Transcanalicular THC:YAG dacryocystorhinostomy.

Chromium-sensitized and thulium- and holmium-doped YAG lasers (THC:YAG laser) were used to create a nasal bony ostium in the area of the lacrimal sac fossa in four fresh frozen bisected human cadaver heads. The lasers-long pulsed (300 milliseconds), compact, self-contained, and solid state--operate in the near infrared (2.1 microns). The opening was created by passing the 320-micrometer laser fiber across the canalicular system. Pulse energies of 250 to 900 mJ were used with a repetition rate of 5 to 15 pulses per second. Energy levels ranging from 1.25 to 9 W produced a full-thickness bony ostium approximately 3 to 4 mm in diameter. Silicone tubing was then threaded through the superior and inferior canaliculus system in the standard fashion. This technique may simplify conventional dacryocystorhinostomy as well as endonasal laser dacryocystorhinostomy procedures.

Subconjunctival THC:YAG laser thermal sclerostomy.

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.

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.

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.

Ab interno and ab externo filtering operations by laser contact surgery.

A new method to create filtering tracts ab interno or ab externo which may eventually prove useful in eyes with poorly controlled glaucoma is described. Fiberoptics of 200 microns diameter, with either cleaved or 500 microns ball lens tips, were coupled to the output of an argon gas laser emitting a number of radiation lines in the ultraviolet (333 to 363 nm) wavelengths. This system was used to perforate the corneoscleral limbal tissue of enucleated bovine eyes with a small number of laser applications to create a filtering fistula. Corneoscleral limbal perforation with a 200 microns cleaved fiber required 0.6 to 1.1 J total energy, delivered with a laser power of 0.5 W, or greater, for 0.1 second. With a 500 microns ball lens fiber tip a tract of nearly 0.5 mm diameter was created, requiring 5.1 to 10.4 J total energy, delivered with a laser power of 2.0 W, or greater, for at least 0.1 second. The energy required for perforation from the external surface to the anterior chamber was the same as the energy required for ab interno perforation.

Design considerations for a fluorophotometer for ocular research.

Fluorometric studies have been made with modified slit-lamp microscopes. These instruments offered considerable versatility in modifying experimental parameters, but were seldom optimized in terms of detector and illuminator apertures, filter band-pass characteristics, detection system, light-source stabilization, or optical resolution. Improper control of these parameters can result in artifacts which override useful information. A new fluorophotometer for ocular research has been designed that utilizes an optical system, which eliminates the need for a contact lens. An effort was made to optimize both the axial resolution and the minimum detectable signal. The characteristics of standard barrier filters and excitation filters were examined and compared with photomultiplier sensitivity curves. It was necessary to use double filters in order to reduce artifacts due to excitation light that was not rejected by the barrier filter. In order to optimize the signal-to-noise ratio, a photon counting detection system was used. A dark current equivalent to 3 X 10(-10) g/ml allows a useful detection range of 1 X 10(-10) g/ml.