effects side ocular induced-Chemical  • 8 PART  

acetone, glycerol and isopropyl acetate. In medicine, it receives widespread use as an antiseptic for skin and instrumentation, including the antisepsis of applanation tonometer tips.

Ocular side effects

Direct ocular exposure

Certain 

1. Irritation – burning

2. Conjunctiva – hyperemia

3. Cornea

a.Abrasion

b.Punctate keratitis

Clinical significance

Isopropyl alcohol is well known to cause ocular surface irritation, epithelial keratitis and occasional corneal abrasion. Most commonly, isopropyl alcohol comes into contact with the eye surface during Goldmann applanation tonometry. Tonometer tips are frequently cleaned with a wipe saturated in 70% isopropyl alcohol or soaked for at least 5 minutes in a 70% solution (the method recommended by the US Center for Disease Control) and applied to the corneal surface. If this is done before the alcohol has completely dried, a familiar round epithelial defect, a burning sensation or frank eye pain may ensue. Another potential route of ocular injury includes pre-surgical preparation of the peri-ocular skin with alcohol wipes. Occupational exposures to isopropyl alcohol vapors have been reported to cause eye irritation but no significant injury.

Recommendations

As with most chemical eye injuries, rapid irrigation with iso­ tonic saline or sterile water is the best first aid. Unlike methanol, drinking isopropyl alcohol, although potentially fatal, does not cause loss of vision.

References and Further Reading

Griffith JF, Nixon GA, Bruce RD, et al. Dose-response studies with chemical­ irritants in the albino rabbit eye as a basis for selecting optimum­ testing conditions for predicting hazard to the human eye. Toxicol Appl Pharmacol 55(3): 501–513, 1980.

Mac Rae SM, Brown B, Edelhauser HF. The corneal toxicity of presurgical skin antiseptics. Am J Ophthalmol 97(2): 221–232, 1984.

Roseman MJ, Hill RM. Aerobic responses of the cornea to isopropyl alcohol, measured in vivo. Acta Ophthalmol (Copenh) 65(3): 306–312, 1987.

Segal WA, Pirnazar JR, Arens M, Pepose JS. Disinfection of Goldmann tonometers after contamination with hepatitis C virus. Am J Ophthalmol 131(2): 184–187, 2001.

Smeets MA, Maute C, Dalton PH. Acute sensory irritation from exposure to iso propanol (2-propanol) at TLV in workers and controls: objective versus subjective effects. Ann Occup Hyg 46(4): 359–373, 2002.

Smith CA, Pepose JS. Disinfection of tonometers and contact lenses in the office lenses in the office setting: are current techniques adequate? Am J Ophthalmol 127(1): 77–84, 1999.

Soukiasian SH, Asdourian GK, Weiss JS, Kachadoorian HA. A complication from alcohol-swabbed tonometer tips. Am J Ophthalmol 105(4): 424–425, 1988.

Generic name: Methanol.

Synonyms: Methyl alcohol, wood alcohol, wood spirits.

Proprietary names/products containing: Found in

automobile engine cleaners, antifreeze, de-icers and paint/stain removers.

Primary use

Known as wood alcohol, methanol was once produced by the distillation of wood. It is now produced synthetically. Methanol is the simplest alkyl alcohol. It is used primarily as a solvent and as an antifreeze. It is also found in several cleaners and is used to denature ethanol. Methanol occurs in small amounts naturally in the environment.

Ocular side effects

Topical ocular exposure

Possible

1. Irritation

Systemic exposure

Certain

1. Blindness

2. Blurred vision

3. Optic atrophy

4. Optic disc hyperemia

5. Visual field defects

6. Decreased pupil reactions.

7. Death

Clinical significance

Many unfortunate accidents involving the consumption of methanol have been recorded in the literature. Methanol is often used to denature ethanol for industrial uses, and as its odor is milder and sweeter than ethanol, so its presence in denatured alcohol is difficult to detect. People may accidentally consume methanol while consuming what they believe to be unadulterated ethanol. A report of multiple victims of methanol toxicity in Port Moresby, Papua New Guinea showed that a dose-related response exists with ocular effects ranging from none to blindness. With consumption of higher volumes, vision loss often precedes death. Rarely, significant systemic toxicity may occur via percutaneous or inhalational exposure.

Temporary reactions to systemic methanol exposure include peripapillary edema, optic disc hyperemia, diminished pupillary reactions and central scotomata. Permanent ocular abnormalities include decreased visual acuity, blindness, optic disc pallor, ­attenuation or sheathing of arterioles, diminished pupillary ­reaction to light and visual field defects. MRI studies have shown one location of neurological damage from methanol to be in the putamen. Pathologic studies reveal that methanol probably ­damages mitochondria in the photoreceptors.

Recommendations

People who are suspected to have ingested methanol need immediate care, preferably in an intensive care unit setting. Treatment of systemic methanol poisoning consists of trying to prevent the metabolism of methanol to formaldehyde, which then is converted to formic acid. Formic acid inhibits cytochrome oxidase, a key protein in the production of ATP within mitochondria, and its formation is thought to precipitate the neurological side effects of methanol consumption. Peak concentrations of methanol occur within an hour of ingestion. A latent period occurs while the methanol is converted to formic acid, and a metabolic acidosis ensues. Visual loss often precedes the potentially fatal side effects of the formic acidosis. To block the metabolism towards formic acid, competitive inhibition of alcohol dehydrogenase may be achieved by giving the patient ethanol or fomepizole (which does not cause inebriation). Hemodialysis may enhance the elimination of methanol and its metabolic byproducts, allowing improved chances of recovery.