SIGNS AND SYMPTOMS
Many patients with RP also experience photopsiae as the disorder progresses; typically they report small flashes of light or a twinkling, shimmering sensation in the midperipheral or peripheral field. These are believed to represent aberrant electrical impulses from the degenerating retina.
Central visual acuity is generally not affected until the very late stages of RP, although variants have been encountered that cause devastating macular compromise early in the disease course (e.g., X-linked recessive RP). Color vision is typically remains intact as long as visual acuity is better than 20/40.
Attenuation of the retinal arterioles is the earliest observable sign in RP. Retinal pigmentary changes occur in the form of fine mottling or granularity with surrounding areas of atrophy. Later, stellate pigment hyperplasia may be noted at perivascular locations in the midperipheral retina. These hyperplastic formations are often referred to as "bone spicules."
As the disorder progresses, general atrophy of the RPE and choriocapillaris ensues, exposing the larger choroidal vessels. The optic nerve head is often normal in early RP, but may demonstrate a waxy yellow or pale appearance later. RP has a strong correlation with acquired optic disc drusen. The macula, like the optic nerve, is usually unaffected in the early stages, but in some forms of RP may demonstrate preretinal gliosis ("cellophane maculopathy"), cystoid macular edema or focal RPE defects. Additional findings in RP include pigment cells in the vitreous ("tobacco dust sign"), posterior vitreous detachment and posterior subcapsular cataracts.
Most patients with retinitis pigmentosa are myopic, and many have
keratoconus as well. Electrodiagnostic testing in RP shows a significantly diminished
scotopic ERG as well as an abnormal EOG and dark adaptometry.
There are many forms of retinitis pigmentosa, and while most present
with similar findings and outcome, some presentations are atypical. RP may be classified
on the basis of inheritance pattern (autosomal dominant, autosomal recessive, X-linked,
simplex, multiplex), age of onset (congenital, childhood onset, juvenile onset, adult
onset), predominant photoreceptor involvement (rod-cone, cone-rod), or location of retinal
involvement (central, pericentral, sectoral, peripheral).
Always obtain visual fields and electrodiagnostic testing to confirm the diagnosis of RP; order serology if the diagnosis is unclear or other disorders are suspected.
Most experts recommend a pedigree analysis of patients once RP has been diagnosed. This is critical to determine the exact inheritance pattern of the patient's condition. Individuals should know the risk for their progeny or other family members developing the disease.
Recommend genetic counseling to help the patient deal with
these issues. Implement low-vision services as the disorder begins to affect visual
function. Field-expansion devices, infrared blocking sun lenses and contrast enhancing
filters may be helpful. Periodic optometric follow-up is also important. Perform visual
fields several times a year, and evaluate for cataract or macular edema at least annually.
Other reports in this section
Eyelids & Eyelashes | Conjunctiva & Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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