Evaluation of visual function following neodymium:YAG laser posterior capsulotomy.

PURPOSE: Improvement in visual acuity is the primary endpoint for successful neodymium:YAG (Nd:YAG) laser posterior capsulotomy for posterior capsule opacification. There is limited information on related parameters of visual function that may also improve after laser treatment. The authors evaluate changes in contrast sensitivity and glare disability, aside from visual acuity, following Nd:YAG laser posterior capsulotomy. METHODS: Measurements of visual acuity, contrast sensitivity (using the Pelli-Robson chart), and glare disability (using the Brightness Acuity Tester [Mentor O & O, Inc., Norwell, MA]) were obtained from 24 consecutive patients before and after Nd:YAG laser posterior capsulotomy. Glare testing was done with both the Pelli-Robson and Early Treatment Diabetic Retinopathy Study (ETDRS) charts. The degree of glare disability was indicated by the difference between visual function with glare (at medium and high settings) and without glare. Prelaser measurements were taken within 2 weeks prior to treatment, and postlaser measurements were obtained within 3 months after treatment. Only one eye per patient was evaluated. RESULTS: Mean differences between prelaser and postlaser measurements were significantly different from zero: (1) Contrast sensitivity, mean difference = 0.24 log units (P < 0.0001); (2) High glare disability using Pelli-Robson chart, mean difference = 0.15 log units (P = 0.004); (3) Visual acuity using ETDRS chart, mean difference = 11 letters (P < 0.0001); 4) High glare disability using ETDRS chart, mean difference = 7 letters (P = 0.005). CONCLUSIONS: Using the above methods for visual function testing, Nd:YAG laser capsulotomy is shown to significantly improve visual acuity, contrast sensitivity, and glare disability measurements as compared with prelaser values. The ophthalmologist may find it helpful to document the last two measurements prior to Nd:YAG laser capsulotomy, especially in patients who have good visual acuity but complain of glare sensitivity.

Study of nuclear cataract progression using the National Eye Institute Scheimpflug system.

AIMS: A study was conducted to determine the capability of the recently developed National Eye Institute (NEI) Scheimpflug cataract imaging system in detecting changes in the nuclear region of the lens over a 1 year period. METHODS: Twenty five eyes with pure nuclear cataracts with mean nuclear densities < or = 0.30 optical density units (ODU) as well as 30 normal control eyes were each examined at baseline and 12 months later. Computerised densitometry using the NEI Scheimpflug cataract imaging system was performed. Clinical grading of the lenses was also done using the Lens Opacities Classification System II (LOCS II). For densitometry, a change of plus or minus 0.023 ODU (the 99% range) in mean density in the nuclear area was considered a progression or regression at 1 year. RESULTS: Using the Scheimpflug densitometry, 14 of the 25 cataractous eyes showed significant progression at 1 year. In the normal control group, only three of the 30 eyes showed significant progression. In contrast, using the LOCS II clinical grading, only two of the 25 cataractous eyes showed a one step increase, two of the 30 controls progressed at 1 year, and none regressed. There was no significant difference in visual acuity. CONCLUSION: This study suggests the value of the NEI Scheimpflug cataract imaging system in detecting nuclear change within 1 year. However, clinically significant changes may require longer follow up periods. These data will be useful in planning future longitudinal studies of nuclear cataracts, such as for clinical trials of anticataract drugs.

Scheimpflug photography and postcataract surgery posterior capsule opacification.

We describe a method to objectively document postcataract surgery posterior capsule opacification using Zeiss Scheimpflug photography and computerized image analysis. We examined 42 eyes with clear capsules (group A) and 27 with posterior capsule opacities (group B). The group A eyes had significantly better visual acuity (P < .05), lower mean capsular densitometry readings (0.03 +/- 0.03 optical density units versus 0.15 +/- 0.11 optical density units; P < .0001), and thinner capsules (0.03 +/- 0.4 mm versus 0.10 +/- 0.05 mm) than the group B eyes. This new objective method of documenting postoperative capsular haze may be useful for clinical studies such as clinical trials of drugs or surgical techniques being developed to prevent or minimize capsule opacification.

Progression of lens opacities in cataract patients after one year.

We used the Lens Opacities Classification System II to clinically grade the lenses of 57 patients with age-related cataracts in at least one eye. Progression or regression in each lens region was defined as a one or more step change in the Lens Opacities Classification System II grading noted at 1 year and maintained at the 1 1/2 to 2 year visit (the validation visit). A validated change in a lens region in one eye of a patient was considered a change in that region for that patient. Person-specific rates of cataract progression at 1 year were 42% for nuclear, 32% for cortical and 10% for posterior subcapsular opacities. Corresponding regression rates were 5%, 4%, and 2% for nuclear, cortical and posterior subcapsular opacities, respectively. Progression rates were significantly greater than the regression rates only for nuclear and cortical opacities (p < 0.0005). These findings show the applicability of the clinical Lens Opacities Classification System II method in documenting and monitoring lens changes over time. The usefulness of person-specific analysis was also shown.

Measurement error in assessing the size of cortical cataracts from retroillumination photographs.

This study describes a new method of quantifying anteriorly located cortical cataracts using retroillumination photographs and computer planimetry. Cortical cataracts were graded clinically and then photographed using the Neitz retroillumination camera twice by each of 2 photographers. The cataract outlines were traced onto a transparent overlay, and computer planimetry was performed using a Scan Maker 600ZS, a MAC II Computer and specially developed software. We estimated the measurement error of the method and its associated effect on sample size estimates for clinical studies. We calculated that the variability in this technique would contribute about 21 additional subjects to overall sample size estimates in studies comparing the mean areas of cortical opacities. In many studies this would be a small addition to total sample size requirements. This technique provides clinically useful measurements of the size of a cortical opacity as seen on a retroillumination photograph. This may be useful for future clinical studies on natural progression of cortical cataracts as well as for clinical trials of anticataract drugs.

Comparison of linear, multilinear and mask microdensitometric analyses of Scheimpflug images of the lens nucleus.

We wanted to determine the agreement among three methods currently used to measure the average density of the nucleus from a Scheimpflug video image of the lens, namely, the multilinear, linear and mask techniques. Using the NEI Scheimpflug Cataract Imaging System, video images of the lens were obtained from 49 eyes of 31 consecutive patients with predominantly nuclear opacities of varying severities. For each image, 3 separate determinations of the average nuclear density [in optical density units (odu)] were obtained by one analyst sequentially applying each of the three methods. Repeat measurements were obtained by the same analyst one week apart to evaluate reproducibility (using 95% error range), of each of the methods. Pairwise comparisons of the 3 methods were also done. Only the error due to outlining of the nucleus was assessed. Reproducibility of each method was excellent. The 95% error ranges were +/- 0.015 odu for the linear, +/- 0.013 odu for the multilinear, and +/- 0.017 odu for the mask methods. Very strong linear relationships were observed between the linear and multilinear methods (R2 = 0.99), between the linear and mask methods (R2 = 0.97), and between the multilinear and mask methods (R2 = 0.98). Simple linear regressions calibrating these three methods against each other would facilitate comparison of density measurements using any of these methods for analysis of Scheimpflug images of the lens nucleus.

Reproducibility of the NEI Scheimpflug Cataract Imaging System.

PURPOSE: The NEI Scheimpflug Cataract Imaging System was developed to allow for easy, accurate and reproducible image analysis of nuclear cataracts. This study was undertaken to determine the reproducibility of densitometric measurements of the lens nucleus using this modified system. METHODS: Replicate Zeiss Scheimpflug images of the lenses in 143 eyes were obtained by one photographer. Normal and cataractous lenses (without central cortical or anterior subcapsular opacities) were sampled. Images were stored after testing for adequacy using immediate exposure checking. Densitometry of the nuclear region was then performed for each image. The interval within which 99% of the differences between repeat measurements may be expected to lie was used as a measure of reproducibility (99% range). RESULTS: A 99% range of +/- 0.023 optical density units (odu) was obtained for nuclear densities < 0.30 odu (125 eyes). For lenses with nuclear densities > or = 0.30 odu (18 eyes), the 99% range was +/- 0.14 times the first measurement. CONCLUSION: This study shows the excellent reproducibility of this Scheimpflug imaging system in the nuclear region and demonstrates its usefulness in studies on nuclear cataracts, particularly for natural history studies and clinical trials of anti-cataract drugs.

Glare sensitivity in early cataracts.

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

Senile cataract progression studies using the Lens Opacities Classification System II.

PURPOSE: To determine cataract progression rates at 6-mo intervals as evaluated using the Lens Opacities Classification System II (LOCS II). METHODS: Idiopathic age-related cataracts in both eyes of 50 cataract patients and 17 normal control subjects were graded. The lenses were reexamined at 6 and 12 mo (+/- 2 mo) from baseline to determine rates of change. Progression or regression in patients or control subjects was considered to have occurred at the 6-mo examination if a one or more step change in the LOCS II grading was noted in at least one eye at 6 mo and maintained at the 12-mo visit. RESULTS: Six months from baseline, 38% of patients' conditions worsened in the nuclear area, 34% of patients' conditions worsened in the cortical region, and 8% of patients' conditions worsened in the posterior subcapsular region. Regression rates were 4% in each region. The percentages of patients progressing in the nuclear and cortical regions were significantly greater than the corresponding regression rates (P < .001). Greater progression was noted in the nuclear (P = .06) and posterior subcapsular (P < .01) regions in patients with early opacities (LOCS + 1/+2) as compared to patients with no opacities initially in the same lenticular areas. CONCLUSION: This study suggests that the LOCS II is capable of detecting changes in lens opacities in a relatively short period of time among persons with early to moderate opacities.

Contrast and glare sensitivity. Association with the type and severity of the cataract.

PURPOSE: Contrast and glare sensitivity tests are now being used as adjuncts to visual acuity in the assessment of visual function. Limited data are available on the associations of the former tests with cataract type and severity. The aim of the study is to assess these associations using standardized techniques. METHODS: Contrast sensitivity tests (using the Pelli-Robson chart) and glare sensitivity tests (using the Vistech MCT 8000) were done on 128 patients with cataracts and no other ocular disease and on 29 control volunteers. The cataracts were graded using the Lens Opacities Classification System II (LOCS II). Data from the left eyes were analyzed using logistic regression models. RESULTS: Contrast sensitivity loss was associated with cataract severity for cortical (P less than 0.0001) and posterior subcapsular (P = 0.0001) cataracts and with decreased visual acuity (P = 0.0001). Night and day glare sensitivity were each associated only with increased severity of posterior subcapsular cataracts (P less than or equal to 0.003) and with decreased visual acuity (P less than 0.001). Additional analyses showed that contrast and glare sensitivity were similar in eyes with no cataracts and early cataracts. CONCLUSION: These results suggest that the Pelli-Robson Chart and the Vistech MCT 8000 are good techniques for evaluating visual function in moderate to advanced cataracts. However, for early cataracts, other techniques need to be explored to assess visual function loss.