Ultrahigh resolution optical coherence tomography of birdshot retinochoroidopathy

1 New England Eye Center, Tufts-New England Medical Center, Tufts University, Boston, MA, USA

2 Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA

3 UPMC Eye Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

Keywords: birdshot retinochoroidopathy; optical coherence tomography

Birdshot retinochoroidopathy is a rare inflammatory eye disease with typical clinical presentation and strong association with the HLA-A29 allele. Characteristic appearances on fluorescein angiogram (FA), indocyanine green (ICG) angiography, and electroretinogram (ERG) have been described.1 However, histopathology of the disease has been rare.2,3 The following case is an example of birdshot retinochoroidopathy imaged with ultrahigh resolution optical coherence tomography (UHR-OCT), capable of 3 μm axial resolution.4 UHR-OCT is able to clearly delineate individual intraretinal layers (fig 1).

Figure 1  Ultrahigh resolution optical coherence tomography image from a normal eye. The intraretinal layers are labelled: NFL, nerve fibre layer, GCL, ganglion cell layer, IPL, inner plexiform layer, INL, inner nuclear layer, OPL, outer plexiform layer, ONL, outer nuclear layer, IS/OS, photoreceptor inner/outer segment junction, RPE, retinal pigment epithelium.

Case report

A 64 year old man presented to the New England Eye Center (NEEC) for progressive visual deterioration despite cataract surgery in the left eye 2 years earlier. The patient’s major complaints were difficulty seeing at night and difficulty driving. Best corrected visual acuity (BCVA) was 20/50 right eye and 20/60 left eye. Anterior eye examination revealed mild cells and flare in both eyes, a moderate cataract in the right eye, and a posterior chamber intraocular lens in the left.

Dilated fundus examination revealed mild vitritis bilaterally. The optic discs appeared slightly pale and the retinal vasculature was narrowed. Fundus appearance was consistent with the diagnosis of birdshot retinochoroidopathy (fig 2A). FA and ICG angiography were also consistent with this diagnosis (fig 2B). Six mm radial macular OCT3 scans showed bilateral epiretinal membranes (ERM), with mild thickening in the left eye. The patient subsequently tested positive for the HLA-A29 antigen. Over the next 6 months, the patient was treated for macular oedema with intravitreal Kenalog injections in both eyes, and the macular oedema subsided.

Figure 2  (A) Colour photograph of the left eye. (B) Fluorescein angiogram of the left eye, 2 minutes after injection. The image shows two small haemorrhages originating from the superior arcade, multiple hyperfluorescent spots, and central cystoid macular oedema.

UHR-OCT images were obtained 6 months later (fig 3), at which time BCVA remained stable. Repeat fundus examination and OCT3 imaging revealed an ERM with no macular oedema and normal retinal thickness in both eyes. UHR-OCT images additionally showed photoreceptor atrophy in several areas of both eyes. RPE degeneration was present underneath areas of photoreceptor involvement. The inner retinal layers were difficult to delineate, probably because of anatomical disorganisation of these layers.

Figure 3  (A) Horizontal ultrahigh resolution OCT (UHR-OCT) image through the right macula. Notable are an epiretinal membrane (ERM) (yellow arrows), and an area of thinning of the outer nuclear layer (ONL) with underlying absence of the photoreceptor inner/outer segment junction (IS/OS) (red asterisk). Retinal pigment epithelium (RPE) disruption is also seen as an increase in choroidal signal backscattering. Other retinal layers are also labelled as in figure 1. (B) Horizontal UHR-OCT image through the left macula. ERM is present (yellow arrows). Thinning of the ONL and disruption of the photoreceptor IS/OS junction is present outside of the fovea (red asterisks). RPE disruption is also present in these areas. The inner retinal layers are not clearly delineated.

Comment

This case represents a fairly severe case of birdshot retinochoroidopathy. In a review by Gasch et al, epiretinal membrane was the second most common complication of birdshot retinochoroidopathy next to macular oedema,1 which our patient also had on initial presentation. ERG findings have shown Mueller and bipolar cell involvement early in the disease, while photoreceptors are affected later.1 The UHR-OCT images presented here show disorganisation of inner retinal layers as well as photoreceptor and RPE atrophy. Choroidal ischaemia, suggested by ICG angiography, may be the cause of RPE and photoreceptor degeneration.

We found two histolopathological reports of birdshot retinochoroidopathy. One case was a blind phthisical patient.2 The other was a more typical yet mild case, which showed lymphocytic infiltration around the choroidal and retinal vasculature with minimal retinal disturbance.3 Serial UHR-OCT imaging of patients could help in understanding and following progression of macular involvement in this disease.

References

Gasch AT, Smith JA, Whitcup SM. Birdshot retinochoroidopathy. Br J Ophthalmol 1999;83:241–9.

Nussenblatt RB, Mittal KK, Ryan S, et al. Birdshot retinochoroidopathy associated with HLA-A29 antigen and immune responsiveness to retinal S-antigen. Am J Ophthalmol 1982;94:147–58.

Gaudio PA, Kaye DB, Crawford JB. Histopathology of birdshot retinochoroidopathy. Br J Ophthalmol 2002;86:1439–41.

Drexler W, Morgner U, Ghanta RK, et al. Ultrahigh-resolution ophthalmic optical coherence tomography. Nat Med 2001;7:502–7.