The importance of central corneal thickness measurements and decision making in general ophthalmology clinics: a masked observational study

BACKGROUND: To assess the impact of knowing central corneal thickness (CCT) on glaucoma management in a United Kingdom district general hospital. METHODS: A masked observational non-interventional study included 304 eyes of 152 consecutive glaucoma cases attending general clinic. CCT was measured using a hand-held pachymeter. IOP, as measured by the Goldmann applanation tonometer (GAT), was adjusted for CCT using a normogram. Two identical study sheets were retrospectively constructed from each subject's case notes: one included the CCT and adjusted IOP information, the other excluded. Study sheets were randomly presented to a single masked observer to decide glaucoma management. The difference in management decision was noted. RESULTS: The mean ± standard deviation CCT was 561.5 ± 35.7 μm, 538.9 ± 41.4 μm, 538.3 ± 40.3 μm for ocular hypertension (OHT), primary open angle glaucoma (POAG) and normal pressure glaucoma (NPG) subjects respectively. IOP adjustment was greater than ±2 mmHg in 33.9%(103/304) of eyes. CCT and adjusted IOP information led to different treatment option in 37%(55/152). Of the most important changes 20.4%(31/152) cases would have been commenced on additional IOP-lowering medication, 2.0%(3/152) would have been counselled for trabeculectomy surgery and 3.3%(5/152) of the cohort would have been observed rather than treated. CONCLUSION: CCT and adjusted IOP measurement can influence glaucoma management in a clinical context. It helps attribute risk and hence aids patient management decisions.