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Abstract:
Purpose: To evaluate the relationship between measurements of the ocular pulse amplitude (OPA) and intraocular pressure, retinal nerve fiber layer thickness, axial length and central corneal thickness in glaucoma patients compared to healthy subjects.
Methods: One eye of 20 glaucoma patients defined by glaucomatous optic neuropathy (GON) based on clinical exam and 10 healthy subjects with normal optic nerve head exam, normal visual fields on standard automated perimetry (SAP) and normal intraocular pressure (IOP <= 21 mm Hg) were included. All glaucoma patients had reliable visual fields in the study eye on SAP with fewer than 33% false positives, 33% false negatives and 33% fixation losses. Each patient underwent 3 OPA measurements using dynamic contour tonometry on one randomly selected eye. Pearson correlation was performed between OPA measurements and IOP, retinal nerve fiber layer thickness, global visual field indices (MD and PSD) and central corneal thickness.
Results: There was no significant difference in age, refraction or gender between glaucoma patients and healthy subjects. Ocular pulse amplitude in glaucoma patients was lower than in the healthy group (2.98 ± 0.58 vs. 2.49 ± 1.04). OPA was significantly correlated to IOP in glaucoma patients and healthy subjects (r = 0.56, p< 0.0001, r = 0.43, p = 0.02). In healthy subjects, OPA was significantly correlated to axial length (r = -0.61, p = 0.0007). No correlation was found in glaucoma patients, respectively (r = -0.18, p = 0.19). There was no significant correlation between OPA measurements and Nerve Fiber Index in both experimental groups. Pattern standard deviation showed a significant correlation with OPA (r = 0.37, p = 0.0001) in the glaucoma patients, whereas mean deviation was significantly correlated with OPA in the healthy subjects (r = -0.63, p = 0.0004). Central corneal thickness was not correlated to OPA in both groups.
Conclusions: The glaucoma patients had lower OPA than healthy subjects. An explanation might be that our patients were treated for glaucoma with a mean IOP of 18.4 ± 1.5 mm Hg. It would be interesting to know if OPA changes after a wash-out period of local treatment in one eye of glaucoma patients in order to investigate if therapy influences OPA measurements.
