A 93-year-old gentleman presented with bilateral cataracts and corneal astigmatism. His BSCVA had gradually declined over the past decade from 20/20 OU to 20/50 OD and 20/40 OS pinholing to 20/30 OD and 20/25 OS. His manifest refraction was -3.00+4.25x10 OD and -2.25+3.75x175 OS.
Anterior segment exam revealed trace inferior corneal punctate staining and 4+ nuclear sclerotic cataracts with 3+ cortical changes OU. Retinal exam showed an epiretinal membrane OD and collateral optociliary shunt vessels at the optic nerve head OS from an old incipient hemiretinal vein occlusion with macular edema that resolved with an Avastin® injection.
The patient decided to proceed with cataract extraction and correction of astigmatism with toric IOL implants. He was instructed to lubricate his eyes at least qid with preservative free artificial tears, and when he returned for preop biometry there was no corneal staining. Corneal topography confirmed regular against-the-rule astigmatism, which corresponded with that determined by refraction and keratometry measurements:
Cataract surgeries were performed one month apart, OD then OS, and the patient used brand name topical drops postoperatively (i.e., Vigamox® tid for one week, Prolensa® qd for two months, and Lotemax® tid for one month then bid for one month because of the increased risk of postop macular edema from his retinal pathology).
After the first surgery, the patient attained a BSCVA of 20/25 with a refraction of -0.25+0.50x115 OD, and there was no corneal staining during the healing period. However, one week after the second surgery the patient was noted to have 2+ punctate central corneal staining without edema, and a BSCVA of 20/80 with a refraction of -0.25+0.25x175 OS.
The patient was questioned specifically about his eye drop usage, and he reiterated his strict adherence to the prescribed regimen with brand name drops. He was instructed to use preservative free lubricating drops at least qid OS. When the patient returned two weeks later, his visual acuity had deteriorated to 20/200 OS and the cornea showed 4+ punctate staining and irregular epithelium centrally:
Discussion
There was no anterior chamber reaction or posterior capsular opacity, the IOL was well centered, and the retinal exam was within normal limits. The patient was diagnosed with drug-induced corneal toxicity (medicamentosa) and was told to stop all topical eye drops except for lubrication. Over the following six weeks, the patient’s vision improved to 20/25 as the cornea healed.
This case demonstrates toxic keratitis caused by medication. The patient was at increased risk for medicamentosa because of his underlying mild dry eye condition and his advanced age. Usually, corneal drug toxicity is bilateral (although it can be asymmetric) and occurs between one week and three weeks after starting the inciting agent, so it is somewhat unusual that the patient developed corneal changes only in his left eye. Medicamentosa is also more commonly seen with generic eye drops and drops containing high levels of benzalkonium chloride (BAK).
The treatment is to reduce exposure to the offending drug by tapering or discontinuing it, or substituting a preservative free formulation of the drug if available, and to apply non-preserved lubricating drops. The earlier this condition is identified and treated, the quicker it resolves; however, severe cases of corneal toxicity (most notably with unopposed topical generic NSAIDS) can result in damage to limbal stem cells and corneal melting, which require more aggressive treatment.