Ocular higher-order aberrations and contrast sensitivity after conventional laser in situ keratomileusis

PURPOSE: To investigate prospectively the relation between induced changes in higher-order aberrations of the eye and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 200 eyes of 110 consecutive patients (mean age, 32.7 +/- 8.4 years) undergoing LASIK, ocular aberrations and contrast sensitivity function were determined before and 1 month after surgery. The amount of myopic correction was 5.2 +/- 2.8 D (range, 1.0-13.0). Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer (KR-9000PW; Topcon, Tokyo, Japan). The root mean square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberrations, respectively. Total higher-order aberrations were calculated as the RMS of the third- and fourth-order coefficients. Contrast sensitivity and low-contrast visual acuity were measured. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: LASIK significantly improved logMAR best corrected visual acuity (Wilcoxon signed-rank test, P <0.001), but significantly reduced AULCSF (P <0.001) and low-contrast visual acuity (P=0.007). Total higher-order (P <0.001), coma-like (P <0.001), and spherical-like (P <0.001) aberrations were significantly increased after LASIK. The greater the amount of achieved myopia correction was, the more the changes in contrast sensitivity function and ocular higher-order aberrations were. The induced changes in AULCSF by LASIK showed significant correlations with changes in total higher-order (Pearson r=-0.221, P=0.003), coma-like (r=-0.205, P=0.006), and spherical-like (r=-0.171, P=0.022) aberrations. The changes in logMAR low-contrast visual acuity by surgery significantly correlated with changes in total higher-order (r=0.222, P=0.003), coma-like (r=0.201, P=0.007), and spherical-like (r=0.207, P=0.005) aberrations. CONCLUSIONS: Conventional LASIK significantly increases ocular higher-order aberrations, which compromise the postoperative contrast sensitivity function.     

Impact of visual function on computer task accuracy and reaction time in a cohort of patients with age-related macular degeneration

PURPOSE: To investigate the impact of visual function parameters on computer task performance in patients with age-related macular degeneration (AMD). DESIGN: Interventional case series. METHODS: Eighteen patients with visual impairment due to age-related macular degeneration underwent evaluation of visual acuity using the Early Treatment Diabetic Retinopathy Study protocol, contrast sensitivity using a Pelli-Robson chart, binocular simultaneous visual field using the Esterman program on an automated perimeter, and color vision using Farnsworth D-15. Each subject then completed 125 computer icon identification tasks. Relationships between computer task performance (accuracy and speed) and visual function parameters (visual acuity, contrast sensitivity, visual field, and color vision) were analyzed. RESULTS: Visual acuity and contrast sensitivity in the better eye, weighted average contrast sensitivity, and color vision defects are significantly associated with computer task accuracy. Visual acuity in the better eye, weighted average visual acuity, and color vision defects are significantly associated with performance speed. Visual function parameters and clinical features significantly associated with computer task accuracy in a multiple regression model include weighted average contrast sensitivity (P = 0.001), protan color vision defect (P = 0.002), cataract severity in the better-seeing eye (P = 0.036), and geographic atrophy outside the central macula (P = 0.046). Visual function parameters and clinical features significantly associated with computer task speed in a multiple regression model include color vision defects (deutan, P < 0.001; protan, P < 0.001) and gender (P = 0.05). CONCLUSIONS: Among this cohort of patients with AMD, visual acuity, contrast sensitivity, and color vision defects are significant predictors of computer task performance. Visual function parameters of the better eye played a more significant role than parameters of the worse eye, and contrast sensitivity is the most significant predictor of computer task accuracy.     

The Contrast Sensitivity Function in Low Vision

The contrast sensitivity of 51 low vision patients (95 eyes) showed a substantial decrease in all spatial frequencies. The peak contrast sensitivity was shifted to 1 C/D from the normal 3-4 C/D. The high-frequency cut off is correlated to the visual acuity positively. Of the 33 patients, the preferred eye was the eye with better peak sensitivity in 28 patients (84%), while the preferred eye was the eye with better visual acuity in 22 patients (66%). It seems that the peak sensitivity is more important than visual acuity in determining eye preference. It provides a useful information for the clinician to determine which eye to train with low vision aids. Forty patients among 46 patients (87%) with RFN (Recognized Frequency Number) >3 are able to read No.5 reading card, while 5 patients among 5 patients with RFN<3 are not able to read No.5 reading card. The contributions of CSF to the low vision are evaluated.     

Contrast sensitivity function and ocular higher-order aberrations following overnight orthokeratology

PURPOSE: To evaluate relationships among contrast sensitivity function, ocular higher-order aberration, and myopic correction in eyes undergoing overnight orthokeratology for myopia. METHODS: A prospective study was conducted in 46 eyes of 23 patients undergoing orthokeratology. Inclusion criteria were spherical equivalent refraction between -1.00 and -4.00 diopters (D), refractive astigmatism up to 1.00 D, and best-corrected visual acuity of 20/20 or better. Ocular higher-order aberrations and contrast sensitivity function were determined before and 3 months after initiation of the procedure. We measured three indices of contrast sensitivity function: contrast sensitivity, low-contrast visual acuity, and letter contrast sensitivity with the CSV-1000 charts (Vector Vision Co., Greenville, OH). Area under the log contrast sensitivity function (AULCSF) was calculated from the contrast sensitivity data. RESULTS: Orthokeratology significantly improved logMAR uncorrected visual acuity (P < 0.0001; paired t-test) but significantly increased ocular higher-order aberrations (P < 0.0001) and decreased contrast sensitivity function, including AULCSF (P < 0.0001), low-contrast visual acuity (P = 0.0025), and letter contrast sensitivity (P < 0.0001; Wilcoxon signed-rank test). The induced changes in AULCSF, low-contrast visual acuity, and letter contrast sensitivity by orthokeratology showed significant correlation with changes in third-order (Pearson r = -0.430, P = 0.0026; r = 0.423, P = 0.0031; and Spearman r(s) = -0.351, P = 0.0186, respectively), fourth-order (r = -0.418, P = 0.0035; r = 0.425, P = 0.0029; and r(s) = -0.566, P = 0.0001, respectively), and total higher-order (r = -0.460, P = 0.0011; r = 0.471, P = 0.0008; and r(s) = -0.434, P = 0.0036, respectively) aberrations. The induced changes in contrast sensitivity function and higher-order aberrations significantly correlated with the amount of myopic correction (P < 0.01). CONCLUSIONS: Orthokeratology significantly increases ocular higher-order aberrations and compromises contrast sensitivity function, depending on the amount of myopic correction.     

Is binocular contrast sensitivity at distance compromised with multifocal soft contact lenses used to correct presbyopia?

PURPOSE: The purpose of this investigation was to determine whether new experimental multifocal optical designs incorporating diffractive/refractive optics for correction of presbyopia in a soft contact lens would compromise binocular contrast sensitivity at distance while achieving 20/20 binocular visual acuity at near. METHODS: Thirty presbyopic volunteers were fitted with Acuvue Bifocal soft lenses, two (FO1 and 3B1) experimental diffractive/refractive multifocal soft lenses separately and in combination as a pair and soft spherical lenses. Visual performance was evaluated via binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity after 1 week of lens wear. RESULTS: The experimental lenses FO1 and the combination FO1/3B1 performed as well for binocular contrast sensitivity, binocular distance high-contrast visual acuity, and binocular distance low-contrast visual acuity as the habitual presbyopic correction and the spherical soft distance correction. A strong correlation (r = 0.73 and 0.53, respectively) was found between binocular contrast sensitivity and binocular distance low-contrast visual acuity with experimental FO1 and FO1/3B1 lenses. However, the correlation (r = 0.37 and 0.60, respectively) between binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity with FO1 was weaker than that with the combination FO1/3B1 lenses. Subjective responses support the objective data. DISCUSSION: The data show that experimental FO1 lens and the experimental combination of the FO1/3B1 lenses can be prescribed to not compromise distance binocular contrast sensitivity.     

Night driving self-restriction: vision function and gender differences.

PURPOSE: The purpose of this study was to evaluate gender differences in the relationship between night driving self-restriction and vision function in an older population. METHODS: Night driving self-restriction patterns (assessed by questionnaire) were examined cross-sectionally in relation to age, gender, health and cognitive status, depression, and vision function in a sample of 900 elders (mean age, 76 years) living in Marin County, California. RESULTS: Of the total sample, 91% of men and 77% of women were current drivers. The mean age of the drivers was 73.3 years (range, 58-96 years). Among current drivers, women had slightly better vision function than men on most measures (low-contrast acuity, contrast sensitivity, low-contrast acuity in glare, low-contrast, low-luminance acuity, and glare recovery) but were twice as likely as men to restrict their driving to daytime. Men showed significant associations with avoidance of night driving on four spatial vision measures (high- and low-contrast acuity, low-contrast, low-luminance acuity, and contrast sensitivity). For women, in addition to these measures, a significant association was seen for low-contrast acuity in glare. Neither men nor women showed significant associations between driving restriction and performance on the other vision measures examined (glare recovery time, attentional field integrity, or stereopsis). The vision measures most predictive of self-restriction were contrast sensitivity for men and low-contrast acuity in glare for women. CONCLUSIONS: Including both cessation and self-restriction, men over age 85 years are 6.6 times more likely than women to be driving at night. For both genders, vision plays a significant role in the self-restriction decision. A higher percentage of men than women continue to drive at night with poor vision. Men's night-driving cessation was associated with contrast sensitivity and depression, whereas women's night-driving cessation was associated with low-contrast acuity in glare as well as age.     

Binocular Summation and Control of Intermittent Exotropia

Background: Binocular summation (BiS), or improvement in binocular vision exceeding the better eye alone, is affected by strabismus. Being easily measured, BiS may be a useful indicator for subjective outcomes like stereopsis in strabismus. This study aims to investigate the relationship between BiS and measures of control of intermittent exotropia (IXT). Methods: Patients with IXT were recruited before undergoing strabismus surgery and underwent tests of binocular and monocular high- and low-contrast visual acuity, stereopsis at distance and near, and Newcastle Control Score (NCS), a score developed by incorporating home control and clinic control criteria into a control rating scale. BiS was calculated using high-contrast Early Treatment of Diabetic Retinopathy Study (ETDRS) and Sloan low-contrast acuity charts (LCA) at 2.5% and 1.25% contrast as the difference between the binocular score and that of the better eye. The relationship between BiS and measures of IXT control (NCS and distance near stereoacuity disparity) was evaluated using a correlation analysis by Spearman correlation coefficients and the Kruskal-Wallis test. Results: Thirty-four patients were included (mean [± standard deviation (SD)] age 19±16 years) having a mean (±SD) of 26±16Δ IXT at distance and 20±16Δ at near. Mean (±SD) BiS for ETDRS and Sloan LCA at 2.5% and 1.25% was 0.8±3.6, 1.9±6.0, and -2.3±7.2, respectively. The Spearman correlation coefficient of BiS and NCS was -0.53 (95% CI -0.85 to -0.25) for 2.5% LCA and -0.43 (95% CI -0.77 to -0.13) for 1.25% LCA. BiS at 2.5% LCA (P=0.006) and at 1.25% LCA (P=0.029) significantly differed between the groups based on NCS score groupings (1-3, 4-6, and 7-9), with patients who had better control scores having higher levels of BiS. BiS did not differ significantly between patients grouped according to the difference between stereoacuity measured at near versus distance. Conclusion: Significantly lower low-contrast BiS in patients with higher NCS may suggest that decreased BiS is associated with less control in IXT. This finding suggests that BiS may reflect control in IXT across a population of patients with IXT.     

Correlation of aberrations with visual acuity and symptoms

Standard refractive surgery (photorefractive keratectomy and laser in situ keratomileusis)induces optical changes in the wavefront aberrations of the eye. Higher-order optical changes are induced, especially spherical aberration and coma. Wavefront sensing performed after refractive surgery has revealed a decrease in low-contrast acuity and contrast sensitivity, comprising the patient's night vision and leading to symptoms such as halos, starburst, and glare.     

Face recognition in the elderly.

PURPOSE: The purpose of this study was to assess face recognition ability in a large sample of elders (n=572, mean age=78.1 years) and to identify factors that affect performance. METHODS: Face recognition was measured by presenting standardized faces of varying sizes to simulate normal-sized faces at different viewing distances. Subjects were asked to identify the name of the person and their facial expression. Threshold equivalent viewing distance (EVD) was calculated. High- and low-contrast acuity, contrast sensitivity, low-contrast/low-luminance acuity, disability glare, stereoacuity, and visual field measures (with and without an attentional task) were also measured. These vision measures, along with demographic information (age, sex, education) and cognitive status, were included in a multiple regression analysis to determine which factors predicted task performance. RESULTS: This cross-sectional sample of elders showed significant declines in face recognition with age. Mean threshold EVD ranged from 8.0 m for participants相似文献   

Effect of a modified optic edge design on visual function: textured-edge versus round-anterior, slope-side edge

PURPOSE: To compare the impairment in visual function caused by glare with 2 acrylic intraocular lenses (IOLs) with different modified optic edges. SETTING: Hayashi Eye Hospital, Fukuoka, Japan. METHODS: Fifty-four patients had implantation of an IOL with a textured edge (Alcon MA60AC) in 1 eye and an IOL with a round-anterior, sloped-sided edge (AMO AR40e) in the opposite eye. Visual acuity was measured at 5 contrast visual targets (100%, 25%, 10%, 5%, and 2.5%) (contrast visual acuity) under photopic and mesopic conditions with and without a glare source approximately 1 month after surgery using the Contrast Sensitivity Accurate Tester (Menicon CAT-2000). RESULTS: The mean mesopic contrast visual acuity at moderate- to low-contrast visual targets was significantly worse in the presence of a glare source in both groups, whereas photopic contrast visual acuity did not change significantly. There were no significant differences between the 2 groups in the mean visual acuity or in photopic or mesopic lighting contrast visual acuity with and without a glare source. Furthermore, there was no significant difference in loss of contrast visual acuity in the presence of glare. CONCLUSION: Mesopic contrast sensitivity with both acrylic IOLs was impaired significantly in the presence of glare, but the impairment of contrast sensitivity from glare was approximately the same between eyes with a textured-edge IOL and eyes with a round-anterior, sloped-sided edge IOL.     

Bioptics mit Multifokallinsen und Lasek

Purpose

Good functional results with multifocal lenses need exact postoperative emmetropia. Therefore, it seems reasonable to perform additional refractive surgery to correct minimal spherical or cylindrical postoperative ametropia (bioptics). But concerns could arise about additional photoptic phenomena or loss of contrast. The literature contains only a few reports about bioptics after multifocal lens implantation.

Method

In eight eyes of seven patients, laser subepithelial keratomileusis (Lasek) was done after multifocal lens implantation. Pre-Lasek and 6 months postoperatively, we performed the following examinations in addition to visual acuity: contrast sensitivity (Pelli–Robson charts), low-contrast visual acuity (Humphrey AR 570), glare visual acuity (Humphrey AR 570), and night-driving ability (Mesoptometer II, Oculus).

Results

Preoperative contrast sensitivity was 1.2–1.65; postoperatively it was 1.35–1.65. Low-contrast visual acuity measured 50–70% preoperatively and 57–70% postoperatively. Glare visual acuity measured 12.5–50% preoperatively and 28.5–57% postoperatively. Mesoptometer measurements did not change after Lasek; they revealed night-driving ability under strict criteria for four patients.

Conclusions

Bioptics as a combination of multifocal lens implantation and Lasek does not cause a functional decline in low-contrast or glare visual acuity, but it minimizes postoperative ametropia. It seems superior to exclusive multifocal lens implantation.     

Global shape discrimination at reduced contrast in enucleated observers

Previous research has shown that observers with early unilateral enucleation have selectively better sensitivity to luminance contrast than monocular viewing controls [González et al., 2002; Vision Research 36 (1) (1996) 175; Vision Research 36 (1996) 3011; Vision Research 37 (17) (1997) 2465]. We asked whether unilateral enucleation specifically enhances all levels of luminance processing. Enucleated observers, as well as binocular and monocular viewing controls, detected global shape in radial frequency (RF) patterns [Vision Research 38 (1998) 2555] at low contrast. Control observers were tested in two monocular conditions in which the stimulus was presented to one eye, while the fellow eye: (1) viewed a luminance-matched grey field or (2) was covered by a dark eye patch. Sensitivity to low-contrast global shape was equivalent in enucleated observers and binocular controls. More importantly, enucleated observers showed superior performance to that of controls in either monocular condition. At low contrast, the dichoptic control group was more sensitive than controls wearing an eye patch, which suggests that dichoptic viewing is a superior method of testing when comparing monocular control performance to that of monocularly deprived populations. The previously reported enhanced sensitivity to luminance-defined form in early enucleated observers also occurs for low-contrast global shape discrimination.     

Influence of pupil diameter on the relation between ocular higher-order aberration and contrast sensitivity after laser in situ keratomileusis

PURPOSE: To investigate the influence of pupil diameter on the relation between induced changes in ocular higher-order wavefront aberrations and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 215 eyes of 117 patients (age, 33.2 +/- 8.3 years) undergoing LASIK for myopia of -1.25 to -13.5 D (-5.28 +/- 2.55 D), ocular wavefront aberrations and contrast sensitivity function were determined before and 1 month after surgery. Preoperative photopic pupil diameter was measured with a digital camera. Ocular higher-order aberrations were measured for a 4-mm pupil with a Hartmann-Shack wavefront analyzer. The root-mean-square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberration, respectively. From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: One hundred five eyes had a photopic pupil diameter of 4 mm or larger, and the remaining 110 had a photopic pupil diameter smaller than 4 mm. There were no statistically significant differences in the background clinical data between these two groups. In the eyes with a photopic pupil diameter of 4 mm or larger, the changes in third-order comalike aberrations did not correlate with the changes in AULCSF (Pearson correlation coefficient, r = -0.037, P = 0.723) and 10% low-contrast visual acuity (r = 0.125, P = 0.224), but fourth-order spherical-like aberrations correlated significantly with the changes in AULCSF (r = -0.229, P = 0.024) and 10% low-contrast visual acuity (r = 0.221, P = 0.038). In the eyes with photopic pupil size smaller than 4 mm, there were significant correlations between the changes in comalike aberrations and the changes in AULCSF (r = -0.487, P < 0.001) and 10% low-contrast visual acuity (r = 0.310, P = 0.003), but spherical-like aberrations showed no correlation with the changes in AULCSF (r = -0.078, P = 0.485) and 10% low-contrast visual acuity (r = 0.208, P = 0.158). CONCLUSIONS: In eyes with larger photopic pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in coma-like aberration exert greater influence on visual performance.     

Between-eye asymmetry in keratoconus

PURPOSE: To report baseline differences between eyes on key variables in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study cohort compared with a retrospectively assembled group of myopic contact lens wearers without ocular disease. METHODS: A total of 1,079 keratoconus patients who had not undergone a penetrating keratoplasty in either eye before their baseline visit were enrolled and examined at baseline. Records from 330 contact lens-wearing myopes were reviewed. Corneal curvature (keratometry), visual acuity, refractive error (manifest refraction), and corneal scarring were measured. RESULTS: The mean differences between keratoconic eyes are as follows (better eye-worse eye for each variable, separately). Flat keratometry: -3.59 +/-4.46 D and steep keratometry: -4.35 +/-4.41 D; high-contrast best-corrected visual acuity: 7.30 +/-6.83 letters; low-contrast best-corrected visual acuity: 8.53 +/-7.51 letters; high-contrast entrance visual acuity: 9.03 +/-8.40 letters; low-contrast entrance visual acuity: 9.43 +/-7.88 letters; spherical equivalent refractive error: 3.15 +/-3.84 D; and refractive cylinder power 1.55 +/-1.42 D. Twenty-one percent of the keratoconus patients had corneal scarring in only one eye. There is an association between patient-reported unilateral eye rubbing and greater asymmetry in corneal curvature, and between a history of unilateral eye trauma and greater asymmetry in corneal curvature and refractive error, with the rubbed/traumatized eye being the steeper eye most of the time. CONCLUSIONS: Keratoconus is asymmetric in the CLEK Study sample.     

Training in contrast detection improves motion perception of sinewave gratings in amblyopia

PURPOSE. One critical concern about using perceptual learning to treat amblyopia is whether training with one particular stimulus and task generalizes to other stimuli and tasks. In the spatial domain, it has been found that the bandwidth of contrast sensitivity improvement is much broader in amblyopes than in normals. Because previous studies suggested the local motion deficits in amblyopia are explained by the spatial vision deficits, the hypothesis for this study was that training in the spatial domain could benefit motion perception of sinewave gratings. METHODS. Nine adult amblyopes (mean age, 22.1 ± 5.6 years) were trained in a contrast detection task in the amblyopic eye for 10 days. Visual acuity, spatial contrast sensitivity functions, and temporal modulation transfer functions (MTF) for sinewave motion detection and discrimination were measured for each eye before and after training. Eight adult amblyopes (mean age, 22.6 ± 6.7 years) served as control subjects. RESULTS. In the amblyopic eye, training improved (1) contrast sensitivity by 6.6 dB (or 113.8%) across spatial frequencies, with a bandwidth of 4.4 octaves; (2) sensitivity of motion detection and discrimination by 3.2 dB (or 44.5%) and 3.7 dB (or 53.1%) across temporal frequencies, with bandwidths of 3.9 and 3.1 octaves, respectively; (3) visual acuity by 3.2 dB (or 44.5%). The fellow eye also showed a small amount of improvement in contrast sensitivities and no significant change in motion perception. Control subjects who received no training demonstrated no obvious improvement in any measure. CONCLUSIONS. The results demonstrate substantial plasticity in the amblyopic visual system, and provide additional empirical support for perceptual learning as a potential treatment for amblyopia.     

Longitudinal changes in visual acuity in keratoconus

PURPOSE: The present investigation aimed to identify factors that predict reduced visual acuity in keratoconus from a prospective, longitudinal study. METHODS: This report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study used 7 years of follow-up data from 953 CLEK subjects who did not have penetrating keratoplasty in either eye at baseline and who provided enough data to compute the slope of the change over time in high- or low-contrast best-corrected visual acuity (BCVA). Outcome measures included these slopes and whether the number of letters correctly read decreased by 10 letters or more in at least one eye in 7 years. RESULTS: Mean age of the subjects at the first follow-up visit was 40.2 +/- 11.0 years (mean +/- SD). Overall, 44.4% were female, and 71.9% were white. The slope of the change in high- and low-contrast BCVA (-0.29 +/- 1.5 and -0.58 +/- 1.7 letters correct/year, respectively) translated into expected 7-year decreases of 2.03 high- and 4.06 low-contrast letters correct. High- and low-contrast visual acuity decreases of 10 or more letters correct occurred in 19.0% and 30.8% of subjects, respectively. Independent predictors of reduced high- and low-contrast BCVA included better baseline acuity, steeper first definite apical clearance lens (FDACL), and fundus abnormalities. Each diopter of steeper baseline FDACL predicted an increased deterioration of 0.49 high- and 0.63 low-contrast letters correct. CONCLUSIONS: CLEK Study subjects with keratoconus exhibited a slow but clear decrease in BCVA during follow-up, with low-contrast acuity deteriorating more rapidly than high-contrast. Better baseline BCVA, steeper FDACL, and fundus abnormalities were predictive of greater acuity loss with time.     

Repeatability and intercorrelations of standard vision tests as a function of age.

PURPOSE: We assessed repeatability and intercorrelations of five standard vision tests in subjects with normal vision. METHODS: Seventy-eight subjects (aged 21 to 68 years) completed five measurements each of high- and low-contrast visual acuity, near visual acuity and contrast sensitivity (Pelli-Robson chart). RESULTS: Except for correlations between high- and low-contrast visual acuity (r = 0.78), intercorrelations between tests were low to moderate (r < 0.5). For each measure, variability for the group was about one line on the chart (one triplet for the Pelli-Robson chart) and the minimum variability for an individual subject was about one third of this. On average, 1 to 2 lines can be expected to be lost over the normal lifespan on each test. Variability in responses did not increase significantly with age for any test. CONCLUSIONS: The criterion for judging change on commonly used clinical vision tests is about one line for subjects over a wide age range.     

Associations between subjective and objective visual function in patients with unilateral macular holes

Forty-six patients with uniocular macular holes and unaffected, fellow eyes were studied to evaluate inter- and intraocular associations between various objective tests of visual function and perceived visual ability. The affected eye had significant associations between visual acuity (VA) and the fovea threshold test, but for the fellow eye only VA and low-contrast VA 10% were associated. The reduction in visual acuity under low-contrast conditions relative to high-contrast did not differ between the affected eye and the healthy eye. Subjective visual ability seems to depend more on the visual acuity of the affected eye than the healthy eye.     

Impact of a modified optic design on visual function: clinical comparative study

PURPOSE: To determine whether implantation of an intraocular lens (IOL) with a modified anterior surface designed to compensate for the positive spherical aberration of the cornea in eyes of cataract patients results in improved pseudophakic quality of vision. SETTING: Department of Ophthalmology, Bundesknappschaft's Hospital, Sulzbach, Germany. METHODS: In an intraindividual randomized study of 45 patients with bilateral cataract, an IOL with a modified anterior surface (Tecnis Z9000, Pharmacia) was compared with a biconvex lens with spherical surfaces (SI-40, Allergan). All patients had bilateral cataract surgery; in 1 eye the Z9000 IOL was implanted and in the other, the SI-40 IOL. After 1 and 3 months, the following investigations were performed: assessment of the anterior and posterior segments including IOL decentration and tilt, pupil size, high- and low-contrast visual acuities, photopic and mesopic contrast sensitivities, and wavefront aberration of the cornea and eye. RESULTS: Thirty-seven patients were examined at all follow-up visits. Although the eyes with the Z9000 IOL had significantly better best corrected visual acuity after 3 months, the improved quality of vision was more apparent when assessing low-contrast visual acuity and contrast sensitivity. Wavefront measurements revealed no significant spherical aberration in eyes with a Z9000 IOL but significantly positive spherical aberration in eyes with an SI-40 IOL. CONCLUSIONS: The clinical results confirm the theoretical preclinical calculations that the spherical aberration of the eye after cataract surgery can be eliminated by modifying the anterior surface of the IOL. The Tecnis Z9000 lens compensates for the positive spherical aberration in older eyes. This leads to a significant improvement, particularly in contrast sensitivity and mesopic visual quality.     

Low-contrast letter charts in early diabetic retinopathy, ocular hypertension, glaucoma, and Parkinson''s disease.

Diabetes can cause visual loss that is not detected by standard reading tests such as the Snellen test but can be detected by low-contrast letter charts. This visual loss is quite different from loss caused by refractive error. These low-contrast charts are diagnostically at least as sensitive as the sinewave grating contrast sensitivity test. They are inexpensive, and the test is brief and simple. Preliminary evidence is that patients with diabetes who have abnormal low-contrast chart results give abnormal intravenous fluorescein (IVF) test results, even though visual acuity is normal. Low-contrast charts also detect visual loss in patients with ocular hypertension, glaucoma, and Parkinson's disease, including patients with normal visual acuity.