Best Disease Workup

Updated: Oct 10, 2016
  • Author: Michael Altaweel, MD, FRCSC; Chief Editor: Hampton Roy, Sr, MD  more...
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Workup

Laboratory Studies

Genetic testing: This disorder has been mapped to a genetic defect in chromosome 11 (region q12-q13.1). [16, 17, 18, 19] A mutation in Best1 is more probable when a vitelliform lesion is accompanied by a reduced Arden ratio on EOG testing. [20] Although most individuals with Best disease have an autosomal dominant defect, there are individuals with autosomal recessive inheritance. [10]

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Imaging Studies

Fluorescein angiogram reveals blockage of choroidal fluorescence by the vitelliform lesion. The angiogram is otherwise normal at this stage. In the atrophic stage, a transmission defect is noted; this is shown in the image below. If a choroidal neovascular membrane develops, then a corresponding area of hyperfluorescence with leakage will be found in fluorescein or indocyanine green angiography. [6, 21]

The fluorescein angiogram of the latter lesion rev The fluorescein angiogram of the latter lesion reveals a transmission defect consistent with atrophic changes in the retinal pigment epithelium. This appearance also can be found in the later stages of Best disease.

Fundus photography is useful for documentation and follow-up of fundus lesions.

Spectral domain Optical coherence tomography (SD OCT) demonstrates abnormality in the region between the RPE and the inner segment/outer segment line visualized on high resolution studies. Later stages involving atrophy are identified on the OCT as well. Cystoid macular edema and choroidal neovascularization can be identified on OCT. [22, 23] See the image below.

Spectral domain optical coherence tomography demon Spectral domain optical coherence tomography demonstrates subretinal lesion with adjacent cystoid macular edema.

Adaptive optics demonstrates disruption of photoreceptor integrity with some retention of function, [24] consistent with the retention of visual function found through the earlier stages of Best disease.

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Other Tests

Electro-oculogram

The EOG, which reflects RPE function, is the most diagnostic test for evaluating vitelliform macular dystrophy. In the majority of such individuals, a severe decrease occurs in light response, reflected by an Arden (light-peak/dark-trough) ratio of 1.1-1.5. (The normal Arden ratio is 1.8.) Carriers will also have an abnormal EOG result. [25] No correlation exists between EOG result and disease stage, visual acuity, or patient age. EOG results are usually symmetric for both eyes. [26]

The EOG is very useful for distinguishing this diagnosis from its differential. The EOG result is usually normal in adult foveomacular dystrophy.

Electroretinogram

The full-field electroretinogram (ERG) result is normal in this condition. A focal ERG or multifocal ERG, concentrating on macular function, reveals abnormal function corresponding to the area of anatomical disruption. [27]

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Histologic Findings

This disease primarily affects the RPE. Lipofuscin accumulates within RPE cells and in the sub-RPE space. This material stains PAS-positive. The RPE can degenerate, and macrophages containing PAS-positive material have been found to migrate into the outer retina. The choriocapillaris is normal. Choroidal neovascularization has been demonstrated. [28, 4]

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Staging

See Physical.

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