Functional visual impairment at different depths revealed by depth dependent integrated visual field simulation in glaucomatous visual field archetypes

Abstract

Purpose : Clinical visual fields (VFs) are measured monocularly at a single depth yet people interact with objects binocularly at depths that are different to the fixation plane. We have developed a depth dependent integrated visual field (DD-IVF) simulation program that enables visualization of defects at multiple depths. This project aimed to evaluate DD-IVF defects associated with typical, monocularly measured, glaucomatous VF defect archetypes.

Methods : Our DD-IVF simulation maps monocular VFs to binocular ones as a function of depth using binocular geometry. The simulation incorporates three parameters: fixation, object and interpupillary distance to simulate IVFs at specified depths. At each location and depth plane in the visual field, sensitivities are linearly interpolated from corresponding locations in monocular VFs and returned as the higher value of the two. We evaluated DD-IVFs arising from combinations of 12 glaucoma VF archetypes present in either left or right eye (144 combinations in total). The 12 archetypes included typical variants of superior and inferior nasal steps, arcuate and altitudinal defects, temporal wedge, biarcuate and intact visual fields.¹

Results : The 144 DD-IVFs are provided as a Shiny app in the Open Perimetry Initiative visualFields package 1.0.². The number of impaired locations in the DD-IVFs varied according to the overlap of visual field loss between eyes. Except for the biarcuate case, bilateral superior nasal defects produce most impaired locations in the DD-IVFs, followed by bilateral inferior nasal then bilateral inferior temporal defects. The visual defect patterns for objects in front of the fixation plane (e.g., 25 cm) can vary considerably from those at typical fixation distances (e.g., 60 cm), Figure 1.

Conclusions : Our DD-IVF app can be used to reveal functional visual defects associated with glaucoma VF archetypes. The comparison of identified functional visual impairment across multiple depths is informative for future exploration of functional visual impairments in glaucoma. Individual patient’s functional visual defects can be readily visualized using our model at any depth.

1. Elze J. R. Soc. Interface. 2015; 12: 20141118.
2. Marín-Franch J. Vis. 2013; 13:1-12.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. DD-IVFs with bilateral superior nasal steps nasal defects at 25, 60 (fixation plane) and 100 cm (sensitivity values in dB).