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BLIND AND PAINFUL EYE Retrobulbar injection of either absolute or 95% ethanol may provide relief from chronic pain associated with a blind and painful eye. Retrobulbar chlorpro-mazine also has been used. This treatment is preceded by administration of local anesthesia. Local infiltration of the ciliary nerves provides symptomatic relief from pain, but other nerve fibers may be damaged, causing paralysis of the extraocular muscles, including those in the eyelids, or neu-roparalytic keratitis. The sensory fibers of the ciliary nerves may regenerate, and repeated injections sometimes are needed.

SYSTEMIC AGENTS WITH OCULAR SIDE EFFECTS Just as certain systemic diseases have ocular manifestations, certain systemic drugs have ocular side effects. These can range from mild and inconsequential to severe and vision threatening.

Retina Numerous drugs have toxic side effects on the retina. The antiarthritis and antimalarial medicines hydroxychloroquine (plaquenil) and chloroquine can cause a central retinal toxicity. With normal dosages, toxicity does not appear until about 6 years after the drug is started. Stopping the drug will not reverse the damage but will prevent further toxicity. Sildenafil (viagra) inhibits PDE5 in the corpus cavernosum for the purpose of helping to achieve and maintain penile erection. The drug also mildly inhibits PDE6, which controls the levels of cyclic GMP in the retina. Visually, this can result in seeing a bluish haze or experiencing light sensitivity. Although no retinal damage has been reported, no long-term studies have been reported. Two newer PDE5 inhibitors, vardenafil (levitra) and tadalafil (cialis), are associated with similar visual disturbances.

Optic Nerve Multiple medications can cause a toxic optic neuropathy characterized by gradually progressive bilateral central scotomas and vision loss. There can be accompanying optic nerve pallor. These medicines include ethambutol, chloramphenicol, and rifampin. Systemic or ocular glucocorticoids can cause elevated IOP and glaucoma. If the glucocorticoids cannot be stopped, glaucoma medications, and even filtering surgery, often are required.

Anterior Segment Glucocorticoids also have been implicated in cataract formation. If vision is reduced, cataract surgery may be necessary. Rifabutin, if used in conjunction with clarithromycin or fluconazole for treatment of Mycobacterium avium complex (MAC) opportunistic infections in AiDS, is associated with an iridocyclitis and even hypopyon. This will resolve with glucocorticoids or by stopping the medication.

Ocular Surface Isotretinoin (accutane) has a drying effect on mucous membranes and is associated with dry eye.

corneal side effects of systemic medications The cornea, conjunctiva, and even eyelids can be affected by systemic medications. One common drug deposit found in the cornea is from the cardiac medication amiodarone. it deposits in the inferior and central cornea in a whorl-like pattern termed cornea verticillata. It appears as fine tan or brown pigment in the epithelium that seldom affects vision and rarely causes discontinuation. The deposits disappear slowly if the medication is stopped. Other medications can cause a similar pattern, including indomethacin, atovaquone, chloroquine, and hydroxychloroquine.

The phenothiazines, including chlorpromazine and thioridazine, can cause brown pigmentary deposits in the cornea, conjunctiva, and eyelids. The deposits generally are found in Descemet's membrane and the posterior cornea and typically do not affect vision. The ocular deposits generally persist after discontinuation of the medication and can even worsen, perhaps because the medication deposits in the skin are slowly released and accumulate in the eye. Tetracyclines can cause a yellow discoloration of the light-exposed conjunctiva. Systemic minocycline can induce a blue-gray scleral pigmentation that is most prominent in the interpalpebral zone.

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