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

Predicting individual contrast sensitivity functions from acuity and letter contrast sensitivity measurements

Contrast sensitivity (CS) is widely used as a measure of visual function in both basic research and clinical evaluation. There is conflicting evidence on the extent to which measuring the full contrast sensitivity function (CSF) offers more functionally relevant information than a single measurement from an optotype CS test, such as the Pelli-Robson chart. Here we examine the relationship between functional CSF parameters and other measures of visual function, and establish a framework for predicting individual CSFs with effectively a zero-parameter model that shifts a standard-shaped template CSF horizontally and vertically according to independent measurements of high contrast acuity and letter CS, respectively. This method was evaluated for three different CSF tests: a chart test (CSV-1000), a computerized sine-wave test (M&S Sine Test), and a recently developed adaptive test (quick CSF). Subjects were 43 individuals with healthy vision or impairment too mild to be considered low vision (acuity range of -0.3 to 0.34 logMAR). While each test demands a slightly different normative template, results show that individual subject CSFs can be predicted with roughly the same precision as test-retest repeatability, confirming that individuals predominantly differ in terms of peak CS and peak spatial frequency. In fact, these parameters were sufficiently related to empirical measurements of acuity and letter CS to permit accurate estimation of the entire CSF of any individual with a deterministic model (zero free parameters). These results demonstrate that in many cases, measuring the full CSF may provide little additional information beyond letter acuity and contrast sensitivity.

Post-lens tear turbidity and visual quality after scleral lens wear

BACKGROUND

The aim was to evaluate the turbidity and thickness of the post-lens tear layer and its effect on visual quality in patients with keratoconus after the beginning of lens wear and before lens removal at the end of eight hours.

METHODS

Twenty-six patients with keratoconus (aged 36.95 ± 8.95 years) participated voluntarily in the study. The sample was divided into two groups: patients with intrastromal corneal ring (ICRS group) and patients without ICRS (KC group). Distance visual acuity (VA), contrast sensitivity, pachymetry, post-lens tear layer height and post-lens tear layer turbidity (percentage area occupied and number of particles per mm² ) were evaluated with optical coherence tomography before and after wearing a scleral lens.

RESULTS

A significant increase of turbidity was found in all groups assessed (p < 0.05). The number of particles per square millimetre was eight times higher after scleral lens wear than at the beginning of wearing the lens for all groups. VA decreases in all groups after scleral lens wear (p < 0.001). All patients showed a statistical diminishing of contrast sensitivity after scleral lens wear (p < 0.05). A significant correlation was found for both turbidity parameters with distance VA but no correlation between turbidity and post-lens tear layer thickness at the beginning was found (p > 0.05). A strong correlation in all groups between the post-lens tear layer at the beginning and differences of tear layer thickness between two measures was also found (p < 0.05).

CONCLUSION

The VA decrease during the scleral lens wearing, filled with preserved saline solution, was due to the increasing post-lens tear layer turbidity.

Inter-Display Reproducibility of Contrast Sensitivity Measurement with iPad

PURPOSE

To evaluate the reliability of measuring CS with uncalibrated iPads.

METHODS

Six random iPads with retina display were calibrated with a colorimeter and the correlation between Luminance (L) and pixel level (y) was computed according to an exponential function. The mean and confidence interval (±2SD) obtained from the six iPads were calculated and the bit-stealing technique was applied for expanding y from 256 to 2540 possible values. The L of the optotype was computed for the selected contrast values (logC) represented in log units, using 0.1 log and 0.05 log steps. At each particular y, the contrast was considered reliable when the mean L plus 2SD was less than half the difference of luminance between two consecutive levels of contrast. Differences between the iPads for the Experimental logC were evaluated with the Friedman test.

RESULTS

Luminance properties vary between devices, which were reflected in the computed Experimental logC (p < 0.0005). The contrast was found to be reliable for 0.1 log steps in the range from 0 to -2.2 log. On the other hand, for steps of 0.05 log, the contrast was only reliable for values ranging from 0 to -1.7 log.

DISCUSSION

Both luminance and contrast steps differed between iPads with the same retina display, making it necessary to calibrate each display to achieve accurate luminance and contrast steps of 0.05 log units or less. However, for screening purposes utilizing contrast steps of 0.1 log unit or greater for a validated psychophysical test, calibration is not required to achieve accurate results across the displays described herein.

Biometry and visual function of a healthy cohort in Leipzig, Germany

Background

Cross-sectional survey of ocular biometry and visual function in healthy eyes across the life span of a German population aged 20 to 69 years (n = 218). Subject number in percent per age category reflected the percentage within the respective age band of the population of Leipzig, Germany.

Methods

Measurements obtained: subjective and objective refraction, best-corrected visual acuity, accommodation, contrast sensitivity, topography and pachymetry with Scheimpflug camera, axial length with non-contact partial coherence interferometry, and spectral-domain optical coherence tomography of the retina. Pearson correlation coefficients with corresponding p-values were given to present interrelationships between stature, biometric and refractive parameters or their associations with age. Two-sample T-tests were used to calculate gender differences. The area under the logarithmic contrast sensitivity function (AULCSF) was calculated for the analysis of contrast sensitivity as a single figure across a range of spatial frequencies.

Results

The results of axial length (AL), anterior chamber depth (ACD) and anterior chamber volume (ACV) differed as a function of the age of the participants (rho (p value): AL −0.19 (0.006), ACD −0.56 (< 0.001), ACV-0.52 (< 0.001)). Longer eyes had deeper ACD (AL:ACD 0.62 (< 0.001), greater ACV (AL:ACV 0.65 (< 0.001) and steeper corneal radii (AL:R1ant; R2ant; R1post; R2post 0.40; 0.35; 0.36; 0.36 (all with (< 0.001)). Spherical equivalent was associated with age (towards hyperopia: 0.34 (< 0.001)), AL (−0.66 (< 0.001)), ACD (−0.52 (< 0.001)) and ACV (−0.46 (< 0.001)). Accommodation was found lower for older subjects (negative association with age, r = −0.82 (< 0.001)) and contrast sensitivity presented with smaller values for older ages (AULCSF −0.38, (< 0.001)), no change of retinal thickness with age. 58 % of the study cohort presented with a change of refractive correction above ±0.50 D in one or both eyes (64 % of these were habitual spectacle wearers), need for improvement was present in the young age-group and for older subjects with increasing age.

Conclusion

Biometrical data of healthy German eyes, stratified by age, gender and refractive status, enabled cross-comparison of all parameters, providing an important reference database for future patient-based research and specific in-depth investigations of biometric data in epidemiological research.

Trial registration

ClinicalTrials.gov # NCT01173614 July 28, 2010

Impact of Low Mesopic Contrast Sensitivity Outcomes in Different Types of Modern Multifocal Intraocular Lenses

Purpose

To investigate the low mesopic contrast sensitivity function (LMCSF) of patients implanted with different modern optical bifocal and trifocal designs of multifocal intraocular lenses (mfIOLs).

Methods

This prospective, comparative, nonrandomized consecutive case series included 180 eyes that underwent cataract surgery. Six groups of eyes were differentiated: group A, eyes with the diffractive AT LISA tri 839MP; group B, eyes with diffractive FineVision; group C, eyes with the bifocal Lentis Mplus-LS313; group D, eyes with the diffractive bifocal Acri.Lisa 366D; group E, eyes with the diffractive apodized Acrysof ReSTOR SN6AD1; group F, as the control group, implanted with a monofocal spherical intraocular lens. The LMCSF was evaluated with the OPTEC® 6500 device at 3 months postoperatively using a luminance of 3 cd/m2.

Results

No significant differences among groups were detected in LMCSF for the spatial frequencies of 1.5, 3.0, 6.0, and 12.0 cpd (1.5 cpd: F = 1.81, p = 0.13; 3.0 cpd: F = 1.14, p = 0.14; 6.0 cpd: F = 1.87, p = 0.11; 12.0 cpd: F = 1.26, p = 0.29), but significant differences were found among groups for the spatial frequency of 18 cpd (F = 2.62, p = 0.03). When comparing the groups in pairs, only statistically significant differences were observed between groups E and F for the spatial frequency of 18.0 cpd (t = 3.27, p = 0.03) with better values for group F.

Conclusion

No significant differences were observed in LMCSF among the different mfIOLs studied. The third focus of trifocal IOL models did not adversely affect the LMCSF. The ReSTOR SN6AD1 showed the poorest LMCSF for the highest spatial frequency analyzed when compared with the control group.

Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts As Visual Acuity Measurement Devices

Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer's recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards.

Trifocal Intraocular Lens Implantation to Treat Visual Demands in Various Distances Following Lens Removal

PURPOSE

To evaluate visual and refractive outcomes after implantation of a trifocal intraocular lens (IOL).

DESIGN

Prospective, nonrandomized noncomparative case series.

METHODS

setting: Department of Ophthalmology, Goethe University, Frankfurt/Germany. patient or study population: Twenty-seven patients (54 eyes) who had bilateral implantation of the AT LISA trifocal IOL (AT LISA tri839MP; Carl Zeiss Meditec, Jena, Germany) pre-enrollment. Exclusion criteria were previous ocular surgeries excluding cataract surgery and refractive lens exchange, irregular corneal astigmatism of >1.5 diopter, and ocular pathologies or corneal abnormalities. Intervention or Observation Procedure(s): Postoperative examination at 1 and 3 months included manifest refraction; monocular and binocular uncorrected (UCVA) and distance-corrected (DCVA) visual acuity in 4 m, 80 cm, and 40 cm; slit-lamp examination; and tomography. At 3 months defocus testing, binocular contrast sensitivity (CS) under photopic and mesopic conditions, and a questionnaire on subjective quality of vision, optical phenomena, and spectacle independence were performed.

MAIN OUTCOME MEASURE(S)

Three-months-postoperative monocular and binocular UCVA and DCVA in 4 m, 80 cm, and 40 cm (logMAR); defocus curve; CS; and quality-of-vision questionnaire results.

RESULTS

Mean spherical equivalent was 0.05 ± 0.32 D 3 months postoperatively. Binocular UCVA at distance, intermediate, and near was -0.1 ± 0.1 logMAR, 0.0 ± 0.1 logMAR, and 0.0 ± 0.1 logMAR, respectively. Despite some optical phenomena, 92% of patients would choose the same IOL again.

CONCLUSION

Evaluation of a trifocal IOL showed good VA (0.1 logMAR or better) at far, intermediate, and near distance; high patient satisfaction despite some optical phenomena; and high spectacle independence 3 months postoperatively.

Evaluating the performance of the quick CSF method in detecting contrast sensitivity function changes

The contrast sensitivity function (CSF) has shown promise as a functional vision endpoint for monitoring the changes in functional vision that accompany eye disease or its treatment. However, detecting CSF changes with precision and efficiency at both the individual and group levels is very challenging. By exploiting the Bayesian foundation of the quick CSF method (Lesmes, Lu, Baek, & Albright, 2010), we developed and evaluated metrics for detecting CSF changes at both the individual and group levels. A 10-letter identification task was used to assess the systematic changes in the CSF measured in three luminance conditions in 112 naïve normal observers. The data from the large sample allowed us to estimate the test-retest reliability of the quick CSF procedure and evaluate its performance in detecting CSF changes at both the individual and group levels. The test-retest reliability reached 0.974 with 50 trials. In 50 trials, the quick CSF method can detect a medium 0.30 log unit area under log CSF change with 94.0% accuracy at the individual observer level. At the group level, a power analysis based on the empirical distribution of CSF changes from the large sample showed that a very small area under log CSF change (0.025 log unit) could be detected by the quick CSF method with 112 observers and 50 trials. These results make it plausible to apply the method to monitor the progression of visual diseases or treatment effects on individual patients and greatly reduce the time, sample size, and costs in clinical trials at the group level.

Index of contrast sensitivity (ICS) in pseudophakic eyes with different intraocular lens designs

PURPOSE

To evaluate the index of contrast sensitivity (ICS) in eyes after cataract surgery with various intraocular lens designs and to compare with the area under log contrast sensitivity curve (AULCSF).

METHODS

The study comprised 395 eyes of 198 patients in the age of 73.1 ± 7.86 years receiving 11 different aspheric IOL designs (aberration-free and correcting) and a spherical (IOL) as control group. Follow-up examination after bilateral cataract surgery was completed within 71 ± 21.4 days after second IOL implantation. Patients underwent complete examination and biometry before surgery. The follow-up examination included visual acuity, pupil diameter, residual spherical aberration and mesopic as well as photopic contrast sensitivity (CS) measured with the Optec 6500 Functional Vision Analyzer. From the contrast sensitivity, we calculated the ICS according to Haughom and Strand.

RESULTS

The median mesopic ICS was -144, -131 and -85, and the median photopic ICS was -289, -285 and -212 for the spherical, aberration-free and aberration-correcting IOL group, respectively. While we could not detect a significant difference between the aberration groups in some spatial frequencies, the ICS showed a significant difference between the aberration-correcting and the aberration-free or the spherical group, respectively. No significant difference was found between the aberration-free and the spherical group.

CONCLUSIONS

The ICS is a useful index for evaluation of overall CS and comparison of different patient groups. With aberration-correcting IOLs, ICS was statistically better than with aberration-free or spherical IOLs, whereas the latter two showed no significant difference.

Contrast sensitivity measured by two different test methods in healthy, young adults with normal visual acuity

PURPOSE

This study reports contrast sensitivity (CS) reference values obtained by two different test methods in a strictly selected population of healthy, young adults with normal uncorrected visual acuity. Based on these results, the index of contrast sensitivity (ICS) is calculated, aiming to establish ICS reference values for this population and to evaluate the possible usefulness of ICS as a tool to compare the degree of agreement between different CS test methods.

METHODS

Military recruits with best eye uncorrected visual acuity 0.00 LogMAR or better, normal colour vision and age 18-25 years were included in a study to record contrast sensitivity using Optec 6500 (FACT) at spatial frequencies of 1.5, 3, 6, 12 and 18 cpd in photopic and mesopic light and CSV-1000E at spatial frequencies of 3, 6, 12 and 18 cpd in photopic light. Index of contrast sensitivity was calculated based on data from the three tests, and the Bland-Altman technique was used to analyse the agreement between ICS obtained by the different test methods.

RESULTS

A total of 180 recruits were included. Contrast sensitivity frequency data for all tests were highly skewed with a marked ceiling effect for the photopic tests. The median ICS for Optec 6500 at 85 cd/m2 was -0.15 (95% percentile 0.45), compared with -0.00 (95% percentile 1.62) for Optec at 3 cd/m2 and 0.30 (95% percentile 1.20) FOR CSV-1000E. The mean difference between ICSFACT 85 and ICSCSV was -0.43 (95% CI -0.56 to -0.30, p<0.00) with limits of agreement (LoA) within -2.10 and 1.22. The regression line on the difference of average was near to zero (R2=0.03).

CONCLUSION

The results provide reference CS and ICS values in a young, adult population with normal visual acuity. The agreement between the photopic tests indicated that they may be used interchangeably. There was little agreement between the mesopic and photopic tests. The mesopic test seemed best suited to differentiate between candidates and may therefore possibly be useful for medical selection purposes.

Ultrasound-based quantification of vitreous floaters correlates with contrast sensitivity and quality of life

PURPOSE

Clinical evaluation of floaters lacks quantitative assessment of vitreous structure. This study used quantitative ultrasound (QUS) to measure vitreous opacities. Since floaters reduce contrast sensitivity (CS) and quality of life (Visual Function Questionnaire [VFQ]), it is hypothesized that QUS will correlate with CS and VFQ in patients with floaters.

METHODS

Twenty-two eyes (22 subjects; age = 57 ± 19 years) with floaters were evaluated with Freiburg acuity contrast testing (FrACT; %Weber) and VFQ. Ultrasonography used a customized probe (15-MHz center frequency, 20-mm focal length, 7-mm aperture) with longitudinal and transverse scans taken in primary gaze and a horizontal longitudinal scan through premacular vitreous in temporal gaze. Each scan set had 100 frames of log-compressed envelope data. Within each frame, two regions of interest (ROIs) were analyzed (whole-central and posterior vitreous) to yield three parameters (energy, E; mean amplitude, M; and percentage of vitreous filled by echodensities, P50) averaged over the entire 100-frame dataset. Statistical analyses evaluated E, M, and P50 correlations with CS and VFQ.

RESULTS

Contrast sensitivity ranged from 1.19%W (normal) to 5.59%W. All QUS parameters in two scan positions within the whole-central ROI correlated with CS (R > 0.67, P < 0.001). P50 in the nasal longitudinal position had R = 0.867 (P < 0.001). Correlations with VFQ ranged from R = 0.52 (P < 0.013) to R = 0.65 (P < 0.001).

CONCLUSIONS

Quantitative ultrasound provides quantitative measures of vitreous echodensity that correlate with CS and VFQ, providing objective assessment of vitreous structure underlying the functional disturbances induced by floaters, useful to quantify vitreous disease severity and the response to therapy.

Past and present of corneal refractive surgery: a retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction

Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become possible. Two new procedures were developed, ReLEx flex (FLEX) and ReLEx smile (SMILE). Until this thesis, only a few long-term studies of PRK with a relatively limited number of patients had been published; therefore, this thesis intended to retrospectively evaluate long-term outcomes after PRK for all degrees of myopia for a large number of patients. Furthermore, a prospective contralateral eye study comparing FLEX and SMILE, when treating high to moderate degrees of myopia, had not been performed prior to this study. This was the second aim of this thesis. In the first study, results from 160 PRK patients (289 eyes) were presented. Preoperative spherical equivalent ranged from -1.25 to -20.25 D, with 78% having low myopia (<-6 D). Average follow-up time was 16 years (range 13-19 years), making this the longest published follow-up study on PRK patients. Outcomes from eyes with low myopia were generally superior to outcomes from eyes with high myopia, at final follow-up. Seventy-two percent were within ± 1.00 D of target refraction, as compared to 47% of eyes with high myopia. However, results from a subgroup of unilateral treated PRK patients indicated that refraction at final follow-up was affected by myopic progression. Fifty percent of eyes with low myopia had uncorrected 20/20 distance visual acuity or better, as compared to 22% of eyes with high myopia. Haze did not occur if attempted corrections were <-4 D, and only eyes with high myopia lost two lines or more of CDVA (corrected distance visual acuity). Eighty-one per cent were satisfied or very satisfied with their surgery.

CONCLUSION

The results support the continued use of the excimer laser for corneal surface ablation as a treatment option for correction of low degrees of myopia, and as the treatment of choice for subgroups of refractive patients (thin corneas, etc.). The results also highlight that treatment of higher degrees of myopia with standard PRK should only be done today under special circumstances, due to low refractive predictability, and high risk of corneal haze. Technological advances since then should be taken into account when comparing these results with contemporary techniques. In the second study, 35 patients were randomized to receive FLEX in one eye and SMILE in the other. Preoperative spherical equivalent refraction ranged from -6 to -10 D with low degrees of astigmatism. A total of 34 patients completed the 6 month follow-up period. Refractive and visual outcomes were very similar for the two methods, as well as tear film measurements and changes in corneal biomechanics. Ninety-seven percent were within ± 1.00 D of target refraction, no eyes lost two lines or more of CDVA, and contrast sensitivity was unaffected after both procedures. The changes in higher-order aberrations were also very similar. There were also no differences in tear film parameters 6 months after surgery, although less postoperative foreign body sensation was reported within the first week after surgery in SMILE eyes. Corneal sublayer pachymetry measurements demonstrated equally increased epithelial thickness 6 months after surgery. Contrary to expectations, it was not possible to measure the theoretical biomechanical advantages of a small corneal incision in SMILE as compared to a corneal flap in FLEX. The main differences between FLEX and SMILE were found when the corneal nerves and intraoperative complications were evaluated. Thus, corneal sensitivity was better preserved and corneal nerve morphology was less affected after SMILE, but intraoperative complications occurred more frequently, although without visual sequela. Finally, 97% were satisfied or very satisfied with both their surgeries.

CONCLUSION

The results support the continued use of both FLEX and SMILE for treatment of up to high degrees of myopia. Overall, refractive and visual results for both procedures were good and similar, but from a biological point of view, the less invasive SMILE technique is more attractive, as demonstrated in this study, despite being slightly more surgically demanding than FLEX.

The impact on vision of aspheric to spherical monofocal intraocular lenses in cataract surgery: a systematic review with meta-analysis

PURPOSE

To provide a summary of the impact on vision of an aspheric intraocular lens (IOL) compared with a spherical IOL in cataract surgery.

DESIGN

Systematic review with meta-analysis.

PARTICIPANTS

Patients from published randomized controlled trials (RCTs) of cataract surgery with aspheric compared with spherical monofocal IOL implantation.

METHODS

We systematically searched the peer-reviewed literature in MEDLINE, EMBASE, Web of Science, BIOSIS, and the Cochrane Library according to the Cochrane Collaboration method to identify relevant RCTs. The inclusion criteria were RCTs on cataract surgery comparing the use of aspheric versus spherical IOL implantation that assessed visual acuity, contrast sensitivity, or quality of vision. The effects were calculated as mean differences or standardized mean differences (Hedges' g) and pooled using random-effect models.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), contrast sensitivity, and subjective perception of the quality of vision.

RESULTS

Forty-three studies provided data and were included, comprising 2076 eyes implanted with aspheric IOLs and 2034 eyes implanted with spherical IOLs. The BCVA showed a significant difference for aspheric IOLs (-0.01 logarithm of the minimum angle of resolution; 95% confidence interval [CI], -0.02 to -0.00). For contrast sensitivity, a significant advantage for aspheric IOLs was found under photopic and mesopic light conditions (photopic: Hedges' g 0.42, 95% CI 0.24-0.61 (3 cycles per degree [cpd]) to 0.53, 95% CI 0.33-0.73 (12 cpd); mesopic: Hedges' g 0.49, 95% CI 0.23-0.75 (1.5 cpd) to 0.76, 95% CI 0.52-1.00 (18 cpd)). Questionnaires targeting the subjective perception of quality of vision yielded less conclusive results.

CONCLUSIONS

Overall, a patient may achieve better contrast sensitivity with an aspheric IOL than with a spherical IOL, especially under dim light. There was no clinically relevant difference in BCVA between aspheric and spherical IOL implantation. The findings on the subjective perception of visual quality were heterogeneous with no clear result favoring either option.

Sine wave mesopic contrast sensitivity -- defining the normal range in a young population

PURPOSE

Limited information is available regarding the normal range of mesopic sine wave contrast sensitivity (CS). The aim of this study was therefore to define a reference range and in addition to identify factors related to mesopic CS in a young population.

METHODS

Individuals with normal visual acuity (VA) were included from a population of air crew members visiting the Institute of Aviation Medicine for routine medical examinations. CS was measured using the Optec 6500/FACT and evaluated by (i) the CS curve with five frequencies and (ii) the index of contrast sensitivity (ICS). ICS was defined as the sum of the weighted differences from the median CS value for each frequency. Multivariate analyses were performed to identify factors related to CS.

RESULTS

In a total of 197 subjects included, the mean mesopic CS score was significantly lower compared to the corresponding photopic measurements for all five frequencies tested. Median CS score for frequencies 1.5, 3, 6, 12 and 18 cycles per degree was 50, 114, 180, 60 and 33 for photopic and 71, 80, 90, 22 and 12 for mesopic (- glare) conditions, respectively. Better binocular VA was positively associated, while the use of corrective lenses was negatively associated with CS performance.

CONCLUSION

We have provided reference values for mesopic CS and identified factors important for CS. The difference between mesopic and photopic measurements highlights the need for separate population norms. The new ICS score may be a useful collective descriptor of the traditional CS curve with five frequencies.

Reliability of the CSV-1000 in adults and children

PURPOSE

Test-retest reliability of the CSV-1000 (Vector Vision) has only been reported for one adult sample. We measured the reliability of this instrument in both children and adults and also investigated the effect of changing the examiner on test-retest reliability.

METHODS

Test-retest log contrast sensitivity (CS) measurements were obtained for 19 young adults and 15 children by the same examiner. Test-retest log CS data were obtained from 21 young adults with different examiners. Reliability was calculated using the Bland-Altman limits of agreement, the coefficient of repeatability (COR), and the intraclass correlation coefficient.

RESULTS

All three estimates of reliability for the CSV-1000 chart are low for both children and adults using the standard recommended testing protocol. If the test-retest log CS data are obtained from the same examiner then the reliability is improved, but not significantly so.

CONCLUSIONS

The reliability of the CSV-1000 is low, even if the same examiner obtains test-retest data. The data indicate that this test is unlikely to be sensitive enough to provide useful information for the clinician as is, but we suggest modifications of the procedure that may significantly increase test reliability.

Visual acuity and contrast sensitivity after posterior lamellar keratoplasty

PURPOSE

It has previously been reported that patients who suffer from Fuchs' endothelial dystrophy (Fuchs' ED) have decreased contrast sensibility threshold. The removal of endothelial guttata by Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) surgery has also been demonstrated to decrease intraocular light scatter and improve contrast thresholds. The purpose of this study was to compare different visual qualities in patients that had undergone DSAEK surgery in one eye while having untreated Fuchs' dystrophy in the other eye.

METHODS

Thirty-two eyes of 16 patients with bilateral Fuchs' ED who had DSAEK surgery performed in one eye were enrolled. Visual acuity at 100% contrast and contrast sensitivity (CS) as evaluated by a modified simulation of the Freiburg Acuity and Contrast Test, was measured in both eyes of each patient.

RESULTS

  Snellen visual acuity improved in treated eyes from 0.66 ± 0.35 (SD) before surgery to 0.38 ± 0.18 after surgery (log MAR units; p < 0.01). In eyes with untreated Fuchs' dystrophy, visual acuity was 0.46 ± 0.14. In a pairwise comparison, there was no difference in Snellen visual acuity between treated and nontreated eyes (p = 0.12). Contrast sensitivity was significantly better in DSAEK-treated eyes compared with untreated eyes. Mean log CS in DSAEK-treated eyes was 1.06 ± 0.25 compared with a mean log CS of 0.84 ± 0.16 in untreated eyes (p < 0.01). Fourteen of 16 patients (88%) reported that vision in their DSAEK-treated eye had the best visual quality.

CONCLUSION

In this study, using a paired design, we demonstrate improved CS in DSAEK-operated eyes when compared with the other eye that had untreated Fuchs' ED despite the fact that no difference in visual quality was detected with standard Snellen visual acuity. Contrast sensitivity appears to be superior to normal visual acuity measurements in the evaluation of overall visual quality after DSAEK.

Grating acuity and contrast tests for clinical trials of severe vision loss

PURPOSE

To evaluate the reliability and validity of grating visual acuity (VA) and contrast sensitivity (CS) tests, which could be useful outcome measures to assess changes in severely reduced vision.

METHODS

The Grating Acuity Test (GAT) and Grating Contrast Sensitivity (GCS) tests, which involve the detection of grating orientation in a four-Alternative Forced Choice paradigm on a liquid crystal display screen, were compared with the well-validated Early Treatment of Diabetic Retinopathy Study (ETDRS) and Pelli-Robson (PR) charts. Grating tests were repeated two or three times within-visit, across three or four sessions, in 20 legally blind subjects: 8 with retinitis pigmentosa (RP) (16 eyes) and 12 with other retinal diseases (OR) (16 eyes).

RESULTS

VA determined by ETDRS and GAT was in good agreement and scaled very similarly, as shown by regression of the within-session difference between the two measures against their mean [RP group: slope (m) = 0.11; 95% confidence interval [CI]: -0.06, 0.29; p = 0.21; OR group: m = -0.07; 95% CI: 0.33, 0.20; p = 0.62]. On average, higher logCS levels were obtained using the GCS than the PR in both groups. The two CS measures scaled similarly in the RP group (m = 0.07; 95% CI: -0.09, 0.22; p = 0.39) but not in the OR group (m = 0.41; 95% CI: 0.12, 0.70; p = 0.005). The within- and between-visit 95% coefficient of repeatability (CR.95) were 0.11 to 0.17 log units for the ETDRS charts and GAT in both groups and 0.14 to 0.15 log units for the PR and GCS in the RP group, whereas the OR group demonstrated more variability in CS. Between-visit CR.95 did not significantly change with mean VA or CS for the ETDRS, PR, or GCS tests, but RP patients' CR.95 on the GAT increased significantly with decreasing VA. Floor effects occurred for some RP eyes with ETDRS and PR charts but not with the GAT and GCS.

CONCLUSIONS

Computer-driven grating tests appear to be reliable, capable of evaluating vision that may fall outside of the range of standard clinical tests and may be useful during clinical trials for advanced eye disease.

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.

Ocular motor and sensory function in Parkinson's disease

PURPOSE

To evaluate the effect of dopaminergic medication and deep brain stimulation on ocular function in Parkinson's disease (PD) and to measure vision-related quality of life in subjects with PD.

DESIGN

Prospective, comparative case series.

PARTICIPANTS AND CONTROLS

Twenty-seven PD and 16 control subjects were recruited.

METHODS

Visual acuity, ocular motor function, convergence, and vision-related quality of life using the 25-item National Eye Institute Visual Function Questionnaire (VFQ-25) were measured. Visual sensory and motor measurements were obtained during the on and off states of PD dopaminergic treatment.

MAIN OUTCOME MEASURES

Convergence ability and vision-related quality of life.

RESULTS

The PD subjects had a mean age of 58.8 years; 30% were female. Their mean duration of PD was 10.9 ± 6.8 years. The control subjects had a mean age of 61.6 years; 56% were female. There was no difference in visual acuity, contrast sensitivity, or color vision of the PD subjects in their on state compared with controls. Convergence amplitudes measured with base-out prism were significantly poorer in PD subjects in their on state compared with controls (24.1 ± 8 Δ vs. 14.8 ± 10.3 Δ; P = 0.003). The mean composite VFQ-25 score was significantly worse in the PD subjects compared with the controls (87.1 ± 8.69 vs. 96.6 ± 3.05; P = 0.0001). Comparing the PD subjects in their on with their off states, there was no difference in distance exodeviation, near exodeviation, or ocular ductions. Mean convergence amplitudes and near point of convergence were better in the on state compared with the off state: 14.8 ± 10.3 Δ versus 10.7 ± 9.0 Δ (P = 0.0006) and 13.1 ± 9.1 cm versus 18.1 ± 12.2 cm (P = 0.002), respectively.

CONCLUSIONS

Convergence ability is significantly poorer in PD subjects in both the on and off states compared with controls, but improves significantly with systemic dopaminergic treatment. Ocular motor function in PD subjects fluctuates in response to treatment, which complicates ophthalmic management. Parkinson's disease subjects have a significant reduction in vision-related quality of life, especially with near activities, that is not associated with visual acuity.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Visual contrast sensitivity in children exposed to tetrachloroethylene

This study examined relationships between indoor air, breath, and blood tetrachloroethylene (perc) levels and visual contrast sensitivity (VCS) among adult and child residents of buildings with or without a colocated dry cleaner using perc. Decreasing trends in proportions of adults or children with maximum VCS scores indicated decreased VCS at a single spatial frequency (12 cycles per degree [cpd]) among children residing in buildings with colocated dry cleaners when indoor air perc level averaged 336 μg/m³; breath perc level averaged 159.5 μg/m³; and blood perc level averaged 0.51 μg/L. Adjusted logistic regression indicated that increases in indoor air, breath, and blood perc levels among all child participants significantly increased the odds for decreased VCS at 12 cpd. Adult VCS was not significantly decreased by increasing indoor air, breath, or blood perc level. These results suggest that elevated residential perc exposures may alter children's VCS, a possible subclinical central nervous system effect.

qCSF in clinical application: efficient characterization and classification of contrast sensitivity functions in amblyopia

PURPOSE

The qCSF method is a novel procedure for rapid measurement of spatial contrast sensitivity functions (CSFs). It combines Bayesian adaptive inference with a trial-to-trial information gain strategy, to directly estimate four parameters defining the observer's CSF. In the present study, the suitability of the qCSF method for clinical application was examined.

METHODS

The qCSF method was applied to rapidly assess spatial CSFs in 10 normal and 8 amblyopic participants. The qCSF was evaluated for accuracy, precision, test-retest reliability, suitability of CSF model assumptions, and accuracy of amblyopia screening.

RESULTS

qCSF estimates obtained with as few as 50 trials matched those obtained with 300 Ψ trials. The precision of qCSF estimates obtained with 120 and 130 trials, in normal subjects and amblyopes, matched the precision of 300 Ψ trials. For both groups and both methods, test-retest sensitivity estimates were well matched (all R > 0.94). The qCSF model assumptions were valid for 8 of 10 normal participants and all amblyopic participants. Measures of the area under log CSF (AULCSF) and the cutoff spatial frequency (cutSF) were lower in the amblyopia group; these differences were captured within 50 qCSF trials. Amblyopia was detected at an approximately 80% correct rate in 50 trials, when a logistic regression model was used with AULCSF and cutSF as predictors.

CONCLUSIONS

The qCSF method is sufficiently rapid, accurate, and precise in measuring CSFs in normal and amblyopic persons. It has great potential for clinical practice.

Bayesian adaptive estimation of the contrast sensitivity function: the quick CSF method

The contrast sensitivity function (CSF) predicts functional vision better than acuity, but long testing times prevent its psychophysical assessment in clinical and practical applications. This study presents the quick CSF (qCSF) method, a Bayesian adaptive procedure that applies a strategy developed to estimate multiple parameters of the psychometric function (A. B. Cobo-Lewis, 1996; L. L. Kontsevich & C. W. Tyler, 1999). Before each trial, a one-step-ahead search finds the grating stimulus (defined by frequency and contrast) that maximizes the expected information gain (J. V. Kujala & T. J. Lukka, 2006; L. A. Lesmes et al., 2006), about four CSF parameters. By directly estimating CSF parameters, data collected at one spatial frequency improves sensitivity estimates across all frequencies. A psychophysical study validated that CSFs obtained with 100 qCSF trials ( approximately 10 min) exhibited good precision across spatial frequencies (SD < 2-3 dB) and excellent agreement with CSFs obtained independently (mean RMSE = 0.86 dB). To estimate the broad sensitivity metric provided by the area under the log CSF (AULCSF), only 25 trials were needed to achieve a coefficient of variation of 15-20%. The current study demonstrates the method's value for basic and clinical investigations. Further studies, applying the qCSF to measure wider ranges of normal and abnormal vision, will determine how its efficiency translates to clinical assessment.

Determinants of contrast sensitivity for the tumbling E and Landolt C

PURPOSE

To compare the object spatial frequencies that underlie contrast sensitivity for the tumbling E and Landolt C across a range of optotype sizes and under conditions biased toward the magnocellular (MC) and parvocellular (PC) pathways.

METHODS

Contrast thresholds of two visually normal observers were measured using tumbling E optotypes that were either low-pass filtered or high-pass filtered with a two-dimensional Gaussian filter. Optotypes were presented using steady-pedestal and pulsed-pedestal paradigms to target the MC and PC pathways, respectively. Object frequencies essential for orientation judgments of the tumbling E were derived from plots of log contrast threshold vs. log filter cutoff frequency, and results were compared with those obtained previously for the Landolt C under identical testing conditions.

RESULTS

The object frequency used to judge the orientation of the tumbling E increased systematically with increasing target angular subtense, and the effect of target size differed depending on whether performance was mediated by the inferred MC or PC pathway. The overall pattern of results was similar for the tumbling E and Landolt C, but there was generally less dependence of object frequency on target angular subtense for the tumbling E.

CONCLUSIONS

The tumbling E and Landolt C are not equivalent in terms of the object frequencies that mediate orientation judgments. However, both optotypes show scale-dependent changes in object frequency, particularly under test conditions that favor the PC pathway. The scale dependence of these broadband optotypes can pose a challenge in interpreting test results using these targets. A potential solution is to use spatially filtered optotypes with limited, known object frequency content.

The association between various visual function tests and low fragility hip fractures among the elderly: a Malaysian experience

BACKGROUND

hip fractures are an increasing source of morbidity and mortality in older people. The role of visual function tests such as visual impairment, stereopsis, contrast sensitivity and visual field defects in low fragility hip fractures in Asian populations is not well understood.

OBJECTIVE

to determine the association between various visual function tests and low fragility hip fractures in an Asian population.

DESIGN

case-control study.

SETTING

University Malaya Medical Centre, Kuala Lumpur, Malaysia.

SUBJECTS

108 cases aged > or = 55 years admitted with low fragility fractures and 108 controls (matched for age, gender and race).

METHODS

both cases and controls underwent a detailed ophthalmological examination, which included visual acuity, stereopsis, contrast sensitivity and visual field testing.

RESULTS

poorer visual acuity (odds ratio, OR = 4.08; 95% confidence interval, CI: 1.44, 11.51), stereopsis (OR = 3.60, 95% CI: 1.55, 8.38), contrast sensitivity (OR = 3.34, 95% CI: 1.48, 7.57) and visual field defects (OR = 11.60, 95% CI: 5.21, 25.81) increased the risk of fracture. Increased falls were associated with poorer visual acuity (OR = 2.30, 95% CI: 1.04, 5.13), stereopsis (OR = 2.11, 95% CI: 1.03, 4.32), contrast sensitivity (OR = 2.12, 95% CI: 1.05, 4.30) and visual field defects (OR = 3.40, 95% CI: 1.69, 6.86).

CONCLUSION

impaired visual acuity, stereopsis, contrast sensitivity and visual field defects are associated with an increased risk of low fragility hip fractures. We recommend that all patients aged > or = 55 should have an annual ophthalmological examination that includes visual acuity, contrast sensitivity, stereopsis and visual field testing to assess the risks for falls and low fragility fractures.

Calibration tools for PC-based vision assessment

This paper details the research and development of the PC Vision system, a unique calibration and monitoring subsystem that will enable use of personal computers as accurately calibrated and controlled vision test instruments. The need for such a system is evident. Display intensity and chromaticity, test distance, room illumination, and a number of other variables must be controlled to avoid unexplained discrepancies in test outcomes, within and between individuals and test locations. Modern displays (CRT-, LCD-, or projector-based) have sufficient resolution, gamut, and stability to allow high-quality stimulus presentation. The PC Vision system consists of two categorical functions - one to calibrate screen properties, the other to monitor room and test setup conditions - packaged into a fully integrated hardware prototype.

Cataract surgery with implantation of an artificial lens

BACKGROUND

Cataract surgery, the most frequently performed operative procedure worldwide, typically concludes with the implantation of an artificial intraocular lens (IOL) to correct aphakia (absence of the crystalline lens).

METHOD

Selective literature review including current regulations, guidelines and recommendations for cataract surgery.

RESULTS

The main symptom of cataract is loss of visual acuity, which usually progresses slowly. It can arise in one eye or both. There is a basic distinction between congenital and acquired cataracts. The probability of developing a cataract rises with age because of biochemical aging processes. The development of a cataract becomes highly likely from the sixth decade of life onward.

CONCLUSIONS

As no effective medications for cataract are available at present, its current standard treatment is the removal of the clouded lens. In industrialized countries, this is usually done with ultrasound (phacoemulsification), followed by the implantation of an IOL.

Correlation of aberrometry, contrast sensitivity, and subjective symptoms with quality of vision after LASIK

PURPOSE

To compare which parameter category (wavefront data, psychophysical data, or subjective symptoms) predicts best subjective quality of vision after LASIK.

METHODS

Twenty-eight eyes (15 patients) were included. Twenty-three eyes (12 patients) underwent uneventful LASIK; 5 eyes (3 patients) were symptomatic eyes treated with myopic LASIK elsewhere. Mean preoperative spherical equivalent refraction was -4.79+/-1.92 diopters (D) (range: -1.63 to -7.13 D); mean patient age was 36.6+/-7.4 years (range: 18 to 48 years). All examinations were performed 1 month postoperatively. The wavefront error was described with Zernike polynomials (6-mm pupil). Psychophysical tests included high-contrast visual acuity and contrast sensitivity with and without glare at 167 cd/m(-2), 1.67 cd/m(-2), and 0.167 cd/m(-2) with best spectacle correction. Correspondingly, overall subjective quality of vision and frequency of visual symptoms (glare, halos, starbursts, ghosting, blur) were assessed for three lighting conditions (photopic, high-mesopic, and low-mesopic) using a questionnaire with a visual analog scale. For each parameter category and each lighting condition, a multiple stepwise backwards regression model with the overall quality of vision item value as dependent was applied.

RESULTS

Under all lighting conditions, subjective symptom scores predicted subjective quality of vision best (adjusted R2=0.83-0.92) with blur as the main predictor throughout all conditions. Psychophysical tests did not significantly predict postoperative subjective quality of vision. The adjusted R2 for the Zernike coefficients was highest for low-mesopic (0.56) and lowest for photopic conditions (0.31).

CONCLUSIONS

Different parameter categories for the description of optical quality did not predict subjective quality of vision after LASIK equally. Subjective symptom scores had the highest predictability, whereas psychophysical tests with spectacle correction had no predictability. The latter probably do not reflect all dimensions of subjective quality of vision.

Spatial frequencies used in Landolt C orientation judgments: relation to inferred magnocellular and parvocellular pathways

The purpose of this study was to define the spatial frequencies that underlie judgments of Landolt C orientation under test conditions designed to favor either the magnocellular (MC) or parvocellular (PC) pathway. Contrast thresholds of two observers were measured for briefly presented Landolt Cs of four sizes, using steady- and pulsed-pedestal paradigms to bias performance toward the MC and PC pathways, respectively. Contrast thresholds were derived from a two-alternative forced-choice orientation judgment task using the QUEST procedure. The Landolt Cs were either low-pass or high-pass Gaussian filtered with a range of cutoff object spatial frequencies (cycles per letter) to limit their frequency content. Center object frequencies were derived from plots of log contrast threshold for orientation judgments vs. log filter cutoff object frequency. The function relating center object frequency to Landolt C angular subtense was nonlinear on log-log coordinates for both the steady- and pulsed-pedestal paradigms, indicating that different object frequencies were used to judge Landolt C orientation at different optotype sizes. However, the function was substantially steeper under the pulsed-pedestal than under the steady-pedestal paradigm, such that a large change in optotype size produced a relatively small change in retinal spatial frequency (cycles per degree). The pattern of results is consistent with previously reported differences between the spatial contrast sensitivity functions of the inferred MC and PC pathways.

[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.

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.

Visual performance of aspherical and spherical intraocular lenses: Intraindividual comparison of visual acuity, contrast sensitivity, and higher-order aberrations

PURPOSE

To intraindividually compare visual performance in terms of photopic high-contrast visual acuity (HCVA), mesopic HCVA, mesopic low-contrast visual acuity (LCVA), and contrast sensitivity (CS) in patients after implantation of either an aspherical or a spherical intraocular lens (IOL).

SETTING

Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

METHODS

Forty eyes of 20 patients were randomized to implantation of an aspherical IOL (Tecnis Z9000, AMO) in 1 eye and a spherical IOL (Sensar AR40e, AMO) in the other eye. Three to 4 months postoperatively, photopic HCVA (270 cd/m(2)) was measured with the observer-independent Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) and high-mesopic HCVA and LCVA (8 cd/m(2)) were measured with Early Treatment Diabetic Retinopathy Study charts. CS was assessed with the FF-CATS under photopic (167 cd/m(2)), high-mesopic (1.67 cd/m(2)), and low-mesopic (0.167 cd/m(2)) luminance conditions with and without glare. For each individual eye, higher-order wavefront aberrations were reconstructed for a physiological mesopic pupil diameter. Intraindividual differences (Delta(i)) in visual acuity, contrast sensitivity, and higher-order aberrations (HOAs) were calculated, and the influence of age and Delta(i) HOA on Delta(i) contrast sensitivity (logCS) under high-mesopic conditions was investigated using multiple regression analysis.

RESULTS

There were no statistically significant differences between the Tecnis IOL and the Sensar IOL in visual acuity measurements or contrast sensitivity measurements. For physiological mesopic pupil diameter, primary spherical aberration (Z(4)(0)) was significantly lower in the Tecnis group (P<.001). For all parameters studied except Z(4)(0), the Delta(i) values were distributed around zero. Multiple regression analysis showed only a partial influence of Delta(i) Z(4)(0) on Delta(i) logCS (adjusted R(2) = 0.49) but did not show any influence of age, coma-like aberration, or residual HOA.

CONCLUSIONS

Although Z(4)(0) was significantly lower in the eyes with the aspherical IOL, no statistically significant differences were found between aspherical and spherical IOLs in LCVA, HCVA, and contrast sensitivity. Statistical analysis of intraindividual contrast sensitivity differences showed that in most patients, this Z(4)(0) difference was too low to have an effect on contrast sensitivity.