Pattern Electroretinogram in Treated Ocular Hypertension: A Cross-Sectional Study after Timolol Maleate Therapy

Abstract

To investigate pattern electroretinogram changes in treated ocular hypertension, we evaluated pattern electroretinogram recordings of 48 hypertensive eyes following an 8-month timolol maleate therapy. During treatment, 27 of 48 eyes had normalized intraocular pressures (15–18 mm Hg), while 21 retained elevated values (21–25 mm Hg). Twenty-eight eyes with untreated hypertension (22–25 mm Hg) lasting at least 8 months, as well as 32 untreated, normotensive eyes served as controls. When compared to untreated normotensive controls, timolol-treated eyes with either elevated or normalized intraocular pressures showed reductions in the mean electroretinographic amplitudes. However, these amplitude reductions were substantially greater in treated eyes with elevated pressures as compared to those with normalized ones. Untreated hypertensive controls showed pattern electroretinogram reductions, with respect to normal values, that were comparable to those of treated hypertensive eyes, but larger than those of treated normotensive ones. These results indicate that, in treated ocular hypertension, pattern electroretinogram losses tend to be associated with moderately increased intraocular pressures in the range of 21–25 mm Hg. Electro retinographic abnormalities may be, at least in part, prevented only by lowering intraocular pressure into a normal range.

Retrograde Signaling in the Optic Nerve Is Necessary for Electrical Responsiveness of Retinal Ganglion Cells

“…Numerous reports of early PERG impairment in glaucoma, 56,57 optic nerve diseases, 58 and diabetes 59,60 at least in part may be due to altered axon transport. Also, recovery of PERG amplitude losses after either IOP lowering 15,17,18,61,62 or removal of pituitary tumors 63 may be related to restoration of axon transport. Thus, the PERG may represent a promising marker of early, reversible axonal dysfunction preceding RGC death in glaucoma and optic nerve diseases.…”

Head-up tilt lowers IOP and improves RGC dysfunction in glaucomatous DBA/2J mice

“…Corresponding studies in human patients with suspicion of glaucoma or glaucoma in the early stages indicate that the effects described here have a counterpart in the human model. In particular, loss of PERG signal exceeds loss of optic nerve structure, suggesting dysfunction of anatomically present neurons (Ventura and Porciatti, 2005); abnormal PERG signal may be improved with IOP lowering, suggesting reversibility of RGC dysfunction (Colotto et al, 1995; Falsini et al, 1992; Nesher et al, 1990; Ventura et al, 2006). Moderate IOP elevation by means of a suction cup impairs the PERG signal in patients with ocular hypertension (Colotto et al, 1996); head-down body tilt may impair the PERG signal in patients with suspicion of glaucoma or glaucoma in the early stages, suggesting susceptibility of RGC function to additional stress (Ventura et al, 2008).…”

Effect of epigallocatechin-gallate on inner retinal function in ocular hypertension and glaucoma: A short-term study by pattern electroretinogram

“…Sample size estimates of patients for this study were based on previous investigations from our group [7,9] where the within-subject variability [expressed as data standard deviation (SD)] of PERG parameters was determined in OHT and OAG patients. Assuming within-subject SDs in PERG amplitude and phase of 0.1 logμV and 0.11 π (6.7 ms) respectively, the sample sizes of patients assigned to both treatment and placebo supplementation provided a power of 90%, at an α=0.01, for detecting a test-retest difference (i.e.…”

“…There is also an indication [7,9,29] that PERG may document, at a pre-clinical stage, an improvement of RGC function following therapeutic IOP reduction. With a similar rationale, PERG can be considered as an early indicator of functional RGC changes following an intervention aimed at counteracting oxidative stress.…”