The PERG in diabetic glaucoma suspects with no evidence of retinopathy

Objective: To better understand the role of diabetes mellitus on retinal ganglion cell function of glaucoma suspects. Methods: Eighteen diabetic glaucoma suspects (GSD) without retinopathy (type-2, n=16, type-1, n=2) and 156 age-matched glaucoma suspects (GS) without diabetes were tested with steady-state pattern electroretinogram (PERG, PERGLA paradigm, Ophthalmology 2004,111:161) as surrogate measure of retinal ganglion cell function. Results were compared with previously published data of 48 similarly aged normal controls (NC). All subjects (NC, GS, GSD) had small refractive errors and corrected visual acuity ≥20/25. Results: The mean PERG amplitude of both GS and GSD was significantly (P<0.01) smaller than that of age-matched NC. The mean PERG amplitude of GSD patients was significantly (P<0.05) smaller than that of GS accounting for individual differences in age, visual acuity, visual field defect, and intraocular pressure. The mean PERG phase did not differ between GS and GSD. Conclusions: In agreement with previous studies, our results show that on average, GS have reduced PERG amplitude compared with NC. PERG amplitude is further reduced in GSD compared with nondiabetic GS with otherwise comparable ophthalmologic and systemic conditions.