More Frequent Testing Detects Glaucoma Earlier

Emma Hitt, PhD

August 08, 2011

August 8, 2011 — Increased frequency of visual field testing, from once to twice yearly, appears to result in earlier detection of glaucoma progression, according to new research.

Kouros Nouri-Mahdavi, MD, with the Glaucoma Division, Jules Stein Eye Institute, University of California, Los Angeles, and colleagues reported the findings in the August 8, 2011, online issue of the Archives of Ophthalmology.

"Estimating rates of progression can help identify patients who are progressing at a faster pace and are therefore at serious risk of developing visual disability during their lifetime," Dr. Nouri-Mahdavi and colleagues write.

Based on simulation data, explain the study authors, a minimum of 3 examinations per year are required for achieving optimal sensitivity and specificity for detection of clinically significant rates of progression; "[h]owever, there is no evidence based on real patient data in the literature to support such recommendations," the study authors write.

In the current trend analysis, the researchers tested whether glaucoma progression would be detected earlier or in a larger proportion of patients with the more frequent testing schedule.

The analysis included visual fields of 468 eyes from 381 patients from the Advanced Glaucoma Intervention Study. All patients underwent at least 10 visual field tests during at least 3 years.

Beginning at year 1, every other visual field examination was excluded to generate a low-frequency data set, and the original group was kept as the high-frequency data set. The proportion of eyes that progressed and the time to progression were compared with global and pointwise linear regression criteria.

During follow-up, the median number of visual field examinations was 20 and 12 for the high- and low-frequency data sets, respectively. Progression as measured by global linear regression was noted in 43.6% of eyes in the high-frequency data set and 34.2% in the low-frequency data set (P < .001). With pointwise linear regression, the rate of progression was 39.5% of eyes in the high-frequency vs 35.7% in the low-frequency data set (P = .02).

The likelihood of detecting progression in the high-frequency data set compared with the low-frequency data set was more than 1.50 for both methods.

"[W]e found that a twice-yearly schedule of visual field testing resulted in earlier detection of glaucoma progression compared with a yearly schedule, especially with global trend analyses," the study authors conclude. "Our results have significant health care policy implications with regard to determining the frequency of visual field testing in patients with glaucoma," they add.

The study was funded by a grant from Research to Prevent Blindness. The study authors have disclosed no relevant financial relationships.

Arch Ophthalmol. Published online August 8, 2011. Abstract