How Melanoma Can Affect Vision: Mechanisms, Symptoms, and When to Seek Care

Melanoma can cause vision problems in two main ways: by forming a primary tumor inside the eye (ocular or uveal melanoma) and by spreading (metastasizing) from skin melanoma to the eye or orbit. Primary eye melanoma often develops in the uveal tract (iris, ciliary body, choroid) and can directly disturb retinal function, fluid balance, and the optics of the eye, leading to visual changes. ^{[1] [2]} Cutaneous melanoma can also metastasize to structures of the eye and orbit, compressing the optic nerve or retina, which may cause sudden vision loss or other visual symptoms. ^[3] These processes are clinically significant and should prompt timely evaluation because early detection can influence eye preservation and overall outcomes. ^[4]

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How Melanoma Causes Vision Problems

Ocular (Uveal) Melanoma

• Location and impact: Eye melanoma most commonly arises in the uvea, the vascular layer beneath the white of the eye, where it can alter vision by affecting the retina and fluid layers. ^[5] When melanoma grows in the choroid, it may induce retinal detachment, causing blurred or distorted vision and areas of missing vision. ^[6] Tumors in the ciliary body can change lens position and shape, leading to focusing problems, double vision, or blurry vision. ^[6]
• Optical and mechanical changes: A growing dark spot on the iris or changes in pupil shape can affect how light enters the eye, disrupting visual clarity and peripheral vision. ^[1] Accumulation of fluid under the retina (serous detachment) can produce wavy lines or patchy missing areas in the visual field. ^[6]
• Functional retinal disturbance: Eye melanoma can present with flashes of light and “floaters,” reflecting retinal irritation or vitreous changes. ^[1] These symptoms are common in uveal tumors that disturb the retina or vitreous. ^[1]

Metastatic Melanoma to the Eye/Orbit

• Direct compression and infiltration: Metastatic lesions can involve the orbit and optic nerve, leading to sudden, painless vision loss, disc swelling, or other visual deficits. ^[3] Such orbital metastasis is rare but serious, often occurring in advanced systemic disease, and warrants urgent imaging and specialist evaluation. ^[3]
• Paraneoplastic retinal dysfunction: In some cases, melanoma may trigger immune-mediated (paraneoplastic) disruption of retinal signaling, causing night blindness and abnormal retinal electrical responses even without visible ocular tumors. ^[7]

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Visual Symptoms That Should Prompt Medical Evaluation

Urgent (Same-Day) Evaluation

• Sudden vision loss in one eye or rapid decline in vision clarity. ^[1] This can signal retinal detachment, optic nerve compression, or acute intraocular complications, and should be assessed immediately. ^[2]
• New, significant loss of side (peripheral) vision. ^[1] Peripheral field loss can indicate tumor impact on retinal pathways or optic nerve involvement. ^[1]
• New flashes of light, a shower of floaters, or a “curtain” over vision. ^[1] These may represent retinal traction or detachment associated with intraocular tumors. ^[1]
• Painful, red eye with blurred vision or light sensitivity. While eye melanoma itself is often painless, inflammation (uveitis) or fluid under the retina can present with blurred vision, photophobia, and redness and needs prompt ophthalmologic evaluation. ^{[8] [9]}

Prompt (Timely) Eye Exam Within Days

• A growing dark spot on the iris or a change in iris color. ^[1] Iris lesions can represent anterior uveal melanoma and warrant slit-lamp evaluation. ^[1]
• Change in pupil shape or new irregularity. ^[1] Pupil distortion can reflect tumor in the iris or ciliary body affecting ocular structures. ^[1]
• New blurred or double vision, especially in one eye. ^[1] This may arise from ciliary body involvement or retinal changes affecting focus and alignment. ^[6]
• Distorted vision (straight lines look wavy) or patchy missing areas in a grid. These are classic signs of macular or subretinal fluid changes that can occur with choroidal melanoma. ^[6]
• Visible bulging or displacement of the eye. Orbital involvement can shift the eye position and cause visual disturbance. ^[6]

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Common Ocular Melanoma Symptom Patterns

• Asymptomatic detection is common: Many eye melanomas are found incidentally on routine exams before symptoms develop, highlighting the importance of periodic comprehensive eye evaluations. ^[4]
• Typical symptomatic presentation: When symptoms occur, they often include visual acuity or field defects, flashes or floaters, and less commonly pain. ^[10] Medium-sized choroidal melanomas are more likely to present with symptoms than very large tumors, which may have already caused structural changes. ^[10]

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Comparison: Ocular vs. Metastatic Melanoma Visual Signs

Feature	Ocular (Uveal) Melanoma	Metastatic Melanoma to Eye/Orbit
Typical origin	Primary tumor within uvea (iris, ciliary body, choroid) [5]	Spread from cutaneous melanoma to orbit/eye structures [3]
Common symptoms	Flashes, floaters, blurred vision, iris dark spot, pupil shape change, peripheral vision loss, distortion/wavy lines [1] [6]	Sudden painless vision loss, optic disc swelling, eye displacement, visual field defects [3]
Mechanisms	Retinal detachment/serous fluid, optical disruption, macular distortion [6]	Optic nerve compression, retinal involvement, orbital mass effect [3]
Urgency	Prompt ophthalmology referral; sudden changes need emergency care [2]	Urgent imaging and oncologic/ophthalmologic co-management [3]
Asymptomatic rate	Frequently detected incidentally on routine exams [4]	Often occurs with disseminated systemic disease and advanced symptoms [3]

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Why Early Evaluation Matters

• Diagnosis and eye preservation: Timely detection of uveal melanoma allows personalized treatment planning (e.g., plaque radiotherapy, laser, surgery) that can preserve vision and the eye. ^[4]
• Systemic implications: Uveal melanoma carries a risk of metastasis, particularly to the liver, and requires coordinated surveillance and management. ^[11] Orbital metastasis from cutaneous melanoma indicates advanced disease and needs rapid multidisciplinary care. ^[3]
• Prognosis and staging: Clinical exam and imaging (ultrasound, fluorescein angiography, CT/MRI) complement each other to stage ocular tumors and guide therapy. ^[4]

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When to Seek Care and What to Expect

• Seek urgent care for sudden vision loss, new peripheral field loss, or a dramatic increase in flashes/floaters especially with a “curtain” over vision. ^{[1] [2]}
• Arrange a timely eye exam for any new dark spot on the iris, pupil shape change, persistent blurred/double vision, or distorted vision. ^{[1] [6]}
• Expect a comprehensive ophthalmic evaluation, including dilated exam and imaging (B-scan ultrasound, optical coherence techniques, and sometimes MRI/CT for orbital assessment). ^[4]
• If you have a history of melanoma elsewhere and develop visual symptoms, inform the eye specialist, as this may guide imaging and urgency. ^[3]

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Key Takeaways

• Melanoma can affect vision either as a primary eye tumor (ocular/uveal melanoma) or by metastasizing to the eye/orbit. ^{[5] [3]}
• Warning signs include flashes, floaters, blurred vision, peripheral vision loss, iris dark spots, pupil changes, distorted or missing parts of the visual field, and sudden vision loss. ^{[1] [6] [2]}
• Early evaluation improves the chance of preserving vision and managing systemic risk. ^{[4] [11]}

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