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Angioid streaks were first described in 1889 by Doyne,1 who described them in a patient with retinal haemorrhages secondary to trauma. Knapp2 first coined the term “angioid streaks” although it was Kopler, in 1917, who correctly determined that angioid streaks represented changes at the level of Bruch’s membrane. Since then, angioid streaks have been described in a diverse group of diseases including pseudoxanthoma elasticum, Paget’s disease, and the haemoglobinopathies such as sickle cell anaemia and β thalassaemia.3 Although angioid streaks have been reported among siblings and family members in association with pseudoxanthoma elasticum, they have not previously been reported in identical twins without any associated systemic conditions.
A 66 year old man with no significant medical history presented to the eye clinic with reduced central vision in the left eye for 6 months. On examination, best corrected visual acuities were RE 6/12 and LE 6/36. Amsler grid testing of the central field showed a central scotoma in both eyes, more pronounced in the right. Funduscopy revealed bilateral, red/brown bands radiating from the optic disc suggestive of angioid streaks, and a lesion at the left macula suggestive of a subretinal neovascular membrane. Fluorescein angiography confirmed angioid streaks showing increased transmission of fluorescence overlying the streaks and peripapillary region. The macula also showed leakage of fluorescein suggestive of a subfoveal neovascular membrane (fig 1). Visual acuity deteriorated to counting fingers in the left eye over 9 months and, to date, he maintains acuity of 6/12 in the right.
Three months later, the identical twin of the above patient was referred by his optician with a haemorrhage at the left macula. Visual acuities were 6/6 in each eye. Funduscopy revealed a small haemorrhage along the left papillomacular bundle. Fundus fluorescein angiogram showed features similar to his brother in the form of angioid streaks associated with a subretinal neovascular membrane (fig 2).
On ophthalmoscopic examination, angioid streaks appear as single or multiple dark red/brown bands radiating form the optic disc. They are thought to represent breaks or dehiscence in a thickened, calcified, and abnormally brittle Bruch’s membrane. The most common systemic association with angioid streaks is pseudoxanthoma elasticum, although in approximately 50% of cases, no systemic association can be identified. Angioid streaks have been reported among siblings and family members in association with pseudoxanthoma elasticum.4–8 In the twins described above, there was no associated systemic condition. In pseudoxanthoma elasticum, it is likely that the defect in Bruch’s membrane may be inherited. Idiopathic angioid streaks in twins have not previously been reported. The most important complication of angioid streaks is the development of a subretinal neovascular membrane.9 Visual disturbance and symptoms secondary to angioid streaks are unusual unless such a membrane is present. Other complications include subretinal haemorrhage without neovascularisation that occur either spontaneously or with relatively minor ocular trauma. We believe that detailed ophthalmoscopic and fluorescein angiographic assessment in twins with angioid streaks may promote further understanding of the condition and facilitate the detection, and possible early therapeutic intervention of, secondary complications such as subretinal neovascularisation.