Michael V. Drake

Subconjunctival THC:YAG Laser Thermal Scierostomy

A THC:YAG laser (thulium, holmium, chromium-doped YAG crystal) was used to create thermal sclerostomies in 21 glaucomatous eyes of 19 patients. The laser is a long-pulsed (300 microsec), compact, self-contained, solid state laser operating in the near infrared (2.1 mu). A 1-mm conjunctival stab incision was made 12 mm away from the sclerostomy site to allow entry of a specially designed 22-gauge (712 mu) optic probe that delivers energy at a right angle to the long axis of the fiber. Probe insertion produced minimal disturbance of the conjunctiva. Pulse energies of 80 mJ to 120 mJ were used with a repetition rate of 5 pulses/second. Total energy levels to produce full-thickness sclerostomies ranged from 1.4 to 4.8 J. Subconjunctival 5-fluorouracil injections were administered in 15 eyes. At 3 months the mean intraocular pressure of successful cases (16) was 14 mmHg (range, 9 to 22 mmHg). Of successful cases, the mean intraocular pressure at 6 months was 13 mmHg (range, 2 to 22 mmHg). Five cases failed within the initial 3 months, and 3 additional cases failed by 6 months. The authors conclude that this full-thickness sclerostomy technique may simplify filtering surgery without anterior chamber instrumentation and with minimal conjunctival trauma.

Self-injected retinal emboli.

Twelve patients with bilateral intraretinal talc emboli were examined. Each patient had self-injected large doses of methylphenidate (Ritalin) for one or more years. All fundi showed yellow-white particles in the macular area, and two eyes had reduced vision secondary to retinal vascular occlusion. The clinical syndrome, ophthalmoscopic appearance, and fluorescein angiographic findings of self-injected retinal emboli are presented, and the pathogenesis is discussed.

Subconjunctival THC: YAG Laser Limbal Sclerostomy Ab Externo in the Rabbit

A chromium-sensitized, and thulium and holmium-doped YAG laser (THC:YAG laser) was used to create bilateral limbal sclerostomies in six Dutch pigmented rabbits. The laser is a long-pulsed (300 microseconds) [corrected], compact, self-contained, solid-state laser operating in the near infrared (2.1 microns). A 1-mm conjunctival stab incision was made 12 mm away from the sclerostomy site to allow entry of a specially designed 26-gauge (480 microns) optic probe that delivers energy at right angles to the long axis of the fiber. Probe insertion minimally disturbed the conjunctiva. Pulse energies of 60 to 150 mJ were used with a repetition rate of 5 pulses/s. Energy levels ranging from 1.35 to 6.6 J produced full-thickness sclerostomies. Histopathology showed a sharply defined perforating limbal wound at all energy levels. The overlying conjunctiva was intact, with swelling of the adjacent cornea. A peripheral iridectomy was intentionally created with the laser through the peripheral limbus, resulting in a sharply defined perforating tract through the iris/ciliary body. This technique may simplify filtering sclerostomy surgery, without anterior chamber instrumentation and with minimal conjunctival trauma.

Neodymium: YAG laser iridotomy

During the past several years the Neodymium:YAG laser has become increasingly popular for performing peripheral iridotomy. Using energy levels of 2-8 millijoules per shot and 1-3 shots per treatment, most irides can be penetrated in one sitting. Nd:YAG laser iridotomies show very little tendency to close, except in patients with active intraocular inflammation. A small amount of hemorrhage is common following YAG laser iridotomy, but clinically significant hyphema is rare. Significant lenticular or corneal damage is extremely rare. Although longterm follow-up of large numbers of patients is lacking, Nd:YAG laser iridotomy appears to be a safe and effective alternative to Argon laser iridotomy in selected patients.

Filtering Seton Implant for Glaucoma: Initial Animal Trial

A newly developed silicone filtering seton device was implanted in each of five eyes of four rhesus monkeys after they had undergone extensive argon-laser trabeculoplasty to raise their intraocular pressure (IOP). One animal (one implant eye) was killed at 6 weeks. The other three animals (four implant eyes) were observed for 17 to 24 months following implantation surgery. Mild to moderate postoperative inflammation subsided during the first postoperative week. The eyes remained quiet throughout the remainder of follow up. The postoperative IOPs varied between 18% and 70% of the IOPs at the time of implant surgery. In the three monkeys that had unilateral surgery, the IOP at the final follow-up measurement was equal to or lower than the IOP in the unoperated fellow eye. In the monkey that had bilateral surgery, both of the final IOPs were lower than the preoperative ones.

Subconjunctival THC:YAG (holmium) laser thermal sclerostomy ab externo

A THC:YAG laser (thulium, holmium, chromium-doped YAG crystal) was used to create thermal sclerostomies in 35 glaucomatous eyes of 33 patients. The laser is a long-pulsed (300 microsecond(s) ec), compact, self-contained, solid state laser operating in the near infrared (2.1 (mu) ). A 1 mm conjunctival stab incision was made 12 mm away from the sclerostomy site to allow entry of a specially designed 22-gauge (712 (mu) ) optic probe that delivers energy at a right angle to the long axis of the fiber. Probe insertion produced minimal disturbance of the conjunctiva. Pulse energies of 80 mJ to 120 mJ were used with a repetition rate of 5 pulses/sec. Total energy levels to produce full-thickness sclerostomies ranged from 1.4 to 7.2 J. Subconjunctival 5-fluorouracil injections were administered in 32 eyes. Success rate was 66% at 6 months and 63% at 12 months. Mean intraocular pressure of successful cases was 14 mmHg at 6 months and 13 mmHg at 12 months. Ten cases failed within the initial six months, and one additional case failed by 12 months. Success and failure were analyzed relative to patient risk factors and clinical experience with the procedure.

A new contact neodymium:YAG laser for cyclophotocoagulation.

A newly developed compact (40 kg), self-contained contact Neodymium:YAG laser produces high-peak, high-energy (800 mJ/pulse), short (1.0 millisecond) pulses with 1 to 3 pulses/exposure. Energy is delivered via a 320-microns cleaved quartz fiber optic probe. Cyclophotocoagulation was performed in five eyes of three medium-sized Dutch-pigmented rabbits. The eyes received exposures of 1 to 3 pulses/exposure. Energy delivered ranged from 100 to 800 mJ/pulse. Histopathology revealed ciliary body disruption and hemorrhage with no damage to overlying sclera. When used for transscleral cyclodiathermy in the rabbit, the laser created significant ciliary body disruption with minimal scleral injury.