Iris microhemangioma
Key Points at a Glance
Section titled “Key Points at a Glance”1. What is Iris Microhemangioma?
Section titled “1. What is Iris Microhemangioma?”Iris microhemangioma, also called Cobb’s tufts or iris vascular tufts, is a tiny tangled vascular lesion that occurs at the pupillary margin. In 1932, Tyson first reported a case in association with spontaneous hyphema, and in 1969, Cobb described and named 44 cases in detail, establishing its name 1).
The lesion is essentially a small, twisted or coiled mass of blood vessels lined by endothelial cells within the iris stroma, classified as a hamartoma rather than a true tumor 1). It is a rare lesion, accounting for about 2% of all iris tumors.
Age at onset ranges from 36 to 86 years (mean 65 years, median 67 years), with no sex or racial predilection 1). Approximately 90 cases had been reported before 2013, and a 2021 systematic review accumulated a total of 115 cases 1). It is usually bilateral.
Rubeosis iridis (iris neovascularization) is pathological neovascularization associated with diabetes and ischemic ocular diseases, accompanied by fibrovascular membranes that spread across the entire iris and angle. In contrast, iris microhemangioma is a localized, elevated vascular tuft at the pupillary margin, without fibrovascular membranes, and shows no leakage on iris fluorescein angiography, which helps differentiate it1).
2. Main Symptoms and Clinical Findings
Section titled “2. Main Symptoms and Clinical Findings”Subjective Symptoms
Section titled “Subjective Symptoms”Most cases are asymptomatic. When complications (hyphema) occur, the following symptoms may appear.
- Sudden blurred vision or vision loss: Varies from mild to light perception depending on the amount of hyphema. This is the most common complaint1).
- Eye pain or discomfort: Occurs when accompanied by elevated intraocular pressure.
- Awareness of “blood in the eye”: Patients may notice hyphema themselves.
- Transient vision loss: Symptoms resolve within hours and may be mistaken for amaurosis fugax1).
Symptoms usually resolve spontaneously within 48 hours1).
Clinical Findings
Section titled “Clinical Findings”Slit-lamp examination: Bilateral small red to reddish-brown nodules at the pupillary margin. They are 15–150 micrometers in size, and high magnification may be needed to identify them in eyes with dark iris pigmentation1). Multiple microhemangiomas are often scattered.
Iris fluorescein angiography: Shows early hyperfluorescence and late faint staining, but no clear dye leakage. This is an important distinguishing feature from rubeosis. It has been reported that only one-third of iris vascular tufts confirmed clinically are visualized as additional lesions on iris fluorescein angiography, making it useful for assessing the full extent of lesions1).
When complicated by hyphema: In a series of 22 eyes, about half had at least one hyphema, and one-third developed secondary glaucoma1). The mechanism of elevated intraocular pressure is obstruction of the trabecular meshwork by blood.
3. Causes and Risk Factors
Section titled “3. Causes and Risk Factors”Etiology
Section titled “Etiology”The lesion is thought to be acquired, with no reported cases in children 1). There has been ongoing debate about whether it is due to congenital abnormalities of iris stromal vessels or acquired microvascular proliferation, but the acquired mechanism is currently supported. Histologically, it corresponds to a hamartoma with normal cell thickness lacking fenestrations, composed of endothelial cells surrounded by pericytes and loose connective tissue 1).
Association with systemic diseases
Section titled “Association with systemic diseases”Associations with specific systemic diseases have been reported, which can serve as diagnostic clues.
| Disease | Reported association |
|---|---|
| Myotonic dystrophy | Iris vascular tufts in approximately 12.5% of patients |
| Type 2 diabetes | Iris vascular tufts in approximately 6.7% of patients |
| Chronic obstructive pulmonary disease | Reported in multiple cases |
| Congenital cyanotic heart disease | Association with hypoxemia and venous stasis suggested |
The association with myotonic dystrophy is best known, first reported by Cobb et al. in 1970. It has been suggested that hyperinsulinemia may contribute to iris neovascularization1). However, many patients have no systemic disease1).
4. Diagnosis and examination methods
Section titled “4. Diagnosis and examination methods”Diagnosis is primarily clinical, but the following tests are supportive.
Slit-lamp biomicroscopy
Section titled “Slit-lamp biomicroscopy”The basic step is to identify microvascular tufts at the pupillary margin. Lesions can be very inconspicuous, requiring high-magnification observation to avoid oversight. Active bleeding or blood clots may also be observed.
Gonioscopy
Section titled “Gonioscopy”This is useful for evaluating the angle and confirming the absence of angle neovascularization (rubeosis). In the acute phase of hyphema, it should be avoided due to the risk of rebleeding.
Iris fluorescein angiography
Section titled “Iris fluorescein angiography”This is the most recommended test for confirming the diagnosis and assessing the full extent of the lesion. Lesions show early hyperfluorescence and late staining, without the clear leakage seen in rubeosis 1). Performing iris fluorescein angiography before treatment is recommended 1).
Anterior segment optical coherence tomography angiography
Section titled “Anterior segment optical coherence tomography angiography”A new imaging technique that can non-invasively visualize blood flow in microvessels. The first report of anterior segment optical coherence tomography angiography of iris vascular tufts was by Kang et al. in 2017 1). It is attracting attention as an alternative to iris fluorescein angiography, but further research is needed for widespread adoption.
Blood and Urine Tests
Section titled “Blood and Urine Tests”Complete blood count, coagulation screening, and urinalysis are normal in most cases, but are recommended for the differential diagnosis of spontaneous hyphema. Fasting blood glucose and oral glucose tolerance tests are also recommended due to the association with diabetes 1).
Differential Diagnosis
Section titled “Differential Diagnosis”The most important differential diagnosis is uveal melanoma, which is excluded by iris fluorescein angiography and regular photographic follow-up 1). Other differentials include rubeosis, iris hemangioma, hereditary hemorrhagic telangiectasia, and inflammatory iris vessels.
It has been reported that only one-third of iris vascular tufts recognized by slit-lamp microscopy are visualized as additional lesions on iris fluorescein angiography 1). When a lesion is found clinically, performing iris fluorescein angiography as an adjunct is useful for understanding the full extent of the lesion and planning treatment.
5. Standard Treatment
Section titled “5. Standard Treatment”Observation (Conservative Management)
Section titled “Observation (Conservative Management)”In most cases, observation is recommended if there is no hyphema or only an initial mild hyphema 1). Regular monitoring is performed to check for new bleeding.
Acute Phase (Hyphema) Management
Section titled “Acute Phase (Hyphema) Management”Acute management when hyphema occurs:
- Rest and head elevation: Recommended as initial management.
- Topical corticosteroid eye drops: Reduce inflammation and stabilize the blood-aqueous barrier.
- Cycloplegic eye drops (e.g., cyclopentolate): Help hemostasis by dilating the pupil.
- Intraocular pressure management: If elevated, use aqueous suppressants (e.g., acetazolamide, beta-blocker eye drops) 1).
Most hyphemas resolve within a few days1).
Argon Laser Photocoagulation
Section titled “Argon Laser Photocoagulation”This is the most commonly reported treatment for recurrent hyphema or cases unresponsive to medical therapy1). It is recommended to perform with IFA guidance1).
Sarmad et al. (2018) reported performing argon laser photocoagulation with parameters of ARI 532nm, 2 burns, spot size 50μm, 0.1 seconds, 400mW, and found no recurrence at 5-year follow-up1).
Laser irradiation parameters vary widely across studies, and no consensus on optimal settings has been established1). Argon laser photocoagulation was indicated in only about 9% of all iris vascular tufts, with the majority managed by observation alone1).
Iridectomy
Section titled “Iridectomy”This is considered when symptoms persist after laser treatment or when malignancy is suspected. It offers the advantage of no recurrence and allows clinical exclusion of malignant findings1).
Precautions during cataract surgery
Section titled “Precautions during cataract surgery”In patients with known iris microhemangiomas undergoing intraocular surgery, prophylactic argon laser photocoagulation to prominent vascular tufts may be considered to reduce the risk of intraoperative and postoperative hyphema. However, there are reports of cataract surgery performed without argon laser photocoagulation and completed without bleeding1).
6. Pathophysiology and detailed pathogenesis
Section titled “6. Pathophysiology and detailed pathogenesis”The pathophysiology of iris microhemangiomas is not fully understood.
Initially thought to be a congenital developmental anomaly of the iris vasculature, the absence of reported cases in children now supports an acquired degenerative mechanism1).
In relation to systemic diseases, the following mechanisms have been suggested.
- Microvascular disorder theory: Systemic microvascular disorders associated with myotonic dystrophy affect the iris vessels.
- Iris tissue hypoxia and venous stasis theory: In chronic obstructive pulmonary disease and congenital cyanotic heart disease, chronic hypoxia and venous stasis are thought to promote microvascular changes in iris tissue. Krarup reported that in cases of iris vascular tufts with congenital cyanosis, “prolonged venous stasis and secondary iris tissue hypoxia are common factors in the presence of local or systemic disease” 1).
- Biochemical changes in aqueous humor theory: Changes in aqueous humor composition due to cataracts, diabetes, respiratory failure, decreased intraocular pressure, etc., are hypothesized to induce proliferation of iris vascular tufts 1).
- Hyperinsulinemia theory: In patients with myotonic dystrophy, hyperinsulinemia due to increased reactivity of pancreatic beta cells may contribute to iris neovascularization 1).
Histologically, it is described as a hemangioma with normal cell thickness, where endothelial cells are surrounded by pericytes and loose connective tissue, without fenestrations (tight junctions preserved), distinguishing it from diabetic neovascularization and pathological rubeosis 1).
7. Latest Research and Future Perspectives
Section titled “7. Latest Research and Future Perspectives”Optical Coherence Tomography Angiography (OCTA)
Section titled “Optical Coherence Tomography Angiography (OCTA)”Optical coherence tomography angiography is expected as a non-invasive alternative to iris fluorescein angiography. In 2017, Kang et al. first reported optical coherence tomography angiography images of iris microhemangiomas1). Compared to iris fluorescein angiography, it offers advantages such as no need for contrast agents, short acquisition time, and three-dimensional visualization. However, further multicenter studies are needed for its widespread adoption1).
Establishment of Optimal Laser Parameters
Section titled “Establishment of Optimal Laser Parameters”Current argon laser photocoagulation protocols are mostly based on case reports and small case series, and there is no established consensus on optimal settings for spot size, power, duration, and number of applications1). The need for large-scale prospective studies has been pointed out.
Role of Prophylactic Laser Before Cataract Surgery
Section titled “Role of Prophylactic Laser Before Cataract Surgery”There are conflicting data regarding the necessity of preoperative argon laser photocoagulation in patients with iris vascular tufts undergoing intraocular surgery, and no established recommendation exists1). Further accumulation of evidence is required.
8. References
Section titled “8. References”- Almafreji I, Manton A, Peck FS. Cobb’s Tufts: A Systematic Review. Cureus. 2021;13(12):e20151. DOI:10.7759/cureus.20151
- Roberts DK, Haine CL. Iris microhemangiomas. J Am Optom Assoc. 1988;59(10):780-4. PMID: 3183274.
- Ison M, Dorman A, Imrie F. Spontaneous hyphema from iris microhemangioma in Eisenmenger syndrome. American journal of ophthalmology case reports. 2022;26:101536. doi:10.1016/j.ajoc.2022.101536. PMID:35496761; PMCID:PMC9046946.