REPRODUCIBILITY OF TOPOMETRIC DATA WITH A SCANNING LASER OPHTHALMOSCOPE IN RABBITS

The Heidelberg Retina Tomograph is a confocal scanning laser ophthalmo scope which obtains three-dimensional images of the optic nerve head a nd the retina in the human eye. Because of its potential investigative uses in experimental animal models of glaucoma, we examined its varia bility with optic nerve head measurements in the rabbit eye. Three top ographic images, recorded on different days, were acquired from the ri ght eye of 5 New Zealand white rabbits over 3 weeks. To estimate the l owest possible variability, a second series of three images was record ed in a single setting without displacement of the rabbits. The averag e coefficient of variability (standard deviation/mean) for the estimat e of the optic nerve head cup volume (volume below surface) was 11.1% in the independent series and was decreased to 3.0% in the sequentiall y recorded series without displacement of the rabbits (P<0.001). These values indicate a comparable variability for the estimate of the opti c nerve head cup volume in the rabbit compared with those reported for the human eye. This variability is considerably decreased by maximall y standardizing the image acquisition position, suggesting that variab ility largely depends on the alignment between the subject and the las er-scanner.