Study Shows New Major Risk Factor for Glaucoma
Posted by Dr. J. R. Lacey, Therapeutic Optometrist
Thin Corneas are a Major Risk Factor for Glaucoma
A major national study called the Ocular Hypertension and Treatment Study (OHTS) proved that the thickness of the cornea is one of the most powerful predictors for the development of glaucoma. Eyes with a corneal thickness of 555 microns or less (thinner corneas) had a 300% greater risk of developing glaucoma than those eyes with a corneal thickness of 588 microns or more.
Eyes with thicker corneas show artificially higher intraocular pressure (IOP) readings when measured; and conversely, eyes with thinner corneas show artificially lower IOP readings. LASIK patients must always advise their eye doctors of their LASIK procedure so that the true IOP's can be calculated. This is perhaps the underlying issue of "normal tension (pressure) glaucoma" which accounts for 25-33% of all glaucoma patients. Normal tension glaucoma patients virtually always have thin corneas!
Ultrasonic Corneal Pachymetry
Measurement of corneal thickness is not a routinely performed test in a general vision exam. The most common test used to measure the thickness of the cornea is by ultrasonic technology (corneal pachymetry). Topical anesthetic drops are instilled on the cornea of the eye. A probe is then touched to the cornea and the reading is completed. The accuracy and reproducibility are somewhat difficult to duplicate since the corneal thickness varies and increases toward the periphery. Additionally, the probe must be perpendicular to the corneal surface for maximum accuracy.
Because corneal thickness is such an important test it should be performed at least once on everyone over the age of 40 or those with other glaucoma risk factors so your eye doctor is able to accurately assess the true intraocular pressure of your eye.
Corneal Ultrasonic
Pachymeter used to
measure corneal thickness
