Perimetric probability maps to separate change caused by glaucoma from that caused by cataract

Abstract

We describe a new method for analysis of change in glaucomatous visual fields with the object to differentiate between changes caused by glaucoma from those caused by cataract. New pattern deviation change probability maps were developed from a prospectively collected glaucoma material and designed to be sensitive to changes in localized field loss, but to be unaffected by media-induced perimetric change. We compared the new change probability maps with the commercially available total deviation change probability maps in series of Humphrey perimetric tests in a glaucoma material of 43 eyes of 35 patients, who had undergone cataract surgery. When using the total deviation maps, considerable differences were seen between fields obtained before and after cataract surgery. Much smaller differences were seen when using the new change probability maps, that almost eliminated the common and disturbing effect of increasing cataract. This new tool could be of considerable help in differentiation between progressive glaucomatous visual field loss and deterioration caused by increasing media opacities.

Fluctuation of Intraocular Pressure and Glaucoma Progression in the Early Manifest Glaucoma Trial

“…AGIS applied pointwise linear regression analyses of threshold sensitivities, which are more sensitive to increasing media opacities than the EMGT progression criterion. 18 Filtering surgery often leads to progressive cataract, which in turn, leads to a slow and monotonic worsening of threshold values. Therefore, it is reasonable to assume that the authors' visual field analysis resulted in more false positive progression in filtered than in non-filtered eyes, thus leading to an apparent link between IOP change and progression.…”

Effects of Argon Laser Trabeculoplasty in the Early Manifest Glaucoma Trial

“…Progression was defined as worsening of visual fields according to pre-defined criteria 6 based on computerized analyses using glaucoma change probability maps, 7 which have been shown to offer high sensitivity and specificity. 8,9 Glaucoma progression could also be identified as worsening of the disc, which was assessed by masked readings at a disc photography reading center.…”

Performance of glaucoma progression analysis software in a glaucoma population

“…Several studies have evaluated the performance of event analysis based on pattern deviation data compared to the use of total deviation data [5][6][7][8]. Pattern deviation analysis generally yields a smaller number of eyes with progression than total deviation analysis, as it does not account for diffuse loss from cataract progression [6,7] or for the diffuse glaucoma progression that differs from classical focal glaucomatous visual field deterioration [5]. In addition, in patients with moderate or advanced damage, pattern deviation calculations can also underestimate and bias the results [12,13].…”

“…By adjusting for diffuse changes in visual field sensitivity, pattern deviation analysis seeks to separate glaucomatous changes from those resulting from a cataract, on the assumption that a cataract causes a diffuse reduction in visual field sensitivity, whereas glaucoma leads to focal visual field changes [5]. A study in which the glaucomatous visual fields were tested for differences before and after cataract surgery showed that differences were much greater when using total rather than pattern deviation plots [6]. Therefore, pattern deviation analysis is thought to be less affected by cataract progression.…”