Thickness of the cornea an important factor in considering treatment options for patients with glaucoma

Sep 12 2004

Thickness of the cornea, the thin, transparent layer covering the eye, may be an important factor in considering treatment options for patients with glaucoma, according to an article appearing in the September issue of The Archives of Ophthalmology, one of the JAMA/Archives journals.

According to information in the article, central corneal thickness (CTT) can effect the accuracy of intraocular pressure (IOP) measurements. Elevated intraocular pressure (pressure inside the eyeball) is a strong indicator of glaucoma, a disease of the optic nerve that can cause vision loss. Patients with decreased CCT measurements are at an increased risk for developing glaucoma, the article states.

Carolyn Y. Shih, M.D., of the Edward S. Harkness Eye Institute, Columbia University, New York, and colleagues evaluated the effect of CCT measurements on decisions regarding clinical management of 188 patients with glaucoma or suspected glaucoma.

The researchers measured CCT and IOP for each participant. Using an algorithm, the researchers adjusted the IOP measurements based on their findings from the CCT measurements. Adjustments in therapy—use of eye drops, or addition or cancellation of laser therapy or surgery—were recorded for patients whose IOP was adjusted by 1.5 mm Hg (millimeters of mercury, the unit of measurement for pressure inside the eye) or more based on the CCT findings (referred to in the paper as “measurement-significant adjustment”).

Of 188 patients, 105 (55.9 percent) had a measurement-significant adjustment in their IOP measurements, with 67 patients (35.6 percent) having adjustments between 1.5 and 3.0 mm Hg, with 38 patients (20.2 percent) having an outcomes-significant IOP adjustment. Sixteen patients (8.5 percent) had a change in eye drop therapy, four (2.1 percent) had a change regarding laser therapy, and six (3.2 percent) had a decision change regarding glaucoma surgery.

“Although some authors have reported that patients may be misdiagnosed because of the absence of CCT determination or the subsequent adjustment of IOP, we are not aware of any studies that have assessed the effect of CCT-associated IOP adjustments on glaucoma clinical management,” write the researchers.

“Based on our analysis, there appears to be clinical usefulness in the IOP corrections, as approximately 8 percent to 10 percent of the patients had a change in their medication therapy, about 2 percent had a change in the recommendation (or deferment) of laser procedures, and about 3 percent had a change in the recommendation (or deferment) of glaucoma incisional surgery,” write the authors.

They conclude: “… central corneal thickness has a significant effect on the clinical management of patients with glaucoma and glaucoma suspect [suspected glaucoma].”