Abstract
Abstract: :
Purpose: A substantial proportion of retinal ganglion cells and nerve fibers die in glaucoma before visual field changes occur. These losses have been documented in the macular region in previous studies. We compared visual field findings and localized areas of retinal thinning, relative to normal values, in a series of patients with glaucoma. Methods: 37 eyes of 26 patients with glaucomatous visual field loss (at least two visual fields with Glaucoma Hemifield Test «outside normal limits» or Mean Deviation (MD) less than 5% or (Corrected) Pattern Standard Deviation (PSD) less than 5%, with corresponding glaucomatous optic disc findings confirmed by a glaucoma specialist) were studied. They underwent visual field testing (Humphrey II perimeter, 24-2 (SITA Fast)) and scanning with the Retinal Thickness Analyzer (RTA, Talia Technologies, Ltd, Neve Ilan, Israel). The RTA is a scanning laser technology to obtain digital optical cross-sections over the macular region. An automated algorithm computes a retinal thickness map and summary parameters, relative to a normative database, within regions of interest. RTA digital images were processed by new algorithms developed in Matlab software to provide a sharper definition of the retinal boundaries and thereby improve the automated analysis by the commercial software. The number of clusters with significant retinal thinning (ClusSignifThin) for the perifoveal region (6 x 6-mm2 area excluding the 600-µm-radius circle centered on the foveola) was computed using the RTA’s automated software (version 4.075). Results: All eyes with MD of -10 or worse had at least two ClusSignifThin. All eyes with MD of -4.8 or worse had at least one ClusSignifThin. 83% of eyes with MD between -2 and -4.5 had at least one ClusSignifThin. 80% of eyes with MD better than -2 had at least one ClusSignifThin. All eyes with PSD values ≥4 had at least one ClusSignifThin. 75% of eyes with PSD < 4 had at least one ClusSignifThin. Conclusion: In eyes with defined glaucomatous visual field loss, significant retinal thinning was observed in the macular region in a high percentage of eyes that still had PSD or MD within normal limits. This provides further evidence that structural changes in the macular region, objectively detected by the RTA, precede visual field changes. A longitudinal study is underway to assess the prognostic significance of macular RT changes.
Keywords: 354 clinical (human) or epidemiologic studies: prevalence/incidence • 430 imaging/image analysis: clinical • 624 visual fields