Müller cell involvement in methanol-induced retinal toxicity

Late Functional and Morphological Findings after Methylalcohol Poisoning

AIM

The aim of the study was to determine the morphological and functional findings in a patient after methanol poisoning. Examination methods: The patient (male, 38 years old) was suffered methanol poisoning in eight years ago (2012). The following tests and examinations were performed: neurological visual field XR test (Medmont M700), retinal nerve fibre layer (RNFL), ganglion cell complex (GCC) and peripapillary vessel density (all using Avanti RTvue, Optovue), pattern electroretinography (PERG) and pattern visual evoked potential (PVEP) examination according to ISCEV methodology (Roland Consult Instrument) and brain MRI examination (Philips Achieva Dstream 3 T).

RESULTS

The biggest changes were found in RNFL and VD. PERG also showed damage to retinal ganglion cell axons. In left eye we determined decrease in oscillations (in comparison with contralateral eye) at N35-P50 and P50-N95. VEPs in both eyes were significantly reduced, almost inconspicuous in the left eye. Extension of latency time of P100 was not identified. Functional MRI showed a bilateral decrease in voxel activity with a greater decrease in the left eye. There were postmalatical changes in the dorsal parts of the putamen on MRI. The width of the optic nerve and chiasm was physiological.

CONCLUSION

Asymmetric damaging of RNFL and cortical centres of the brain were determined. We registered large pathological changes in VD, which are probably responsible for the deepening of optic nerve excavation and further loss of nerve fibers of retinal ganglion cells, which have not yet been described in the literature. Following these results is possible to define direct damage of nerve structures and blood vessels by toxins of methanol metabolism in the acute stage and upcoming reparation processes in following periods.

Comparison of the most favoured methods for the diagnosis of hepatic encephalopathy in liver transplantation candidates

OBJECTIVE

Hepatic encephalopathy (HE) is a common complication of liver insufficiency. While there is widespread acceptance of its importance, there is no consensus on how best to diagnose and monitor HE.

OBJECTIVE

To compare the four most favoured methods for the diagnosis of HE.

DESIGN

170 patients who were on the waiting list for liver transplantation as well as 86 healthy controls were included in the study. All patients and controls underwent the portosystemic encephalopathy syndrome test yielding the psychometric hepatic encephalopathy score (PHES), the repeatable battery for the assessment of neuropsychological status (RBANS), the inhibitory control test (ICT) and critical flicker frequency (CFF) measurement.

RESULTS

PHES and ICT targets had the best sensitivity (85.7% vs 85.7%) and specificity (96.5% vs 97.6%) for the diagnosis of overt HE. CFF showed inferior sensitivity (40.9%) for the diagnosis of HE and dependency from previous alcohol abuse (p=0.015). Multiple regression analysis showed that all test results apart from PHES were influenced by secondary diagnoses such as diabetes mellitus and renal insufficiency.

CONCLUSIONS

In the German population of patients awaiting liver transplantation, PHES is the most robust method for the diagnosis and follow-up of HE.

Examining the risk of methanol poisoning from methyl acetate-containing products

OBJECTIVES

This retrospective study aims to review California Poison Control System data to qualitatively describe reported methyl acetate (MA) exposures and determine if a metabolic acidosis develops.

METHODS

We queried the Poison Control System data between January 1997 and December 1, 2010. Inclusion criteria were single MA ingestions.

RESULTS

Eighty-three cases were analyzed. Females made up 52% of study subjects. Seventy-five cases (90%) were 5 years or younger. Most (93%) ingestions were unintentional. Sixty-two cases (75%) were referred to a health care facility (HCF). Of these, 75% of cases referred to an HCF had no effect, and 25% of cases had a minor effect. There were no major effects, including deaths reported. One case received single-dose activated charcoal, and 1 case received intravenous fluids as therapy. All other cases were observed only. Of all cases, including home-managed and HCF cases, 63 (76%) had no symptoms. Vomiting was observed in 12 cases (14%), drowsiness in 1 case, ataxia in 1 case, abdominal pain in 1 case, and throat/oral irritation in 5 cases. Fifty-three percent of cases referred to HCF had at least 1 chemistry panel done (27% had >1 chemistry panel done). One patient had a mild metabolic acidosis without symptoms that resolved after a period of observation. There was no renal dysfunction.

CONCLUSION

These data suggest that minor ingestions of MA may be observed at home, but a prospective study is needed to exclude the risk of home observation.

Molecular and biochemical characterization of folate transport proteins in retinal Müller cells

PURPOSE

To analyze the mechanisms of folate uptake in retinal Müller cells.

METHODS

RT-PCR and Western blot analysis were performed in freshly isolated neural retina and RPE/eyecup, primary mouse Müller cells, and rMC-1 cells for the three known folate transport proteins folate receptor alpha (FRalpha), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Laser scanning confocal microscopy (LSCM) and immunoelectron microscopy were used to determine the subcellular location of FRalpha and PCFT in primary Müller cells. The pH dependence of the uptake of [(3)H]-methyltetrahydrofolate ([(3)H]-MTF) was assayed in Müller cells in the presence/absence of thiamine pyrophosphate, an inhibitor of RFC.

RESULTS

FRalpha and PCFT are expressed abundantly in the retina in several cell layers, including the inner nuclear layer; they are present in primary mouse Müller cells and rMC-1 cells. LSCM localized these proteins to the plasma membrane, nuclear membrane, and perinuclear region. Immunoelectron microscopic studies revealed the colocalization of FRalpha and PCFT on the plasma membrane and nuclear membrane and within endosomal structures. Müller cell uptake of [(3)H]-MTF was robust at pH 5.0 to 6.0, consistent with PCFT activity, but also at neutral pH, reflecting RFC function. RFC was expressed in mouse Müller cells that had been allowed to proliferate in culture, but not in freshly isolated primary cells.

CONCLUSIONS

FRalpha and PCFT are expressed in retinal Müller cells and colocalize in the endosomal compartment, suggesting that the two proteins may work coordinately to mediate folate uptake. The unexpected finding of RFC expression and activity in cultured Müller cells may reflect the upregulation of this protein under proliferative conditions.

Ocular and systemic safety evaluation of calcium formate as a dietary supplement

PURPOSE

The objective of this study was to perform a preliminary evaluation of the ocular and systemic safety of calcium formate, a dietary calcium supplement for prevention and management of osteoporosis. Although formate is an endogenous product of metabolism, high concentrations are associated with toxicity during methanol overdose.

METHODS

In this prospective clinical trial, 12 healthy women ingested calcium formate (1,300 mg) three times a day for 14 days. Study evaluations included physical and ocular examination, extensive laboratory testing, serum calcium and formate levels, Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, color vision, visual fields, visual evoked potential (VEP), and full-field, pattern, and multifocal electroretinograms (MERG).

RESULTS

The mean baseline serum level of formate was 0.572 +/- 0.06 mM. Peak serum levels and final serum formate did not differ significantly from baseline. The final concentration was 0.582 +/- 0.091 mM. Accumulation of serum formate did not occur. There was also no evidence of toxicity with calcium formate ingestion. All examinations and tests remained normal, including optic nerve and retinal function. Three subjects had mild transient symptoms attributable to any calcium formulation.

CONCLUSIONS

Calcium formate is highly bioavailable and well-tolerated. Serum formate remained at basal levels and did not accumulate with repeated dosing. Systemic and ocular safety was demonstrated by objective testing. Given its high oral bioavailability, calcium formate may be a good choice for calcium supplementation in the prevention and management of osteoporosis. Further study will be needed to evaluate its long-term safety in a larger group of subjects representing more varied age, health, dietary, and nutritional status.

Cellular signaling and factors involved in Müller cell gliosis: neuroprotective and detrimental effects

Müller cells are active players in normal retinal function and in virtually all forms of retinal injury and disease. Reactive Müller cells protect the tissue from further damage and preserve tissue function by the release of antioxidants and neurotrophic factors, and may contribute to retinal regeneration by the generation of neural progenitor/stem cells. However, Müller cell gliosis can also contribute to neurodegeneration and impedes regenerative processes in the retinal tissue by the formation of glial scars. This article provides an overview of the neuroprotective and detrimental effects of Müller cell gliosis, with accounts on the cellular signal transduction mechanisms and factors which are implicated in Müller cell-mediated neuroprotection, immunomodulation, regulation of Müller cell proliferation, upregulation of intermediate filaments, glial scar formation, and the generation of neural progenitor/stem cells. A proper understanding of the signaling mechanisms implicated in gliotic alterations of Müller cells is essential for the development of efficient therapeutic strategies that increase the supportive/protective and decrease the destructive roles of gliosis.

Non-P450 aldehyde oxidizing enzymes: the aldehyde dehydrogenase superfamily

BACKGROUND

Aldehydes are highly reactive molecules. While several non-P450 enzyme systems participate in their metabolism, one of the most important is the aldehyde dehydrogenase (ALDH) superfamily, composed of NAD(P)+-dependent enzymes that catalyze aldehyde oxidation.

OBJECTIVE

This article presents a review of what is currently known about each member of the human ALDH superfamily including the pathophysiological significance of these enzymes.

METHODS

Relevant literature involving all members of the human ALDH family was extensively reviewed, with the primary focus on recent and novel findings.

CONCLUSION

To date, 19 ALDH genes have been identified in the human genome and mutations in these genes and subsequent inborn errors in aldehyde metabolism are the molecular basis of several diseases, including Sjögren-Larsson syndrome, type II hyperprolinemia, gamma-hydroxybutyric aciduria and pyridoxine-dependent seizures. ALDH enzymes also play important roles in embryogenesis and development, neurotransmission, oxidative stress and cancer. Finally, ALDH enzymes display multiple catalytic and non-catalytic functions including ester hydrolysis, antioxidant properties, xenobiotic bioactivation and UV light absorption.

Formaldehyde at low concentration induces protein tau into globular amyloid-like aggregates in vitro and in vivo

Recent studies have shown that neurodegeneration is closely related to misfolding and aggregation of neuronal tau. Our previous results show that neuronal tau aggregates in formaldehyde solution and that aggregated tau induces apoptosis of SH-SY5Y and hippocampal cells. In the present study, based on atomic force microscopy (AFM) observation, we have found that formaldehyde at low concentrations induces tau polymerization whilst acetaldehyde does not. Neuronal tau misfolds and aggregates into globular-like polymers in 0.01–0.1% formaldehyde solutions. Apart from globular-like aggregation, no fibril-like polymerization was observed when the protein was incubated with formaldehyde for 15 days. SDS-PAGE results also exhibit tau polymerizing in the presence of formaldehyde. Under the same experimental conditions, polymerization of bovine serum albumin (BSA) or α-synuclein was not markedly detected. Kinetic study shows that tau significantly misfolds and polymerizes in 60 minutes in 0.1% formaldehyde solution. However, presence of 10% methanol prevents protein tau from polymerization. This suggests that formaldehyde polymerization is involved in tau aggregation. Such aggregation process is probably linked to the tau's special “worm-like” structure, which leaves the ε-amino groups of Lys and thiol groups of Cys exposed to the exterior. Such a structure can easily bond to formaldehyde molecules in vitro and in vivo. Polymerizing of formaldehyde itself results in aggregation of protein tau. Immunocytochemistry and thioflavin S staining of both endogenous and exogenous tau in the presence of formaldehyde at low concentrations in the cell culture have shown that formaldehyde can induce tau into amyloid-like aggregates in vivo during apoptosis. The significant protein tau aggregation induced by formaldehyde and the severe toxicity of the aggregated tau to neural cells may suggest that toxicity of methanol and formaldehyde ingestion is related to tau misfolding and aggregation.

Amyloid-like aggregates of neuronal tau induced by formaldehyde promote apoptosis of neuronal cells

Background

The microtubule associated protein tau is the principle component of neurofibrillar tangles, which are a characteristic marker in the pathology of Alzheimer's disease; similar lesions are also observed after chronic alcohol abuse. Formaldehyde is a common environmental contaminant and also a metabolite of methanol. Although many studies have been done on methanol and formaldehyde intoxication, none of these address the contribution of protein misfolding to the pathological mechanism, in particular the effect of formaldehyde on protein conformation and polymerization.

Results

We found that unlike the typical globular protein BSA, the natively-unfolded structure of human neuronal tau was induced to misfold and aggregate in the presence of ~0.01% formaldehyde, leading to formation of amyloid-like deposits that appeared as densely staining granules by electron microscopy and atomic force microscopy, and bound the amyloid-specific dyes thioflavin T and Congo Red. The amyloid-like aggregates of tau were found to induce apoptosis in the neurotypic cell line SH-SY5Y and in rat hippocampal cells, as observed by Hoechst 33258 staining, assay of caspase-3 activity, and flow cytometry using Annexin V and Propidium Iodide staining. Further experiments showed that Congo Red specifically attenuated the caspase-3 activity induced by amyloid-like deposits of tau.

Conclusion

The results suggest that low concentrations of formaldehyde can induce human tau protein to form neurotoxic aggregates, which could play a role in the induction of tauopathies.

Modulation of fatty acid methyl esters in rats pretreated with tri-o-tolyl phosphate

Formation and toxicity of fatty acid methyl esters (FAMEs) have been reported both in vitro and in vivo. In previous studies, it was shown that fatty acid ethyl ester synthase (FAEES), which catalyzes the formation of FAMEs, also expresses esterase activity. Therefore, it was hypothesized that inhibitors of esterases such as tri-o-tolyl phosphate (TOTP) can modulate the formation of FAMEs. To test this, four groups of rats were used. Group 1 served as control (vehicle only). Group 2 was treated with methanol only (3 g/kg via gavage), group 3 was given TOTP only (100 mg/kg i.p. in corn oil), and group 4 was administered TOTP as in group 3, followed by methanol after 18 h. Three hours after exposure, animals were sacrificed and FAEES activity and FAME levels were measured in blood, liver, pancreas, and brown fat. About 95% of FAEES activity was inhibited in the liver and whole blood of TOTP-treated rats (group 3) but no inhibition was observed in the pancreas or brown fat. Total hepatic FAMEs were found to be lowest for the TOTP-treated group (3) and highest in the methanol-treated animals (group 2). Total pancreatic FAMEs in different groups were not statistically different, while significant increases were observed in the brown fat in both methanol-treated groups. To verify that the oxidative metabolism of methanol was unaffected by TOTP, alcohol dehydrogenase activity was also measured and found to be unchanged in any group as compared to control. These results demonstrate that the formation of FAMEs can be modulated in the liver and probably in blood, but not in the pancreas or brown fat by the inhibitors of FAEES.

Gene transfer to the nonhuman primate retina with recombinant feline immunodeficiency virus vectors

We hypothesize that recombinant feline immunodeficiency viral (rFIV) vectors may be useful for gene transfer to the nonhuman primate retina. We performed vitrectomies and subretinal injections in the right eyes of 11 cynomolgus monkeys. Vesicular stomatitis virus glycoprotein-pseudotyped rFIV that expressed the Escherichia coli beta-galactosidase gene was injected into eight eyes. Sham vehicle or lactose buffer injections were also performed in two of these eight study eyes. rFIV pseudotyped with an amphotropic envelope was used in two eyes, and in one animal injections of lactose buffer only were given. After surgery the animals were clinically evaluated by retinal photography and electroretinography. beta-Galactosidase expression was evaluated, at a final end point, in histological sections. We found photoreceptor and Müller cells to have the greatest transgene expression. Focal inflammatory responses localized to the injection site were seen histologically in all eyes. No difference in transduction efficiency was seen between injections near the macula and more peripheral injections. Visual function as assessed by electroretinography was not significantly affected by vector or vehicle injections. We conclude that rFIV vectors administered beneath the retina can transduce a variety of retinal cells in the nonhuman primate retina. rFIV vectors have therapeutic potential and could be exploited to develop gene therapy for the human eye.

The effects of vigabatrin on electrophysiology and visual fields in epileptics: a controlled study with a discussion of possible mechanisms

PURPOSE

To compare the visual electrophysiology and visual fields of patients taking vigabatrin to those of a control group of epileptics on other anti-epileptic drugs (AEDs).

METHODS

Fourteen epileptics treated with vigabatrin and 10 control patients treated with other AEDs underwent ERG and EOG. Goldmann visual fields were performed and analysed using standard software to measure areas contained within I4e isopters.

RESULTS

The cone and rod b-waves of the ERG, the oscillatory potential amplitudes and Arden indices were reduced in vigabatrin-treated subjects and the oscillatory potentials delayed. The Arden indices were reduced due to an increased dark trough. The areas contained within the I4e isopter of vigabatrin treated subjects were reduced compared to the control group and these areas correlated well with oscillatory potential amplitudes and b-wave amplitudes in the vigabatrin group only.

CONCLUSIONS

The use of vigabatrin is associated with a reduction of the ERG cone b-wave amplitude and oscillatory potentials which correlates with visual field loss. The Arden ratio is reduced in subjects taking vigabatrin but may recover after cessation. However, visual loss may persist in the presence of a recovered EOG. These findings suggest further effects of the drug than those mediated by GABA receptors, and support the contention that the cause of the field loss may be at least in part due to retinal effects. Possible mechanisms are discussed.

Evoked potentials investigation of visual dysfunction after methanol poisoning

OBJECTIVE

To present results of electrophysiologic investigations of the visual toxicity observed during the early stage of methanol poisoning.

DESIGN

Retrospective, clinical study.

SETTING

A 7-bed intensive care unit in a university hospital.

PATIENTS

Nineteen patients admitted with a diagnosis of acute methanol poisoning.

INTERVENTIONS

Visual evoked potentials were obtained within the first 48 hrs after admission; a clinical follow-up examination was performed in 11 patients, and 12 patients were followed up by visual evoked potentials beyond the same delay. Correlations between the occurrence of an optic neuropathy and clinical, biological, and electrophysiological data were studied.

MEASUREMENTS AND MAIN RESULTS

A significant correlation was found between arterial pH and blood formate concentration (r2 = 0.58, p = .003), between blood formate and bicarbonate concentrations (r2 = 0.36, p = .02), and between delay from ingestion and blood formate concentration (r2 = 0.44, p = .017). Clinical outcome was correlated not only with the bicarbonate (p = .007), formate (p = .018), and methanol (p = .03) concentrations and arterial pH (p = .004) but also with a well-defined electrophysiologic pattern during the acute stage. An index of global cortical functioning > or =3 was associated with death, whereas a global cortical functioning index < or =2 was associated with survival (p = .0058). Moreover, a statistically significant difference in long-term visual impairment was found between the subgroup with abnormal wave III morphology or a global cortical functioning index of 1-2 and the subgroup with normal wave III morphology and a global cortical functioning index <1 (p = .015). Results of the electrophysiologic studies were expressed as retinal dysfunction and optic nerve injury. Five patients had normal findings on electrophysiologic examination. Ten patients had early signs of retinal dysfunction that were fully reversed in the eight patients who were followed. Ten patients had persistent electrophysiologic signs of optic neuropathy.

CONCLUSIONS

Although reversible retinal dysfunction is evident in the early stage of human methanol poisoning, its absence does not preclude development of optic neuropathy. The occurrence of optic neuropathy and early electrophysiologic data are correlated.

Comments on the purported generation of formaldehyde and adduct formation from the sweetener aspartame

A recent paper by Trocho et al. (1) describes experiments meant to show that formaldehyde adducts are formed when rats are administered the sweetener aspartame. These authors assume that the methanol carbon of aspartame generates formaldehyde which then forms adducts with protein, DNA, and RNA. Doses employed range widely. In this letter, studies which have been published previously and which were not cited by these authors are reviewed in order to put into perspective the disposition of methanol and formaldehyde in monkeys and humans, species relevant to the toxicity of methanol and its toxic metabolite, formic acid.

Chloral hydrate enhances ethanol-induced inhibition of methanol oxidation in mice

Several studies indicated that chloral hydrate can prolong the disappearance time of ethanol from blood in mice. This seems to result from inhibition of the enzyme alcohol dehydrogenase by chloral hydrate and trichloroethanol, its main metabolite. We examined the effect of both these compounds on the disappearance time of methanol in mice. Also the effect of a combination of ethanol and chloral hydrate on the disappearance time of methanol was examined. Several groups of six mice each received methanol (1 g/kg i.p.) followed immediately by one of the following treatments: saline (10 ml/kg); chloral hydrate (0.4 g/kg); trichloroethanol (0.36 g/kg); ethanol (4 g/kg); or a combination of chloral hydrate (0.2 g/kg) and ethanol (4 g/kg). The concentrations of methanol in blood were measured at 1, 2, 4, and 8 h after its administration and were used to calculate some approximate indicators of methanol elimination in each group. The results show that all the above treatments do prolong the disappearance time of methanol in the blood of mice to varying extents. The ethanol-chloral hydrate combination produced the most pronounced effect.

Potential health effects of gasoline and its constituents: A review of current literature (1990-1997) on toxicological data

We reviewed toxicological studies, both experimental and epidemiological, that appeared in international literature in the period 1990-1997 and included both leaded and unleaded gasolines as well as their components and additives. The aim of this overview was to select, arrange, and present references of scientific papers published during the period under consideration and to summarize the data in order to give a comprehensive picture of the results of toxicological studies performed in laboratory animals (including carcinogenic, teratogenic, or embryotoxic activity), mutagenicity and genotoxic aspects in mammalian and bacterial systems, and epidemiological results obtained in humans in relation to gasoline exposure. This paper draws attention to the inherent difficulties in assessing with precision any potential adverse effects on health, that is, the risk of possible damage to man and his environment from gasoline. The difficulty of risk assessment still exists despite the fact that the studies examined are definitely more technically valid than those of earlier years. The uncertainty in overall risk determination from gasoline exposure also derives from the conflicting results of different studies, from the lack of a correct scientific approach in some studies, from the variable characteristics of the different gasoline mixtures, and from the difficulties of correctly handling potentially confounding variables related to lifestyle (e.g., cigarette smoking, drug use) or to preexisting pathological conditions. In this respect, this paper highlights the need for accurately assessing the conclusive explanations reported in scientific papers so as to avoid the spread of inaccurate or misleading information on gasoline toxicity in nonscientific papers and in mass-media messages.

Was Dom Perignon really blind?

Many sources perpetuate the tripartite myth that Dom Perignon was the blind inventor of champagne, whose senses of taste and smell were enhanced by his loss of vision. This myth, however, is seemingly contradicted by historical fact. Not only do ancient references suggest that sparkling wine existed long before Perignon's time, but the making of champagne was a scientific process that required careful measuring, weighing, and record keeping, and it is unlikely that Perignon was blind when he was perfecting champagne. While the truth regarding Dom Perignon's blindness has disappeared during the more than two and a half centuries since his death, it is interesting to speculate why he may have lost vision at some stage of life. A brief history of Perignon's discovery of the secret of champagne and the blindness myth is traced, and a differential diagnosis is given, including cataracts, uncorrected refractive error, alcohol toxicity, and champagne-related ocular/cerebral trauma.

Folate and 10-formyltetrahydrofolate dehydrogenase (FDH) expression in the central nervous system of the mature rat

10-Formyltetrahydrofolate dehydrogenase (10-FTHFDH) is a folate-binding protein that is important in folate metabolism. In addition, 10-FTHFDH catalyzes the rate-limiting step in hepatic folate-dependent formate oxidation. We measured folate concentrations and examined cellular 10-FTHFDH expression in regions of the adult rat central nervous system (CNS), to study components of CNS oxidative formate metabolism. Folate was detected in every CNS region studied; the concentrations ranged from 3 to 14% of that detected in the liver. Immunohistochemical expression of 10-FTHFDH was identified in many CNS structures. 10-FTHFDH was mostly expressed by glia, especially astrocytes and ventricular ependyma. Neuronal expression was weak but evident in the cerebral cortex, basal ganglia, cerebellum, and spinal cord. Thus, CNS tissue has the chief components of folate-dependent formate oxidation and the chief site of this oxidation appears to be glia.

Acute ocular methanol toxicity: clinical and electrophysiological features

PURPOSE

The present report describes previously undocumented changes in the electroretinogram (ERG) and visual-evoked response (VER) following acute methanol ingestion and highlights the ocular effects of methanol poisoning.

METHODS

Two cases of acute ocular damage following methanol ingestion are presented. One patient underwent extensive electrophysiological and psychophysical testing.

RESULTS

Both patients reported transient visual disturbances. In each patient vision was 6/6 in both eyes at presentation but subsequently improved to 6/4. Colour vision (Ishihara plates) and pupillary reactions were normal. The optic discs were hyperaemic and swollen and retinal oedema extended along the major vascular arcades. There was cystoid macular oedema and 'pseudo cherry red spots' were observed. Automated field analysis revealed a generalized depression of retinal sensitivity, an enlargement of one blind spot and paracentral scotomas. The scotopic ERG was subnormal with diminished a- and b-waveforms and the cone response to flicker was reduced. The pattern VER P2 waveform was normal in latency but decreased in amplitude.

CONCLUSIONS

Acute methanol ingestion can cause characteristic ocular damage, together with widespread electrophysiological dysfunction. The data presented suggest that methanol affects the photoreceptors, Muller cells and the retrolaminar portion of the optic nerve.