Stereopsis and Teleophthalmology

3.1Introduction

Stereopsis is the ability of the brain to fuse two different images received from each eye and provide a three-dimensional image as well as a sense of depth. This sense of depth provides additional information that might not otherwise be available to the viewer. Stereopsis is, therefore, an important clinical tool in ophthalmology. The use of stereo vision in ophthalmologic clinical practice is crucial for the detection and diagnosis of three-dimensional pathology such as optic nerve cupping, neovascularization, agerelated macular degeneration (AMD) and diabetic macular oedema. It is also important when performing surgery with a binocular microscope, as is most commonly used in ophthalmology.

The use of stereopsis in ophthalmic photography is widespread, as this reproduces most accurately a clinical examination by slit lamp biomicroscopy or indirect ophthalmoscopy. Anterior segment, angle and fundus photography, as well

as ßuorescein angiography [13], all utilize stereoscopic photography.

In teleophthalmology, clinical evaluations are completed remotely and rely on digital ocular photography in most cases. In order to replicate the clinical examination in a telehealth setting, the incorporation of stereophotography is vital for the detection of three-dimensional pathologies [18]. The technique of capturing threedimensional photographs does not come without inherent difÞculties, thereby leading some to question its necessity [17]. As a result, several groups have developed monoscopic [5, 14, 28, 30] instead of stereoscopic [6, 23, 26] retinal teleophthalmology systems.

This chapter reviews a brief history of stereopsis, the use of stereo imaging in ophthalmology, stereographic photography and technology, and its uses in teleophthalmology.

B.K. Wong, M.D.

Department of Ophthalmology, Loma Linda University

Health Care, 11370 Anderson, Suite 1800,

Loma Linda, California 92354, USA

C.J. Rudnisky, M.D., MPH, FRCSC ( ) ¥ M.T.S. Tennant, M.D., FRCSC Department of Ophthalmology,

Royal Alexandra Hospital, University of Alberta, Rm. 2316, 10240 Kingsway Avenue, T5H 3V9, Edmonton, AB, Canada

e-mail: chris@rudnisky.ca

3.2History of Stereopsis and Stereopsis in Ophthalmology

Stereoscopic vision and the concept of stereopsis were Þrst described in 280 B.C. by Euclid [25]. The knowledge of retinal disparities allowed an inventor by the name of Charles Wheatstone to create the Þrst stereoscope in the 1830s. His invention fused two dissimilar pictures to produce a single image with depth [32]. In 1850, an improved stereoscope was made by David Brewster which viewed photographs in a darkened box with the use of lenses; the advent of fundus photography soon followed in 1854.