Iris Arteriovenous Malformation

All content on Eyewiki is protected by copyright law and the Terms of Service. This content may not be reproduced, copied, or put into any artificial intelligence program, including large language and generative AI models, without permission from the Academy.

Article initiated by:

Harpreet Walia, MD

All contributors:

Harpreet Walia, MD, Joobin Khadamy, MD, FEBO, Jill Wells, MD

Assigned editor:

Erica Renee Alvarez, MD

Review:

Assigned status Update Pending

 by Jill Wells, MD on April 22, 2023.

add
Contributing Editors:	add

Disease Entity

Disease

Iris arteriovenous malformations (AVM) are rare benign vascular lesions which have also been called iris racemose hemangiomas. This is not a true neoplasm, but rather an anomalous arteriovenous malformation with a tangle of vascular channels at the site of the communication.

Etiology

These vascular lesions are congenital. They are not associated with any systemic or ocular conditions.

General Pathology

The basic underlying pathology is an artery connects directly to a vein bypassing the capillary network. This is thought to be due to a local failure of mesenchymal cell maturation. In normal early vascular development, primitive mesenchymal cells differentiate into solid cords, which then become canalize to form capillary networks. As blood enters the system, arteries, capillaries, and veins are formed. The intervening capillaries then retract and atrophy. In iris AVM, extensive atrophy occurs, leaving a single channel to shunt blood across the defective capillary zone.

Pathophysiology

On microscopic examination, iris AVMs appear as telangiectatic vessels lined by endothelial cells.

Diagnosis

The diagnosis of Iris AVM can be made on a clinical basis with careful slit lamp examination. While these lesions are benign in nature, they must be differentiated from other causes of abnormal iris vessels such as other iris hemangiomas, pathologic neovascularization of the iris, and dilated normal vessels resulting from chronic inflammation. Additionally, these lesions often present with a sclera sentinel vessel and thus concomitant malignancy such as uveal melanoma must be ruled out.

History

These lesions are non-progressive. While they are congenital in nature, most cases of iris AVMs are reported to present during the sixth decade.

Physical examination

Careful slit lamp exam reveals a tortuous, dilated vascular loop running from iris root to peripupillary region and back. These lesions usually are two clock hours in size. Additionally, these vessels can be visualized by gonioscopy.

Symptoms

Iris AVMs are typically asymptomatic and do not impair visual acuity.

Diagnostic procedures

Iris Fluoroscein Angiography (FA) can be used in diagnosis. FA will reveal a rapidly filling hyperfluorescent lesion with no late phase leakage. Intervening iris hypoperfusion can be visualized as well. In patients with darker irises, iris indocyanine green angiography can be used to for better penetration through the pigmentation and minimal leakage may be seen.

Differential diagnosis

While generating a differential diagnosis, the clinician should consider:

• Iris hemangioma
• Pathologic neovascularization of the iris
• dilated normal vessels resulting from:
  • Chronic inflammation
  • Dilated normal vessels resulting from underlying malignancy

• Iris hemangiomas
  • Capillary hemangioma:
    • Capillary hemangiomas typically present in infancy and can be associated with the systemic conditions of diffuse neonatal hemangiomatosis (DNH) and periorbital capillary hemangioma.
      • These lesions appear as multiple iris hemangiomas and on microscopic examination appear as closely packed, flattened endothelial cells separated by a connective tissue stroma.
  • Cavernous hemangioma:
    • Cavernous hemangiomas also typically present in infancy or childhood and appear as multilobulated blood-filled lesions that mimic clusters. The can also be associated with DNH as well as CNS and cutaneous hemangiomas. On microscopic examination, they appear as large, cavernous vascular spaces with intervening connective tissue stroma.
  • Microhemangioma:
    • Microhemangiomas appear in adults as tiny vascular tufts usually found near the pupillary margin and can be associated with diabetes mellitus and myotonic dystrophy. On microscopic examination, they appear as small, tightly coiled blood vessels.
• Iris varix
  • Iris varix is a condition characterized by elongated and dilated veins within the iris of the eye. It can be mistaken for other conditions such as iris hemangioma or melanoma. It is typically unilateral, often located in the inferotemporal quadrant of the iris, and can have a radial or circumferential orientation. It may be associated with features like a dilated episcleral sentinel blood vessel but does not exhibit characteristics of malignancy. Iris varix cases remains stable during follow-up, and no secondary tumors were observed. Iris varix, experiencing repeated hemorrhages into the anterior chamber, may result in secondary glaucoma. When these veins become thrombosed they may resemble iris melanoma.

Management

Since iris AVMs are benign, non-progressive lesions, the treatment of choice is observation with periodic follow-up.

Complications

While complications of iris AVM are rare, the most common complication arising is spontaneous hyphema. Iris AVM associated hyphema is managed as primary hyphema. Additionally, depending on the location of the iris AVM, any intraocular surgery, such as cataract surgery, should prompt careful attention by the surgeon.

Prognosis

Iris AVMs carry very little risk for morbidity or mortality and thus confer an excellent prognosis.

References

1. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 2. Fundamentals and Principles of Ophthalmology. San Francisco: American Academy of Ophthalmology; 2023-2024.
2. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 4. Ophthalmic Pathology and Intraocular Tumors. San Francisco: American Academy of Ophthalmology; 2023-2024.
3. Broadus E, Lystad L, Schonfield L, Singh AD. Iris Varix: Report of a Case and Review of Iris Vascular -Anomalies. Survey of Ophthalmology. 54. Jan –Feb 2009.
4. Ferri AP. Hemangiomas of the iris and ciliary body: do they exist? A search for a histologically proved case. Int Ophthlmol Clinc. 1972
5. Mahmoud M, et al. Pathogenesis of Arteriovenous Malformations in the Absence of Endoglin. Circulation Research. March 2010.
6. Parodi MB, Bondel E, Saviano S, Da Pozzo S, et al. Iris arteriovenous communication: Clinical and angiographic features. International Ophthal 22; 1-5; 1998.
7. Prost M. Arteriovenous communication of the iris. Br J Ophthalmol. 1986 70: 856-859
8. Shields JA, Biancotto C, Kligman B, Shields CL. Vascular Tumors of the Iris in 45 patients. Arch Ophthalmol. 2010; 128(9): 1107-1113
9. Shields JA, Streicher TF, Sprikova JH, Stubna S, et al. Arteriovenous Malformation of the Iris in 14 Cases. Arch Ophthalmol. 2006; 124: 370-375.
10. Vavvas D, Fay A, Watkins L. Two cases of orbital lymphangioma associated with vascular abnormalities of the Retina and Iris. Ophthalmology 2004; 111: 189-192.