Difference in Corneas May Affect Glaucoma Care

A new study indicates that African-Americans tend to have thinner corneas than Caucasians.

If these differences are not taken into account by physicians, they may affect the accuracy of measurements of pressure within the eye, which could lead to improper diagnosis and treatment of glaucoma in blacks, according to the study s authors.
Glaucoma, a disease characterized by high intraocular pressure (pressure within the eye), damages optic nerve fibers and can lead to progressive vision loss. The disease strikes about six times as many blacks as whites and is the leading cause of irreversible blindness in blacks. Blacks tend to develop the disease about 10 years earlier than whites.
One of the study s authors, Dr. Silvia Orengo-Nania, of the Houston Veterans Affairs Medical Center in Texas, said that intraocular pressure is one of several factors used to diagnose glaucoma. But she noted that the method used to calculate this pressure is based on a formula that assumes that the cornea is a standard shape and size. The cornea is the transparent portion of the eye that covers the iris and the pupil.
Given the racial differences in glaucoma rates, Orengo-Nania s team set out to detect racial differences in corneal thickness that might affect the diagnosis and treatment of the disease in blacks. They measured the corneas of 165 men--83 whites and 82 blacks--who were treated at the Houston VA Medical Center. The study included not only men who had confirmed or suspected glaucoma but also men with no signs of the disease.
The researchers detected a racial difference in central corneal thickness, with blacks tending to have significantly thinner corneas than whites. The differences were present in men with glaucoma and in men without the disease. They said they hope the results of the study will alert doctors to look for other factors besides pressure in the eye when diagnosing glaucoma.