Use of Topographical Structure–Function Agreement For Glaucoma Screening

Abstract

Purpose : To evaluate a topographical approach for glaucoma screening using the FORUM® (Carl Zeiss Meditec, Dublin, CA, USA) Structure-Function (S-F) combined report in a real-world clinical setting.

Methods : We collected S-F reports from individuals seen at a tertiary glaucoma clinic between 11/15/23-10/15/23. The S-F report combines the 24-2 visual field (VF) pattern deviation points with the six retinal nerve fiber layer (RNFL) zones of the Garway-Heath sectors (Fig. 1).¹ Each zone is color-coded based on the deviation of the mean RNFL thickness from the age-corrected reference database: green indicates thickness within normal limits; yellow indicates deviations from normal with P < 5%; red indicates deviations with P < 1%. All cases were reviewed by a glaucoma specialist (AL) and classified using the Columbia University Method (CU-method) for glaucoma detection^2,3 as glaucomatous optic neuropathy (GON, N=76), OCT glaucoma suspect (GS, N=10), or not glaucoma (NG, N=102). For this study, we recorded the color and the number of abnormal (P<2%) VF points of each RNFL zone. Different combinations of abnormal VF and abnormal RNFL criteria were evaluated. The optimal criteria was defined based on the percentages of abnormal structure–abnormal function (aS-aF) agreement found in GON eyes and “no aS-aF” found in NG eyes.⁴

Results : A criterion of “At least one yellow RNFL zone that has three or more abnormal VF points” (table 1, green highlight) yielded high overall agreement (91%) with an excellent “no aS-aF” agreement for the NG eyes (99%) and good aS-aF agreement for the GON eyes (80%). Similar performance was obtained with two other criteria (table 1, orange highlight). 15 of the 76 GON eyes were below the threshold of the “best” criteria. Lack of structure-function agreement was due to structural damage preceding functional loss (11) and vice versa (1). In the remaining 3 cases the abnormal VF cluster fell outside the boundaries of the abnormal RNFL zone.

Conclusions : A S-F report may be useful for ruling out glaucoma and has the potential to assist in detection of the disease. Detection of early glaucoma might be limited due to lower S-F agreement in such cases.

Reffs:
¹ Garway-Heath et al. Ophthalmology, 2000
² Hood et al. PRER 2022
³ Liebmann et al. JoG 2022
⁴ Tsamis et al. TVST 2020

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. FORUM® Combined Structure Function Section (not available in the USA)

 

Table 1. Agreement of aS-aF criteria for eyes with GON and NG