Tip of the Month
Publishing date: March 2009
The Science behind the Tip
Central corneal thickness (CCT) varies among individuals, the average CCT in the general population being approximately 540 µm. Studies using optical pachymetry have reported slightly lower CCT values (530 ± 29 µm, average ± SD) compared to ultrasonic studies (544 ± 34 µm)(1).
Among the most striking of the Ocular Hypertension Treatment Study's (OHTS) findings was that CCT is a powerful predictor of primary open-angle glaucoma risk(2). It appeared that CCT bears an inverse relation with the risk of developing glaucoma damage, i.e. patients with thinner corneas are at higher risk. This observation in ocular hypertensive patients was confirmed in another study(3). In addition, EMGT has since provided support of a role for CCT in the progression of glaucoma damage in patients with early glaucoma(4).
In another study CCT proved to be a powerful clinical factor in determining glaucoma severity at the initial eye examination(5). Whether a thin cornea is the expression of thin ocular tissues and a weak lamina cribrosa increasing susceptibility to glaucomatous damage, is still under investigation. The possibility can at this time not be excluded that the increased risk is partly or even entirely due to incorrect tonometric readings in eyes with corneas thinner than 520 µm.
Contributor: Ann Hoste, Antwerp
Co-editors: John Thygesen and Ann Hoste
Peer reviewers: Roger Hitchings and Anders Heijl
1. Doughty MJ, Zaman ML. Human corneal thickness and its impact on intraocular pressure measures: A review
and meta-analysis approach. Surv Ophthalmol. 2000;44:367-408.
2. Gordon MO, Beiser JA, Brandt JD, et al. Ocular Hypertension Treatment Study: baseline factors that predict
the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120:714-20.
3. Medeiros FA, Sample PA, Weinreb RN. Corneal thickness measurements and visual function abnormalities in
ocular hypertensive patients. Am J Ophthalmol. 2003;135:131-7.
4. Leske MC, Heijl A, Hyman L, et al. Predictors of long-term progression in the early manifest glaucoma trial.
5. Herndon LW, Weizer JS, Stinnett SS. Central corneal thickness as a risk factor for advanced glaucoma
damage. Arch Ophthalmol. 2004;122:17-21.
Tip Reviewer: Roger Hitchings
Tip Editors: Ann Hoste, John Salmon and John Thygesen