The effect of optic neuritis treatment trial (ONTT) combined corticosteroid regimen on pattern reversal visual evoked potentials: a prospective follow-up study.

BACKGROUND: The combined corticosteroid regimen of the original Optic Neuritis Treatment Trial (ONTT) is used in many centers to treat optic neuritis. Though pattern reversal visual evoked potentials (PRVEPs) are a sensitive, standard measure of visual conduction in optic neuritis, no studies hitherto have investigated the effect of combined ONTT regimen on PRVEPs. We aimed to determine the effect of combined corticosteroid regimen of the ONTT on changes of PRVEPs in patients with first-episode optic neuritis over 3 months post-treatment. METHODS: This is a prospective, observational study in which 44 patients with optic neuritis were seen pre-treatment (baseline) and follow-up, at 1 month (FU1) and 3 months (FU2). Twenty-nine patients were treated with ONTT combined regimen (ONTT+ Group) while 15 were conservatively managed without corticosteroids (ONTT- Group). The median latency and amplitude values of the P100 PRVEP component and the visual acuity (i.e. LogMAR values) at pre-treatment, FU1 and FU2 were compared in the two groups using Friedman's rank test and Wilcoxon Signed Ranks test. RESULTS: Median P100 latency improved significantly (to the normal range) as early as by 1 month after the commencement of treatment in the ONTT+ Group, and then remained significantly lower than the baseline over next 2 months. In the ONTT- Group, the median P100 latency improved more slowly over the two follow up assessments and reached the normal range by 3 months. Median visual acuity values also improved significantly at 1 and 3 months after the commencement of treatment in the ONTT+ Group but not in the ONTT- Group. CONCLUSION: ONTT combined corticosteroid regimen improves conduction in the visual pathways of patients with first-episode optic neuritis earlier than does conservative management. We provide electrodiagnostic evidence that combined ONTT regimen-compared with conservative management-results in early remission of visual conduction abnormalities in first-episode optic neuritis.

Dysfunction in macula, retinal pigment epithelium and post retinal pathway in acute organophosphorus poisoning.

CONTEXT: Organophosphorus (OP) insecticide poisoning is a significant health problem in South Asian countries. Although cholinergic receptors are present at the junction between photoreceptors and the retinal pigment epithelium (RPE), human studies of the effects of OP poisoning on the visual pathways are very few. This study aims to demonstrate the pattern of changes in retina and post retinal pathways in patients with acute OP poisoning using visual electrophysiological tests. METHODS: This is an observational, cross-sectional study conducted at the Neurophysiology Unit, Teaching Hospital, Peradeniya, Sri Lanka. We tested 16 patients recovered from cholinergic phase, at least 24 h after deatropinization and within 8 weeks of OP ingestion. We assessed the functional integrity of the photoreceptors and ganglion cells of the macula by pattern electroretinography (PERG); RPE by electro-oculography (EOG); and post retinal pathways by pattern reversal visual evoked potentials (PR-VEP). Latencies and amplitudes of PR-VEP and PERG, light peak (LP), dark trough (DT) and Arden ratio of EOG were determined in patients and compared with 16 controls using the Mann-Whitney U test. RESULTS: Of the 16 OP-poisoned patients (median age of 37 ± IQR 20 years), six (37.5%) had reduced Arden ratio with reference to the International Society of Clinical Electrophysiology of Vision cut-off value of 1.7. The median Arden ratio in patients (1.69 ± IQR 0.36) was significantly lower compared to controls (1.90 ± IQR 0.4). The median latencies and amplitudes of PR-VEP or PERG were not significantly different between patients and controls. However, three patients had prolonged P100 latencies in PR-VEP and one had prolonged P50 latency in PERG. CONCLUSIONS: Acute OP poisoning seems to affect the functions of the RPE and the visual electrophysiological changes outlast the cholinergic phase. Limited evidence suggests that photoreceptors of the macula region and post retinal pathway might be affected in some patients.

Electro-oculography in bilateral optic neuropathy.

OBJECTIVE: Effect of bilateral, optic neuropathy on the function of retinal pigment epithelium has not been investigated extensively to date. This study aimed to determine the effect of bilateral, optic neuropathy on light peak:dark trough ratio, light peak and dark trough values of electro-oculography. Thirty-seven patients with a clinical diagnosis of bilateral optic neuropathy and 40 control subjects were recruited in this observational, cross-sectional study, carried out at the Neurophysiology unit, Teaching Hospital, Peradeniya, Sri Lanka. Pattern reversal visual evoked potentials, pattern electroretinography and electro-oculography were recorded in all of them. RESULTS: Twenty-four patients (64.9%) had reduced light peak:dark trough ratio values. The median light peak:dark trough ratio ± inter quartile range of the patient group (1.50 ± 0.4) was significantly lower than that of the controls (1.80 ± 0.2), (p < 0.001). Median dark trough value was significantly higher in patients compared to the control value. These changes may be due to higher conductance of ion channels in the retinal pigment epithelium, sub retinal space creation, changes in choroidal circulation or secondary to photoreceptor abnormalities in the macular region. These results indicate that retinal pigment epithelium might be affected in bilateral optic neuropathy.