In particular, the cost of optic nerve photography is substantially lower than the newer techniques. Īlthough recent advances in computerized analysis of the ONH have assisted the practitioner, these methods have not completely supplanted photographic analysis of the optic nerve. The resulting photographs can then be viewed with an inexpensive stereoscope viewer or similar device. A common technique is to take two photographs of the same nerve shifting the angle of the camera slightly between exposures. Stereo disc photography can be achieved utilizing several methods. Stereo disc photography has greater utility in determining size and shape of the neuroretinal rim and the depth of the cup than two-dimensional photography. Stereo disc photography and red-free nerve fiber layer photography are additional techniques to enhance the evaluation of the disc photograph. In addition, photographs allow for analysis of changes in the anatomy of the optic nerve over time. It is not uncommon for practitioners to identify feature such as disc hemorrhages on subsequent evaluation of a photograph. Thus, photography allows the practitioner to evaluate fine details of the anatomy not easily seen on examination. Extended examination is difficult for patients and practitioners. Single images can be used to closely evaluate the structural relationships within the nerve. Photographic documentation of the optic nerve serves multiple purposes. The standard optic nerve photographic technique of 35mm film and now digital photography has been used extensively since the 1960’s. Fundus photography was developed in the 1920’s. The optic nerve appearance often provides evidence of the presence and progression of glaucoma.Ĭlinical Signs of Glaucomatous Optic Neuropathyįundus photography has been the primary method of documenting the optic nerve until the advent of computerized imaging techniques. However there appear to be a number of different pathophysiologic mechanisms by which ganglion cell loss may occur. Elevated intraocular pressure is the greatest risk factor for development of ganglion cell loss. The decrease in vision from glaucoma is related to the loss of retinal ganglion cells. The retinal ganglion cells coursing into the optic nerve are responsible for the appearance of the neuroretinal rim. Pallor of the neuroretinal rim indicates previous insufficiency of the vascular supply of the optic nerve which is often unrelated to glaucoma. As the rim thins from ganglion cell loss, the cup becomes larger and often deeper exposing the lamina with increased pallor of the cup. The pallor of glaucomatous optic nerves relates to the increased visibility of the lamina cribosa as compared to the neuroretinal rim (containing the ganglion cells). The term pallor is likely to be misinterpreted to mean generalized pallor of the optic nerve. Optic Nerve in the Detection of GlaucomaĬhanges in the optic nerve in glaucoma are classically considered to be cupping and pallor of the disc. There are significant variations in optic nerve structural parameters in homogenous populations as well as with refractive error and race. The optic nerve size changes in early life and is likely stable after age 10. The optic nerve (optic disc, optic disk, optic nerve head ) area is approximately 2.1-2.8 mm 2 in whites who are not highly myopic depending on the measurement method utilized. This article will discuss information on evaluation of the intra-bulbar structure of the optic nerve as it relates to glaucoma, with particular emphasis on three imaging devices, confocal scanning laser ophthalmoscopy, optical coherence tomography, and scanning laser polarimetry. Recently, techniques utilizing sophisticated laser scanning with digital image processing have been used to assist clinical evaluation of the optic nerve and the retinal nerve fiber layer (RNFL). Direct observation with notation progressed to accurate photographic techniques. Although there have been variations in the definition of glaucoma over time, increased attention to the structure and appearance of the optic nerve has been a hallmark in understanding glaucoma. Since the mid-19th century, it has been recognized that changes in the optic nerve appearance correlate with vision and visual field loss in glaucoma. 2.7.1 General Concepts of OCT Analysis for Glaucoma.2.5 Confocal Scanning Laser Ophthalmoscopy.2.4 Computed Analysis of the Optic Nerve Head and Retinal Nerve Fiber Layer.2.3.2 Disadvantages of Optic Disc Photography.2.3.1 Advantages of Optic Disc Photography.2.1 Optic Nerve in the Detection of Glaucoma.
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