Monitor drug use for clues to optic neuropathy causes

Physicians at the NANOS meeting discuss causes and treatment of optic neuritis and other conditions.

MONT TREMBLANT, Canada — Physicians discussed the causes of optic neuritis and pearls for its diagnosis at the annual North American Neuro-Ophthalmology (NANOS) meeting held here.

Optic neuritis can stem from many causes and is sometimes confused with other conditions that arise. Several physicians at the meeting discussed an assortment of neuropathies and how to address each.

Optic neuropathy

Paul W. Brazis, MD, of Jacksonville, U.S.A., spoke about how drugs can induce optic neuritis, pseudotumor cerebri or pupil dysfunctions. Because medicines can cause various neuropathies, a review of the drugs a patient takes becomes a crucial way of eliminating a toxic etiology for the condition.

“In my mind, any drug that’s any good can cause an optic neuropathy,” Dr. Brazis said. Patients may not mention a particular drug because they feel it is unimportant or they take it only occasionally.

Patients may not mention they take Viagra (sildenafil, Pfizer), for example.

And sometimes physicians may take note of the drug but not act upon the information.

“The worst error I can make is to not know what a drug is. I’ll write it down and leave it out, and that’s the one that I really should be learning about and thinking about,” he said. “There’s a problem with the patients not giving you the right data, but also of you not giving the right data.

He later added, “For any person that comes to your office that has any neuro-ophthalmic problem, you need to stress how important it is to find out what drugs they are taking. Not only the usual dose, but also supplements. Look those drugs up.”

Dr. Brazis conducts tests to screen for medication-induced optic neuropathies. A magnetic resonance image can eliminate compressive optic neuropathies. Physicians also need to check for syphilis, tumors or Leber’s hereditary optic neuropathies.

Dr. Brazis conducted an informal survey about how physicians follow the administration of ethambutol. Responses ranged from testing color vision every 6 months to testing Amsler grid, central 20° fields and visual potentials every 3 months.

The cardiac disease drug amiodarone can cause neuro-ophthalmic consequences.

“There definitely seems to be a drug effect,” he said. “Optic neuropathy is real and some of these people can improve by discontinuing the drug.”

Anabolic steroids can cause pseudotumor cerebri, as can vitamin A and nonsteroidal anti-inflammatory drugs.

And most eye whitening drops are said not to affect the pupil unless the eye is abraded. However, contact lens use seems to be enough to lead to dilated pupils, Dr. Brazis said. Flea collars and insecticides also cause pupil problems. People who pet their cat and then rub their eyes can induce small pupils.

AION in young patients

Although most physicians have seen acute ischemic optic neuropathy (AION) in patients less than 50 years old, it has never been examined in an organized way, said Anthony Arnold, MD, of Los Angeles. “I have the impression that I’m seeing it more often and seeing more bilaterally,” he said.

Typical AION occurs after age 50. Young patients have rarely been reported, and there are risk factors involved, such as diabetes, hypertension in young children, migraines, chronic renal failure and dialysis. “There is some evidence that there may be a higher recurrence rate in young AION, but it is so rare that it is hard to get a handle on the percentages,” he said.

To learn the answer, Dr. Arnold conducted a descriptive review of all the cases of AION seen at Jules Stein Eye Institute from 1986 to 1991. He used the criteria of acute optic nerve dysfunction, optic disk edema that resolved by 2 months, lack of pain, lack of visual recovery, and a loss of three lines of visual acuity and 3 dBs of visual field.

From the charts, 44 patients met the criteria. The patients ranged in age from 18 to 49 years old. In the study, 26 patients were less than 45 years old, 15 were less than 40 years old and seven were less than 35 years old. One probable risk factor was crowded disks in 86 of 88 eyes. Other factors included smoking, systemic hypertension, diabetes mellitus, vasculitis and migraines.

Fluorescein angiography revealed a segmental or diffuse optic disk filling delay of at least 5 seconds in 20 of 24 eyes that underwent the exam.

The retrospective study consisted of a small, biased sample and did not allow for comparisons among populations. However, Dr. Arnold said, fellow eye involvement seems a much more frequent recurrence, more frequent than in typical AION. Fluorescein angiography may aid in differentiation of AION from optic neuropathy in the under-50 age group.

New botulinum drug

In addition to optic neuropathies, physicians also discussed new treatment regimens for other conditions. A new form of botulinum toxin could offer help for previously unresponsive conditions, said Jonathan D. Wirtschafter, MD, of Minneapolis.

“Botox [botulinum toxin type A, Allergan] has had a tremendous effect on what we do in neuro-ophthalmology,” he said. “It’s been a very exciting drug for us because it’s permitted us to offer a whole variety of new therapy.”

Botulinum B has been tested for nonophthalmic purposes, and information about blepharospasm and extraocular muscles are not available. The U.S. Food and Drug Administration has not approved the drug. However, Dr. Wirtschafter said that some information is available about the product already.

Botulinum B has the same duration of action as Botox, about 3 months. It requires refrigeration, not freezing, is more acidic and stings more. It may be possible to treat more than one patient per vial, especially in cosmetic cases that require lower doses.

Botulinum B may overcome the immune resistance generated by repeated Botox administration at high doses. It is likely that botulinum B will produce immune resistance as well, but the resistance will be independent of that to Botox.

Botox also has been reported for several new uses, including gustatory lacrimation stemming from aberrant growth of salivary gland nerve fibers. In one study, Botox doses of 3 mU showed efficacy for months, Dr. Wirtschafter said.

Botox also can help with Frey syndrome. Doses of 5 to 10 mU last for about 3 years.

“There are many new uses for Botox, and they are growing,” he said. “The main thing is to be aware of the botulinum toxin B and accommodate it into your practice when it is released.”

For Your Information:

Paul W. Brazis, MD, can be reached at 5120 Otter Creek Dr., Ponte Vedra, FL 32082 U.S.A.; +(1) 904-953-7102; fax: +(1) 904-953-7233. Dr. Brazis has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Jonathan D. Wirtschafter, MD, can be reached at the Dept. of Ophthalmology, Box 493 UMHC, 420 Delaware St. SE, Minneapolis, MN 55455 U.S.A.; +(1) 612-625-4400; fax: +(1) 612-626-3119. Dr. Wirtschafter has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Anthony C. Arnold, MD, can be reached at the Jules Stein Eye Inst., 100 Stein Plaza, UCLA, Los Angeles, CA 90095 U.S.A.; +(1) 310-825-4344; fax: +(1) 310-267-1918. Dr. Arnold has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.