Visual field progression patterns in the ocular hypertension treatment study correspond to vulnerability regions of the disc

Abstract

Objectives: To determine the locations on the 24-2 visual field (VF) testing grid that are most likely to progress in patients with ocular hypertension (OHTN). Based on a structural model of superior and inferior areas of relative vulnerability at the optic disc, we hypothesized that the nasal and paracentral regions are more prone to show a reduction in sensitivity.

Methods: Posthoc analysis of data collected in phases 1 and 2 of the Ocular Hypertension Treatment Study (OHTS). A pointwise analysis was applied to determine the progression patterns in the early and delayed treatment groups. Each group's progression rate and frequency were calculated for each of the 52 locations corresponding to the 24-2 VF strategy, using trend- and event-based analyses, respectively.

Results: For the event-based analysis, the events were most commonly found in the nasal and paracentral regions. The same regions, with some modest variation, were found to have the fastest rates of progression (ROP) measured with trend analysis. A similar pattern of progression was observed in both the early and delayed treatment groups. The difference in event rates and ROP between the early and delayed treatment groups was also greatest in the nasal and paracentral regions.

Conclusions: Development of VF loss in ocular hypertensive eyes appears to be consistent with the vulnerability zones previously described in glaucomatous eyes with established VF loss. Ocular hypotensive treatment likely helps to slow the rate of progression in these regions. This suggests that careful monitoring of these locations may be useful.

Fig. 1. The vulnerability zones model.

a The original schematic model (right eye vertically inverted for field view orientation) published by Hood et al. [7] showing the location of the superior vulnerability zone (SVZ, orange) and the inferior vulnerability zone (IVZ, green) on the temporal half of the disc. b Schematic model (right eye in field view orientation) highlighting the 24-2 visual field regions of vulnerability based on spatial correspondence to the IVZ and SVZ at the disc. The borders of the superior (red) and inferior (blue) regions supplying input to the temporal half of the disc are superimposed on retinal nerve fibre layer tracings modified from Fig. 3 by Jansonius et al. [8], with permission. The points on each hemifield on the 24-2 that are expected to have the greatest overlap (top quartile) with the corresponding disc vulnerability zone are marked by a yellow circle.

Fig. 2. Overview of the collected visual field data.

Number of fields (a) and follow-up duration (b) for the delayed and medication groups.

Fig. 3. Event based analysis.

The mean percentage of pointwise events in the delayed (A) and early (B) medication groups: The frequency of pointwise events varied across the 52 visual field points for the delayed (A) and early (B) medication groups. Locations with higher frequency of events are shown in darker background.

Fig. 4. Trend based analysis.

Distribution and mean threshold sensitivity rates for each point in the medication (A) and delayed medication groups (B): The distribution of progression slopes within each of the 52 field-points pointwise events varied across the 52 visual field points for the delayed (A) and early (B) medication groups. Locations with a higher frequency of events are shown in darker colours.

Fig. 5. Treatment effect.

Differences in rates of change (A) and frequency of pointwise events (B): The difference between the delayed and early medication groups in rates of change (A) and frequency of events (B) for each of the 52 points of the 24-2 visual field. Locations with higher frequency of event are shown in darker colours.