Both eyes show multiple small yellow deposits scattered over the posterior pole. OCT shows shallow subretinal fluid with cystoid spaces in the retina, and the EOG shows almost no light rise. Think of autosomal recessive bestrophinopathy (ARB). This article shows how ARB looks on the fundus, autofluorescence and OCT, how the EOG and ERG separate it from Best disease, and why you must check the angle.

Think of ARB when
  1. Vision falls between childhood and middle age.
  2. Multiple small yellow deposits sit around the macula and the optic disc in both eyes.
  3. OCT shows shallow subretinal fluid and cystoid spaces in the retina.
  4. The EOG is severely reduced, and the full-field ERG is often abnormal too.
  5. The eyes are hyperopic, with shallow anterior chambers.

What is ARB?

ARB is an autosomal recessive retinal dystrophy caused by mutations in both copies of the BEST1 gene. This is the same gene as in Best disease. The inheritance and the fundus are different, so ARB is regarded as a separate disease. In both diseases, the retinal pigment epithelium (RPE) does not work properly, and lipofuscin builds up.

Best disease is autosomal dominant, so one parent is often affected. In ARB, the parents are carriers, and their fundus and EOG are normal[1].

Symptoms

Typical patients come in with reduced vision at about 10 to 40 years of age, though it can start in early childhood or after 60. Children often still have good central vision. Vision then falls slowly over the years[2].

Findings

Fundus and autofluorescence

ARB does not usually show the single egg-yolk (vitelliform) lesion of Best disease. Instead, many small, round, yellow deposits are scattered over the posterior pole, often around the optic disc as well as the macula. They come from lipofuscin, so they are bright (hyperautofluorescent) on fundus autofluorescence.

Over time, some eyes develop atrophy or fibrosis at the macula[2].

Six panels from one patient with ARB. Two slit-lamp photographs show a shallow anterior chamber, with anterior segment OCT insets measuring the depth. Two widefield fundus photographs show many small yellow deposits over the posterior pole and around the optic disc. Two autofluorescence images show the posterior pole bright.
One patient with ARB. (A, B) Shallow anterior chambers. (C, D) Many small yellow deposits over the posterior pole, around the disc as well as the macula. (E, F) The deposits are bright on fundus autofluorescence. From Zhao et al. 2024, CC BY 4.0. Unchanged.

OCT

OCT shows shallow subretinal fluid (a serous retinal detachment) and cystoid spaces within the retina that can look like schisis. The yellow deposits seen on the fundus sit under the retina as bright material. The subretinal fluid usually stays for years[2].

Two OCT scans through the macula, one from each eye of a patient with ARB. Each shows a shallow dome of subretinal fluid under the fovea and small dark cystoid spaces within the inner retina.
OCT of both eyes in ARB: shallow subretinal fluid (asterisk) and cystoid spaces within the retina. From Casalino et al. 2021, CC BY 4.0. Cropped to panels G and H.

EOG

As in Best disease, the RPE is abnormal, so the electro-oculogram (EOG) is reduced. In ARB, the light rise is severely reduced or absent at every age[2]. Rarely, it is close to normal[1].

ERG

In Best disease, the full-field electroretinogram (ERG) is normal. In ARB, it is often abnormal. It can still be normal in children, so a normal ERG does not rule out ARB[2].

Complications

ARB eyes are often hyperopic, with a short axial length, a shallow anterior chamber and a narrow angle. Angle-closure glaucoma is common. Some patients are first diagnosed with glaucoma, and the retinal disease is found later[1].

Check the anterior chamber and the angle in every patient with ARB. If the angle is narrow, a laser iridotomy is often done to prevent acute angle closure.

Summary

  • ARB is caused by mutations in both copies of BEST1, the gene of Best disease.
  • Look for multiple small yellow deposits that are bright on autofluorescence, and shallow subretinal fluid with cystoid spaces on OCT.
  • The EOG is severely reduced, and unlike in Best disease, the full-field ERG is often abnormal.
  • The eyes are often hyperopic with narrow angles, so check the angle.

References

[1] Zhao D, Gu VY, Wang Y, Peng J, Lyu J, Fei P, Xu Y, Zhang X, Zhao P. Clinical and genetic features in autosomal recessive bestrophinopathy in Chinese cohort. BMC Ophthalmol. 2024;24(1):308. PMID 39048936.

[2] Casalino G, Khan KN, Armengol M, Wright G, Pontikos N, Georgiou M, Webster AR, Robson AG, Grewal PS, Michaelides M. Autosomal recessive bestrophinopathy: clinical features, natural history, and genetic findings in preparation for clinical trials. Ophthalmology. 2021;128(5):706-718. PMID 33039401.

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