The usefulness of Vistech and FACT contrast sensitivity charts for cataract and refractive surgery outcomes research

The relation between driving experience and recognition of road signs relative to their locations

OBJECTIVES

Examine how driving experience and expectations affect the ability of experienced drivers to identify traffic signs--specifically, no right turn (NRT) and no left turn (NLT) at intersections.

BACKGROUND

Failure to heed signs is a frequent cause of accidents, and the authors focused on the contributions of experience and expectancy to sign identification.

METHOD

Inexperienced and experienced drivers were connected to an eye tracker system and briefly exposed to various traffic scenes. Some of the pictures included an NRT sign at the expected location (on the right), and some included the same sign at an unexpected location (on the left). The same procedure was used with an NLT traffic sign.

RESULTS

Experienced drivers identified traffic signs better than inexperienced drivers did when the signs were posted at the expected location but identified them worse than did inexperienced drivers when they were at unexpected locations.

CONCLUSIONS

With experience, drivers' expectations regarding the expected location of traffic signs become so strong that violating these expectancies results in more identification errors among experienced drivers than among inexperienced drivers. To optimize experienced drivers' traffic sign identification, signs must be located in accordance with drivers' expectations--specifically, on the right side of the road.

APPLICATIONS

When signs are misplaced, crashes can be caused by inappropriate placement rather than inappropriate driving. Highway designers should ensure that their design conforms to standards that shape experienced drivers' expectations.

[Photopic contrast sensitivity. Local contrast perception]

Contrast perception is an important visual function. Contrast sensitivity (CS) is affected by to optical reasons (aberrations, scatter, diffraction) or neural dysfunction (e.g., glaucoma, optic nerve diseases). In clinical practice the measurement of CS is relevant for disease monitoring, expert opinions, roadworthiness assessment, and recruitment screening. Furthermore, CS testing is often required in studies assessing optical quality, e.g., cataract or refractive surgery. Adding an appropriate glare source allows measurement of the glare-induced loss of CS (disability glare). Compared to high-contrast acuity, CS is more variable and strongly depends on the type of test, illumination, test strategy, and contrast definition; ceiling effects are quite common among many tests. Maximal standardization is important, especially for follow-up exams. In summary, CS testing cannot be regarded as a routine test. The present report by the DOG commission for quality management of psychophysical assessment covers the physiological background, testing principles, and strategies and presents a tabular overview of common tests.

Binocular implantation of the Tecnis Z9000 or AcrySof MA60AC intraocular lens in routine cataract surgery

PURPOSE

To compare vision-related quality of life after binocular implantation of the Tecnis Z9000 intraocular lens (IOL) (Advanced Medical Optics) or the AcrySof MA60AC IOL (Alcon).

SETTING

Moorfields Eye Hospital, London, United Kingdom.

METHODS

The study was a double-masked prospective randomized controlled trial. The main outcome measure was the percentage of patients achieving a Visual Function-14 (VF-14) score of 90 or higher. Additional outcome measures were dysphotopsia symptom scores, a 5-point subjective grading of overall satisfaction, refraction, photopic and mesopic best corrected visual acuities, uncorrected visual acuity, Pelli-Robson contrast sensitivity, aberrometry, infrared pupillometry, and evaluation of posterior capsule opacification scores.

RESULTS

Seventy-nine patients who had bilateral implantation of the Z9000 IOL and 100 patients who had bilateral implantation of the MA60AC IOL were assessed a mean of 7.9 months +/- 2.9 (SD) (range 4 to 16 months) after second-eye surgery. Spherical aberration (mean: Z9000, 0.00 microm +/- 0.06 [SD]; MA60AC, +0.14 +/- 0.09 microm) and root mean square scores for higher-order aberrations combined (mean: Z9000, 0.26 +/- 0.11 microm; MA60AC, 0.32 +/- 0.14 microm) were significantly lower in patients with the Z9000 IOL (P<.001 and P = .007, respectively). The VF-14 scores were 90 or higher in 96.2% of Z9000 patients and 90.0% of MA60AC patients (P = .15). It is unlikely that this weak trend in favor of the Z9000 IOL was clinically significant. The VF-14 scores were heavily skewed toward a perfect outcome and similarly distributed in both groups (median 100; interquartile range 98 to 100). Results for all other outcomes, including measures of acuity, were similarly distributed in Z9000 patients and MA60AC patients.

CONCLUSIONS

The Z9000 IOL reduced spherical aberration compared with the MA60AC IOL. No improvement in subjective visual function using the VF-14 questionnaire was detected.

Measuring contrast sensitivity in normal subjects with OPTEC® 6500: influence of age and glare

BACKGROUND

The purpose of this study was to develop age-related curves for contrast sensitivity (CS) in normal subjects under day and night conditions with and without glare.

METHODS

Sixty-one healthy eyes from 61 subjects were measured with the OPTEC(R) 6500 P under day and night conditions (luminance levels: 85 cd/m(2) and 3.0 cd/m(2) with and without glare; spatial frequencies: 1.5, 3, 6, 12 and 18 cycles/degree). A reliability analysis with five repeated measurements of six persons on 4 days was performed to examine the repeatability. The influence of age on contrast sensitivity, forward and backward scatter was examined by means of linear regression.

RESULTS

Contrast sensitivity was significantly reduced under night conditions with glare, whereas glare had less influence under daylight illumination. Mean reliability coefficients are 0.87 (day), 0.77 (day with glare), 0.69 (night) and 0.81 (night with glare), which suggests sufficient retest reliability of the device. Regression analyses showed a highly significant influence of age, but the variance of the measurement values is not explained by age alone. The coefficients of determination for the regression of area under the log contrast sensitivity function (AULCSF) on age are 0.33 (photopic), 0.34 (photopic with glare), 0.29 (mesopic) and 0.36 (mesopic with glare, p < 0.0001 in all cases).

CONCLUSION

A significant relationship between age, CS and scatter was confirmed in our study. The results provide baseline values for the examination of patients with different diseases in which contrast sensitivity is impaired (such as glaucoma, cataracts and amblyopia) and might be useful in studies of roadworthiness or in investigation of the impact of intraocular lenses.

Genetic influence on contrast sensitivity in middle-aged male twins

Contrast sensitivity is strongly associated with daily functioning among older adults, but the genetic and environmental contributions to this ability are unknown. Using the classical twin method, we addressed this issue by examining contrast sensitivity at five spatial frequencies (1.5-18 cycles per degree) in 718 middle-aged male twins from the Vietnam Era Twin Study of Aging (VETSA). Heritability estimates were modest (14-38%), whereas individual-specific environmental influences accounted for 62-86% of the variance. Identifying the types of individual-specific events that impact contrast sensitivity may suggest interventions to modulate this ability and thereby improve overall quality of life as adults age.

Quels bénéfices visuels peut-on attendre d’un implant sans aberration sphérique dans la chirurgie de la cataracte ?

PURPOSE

To assess the quality of vision in pseudophakic patients with aspheric intraocular lens (IOL) without spherical aberration compared to patients with spherical IOL.

METHODS

Twenty-four patients (48 eyes) undergoing cataract surgery were randomly divided into two groups: 12 patients received an aspheric IOL in both eyes and 12 received spherical IOLs. The integrity of ocular functions was assessed with clinical examination and multifocal electroretinogram. Postoperative evaluations were conducted 3 months after surgery. Refraction, best-corrected visual acuity, contrast sensitivities, and wavefront ocular aberrations were analyzed. Patient-centered visual functions were evaluated according to the Activities of Daily Vision Scale.

RESULTS

The ADVS score was better in the aspheric IOL group (p=0.01), particularly concerning the best-corrected near vision (p=0.006). Refraction and BCVA were similar. Contrast sensitivities in photopic conditions was better in the aspherical IOL group (p<0.001). Higher-order aberration was not different, except from spherical aberration (p=0.022).

CONCLUSION

Patients with the aspherical IOLs felt they had better quality of vision, particularly near vision, compared with the spherical IOL group. These patient-centered benefits were associated with better photopic contrast sensitivity and reduced spherical aberration.

Takagi Glare Tester CGT-1000 for Contrast Sensitivity and Glare Testing in Normal Individuals and Cataract Patients

PURPOSE

To investigate the sensitivity and repeatability of the Takagi Contrast Glare Tester CGT-1000 in normal individuals and those with cataracts.

METHODS

A prospective observational study was performed. The Takagi Contrast Glare Tester measures contrast sensitivity (CS) at 6 target sizes and 13 contrast levels (2.00 to 0.34 logCS). Testing follows a method of descending limits paradigm with a single reversal determining threshold. The CGT-1000 was administered with and without glare in 95 eyes of 61 cataract patients and 13 controls. The percentage floor (unable to see the highest contrast) and ceiling (able to see the lowest contrast) effects and correlations between CS and cataract grades were determined. The repeatability was evaluated using Bland-Altman limits of agreement and expressed as the coefficient of repeatability (COR). Factor analysis was used to test for redundancy within the 6 spatial frequencies.

RESULTS

In normal individuals, a high rate of ceiling effect varying with target size was noted--for 6.3 degrees, 4.0 degrees, 2.5 degrees, 1.6 degrees, 1.0 degrees, 0.7 degrees, ceiling effects were 68%, 58%, 18%, 11%, 4%, 2%, respectively, for no glare, and 47%, 42%, 8%, 2%, 2%, 2%, respectively, with glare. In cataract patients, floor effects were noted--3%, 0%, 3%, 7%, 19%, 62%, respectively, for no glare, and 3%, 3%, 6%, 14%, 44%, 79%, respectively, with glare. Correlations with cataract grades ranged from 0.10 to 0.61, being best for nuclear cataract. Repeatabilities expressed as COR were +/- 0.11, +/- 0.14, +/- 0.28, +/- 0.38, +/- 0.38, +/- 0.47 logCS, respectively. All spatial frequencies loaded heavily on one factor, indicating no gain in information from testing multiple target sizes.

CONCLUSIONS

Sensitivity to the presence of cataract was good, but ceiling effects in normal individuals and floor effects in cataract patients limit accuracy. Repeatability was poor, but could be improved by testing less spatial frequencies more rigorously.

Visual acuity, contrast sensitivity, peripheral vision and refraction in low birthweight teenagers

PURPOSE

To assess visual acuity (VA), contrast sensitivity, visual fields, refractive errors and use of correction in adolescents with very low birthweight (VLBW; birthweight < 1500 g) and adolescents born at term but small for gestational age (SGA; birthweight < 10th percentile) in a population-based study.

METHODS

Ophthalmological examination including VA, Vistech contrast sensitivity and Humphrey two-zone, 120-point perimetry was performed in 51 VLBW, 59 SGA and 77 control adolescents.

RESULTS

The VLBW adolescents had reduced VA, reduced contrast sensitivity, and were more often anisometropic compared with control adolescents. They had started wearing glasses earlier, but were not more likely to use correction as teenagers. However, they were more often undercorrected (for refractive status) than control adolescents. Hypermetropia was more common in the SGA group than in the control group, but otherwise the SGA group did not differ from the control group.

CONCLUSIONS

Being born SGA may be a risk factor for hypermetropia in adolescence. Prematurely born adolescents present lower VA and contrast sensitivity and are more prone to anisometropia than adolescents born at term. It may be noteworthy that a higher proportion of VLBW than control adolescents were undercorrected, despite the well known vulnerability of visual function associated with preterm birth.

Contrast Sensitivity After LASIK, LASEK, and Wavefront-guided LASEK With the VISX S4 Laser

PURPOSE

To evaluate the changes in contrast sensitivity and glare after corneal refractive surgery for moderate myopia.

METHODS

The study comprised 267 eyes of 149 patients who underwent LASIK, laser epithelial keratomileusis (LASEK), or wavefront-guided LASEK with the VISX STAR S4. Contrast sensitivity was measured with VCTS 6500 before surgery and at 2 and 6 months postoperatively. Glare was evaluated using questionnaires and the ALC glare test at last follow-up. Contrast sensitivity at 2 and 6 months was compared with preoperative contrast sensitivity in each group. Glare sensitivity in each group was compared to normal controls.

RESULTS

Contrast sensitivity did not change after LASIK (P > .05). Contrast sensitivity of 3 and 6 cycles per degree (cpd) at 2 months increased after LASEK (P < .05) and contrast sensitivity of 6, 12, and 18 cpd at 2 months and 3, 6, 12, and 18 cpd at 6 months improved in wavefront-guided LASEK (P < .05). Glare test and questionnaires did not show any significant difference between the groups.

CONCLUSIONS

Wavefront-guided LASEK induced significant increases in contrast sensitivity of moderate myopes at high spatial frequencies under mesopic conditions by 6 months. Glare was not affected by the different refractive procedures.

Quality of vision after cataract surgery after Tecnis Z9000 intraocular lens implantation: effect of contrast sensitivity and wavefront aberration improvements on the quality of daily vision

PURPOSE

To compare ocular performance and quality of vision in pseudophakic eyes with an aspherical intraocular lens (IOL) or a conventional spherical IOL.

SETTING

Bretonneau University Hospital, Tours, France.

METHODS

Twenty patients (40 eyes) were randomly divided in 2 equal groups to bilaterally receive the aspherical Tecnis Z9000 IOL (AMO) or the spherical CeeOn Edge 911 IOL (AMO). Contrast sensitivity was measured and ocular wavefront analysis performed before surgery and 6 months after. Patients completed the Activities of Daily Vision Scale (ADVS) to evaluate patient-centered visual outcomes. Other examinations included refraction before and after mydriasis and pupil diameter.

RESULTS

The mean postoperative best corrected visual acuity (logMAR) was 0.03 +/- 0.05 (SD) in the Tecnis group and 0.01 +/- 0.05 in the CeeOn Edge group (P = .41). Refractive evaluation with mydriasis showed a mean myopic shift as low as -0.02 +/- 0.36 diopter (D) in the Tecnis group and -0.51 +/- 0.37 D in the CeeOn Edge group (P = .001). Mesopic contrast sensitivity at high spatial frequencies was significantly better in the Tecnis group (P<.001), while contrast sensitivity under photopic and glare conditions was not different between the 2 groups. Spherical aberration was significantly lower in the Tecnis group, which had a mean Z(4)(0) of 0.01 +/- 0.06 microm, than in the CeeOn Edge group, which had a mean Z(4)(0) of 0.16 +/- 0.12 microm (P<.001). The global score on the ADVS was not statistically different between groups; however, quality of distance vision was better in the Tecnis group than in the CeeOn Edge group (mean 99.0 +/- 2.0 versus 89.2 +/- 3.4) (P<.001).

CONCLUSION

Implantation of an aspherical IOL with a negative spherical aberration resulted in reduced ocular spherical aberration and improved mesopic contrast sensitivity and led to better subjective quality of vision.

Penetrating Keratoplasty for Keratoconus: The Nexus Between Corneal Wavefront Aberrations and Visual Performance

PURPOSE

To compare the visual and optical performance after penetrating keratoplasty (PK) for keratoconus to normal patients and to examine the relationship between corneal wavefront aberrations and visual performance in patients with PK.

METHODS

Visual performance testing, with optimal refractive correction, included low contrast visual acuity (LCVA) and Pelli-Robson contrast sensitivity with and without glare, and high contrast visual acuity. Corneal first surface wavefront aberrations were calculated from EyeSys topography data using VOL-Pro software v7.00 for a 4.0-mm pupil as a 10th order Zernike expansion and converted into single value metrics. Normal patients were compared to patients with PK using analysis of variance, and linear regression was used to compare wavefront aberration metrics to visual performance.

RESULTS

Patients with PK (n=14, age 41.6 +/- 7.0 years) and normal patients (n=14, age 36.7-9.0 years) were of similar age (F(1, 26) = 2.54, P = .12). Normal patients saw significantly better on all visual performance measures and had better optical performance for total higher order root-mean-square corneal wavefront aberration (mean-SD): PK, 0.67 +/- 0.41 microm; normal, 0.09 +/- 0.02 microm (F(1,26) = 28.41, P < .001) and across all Zernike orders and modes. Wavefront aberrations in PK eyes were dominated by trefoil 0.35 +/- 0.27 microm, coma 0.47 +/- 0.37 microm, spherical aberration 0.17 +/- 0.10 microm, and tetrafoil 0.12 +/- 0.07 microm. The relationships between corneal wavefront aberration and visual performance metrics were strongest for LCVA = 0.30-0.98 Pupil fraction for wavefront (tessellation) -0.04 Half width at half height, R2=0.75.

CONCLUSIONS

In this series, patients with PK had poorer visual performance compared to normal patients, which is due to increased corneal wavefront aberrations. Outcomes research in corneal transplantation should include measurement of wavefront aberrations and visual performance in the contrast domain.

Color stimuli perception in presence of light scattering

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresponding to the blue, green, and red color contributions in achromatic white stimuli (computer digital R, G, or B values for chromatic stimuli equal to RGB values in the achromatic white background) that results in the greatest luminance contrast for the white–blue stimuli, thus advancing the visual acuity for the white-blue stimuli. Besides such blue stimuli on the white background are displayed with a uniform, spatially unmodulated distribution of the screen blue phosphor emission over the entire area of the screen including the stimulus C optotype area. It follows that scattering, which has the greatest effect on the blue component of screen luminance, has the least effect on the perception of white–blue stimuli.

Measurement of Contrast Sensitivity and Glare Under Mesopic and Photopic Conditions Following Wavefront-guided and Conventional LASIK Surgery

PURPOSE

To compare contrast and glare vision in a prospective study of eyes treated using conventional and wavefront-guided LASIK surgery. The reproducibility of a glaremeter device used to quantitatively measure glare and halo was also determined.

METHODS

Ninety-two eyes of 46 patients underwent conventional LASIK surgery and 104 eyes of 52 patients underwent wavefront-guided LASIK surgery. Visual acuity, glare disability measured using a glaremeter, and contrast sensitivity assessed using a Pelli-Robson chart were measured monthly for 6 months postoperatively. Glaremeter testing was performed under both mesopic (5.4 +/- 0.4 cd/m2) and photopic (78.3 +/- 4.4 cd/m2) conditions. To evaluate the reproducibility of the glaremeter, 36 eyes of 18 nonoperated myopic patients were tested.

RESULTS

The coefficient of variation and the reliability coefficient for the glare test were 13.6% and 95.2%, respectively. The glaremeter showed that glare disability under mesopic conditions differed between conventional and wavefront-guided LASIK eyes over 6-month follow-up (907.5 +/- 491.5 vs 986.1 +/- 448.0 pixels preoperatively and 1717.1 +/- 521.2 vs 1407.8 +/- 411.3 pixels at 6 months, P<.0001). At 6 months, contrast sensitivity log values were 1.62 +/- 0.31 and 1.78 +/- 0.34 for conventional and wavefront-guided LASIK eyes, respectively (P=.010). The visual complaint score was lower in the wavefront-guided LASIK group (P=.0116).

CONCLUSIONS

Compared to conventional ablation, wavefront-guided ablation provided superior outcomes in terms of postoperative glare under mesopic conditions, subjective complaints, and contrast sensitivity. In addition, it appears the glaremeter can be used for clinical quantitative evaluation of glare and halo.

Measuring contrast sensitivity under different lighting conditions: comparison of three tests

PURPOSE

The purpose of this study was to evaluate three psychophysical tests for the measurement of contrast sensitivity (CS) and disability glare (DG) at different luminance levels.

METHODS

In 60 eyes of 60 individuals (group 1: 20 healthy eyes of young individuals; group 2: 20 healthy eyes of elderly subjects; group 3: 20 eyes with nuclear cataract), CS with best correction was measured twice with the Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) and the Functional Acuity Contrast Test (FACT, 1.5 cycles per degree [cpd]) at 167 cd/m2 and 0.167 cd/m2, and with the Pelli-Robson Chart (PRC) at 100 cd/m2 with and without glare. Repeatability of test and retest, and discriminative ability between the different subgroups, were assessed for CS values.

RESULTS

Maximum CS values varied across tests. In all groups, highest CS values were obtained with the photopic FF-CATS. For FACT scores at 1.5 cpd, there was a ceiling effect for young subjects. CS scores obtained with the PRC were the lowest. The PRC had the best test-retest repeatability of all tests. Under mesopic conditions with glare, reliability was generally lower; the FF-CATS had the highest repeatability of the mesopic tests. The FF-CATS discriminated best between the different groups for all conditions.

CONCLUSIONS

There are large discrepancies in the test results between CS testing methods, especially under different lighting conditions. Results from different CS tests are not interchangeable.

Accuracy of the contrast sensitivity card test for infants: retest variability and prediction of spatial resolution

PURPOSE

We assessed the retest variability of a new contrast sensitivity (CS) card procedure and its ability to predict spatial resolution.

METHODS

Twenty-four 3-month-olds were tested twice with the CS cards and once with the Teller acuity cards (TAC) within a single session.

RESULTS

Coefficient of repeatability (COR) analysis revealed that retest variability of the new cards is superior to that of an earlier prototype at low to mid spatial frequencies. Furthermore, retest variability is comparable to that of infant visual evoked potential studies and the Vistech 6500, a chart commonly used to measure CS in adults. Finally, estimates of visual acuity based on the CS cards were consistent with those provided by the TAC (although CS-based estimates were generally lower overall).

CONCLUSIONS

Given its reliability and accuracy, the new CS card procedure has good potential as a clinical tool for assessing spatial vision in infants and toddlers.

[Optical quality after refractive corneal surgery]

Correction of myopia, hyperopia and astigmatism within its indicated margin by means of refractive corneal surgical procedures such as LASIK and surface ablation (e.g. PRK) is one of the standard procedures in ophthalmology. Now that advances in the fields of surgical techniques and the technical devices employed have further progressed in terms of safety and predictability, research also focuses on optical quality. "Optical quality" is not a clearly defined parameter, but can be captured indirectly by means of directly measured data. One has to start with the anatomical properties of the eye, which determine the optical images on the retinal level. The quality of the retinal image influences the eye's function, i.e. acuity and contrast perception. Finally, there is the subjective perception of the image we receive. "Optical quality" as such is reflected by the patient's evaluation of this image perception. Three phenomena are especially responsible for deterioration of the quality of the retinal image: diffraction, aberrations and dispersion. Some of the methods for measuring optical quality are subjective questionnaires, functional testing procedures for measuring visual acuity and contrast sensitivity, optical measuring procedures for the determination of optical quality, as well as biomicroscopy, aberrometry and corneal topography for assessing anatomical changes.

Contrast sensitivity in 10 year old preterm and full term children: a population based study

AIMS

To determine the contrast sensitivity (CS) in 10 year old prematurely born children, previously included in a population based study on the incidence of retinopathy of prematurity (ROP), and in full term controls.

METHODS

This study included 205 prematurely born children and 215 children born at term, from the same geographical area and study period. CS was assessed monocularly with the Vistech 6500 test at five spatial frequencies (1.5-18 cycles/deg).

RESULTS

Prematurely born children had statistically significant lower CS at all frequencies, compared to full term ones. The mean differences in logarithmic CS were 0.03 (1.5 cycles/deg), 0.09 (3 cycles/deg), 0.10 (6 cycles/deg), 0.12 (12 cycles/deg), and 0.19 (18 cycles/deg). Even when the children with ROP and neurological disorders were excluded there was a difference between the two groups. Children who had been treated with cryotherapy had the lowest CS.

CONCLUSION

CS was lower in 10 year old prematurely born children than in full term ones of the same age. Whether this finding affects their visual function in daily life is uncertain.

Das „Frankfurt-Freiburg Contrast and Acuity Test System“ (FF-CATS)

BACKGROUND

The purpose of the present study was to evaluate a computerized test for measurement of contrast sensitivity thresholds under variable ambient and glare luminance levels.

METHODS

A total of 40 eyes of 40 healthy subjects were examined with the FF-CATS and the Functional Acuity Contrast Test (FACT) at 0.167 cd/m(-2) (mesopic) and 167 cd/m(-2) (photopic). Measurements were performed twice with and without glare in a randomized fashion. Tests were evaluated according to three criteria: (1) repeatability, (2) discriminative ability, and (3) validity.

RESULTS

The FF-CATS showed a higher discriminative ability between the two groups compared to the FACT charts. Under photopic conditions, the COR value was 0.39 for the FF-CATS and 0.26 for the FACT charts; under mesopic illumination, the COR value for the FF-CATS was 0.46 and 0.36 for the FACT charts.

CONCLUSION

The FF-CATS is a reliable, sensitive, valid, and flexible test system for the determination of visual acuity and contrast sensitivity thresholds under variable ambient and glare luminance conditions.

Contrast and glare testing in keratoconus and after penetrating keratoplasty

AIM

To compare the performance of keratoconus, penetrating keratoplasty (PK), and control subjects on clinical tests of contrast and glare vision, to determine whether differences in vision were independent of visual acuity (VA), and thereby establish which vision tests are the most useful for outcome studies of PK for keratoconus.

METHODS

All PK subjects had keratoconus before grafting and no subjects had any other eye disease. The keratoconus (n = 11, age 35.0 (SD 11.1) years), forme fruste keratoconus (n = 6, 33.0 (13.0)), PK (n = 21, 41.2 (7.9)), and control (n = 24, 33.7 (8.6)) groups were similar in age. Vision testing, conducted with optimal refractive correction in place, included low contrast visual acuity (LCVA) and Pelli-Robson contrast sensitivity (PRCS) both with and without glare, as well as VA.

RESULTS

Normal subjects saw better than PK subjects who in turn saw better than keratoconus subjects on all raw measures. However, when adjusted for VA, the normal group only saw significantly better than the keratoconus group on LCVA (low contrast loss 0.05 (0.04) v 0.15 (0.12), F(2,48) = 6.16; p<0.01, post hoc Sheffé p<0.05), and the decrements to glare were no worse than for normals. The forme fruste keratoconus group were indistinguishable from normals on all measures.

CONCLUSIONS

PK subjects have superior vision to keratoconus subjects, but not as good as normal subjects. Including mild keratoconus subjects within a keratoconus group could confound these differences in vision. While VA is an excellent test for comparing normal, keratoconus and PK groups, additional information can be provided by LCVA and PRCS, but not by glare testing. Outcomes research into keratoconus management should include a measure in the contrast domain.