Choroidal Nevus: NBEO and OKAP Review

Master choroidal nevus features, TFSOM-UHHD risk factors and melanoma clues for NBEO and OKAP exam preparation.

Reviewed for accuracyAugust 4, 20263 min read

Warm-up

What is the most common benign intraocular tumor in adults?

Lesson

Choroidal Nevus in 30 Seconds

A choroidal nevus is a benign melanocytic lesion within the choroid, usually at the posterior pole. Most remain stable and asymptomatic. For NBEO and OKAP, recognize the benign pattern but monitor for features suggesting transformation into choroidal melanoma.

Typical Features

Appearance: slate-gray to brown choroidal lesion that is typically flat or minimally elevated. Exam relevance: a quiet, minimally elevated lesion favors nevus.
Size: most are less than 5 to 6 mm in basal diameter and less than 2 mm thick. Exam relevance: greater thickness raises concern for melanoma.
Drusen: overlying drusen suggest chronicity and favor benignity. Exam relevance: drusen is a reassuring chronic feature.
Margins: well-defined. Exam relevance: clear margins support a typical benign appearance.
Location: choroid, often posterior pole. Exam relevance: identify the lesion as choroidal, not retinal.
Symptoms: most patients are asymptomatic. Exam relevance: new flashes, blurred vision or visual field defects increase concern for melanoma.
RPE changes: long-standing nevi often develop overlying drusen and RPE alterations, indicating chronicity rather than malignant transformation.

Risk Factors for Malignant Transformation

The mnemonic TFSOM-UHHD, meaning To Find Small Ocular Melanoma Using Helpful Hints Daily, identifies risk factors for transformation into small choroidal melanoma:

T: thickness greater than 2 mm
F: subretinal fluid
S: symptoms, especially vision loss
O: orange pigment from lipofuscin
M: margin within 3 mm of the optic disc
UH: ultrasound hollowness
H: halo absence
D: drusen absence

4 Facts Exams Always Ask

Choroidal nevus is a common benign melanocytic lesion that still requires surveillance for melanoma transformation.
TFSOM-UHHD organizes the clinical features that predict nevus growth into small ocular melanoma.
Melanoma is more likely with greater size or thickness, subretinal fluid and orange pigment.
Low-risk lesions need serial photography and observation. High-risk lesions require ocular oncology referral.

The Classic Trap

The key board trap is separating benign choroidal nevus from small choroidal melanoma. Overlying drusen and a surrounding halo favor benignity. Orange lipofuscin pigment, subretinal fluid, thickness over 2 mm and proximity to the optic disc favor melanoma. No single feature is definitive, so assess the combined risk profile. Documented growth remains the strongest evidence that a lesion is melanoma.

Clinical Pearl

Use TFSOM-UHHD with serial imaging rather than relying on lesion color alone. A nevus with zero risk factors has a very low chance of growth. The likelihood of growth increases with each additional TFSOM-UHHD feature, and lesions with multiple risk factors warrant prompt ocular oncology referral. Documented growth is the strongest single sign of malignancy.

Check yourself

Checkpoint 1

Orange pigment over a melanocytic choroidal lesion most commonly represents what substance?

Checkpoint 2

Which of the following is a suspicious feature for choroidal melanoma rather than nevus?

Clinical case

During a routine dilated examination, a patient has a pigmented choroidal lesion near the optic disc. It measures 2.4 mm thick on ultrasound. Fundus examination shows orange pigment and no overlying drusen. The patient reports recent blurred vision in that eye. What is the most appropriate clinical concern?

Which feature is most concerning for transformation of a choroidal nevus into melanoma?

Explanation

Thickness greater than 2 mm is a classic risk factor for nevus transformation and is included in commonly used risk stratification schemes. Drusen and a surrounding halo are more often associated with chronicity and relative benignity.

Case discussion

This lesion has multiple TFSOM-UHHD risk factors: thickness over 2 mm, symptoms, orange pigment, proximity to the optic disc and drusen absence. The combined pattern raises concern for small choroidal melanoma rather than a low-risk nevus, and prompt ocular oncology referral is appropriate.

Sources & Reviewer Info

Reviewed by Vasilis Inglezis: Optometrist and Ocular Oncology Imaging Specialist, Ocular Oncology Center, Athens, Greece. Last updated August 4, 2026.

References

American Academy of Ophthalmology. BCSC Section 4: Ophthalmic Pathology and Intraocular Tumors.
Shields CL, Shields JA. Clinical Ocular Oncology.
American Academy of Ophthalmology. EyeWiki: Choroidal Nevus.

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