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R.A. Barros, F.N. Kanadani, M. Pro, M. Shimmyo, V. Malhotra, C. Tello, J. Liebmann, R. Ritch; Ocular Pulse Amplitude (OPA) in High Myopia, Glaucoma, and Normal Subjects . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1800.
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Increasing degrees of myopia are a risk factor for glaucoma. Ocular pulse amplitude (OPA), the difference between the minimum (diastolic) and maximum (systolic) values of the pulsatile intraocular pressure (IOP) has been reported to be increased in patients with high–tension glaucoma (HTG) and reduced in both normal–tension glaucoma (NTG) and high myopia. We assessed OPA in normal, highly myopic, HTG and NTG patients.
95 patients (45 men, 50 women; mean age 59.2 ± 15.3 (SD) years) were enrolled in this prospective trial: Group A [20 patients with HTG and high myopia (refractive error (RE) ≥–6.00D)]; Group B (7 patients with NTG and high myopia); Group C (16 patients with HTG and RE ≤1.00D); group D (9 patients with NTG and RE ≤1.00D); group E (17 patients with high myopia without glaucoma); and group F (26 control patients without glaucoma, RE ≤1.00D). IOP and OPA were measured simultaneously with the Pascal Dynamic Contour Tonometer (Swiss Microtechnology, AG, Switzerland) by the same examiner.
OPAs for each group are listed in the table. Myopic eyes had lower OPAs than emmetropic eyes of similar glaucoma status (all p<0.0002, t–Test). Among highly myopic eyes there was no difference in OPA regardless of glaucoma status (all p>0.27). Among emmetropic eyes, OPA was lower in NTG compared with HTG and normal eyes (both p<0.03).
High myopia is associated with lower, measured OPA compared to emmetropic eyes. This may be related to an alteration in ocular blood flow or differences in scleral thickness and/or rigidity and its response to the cardiac cycle in highly myopic eyes. NTG emmetropic eyes also had lower OPA compared to non–NTG emmetropic eyes.
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