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Editors Selection IGR 24-3

Visual Function Tests: Long-term survival VF and visual acuity

Comment by Steve Mansberger on:

21714 Long-term survival of central visual field in end-stage glaucoma, Much JW; Liu C; Piltz-Seymour JR, Ophthalmology, 2008; 115: 1162-1166

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Much et al. (1022) evaluated the longterm survival of visual field and visual acuity in patients with severe glaucomatous visual field loss. The authors retrospectively identified subjects with severe glaucomatous visual field loss less than ten degrees by surveying a visual field database from their institution. They excluded patients for nonglaucomatous visual field loss, visual field worse than ‐19 db using a 24-2 pattern, and those that did not have four years follow-up. The authors enrolled approximately 262 eyes of 199 patients, but included only 84 eyes of 64 patients, based on the criteria noted above. The authors did not include a participant flow chart to decipher the proportion of patients excluded for various reasons.

The authors describe worsening glaucoma in three ways: 1) decrease in Snellen visual acuity of > 3 lines; 2) decrease in visual field mean deviation of > 3dB; or 3) decreased visual acuity or mean deviation. The authors include two other endpoints in Figure 1, but do not describe how these endpoints were determined within the Methods section. Overall, 14 eyes lost three lines of visual acuity; 7 eyes lost 3dB or more from the mean deviation; and 15 eyes worsened based on either visual acuity or mean deviation. This represents, at most, approximately 16% of persons worsening over a mean time period of 8.3 years.

The criteria for visual acuity loss did not include a manifest refraction, nor did the authors discuss how they mediated non-glaucomatous causes of visual acuity loss such as cataract. Similarly, the authors did not discuss how they determined (expert consensus or individual clinicians) that glaucoma was the etiology for losing 3dB in mean deviation on visual fields. Overall, if the authors inadvertently included non-glaucomatous causes for these outcomes this would decrease the already low proportion. Fifteen (15) eyes were lost to follow-up and the authors do not report how they analyzed these patients. Interestingly, the risk of visual field progression was reduced significantly in eyes that had undergone trabeculectomy; whereas visual acuity was not significantly different between eyes with or without a trabeculectomy. Overall, these results should be treated with caution since the study is retrospective. The authors conclude that the prognosis for treated patients with end-stage glaucoma may be better than was previously thought, since using either visual acuity or change in visual field only resulted in 16% of patients progressing over 8+ years. The study findings may be limited to African-Americans, since 80% of the subjects were African- American. Also, the authors only included 32% of the original enrolled population. Nevertheless, this provides needed information in a unique population.

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