Cogan Corneal Dystrophy
Cogan corneal dystrophy is a disorder in which the cornea (the normally clear front window of the eye) shows grayish fingerprint lines, geographic map-like lines, and dots (or microcysts) on examination with a slit-lamp that focuses a high intensity light beam as a slit while the examiner looks at the front of the eye through a magnifying scope. The disorder is usually silent and without symptoms. However, about one patient in ten has recurrent erosion of the cornea that usually begins after the age 30. Conversely, half of patients with recurrent corneal erosions of idiopathic (unknown) origin have this disorder. Under the microscope, a structure called the epithelial basement membrane is abnormal so the disorder is sometimes called epithelial basement corneal dystrophy. The disorder was first described by Cogan in 1964. David Glendenning Cogan (1908-1993)
Although Cogan’s dystrophy rarely causes symptoms or reduces vision, the recurrent erosions require treatment. There are at least four treatment methods, depending on the severity: hypertonic solution and/or patching, hypertonic solution and contact lens, corneal transplant (penetrating keratoplasty) and phototherapeutic keratectomy (PTK).
Hypertonic solution and/or patching
Hypertonic eyedrops are administered every 3 or 4 hours during the day and an ointment is used at night for mild cases. For other cases, double patching of the eye for 48 hours, followed by an ointment at bedtime for weeks to months. In severe recurrent cases, it is usually effective to remove the redundant epithelium mechanically with a cotton tip applicator. This is done after instilling a topical anesthetic, followed by a cycloplegic (paralyzes the eye) and an antibiotic. The eye is patched for 48 hours.
Hypertonic solution and contact lens
In stubborn and recurrent cases the doctor may recommend the use of soft, loosely fitting, high-water-content contact lens in conjunction with eye drops.
Corneal transplant (penetrating keratoplasty)
A corneal transplant is done on an outpatient basis and lasts about an hour and a half. The patient is given a local anesthetic and light sedation. After the eye is numbed, an instrument similar to a cookie cutter is used to partially cut the cornea. The affected area (slightly smaller than the colored part of the eye) is removed and the new cornea is stitched on. The eye is then patched for the night. The stitches are kept in the eye for three to six months, and it takes up to a year to recover sharp vision.
Phototherapeutic keratectomy (PTK)
PTK may be an effective treatment in removing opacities from the superficial stroma, improving irregularities of the anterior surface of the cornea, and healing corneal epithelial defects.