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Editor,—A case of bilateral birdshot chorioretinopathy diagnosed on the basis of indocyanine angiography in the absence of any overt clinical lesions is presented.
A 47 year old woman presented to the eye clinic with a history of photopsia in both eyes left more than right for the past 2 months. She also complained of a scotoma in the temporal field of her left eye. There was no significant ocular history. She had always been a migraine sufferer. She also gave a history of left hemiparesis with complete resolution. She had been investigated for multiple sclerosis and carotid artery disease at that time but all the results were reported to be normal.
On examination her best corrected visual acuity was 6/4 in the right and 6/5 in the left eye. Anterior chamber showed occasional cells in both eyes. The pupillary reactions were normal. Fundus evaluation did not show any signs of any retinal or choroidal disease. Vitreous showed plus cells. Optic discs were hyperaemic on both sides (Fig 1). Goldmann visual fields showed enlargement of the blind spots. Fundus fluorescein angiography revealed leakage from the disc in both eyes more pronounced in the left eye (Fig 2). ICG showed hypofluorescent dots in the choroid which developed early in transit and stayed through the mid phase. These were vasotropic in distribution and spared the peripapillary and macular areas. Retinal and choroidal vasculature was normal (Fig3).
Based on the ICG findings a presumptive diagnosis of birdshot choroidopathy was made. Full blood counts were requested along with a chest x ray, angiotensin converting enzyme, and HLA typing. HLA typing revealed that she was HLA-A 29 positive. The diagnosis of birdshot choroidopathy was thus confirmed and the patient started on systemic steroids for a period of 6 weeks followed by cyclosporin.
Follow up over a period of 6 months showed a marked improvement in her symptoms. Fundus examination still does not show any lesions. The optic discs were still hyperaemic.
It classically presents with painless reduced vision with floaters and occasional photopsia.2 ,3 Often unilateral and asymmetric at presentation, it invariably involves both eyes over time. The anterior segment is usually quiet with vitreous showing variable vitritis. Vitreous base/pars plana exudation is absent. Variable degrees of retinal vascular inflammation along with disc or macular oedema are seen. Presence of scattered oval, non-pigmented, and creamy yellow subretinal spots, with indistinct borders initially seen in nasal to the disc or in the inferior retina is the hallmark of the disease.3 New spots appear and existing spots may coalesce and enlarge with time.4 Long term complications include posterior subcapsular cataracts, retinal and disc oedema, retinal breaks and detachments, preretinal and choroidal neovascularisation with vitreous and subretinal haemorrhage, optic atrophy, and progressive chorioretinal atrophy.4
Fundus fluorescein angiography shows spots to be hypofluorescent in the transit phase which become mildly hyperfluorescent in the later stages.1-3 Optic disc shows dye leakage which is compatible with the clinical picture. Diffuse and extensive dye leakage, a very characteristic sign, is also seen from retinal vasculature. Long term retinal or choroidal complications can also be seen.1-3
Indocyanine angiography shows a number of well delineated hypofluorescent areas exceeding the number seen clinically appearing early in the study and persisting throughout the course of the study. Early appearance, location, and size of these spots help differentiate between other multifocal choroiditis.5 ,6
A strong association up to 96%7 ,8 has been reported between HLA-A29 and birdshot choroidopathy, with HLA-A29 positive patients having a 50-fold greater risk of developing this disease than those without it.4
The case in discussion fitted well into the clinical scenario of birdshot chorioretinopathy and had classic lesion on both ICG and fluorescein angiography but with no obvious clinical lesions. A high index of suspicion along with the use of ICG which demonstrated the classic lesion followed by the fact that the patient was HLA A29 positive helped to make the diagnosis. This case therefore re-emphasises the role of ICG angiography in establishing a diagnosis of chorioretinopathies in absence of clinical lesions.