Adult vitelliform dystrophy (AVD), also known as adult-onset foveomacular vitelliform dystrophy, is an inherited eye condition affecting the macula. The macula is the central part of the retina responsible for sharp, detailed vision. AVD involves the accumulation of lipofuscin, a waste material, underneath the fovea. This material disrupts the function of light-sensing cells, leading to a decline in central vision.
Understanding the Symptoms and Progression
Individuals with adult vitelliform dystrophy often experience blurred vision, distorted vision (metamorphopsia), and blind spots (scotomas) in their central field of view. These symptoms typically emerge in adulthood, usually between ages 40 and 60. The condition can affect one or both eyes, though severity may differ.
A distinguishing characteristic of AVD is a yellowish, round or oval lesion in the macula, often described as resembling an “egg yolk.” This lesion is caused by the buildup of lipofuscin-like material between the photoreceptors and the retinal pigment epithelium (RPE). As the condition progresses, this material can change, potentially fragmenting or being reabsorbed, leading to retinal atrophy and, in some cases, mild scarring.
Vision loss in AVD tends to be gradual. While central vision may be affected, peripheral vision and night vision are generally preserved. The size of the vitelliform lesions can influence vision, with larger lesions often linked to decreased visual acuity.
Genetic Basis and Causes
Adult vitelliform dystrophy is primarily a genetic disorder, often inherited in an autosomal dominant pattern. This means a person only needs to inherit one copy of the mutated gene from a parent to develop the condition. However, cases can occur without a known family history.
Mutations in the PRPH2 gene (also known as the RDS gene) are frequently associated with AVD. This gene provides instructions for making peripherin, a protein involved in the structure and function of photoreceptor outer segments, the light-sensitive parts of the retina. When mutated, it leads to an abnormal accumulation of lipofuscin, a waste product of photoreceptor metabolism, beneath the retina. This buildup disrupts the interaction between photoreceptors and the retinal pigment epithelium, contributing to the characteristic retinal changes. Other genes, such as BEST1 and IMPG1, have also been linked to some cases of adult-onset foveomacular dystrophy.
How Adult Vitelliform Dystrophy is Diagnosed
Diagnosing adult vitelliform dystrophy involves a comprehensive eye examination and specialized ophthalmic tests. Visual acuity is checked during a general eye exam. An Amsler grid test may detect distorted vision or blind spots, common symptoms of macular conditions.
Imaging techniques are important for visualizing retinal changes. These include:
- Fundus photography, captures images of the back of the eye.
- Optical coherence tomography (OCT), provides cross-sectional views of retinal layers, identifying the vitelliform lesion and assessing its location and size.
- Fundus autofluorescence (FAF) imaging, reveals lipofuscin accumulation.
- Fluorescein angiography (FA), involves injecting a dye to highlight retinal blood vessels, and may be performed if there is suspicion of complications like abnormal blood vessel growth.
Electroretinography (ERG) may assess overall retinal function to differentiate AVD from other retinal dystrophies. Genetic testing is often performed to confirm the diagnosis and identify the specific gene mutation responsible for the condition, to understand the inheritance pattern and for counseling family members.
Current Management and Treatment Approaches
Currently, there is no cure for adult vitelliform dystrophy. Management focuses on monitoring vision and addressing complications. Regular eye examinations track the condition’s progression and detect changes.
For individuals experiencing reduced vision, low vision aids can be beneficial. These aids include magnifiers, telescopic lenses, and specialized software to enlarge text or images, improving reading and other daily tasks. Learning strategies, such as using brighter lighting or increasing contrast, can help adapt to vision loss and maintain independence.
One potential complication of AVD is choroidal neovascularization (CNV), involving the growth of abnormal blood vessels under the macula. If CNV occurs, treatments similar to those for wet age-related macular degeneration may be employed. These often include anti-VEGF injections, medications administered directly into the eye to inhibit new, leaky blood vessel growth. Research into the underlying mechanisms of AVD continues to advance, offering hope for future therapeutic developments.