Prevalence and nature of early glaucomatous defects in the central 10° of the visual field

Abstract

Importance: The macula is essential for visual functioning and is known to be affected even in early glaucoma. However, little is currently understood about the prevalence and nature of central vision loss in early glaucoma.

Objective: To determine the prevalence and characteristics of visual field (VF) defects in the central 10° in glaucoma suspects and patients with mild glaucoma using a prospective design.

Design, setting, and participants: This prospective observational cohort study was conducted at an outpatient glaucoma specialty clinic. One hundred eyes from 74 patients with glaucomatous optic neuropathy and a 24-2 VF with mean deviation better than -6 dB were prospectively studied and tested with a 10-2 test.

Main outcomes and measures: Reliable: VF hemifields were classified as abnormal based on a cluster criterion, and abnormal 10-2 VFs were categorized based on the pattern of abnormal points: arcuatelike, widespread, or other. In addition, at each point of the 10-2 VF, the total deviation values were averaged across eyes and the number of abnormal points with total deviation values below a specific criterion level were calculated. RESULTS There appeared to be as many abnormal 10-2 hemifields (53%) as abnormal 24-2 hemifields (59%). Of the eyes with normal 24-2 hemifields, 16% were classified as abnormal when the 10-2 test was used. Of the abnormal 10-2 hemifields, 68%, 8%, and 25% were arcuatelike, widespread, and other, respectively. The average total deviation values and number of abnormal points plots revealed superior VF defects that were deeper and closer to fixation than those in the inferior VF.

Conclusions and relevance: The 10-2 VF was abnormal in nearly as many hemifields as was the 24-2 VF, including some with normal 24-2 VF, suggesting that the 24-2 test is not optimal for detecting early damage of the macula. The pattern of the defects was in agreement with a recent model of macular damage.

Figure 1. Examples of 10-2 VF Categories

All VFs are presented in right eye view. (A) VFs with loss consistent with an arcuate-like pattern ranging from arcuate (left) to nasal (right). (B) VF with widespread loss. (C) VFs with temporal loss classified as “other.”

Figure 2. 24-2 and 10-2 VF Examples

The region within the blue cross on the 24-2 VFs corresponds to the region in the central 10° tested by the 10-2 VF test points. All fields are presented in right eye view. (A) Both superior hemifields are abnormal. (B) The superior hemifield is normal on the 24-2, but abnormal on the 10-2 VF. (C) The superior hemifield is abnormal on the 24-2, but normal on the 10-2 VF.

Figure 3. Average TD Values for All Patients

Average TD values at each 10-2 location in dB units (left panel) and as pseudo-color (right panel). The blue rectangle corresponds to the maculo-papillary region, which is preserved in the superior hemifield. Both maps are in right eye view.

Figure 4. Average TD Values for Specific Criterion Level

The number of eyes with TD values below specific criterion levels. Pseudo-color legends are to the right of each map and all maps are in right eye view.

Figure 5. The Schematic Model

The schematic model describes RGCs projections from the macula to the disc.^, (A) The RNFL bundles (dashed black curves) associated with RGCs outside the macula (blue circle) project to the regions (red arcs) of the superior (S) and inferior (I) quadrants of the disc, which are associated with the most RNFL damage. The RGCs within the grey area with dark grey border project to the relatively less vulnerable temporal quadrant of the disc, while the RGCs within the white area with red borders project to the more vulnerable inferior quadrant of the disc. (B) The schematic model is superimposed upon a retinal view of the 12 map of average TD values from Fig 3. The 10-2 points have been adjusted for RGC displacement.^. (C) The schematic model is superimposed upon a retinal view of the map of the number of eyes with TD values less than or equal to −5 dB from Fig 4. Pseudo-color legends are to the right of each map.