Filamentary keratitis is an irritating, light‐sensitizing overgrowth of degenerated corneal epithelial cells. The strands of cells are often multiple and most often due to aging, dry eye, and trauma. They may be removed with a Nd:YAG laser (Fig. 250), but may recur. Prevent by treating underlying cause.

Corneal vascularization is a response to injury. Superficial vessels are most commonly a response to poorly fitting contact lenses (Figs 253 and 255), but also grow into areas damaged from ulcers, lacerations, or chemicals.

Chemical injuries with basic chemicals such as lye are most ominous because they immediately penetrate the depths of the cornea and permanently scar (Figs 254 and 255). Acid burns usually do not penetrate the stroma or scar. Rx: irrigate all chemical injuries immediately and profusely.

Epidemic keratoconjunctivitis (Fig. 256) is a common, highly infectious condition due to one of the adenoviruses that cause the common cold. There may be a severe conjunctivitis lasting up to 3 weeks associated with photophobia, fever, cold symptoms, and an adenopathy. The main problem is the keratitis, which can last for months or, rarely, years. It rarely scars, but does restrict use of contact lenses until it clears. Wash your hands, instruments, chair, and doorknobs especially well after evaluating this eye infection. Diluted povidone‐iodine appears effective against virus in tears, but not replicating virus in cells. It may be placed topically in office and rinsed out in 2 minutes. Topical steroid may relieve symptoms but could prolong the course. Unlike most other viruses, this adenovirus can be hardy, and may be cultured from dry surfaces for weeks.

Herpes simplex virus type 1 (HSV‐1) is very common on the face, especially around the eyes and lips and is often triggered by stress. At age 4, about 25% of the population is seropositive, and this approaches 100% by age 60. When the corneal epithelium (Figs 257 and 258) is involved, the lesions, called dendrites, appear and are similar in appearance to a branching tree, especially when stained with fluorescein. Diffuse punctate or round lesions can also occur and mimic the lesions due to dry eye and blepharitis. Patients complain of a gritty ocular sensation, conjunctivitis, and a history of a fever sore on the lip, nose, or mouth. Herpes often decreases corneal sensation. This can be tested by comparing sensation in eye by touching both with a cotton‐tipped applicator, obviously testing the uninfected eye first. There may be small vesicles on the skin of the lids (Fig. 260), which often crust and then disappear within 3 weeks. Involvement of the surface epithelium of the cornea rarely causes scarring and loss of vision unlike the deeper stromal keratitis and uveitis. When the virus involvement does penetrate into the stroma (Fig. 259), cautious addition of topical corticosteroids, together with antivirals, may minimize this scarring and the resulting decrease in vision. This permanent structural change of the stroma, causing haze and loss of vision, when severe, accounts for three percent of all penetrating corneal transplants done in the USA. Recurrences are common. Rx: Generic trifluridine (Viroptic) 1% every 2 hours has been the mainstay treatment for years, but branded Zirgan gel, ganciclovir 0.15%, can be used every 3 hours and is less toxic. Both are usually used during waking hours. Acyclovir 500 mg PO BID may be added in resistant cases, or for systemic symptoms.

Anxious patients must be reassured that this HSV‐1 condition, causing corneal disease, is not usually due to HSV‐2, which is a venereal disease transmitted by sexual contact, although HSV‐2 can, less often, spread to the cornea.

Corneal ulcers are usually caused by a bacterial infection, although they may occasionally be the result of a viral, parasitic, or fungal infection. They are characterized by conjunctivitis with pain and white corneal infiltrates. Over 50% result from contact lens wear, especially lenses worn during sleep. Other causes often include corneal abrasions, conjunctivitis, and blepharitis. Treat vigorously on an emergency basis, since it almost always scars and, in the case of Pseudomonas, may perforate within 1 day (Figs 261–263). Treatment often consists of more than one antibiotic drop and ointment (see Table 8, p.70). The initial frequency of instillation may be as often as every 15 minutes through the night when the central visual axis is involved.

Marginal ulcers (Fig. 261) are most common and may be due to infection or an immune reaction to staphylococcus toxins from associated chronic blepharitis. Rx: topical hourly broad‐spectrum antibiotics (Table 8). Steroids are sometimes used to suppress the inflammation from staphylococcal toxins and when a herpetic cause is confidently ruled out. Treat the often present blepharitis with lid scrubs, warm compresses, and massage of the lid margin.

Central ulcers (Fig. 262

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