Lowering the intraocular pressure (IOP) is the only treatment modality for the management of glaucoma patients, aiming to arrest the irreversible visual field loss. Surgical treatment is usually indicated when the IOP is insufficiently lowered and/or glaucomatous optic neuropathy worsens and visual field defect progresses despite laser Trabeculoplasty or maximally tolerated medical therapy.
CLASS (CO2 Laser Assisted Sclerectomy Surgery) procedure is similar to trabeculectomy, the major difference being that after the scleral flap is raised, the remaining sclera over the Schelm’s canal and trabecular meshwork is dissected by the CO2 laser probe until aqueous percolated over the entire dissected bed. The aqueous originated from the unroofed Schlemm’s canal and juxta-canalicular trabeculum and the dissection stops automatically by the aqueous in the bed and penetration in the AC is avoided. This way the procedure aimed to prevent intra ocular complications.
The procedure is performed under sub-conjunctival anesthesia. The perilimbal conjunctiva and tenon capsule are dissected. A half-thickness superior fornix-based scleral flap is fashioned with a crescent knife. A red laser aiming beam is used to mark the scanning area boundaries. Scan dimensions (width and length) can be changed within the range of 1 to 4 mm. Initially a wide scan area is used to repeatedly remove layers of sclera until a percolation zone can be readily identified. The CO2 laser is repeatedly applied with time intervals of 2 to 3 seconds between applications to allow percolation to take place and be detected, until sufficient percolation zone of at least 3 mm in region length is clearly evident. The scleral flap is then repositioned and sutured with 10-0 nylon sutures.