JRSBRT 10.3, p. 233-239 (PDF)

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A technical guide to Gamma Knife radiosurgery for ophthalmic lesions
Ereena Alfian, Niki Ho Wai Wye, Mae-Lynn Catherine Bastion, Othmaliza Othman, Farizal Fadzil, Jegan Thanabalan, Marfuah Nik Eezamuddeen, Fuad Ismail, Shahizon Azura Mohamed Mukari, Siti Khadijah Hamsan and Ramesh Kumar

Background: Gamma Knife radiosurgery (GKRS) is a minimally invasive technique for treating ophthalmic lesions, offering precision that minimizes damage to surrounding tissues. This paper describes a single-center experience using GKRS for ophthalmic lesions, focusing on the technical aspects.

Methods: The technical guide involved pre-treatment imaging, eye fixation, stereotactic frame placement, and treatment planning. Ophthalmologists performed peribulbar regional sub-tenon anesthesia (0.5% bupivacaine and 2% lignocaine), globe immobilization (via suturing of recti muscles and applying retinal bands), and temporary tarsorrhaphy in the operating theatre to secure the affected eye in position. The stereotactic frame was placed under local anesthesia and angled to center the lesion. Plastic cover filled with tissue-equivalent gel was then placed. Fat-suppressed magnetic resonance imaging (MRI) and Gamma Plan software (Version 11.1) were used for planning.

Results: Six patients were treated using the described technique. Diagnoses included optic nerve sheath meningioma, uveal melanoma, orbital metastases, and sebaceous carcinoma involving the eyelid. Prescription dose range of 15 to 25 Gy with a 50% isodose, selected based on lesion type, volume, and proximity to optic apparatus. All patients successfully completed treatment without frame-related complications, treatment interruptions, or technical failures. At a median follow-up of 11.5 months, radiological tumor control was observed in all cases with no reported acute vision-threatening complications.

Conclusions: GKRS is a minimally invasive alternative to traditional surgery for the management of ophthalmic lesions. With proper planning, optimized dosimetry, and diligent follow-up, favorable clinical outcomes can be achieved with minimal risks. This paper provides practical insights for clinicians seeking to adopt GKRS techniques in treating ophthalmic lesions.

Keywords: orbital neoplasms; Gamma Knife radiosurgery; stereotactic radiosurgery; ocular fixation