Choroidal Nevus: NBEO and OKAP Review
Master choroidal nevus features, TFSOM-UHHD risk factors and melanoma clues for NBEO and OKAP exam preparation.
What is the most common benign intraocular tumor in adults?
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 current multimodal-imaging mnemonic is TFSOM-DIM, which links each risk factor to the imaging modality that detects it:
- T: thickness greater than 2 mm on ultrasonography
- F: subretinal fluid on OCT
- S: symptoms, especially vision loss
- O: orange pigment on autofluorescence
- M: melanoma acoustic hollowness on ultrasonography
- DIM: diameter greater than 5 mm on photography, and margin touching the optic disc
Each additional factor raises the risk of growth into small choroidal melanoma. The older mnemonic TFSOM-UHHD (To Find Small Ocular Melanoma Using Helpful Hints Daily) is still widely taught as a legacy version and adds ultrasound hollowness, halo absence and drusen absence.
4 Facts Exams Always Ask
- Choroidal nevus is a common benign melanocytic lesion that still requires surveillance for melanoma transformation.
- TFSOM-DIM, with TFSOM-UHHD as the legacy version, organizes the imaging 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-DIM with multimodal 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 risk factor, and lesions with multiple factors warrant prompt ocular oncology referral. Documented growth is the strongest single sign of malignancy.
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?
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?
Sources & Publisher Info
Last clinically reviewed: August 9, 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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