Strabismus

Definition

Strabismus in oncology refers to misalignment of the eyes occurring in cancer patients due to tumor involvement, treatment complications, or paraneoplastic syndromes.

Causes in Oncology

1. Orbital or CNS Tumors
   • Tumors near cranial nerves (III, IV, VI) controlling eye muscles.
   • Common in neuroblastoma, medulloblastoma, retinoblastoma, or orbital metastases.
2. Paraneoplastic Syndromes
   • Autoimmune responses can affect extraocular muscles or neuromuscular junctions.
   • Rare, but possible with small cell lung cancer and others.
3. Treatment-Related Causes
   • Radiotherapy: Cranial irradiation can damage cranial nerves controlling ocular movement.
   • Chemotherapy / Immunotherapy: Rare neurotoxic side effects (e.g., vincristine can cause neuropathies affecting eye muscles).
   • Surgical trauma: Postoperative cranial nerve injury.
4. Metastasis
   • Orbital metastases from breast, lung, or melanoma can present as strabismus due to mass effect.

Clinical Features

• Misalignment of one or both eyes (inward, outward, upward, downward).
• Diplopia (double vision), especially in older children or adults.
• Eye pain or proptosis if mass lesion present.
• Possible ptosis or restricted eye movements.

Investigation

• Ophthalmologic exam: Cover/uncover test, ocular motility assessment.
• Neuroimaging: MRI or CT of the brain and orbit to evaluate tumor involvement or cranial nerve compression.
• Laboratory: Paraneoplastic antibody panels if autoimmune etiology suspected.

Management

1. Treat underlying malignancy
   • Surgical resection, radiotherapy, or systemic chemotherapy depending on tumor type.
2. Symptomatic management
   • Prism lenses, patching, or eye exercises for diplopia.
   • Botulinum toxin injection in selected cases.
3. Supportive care
   • Ophthalmology referral for monitoring visual function and preventing amblyopia in pediatric patients.

Pharmacist’s Role

• Monitor for drug-induced neuropathies (e.g., vincristine, cisplatin).
• Educate patients on recognizing visual changes promptly.
• Coordinate with oncology and ophthalmology teams for early intervention to prevent permanent visual impairment.