Effect modification of refractive error on visual field pattern deviation in glaucoma

Abstract

Purpose : Since glaucoma tends to produce specific visual field defects, the pattern deviation (PD) plot, which shows relative light sensitivity at each VF location, is crucial for the functional diagnosis of glaucoma. We studied effect modification of refractive error on PD values as a function of glaucoma severity.

Methods : In this retrospective study, the most recent reliable automated VFs (fixation loss≤33%, false negative/positive rates≤20%, SITA Standard 24-2) were selected among all patients from five clinical glaucoma practices. PD values at each VF location were modeled by linear regression with spherical equivalent (SE), mean deviation (MD), and their interaction (SE×MD) as regressors. P values of the slopes were adjusted for multiple comparisons.

Results : 120,019 eyes of 70,495 patients were selected (medians/[5th;95th] percentiles of age: 66.7 [34.7;86.5] years; MD: -2.7 [-20.2;0.9] dB; SE: -0.4 [-5.75;3.00] D). Fig. 1A shows the isolated effect of SE (i.e. unexplained by MD) on PD. Among all VF locations, 34.6% (predominantly central/infero-temporal) and 36.5% (predominantly peripheral/nasal) showed higher respectively lower PD values with increasing myopia. Fig. 1B illustrates significant interaction effects (SE×MD) on 82.7% of VF locations. With increasing myopia and increasing glaucoma severity, central/nasal VF areas become more depressed and peripheral/temporal areas less depressed. Fig. 2 quantifies the effect of SE on PD separately for the group with at most mildly depressed VFs (MD within ±1dB) vs. severely depressed VFs (MD < -12dB). Significant SE slopes range from -0.11 to +0.04 in mildly depressed VFs and from -0.23 to +0.19 in severely depressed VFs. This means, for severe glaucoma, high myopes (SE: -6D) have up to 2.28 dB lower and up to 2.76 dB higher PDs values than high hyperopes (SE: +6D).

Conclusions : Ametropia in isolation (Fig. 1A) as well as the interaction between ametropia and glaucoma severity (1B) were found to have significant effects on PD values. The two major retinal nerve fiber bundles, known to be vulnerable to glaucomatous damage, are closer to the fovea with increasing myopia (1C). The interaction results (1B) are consistent with a relative increase of glaucomatous VF loss at the individual locations of these bundles compared to the rest of the visual field. In severe glaucoma, single PDs differ by more than 2 dB between high myopes and hyperopes.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

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