Influence of glaucoma surgery on visual function: a clinical cohort study and meta-analysis.

PURPOSE: To determine the cost (loss of visual function associated with the procedure) and benefit (long-term preservation of the visual field) of glaucoma surgery. METHODS: We included 100 patients who underwent glaucoma surgery (Baerveldt glaucoma implant [BGI], n = 61; trabeculectomy [TE], n = 39). Preoperatively, the median (interquartile range [IQR]) standard automated perimetry mean deviation (MD) was -12 (-16 to -6) dB. We analysed the change in visual acuity (BCVA) and MD due to the procedure and, in a subset with at least 5 years of perimetric follow-up both pre- and postoperatively (n = 20), the change in rate of progression (ROP; time rate of change in MD). For the surgery-induced change in ROP, we also performed a meta-analysis including the current and previously published studies. From the surgery-induced decrease in MD and change in ROP, we calculated the average postoperative duration needed for the benefit to surpass the cost. RESULTS: Mean (standard deviation) MD decline was 1.3 (2.7) and 1.0 (2.3) dB for BGI (p < 0.001) and TE (p = 0.009), respectively; no significant surgery-induced changes in BCVA were found (p = 0.08 and p = 0.12, respectively). In our study, surgery was associated with a non-significant deceleration of ROP (from -0.37 [0.52] to -0.15 [0.48] dB/year; p = 0.23). The meta-analysis, based on eight studies, showed an overall surgery-induced change in ROP of 0.44 (95% confidence interval 0.25 to 0.64; p < 0.0001) dB/year. CONCLUSION: Glaucoma surgery significantly reduces the progression velocity in glaucoma. On average, the benefit of glaucoma surgery surpasses the cost after approximately 1.5 years.

Lateral Inhibition in the Human Visual System in Patients with Glaucoma and Healthy Subjects: A Case-Control Study.

In glaucoma, the density of retinal ganglion cells is reduced. It is largely unknown how this influences retinal information processing. An increase in spatial summation and a decrease in contrast gain control and contrast adaptation have been reported. A decrease in lateral inhibition might also arise. This could result in a larger than expected response to some stimuli, which could mask ganglion cell loss on functional testing (structure-function discrepancy). The aim of this study was to compare lateral inhibition between glaucoma patients and healthy subjects; we used a case-control design. Cases (n = 18) were selected to have advanced visual field loss in combination with a normal visual acuity. Controls (n = 50) were not allowed to have symptoms or signs of any eye disease. Lateral inhibition was measured psychophysically on a computer screen, with (1) a modified illusory movement experiment and (2) a contrast sensitivity (CS) test. Illusory movement was quantified by nulling it with a real movement; measure of lateral inhibition was the amount of illusory movement. CS was measured at 1 and 4 cycles per degree (cpd); measure of lateral inhibition was the difference between log CS at 4 and 1 cpd. Both measures were compared between cases and controls; analyses were adjusted for age and gender. There was no difference between cases and controls for these two measures of lateral inhibition (p = 0.58 for illusory movement; p = 0.20 for CS). The movement threshold was higher in cases than in controls (p = 0.008) and log CS was lower, at both 1 (-0.20; p = 0.008) and 4 (-0.28; p = 0.001) cpd. Our results indicate that spatially antagonistic mechanisms are not specifically affected in glaucoma, at least not in the intact center of a severely damaged visual field. This suggests that the structure-function discrepancy in glaucoma is not related to a decrease in lateral inhibition.

Influence of multifocal intraocular lenses on standard automated perimetry test results.

IMPORTANCE: A multifocal intraocular lens (MFIOL) allows for spectacle independence after cataract surgery and is thus a seemingly attractive option. However, several optical limitations have been reported or can be hypothesized. OBJECTIVE: To evaluate the influence of an MFIOL on standard automated perimetry (SAP) size III and size V test results. DESIGN: Cross-sectional case-control. SETTING: The University Medical Center Groningen and the Nij Smellinghe Hospital Drachten, the Netherlands. PARTICIPANTS: Sixteen eyes of 16 patients with a diffractive MFIOL (median age, 64 years), 18 phakic eyes of 18 healthy individuals serving as controls (median age, 62 years), and 12 eyes of 12 patients with a monofocal IOL (median age, 64 years) were included. INTERVENTIONS: All participants underwent (1) SAP using a 30-2 grid and the Swedish Interactive Threshold Algorithm standard strategy with stimulus size III and (2) a full threshold test with stimulus size V. MAIN OUTCOME MEASURES: Primary outcome measures were the mean deviation (MD) for size III and the mean sensitivity (MS) for size V. Comparisons between groups were adjusted for age and pupil size. RESULTS For SAP size III, the average difference in MD between patients in the MFIOL group and phakic controls was -2.40 dB (P < .001) and between patients in the monofocal IOL group and phakic controls was -0.32 dB (P = .52). For SAP size V, the corresponding differences in MS were -1.61 dB (P = .002) and -0.80 dB (P = .09), respectively. The differences were essentially independent of eccentricity for both SAP size III and SAP size V. CONCLUSIONS AND RELEVANCE: Patients with a diffractive MFIOL have a clinically relevant reduction of the visual sensitivity as assessed with SAP size III and size V. The reduction seems to be related to the multifocal design of the IOL rather than to pseudophakia. The reduction interferes with the assessment of common eye diseases such as glaucoma and comes on top of the decline of visual sensitivity due to normal aging or age-related eye diseases, thus potentially accelerating visual impairment.

Factors that influence standard automated perimetry test results in glaucoma: test reliability, technician experience, time of day, and season.

PURPOSE: To determine the influence of several factors on standard automated perimetry test results in glaucoma. METHODS: Longitudinal Humphrey field analyzer 30-2 Swedish interactive threshold algorithm data from 160 eyes of 160 glaucoma patients were used. The influence of technician experience, time of day, and season on the mean deviation (MD) was determined by performing linear regression analysis of MD against time on a series of visual fields and subsequently performing a multiple linear regression analysis with the MD residuals as dependent variable and the factors mentioned above as independent variables. Analyses were performed with and without adjustment for the test reliability (fixation losses and false-positive and false-negative answers) and with and without stratification according to disease stage (baseline MD). RESULTS: Mean follow-up was 9.4 years, with on average 10.8 tests per patient. Technician experience, time of day, and season were associated with the MD. Approximately 0.2 dB lower MD values were found for inexperienced technicians (P < 0.001), tests performed after lunch (P < 0.001), and tests performed in the summer or autumn (P < 0.001). The effects of time of day and season appeared to depend on disease stage. Independent of these effects, the percentage of false-positive answers strongly influenced the MD with a 1 dB increase in MD per 10% increase in false-positive answers. CONCLUSIONS: Technician experience, time of day, season, and the percentage of false-positive answers have a significant influence on the MD of standard automated perimetry.

Persistence, spatial distribution and implications for progression detection of blind parts of the visual field in glaucoma: a clinical cohort study.

BACKGROUND: Visual field testing is an essential part of glaucoma care. It is hampered by variability related to the disease itself, response errors and fatigue. In glaucoma, blind parts of the visual field contribute to the diagnosis but--once established--not to progression detection; they only increase testing time. The aims of this study were to describe the persistence and spatial distribution of blind test locations in standard automated perimetry in glaucoma and to explore how the omission of presumed blind test locations would affect progression detection. METHODOLOGY/PRINCIPAL FINDINGS: Data from 221 eyes of 221 patients from a cohort study with the Humphrey Field Analyzer with 30-2 grid were used. Patients were stratified according to baseline mean deviation (MD) in six strata of 5 dB width each. For one, two, three and four consecutive <0 dB sensitivities in the same test location in a series of baseline tests, the median probabilities to observe <0 dB again in the concerning test location in a follow-up test were 76, 86, 88 and 90%, respectively. For <10 dB, the probabilities were 88, 95, 97 and 98%, respectively. Median (interquartile range) percentages of test locations with three consecutive <0 dB sensitivities were 0(0-0), 0(0-2), 4(0-9), 17(8-27), 27(20-40) and 60(50-70)% for the six MD strata. Similar percentages were found for a subset of test locations within 10 degree eccentricity (P>0.1 for all strata). Omitting test locations with three consecutive <0 dB sensitivities at baseline did not affect the performance of the MD-based Nonparametric Progression Analysis progression detection algorithm. CONCLUSIONS/SIGNIFICANCE: Test locations that have been shown to be reproducibly blind tend to display a reasonable blindness persistence and do no longer contribute to progression detection. There is no clinically useful universal MD cut-off value beyond which testing can be limited to 10 degree eccentricity.

Myopia as a risk factor for open-angle glaucoma: a systematic review and meta-analysis.

OBJECTIVE: To determine the association between myopia and open-angle glaucoma. DESIGN: Systematic review and meta-analysis of observational studies. PARTICIPANTS: Thirteen studies involving 48 161 individuals. METHODS: Articles published between 1994 and 2010 were identified in PubMed, Embase, and reference lists. Study-specific odds ratios (ORs) were pooled using a random effects model. MAIN OUTCOME MEASURES: Odds ratios with 95% confidence intervals (CIs) of myopia as a risk factor for open-angle glaucoma. RESULTS: Data from 11 population-based cross-sectional studies were included in the main analyses. The pooled OR of the association between myopia and glaucoma based on 11 risk estimates was 1.92 (95% CI, 1.54-2.38). On the basis of 7 risk estimates, the pooled ORs of the associations between low myopia (myopia up to -3 D) and glaucoma and between high myopia (≤-3 D myopic) and glaucoma were 1.65 (1.26-2.17) and 2.46 (1.93-3.15), respectively. There was considerable heterogeneity among studies that reported an association between any myopia and glaucoma (I(2)=53%) and low myopia and glaucoma (I(2)=29%), but not for high myopia and glaucoma (I(2)=0%). After omitting studies that contributed significantly to the heterogeneity, the pooled ORs were 1.88 (1.60-2.20) for any myopia and glaucoma and 1.77 (1.41-2.23) for low myopia and glaucoma. CONCLUSIONS: Individuals with myopia have an increased risk of developing open-angle glaucoma. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.