Imaging in glaucoma

Improved estimates of visual field progression using bayesian linear regression to integrate structural information in patients with ocular hypertension

PURPOSE

To assess whether neuroretinal rim area (RA) measurements of the optic disc could be used to improve the estimate of the rate of change in visual field (VF) mean sensitivity in patients with ocular hypertension (OHT) using a Bayesian linear regression (BLR), compared to a standard ordinary least squares linear regression (OLSLR) of mean sensitivity (MS) measurements alone.

METHODS

MS and RA measurements were analyzed from a longitudinal series of 179 patients with OHT visiting Moorfields Eye Hospital between 1992 and 2000. For each patient, linear regression of RA was computed after an appropriate transformation to "scale" RA with MS measurements, and the slope coefficient from this regression was used as a prior for BLR of MS. The BLR then was compared with the OLSLR approach by evaluating how accurately each regression technique predicted future MS measurements.

RESULTS

On average, BLR was significantly more accurate than OLSLR for series up to 8 measurements long (root-mean-square prediction error [RMSPE] was 0.14 decibels [dB] smaller with BLR than OLSLR; P < 0.001, Wilcoxon signed-rank test), with OLSLR of VF data alone being more accurate for longer series (RMSPE was 0.06 dB smaller with OLSLR than BLR).

CONCLUSIONS

BLR provides a significantly more accurate estimate of the rate of change in MS than the standard OLSLR approach, especially in short time series, suggesting that structural measurements can be used successfully in statistical models to assist clinicians monitoring VF progression in patients with OHT. Further studies are necessary to validate the method in glaucoma patients.

Clock-hour laminar displacement and age in primary open-angle glaucoma and normal tension glaucoma

BACKGROUND

To find out the relationship between laminar displacement and age between patients with primary open-angle glaucoma and normal tension glaucoma.

DESIGN

Retrospective study conducted at a tertiary university hospital.

PARTICIPANTS OR SAMPLES

Twenty-six eyes of 26 primary open-angle glaucoma patients and 52 eyes of 52 normal tension glaucoma patients.

METHODS

Patients were scanned with a Stratus optical coherence tomography apparatus to measure the retinal nerve fibre layer thickness and to visualize the cross-sectional laminar displacement of 12 clock-hour segments, 30 degrees each. Depth1 was defined as the longest distance between the retinal pigment epithelium and the anterior laminar cribrosa surface, which represents the amount of laminar displacement.

MAIN OUTCOME MEASURE

Partial correlation coefficients adjusted by mean deviation and intraocular pressure between (i) retinal nerve fibre layer thickness and age, and (ii) Depth1 and age.

RESULTS

In the primary open-angle glaucoma group, strong negative correlations (approximately -0.343 ≈ -0.738) were found between Depth1 and age. Eight of 12 clock-hour segments' correlations were significant after Bonferroni correction (α = 0.0021; 24 comparisons). However, no significant correlations were found between Depth1 and age in the normal tension glaucoma group. When the correlation coefficients were compared between the two groups, eight clock-hour segments showed significant differences after Bonferroni correction.

CONCLUSIONS

The significantly different correlation between laminar displacement and age between primary open-angle glaucoma and normal tension glaucoma patients may suggest a different role of the lamina cribrosa to the disease.

Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error

PURPOSE

Commercial optical coherence tomography (OCT) systems use global signal quality indices to quantify scan quality. Signal quality can vary throughout a scan, contributing to local retinal nerve fibre layer segmentation errors (SegE). The purpose of this study was to develop an automated method, using local scan quality, to predict SegE.

METHODS

Good-quality (global signal strength (SS) ≥ 6; manufacturer specification) peripapillary circular OCT scans (fast retinal nerve fibre layer scan protocol; Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA) were obtained from 6 healthy, 19 glaucoma-suspect and 43 glaucoma subjects. Scans were grouped based on SegE. Quality index (QI) values were computed for each A-scan using software of our own design. Logistic mixed-effects regression modelling was applied to evaluate SS, global mean and SD of QI, and the probability of SegE.

RESULTS

The difference between local mean QI in SegE regions and No-SegE regions was -5.06 (95% CI -6.38 to 3.734) (p<0.001). Using global mean QI, QI SD and their interaction term resulted in the model of best fit (Akaike information criterion=191.8) for predicting SegE. Global mean QI ≥ 20 or SS ≥ 8 shows little chance for SegE. Once mean QI<20 or SS<8, the probability of SegE increases as QI SD increases.

CONCLUSIONS

When combined with a signal quality parameter, the variation of signal quality between A-scans provides significant information about the quality of an OCT scan and can be used as a predictor of segmentation error.

Comparison of retinal nerve fibre layer thickness with visual evoked potential and visual field in patients with multiple sclerosis

BACKGROUND

To evaluate retinal nerve fibre layer thickness and to compare results with visual evoked potentials and visual field in patients with multiple sclerosis.

DESIGN

A prospective, case-control study, university hospital setting.

PARTICIPANTS

Seventy-three eyes of 37 multiple sclerosis patients and 74 eyes of 37 healthy subjects.

METHODS

All patients underwent a complete neurological and ophthalmological examination and peri-papillary retinal nerve fibre layer thickness was evaluated using scanning laser polarimetry (GDx). Furthermore, visual evoked potential and visual field testing were performed.

MAIN OUTCOME MEASURES

The χ(2) test, Student's t-test, Mann-Whitney U-test and Pearson's correlation coefficient analysis of the GDx, visual evoked potential and visual field testing parameters.

RESULTS

GDx measurements showed significantly more retinal nerve fibre layer damage in the patients than in the control groups. Comparison of the GDx parameters between patients with optic neuritis and non-optic neuritis demonstrated a statistically significant difference in symmetry (P = 0.046) and superior/nasal parameters (P = 0.009). A correlation was found between the number, superior and inferior ratio parameters, and P100 amplitude obtained with visual evoked potential in patients with non-optic neuritis. Additionally, there was a correlation between the number, inferior ratio and superior/nasal parameters, and the mean deviation of visual field in the non-optic neuritis group.

CONCLUSIONS

For retinal nerve fibre layer thickness measurements in multiple sclerosis patients, the GDx, along with other techniques, such as visual evoked potential, can be used as a diagnostic and follow-up criterion, particularly in patients without optic neuritis.

Comparison of optical coherence tomography and scanning laser polarimetry measurements in patients with multiple sclerosis

PURPOSE

To compare optical coherence tomography (OCT) and scanning laser polarimetry (GDx) measurements of the retinal nerve fiber layer (RNFL) in multiple sclerosis (MS) patients with and without optic neuritis (ON).

METHODS

OCT and GDx were performed on 68 MS patients. Qualifying eyes were divided into two groups: 51 eyes with an ON history > or =6 months before (ON eyes) and 65 eyes with no history of ON (non-ON eyes). Several GDx and OCT parameters and criteria were used to define an eye as abnormal, for example, GDx nerve fiber indicator (NFI) >20 or 30, OCT average RNFL thickness, and GDx temporal-superior-nasal-inferior-temporal average (TSNIT) below 5 or 1% of the normative database of the instruments. Agreement between OCT and GDx parameters was reported as percent of observed agreement, along with the AC1 statistic. Linear regression analyses were used to examine the relationship between OCT average RNFL thickness and GDx NFI and TSNIT.

RESULTS

All OCT and GDx measurements showed significantly more RNFL damage in ON than in non-ON eyes. Agreement between OCT and GDx parameters ranged from 69 to 90% (AC1 0.37 to 0.81) in ON eyes and 52 to 91% (AC1 = 0.21 to 0.90) in non-ON eyes. Best agreement was observed between OCT average RNFL thickness (p < 0.01) and NFI (>30) in ON eyes (90%, AC1 = 0.81) and between OCT average RNFL thickness (p < 0.01) and GDx TSNIT average (p < 0.01) in non-ON eyes (91%, AC1 = 0.90). In ON eyes, the OCT average RNFL thickness showed good linear correlation with NFI (R = 0.69, p < 0.0001) and TSNIT (R = 0.55, p < 0.0001).

CONCLUSIONS

OCT and GDx show good agreement and can be useful in detecting RNFL loss in MS/ON eyes.

Pulsar perimetry in the diagnosis of early glaucoma

PURPOSE

To assess the ability of Pulsar perimetry (Pulsar) in detecting early glaucomatous visual field (VF) damage in comparison with Frequency Doubling Technology (FDT), Scanning Laser Polarimetry (SLP, GDx VCC), and Heidelberg Retina Tomography (HRT).

DESIGN

Prospective observational cross-sectional case study.

METHODS

This multicenter study included: 87 ocular hypertensives (OHT); 67 glaucomatous optic neuropathy (GON) patients; 75 primary open-angle glaucoma (POAG) patients; and 90 normals. All patients underwent standard automated perimetry (SAP) HFA 30-2, Pulsar T30W, FDT N-30, HRT II, and GDx VCC. Area under Receiver Operating Characteristic Curves (AROCs) for discriminating between healthy and glaucomatous eyes and agreement among instruments were determined.

RESULTS

The best parameters for Pulsar, FDT, HRT, and GDx were, respectively: loss variance square root; no. of areas with P< 5%; Cup-Shape-Measure; and Nerve Fiber Indicator (NFI). In detecting POAG eyes, Pulsar (AROC, 0.90) appeared comparable with FDT (0.89) and significantly better than HRT (0.82) and GDx (0.79). For GON, Pulsar ability (0.74) was higher than GDx (0.69) and lower than FDT (0.80) and HRT (0.83). The agreement among instruments ranged from 0.12 to 0.56. Pulsar test duration was significantly shorter than SAP and FDT (P< .001).

CONCLUSIONS

Pulsar T30W test is a rapid and easy perimetric method, showing higher sensitivity than SAP in detecting early glaucomatous VF loss. Its diagnostic ability is good for detecting early perimetric POAG eyes and fair for GON eyes. Pulsar performance was comparable with FDT, HRT, and GDx, even if the agreement between instruments was poor to fair.

The effect of acute intraocular pressure elevation on peripapillary retinal thickness, retinal nerve fiber layer thickness, and retardance

PURPOSE

To determine whether acutely elevated intraocular pressure (IOP) alters peripapillary retinal thickness, retinal nerve fiber layer thickness (RNFLT), or retardance.

METHODS

Nine adult nonhuman primates were studied while under isoflurane anesthesia. Retinal and RNFLTs were measured by spectral domain optical coherence tomography 30 minutes after IOP was set to 10 mm Hg and 60 minutes after IOP was set to 45 mm Hg. RNFL retardance was measured by scanning laser polarimetry in 10-minute intervals for 30 minutes while IOP was 10 mm Hg, then for 60 minutes while IOP was 45 mm Hg, then for another 30 minutes after IOP was returned to 10 mm Hg.

RESULTS

RNFLT measured 1120 microm from the ONH center decreased from 118.1 +/- 9.3 microm at an IOP of 10 mm Hg to 116.5 +/- 8.4 microm at 45 mm Hg, or by 1.4% +/- 1.8% (P < 0.0001). There was a significant interaction between IOP and eccentricity (P = 0.0006). Within 800 microm of the ONH center, the RNFL was 4.9% +/- 3.4% thinner 60 minutes after IOP elevation to 45 mm Hg (P < 0.001), but unchanged for larger eccentricities. The same pattern was observed for retinal thickness, with 1.1% +/- 0.8% thinning overall at 45 mm Hg (P < 0.0001), and a significant effect of eccentricity (P < 0.0001) whereby the retina was 4.8% +/- 1.2% thinner (P < 0.001) within 800 microm, but unchanged beyond that. Retardance increased by a maximum of 2.2% +/- 1.1% 60 minutes after IOP was increased to 45 mm Hg (P = 0.0031).

CONCLUSIONS

The effects of acute IOP elevation on retinal thickness, RNFL thickness and retardance were minor, limited to the immediate ONH surround and unlikely to have meaningful clinical impact.

A method to detect progression of glaucoma using the multifocal visual evoked potential technique

PURPOSE

To describe a method for monitoring progression of glaucoma using the multifocal visual evoked potential (mfVEP) technique.

METHODS

Eighty-seven patients diagnosed with open-angle glaucoma were divided into two groups. Group I, comprised 43 patients who had a repeat mfVEP test within 50 days (mean 0.9 +/- 0.5 months), and group II, 44 patients who had a repeat test after at least 6 months (mean 20.7 +/- 9.7 months). Monocular mfVEPs were obtained using a 60-sector pattern reversal dartboard display. Monocular and interocular analyses were performed. Data from the two visits were compared. The total number of abnormal test points with P < 5% within the visual field (total scores) and number of abnormal test points within a cluster (cluster size) were calculated. Data for group I provided a measure of test-retest variability independent of disease progression. Data for group II provided a possible measure of progression.

RESULTS

The difference in the total scores for group II between visit 1 and visit 2 for the interocular and monocular comparison was significant (P < 0.05) as was the difference in cluster size for the interocular comparison (P < 0.05). Group I did not show a significant change in either total score or cluster size.

CONCLUSION

The change in the total score and cluster size over time provides a possible method for assessing progression of glaucoma with the mfVEP technique.

The role of optical coherence tomography in multiple sclerosis: Expert panel consensus

Optic neuritis (ON), a common manifestation of multiple sclerosis (MS), often occurs as the initial manifestation of central nervous system demyelination or develops during the course of this disease. Since the retinal nerve fiber layer (RNFL) is composed only of unmyelinated axons, measuring RNFL thickness represents a viable method of monitoring axonal loss in these patients. Optical coherence tomography (OCT) is a noninvasive, noncontact, accurate, and reproducible technique that quantitates the thickness of the peripapillary RNFL, fovea, and macula. Because of its potential role in defining axonal loss in ON and in assessing longitudinal changes in the RNFL before and after MS treatment, a multidisciplinary expert panel was charged with the following tasks: assess the current capabilities of OCT; review the current data about OCT, ON, and MS; and determine whether OCT could be a primary or secondary outcome measure in future MS clinical trials. The panel concluded that: [1] OCT is valid and reproducible; [2] OCT has yielded some important limited data concerning cross-sectional studies with ON and MS; [3] more studies are required to correlate OCT results with other measures of MS disease activity; [4] after correlation with these other measures and upon agreement of standardized technical and statistical methods, OCT may evolve into a important primary or secondary outcome metric for MS clinical trials and patient care.

A framework for comparing structural and functional measures of glaucomatous damage

While it is often said that structural damage due to glaucoma precedes functional damage, it is not always clear what this statement means. This review has two purposes: first, to show that a simple linear relationship describes the data relating a particular functional test (standard automated perimetry (SAP)) to a particular structural test (optical coherence tomography (OCT)); and, second, to propose a general framework for relating structural and functional damage, and for evaluating if one precedes the other. The specific functional and structural tests employed are described in Section 2. To compare SAP sensitivity loss to loss of the retinal nerve fiber layer (RNFL) requires a map that relates local field regions to local regions of the optic disc as described in Section 3. When RNFL thickness in the superior and inferior arcuate sectors of the disc are plotted against SAP sensitivity loss (dB units) in the corresponding arcuate regions of the visual field, RNFL thickness becomes asymptotic for sensitivity losses greater than about 10dB. These data are well described by a simple linear model presented in Section 4. The model assumes that the RNFL thickness measured with OCT has two components. One component is the axons of the retinal ganglion cells and the other, the residual, is everything else (e.g. glial cells, blood vessels). The axon portion is assumed to decrease in a linear fashion with losses in SAP sensitivity (in linear units); the residual portion is assumed to remain constant. Based upon severe SAP losses in anterior ischemic optic neuropathy (AION), the residual RNFL thickness in the arcuate regions is, on average, about one-third of the premorbid (normal) thickness of that region. The model also predicts that, to a first approximation, SAP sensitivity in control subjects does not depend upon RNFL thickness. The data (Section 6) are, in general, consistent with this prediction showing a very weak correlation between RNFL thickness and SAP sensitivity. In Section 7, the model is used to estimate the proportion of patients showing statistical abnormalities (worse than the 5th percentile) on the OCT RNFL test before they show abnormalities on the 24-2 SAP field test. Ignoring measurement error, the patients with a relatively thick RNFL, when healthy, will be more likely to show significant SAP sensitivity loss before statistically significant OCT RNFL loss, while the reverse will be true for those who start with an average or a relatively thin RNFL when healthy. Thus, it is important to understand the implications of the wide variation in RNFL thickness among control subjects. Section 8 describes two of the factors contributing to this variation, variations in the position of blood vessels and variations in the mapping of field regions to disc sectors. Finally, in Sections 7 and 9, the findings are related to the general debate in the literature about the relationship between structural and functional glaucomatous damage and a framework is proposed for understanding what is meant by the question, 'Does structural damage precede functional damage in glaucoma?' An emphasis is placed upon the need to distinguish between "statistical" and "relational" meanings of this question.

Comparison of diagnostic accuracy of Heidelberg Retina Tomograph II and Heidelberg Retina Tomograph 3 to discriminate glaucomatous and nonglaucomatous eyes

PURPOSE

To compare the diagnostic accuracy of the Moorfields regression analysis (MRA), parameters, and glaucoma probability score (GPS) from Heidelberg Retinal Tomograph (HRT) 3 (Heidelberg Engineering, Heidelberg, Germany) with MRA and parameters from HRT II in discriminating glaucomatous and healthy eyes in subjects of African and European ancestry.

DESIGN

Case-control institutional setting.

METHODS

Seventy-eight glaucoma patients (44 of African ancestry, 34 of European ancestry) and 89 age-matched controls (46 of African ancestry, 33 European ancestry), defined by visual fields and self-reported race were included. Imaging was obtained with HRT II, and data were exported to a computer with the HRT 3 software using the same contour line. Area under the receiver operating characteristic (ROC) curves (AUCs), sensitivity, and specificity were evaluated for the entire group, the African ancestry group, and the European ancestry group separately. Mean disk area was compared between correctly and incorrectly diagnosed eyes by each technique.

RESULTS

Disk, cup, and rim areas from HRT 3 were lower than HRT II (P < .0001). AUC (sensitivity at 95% specificity) was 0.85 (54%) for vertical cup-to-disk ratio (VCDR) HRT 3, 0.84 (45%) for VCDR HRT II, and 0.81 (44%) for GPS at the temporal sector. MRA HRT 3 showed greater sensitivity but lower specificity than HRT II for the entire group, the African ancestry group, and the European ancestry group. GPS classification had the lowest specificity. Glaucomatous eyes incorrectly classified by GPS had smaller mean disk area (P = .0002); control eyes incorrectly classified had greater mean disk area (P = .015).

CONCLUSIONS

VCDR from HRT 3 showed higher sensitivity than HRT II and GPS for the entire group and for those of African ancestry and of European ancestry separately. Sensitivity of MRA improved in HRT 3 with some trade-off in specificity compared with MRA of HRT II. GPS yielded erroneous classification associated to optic disk size.

Effect of glaucomatous damage on repeatability of confocal scanning laser ophthalmoscope, scanning laser polarimetry, and optical coherence tomography

PURPOSE

To determine and compare the effect of the severity of glaucomatous damage on the repeatability of retinal nerve fiber layer (RNFL) thickness with GDx-VCC (variable corneal compensation) and StratusOCT (optical coherence tomography; both produced by Carl Zeiss Meditec, Inc., Dublin, CA), and optic nerve head (ONH) topography with HRT-II (retinal tomograph; Heidelberg Engineering GmbH, Heidelberg, Germany) and StratusOCT.

METHODS

With each of these techniques, two measurements were obtained from 41 eyes of 41 control subjects and 98 glaucomatous eyes (37 patients with early, 29 with moderate, and 32 with severe field loss). To evaluate test-retest variability at each stage, limits of agreement (Bland-Altman plots) and repeatability coefficients (RCs) were obtained from pairs of measurements. Comparisons of within-subject variances were used to compare repeatability of GDx-VCC versus StratusOCT for global RNFL and HRT-II versus StratusOCT for global ONH topography. Effects from age, visual acuity, and lens status were also included in the analysis as covariates.

RESULTS

Test-retest variability of RNFL using GDx-VCC and StratusOCT were consistent through all stages of disease severity. Repeatability results of GDx-VCC were better than those of StratusOCT, except in severe cases. Test-retest variability of ONH topography using HRT-II and StratusOCT increased with increasing disease severity for rim area, cup area, and cup-to-disc (C/D) area ratio. In contrast, vertical C/D ratio from HRT-II, and horizontal C/D ratio from StratusOCT showed stable test-retest variability through all stages. Regardless of disease severity, repeatability results of HRT-II were better than those of StratusOCT.

CONCLUSIONS

GDx-VCC and HRT-II showed better repeatability than StratusOCT. Although test-retest variability increased with disease severity for rim area, the variability for vertical C/D ratio (HRTII) and global RNFL (GDx-VCC) was stable across disease severity. These parameters, rather than rim area, may be more useful in detection of progression in patients with glaucoma who have more advanced field loss.

Correlations between retinal nerve fiber layer and visual field in eyes with nonarteritic anterior ischemic optic neuropathy

PURPOSE

To evaluate correlations between retinal nerve fiber layer (RNFL) thickness with visual field (VF) sensitivities in eyes with nonartertic anterior ischemic optic neuropathy (NAION).

DESIGN

Case-control study in an academic, institutional setting.

METHODS

One eye from 21 patients with NAION and 32 healthy participants were included in this prospective study. Humphrey visual field (HVF) sensitivities were obtained from standard achromatic HVF test (24-2 SITA). RNFL was measured with scanning laser polarimetry (SLP, GDx-VCC) and optical coherence tomography (OCT, StratusOCT). Correlations were evaluated between RNFL and sensitivities from global, hemifields, and regional locations of the VF pertinent to the RNFL distribution. A total of 15 NAION eyes had inferior altitudinal HVF defects, and their global and regional RNFL was compared with that of control eyes. The main outcome measure was correlation between HVF sensitivities and RNFL.

RESULTS

Correlations of global, hemifield, and sectorial HVF sensitivities with RNFL were greater when RNFL was measured with OCT than with SLP, except for nasal and inferonasal sectors. RNFL thickness was far lower in the hemiretinas corresponding to the relative unaffected hemifield in eyes with altitudinal VF defect compared with controls.

CONCLUSIONS

In patients with NAION, RNFL measured by OCT provided better correlation to HVF changes than SLP did. Both instruments showed decreased RNFL in NAION eyes with altitudinal VF defects compared with control eyes, demonstrating loss of RNFL even in sectors of the optic disk that corresponded to relatively unaffected hemifield, suggesting greater damage beyond the extent estimated by VF methods.

Discrimination between glaucomatous and nonglaucomatous eyes using quantitative imaging devices and subjective optic nerve head assessment

PURPOSE

To compare the diagnostic ability of the confocal scanning laser ophthalmoscope (HRT-II; Heidelberg Engineering, Heidelberg, Germany), scanning laser polarimeter (GDx-VCC; Carl Zeiss Meditec, Inc., Dublin, CA), and optical coherence tomographer (StratusOCT, Carl Zeiss Meditec, Inc.) with subjective assessment of optic nerve head (ONH) stereophotographs in discriminating glaucomatous from nonglaucomatous eyes.

METHODS

Data from 79 glaucomatous and 149 normal eyes of 228 subjects were included in the analysis. Three independent graders evaluated ONH stereophotographs. Receiver operating characteristic curves were constructed for each technique and sensitivity was estimated at 80% of specificity. Comparisons of areas under these curves (aROC) and agreement (kappa) were determined between stereophoto grading and best parameter from each technique.

RESULTS

Stereophotograph grading had the largest aROC and sensitivity (0.903, 77.22%) in comparison with the best parameter from each technique: HRT-II global cup-to-disc area ratio (0.861, 75.95%); GDx-VCC Nerve Fiber Indicator (NFI; 0.836, 68.35%); and StratusOCT retinal nerve fiber layer (RNFL) thickness (0.844, 69.62%), ONH vertical integrated rim area (VIRA; 0.854, 73.42%), and macular thickness (0.815, 67.09%). The kappa between photograph grading and imaging parameters was 0.71 for StratusOCT-VIRA, 0.57 for HRT-II cup-to-disc area ratio, 0.51 for GDX-VCC NFI, 0.33 for StratusOCT RNFL, and 0.28 for StratusOCT macular thickness.

CONCLUSIONS

Similar diagnostic ability was found for all imaging techniques, but none demonstrated superiority to subjective assessment of the ONH. Agreement between disease classification with subjective assessment of ONH and imaging techniques was greater for techniques that evaluate ONH topography than with techniques that evaluate RNFL parameters. A combination of subjective ONH evaluation with RNFL parameters provides additive information, may have clinical impact, and deserves to be considered in the design of future studies comparing objective techniques with subjective evaluation by general eye care providers.

Effect of posterior capsular opacification removal on automated perimetry

PURPOSE

Although posterior capsular opacification (PCO) is a common phenomenon in a considerable number of ophthalmologic patients, no prospective controlled trials assessing its influence on automated perimetry exist. This technique continues as a standard in the diagnosis of glaucoma and neuro-ophthalmological diseases. The aim of the present report is to investigate the effect of PCO on automated visual field examination.

METHODS

A total of 26 PCO affected eyes of 26 patients had Humphrey SITA standard (program 24-2) immediately before, and between 1 and 8 weeks after Neodymium : YAG capsulotomy. The effect of learning associated with repeated testing was controlled with automated perimetry before enrollment and visual fields of the fellow eye. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), and global perimetric pre- and post-laser indices were compared using the Student's t-test for paired samples. Correlation and linear regression analyses were also performed.

RESULTS

BCVA and mean deviation (MD) improved following capsulotomy. Pattern standard deviation (PSD), an indicator of localized defects in the field, also improved significantly when PCO was solved. Moreover, a strong association among BCVA, MD, and PSD was shown both prior to and after capsulotomy.

CONCLUSION

PCO is a heterogeneous mean opacity. This polymorphism may alter visual field results, and may even simulate the perimetric behaviour of other pathologies such as glaucoma. Consequently, the presence of PCO should be considered in the interpretation of any automated perimetry in pseudophakic patients. In addition, the values obtained before capsulotomy may partially predict the values obtained after capsulotomy.