Variability of vertical cup to disc ratio measurement and the effects of glaucoma 5-year risk estimation in untreated ocular hypertensive eyes.

Abstract

To compare the vertical cup to disc ratio (VCDR) measurements obtained with optical coherence tomography (OCT), Heidelberg retina tomography (HRT) and stereophotography of the optic nerve head (ONH) in patients with ocular hypertension (OHT), and their corresponding estimated 5-year risk for development of glaucoma. ONH images of patients with OHT were taken by fundus camera (stereoscopic images), OCT and HRT. Optic disc stereophotographs were evaluated with a stereo-viewer by two glaucoma specialists (SP1 and SP2) and the VCDR was measured with the ImageJ software. VCDR measurements obtained with stereophotography, OCT and HRT were used to calculate the estimated 5-year risk. One hundred and forty eyes of 75 patients with OHT were included. The VCDR values measured by OCT, HRT, SP1 and SP2 were 0.60±0.14, 0.53±0.23, 0.44±0.13 and 0.49±0.10, respectively. The corresponding 5-year risk for development of glaucoma was 19.54%±16.60%, 18.13%±16.96%, 15.64%±14.35% and 16.70%±14.49%, respectively. Different degrees of proportional biases were observed in VCDR measurements obtained with stereophotography, OCT and HRT. The maximum difference of VCDR measurement was 0.64, while the maximum difference of the corresponding 5-year risk was 24.02%. The disagreement in VCDR measured by OCT, HRT and stereophotography in untreated OHT eyes extends to their 5-year risk estimation of glaucoma development.