Brightness acuity test and outdoor visual acuity in cataract patients

Subjective Straylight Index: A Visual Test for Retinal Contrast Assessment as a Function of Veiling Glare

Spatial aspects of visual performance are usually evaluated through visual acuity charts and contrast sensitivity (CS) tests. CS tests are generated by vanishing the contrast level of the visual charts. However, the quality of retinal images can be affected by both ocular aberrations and scattering effects and none of those factors are incorporated as parameters in visual tests in clinical practice. We propose a new computational methodology to generate visual acuity charts affected by ocular scattering effects. The generation of glare effects on the visual tests is reached by combining an ocular straylight meter methodology with the Commission Internationale de l'Eclairage's (CIE) general disability glare formula. A new function for retinal contrast assessment is proposed, the subjective straylight function (SSF), which provides the maximum tolerance to the perception of straylight in an observed visual acuity test. Once the SSF is obtained, the subjective straylight index (SSI) is defined as the area under the SSF curve. Results report the normal values of the SSI in a population of 30 young healthy subjects (19 ± 1 years old), a peak centered at SSI = 0.46 of a normal distribution was found. SSI was also evaluated as a function of both spatial and temporal aspects of vision. Ocular wavefront measures revealed a statistical correlation of the SSI with defocus and trefoil terms. In addition, the time recovery (TR) after induced total disability glare and the SSI were related; in particular, the higher the RT, the greater the SSI value for high- and mid-contrast levels of the visual test. No relationships were found for low contrast visual targets. To conclude, a new computational method for retinal contrast assessment as a function of ocular straylight was proposed as a complementary subjective test for visual function performance.

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.

Quantification of the Dynamic Visual Acuity Space at Real-World Luminances and Contrasts: The VA-CAL Test

Purpose

Best-corrected visual acuity (BCVA) is assessed at a single standardized luminance with maximum optotype contrast, not reflecting the constantly changing daily-life viewing conditions. For a more realistic estimation of visual performance at varying object contrasts (Cs) and ambient luminances (ALs), we developed a new VA test, VA-CAL.

Methods

Landolt-C-rings between 18% and 95% Weber contrast, were presented at 1 m distance (8 Alternative Forced Choice) on a 5.7 degree field in the middle of a frosted glass screen (66 degrees), back-lit by 3060 LEDs (generating ambient luminances between 0-10,000 cd/m²). Visual acuity (VA) was measured in 14 normally sighted participants twice for 8 conditions of ambient luminance and 6 conditions of contrast using a QUEST staircase procedure.

Results

VA improved continuously up to an ambient luminance of 3000 to 5000 cd/m² (best mean VA ± SEM: -0.47 ± 0.03 logMAR at C = 95%, AL = 3000 cd/m²), followed by a decline of VA at higher luminances with good test-retest variability. As expected, reduced contrast leads to a lower VA (worst mean VA ± SEM: -0.03 ± 0.03 logMAR at C = 18%, AL = 0 cd/m²). A 3D plot of these data shows the VA space (VAS) extending between the contrast and luminance axes, which describes the dynamics of VA continuously changing under varying everyday life conditions.

Conclusions

VA-CAL, an automated device and procedure, allows for simultaneous evaluation of VA at various contrast-luminance combinations, thus providing a more comprehensive assessment of spatial vision problems not seen with standard BCVA tests.

Translational Relevance

The new BCVA test VA-CAL incorporates a range of everyday contrast and ambient luminance conditions for a more realistic description of visual performance.

Assessment of Visual Function and Performance in Paralympic Judo for Athletes with Vision Impairment

SIGNIFICANCE

Paralympic judo currently requires all athletes to compete against each other in one class irrespective of their level of vision impairment (VI). Recent evidence suggests that multiple classes are required to enhance fairness, yet it remains unclear how many classes are necessary and what vision tests should be used to define those classes.

PURPOSE

The aim of this study was to quantify the relationship between vision and performance in judo for individuals with VI. The results were expected to inform the development of evidence-based criteria to structure Paralympic judo competition.

METHODS

The visual function of 53 elite VI judokas was assessed using a test battery that included tests of visual acuity (VA), contrast sensitivity, light sensitivity, depth perception, motion perception, visual search, and central visual field. Performance was assessed by measuring the ratio of fights won across all competitions the participants took part in in the 2 years before and after vision testing. Pearson correlation coefficients and decision tree analyses were used to determine the relationship between vision and performance. Partial correlations were also conducted to determine the unique ability of each measure of visual function to predict judo performance.

RESULTS

Visual acuity was the best predictor of judo performance and remained the only visual function related to performance when controlling for correlations between VA and other visual functions. Decision tree analyses suggested to split athletes into two groups for more legitimate competition, using a cutoff point around 2.6 logMAR. Within each of the two resulting subgroups, no correlations remained between any of the visual functions and performance.

CONCLUSIONS

The results of this study suggest that VI judo competition should be split into separate categories for partially sighted and functionally blind athletes. The inclusion of visual functions in addition to VA does not improve the ability to predict performance in VI judo.

Wide-field direct ocular straylight meter

The impact of the intraocular straylight (IOS) on the visual performance and retinal imaging is still a challenging topic. Direct optical methods to measure IOS avoid psychophysical approaches and interaction with the patient. In this work, we developed an optical instrument providing direct imaging measurement of IOS based on the double-pass technology. The system was tested in an artificial eye IOS model constructed with holographic diffusers and validated with theoretical simulations.

International Paralympic Committee (IPC) and International Blind Sports Federation (IBSA) Joint Position Stand on the Sport-Specific Classification of Athletes with Vision Impairment

Classification is a defining characteristic of para-sports whereby eligible athletes are allocated a sport class to compete against others with similar activity limitations. To account for the unique characteristics of each sport, para-sports should develop their own classification system using evidence that demonstrates the impact of impairment on performance in that sport. Although the move towards sport-specific classification has progressed in sports for athletes with physical and intellectual impairments, sports for athletes with vision impairment (VI) continue to use the same three classes irrespective of the sport, with classes delineated by legal definitions of low vision and blindness. The aim of this joint International Paralympic Committee/International Blind Sports Federation (IPC/IBSA) Position Stand is to provide guidance for how evidence-based sport-specific classification should be achieved in VI sports. It does so by outlining three conceptual research models (correlation, simulation, and component analysis) that can be used to establish both the minimum impairment required to compete plus the appropriate number of sport classes and their inclusion criteria. The present evaluation of vision relies on measures of visual acuity and field, but new criteria may require a sport-specific combination of additional measures of visual function (e.g. contrast, motion, and light sensitivity) to better account for the impact of VI on sport performance. Moreover, the test procedures used during athlete evaluation (e.g. whether to evaluate both eyes individually or together) should be chosen to better represent the habitual viewing situation experienced in that sport. The development of sport-specific criteria should enhance the legitimacy of competition and encourage increased grassroots participation in VI sports.

Double-pass technique and compensation-comparison method in eyes with cataract

PURPOSE

To clinically assess the objective scatter index (OSI) obtained from double-pass images and the log(s) parameter measured with the direct compensation-comparison psychophysical technique in eyes with cataract.

SETTING

Ophthalmology Service, Terrassa Hospital, Barcelona, Spain.

DESIGN

Prospective observational case series.

METHODS

The analysis comprised eyes diagnosed with nuclear, cortical, or posterior subcapsular cataracts and healthy eyes (control group). Patient examinations included assessment of the manifest subjective refraction, corrected distance visual acuity, contrast sensitivity, and cataract grade using the Lens Opacities Classification System III (LOCS III) score. The protocol also included the straylight (log[s]) measured by the C-Quant device, measurement of the objective optical quality (Strehl ratio and modulation transfer function cutoff frequency), and the OSI (HD Analyzer).

RESULTS

Significant correlations with LOCS III classification were found in terms of log(s) and OSI, although they were slightly stronger with OSI for all cataract types, which could be attributable to higher-order aberrations. The OSI and log(s) shared approximately 44% of the scattering estimation and to coincide on the visual function decline with scattering for the 3 cataract types evaluated. Limits to discriminate between healthy and cataractous eyes and sensitivity and specificity values were 1.15 (sensitivity 91%, specificity 100%) for log(s) and 1.18 (sensitivity 89%, specificity 100%) for OSI (P < .05).

CONCLUSIONS

Both instruments provide complementary information to diagnose cataracts and follow patients. Although backscattered light from deeper retinal layers can have an effect on OSI, the double-pass image provides information to grade different types of cataract when assessing cataractous eyes for treatment.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Epithelium-off corneal collagen cross-linking versus transepithelial cross-linking for pediatric keratoconus

PURPOSE

To compare efficiency and safety of epithelium-off corneal cross-linking (CXL) and transepithelial cross-linking (TE-CXL) in pediatric patients with progressive keratoconus.

METHODS

Uncorrected and corrected visual acuity, corneal topography and pachymetry (Pentacam; Oculus Pentacam), and in vivo confocal microscopy (HRT II, Rostock Cornea Module, Heidelberg Engineering, Heidelberg, Germany) were evaluated at baseline and at 3, 6, and 12 months.

RESULTS

In the epithelium-off CXL group (19 patients, 23 eyes; mean age, 14.75 ± 2.1 years), a significant improvement at month 12 was present for Kmax [-1.11 diopters (D), P = 0.01], Kmin (-3.2 D, P = 0.001), mean K (-1.47 D, P = 0.01), surface asymmetry index (-0.64 D, P = 0.001), inferior-superior symmetry index (-0.54 D, P = 0.01), index of height asymmetry (-2.97, P = 0.03), and anterior elevation at the thinnest location (-2.82 D, P = 0.01) and at the apex (-2.27 D, P = 0.01). Postoperative corneal edema lasted 3 months in 16 eyes (69.5%) and more than 6 months in 2 eyes (8.7%). In the TE-CXL group (10 patients, 14 eyes; mean age, 15 ± 4.2 years), a significant improvement at month 12 was present for Kmax (-1.14 D, P = 0.02), Kmin (-2.04 D, P = 0.01), mean K (-1.63 D, P = 0.01), surface asymmetry index (-0.86 D, P = 0.001), inferior-superior symmetry index (-0.55 D, P = 0.001), index of height asymmetry (-2.95, P = 0.01), and anterior elevation at the thinnest location (-2.96 D, P = 0.01) and at the apex (-2.19 D, P = 0.01). No postoperative corneal edema after TE-CXL was observed. Changes at month 12 from baseline were not significantly different between the 2 groups (P > 0.05). TE-CXE was significantly less painful than epithelium-off CXL.

CONCLUSIONS

In pediatric patients with progressive keratoconus, TE-CXL was less painful, provided similar effectiveness and fewer complications than epithelium-off CXL at 12-month follow-up.

History of ocular straylight measurement: A review

The earliest studies on 'disability glare' date from the early 20(th) century. The condition was defined as the negative effect on visual function of a bright light located at some distance in the visual field. It was found that for larger angles (>1 degree) the functional effect corresponded precisely to the effect of a light with a luminosity equal to that of the light that is perceived spreading around such a bright source. This perceived spreading of light was called straylight and by international standard disability glare was defined as identical to straylight. The phenomenon was recognized in the ophthalmological community as an important aspect of the quality of vision and attempts were made to design instruments to measure it. This must not be confused with instruments that assess light spreading over small distances (<1 degree), as originating from (higher order) aberrations and defocus. In recent years a new instrument has gained acceptance (C-Quant) for objective and controllable assessment of straylight in the clinical setting. This overview provides a sketch of the historical development of straylight measurement, as well as the results of studies on the origins of straylight (or disability glare) in the normal eye, and on findings on cataract (surgery) and corneal conditions.

Comparison between an objective and a psychophysical method for the evaluation of intraocular light scattering

In this study we present the comparison of the performance of two systems to measure intraocular scattering. Measurements were made by using a psychophysical system based on a brightness comparison method that provides a glare index and a physical system based on the double-pass technique, which gives an objective scatter index by measuring the optical quality of the eye. Three external diffuser filters that simulated different grades of intraocular scattering were used in subjects with normal vision. The two measured indexes showed a graded rise with increasing level of scattering. The discrimination ability obtained for both systems showed that they were able to distinguish among conditions ranging from normal to early cataracts.

Optical quality after myopic photorefractive keratectomy and laser in situ keratomileusis: comparison using a double-pass system

PURPOSE

To use a double-pass system to compare the optical quality after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for mild to moderate myopia.

SETTING

Universitat Politècnica de Catalunya, Terrassa, Barcelona Institute of Ocular Microsurgery, Barcelona, Spain.

DESIGN

Comparative case series.

METHODS

Optical quality was assessed with a clinical double-pass system preoperatively and 3 months after PRK or LASIK. The modulation transfer function (MTF), retinal image quality parameters (MTF cutoff frequency, Strehl ratio), and intraocular scattering (objective scatter index [OSI]) were calculated.

RESULTS

This study evaluated 34 eyes that had PRK and 55 eyes that had LASIK. Both PRK and LASIK had a statistically significant impact on retinal image quality, although no significant differences between the techniques were observed. The MTF at 30 cycles per degree decreased by a factor of 1.50 in the PRK group and by a factor of 1.32 in the LASIK group. The MTF cutoff frequency decreased by a factor of 1.04 in the PRK group and by a factor of 1.06 in the LASIK group. The Strehl ratio decreased by a factor of 1.10 and 1.07, respectively. Photorefractive keratectomy and LASIK increased the objective scatter index by factors of 1.48 and 1.57, respectively. Significant correlations between the preoperative refraction and the OSI were found.

CONCLUSIONS

Retinal image quality was similarly reduced with PRK and LASIK, with no significant differences between the 2 methods. Some PRK patients had a residual refractive error that might have been related to corneal-wound healing still present 3 months postoperatively.

Effects on vision with glare after correction of monochromatic wavefront aberrations

PURPOSE

To investigate effects of optical aberration correction on vision with glare.

METHODS

Correction of aberrations up to the 6th Zernike order (closed-loop correction) was compared with conventional spectacle correction in 42 healthy eyes. To create these corrections, an adaptive optics system including a thin-film transistor (TFT) monitor for displaying optotypes with additional glare sources was used. Employing both corrections, visual acuity and contrast sensitivity (CS) were tested alternately with and without glare. Disability glare was computed as the difference between log CS without and with glare. Individuals were also asked to rate subjectively the quality of three images displayed on the TFT monitor.

RESULTS

Significant improvements of CS without and with glare were found with the closed-loop correction (0.147 and 0.198 log CS, respectively), whereas no significant difference in visual acuity was found in either correction. Correlations were determined between reduction of total root-mean-square error and increase of CS with glare (Pearson correlation coefficient r=0.42) and decrease of disability glare (r=-0.33). Visual acuity was correlated with the visual Strehl ratio based on the optical transfer function (r=0.46). Subjective comparison of the images showed improvements more clearly. Depending on the image, in 57% to 78% of the eyes, closed-loop correction was rated better than spectacle correction. The subjective glare effect was reduced as well.

CONCLUSIONS

Investigation of vision with glare seems to be a reasonable additional test to evaluate the visual outcome of a customized correction.

An objective scatter index based on double-pass retinal images of a point source to classify cataracts

Purpose

To propose a new objective scatter index (OSI) based in the analysis of double-pass images of a point source to rank and classify cataract patients. This classification scheme is compared with a current subjective system.

Methods

We selected a population including a group of normal young eyes as control and patients diagnosed with cataract (grades NO2, NO3 and NO4) according to the Lens Opacities Classification System (LOCS III). For each eye, we recorded double-pass retinal images of a point source. In each patient, we determined an objective scatter index (OSI) as the ratio of the intensity at an eccentric location in the image and the central part. This index provides information on the relevant forward scatter affecting vision. Since the double-pass retinal images are affected by both ocular aberrations and intraocular scattering, an analysis was performed to show the ranges of contributions of aberrations to the OSI.

Results

We used the OSI values to classify each eye according to the degree of scatter. The young normal eyes of the control group had OSI values below 1, while the OSI for subjects in LOCS grade II were around 1 to 2. The use of the objective index showed some of the weakness of subjective classification schemes. In particular, several subjects initially classified independently as grade NO2 or NO3 had similar OSI values, and in some cases even higher than subjects classified as grade NO4. A new classification scheme based in OSI is proposed.

Conclusions

We introduced an objective index based in the analysis of double-pass retinal images to classify cataract patients. The method is robust and fully based in objective measurements; i.e., not depending on subjective decisions. This procedure could be used in combination with standard current methods to improve cataract patient surgery scheduling.

Comparing the 1CU accommodative, multifocal, and monofocal intraocular lenses: a randomized trial

OBJECTIVE

To compare the binocular near vision performance in patients implanted with the 1CU accommodating intraocular lens (IOL) with a multifocal and monofocal IOL.

DESIGN

Prospective, randomized, double-masked clinical trial.

PARTICIPANTS

Ninety patients presenting for cataract surgery to the Department of Ophthalmology, Hillingdon Hospital were randomized to receive the 1CU accommodative IOL, a multifocal IOL, or a monofocal IOL (control group).

METHODS

Patients underwent bilateral sequential phacoemulsification with implantation of 1 of the 3 IOL types and were assessed at 3 and 18 months after second-eye surgery.

MAIN OUTCOME MEASURES

Logarithm of the minimum angle of resolution distance and near visual acuities (VAs) (unaided and distance corrected), contrast sensitivity, and accommodative amplitude (near point and defocusing) were measured at 3 and 18 months. Reading speed was assessed at 18 months, and glare symptoms and spectacle independence were compared using a standardized questionnaire.

RESULTS

Mean unaided and distance-corrected binocular near VAs were similar in the 1CU and multifocal and were significantly higher than the control group's (P<0.02). There was no significant difference in reading speed between any of the groups, but critical print sizes were similar in the 1CU and multifocal groups and significantly better than the control group's (P = 0.02). The accommodative range was highest in the multifocal group and lowest in the control group, and there was no significant difference between the 1CU and control groups for defocus or near point at 18 months. Of the 1CU group and control group, 71.4% and 63.2%, respectively, experienced no glare at 18 months, compared with only 25% of the multifocal group (P = 0.01). Of the 1CU group and multifocal group, 19% and 27.3%, respectively, were completely spectacle independent at 18 months; none of the control group was (P = 0.05).

CONCLUSIONS

The 1CU accommodating IOL provides improved near vision compared with a monofocal IOL. There is a discrepancy between the near function and accommodative amplitude measured in the 1CU. The multifocal provides excellent near acuity, but photopic phenomena remain a problem inherent in the lens design.

Glare susceptibility test results correlate with temporal safety margin when executing turns across approaching vehicles in simulated low-sun conditions

The purpose of this study was to compare the results of a laboratory glare susceptibility test with the execution of turns at an intersection (turns that required the driver to cross a lane containing approaching traffic). We measured glare susceptibility by means of low and high-contrast letter charts with and without a glare source. Driving performance in the absence and presence of simulated low sun was assessed using a simulator. In particular, we measured the difference between the time taken to complete a turn across the path of an approaching vehicle and the time to collision (TTC) with the approaching vehicle (the safety margin). The presence of glare resulted in a significant reduction in the safety margin used by drivers (by 0.65 s on average) and the mean number of collisions was significantly higher in the glare conditions than in the non-glare conditions. The effect of glare was larger for low-contrast than for high-contrast oncoming vehicles. Older drivers (45-60 years) had a significantly greater reduction in safety margin than younger drivers (19-29 years), though there was a large inter-individual variability in both age groups. We suggest that the reduction in retinal image contrast caused by low-sun caused drivers to overestimate the TTC with approaching vehicles.

Principles of disability glare measurement: an ophthalmological perspective

Disability glare describes the loss of retinal image contrast as a result of intraocular light scatter, or straylight. It has increasingly important modern implications such as with cataract and refractive surgery or high-intensity lighting. However, its measurement has proven difficult despite many varying approaches. This article aims to explain the principles and problems associated with glare testing that are important for assessment and use of glare measures. After defining disability glare, this article discusses the importance of its measurement to current clinical practice. It explains the principles and mechanisms that underlie disability glare and its measurement. Finally, some examples of available glare tests are described to illustrate the principles discussed.

Efficacy of Measuring Visual Performance of LASIK Patients under Photopic and Mesopic Conditions

Introduction: The aim of the study was to compare the visual performance of LASIK eyes measured using high-contrast logMAR letter charts under bright (photopic) and dim (mesopic) conditions. Materials and Methods: A total of 46 subjects (35 ± 8 years of age) undergoing LASIK procedures were recruited for the study. The best spectacle-corrected visual acuity (BSCVA) of each subject was measured using the high-contrast ETDRS logMAR chart under photopic and mesopic conditions at 3 visits: preoperative (Pre), 1 month postoperative (Post1) and 3 months postoperative (Post3). The differences in logMAR scores for the right eyes only were analysed for the Pre-Post1 (n = 46), Pre-Post3 (n = 18) and Post1-Post3 (n = 16) comparisons. Results: The logMAR scores of subjects were worse at the 1-month postoperative visit than preoperatively, and improvement in visual performance was seen at the 3-month postoperative visit. These changes in visual performance became more evident under mesopic conditions. The means and standard errors of the differences in logMAR scores for the Pre-Post3 (0.097 ± 0.020) were slightly larger than those of the Pre-Post1 (-0.067 ± 0.019) and Post1-Post3 (0.031 ± 0.012) comparisons. Under mesopic conditions, the visual performance of the subjects was statistically significant for the 3 comparisons, but not under photopic conditions. Conclusion: High-contrast logMAR chart performed under mesopic conditions has the potential to replace visual acuity measured under photopic conditions in providing more reliable representation of postoperative visual outcomes of LASIK eyes. Eye doctors should consider performing this vision test routinely to gauge the success of LASIK surgery. Key words: Contrast sensitivity, logMAR chart, Visual acuity

Rapid, objective detection of cataract-induced blur using a bull's eye photodetector

PURPOSE

To determine whether optical aberrations caused by cataract can be detected and quantified objectively using a newly described focus detection system (FDS).

SETTING

The Wilmer Opthalmological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

METHODS

The FDS uses a bull's eye photodetector to measure the double-pass blur produced from a point source of light. To determine the range and level of focus, signals are measured with a series of trial lenses in the light path selected to span the point of best focus to generate focus curves. The best corrected visual acuity (BCVA), refractive error, lens photograph grades, and FDS signals were obtained in 18 patients scheduled to have cataract surgery. The tests were repeated 6 weeks after surgery.

RESULTS

The mean FDS outcome measures improved after cataract surgery, with increased peak height (P=.001) and decreased peak width (P=.001). Improvement in signal strength (integral of signal within +/-1.5 diopters of the point of best focus) strongly correlated with improvement in peak height (R(2)=.88, P<.0001) and photographic cataract grade (R(2)=.72, P<.0001). The mean BCVA improved from 20/50 to 20/26 (P<.0001). The improvement in BCVA correlated more closely with FDS signal strength (R(2)=.44, P=.001) than with cataract grade (R(2)=.25, P=.06).

CONCLUSIONS

Improvement in FDS outcome measures correlated with cataract severity and improvement in visual acuity. This objective approach may be useful in long-term studies of cataract progression.

An analysis of an older driver evaluation program

OBJECTIVES

To identify elements of an older driver evaluation program that predict driving performance in older adults.

SETTING

Outpatient medical clinic in an academic medical center.

DESIGN

A retrospective analysis.

PARTICIPANTS

Six hundred sixty-four older adults who were referred to an older driver evaluation program.

MEASUREMENTS

A physician trained in geriatric medicine and a clinical geriatric nurse specialist oversaw an experienced driving evaluator and an occupational therapist who conducted assessments of older persons' functional status; reaction time; driving skills; and cognitive, hearing, and vision abilities. Self-report data along with a medical history submitted by patients' primary care physicians supplemented the clinical assessments.

RESULTS

A multinomial logistic regression revealed that the Mini-Mental State Examination (MMSE), cues needed with the Trail Making Test, Part B, grip strength, and an interaction effect between the MMSE and reaction time constituted the most parsimonious model for predicting on-the-road performance. A receiver operating characteristic analysis indicated that this index had good sensitivity but low specificity. A binomial regression comparing imperfect and perfect drivers demonstrated the significance of the Traffic Sign and Visual Perception tests.

CONCLUSION

Clinicians should employ a multilevel screening process that includes initial cognitive tests, such as the MMSE and the Trail Making Test, Part B, although more studies of driving evaluation programs in medical settings that include random samples of older drivers are needed.

Impact of cataract surgery on self-reported visual difficulties: comparison with a no-surgery reference group

PURPOSE

To examine the impact of cataract surgery on older adults' self-reported visual difficulties and compare them with those of patients with cataract who declined surgery over the same period.

SETTING

Twelve area practices.

METHODS

This was a consecutive chart review over a 6-month period. Primary inclusion criteria were 55 years or older, cataract in 1 or both eyes with 20/40 visual acuity or worse (best corrected, distance), and no previous cataract surgery in either eye. The Activities of Daily Vision Scale (ADVS) and visual acuity, contrast sensitivity, and disability glare tests were administered at baseline and at a 1-year follow-up visit.

RESULTS

This study comprised 245 patients, 156 of whom elected to have cataract surgery and 89 of whom declined. Those electing surgery were more likely to be white, female, and have worse visual acuity and no ocular comorbidities. At baseline, ADVS subscale scores ranged from 53 to 76 in the surgery group and from 72 to 89 in the no-surgery group. In the surgery group, subscale scores improved by 15 to 21 points on average at the 1-year follow-up; scores were unchanged or worse in the no-surgery group over this period. This difference between the groups remained statistically significant after adjustment for group baseline differences in demographics, vision, and ADVS score. In the surgery group, visual acuity improvement in the first eye was an independent predictor of increases in the ADVS overall score and night driving and glare disability subscales; contrast sensitivity was an independent predictor of improvement in the night driving subscale. A reduction in disability glare in the second eye was independently linked to increases in the overall ADVS score and the night driving, near vision, and glare disability subscales.

CONCLUSIONS

Baseline findings suggest that cataract patients who have surgery have more difficulty in visual tasks than those who decline surgery. After surgery, patients reported less difficulty with visual tasks. In the no-surgery group, no change was reported. Improvements in visual acuity and contrast sensitivity and reductions in disability glare after surgery were independently linked to improvements in ADVS scores.

Image analysis and glare sensitivity in human age-related cataracts

BACKGROUND

A new glare disability test and a diagnostic instrument, the Halometer, were proposed for measuring intraocular light scattering in the presence of human cataracts. The objectives of this work were to introduce new methods of computer-generated analysis of lens images and a glare disability test to validate the use of two new tests to measure the severity of cataract and to document and quantify changes in lens clarity at diagnosis in a group of patients with age-related cataract with minimal to advanced opacities.

METHODS

The authors followed 28 patients (46 eyes) with an average age of 66.9 +/- 6 years. Tests included ophthalmoscopy, visual acuity, the halometer glare disability test, stereocinematographic slit-image and retro-illumination photography with subsequent interactive digital image analysis and three-dimensional (3-D) computer graphics of the areas of lens light scattering/absorbing.

RESULTS

The intra-reader reproducibility of measuring techniques for cataractous changes was good. The Halometer instrument measures the angular distance from the glare source from which a specific target can be recognised. The source and the target are in the same vertical and tangential planes and to measure the angular distribution of the glare light, it is necessary to measure the incident light angle between the source and the target, by measuring the distance between the source and the target. The clinical Halometry readings assessed the index of the forward scattered light that reaches the retina and produces a veiling luminance (glare). The glare sensitivity score was determined from the angle of the glare source using both red and green optotypes, so that the effects of light absorption were separated from those of light scatter.

DISCUSSION

The interactive and automated computerised system discriminated the photographic image features of the back light-scattering/absorb centres within different grey thresholds and documented objective lens findings such as optical density, areas of equidensities, geometric surfaces, opacity grading. Digital image analysis gave a topographic and 3-D assembling and visualisation for nuclear, cortical and posterior subcapsular opacities in human lenses revealed from the optical scanning tomographic study of the anterior eye segment. The results indicate on agreement between clinical findings and applied quantitative techniques of analysis. This system has the potential to be a useful objective clinical assessment of cataract.

Night vision disturbances after corneal refractive surgery

A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.

Prospective randomised double-masked trial of bilateral multifocal, bifocal or monofocal intraocular lenses

AIMS

To evaluate the functional effect of bilateral implantation of two different multifocal intraocular lenses (IOL) compared with the standard monofocal IOL.

METHODS

Sixty-nine patients were recruited into a prospective, double-masked, randomised, controlled trial at a single hospital in the United Kingdom. Sixty completed follow-up; 16 implanted with monofocal IOLs, 29 with AMO 'ARRAY' multifocal IOLs and 15 with Storz 'TRUEVISTA' bifocal IOLs. Phacoemulsification and IOL implantation was performed to a standardised technique in both eyes within a 2-month period. The main outcome measures were distance and near visual acuity, depth of field and validated assessment of subjective function (TyPE questionnaire).

RESULTS

naided distance acuity was good, and equivalent across the three groups. Corrected distance acuity was significantly lower in the bifocal group. Patients with multifocal and bifocal IOLs could read smaller absolute print size than those in the monofocal group (P = 0.05), but at a closer reading distance such that mean unaided near acuity was equal in the three groups. Corrected near acuity was significantly higher in the monofocal control group (P < 0.05). Depth of field was increased in multifocal (P = 0.06) and bifocal (P = 0.004) groups. Overall visual satisfaction was equal in the three groups, while near visual satisfaction was higher in the multifocal group than the monofocal (P = 0.04). Spectacle independence was not seen in the monofocal group, but was achieved in 28% of multifocal IOL patients and 33% of bifocal patients (P < 0.001). Adverse symptoms such as glare and haloes were significantly more bothersome with multifocal (not bifocal) IOLs than monofocals (P = 0.01).

CONCLUSIONS

Multifocal and bifocal IOLs improved unaided near vision performance, with around one in three patients becoming spectacle-independent. The main adverse effect was an increased incidence of subjective glare and haloes in the multifocal IOL group.

Visual function after penetrating keratoplasty for keratoconus: a prospective longitudinal evaluation

AIMS

To evaluate visual function and vision specific health status in patients undergoing penetrating keratoplasty for keratoconus.

METHODS

A prospective longitudinal study measuring logMAR visual acuity, contrast sensitivity, disability glare, binocular visual field, stereoacuity, and subjective visual function (VF-14) was conducted on 18 patients with keratoconus undergoing penetrating keratoplasty (PK), including six patients who had already had PK in the fellow eye. Data were collected preoperatively and at 3, 9, and 18 months after surgery.

RESULTS

Within 3 months of surgery there was significant improvement in aided visual acuity, contrast sensitivity, and stereoacuity (p<0.05); disability glare (p<0.05) no longer had a significant detrimental effect on these variables. VF-14 score improved significantly throughout the postoperative period (p<0.05). There was significant correlation of the VF-14 score with aided visual acuity, binocular visual field, and stereoacuity. Postoperative astigmatism (<4D v >4D) did not affect the VF-14 score significantly.

CONCLUSIONS

There is substantial and rapid improvement in visual function and vision specific health status in keratoconic patients as a result of uncomplicated penetrating keratoplasty.

Comparison of methods to assess visual impairment from glare and light scattering with posterior capsule opacification

PURPOSE

To compare 2 glare tests to determine their relative usefulness in the assessment of posterior capsule opacification (PCO) and to evaluate the potential benefits of combined visual, acuity, contrast sensitivity, and glare testing.

SETTING

Teaching hospital ophthalmology department.

METHODS

Sixteen patients had glare, visual acuity, and contrast sensitivity testing before and after neodymium:YAG (Nd:YAG) capsulotomy. Results with the Brightness Acuity Tester (BAT, Mentor), which measures disability glare, and the Straylightmeter (Foundation for Eye Research, The Netherlands), which quantifies forward scatter by direct compensation techniques, were compared. The correlation between glare, ETDRS visual acuity, and Pelli-Robson contrast sensitivity was determined.

RESULTS

Pretreatment visual acuity was significantly correlated with contrast sensitivity (P < .01). However, visual acuity and contrast sensitivity were poorly correlated with both the BAT and Straylightmeter (P > .05), indicating that visual acuity is predictive of contrast sensitivity but a poor predictor of glare. Glare was significantly improved (Straylightmeter, P < .0001; BAT, P < .05) following capsulotomy. While the Straylightmeter consistently measured precapsulotomy forward scatter that improved with treatment, corresponding BAT disability glare was unmeasurable in 18.8% of patients with PCO, as their visual acuities improved rather than deteriorated with glare testing.

CONCLUSIONS

Glare testing provided more information than contrast sensitivity when combined with visual acuity in the evaluation of PCO. Glare related to PCO is better assessed using the Straylightmeter because the BAT may yield aberrant disability glare results.

Visual performance requirements for post-PRK police recruits

BACKGROUND: New Zealand Police regulations (1996) allow the unaided visual acuity requirement of 6/12 to be achieved following refractive surgery (except radial keratotomy or keratoplasty) provided applicants also achieve normal (95 per cent confidence limit data from the literature): glare disability, contrast sensitivity, and low luminance visual acuity, one year or more after treatment. METHODS: To confirm the limits adopted, 80 young normal adults were subjected to the tests in the regulations. To examine the operation of the current standards, the results of 34 post-photorefractive keratectomy (post-PRK) police applicants are reported. Glare disability was the loss of high contrast visual acuity (VA) with the Mentor Brightness Acuity Tester at medium intensity. Contrast sensitivity (CS) was examined using both Melbourne Edge Test thresholds and the VA difference between high and low contrast Bailey-Lovie charts. Low luminance VA was measured using high contrast Bailey-Lovie charts viewed through a one per cent transmittance filter. RESULTS: The 95 per cent confidence limits found for normal performance were as follows. Glare disability: no more than 10 letters worse than VA without glare. Contrast sensitivity: no more than 12 letters difference between high contrast and low contrast letter acuity together with an edge contrast threshold of not less than 20 dB (CS = 100). These results were close to the values adopted for the current standard. The 95 per cent confidence limit for low luminance VA was a loss of 24 letters (almost five lines) and not the three lines of loss estimated from the literature. Two of the 34 post-PRK applicants failed. One was unable to achieve 6/6 acuity with best refraction. The second could not meet the low luminance VA limit (loss no more than three lines). No failures have been due to glare disability or poor contrast sensitivity even though one applicant had obvious corneal haze.

Evaluation of visual function following neodymium:YAG laser posterior capsulotomy

PURPOSE

Improvement in visual acuity is the primary endpoint for successful neodymium:YAG (Nd:YAG) laser posterior capsulotomy for posterior capsule opacification. There is limited information on related parameters of visual function that may also improve after laser treatment. The authors evaluate changes in contrast sensitivity and glare disability, aside from visual acuity, following Nd:YAG laser posterior capsulotomy.

METHODS

Measurements of visual acuity, contrast sensitivity (using the Pelli-Robson chart), and glare disability (using the Brightness Acuity Tester [Mentor O & O, Inc., Norwell, MA]) were obtained from 24 consecutive patients before and after Nd:YAG laser posterior capsulotomy. Glare testing was done with both the Pelli-Robson and Early Treatment Diabetic Retinopathy Study (ETDRS) charts. The degree of glare disability was indicated by the difference between visual function with glare (at medium and high settings) and without glare. Prelaser measurements were taken within 2 weeks prior to treatment, and postlaser measurements were obtained within 3 months after treatment. Only one eye per patient was evaluated.

RESULTS

Mean differences between prelaser and postlaser measurements were significantly different from zero: (1) Contrast sensitivity, mean difference = 0.24 log units (P < 0.0001); (2) High glare disability using Pelli-Robson chart, mean difference = 0.15 log units (P = 0.004); (3) Visual acuity using ETDRS chart, mean difference = 11 letters (P < 0.0001); 4) High glare disability using ETDRS chart, mean difference = 7 letters (P = 0.005).

CONCLUSIONS

Using the above methods for visual function testing, Nd:YAG laser capsulotomy is shown to significantly improve visual acuity, contrast sensitivity, and glare disability measurements as compared with prelaser values. The ophthalmologist may find it helpful to document the last two measurements prior to Nd:YAG laser capsulotomy, especially in patients who have good visual acuity but complain of glare sensitivity.

Effect of a cataract simulation on clinical and real world vision

AIMS/BACKGROUND

Many reports have indicated that some patients with cataract can retain good visual acuity but complain of significant visual problems. This is the first in a series of papers trying to determine what causes these symptoms and whether other clinical tests can predict the real world vision loss.

METHODS

The effect of a cataract simulation with a similar angular distribution of light scatter as real cataract on clinical (visual acuity, contrast sensitivity, and disability glare) and real world vision (face recognition, reading speed, and mobility orientation) was investigated.

RESULTS

The simulation had a relatively small effect on visual acuity (6/6 with the simulation), but much larger effects on contrast sensitivity and low contrast acuity with and without glare. The simulation had no effect on high luminance and high contrast real world tasks, such as mobility orientation in room light and optimal reading speed. A small, but significant deterioration was found for the slightly lower contrast task of face and expression recognition. However, under low luminance conditions, substantial defects in mobility orientation were obtained (despite 6/6 acuity).

CONCLUSIONS

Although the relative effect of the cataract simulation on acuity and contrast tasks is not typical of the average cataract, it can be found in those cataract patients with visual problems despite good visual acuity. This corroborates the suggestion that it is large amounts of wide angle light scatter (forward and/or backward) which are at least partly responsible for visual disability in cataract patients with good visual acuity. A patient's reported visual disability may depend on the percentage of time he or she spends under low contrast and/or low luminance conditions, such as walking or reading in dim illumination, and walking or driving at night, in fog, or heavy rain.

Effect of age and astigmatism on the AMO Array multifocal intraocular lens

Multifocal intraocular lenses (MIOLs) have been designed to provide better uncorrected near visual acuity than monofocal IOLs. However, the increase in depth of focus is combined with a significant decrease in contrast sensitivity and glare. We implanted a new zonal-progressive MIOL (AMO Array) in 31 eyes of 25 patients whose mean age was 60.8 +/- 13.5 years. At 12.1 +/- 2.4 months postoperatively, the uncorrected visual acuity averaged 0.56 +/- 0.09 (20/32) for distance and 0.54 +/- 0.12 (20/40) for near focus. Seventy-five percent of patients achieved a best corrected distance visual acuity of > or = 0.9 (20/22). With distance correction only, mean near visual acuity was 0.72 +/- 0.17 (20/25). Best corrected near acuity reached 0.89 +/- 0.11 (20/22), requiring an additional near add of +1.0 to +2.0 diopters (D). We observed an age-dependent difference in the depth of focus. In younger patients (46 +/- 6 years), the pseudoaccommodation range was 6.25 D; acuity attained was > or = 0.4 (20/50). In older patients (71 +/- 7 years), visual acuity at the near focus was substantially reduced (two lines). Regan contrast sensitivity was lower for MIOL patients at all contrast levels, but the difference was statistically significant only at very low contrast (11%). Contrast sensitivity and glare were dependent on the patient's age but did not change with the amount of postoperative astigmatism. Younger patients were very satisfied with the results of MIOL implantation, and the small loss of contrast sensitivity was counterbalanced by the advantage of improved depth of focus and uncorrected near visual acuity.

Effect of filters on disability glare

Disability glare is the reduction in visual performance caused by a peripheral glare source. We examined the effect of a long wavelength pass (red) and a short wavelength pass (blue) filter on disability glare in the presence of varying amounts of induced wavelength dependent stray light. Measurements were made in the absence of any filter and then repeated in the presence of the red and blue filters whose luminous transmission factors were equal relative to both the stimulus and the glare source. Neither of the filters had any effect on disability glare. Filters not only reduce the amount of veiling luminance from the glare source, but also reduce the ability to detect the stimulus. Disability glare was not significantly different with the red and blue filters, even in the presence of wavelength dependent scatter. Calculation of the veiling luminance transmitted by each filter revealed that the difference in veiling luminance in the two filter conditions was insufficient to result in a measurable difference in disability glare.

Glare sensitivity in early cataracts

In a previous study significant glare sensitivity (using Vistech MCT8000) was found only in patients with posterior subcapsular cataracts (PSC) beyond the very early (LOCS II grade 1) stage. The aim of the present study was to evaluate glare sensitivity in patients with early cataracts. The brightness acuity tester (BAT) was used with the Pelli-Robson chart on 50 patients with early cataracts (LOCS II grade 1 or 2) and on 14 normal volunteers. Only age and PSC were found to be associated with change in contrast sensitivity at high glare. Eyes with grade 1 PSC were not significantly different from eyes with grade 0 PSC after adjusting for age. Eyes with grade 2 PSC had significant glare effect compared with eyes having grade 0 PSC. Thus, glare sensitivity is associated only with early (grade 2) PSC. Other tests still need to be developed to assess visual function changes in patients with early cortical and nuclear cataracts.

Corneal light scattering and visual performance in myopic individuals with spectacles, contact lenses, or excimer laser photorefractive keratectomy

Corneal transparency and visual performance are currently receiving much attention after excimer laser surgery. To date, emphasis has been on comparison of eyes on which laser surgery has been performed to eyes with emmetropia. A more appropriate comparison should be between eyes on which laser surgery has been performed and eyes with other forms of correction for myopia. Forward-scattered light, back-scattered light, and visual acuity were investigated and data were collected from 35 myopic individuals with various types of correction for myopia (spectacles, hard and soft contact lenses, and excimer laser surgery). Forward-scattered light was measured by using a new computerized technique, back-scattered light was measured with a charge coupled device-camera system, and visual acuity was measured with a computerized system at various levels of contrast. Spectacles, hard contact lenses, and excimer laser surgery are all superior to soft contact lenses in terms of light scatter and low-contrast visual acuity and excimer laser photorefractive keratectomy produces comparable results to spectacles one year postoperatively. At low-contrast visual acuity, mean visual acuity was 2.45 minutes of arc for the spectacle wearers, 3.21 minutes of arc for the hard contact-lens wearers, and 5.04 minutes of arc for the soft contact-lens wearers. Excimer laser patients had a mean visual acuity of 9.04 minutes of arc three months postoperatively, and 2.53 minutes of arc after one year. A mean value of 2.4% contrast for forward light scatter was obtained for spectacle wearers compared with a level of 3.84% contrast for hard contact-lens wearers and 16.1% contrast for soft contact-lens wearers. The mean value for excimer laser patients was 20% contrast three months postoperatively and 2.1% contrast one year postoperatively.

Measurement of glare sensitivity in cataract patients using low-contrast letter charts

The Committee on Ophthalmic Procedures Assessment of the American Academy of Ophthalmology suggested using low-contrast visual acuity measured before and after adding a glare source as a test for assessing overall visual disability from immature cataracts. We have developed a test that follows the Committee's three principles of design, and we report that the effect of glare on visual acuity is considerably greater for recognizing low-contrast letters than for recognizing high-contrast letters. The effect of glare on visual acuity increases progressively as letter contrast is reduced in the stages 96%, 50%, 25%, 11% and 4%. The 25% chart (and possibly the 11% chart) gives the most suitable sensitivity for eyes with immature cataracts. Age-related brunescence and aging itself do not necessarily produce high sensitivity to glare. Sensitivity to glare was markedly different in eyes with different kinds of cataract.

The morphology of cataract and visual performance

The various effects of cataract on vision are reviewed. The morphological types of senile cataract are classified into three basic categories: cortical spoke, nuclear and posterior subcapsular (PSC). The significant basic effect of cataract on the optical system of the eye is that of light scattering. Forward light scattering (light scattered towards the retina) accounts for reduced contrast sensitivity, for glare and for reduced visual acuity. Other effects of cataract are a myopic shift, a possible astigmatism change, monocular diplopia and polyopia, colour vision shift, reduced light transmission, and field of vision reduction. The effect of the various cataract morphologies on these functions is discussed. The nature of the effect varies with the degree of the cataract and with the cataract morphology. The assessment of a patient's visual disability is therefore not a simple task and cannot be based solely on the visual acuity nor on the objective measurement of the cataract.

Quantification of the reduction of glare disability after standard extracapsular cataract surgery

Glare disability is often cited as an indication for cataract extraction, but very little objective data exist showing improvement of glare disability following standard extracapsular cataract extraction with posterior chamber intraocular lens implantation. In a series of 25 patients we determined glare disability by the reduction in visual acuity with dim room lighting (baseline) and with full room lights; with the brightness acuity tester (BAT) on low, medium, and high; with the true vision analyzer (TVA) glare light. Glare disability was quantified by the difference between the log VA postoperatively and the log VA preoperatively. Glare disability with BAT medium was no different than that with bright room lights (P greater than .05). Glare disability with BAT high was greater than that with BAT medium (P less than .01) but did not differ from that with TVA (P greater than .05). Glare disability was significantly reduced (P less than .01) six weeks postoperatively as measured by all tests except BAT low. Cataract surgery can be expected to reduce glare disability as measured by these tests.

A prospective, randomized, double-masked comparison of a zonal-progressive multifocal intraocular lens and a monofocal intraocular lens

INTRODUCTION

Multifocal intraocular lenses (IOLs) have been designed to provide improved near visual acuity without spectacles compared with monofocal IOLs. Early studies have reported variables amounts of decreased visual acuity and contrast sensitivity with multifocal IOLs, and some patients have experienced halos and glare.

METHODS

The authors performed a prospective, double-masked, multicenter evaluation of 62 patients randomized between a new zonal-progressive optic multifocal IOL and a monofocal IOL.

RESULTS

Mean postoperative spherical equivalent, astigmatism, and uncorrected and best-corrected distance visual acuity were similar between the two groups. Patients with a multifocal IOL achieved significantly better uncorrected near visual acuity than patients with monofocal IOLs (J3+ versus J7; P less than 0.0001). With distance correction only, mean near visual acuity was J2 versus J5- (P = 0.0001). Best-corrected near visual acuity was J1 for both groups, with 1.36 diopters (D) for the multifocal group versus 2.37 D for the monofocal group (P less than 0.0001). Regan contrast sensitivity was lower for the multifocal patients at all contrast levels, and achieved statistical significance at very low contrast (11% contrast; P = 0.0024). Fifty-two percent of patients with a multifocal IOL reported that they did not need spectacles at all or used them only for their fellow eye, compared with 25% of the patients with monofocal IOLs.

CONCLUSION

Both monofocal and multifocal implant patients were very satisfied with the results of their cataract extraction and IOL implant surgery. A small loss of contrast sensitivity with the multifocal IOL was demonstrated, consistent with theoretical predictions. The functional significance of the loss of contrast sensitivity appears to be small and counterbalanced by the advantage of improved uncorrected near visual acuity.

Resolution testing of intraocular lenses

A basic goal associated with the manufacture of intraocular lenses (IOLs) is that they not be vision limiting. Manufacturers must therefore test IOL resolution against some minimum requirement. Currently, American National Standards Institute voluntary standard Z80.7-1984 addresses IOL optical requirements. One criterion of this standard is a minimum resolving power of 100 line-pairs-per-millimeter. This report presents some results of lens testing that suggest this standard is inadequate because it may not control the performance of a large enough fraction of the optic aperture.

Comparing clinical tests of visual function in cataract with the patient's perceived visual disability

Conventional techniques for assessing the visual function of cataract patients include visual acuity (VA), contrast sensitivity (CS) and glare disability (GD). The extent to which these measurements provide accurate information about a patient's perceived visual disability is not known. In this study, binocular and monocular VA and CS and monocular GD measurements were made using commercially available techniques on 33 cataract patients. VA was measured using a Ferris-Bailey LogMAR chart and CS by the Pelli-Robson letter CS chart. Glare disability was measured using the Mentor Brightness Acuity Tester in conjunction with both the LogMAR and Pelli Robson charts. Each patient's perceived visual disability was quantified using a 20-point questionnaire about the effect of vision on everyday activities. There was little correlation between subjective visual disability and monocular or binocular VA measurements. Measurements of binocular CS, however, were highly correlated with the patient's perceived visual disability, particularly their subjective assessment of the effect of vision on their mobility-orientation. We suggest that binocular CS measurements using the Pelli-Robson chart provide useful additional information regarding the need for surgery in cataract patients.

Glare and contrast sensitivity in contact lens corrected aphakia, epikeratophakia and pseudophakia

The effects of glare on contrast sensitivity and high contrast Snellen acuity were investigated in a group of unilaterally aphakic patients with normal fellow eyes. In spite of relatively good visual acuity and apparently satisfactory surgical results, there was a marked reduction in contrast sensitivity in epikeratophakia and contact lens corrected aphakic eyes, relative to fellow normal eyes, especially in the presence of glare (P less than 0.05). Although the results from the pseudophakic patients were more variable, there is some evidence to suggest that epikeratophakia provides inferior visual function to contact lens correction or intraocular lens implantation. The results also suggest that the measurement of visual acuity in the presence of glare fails to identify many patients with a functional visual impairment secondary to glare.

Glare and contrast sensitivity testing in cataract patients

I measured contrast sensitivity and glare in 51 cataract patients who had Snellen visual acuities of 20/60 or better. The VCTS contrast sensitivity plates, the Miller-Nadler glare tester, Baylor visual function tester, and the Stereo Optical glare tester were used. Patients indicated that the Baylor visual function tester most closely reproduced their daytime glare symptoms and that the Stereo Optical glare tester most closely reproduced their nighttime glare symptoms. Scores on the Stereo Optical glare tester and VCTS contrast sensitivity chart statistically were most strongly correlated with patients' complaints and the severity of their lens opacities. Contrast sensitivity and glare testing are important adjuncts in evaluating patients who have visual complaints and yet have good Snellen acuities.

Reversal of glare disability after cataract surgery

Awareness of the limitations of Snellen vision testing and the favorable risk-to-benefit ratio for cataract surgery have changed the indications for cataract rehabilitation. Interest in functional vision analysis generated the present study, which was designed to identify cataract-specific disabling glare and its reversal with best-case cataract surgical techniques. Thirty eyes with symptomatic cataracts and no other ocular diseases were evaluated by Miller-Nadler glare testing prior to and six weeks after surgery. All surgical cases were uncomplicated and were free of macular disease. They had well-centered posterior chamber intraocular lenses, clean posterior capsules, and were returned to 20/20 Snellen acuity. Careful patient selection assured that presurgical glare disability was due to cataract formation. Presurgical Miller-Nadler scores were markedly elevated and correlated well with symptomatic glare, whereas postoperative scores were indistinguishable from normals, suggesting that cataract-induced symptomatic glare is discernible, remediable, and warrants surgical intervention, but requires best-case surgery to assure glare reversal.

Glare testing in cataract patients: instrument evaluation and identification of sources of methodological error

This study sought to determine the relative sensitivity of two commercially available glare testers in predicting outdoor acuity in a population of patients with minimal cataracts. Two target optotypes were evaluated: high contrast letters and varying contrast sinusoidal gratings. Although both instruments demonstrated a significant correlation between indoor and outdoor acuity, they showed a significant difference between predicted outdoor acuity and obtained visual acuity. The brightness acuity tester on high intensity was inaccurate in predicting outdoor vision regardless of test optotype, overpredicting glare disability in 76% (average) of the study population. Glare disability overpredictions fell to 8% on the medium setting with +/- 2 lines of vision classified as "no change." Using the same criterion, the Miller-Nadler glare tester overpredicted glare disability in 2% of the cataract population but underpredicted glare disability in 62%. In this study, letter optotypes resulted in less variability than sinusoidal grating stimuli. In addition, we identify several methodological factors to consider before designing a glare experiment. These potential sources of error can influence the outcome of any glare study that compares indoor and outdoor acuity and include the study population, visual stimuli (optotypes), and elements of the outdoor testing situation.

Glare disability devices for cataractous eyes: a consumer's guide

We evaluated five commercially available glare testers to determine how accurately each device predicted outdoor Snellen acuity in cataract patients. Predicted outdoor Snellen acuity was compared to actual Snellen outdoor acuity for the Miller-Nadler glare tester, the brightness acuity tester (BAT), the InnoMed true vision analyzer (TVA), the VisTech VCT 8000, and the EyeCon 5. All five devices were evaluated in a single series of eyes. We ranked the five glare testers as follows based upon their ability to predict outdoor Snellen acuity within one Snellen line: (1) BAT (73%), (2) TVA (69%), (3) VisTech VCT 8000 (56%), (4) Miller-Nadler (47%), and (5) EyeCon 5 (15%). All five devices were also evaluated for their capacity to provide false negative or false positive results and for testing time per eye, test difficulty level for the patient, versatility, upgrading capacity, examining room adaptability, and price. We concluded that glare testing of cataract patients is necessary to measure visual disability and that glare testing devices vary in their ability to predict outdoor vision.