal, extended depth of focus, refractive bifocal, diffractive bifocal and trifocal). Polynomial curves from 2nd to 11th order and cubic splines were fitted. Goodness of fit (GOF) was assessed using five methods: least squares, coefficient of determination (R²_adj), Akaike information criteria (AIC), visual inspection and Snedecor and Cochran. Additional defocus steps at −2.25 D and −2.75 D were measured and compared to the calculated visual acuity (VA) values. Area under the defocus curve and range of focus were also compared.

Results

Goodness of fit demonstrated variable results, with more lenient methods such as R²_adj leading to overfitting and conservative methods such as AIC resulting in underfitting. Furthermore, conservative methods diminished the inflection points resulting in an underestimation of VA. Polynomial of at least 8th order was required for comparison of area methods, but overfitted the EDoF and monofocal groups; the spline curve was consistent for all IOLs and methods.

Conclusions

This study demonstrates the inherent difficulty of selecting a single polynomial function. The R² method can be used cautiously along with visual inspection to guard against overfitting. Spline curves are suitable for all IOLs, guarding against the issues of overfitting. Therefore, for analysis of the defocus profile of IOLs, the fitting of a spline curves is advocated and should be used wherever possible.

Defocus curves: Focusing on factors influencing assessment

ABSTRACT

Defocus curve assessment is used to emulate defocus over a range of distances and is a valuable tool that is used to differentiate the performance of presbyopia-correcting intraocular lenses. However, defocus curves are limited by a lack of standardization, and multiple factors can impact their generation and interpretation. This review discusses key factors that influence the assessment of defocus curves, including pupil size, level of contrast, sphere versus cylinder defocus, viewing distance, monocular versus binocular assessment, use of Snellen versus logarithm of the minimum angle of resolution charts, and diopter range and step size. There are also different methods to analyze defocus curves, including the direct comparison method, range-of-focus analysis, and area under the curve analysis, which can impact result interpretation. A good understanding of these factors and standardization of the methodology are important to ensure optimal cross-study comparisons.

Depth of field measures in pseudophakic eyes implanted with different type of presbyopia-correcting IOLS

To evaluate depth of field (DOF) provided by different presbyopia-correcting intraocular lens (IOL) designs, comparing the results obtained using different criteria for defining the defocus tolerance. A total of 150 eyes undergoing cataract surgery were enrolled and divided into 6 groups depending on the IOL implanted: AT.LISA Tri (Carl Zeiss Meditec), FineVision (PhysIOL), PanOptix (Alcon Laboratories), Tecnis Symfony (Johnson & Johnson Vision), Miniwell (SIFI MedTech) and Tecnis Synergy (Johnson & Johnson Vision). Subjective DOF was obtained from defocus curves with absolute and relative criteria of tolerance of 0.1 logMAR. Aberrometry was also measured and the visual strehl optical transference function (VSOTF) with percentage of degradation of 90%, 80% and 60% was used to quantify objectively the DOF. Tecnis Symfony, Tecnis Synergy and Panoptix IOL groups showed better subjective and objective DOF compared to the rest of IOL groups, being these differences statistically significant differences (p < 0.001). Comparison between subjective and objective DOF showed that subjective measures were higher for all IOLs, being also these differences statistically significant for all groups (p < 0.001). A moderate significant correlation was found between absolute subjective criteria and VSOTF60% (r = 0.73, p < 0.05). Objective and subjective measures of DOF are not comparable due to differences in methodologies and criterions to define the level of degradation tolerance. Nevertheless, both objective and subjective measures showed a trend to a greater DOF for Tecnis Symfony and Tecnis Synergy IOLs compared to most of trifocal diffractive designs, with the exception of PanOptix.

Comparison of an aspheric monofocal intraocular lens with the new generation monofocal lens using defocus curve

Purpose:

The aim of this study was to compare the visual outcomes of two monofocal intraocular lenses (IOLs), with emphasis on the defocus curve.

Methods:

A total of 116 consecutive eyes with cataract, undergoing phacoemulsification with IOL implantation were included in the observational case series, and divided into two groups. 71 eyes were implanted with Tecnis Eyhance and 45 with Tecnis 1 monofocal IOL. Eyes with ocular comorbidities, previous ocular surgeries and corneal astigmatism >1 Diopters (D) were excluded from the study. Complete ophthalmic evaluation including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), uncorrected intermediate visual acuity (UIVA), corrected intermediate visual acuity (CIVA), uncorrected visual acuity (UNVA), corrected near visual acuity (CNVA) was noted and defocus levels ranging from - 4.00 D to + 1.00 D were plotted postoperatively in both groups.

Results:

Uncorrected intermediate visual acuity (UIVA) and uncorrected near visual acuity (UNVA) was significantly better in Tecnis Eyhance group compared to Tecnis 1 monofocal. Both the IOLs have similar performance for distance vision but visual acuity at intermediate and near is significantly better with Tecnis Eyhance compared to Tecnis 1 piece IOL.

Conclusion:

Tecnis Eyhance IOL with its better defocus curve, not only provides good distance, but intermediate vision as well. With significantly better visual acuity across the range of near and intermediate vision, Tecnis Eyhance IOL can prove to be a viable and reasonable option for patients who are more dependent on intermediate vision in daily activities.

Factors Influencing Pseudo-Accommodation-The Difference between Subjectively Reported Range of Clear Focus and Objectively Measured Accommodation Range

The key determinants of the range of clear focus in pre-presbyopes and their relative contributions to the difference between subjective range of focus and objective accommodation assessments have not been previously quantified. Fifty participants (aged 33.0 ± 6.4 years) underwent simultaneous monocular subjective (visual acuity measured with an electronic test-chart) and objective (dynamic accommodation measured with an Aston open-field aberrometer) defocus curve testing for lenses between +2.00 to −10.00 DS in +0.50 DS steps in a randomized order. Pupil diameter and ocular aberrations (converted to visual metrics normalized for pupil size) at each level of blur were measured. The difference between objective range over which the power of the crystalline lens changes and the subjective range of clear focus was quantified and the results modelled using pupil size, refractive error, tolerance to blur, and ocular aberrations. The subjective range of clear focus was principally accounted for by age (46.4%) and pupil size (19.3%). The objectively assessed accommodative range was also principally accounted for by age (27.6%) and pupil size (15.4%). Over one-quarter (26.0%) of the difference between objective accommodation and subjective range of clear focus was accounted for by age (14.0%) and spherical aberration at maximum accommodation (12.0%). There was no significant change in the objective accommodative response (F = 1.426, p = 0.229) or pupil size (F = 0.799, p = 0.554) of participants for levels of defocus above their amplitude of accommodation. Pre-presbyopes benefit from an increased subjective range of clear vision beyond their objective accommodation due in part to neural factors, resulting in a measured depth-of-focus of, on average, 1.0 D.

Fast Measure of Visual Acuity and Contrast Sensitivity Defocus Curves with an iPad Application

Objective:

To evaluate the repeatability of the fast measurement of the visual acuity (VADC) and contrast sensitivity (CSDC) defocus curves with a new test as well as the agreement of measurements at far distance obtained with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and the ClinicCSF test for measuring Contrast Sensitivity Function (CSF).

Method:

Records from fifty-nine subjects implanted with Multifocal Intraocular Lenses (MIOLs) were retrieved from our database. VADC and CSDC were measured from +1.00 D to -4.00 D in 0.50 D steps. The agreement with the ETDRS and the CSF at far distance was assessed in comparison to the 0 D location of the VADC and the CSDC, respectively. The repeatability was evaluated in 34 subjects who consecutively repeated two measures.

Results:

Median Visual Acuity (VA) was -0.1 logMAR with the VADC at 0 D of defocus and 0 logMAR with the ETDRS (p>0.05). A total of 45.8% of eyes showed no differences between both tests and the difference was less than one line of VA in 96.6% of the eyes. The intrasubject repeatability was under one line of VA along all the defocus curve except for positive defocus levels. The CSDC showed the best agreement with the CSF for 18 cycles per degree. The CSDC was less repeatable than VADC. Mean time spent on completing the VADC and CSDC was 7.81 and 7.98 minutes, respectively.

Conclusion:

The VADC showed good agreement with the ETDRS and good repeatability despite the short testing time. In contrast, poorer repeatability was found for CSDC. Our method would facilitate the inclusion of VADC in clinical practice as it is a fast test, being also the first one including the measure of CSDC.

Presbyopia: Effectiveness of correction strategies

Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations, due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states "presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements". Strategies for correcting presbyopia include separate optical devices located in front of the visual system (reading glasses) or a change in the direction of gaze to view through optical zones of different optical powers (bifocal, trifocal or progressive addition spectacle lenses), monovision (with contact lenses, intraocular lenses, laser refractive surgery and corneal collagen shrinkage), simultaneous images (with contact lenses, intraocular lenses and corneal inlays), pinhole depth of focus expansion (with intraocular lenses, corneal inlays and pharmaceuticals), crystalline lens softening (with lasers or pharmaceuticals) or restored dynamics (with 'accommodating' intraocular lenses, scleral expansion techniques and ciliary muscle electrostimulation); these strategies may be applied differently to the two eyes to optimise the range of clear focus for an individual's task requirements and minimise adverse visual effects. However, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is given on presbyopic correction evaluation techniques.

Clinical application of accommodating intraocular lens

The present review describes recent advances in application of accommodating intraocular lenses (AIOLs). Standard monofocal intraocular lenses (MIOLs) only correct distance vision, while AIOLs are designed to allow both good distance vision and near vision, which is achieved through the contraction and relaxation of ciliary muscles by providing transformation of the axial movement or curvature of the lens. Thus, AIOLs may be a better choice for those patients who demand a higher level of visual performance. Since techniques to analyze the performance of AIOLs have not been standardized, and there is a variety of both subjective and objective methods, it is hard to measure the performance of these intraocular lenses. By evaluating advantages and disadvantages of various AIOLs, and introducing techniques for measurement the performance postoperative, this paper can provide some relative information on choosing the type of AIOLs in the clinic.

The clinical depth of field achievable with trifocal and monofocal intraocular lenses: theoretical considerations and proof of concept clinical results

BACKGROUND

To estimate the depth of field (DOF) achievable with multi-and monofocal intraocular lenses (IOLs) and compare with actual measurements of DOF in cases implanted with a trifocal IOL and biconvex monofocal IOL METHODS: I) Computer simulations were produced to describe the relationship between DOF, pupil size, preoperative ametropia, and retinal blur tolerance limit for a model eye implanted with either multi- or monofocal IOLs. II) Monocular DOF and pupil size were measured under distance viewing conditions between 3 and 6 months postoperative following uneventful cataract surgery. Cases were implanted with either i) trifocal aspheric IOL (n = 36), or ii) biconvex aspheric monofocal IOL (n = 26). DOF was also measured at 0.33 m in cases implanted with i).

RESULTS

Simulations revealed significant associations between DOF, pupil size, and retinal blur tolerance limit. The mean (±SD) DOF & pupil sizes were at distance for i)  above 2.59D (0.68) & 3.54 mm (0.377), and for ii) above 1.67D (0.51) & 2.90 mm (0.351), and for i) above 3.16D (0.46) at near. The difference between groups were significant for DOF and pupil size at distance (p < 0.001). DOF was significantly greater at near compared with distance in i) above (p < 0.001). For a pupil size of 3 mm, the simulations produce similar DOF values when the tolerance limit of retinal blur is 10 μ.

CONCLUSIONS

The DOF was significantly better after implanting the trifocal IOL compared with the monofocal IOL, and DOF is increased under near viewing conditions. The clinical results are similar to calculated DOF values when the tolerance limit of retinal blur is 10 μ.

Exploring the optimum step size for defocus curves

PURPOSE

To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified.

SETTING

Midland Eye, Solihull, United Kingdom.

DESIGN

Evaluation of a technique.

METHODS

Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and -5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear-focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add-specific profile (ie, distance, half the near add, and the full near-add powers).

RESULTS

A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear-focus or area metrics for each of the multifocal designs examined when the defocus-curve step size was increased (P<.05).

CONCLUSION

Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Objective accommodation measurements in pseudophakic subjects using an autorefractor and an aberrometer

PURPOSE

To compare objective measures of accommodation with the WR-5100K autorefractor and iTrace aberrometer to subjective push-down and defocus tests in normal phakic subjects and pseudophakic subjects with standard monofocal intraocular lenses (IOLs).

SETTING

University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

The push-down test and defocus curves were used to stimulate and measure accommodation subjectively in pseudophakic subjects. For objective testing, a near target was pushed up and refraction measured objectively. For comparison, the same objective measurements were performed in phakic subjects. Calibration tests were performed with soft contact lenses in phakic subjects with varying refractive error and in pseudophakic subjects.

RESULTS

Fifteen phakic subjects (mean age 28.9 years+/-5.52 [SD]) and 10 pseudophakic subjects (mean age 66.2+/-11.23 years) participated. Subjectively measured accommodative amplitude in the pseudophakic group was 3.28+/-1.11 diopters (D) in the right eye and 3.64+/-1.38 D in the left eye. Defocus curves in the pseudophakic group had a range of 2.00 D for distance-corrected visual acuity of 20/40 or better. Objective measurements in the pseudophakic group were 0.11+/-0.50 D with the autorefractor and 0.10+/-0.47 D with the aberrometer. Contact lens calibrations showed good agreement with the 1:1 line.

CONCLUSIONS

The subjective tests overestimated accommodative amplitude relative to the objective measures. The autorefractor and aberrometer were accurate, reliable, and appropriate for objective accommodation measurements in pseudophakes. Objective accommodation measurements such as these can be used to evaluate the performance of accommodating IOLs.