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R. A. Longmuir, K. Woodward, C. Doyle, C. Johnson, M. Wall; Improvement in Visual Field Performance in Patient With Glaucoma: The Variability in Perimetry Study. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2234.
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To determine if improvement in visual field performance is common among glaucoma patients in the Variability in Perimetry study.
All subjects were recruited from the glaucoma clinic at The University of Iowa Hospitals and Clinics. Enrollment criteria included the presence of optic disc changes with abnormal automated perimetry results. The patients could have primary, secondary, or normal tension glaucoma. Exclusion criteria included cataract with vision less than 20/30, pupils smaller than 2.5 mm, younger than age 19 years, or current pregnancy. Subjects underwent baseline visual field testing using the SITA-Size III, Size V full threshold, motion detection perimetry, and matrix perimetry. Included subjects performed these tests twice at baseline in one eye only, and the results averaged. Subsequent tests were performed every six months on the same eye, for a total of ten visits. Those subjects with eight or more tests are included. Mean deviation results from each test were used to create a regression line for the total number of tests performed, and the slope was used to determine if the subject’s visual field test had improved, worsened, or remained stable over time.
67 patients were included in the analysis. These patients all had prior experience taking visual field tests. Of these subjects, 20/67 (30%) showed measurable improvement of the mean deviation on the size III test and 20/67 (30%) improved on the size V test. 14/67 (21%) improved on both tests. Of these patients, five underwent surgery during the study period. Three underwent trabeculectomy with mitomycin C, one had cataract surgery, and one had both (trabeculectomy first, then cataract surgery). This patient worsened after trabeculectomy, and then improved after the cataract surgery.
Although improvement in visual field is often felt to be related to a "learning curve", the possibility of subtle visual field improvement related to control and/or treatment of glaucoma has never been fully addressed. Visual field improvement is common in the VIP study, showing that patients can show improvement in their visual field testing even while under care for glaucoma. Conventional wisdom holds that optic nerve function cannot improve, but this data may suggest otherwise. Other explanations for visual field improvement may include testing artifact, removal of media opacity in some (usually cataract) or improvement in acuity due to refraction.
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