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M. K. George, M. B. Shields, P. J. Branden, M. Wand; Effect of IOP Lowering on the Optic Nerve Head and Retinal Nerve Fiber Layer Thickness. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2720.
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© ARVO (1962-2015); The Authors (2016-present)
To study the effect of intraocular pressure lowering on peripapillary retinal nerve fiber layer thickness and the optic nerve head.
Prospective observational study. Informed consent was obtained prior to enrollment. Inclusion criteria were patients over the age of 18 years who needed intraocular pressure (IOP) lowering for advancing glaucoma. All patients were on maximum tolerated medical therapy. Exclusion criteria included previous IOP lowering surgery, signal strength below 5, presence of clinically significant hypotony at post op repeat scanning, more than 50% sector averages showing pre-op RNFL thickness less than 50 microns and presence of any retinal pathology not attributable to glaucoma. IOP on 3 occasions prior to surgery and Stratus 3 OCTs within 30 days prior to trabeculectomy were obtained. Optic nerve head analyses focused on the superior-inferior and nasal-temporal rim areas, disc area, cup area and the cup volume. Peripapillary retinal nerve fiber layer thickness analyses focused on the superior, nasal, inferior and temporal quadrants and the average nerve fiber layer thickness. All scans were repeated twice pre and 12-16 wks post op using the repeat function and the average of the two scans were used for final analysis. Paired samples T-tests and Pearson correlation were used for the analysis using SPSS 13.0.
Twenty four eyes of 24 patients were included in the study. 10 patients were excluded for lack of complete data and 14 patients were included in the final analysis. The mean age of patients was 74.9 years. 12 patients had primary open angle glaucoma and one had pseudoexfoliation glaucoma and one had low tension glaucoma. The mean pre-op IOP was 23.26 mmHg which fell to 9.4 mmHg post op (p=0.000). There was no change in the rim area in the superior-inferior scan or the nasal-temporal scan. There was no statistically significant increase in the disc or cup area. The mean average nerve fiber layer thickness before and after surgery was 56.68 and 59.09 respectively (p=0.092). The mean cup volume fell from 0.35 to 0.26 (p=0.06). There was a significant Pearson correlation between fall in IOP and fall in cup volume (correlation = 0.821; p=0.002)
IOP lowering did not show any significant improvement in the optic nerve rim volume, cup or disc areas and the peripapillary retinal nerve fiber layer thickness after significant intraocular pressure lowering. There is a tendency toward reduction in cup volume with IOP lowering and this fall is significantly proportional to the fall in IOP.
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