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D. Chao, M. T. Leite, L. M. Zangwill, R. N. Weinreb, C. Bowd, P. A. Sample, J. M. Liebmann, C. A. Girkin, F. A. Medeiros; Effect of Intraocular Pressure Fluctuations on Longitudinal Changes in Optic Disc Topographic Measurements Obtained by Confocal Scanning Laser Ophthalmoscopy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2718.
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To evaluate the effect of fluctuations in intraocular pressure (IOP) on longitudinal changes in neuroretinal rim area and retinal nerve fiber layer (RNFL) thickness, as measured by the Heidelberg Retina Tomograph (HRT).
The study included 1610 eyes (313 healthy, 724 suspects and 573 glaucomatous) from 964 patients. Patients were recruited from the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS) and from the African Descent and Glaucoma Evaluation Study (ADAGES) and followed for an average of 34 (±25) months. All patients had at least two visits with HRT imaging for a total of 5535 visits. The average interval between consecutive visits was 14 (±9) months. IOP measurements were obtained on the same day as HRT images. For each pair of consecutive visits, we calculated changes in topographic parameters and IOP. The relationship between changes in topographic parameters and change in IOP was investigated using generalized estimating equations to adjust for multiple measurements per patient.
For each 1 mmHg decrease in IOP between consecutive visits, there was a corresponding increase of 0.003 mm2 or 0.25% in rim area (P<0.001). When we restricted the maximum interval between visits to 12 months, each 1 mmHg decrease in IOP corresponded to a 0.13% increase in rim area (P=0.014). Selecting only patients that had an increase in rim area measurements during consecutive visits, we obtained a 0.16% increase in rim area for 1 mmHg decrease in IOP (P=0.032). Changes in IOP did not significantly influence mean RNFL thickness (P=0.33).
Changes in IOP during follow-up were significantly related to changes in rim area as measured by the HRT. Considering average reported rates of 1%/year of progressive rim area loss in glaucoma, relatively small changes in IOP can significantly affect detection of glaucoma progression for this parameter with this instrument.
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