Best Disease
Best
macular dystrophy
Sawsan Bu
Orm, MD
Histopathology:
Lipofuscin
accumulation in RPE, photoreceptors and choriocappilaris
Lipofuscin : e- dense, autofluoresent and PAS positive, thought to be
the result of liposomal destruction
of the RPE leading to loss of their function
Genetics:
Active area of investigation.
AD with variable penetrance.
Localized to chromosome 11q13.
Best candidate is ROM-1 gene, a photoreceptor specific protein because of
its similarity with RDS
pr responsible for some cases of RP and macular degeneration.
No mutation has been identified yet.
Clinical presentation:
Lesion is usually central but eccentric lesions have
been described
Multifocal lesions can occur,
usually in older individuals
Vessels are undisturbed past the border
May develop within 10 days, may shift with head rotation and occasionally
disappears spontaneously
Usually seen in early childhood (3 to 15yrs) but also described at birth
Syxs are decrease VA, metamorphopsia or patient can be diagnosed on routine
eye exam
Refraction : Hyperopia +/_ astigmatism
Staging (?)
Stage 0 : normal fundus, abnormal EOG à
Carrier
Stage 1 : pigment motling à
Previtelliform
Stage 2 : Vitelliform or egg yolk à
size of lesion from 0.5 to 3 DD
Stage 3 : Srambeled egg appearance
Stage 4 : subretinal
scaring
Effect on visual
acuity
Visual acuity is relatively normal till age of 40 where
VA decreases to 20/40 or less
A study of 74 patients stage two and above showed:
-76% of patients younger than
40 yrs have VA better than 20/40
-20 % of patients older than
40 yrs have VA better than 20/40
-Only 16 % of patients aged
between 30 and 72 years are legally blind ( VA equal or less
than 20/200)
Early stages are usually accompanied with good VA in
spite of striking fundus picture
Decrease in VA usually occurs after the stage of scrambled egg because of
RPE atrophy and
abnormalities in the sensory retina
Acute decrease in VA can occur with disintegration of material, hemorrhage
and exudates into the lesion
Fluctuation of visual acuity occur with or without change in fundus
appearance
VA usually asymmetric and not proportional to fundus exam
64 % have a difference of 2 Snellen lines between the two eyes
Visual loss may be reversible and unpredictable
Diagnostic
Modalities:
-Color vision: mild red green dyschromatopsia and
decrease in hue descrimination
- Visual
field: usually normal, may show
decrease sensitivity in central
VF
scotoma
to red than green than white
- ERG : normal
full field but may have abnormal foveal ERG
- Dark adaptation: usually normal
- EOG : main diagnostic modality
To be confident with the diagnosis:
-
AD
-
Moderate to severeabnormality in EOG
-
One of the typical lesions
-
Typical onset and clinical course
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