Are you at risk for glaucoma? Hopkins specialists explain this common eye condition and report research that links cornea thickness with severity of the glaucoma.

Glaucoma occurs when the clear liquid in the front of the eye, called the aqueous humor, places enough pressure on the optic nerve to damage it. Often this damage is caused by elevated pressure within the eye, but in some cases normal pressure damages the nerve.

Internal pressure in the eye, or intraocular pressure (IOP), is primarily regulated by the aqueous humor. Continually manufactured by the ciliary body (a ring of tissue that is located behind the iris), aqueous humor flows through the pupil into the anterior chamber. After delivering nutrients to the lens and cornea, the fluid drains from the eye through a spongy network of connective tissue known as the trabecular meshwork. From these tiny channels, the fluid passes into a larger opening and eventually drains into the veins of the sclera (episcleral veins) for disposal.

Normally, the steady production and drainage of aqueous humor maintain a stable balance of fluid in the eye and keep IOP within a safe range. Open-angle glaucoma caused by high IOP may develop when, for unknown reasons, the trabecular meshwork becomes partially blocked, hindering the outflow of aqueous humor and throwing off the eye's fluid balance.

A study reported in the Archives of Ophthalmology (Volume 122, page 17) reveals that the thickness of the cornea is strongly correlated with the severity of the glaucoma. Researchers examined medical records that contained information on 190 patients and 350 eyes afflicted by glaucoma. They found that patients with thinner corneas consistently had worse cases of glaucoma and greater eye damage than those with thicker corneas. Corneal thickness was not, however, associated with the number of glaucoma medications taken by patients.

This study was the first to demonstrate that thinner corneas are predictive of more severe glaucoma. In addition, family history of glaucoma was associated with worse disease. The authors concluded that measuring corneal thickness may help ophthalmologists identify patients who are at higher risk for developing severe glaucoma-related problems and prompt them to treat their glaucoma more aggressively.

Used with permission. For further information see Johns Hopkins Medicine 2008 Vision White Paper, by Simeon Margolis, MD, PhD, www.johnshopkinshealthalerts.com/white_papers/vision_wp/main08_landing.html.