IDENTIFICATION OF EARLY GLAUCOMA CASES WITH THE SCANNING LASER OPHTHALMOSCOPE

Purpose: This study aimed to define the confocal laser scanning ophtha lmoscope (Heidelberg Retina Tomograph [HRT]) parameters that best sepa rate patients with early glaucoma from normal subjects. Study Design: A cross-sectional study. Participants: A total of 80 normal subjects a nd 51 patients with early glaucoma participated (average visual field mean deviation = -3.6 dB), Intervention: Imaging of the optic nerve he ad with the HRT and analysis using software version 1.11 were performe d. Main Outcome Measures: The relation between neuroretinal rim area a nd optic disc area, and cup-disc area ratio and optic disc area, was d efined by linear regression of data derived from the normal subjects. The normal ranges for these two parameters were defined by the 99% pre diction intervals of the linear regression between the parameter and o ptic disc area, for the whole disc, and for each of the predefined seg ments. Normal subjects and patients were labeled as abnormal if the pa rameter for either the whole disc or any of the predefined segments wa s outside the normal range, The sensitivity and specificity values of the method were calculated. Results: The highest specificity (96.3%) a nd sensitivity (84.3%) values to separate normal subjects and those pa tients with early glaucoma were obtained using the 99% prediction inte rval from the linear regression between the optic disc area and the lo g of the neuroretinal rim area. Similar specificity (97.5%) and lower sensitivity (74.5%) values were obtained with the 99% prediction inter val derived from regression between the disc area and cup-disc area ra tios. Poor separation between groups was obtained with the other param eters. Conclusions: The HRT, using the technique of linear regression to account for the relationship between optic disc size and rim area o r cup-disc area ratio, provides good separation between control subjec ts and patients with early glaucoma in this population.