What causes brown discoloration of the eye?

Causes of Brown Discoloration of the Eye

Brown discoloration of the eye can be caused by several conditions including melanoma, pigment deposition from iris melanocytes, and drug-induced pigmentation, with the specific cause determining appropriate management and prognosis.

Primary Causes of Brown Corneal Pigmentation

• Melanoma and related conditions

  • Conjunctival melanoma can cause brown pigmentation of the eye, presenting as a painless, flat or nodular, brown lesion on the bulbar or palpebral conjunctiva 1
  • Primary acquired melanosis of the conjunctiva can lead to progressive brown corneal pigmentation 2
  • Iris melanoma can release pigment granules into the anterior chamber that are transported into the cornea through the endothelium 2

• Iris melanocyte migration

  • Iris melanocytes can migrate to the posterior corneal surface following ocular trauma or surgery, causing visible brown pigmentation 3
  • These melanocytes may acquire endothelium-like characteristics and contribute to posterior collagen layers of the cornea 3

• Pigment deposition mechanisms

  • Pigment can be transported into the cornea through the endothelium and accumulate in melanophages between corneal lamellae 2
  • The pigment may subsequently clear via the corneal limbus in a process resembling clearance of corneal hemochromatosis 2

Other Causes of Ocular Pigmentation

• Neoplastic conditions

  • Ocular surface squamous neoplasia can present with conjunctival hyperemia and nodules, sometimes with pigmentation changes 1
  • Sebaceous carcinoma may exhibit yellowish discoloration of the tarsal plate and can be misdiagnosed as a chalazion 4

• Inflammatory and autoimmune conditions

  • Bilateral acute depigmentation of the iris (BADI) can cause symmetrical pigment loss of iris stroma, affecting primarily young women 5
  • Vasculitis conditions like sarcoidosis can cause various ocular manifestations including iris nodules and trabecular meshwork nodules 1

• Drug-induced pigmentation

  • Represents 10-20% of all cases of acquired hyperpigmentation 6
  • Main drugs implicated include NSAIDs, antimalarials, amiodarone, cytotoxic drugs, tetracyclines, heavy metals, and psychotropic drugs 6
  • Pathogenesis varies and can involve accumulation of melanin, the drug itself, synthesis of special pigments, or deposits of iron 6
  • Sun exposure often worsens drug-induced pigmentation 6

Diagnostic Approach

• Slit-lamp biomicroscopy is essential to evaluate:

  • Whether the pigmentation is unilateral or bilateral 1
  • Location and depth of pigmentation (epithelial, stromal, or endothelial) 1
  • Associated findings such as keratic precipitates, endothelial vesicles, or anterior chamber reaction 1
  • Evidence of past trauma, inflammation, or surgery 1

• Warning signs requiring urgent evaluation

  • Enlargement of a pigmented lesion, development of blood vessels, or thickening 1
  • Progressive visual loss associated with pigmentation 2
  • Recurrence of pigmented lesions in the same location, especially in elderly patients 4

Management Considerations

• For suspected melanoma or neoplastic conditions:

  • Surgical excision with histopathological evaluation is recommended 2
  • Close monitoring for recurrence or progression is essential 1

• For drug-induced pigmentation:

  • Sun avoidance and discontinuation of the offending medication 6
  • Pigmentation may fade over time but can become permanent in some cases 6
  • Laser therapy may be beneficial in certain cases 6

• For inflammatory conditions:

  • Treatment of the underlying condition may improve or resolve associated pigmentation 7
  • Topical corticosteroids or immunomodulators may be indicated for certain conditions 7

Potential Complications and Prognosis

• Melanoma can spread to other adnexal structures and metastasize, potentially threatening life 1
• Visual impairment can occur with extensive corneal pigmentation 3
• Some forms of pigmentation (like BADI) may spontaneously repigment over time 5
• Drug-induced pigmentation may persist for a long time even after discontinuation of the causative agent 6