Tip of the Month
Publishing date: May 2010
Tip Editors: Ann Hoste, John Salmon and John Thygesen
Tip reviewer: Roger Hitchings
The Science behind the Tip
The measurement of central corneal thickness (CCT) has emerged as an important parameter to determine in all patients with ocular hypertension and glaucoma.
· Evidence suggests that CCT is an independent risk factor for glaucoma(1). Anatomical correlation between CCT and individual ocular structural differences (lamina cribrosa integrity and scleral rigidity) may explain a biological susceptibility to glaucoma.
· True intraocular pressure is not predictable with linear correction formulas for CCT.
· CCT is a significant predictive factor for conversion from ocular hypertension to glaucoma and for glaucoma progression(1).
· Patients with normal tension glaucoma and black ancestory have thinner CCT than normal(2).
· Glaucoma patients with thin CCT are more likely to be diagnosed at an advanced stage of disease.
· Myopic excimer laser refractive surgery reduces CCT and anterior corneal curvature and results in post-operative underestimation of Goldman IOP.
Contributor: A L Mead, J F Salmon - Oxford Eye Hospital, Oxford, UK
1. Kass MA, Heuer DK, Higginbottom EJ et al. The Ocular Hypertension Treatment Study: a randomised trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002; 120:701-713
2. Copt RP, Thomas R, Mermoud A. Corneal thickness in ocular hypertension, primary open-angle glaucoma, and normal tension glaucoma. Arch Ophthalmol 1999; 117:14-6