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Structural studies in glaucoma
Last reviewed: 06.07.2025
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Glaucoma parameters are measured by assessing the optic disc excavation, SNV defects, and possibly their thickness ratio at the macula. These parameters are reliable indicators of glaucoma and its progression.
The development of noninvasive objective methods for examining the retinal structures most susceptible to glaucomatous damage facilitates the diagnosis and dynamic monitoring of progressive changes in glaucoma. Among the simplest technologies for assessing structural glaucomatous damage are stereoscopic photography and photography of the SNV. Currently, new computerized visualization analytical programs have been developed for more objective and quantitative measurements of the SNV of the retina and optic disc.
[ Photography
Stereoscopic optic disc photography is one of the most widely used imaging techniques. SNV photography is more complex and is used less frequently than optic disc photography. It allows for a broader assessment of the SNV during patient examination. Specific retinal changes in glaucoma include focal and diffuse thinning of the SNV.
How Stereoscopic Photography Is Conducted
Stereoscopic images are obtained using continuous (sequential) or synchronous photography techniques. In continuous stereoscopic photography, two sequential images are captured by manually moving the camera joystick. In synchronous stereoscopic photography, instantaneous stereoscopic images are captured with one-time processing and the production of a composite image from two photographs or two 35 mm slides, depending on the system used.
When is stereoscopic photography used?
Stereoscopic photography of the optic disc should be used, if available, every 1 or 2 years to evaluate patients with suspected glaucoma and in glaucoma to monitor disease progression.
Restrictions
The method of stereoscopic photography of the optic nerve head lacks an objective system for interpreting the state of the optic nerve.
How to photograph the nerve fiber layer
The SNV consists of ganglion cell axons, neuroglia, and astrocytes. When collected together, ganglion cell axons project toward the optic nerve. The SNV is best visualized under red, blue, or green light. Blue and green wavelengths are well absorbed by the retinal pigment epithelium and choroid, and axon bundles reflect light and appear as silvery lines.
When is nerve fiber layer photography used?
The SNV study is used to differentiate suspected glaucoma from damage developing in true glaucoma. SNV defects precede the appearance of changes in the optic disc and visual field. Thus, when the SNV state is correlated with the visual field, subjective signs detected by automatic perimetry are objectively confirmed.
Restrictions
Factors that limit the ability to evaluate SNF photographs include media opacities such as cataracts, poorly focused photographs, and poor contrast due to insufficient fundus pigmentation.