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The Peli Lens is a mobility aid for people with homonymous hemianopia. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in 1999. It expands the visual field by 20 degrees.
Prisms or "field expanders" that bend light have been prescribed for decades in patients with hemianopsia. Higher power Fresnel ("stick-on") prisms are commonly employed because they are thin and lightweight, and can be cut and placed in different positions on a spectacle lens.
Homonymous hemianopsia. A homonymous hemianopsia is the loss of half of the visual field on the same side in both eyes. The visual images that we see to the right side travel from both eyes to the left side of the brain, while the visual images we see to the left side in each eye travel to the right side of the brain.
Binasal hemianopsia is the medical description of a type of partial blindness where vision is missing in the inner half of both the right and left visual field. It is associated with certain lesions of the eye and of the central nervous system, such as congenital hydrocephalus .
Lesions of right temporal lobe (meyer's Loop) of the optic radiation on one side produces a loss of the upper, outer quadrant of vision on the contralateral side, known as homonymous superior quadrantanopia or superior quadrantic hemianopia. This is also known as pie in the sky disorder.
Lesions in the optic tract correspond to visual field loss on the left or right half of the vertical midline, also known as homonymous hemianopsia. A lesion in the left optic tract will cause right-sided homonymous hemianopsia, while a lesion in the right optic tract will cause left-sided homonymous hemianopsia.
Macular sparing is visual field loss that preserves vision in the center of the visual field, otherwise known as the macula. It appears in people with damage to one hemisphere of their visual cortex, and occurs simultaneously with bilateral homonymous hemianopia or homonymous quadrantanopia.
In contrast, spectacles with prisms of equal power for both eyes, called yoked prisms (also: conjugate prisms, ambient lenses or performance glasses) shift the visual field of both eyes to the same extent.
This page was last edited on 31 December 2006, at 03:45 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike License 4.0; additional terms may apply.
The most common type of visual field impairment due to AVMs is homonymous hemianopia, which is usually unilateral. Central nervous system (CNS) symptoms of Bonnet–Dechaume–Blanc syndrome are highly dependent on the locations and sizes of cerebral AVMs. The most common CNS feature is an intracranial hemangioma in the midbrain.