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B. C. Chauhan, S. A. Lavender, C. A. Macgillivray, P. H. Artes, M. T. Nicolela; Optic Disc Changes in Ocular Hypertension. Results From a Longitudinal Prospective Study With Scanning Laser Tomography. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3330.
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To document the frequency and extent of optic disc changes in patients with ocular hypertension followed longitudinally with scanning laser tomography.
Our sample included 172 eyes of 87 patients with ocular hypertension. At baseline all patients had intraocular pressure > 21 mm Hg on three separate measurements, a normal standard automated perimetry and clinical optic disc examination. Patients were examined with the Heidelberg Retina Tomograph every 3 months for the first year and every 4 months thereafter. Optic disc changes were evaluated with the Topographic Change Analysis software and various criteria for depressed (red) and elevated (green) clusters for size (≥0.1, ≥0.5, ≥1, ≥2, ≥5 and ≥10% disc area) and depth (≥0, ≥20, ≥50, ≥100 and ≥200 microns) were applied. Data analysis was also performed on a reference sample of healthy controls (n = 70) followed longitudinally and the difference in event rates between ocular hypertensives and controls was calculated for each combination of depth and size criteria using Kaplan-Meier analysis and the log-rank test.
The mean age at baseline and number of examinations in the ocular hypertensive and control groups were similar (means: 51.0 and 53.1 yrs; 11 and 10 respectively). The best set of criteria to separate the two groups for depressions were for small clusters (>0.1% of disc area) with shallow changes (>0 and >20 microns) with log-rank chi-squared values ranging from 11.0 to 18.2. The best separation between the groups for elevations also tended to occur at the same criteria, however the separation was considerably poorer with respective chi-squared values ranging from 4.2 to 6.7. At visit 10, these criteria yielded between 15 and 22% differences in survival rates between the groups.
Compared to our previous work in glaucoma patients, this research shows that the best separation between ocular hypertensives and controls occurs at less conservative criteria. This suggests subtler changes in ocular hypertension where scanning laser tomography may have considerable utility before the development of visual field defects with standard automated perimetry.
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