New technologies for diagnosing and monitoring glaucomatous optic neuropathy

Background. Recently, instruments have been developed to provide real-time, quantitative measurements of the optic disc and retinal nerve fiber layer (RNFL) for use in glaucoma management. Our objective is to (1) provide an o verview of two of these instruments, the confocal scanning laser ophthalmos cope (Heidelberg Retina Tomograph, HRT) and scanning laser polarimeter (Ner ve Fiber Analyzer, NFA) and (2) compare measurements obtained with these in struments to clinical features used in the diagnosis of glaucoma. Methods. Twenty glaucoma patients, 4 normal subjects and 20 glaucoma subjects were i ncluded. All subjects had images obtained with the HRT and NFA, and RNFL an d optic disc photography completed within 5 weeks of each other. The HRT re sults were compared with qualitative evaluation of stereophotographs of the optic disc, and NFA results were compared against a semi-quantitative RNFL photograph severity score. Results. Twenty-five (57%) subjects had thinnin g of the neuroretinal rim identified by evaluation of stereoscopic optic di sc photographs. Despite overlap, HRT measurements of rim volume, rim area, and rim/disc ratio were significantly smaller in eyes with evidence of rim thinning than in eyes with no evidence of rim thinning. Moderate to severe RNFL damage was detected by evaluation of photographs in 25 (57%) of subjec ts. NFA RNFL thickness measures were smaller in eyes with moderate to sever e RNFL damage than in relatively healthy eyes. Conclusions. Previous studie s have documented the reproducibility of these instruments and suggested an alytic techniques for improving their ability to differentiate between norm al and glaucoma eyes. Our results indicate that despite overlap in values, these instruments provide measurements that reflect clinically relevant fea tures of the optic disc and RNFL. Whether these technologies can improve ou r ability to detect glaucomatous progression over time needs to be determin ed with well-designed longitudinal studies and comparison with established diagnostic techniques for evaluating glaucomatous optic neuropathy.