Angioid streaks are breaks in the degenerated and mineralized Bruch's membrane, which typically form around the optic disc and radiate from the optic disc. These breaks are usually linear and hence named angioid or like blood vessels. Angioid streaks may be idiopathic or associated with pseudoxanthoma elasticum, Ehlers Danlos syndrome, Sickle cell disease, acromegaly, Paget disease of the bone, and other diseases. Angioid streak may be associated with choroidal neovascularization (CNV), causing metamorphopsia and/or visual decline. Angioid streaks are a risk factor of subretinal bleeding after minor trauma.
Angioid streaks have also been called as Knapp streaks or Knapp striae in honor of the famous German- American ophthalmologist Jacob Hermann Knapp (1832 –1911).
Angioid streaks may be idiopathic in up to 50% of cases.
The most important systemic association of angioid streak is pseudoxanthoma elasticum (PXE) or Gronblad–Strandberg syndrome- It is an autosomal recessive disease caused by the mutation of the ABCC6 gene on chromosome 16. Features include calcification and fragmentation of elastic tissues. The name comes from Ester Elisabeth Grönblad (1898-1942), a Swedish ophthalmologist, and James V Victor Strandberg (1883-1942), a Swedish dermatologist who discussed the association between eye and skin findings in PXE.
PXE is characterized by:
Other associations of angioid streaks include:
The age of onset is variable most commonly it presents in the mid-fifties but may present at a younger age in patients with co-morbidities.
Central visual loss is mainly related to foveal involvement with dehiscence of the Bruch membrane or neovascular membrane formation just under the retina. Choroidal neovascularization is a common cause of vision loss and affects most patients with angioid streaks.
No sexual predilection is described.
The orientation of angioid streaks may be related to force lines due to the pull of intrinsic and extrinsic muscles of the eye around a fixed location (e.g., optic nerve). The fragility and opacification of the Bruch's membrane may be primarily due to the degeneration of the elastic portion of Bruch's membrane along with deposition of calcium, magnesium, or iron salts due to disturbed metabolism.
PXE is characterized by degradation and mineralization of the tissues containing elastin and/or collagen. The Bruch's membrane is hard and fragile in PXE due to calcification.
The histopathological examination in angioid streak reveals:
Angioid streaks are usually asymptomatic visually. The visual decline may result from foveal involvement with an angioid streak, rupture at the area of angioid streak causing subretinal bleed at the fovea, or CNV. These hemorrhages do not have evidence of CNV and usually resolve spontaneously. However, the angioid streak may be associated with CNV, which may cause visual decline and/or metamorphopsia.
Patients with PXE may be referred from the dermatology department for ophthalmic evaluation, leading to the diagnosis of angioid streaks. Other systemic associations will have history and clinical examination findings according to the disease.
The history should try to rule out systemic associations.
A comprehensive ocular examination should be performed. This includes visual acuity, refraction, intraocular pressure, ocular motility, the examination of the ocular adnexa, lacrimal system, cornea, anterior chamber, iris, pupillary reaction including a relative afferent pupillary defect, lens, and fundus.
Clinically, angioid streaks are characterized by:
Associated features include:
Infrared imaging may detect subtle angioid streaks missed in color fundus photo.
Hypo-autofluorescence is usually noted in the area of the angioid streak, and the area of abnormality on autofluorescence may be larger than abnormality visible in color fundus photo or clinical examination.
FFA usually shows window defect corresponding to the area of angioid streaks. FFA is very important to detect choroidal neovascularization.
Optical coherence tomography (OCT) reveals the retinal/subretinal/sub-RPE changes in CNV, and also hyper-reflectivity at the Bruch's membrane level due to calcification. The en-face OCT may reveal the areas of angioid streaks. The choroid may be thinner in eyes with angioid streaks and CNV compared to angioid streaks without CNV.
OCT-angiogram may be used to demonstrate the CNV in the angioid streak.
Indocyanine green angiogram (ICGA) may reveal a speckled pattern of cyanescence at the region of Peau d'orange appearance and reveals the CNV. The angioid streaks may show hypercyanescehce or hypocyanescence or mixed pattern.
Angioid streaks are usually asymptomatic and do not need any treatment.
However, these eyes are more prone to develop subretinal hemorrhage after trivial trauma, and protective eyewear should be used.
All patients with angioid streaks should be screened for potential systemic associations. Examination of family members may give clue to the systemic disease.
In cases with subretinal hemorrhage, a fundus fluorescein angiogram should be performed to rule out CNV. If CNV is absent, the hemorrhage usually resolves on its own.
If CNV is detected, the management options include laser photocoagulation, photodynamic therapy (PDT), transpupillary thermotherapy (TTT), macular translocation surgery, and anti-vascular endothelial growth factor (anti-VEGF) agents. Recurrence of CNV causing vision loss is a concern in the angioid streak.
Among anti-VEGF agents, ranibizumab, aflibercept, and bevacizumab (off-label) have been used with success and may improve or stabilize the visual acuity. All anti-VEGF agents seem to have efficacy against both macular and juxta-papillary CNV and may rapidly improve the retinal anatomy on OCT. Anti-VEGF agents may help stop the activity of CNV without the formation of a scar.
Differential diagnoses of angioid streaks include:
The visual prognosis of untreated patients with choroidal neovascularization is poor. Systemically, though most patients with pseudoxanthoma elasticum have a normal life span, early death can occur due to gastrointestinal hemorrhage, cerebral hemorrhage, and myocardial infarction.
The complications of angioid streaks include:
The initial diagnosis and management of angioid streaks are primarily by the ophthalmologist, but follow up is usually done by the primary care provider and nurse practitioner. Angioid streaks are usually asymptomatic and do not need any treatment. However, these eyes are more prone to develop subretinal hemorrhage after trivial trauma and the clinical team, and specialty-trained ophthalmic nurse should educate the patient on the use of protective eyewear. Due to the rarity in the use of medications, a pharmacist with a background in ophthalmic medications should assist the practitioner in appropriate dosing anti-VEGF agents are used.
All patients with angioid streaks should be screened for potential systemic associations. Examination of family members may give a clue to the systemic disease. Interprofessional collaboration is important for systemic associations including pseudoxanthoma elasticum and sickle cell disease. Various specialties to be included in the loop to manage a patient with pseudoxanthoma elasticum includes but may not be limited to gastroenterology, cardiology, neurology, pulmonary medicine, and genetics.
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