Glaucoma: Pupillary Light Reflex Tests Have Limited Value

Joe Barber Jr, PhD

July 12, 2013

An abnormal pupillary light reflex (PLR) is commonly detected in patients with glaucoma, and these differences can be used to distinguish glaucomatous eyes from unaffected eyes, according to the findings of a meta-analysis and literature review. However, the clinical utility of the tests remains limited, according to some experts.

Dolly S. Chang, MD, PhD, from the Glaucoma Center of Excellence and the Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, and the Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, and colleagues, published their findings online June 26 in Ophthalmology.

"In our review, we summarized the evidence from 30 studies and found that PLRs were more likely to be impaired among glaucoma patients," Dr. Chang told Medscape Medical News by email. "Unlike visual field testing, the assessment of PLRs does not require patients' subjective response to light stimulation, and this might provide us an alternative approach in testing optic nerve function."

The researchers searched Medline and Embase for studies that evaluated PLRs in patients with glaucoma, excluding articles that did not have an English abstract, those evaluating fewer than 10 patients with glaucoma, and nonoriginal studies. In the 30 studies included in the systematic review, a relative afferent pupillary defect (RAPD) was found in between 9% and 82% of patients with glaucoma.

In the 11 studies included in the meta-analysis, the pooled estimate corresponded to a sensitivity of 0.63 (95% confidence interval [CI], 0.43 - 0.80) and a specificity of 0.93 (95% CI, 0.85 - 0.97). The positive and negative likelihood ratios were 8.9 (95% CI, 5.1 - 15.8) and 0.4 (95% CI, 0.2 - 0.6), respectively, resulting in a diagnostic odds ratio of 22.7 (95% CI, 14.0 - 36.9).

In a separate analysis that excluded studies that used the swinging flashlight test, the sensitivity and specificity for detecting glaucoma were 0.74 (95% CI, 0.59 - 0.85) and 0.85 (95% CI, 0.77 - 0.90), respectively.

"The damage to ganglion cells among glaucoma patients contributed to the impairment of the afferent PLR, but most tests were not able to distinguish this damage from other pathological conditions," Dr. Chang told Medscape Medical News. "More evidence would be needed to support whether we can develop a more specific PLR test that can help us distinguish glaucoma damage from other neurological or ophthalmological conditions."

Ted Maddess, PhD, from Australian National University in Canberra, also noted that better tests exist to assess the response of glaucomatous eyes to light. "A problem with studies of the pupil that use a single light source is that the pupillary system has a very strong gain control that changes the size of the pupil response depending on the recent history of stimulus presentations to the eye." Dr. Maddess told Medscape Medical News. "This means the pupil can give a strong response to small or infrequent stimuli, even when the eye is quite damaged. So I think the RAPD, as classically measured, has low utility in early-stage glaucoma."

Dr. Chang received funding from the National Institute on Aging. The other authors have disclosed no relevant financial relationships. Dr. Maddess holds patents and patent applications under license to Seeing Machines Ltd.

Ophthalmology. Published online June 26, 2013. Abstract

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