Basal Laminar Drusen
Basal laminar drusen/Cuticular drusen is an uncommon entity that was originally thought to be distinct from age-related macular degeneration, but is now considered to be part of a spectrum of disease that includes age-related macular degeneration. Findings include numerous small yellow drusen on examination, which are more obvious on fundus auto-fluorescence. Fluorescein angiography (FA) demonstrates punctuate areas of early staining throughout the macula, with a “stars in the sky" pattern. The development of vitelliform macular lesions, choroidal neovascularization (CNV), and geographic atrophy may cause vision loss.
Basal laminar drusen have also been referred to as diffuse drusen, cuticular drusen, and early-adult onset grouped drusen in the literature.
Basal laminar drusen are a subtype of early onset drusen. It is considered part of a spectrum that includes age-related macular degeneration
The etiology is not well understood.
Many risk factors for age-related macular degeneration are risk factors for basal laminar drusen.
Cigarette Smoking Current cigarette smoking is associated with basal laminar drusen, with an odds ratio of 2.06. This association is less strong than that between current smoking and age-related macular degeneration. A history of smoking is not associated with basal laminar drusen.
Genotype Presence of the complement factor H Y402H variant is associated with basal laminar drusen, with a statistically significant odds ratio of 2.88.
Family History In one cohort, 44% of patients with basal laminar drusen reported a family history of age-related macular degeneration.
Gender In one large case series, there was a trend toward female gender being a risk factor for basal laminar drusen, but this was not statistically significant.
Initially, basal laminar drusen were thought to be distinct from the drusen of age-related macular degeneration based on the differences on fundus examination, autofluorescence, FA and histopathology. As the name suggests, Gass and colleagues described basal laminar drusen as areas of thickening of the retinal pigment epithelium basement membrane. More recently, however, Russell and colleagues have shown similarities in basal laminar drusen and drusen from age-related macular degeneration in terms of their lipoprotein composition, ultrastructure, and sub-retinal pigment epithelium localization.
The pathophysiology is poorly understood. Because of the association with the complement factor H Y402H variant, it is hypothesized that overactivity of the complement cascade is a contributing factor.
The diagnosis of basal laminar drusen is clinical, based on dilated fundus examination, fundus autofluorescence and fluorescein angiography.
Young adults may be found to have basal laminar drusen on routine examination. Patients may have a family history of age-related macular degeneration. In cases that present with complications such as geographic atrophy or CNV, visual complaints may be present.
Dilated fundus examination will reveal numerous, small yellow drusen. Vitelliform pigment epithelial detachments, which are often bilateral, may be present. CNV or geographic atrophy may be present.
Multiple small, yellow drusen in a young adult.
Most cases may be asymptomatic. Patients with vitelliform pigment epithelial detachment, CNV, or geographic atrophy may present with decreased visual acuity, or distortion.
Basal laminar drusen is diagnosed clinically. The presence of multiple, diffusely distributed drusen which are more numerous on fluorescein angiography in a young adult is classic.
Fundus autofluorescence often demonstrates more numerous hyperautoflurorescent drusen than seen on examination. Fluorescein angiography reveals more small drusen than seen on fundus examination, spread diffusely throughout the macula, with a “stars in the sky” appearance. Optical coherence tomography may be helpful in evaluation for CNV and may demonstrate a "saw-tooth" appearance of the drusen.
The differential diagnosis includes other conditions associated with drusen, such as autosomal dominant drusen (Malattia Leventinese), pattern dystrophy, and age related macular degeneration. In patients with vitelliform pigment epithelial detachment, Best disease and adult vitelliform foveomacular dystrophy are also a consideration.
Also, drusen related to [glomerulonephritis type 2] should be excluded.
Patients with basal laminar drusen should be monitored for the development of vitelliform lesions, CNV, or geographic atrophy which may be visually significant.
Treatment is indicated in patients who develop CNV, which may affect or threaten vision. Vision loss due to geographic atrophy is not treatable at this time, however patients with geographic atrophy should continue to be observed for the development of CNV.
In cases of isolated basal laminar drusen, no therapy is indicated. Patients should be observed to monitor for the development of CNV or geographic atrophy. CNV should be treated when detected. Photodynamic therapy has been shown to be effective in cases of basal laminar drusen complicated by CNV. Vitelliform pigment epithelial detachments may be observed and have been reported to resolve spontaneously; treatment with photodynamic therapy worsens vision in these cases. It is unclear whether AREDs vitamins, shown to have some benefit for patients with age-related macular degeneration, are of benefit in patients with basal laminar drusen.
Medical follow up
Patients with basal laminar drusen should be followed regularly to monitor for development of CNV. Patients who develop CNV should be monitored frequently to assess response to treatment. Amsler Grid or preferential hyperacuity perimeter are important measures for self monitoring.
Fundus examination of the family members is important.
As noted above, the main complications are the development of CNV, which has been reported in 21% of cases, and geographic atrophy, which has been reported in 11% of cases.
Visual acuity has been reported as worse than 20/100 in the better seeing eye in 22% of patients.
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Claudia Krispel, MD, PhD for critical review of this article.