A comparison of stereoscopic and monoscopic evaluation of optic disc topography using a digital optic disc stereo camera

Abstract

Aims-To compare stereophotographic and monophotographic optic disc assessments made using a digital optic disc stereo camera. Methods-Stereo digital optic disc photographs of 150 selected patients who had presented to a glaucoma clinic were assessed by two masked observers on separate occasions using (1) the stereophotographs and a stereoviewer, (2) a single image from the same stereopair. Results were analysed for both right and left eyes separately. 95% tolerance limits for change (TC) and intraclass correlation coeYcients (ICC) were calculated and a multivariate analysis using a general linear model for repeated measures was performed. Conclusions-This study using a digital stereo camera indicates that there may be little benefit of stereoscopic imaging over monoscopic imaging despite demonstrating small but inconsistent diVerences between both observers and methods. (Br J Ophthalmol 2001;85:1347-1351 The detection of early or progressive glaucomatous optic disc changes is essential in the optimum management of glaucoma patients. Despite the plethora of new technologies the accepted "gold standard" for optic disc assessment remains stereoscopic optic disc photography. Results-1-4 However, measurements rely on a subjective evaluation by the clinician and are subject to poor interobserver agreement. 5-10The Discam optic disc camera (Marcher Enterprises Ltd, Hereford) obtains digital monochromatic sequential stereophotographic images of the optic disc and the allied software allows the computation of a number of optic disc parameters. In a previous study, the intraobserver and interobserver repeatability of optic disc measurements was shown to compare favourably with ophthalmoscopic and stereophotographic methods of assessment of the optic disc.11 However, stereoscopic versus monoscopic assessments of the images were not performed.The aims of this study were to determine whether there were significant diVerences in intraobserver and interobserver repeatability of the computed optic disc parameters using monophotographic and stereophotographic images to determine the margins of the optic disc and optic cup. Materials and methodsStereophotographic digital images of patients presenting to a glaucoma clinic were acquired by two experienced operators following pharmacological mydriasis. The detailed method has been previously described. 11 The quality of the images were assessed by observer 2 (MC), on the basis of contrast, clarity, stereoscopic appearance, illumination, and excessive movement between the image pair. As this study did not aim to determine the clinical usefulness of the Discam, but purely to compare two methods of assessment, only high quality images were used for analysis in order to maximise any diVerences. Exclusion criteria were poor illumination of the disc, poor quality image, lens opacity, poor stereoimage (large shift on the screen between images of stereo pair) and optic discs of anomalous configuration (those which were tilted, colobomatous, or myopic). A total of 201 images (from a ...

Optic Disc Progression in Glaucoma: Comparison of Confocal Scanning Laser Tomography to Optic Disc Photographs in a Prospective Study

“…Although studies comparing observer agreements judging progression using monoscopic and stereoscopic photographs have not been published, observer agreement rates in a onetime assessment of glaucomatous discs was reported to be higher with stereo photographs in one study 35 but not in another. 36 A recent study of agreement among three expert observers using stereo disc photographs 37 yielded generally poorer agreement than that reported in this study. However, it is possible that had stereo disc photographs been available, our observer agreement, hit rates, and specificities would have been higher.…”

Digital imaging of the optic nerve head: monoscopic and stereoscopic analysis

“…Previous reports of digital stereoscopic disc analysis 14 did not describe the use of stereoscopic cursors. With the Discam system a single cursor is used, which is projected on one of the stereoscopic images 13 and cannot be adjusted to lie within the correct measurement plane. It is possible that the presentation of the cursor to a single eye may introduce effects such as rivalry, 26 which could complicate further accurate stereoscopic measurements.…”

“…Finally, there is little evidence to show that stereoscopic imaging per se provides sufficient additional clinical information to justify its use when compared with the monoscopic evaluation of optic nerve head images. This issue was highlighted recently by a study analysing sequential stereoscopic images, which suggests that stereoscopic imaging conveys little additional benefit 13 for the assessment of the optic disc.…”

Comparison of Heidelberg retina tomography, optical coherence tomography and Humphrey visual field in early glaucoma diagnosis

“…The outcomes above have good coherence with the correlation analysis of disc parameters and W/W-MD, but they do not exhibit greater correlation, and this phenomenon has been noted previously. 23 One possible reason may be that the perimetry test has a 'learning curve', which means that sensitivity variation range for the first test may be higher than the normal value and could be a confounding factor that could affect the PSD result, whereas a single point variation of MD is less sensitive than PSD, meaning that MD is less affected.…”