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Adult vitelliform Macular Degeneration (AVMD) is an adult onset form of Bests disease.
What is Adult vitelliform Macular Degeneration (AVMD)?听
AVMD is a听dominantly inherited听bestrophinopathy听which affects the听Retinal Pigment Epithelium (RPE).听It is very similar to听Best disease (learn more Best disease here),听so much so that many听argue听that听AVMD听is a form of听Best disease. The number of patients suffering from听AVMD is not currently known, though, it is a rarer incidence than Best disease. Typical age of onset of the condition is between 30 to 50 years old. AVMD has also been found to be caused by mutations in the PRPH2 gene, as well as the BEST1 gene.听
How does AVMD affect the eye?听听
AVMD is clinically indistinguishable from milder forms of Best disease, with the classical vitelliform 鈥榚gg-yolk鈥� lesion also usually being present. AVMD has even been said to be a less severe form of Bests,听owing to the fact that it begins later than Bests and also seems to have a much slower progression.听The 鈥榚gg-yolk鈥� lesions also appear to be much smaller.听These听smaller lesions听may not necessarily pass through the six clinical stages of听Best听disease听but the听region may听still听undergo atrophy (death of the region).听听
AVMD has a less dramatic听effect on vision,听compared to听Best听disease.听In general, older patients are diagnosed when changes in their macular region are听observed, these changes may or may not be accompanied by vision loss. Over time, central vision loss can occur, but vision tends to remain stable, however AVMD patients can have complications听associated听with the disease.听Vision has been reported to range from 6/12 to 6/60 on the听Snellen chart.听听
How is AVMD diagnosed?听
Similar to听Best disease, OCT imagery can be used to听examine听the macular region, assessing any lesions, RPE structure, lipofuscin deposits and fluid build-up.听
Autofluorescence imaging (FAF and FA)听can be used听to detect the听hyperautofluroscence听seen at earlier stages,听and听hypofluorescence听at late stage disease. EOG recordings, however, are usually normal or only slightly reduced听in AVMD patients. ERG recordings will also be normal in those suffering with AVMD.听听
Suspected cases of AVMD can be confirmed using genetic sequencing.听
Are there any complications听associated with听AVMD?听
The main complication for AVMD is choroidal neovascularization (CNV).听听This is where new and weak blood vessels,听which originate from the choroid,听make their way听through听the RPE听layer of cells. The new blood vessels can听easily rupture and break leading to fluid leakage. The听build up听of fluid can听lead听to听pigment epithelial detachment (PED). PED is another complication of听AVMD听and it occurs when excess fluid build-up causes the RPE to detach from the underlying choroid.听听
What are the treatment options for AVMD?听听
There听are听currently no medical or surgical treatment听options available for AVMD, or any of the听bestrophinopathies, however听research听is ongoing and promising.听The complications associated with AVMD can be treated, e.g.听anti-VEGF injections听used to听stop the growth of newer vessels, with the aim to preserve vision.听
Research听into treatments for AVMD is ongoing. Patients are encouraged to visit the many听charities and support groups for听bestrophinopathies.听