Prism lenses are commonly prescribed for diplopia and other binocular vision conditions. Another interesting application of prism lenses is to improve peripheral visual field loss in patients with advanced glaucoma. This treatment has the potential to enhance patients’ lives significantly.
Glaucoma therapies primarily focus on slowing the progression of the disease. However, there are emotional and functional aspects of vision loss in glaucoma that may be overlooked by therapies.
For example, patients with glaucoma are more likely to experience anxiety or depression than those without glaucoma. Additionally, quality of life ratings are lower in patients with visual impairments, which may be related to issues like driving limitations or fear of falling.
Research from Dr. Eli Peli’s team at the Schepens Eye Research Institute at Harvard Medical School indicates that patients with peripheral field loss do not compensate for this loss by scanning across a wider area of their environment than normally sighted people. This lack of compensation creates mobility issues, such as bumping into other pedestrians while walking.
The study found that a patient with peripheral field loss is most likely to collide with other pedestrians if the pedestrian is located at a 45-degree angle from the patient’s walking path. They determined from this data that high-power prisms could be used to expand the patient’s visual field and create “islands of vision” at 45-degree eccentricities.
Dr. Peli’s lens design involves placing high-power Fresnel prism segments on the upper and lower periphery of the lens. His design leaves the central portion of the lens clear for distance viewing and avoids central double vision. This lens expands the binocular visual field rather than simply shifting it, as binocular sector prisms do for patients with hemianopic field loss. Peli found that lenses with peripheral Fresnel prisms of at least 35 prism diopters provided a field expansion of about 20 degrees.
He also devised an oblique design in which the base of both Fresnel prism segments are tilted towards the horizontal meridian. This orientation moves the field expansion area vertically and centrally to reduce the central gap (without moving the prism segments more centrally). The oblique peripheral prism has been shown to improve the efficacy of driving in randomized trials.
These prisms present a promising, long-lasting solution for glaucoma patients and others who have suffered significant visual field loss. Potential benefits include regained independence, improved mobility, positive emotional impact, and better overall quality of life.
R&D Optical thrives on helping you help your patients. We can manufacture specialty lenses that your patients may not be able to find elsewhere, including lenses with peripheral prism segments. We also customize lens tints and treatments to alleviate glare and light sensitivity for your glaucoma patients. To find out more about our products, please visit our website RandDOptical.com or call us at 513-273-4034. For more tips and our latest updates, follow us on Facebook, Twitter, Pinterest, Instagram or LinkedIn!
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