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BACKGROUND: The holmium:YAG laser shrinks stromal collagen and changes corneal refractive power, reportedly without recurrent or persistent epithelial defects, stromal necrosis, or damage to the epithelium and endothelium observed with some other thermokeratoplasty techniques. METHODS: We studied the safety of the holmium:YAG laser using various patterns and energy densities after treating 12 poorly sighted eyes, two immediately prior to corneal transplantation and 10 followed for a mean period of 90 days (range, 60 to 180 days). Visual acuity, intraocular pressure and inflammation, central corneal endothelial cell density and thickness, and intraocular structures of the eye were indices evaluated regularly. Patients were also assessed for specific symptoms during the post-operative period. RESULTS: There were no problems with epithelial healing and no stromal necrosis or evidence of endothelial damage; no significant differences were noted in any of the endothelial cell indices examined. A mean change in corneal curvature of 1.10 diopter (D) was achieved, but varying amounts of regression of this effect was noted. CONCLUSIONS: Holmium:YAG laser thermal keratoplasty appears to be safe over a follow up of up to 180 days. Corneal refractive changes on the order of 1.05 D can be achieved using the parameters employed in this study. Whether or not larger, persistent corneal refractive change can be achieved with a holmium:YAG laser remains to be determined. [J Refract Surg. 1995,11:358-365.]

The eradication of Trichophyton rubrum has been attempted via laser irradiation because it could result advantageous relative to current clinical therapies. Anticipating that the necessary thermal effects could unintentionally damage the underlying toe dermal layer, we have explored two auxiliary approaches: (a) laser irradiation under vacuum pressure, with and without water dousing and, (b) cooling followed by laser heating (thermal shock). The rationale is that at low pressures, the temperature necessary to achieve water evaporation/boiling is significantly reduced, thus requiring lower fluences. Similarly, a thermal shock induced by cooling followed by laser irradiation may require lower fluences to achieve fungus necrosis. For all experiments presented we use a Cooltouch, model CT3 plus, 1320 nm laser to irradiate fungi colonies. The vacuum pressure experiments exposed fungi colonies to a subatmospheric pressure of 84.7 kPa (25 inHg) with and without water dousing for 5 min, followed by irradiation with 4.0 J/cm2 fluence and 40-90 J total energies. The thermal shock experiments consisted of three sections at 4.8 J/cm2: cooling the fungus to 0 °C at 0.39 °C/min and then irradiating to 45-60 °C; cooling to -20 °C at 1.075 °C/min and irradiating to 45 °C; and cooling to -20 °C at 21.5 °C/min and irradiating to 45 °C. Fungus growth rate over a 1-week period assessed the feasibility of these procedures. Results indicated both approaches hamper the growth rate of fungi colonies relative to untreated control samples, especially water dousing under vacuum conditions and slow cooling rate preceding irradiation for thermal shock effect.

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 µsec), compact, self-contained, solid state laser operating in the near infrared (2.1 µ). A 1-mm conjunctiva) stab incision was made 12 mm away from the sclerostomy site to allow entry of a specially designed 22-gauge (712 µ) 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 conjunctiva) trauma.

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- µm 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.

We present our research into a pulsed xenon lamp source for the treatment of psoriasis and other skin disorders. Various filtering techniques, lamp configurations, power supply configurations and delivery systems are discussed. Comparisons are made to existing treatment modalities. Cryogen cooling of the treatment site is discussed.

Chromium-sensitized and thulium- and holmiumdoped 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 urn). 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.

The purpose of this study is to evaluate the safety and effectiveness of the New Star Model 130 neodymium:yttrium aluminum garnet (Nd:YAG) laser system for nonablative laser treatment of facial rhytides (e.g., periorbital wrinkles). Facial rhytides are treated with 1.32 micrometer wavelength laser light delivered through a fiberoptic handpiece into a 5 mm diameter spot using three 300 microsecond duration pulses at 100 Hz pulse repetition frequency and pulse radiant exposures extending up to 12 J/cm2. Dynamic cooling is used to cool the epidermis selectively prior to laser treatment; animal histology experiments confirm that dynamic cooling combined with nonablative laser heating protects the epidermis and selectively injures the dermis. In the human clinical study, immediately post-treatment, treated sites exhibit mild erythema and, in a few cases, edema or small blisters. There are no long-term complications such as marked dyspigmentation and persistent erythema that are commonly observed following ablative laser skin resurfacing. Preliminary results indicate that the severity of facial rhytides has been reduced, but long-term follow-up examinations are needed to quantify the reduction. The mechanism of action of this nonablative laser treatment modality may involve dermal wound healing that leads to long- term synthesis of new collagen and extracellular matrix material. ©2005 Copyright SPIE - The International Society for Optical Engineering.

Nonablative skin resurfacing is a dermatologic procedure utilizing pulsed laser irradiation and dynamic cooling to induce selectively a wound healing response in the papillary and upper reticular dermis. Using temperature measurements of human skin provided by pulsed photothermal radiometry immediately following laser irradiation (lambda equals 1.32 micrometer), spatial distribution of thermal damage is predicted in response to various potential therapeutic laser- cryogen doses. Results of our analysis suggest that appropriate application of pulsed laser irradiation and cryogen spray cooling may be used to protect the epidermis and selectively confine thermal injury to the papillary and upper reticular dermis. Development of nonablative skin resurfacing will require understanding the relationship between the degree of dermal photocoagulation and the cutaneous wound healing response following laser irradiation. ©2005 Copyright SPIE - The International Society for Optical Engineering.

The THC:YAG laser was used to create 93 thermal sclerostomies ab externo in 81 glaucomatous eyes of 76 patients. This holmium laser is a long-pulsed, compact, self-contained, solid-state laser operating in the near infrared. A 1-mm conjunctival stab incision was made 5-15 mm from the sclerostomy site to allow entry of a specially designed 22-gauge optic probe that delivers energy at a right angle to the long axis of the fiber. Pulse energies of 80 mJ to 120 mJ were used with a repetition rate of 5 pulses per second. Total energy levels to produce full-thickness sclerostomies ranged from 1.4 to 7.2 J. Seventy-eight eyes received the antimetabolite 5-fluorouracil. Success was defined as postoperative intraocular pressure 30% reduction in intraocular pressure if preoperative pressure was

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 µm diameter, with either cleaved or 500 µm 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 µm 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 µm 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.

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.