Steady-state pattern electroretinogram following long term unilateral administration of timolol to ocular hypertensive subjects

Abstract

To determine whether long-term reduction of intraocular pressure leads to a corresponding preservation of the pattern electroretinogram (PERG), PERGs were studied in 21 patients with ocular hypertension who had received unilateral timolol therapy for a minimum of 6 years. The mean difference in intraocular pressure (IOP) between the placebo-treated and the timolol-treated eyes (over 6 years) was 2.4 mm Hg. Steady-state PERGs (16.0 rps) were obtained simultaneously in both eyes of each patient, with four check sizes (0.25, 0.5, 1.0 and 2.0 degrees). Significant (p less than 0.05) steady-state PERG deficits (i.e., amplitude more than two standard deviations below the mean value of age-matched controls) were observed in 16 eyes of 12 patients (10 placebo-treated and 6 timolol-treated eyes). The mean PERG amplitude did not differ significantly between the placebo-treated and timolol-treated eyes. However, a significant correlation (r = -0.423) in the IOP differences between the placebo-treated and timolol-treated eyes and the corresponding PERG amplitude differences was noted in three of the four test conditions (i.e. 0.25, 0.5, and 1.0 degrees). These results suggest that reducing IOP may preserve ganglion cell function in some patients with ocular hypertension.

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

“…Tak en together, these findings indicate that the degree and prevalence of pattern electroreti nogram abnormalities in treated ocular hyper tension are associated with the individual in traocular pressure control in the 15-25 mm Hg range. The present results confirm pre vious data on treated ocular hypertensives [14,15], and show, in addition, that timololtreated eyes with moderate hypertension ex hibit pattern electroretinogram losses that are comparable to those of untreated eyes retain ing similar intraocular pressures. The differ ences in pattern electroretinogram ampli tudes across ocular hypertensives found in the present study may presumably reflect differ ent degrees of ganglion cell dysfunction asso ciated with long-term intraocular pressure control.…”

“…The results of two recent prospective studies have indicated that in traocular pressure normalization can prevent or delay the onset of visual field damage in treated as compared to untreated ocular hy pertensive eyes [10], or prevents the progres sion of visual field defects in eyes with early glaucoma [11], The relationship between pat tern electroretinogram changes and intraocu lar pressure control in treated ocular hyper tension is currently a matter of investigation. In a cross-sectional study on patients with moderate ocular hypertension who had re ceived unilateral long-term treatment with ti molol (and a placebo in the fellow eye), Nesher et al [14] reported no significant differ ences in the electroretinographic amplitudes between the timolol-treated and placebotreated eyes, or between hypertensive eyes (either timolol or placebo treated) and normal controls. However, the authors showed in a correlational analysis that amplitudes tended to be lower in eyes with higher intraocular pressures.…”

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.…”

The role of pattern-reversal electroretinography in the diagnosis of glaucoma

“…Based on the observed correlation between high IOP and reduced PERG response, likely as a result of RGC dysfunction, Feghali et al demonstrated that, in rabbits with low PERG amplitude associated with high IOP, the amplitude was immediately normalized when the IOP was lowered (57) . Other studies have evaluated the effect of medically or surgically reduced IOP on PERG response in humans (58)(59)(60) . After following OHT patients treated with timolol as well as a control group receiving placebo for six years, Nesher et al observed a significant correlation between IOP levels and steady-state PERG amplitude (58) .…”

“…Other studies have evaluated the effect of medically or surgically reduced IOP on PERG response in humans (58)(59)(60) . After following OHT patients treated with timolol as well as a control group receiving placebo for six years, Nesher et al observed a significant correlation between IOP levels and steady-state PERG amplitude (58) . Spadea et al observed no recovery of the PERG amplitude trabaculectomy was performed on eyes with advanced glaucoma (59) ; however, other authors reported that the PERG response could be restored after pharmacologically induced IOP reduction in low-and high-tension glaucomatous eyes, even in the presence of early VF de fects (60) , suggesting that PERG reduction is related not only to RGC loss, but also to RGC dysfunction.…”