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
- Orbital or CNS Tumors
- Tumors near cranial nerves (III, IV, VI) controlling eye muscles.
- Common in neuroblastoma, medulloblastoma, retinoblastoma, or orbital metastases.
- Paraneoplastic Syndromes
- Autoimmune responses can affect extraocular muscles or neuromuscular junctions.
- Rare, but possible with small cell lung cancer and others.
- 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.
- 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
- Treat underlying malignancy
- Surgical resection, radiotherapy, or systemic chemotherapy depending on tumor type.
- Symptomatic management
- Prism lenses, patching, or eye exercises for diplopia.
- Botulinum toxin injection in selected cases.
- 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.