Automation in krypton laser photocoagulation.

Histologic study of lesions produced by krypton red (647.1 nm) and krypton yellow (568.2 nm) laser lights reported here suggests advantages in alternating these two wavelengths in photocoagulation. Selection of the best wavelength to be used in a given location on the retina should result from pre-determined absorbance conditions in that location. The feasibility of the relative measurement of absorbance in different fundus locations by measurement of the relative reflectance is discussed. Instrumentation for these measurements and for switching from one wavelength to the other is described. Instrumentation for the possible expansion of krypton laser applications to clinical problems in the anterior segment also is suggested.

Astigmatism of oblique incidence in the human model eye.

Two cylindrical lenses of equal power, one positive and one negative, were used to correct astigmatism of oblique incidence in a wide-angle optical model of the human eye. Tangential and sagittal vergences were calculated at different visual angles from the posterior pole to the peripheral retina. The positive cylinder was placed with its axis parallel to the tangential meridian while the negative cylinder was placed with its axis parallel to the sagittal meridian. Improvement in the quality of the retinal image at different angles of incidence was obtained by varying the angle between the axes of the correcting cylinders. Corresponding gains in resolution have been calculated and confirmed by peripheral fundus photography.

Transtympanic endoscopy of the middle ear.

Modern optical technology has made available fiberoptic and rigid endoscopes with diameters of 2 mm and less with acceptable resolution. Endoscopes of small caliber were introduced through a strategically placed myringotomy or an existing perforation to perform exploration of the middle ear as an in-the-office procedure. This technique is now routinely used as an adjunct in the diagnostic evaluation of patients with suspected middle ear conditions. Exploratory surgery of the middle ear may be avoided or definitive procedures may be planned better based on endoscopic findings.

Endoscopic diode laser welding of mucosal grafts on the larynx: a new technique.

Epithelial coverage of a laryngotracheal wound is an important factor in preventing stenosis, and endoscopic transplantation of a free mucosal graft without stents or sutures would be a significant therapeutic advance. In vitro and in vivo canine studies were performed to explore the feasibility of transplantation with a low-power diode laser (400 mW) enhanced by indocyanine green dye-doped albumin. The tensile strength of graft adherence in 10 cadaver larynges was strong (35.25 +/- 10.39 g). Survival studies in live canine models with a specially designed endoscopic instrument set showed excellent healing at 6, 14, and 28 days. Healing was documented with photography and by histologic examination. Successful endoscopic transplantation of a free mucosal graft should improve results of treatment for laryngotracheal stenosis and laryngeal reconstructive surgery.

Tracheal anastomosis with the diode laser and fibrin tissue adhesive: an in vitro and in vivo investigation.

Absorbable sutures have been advocated for tracheal anastomosis to reduce fibrosis and foreign body reaction leading to recurrent stenosis. Fibrin tissue adhesive (FTA) and diode laser welding with indocyanine green-dyed fibrinogen were evaluated in tracheal anastomosis to reduce the number of sutures and to improve healing. In vitro studies demonstrated strong anastomoses with a combination of laser welding and FTA with minimal tissue damage. In a controlled in vivo study, circumferential resections of canine tracheas were repaired with laser welding and FTA augmented with a few stay sutures. These anastomoses had less fibrosis and tissue damage than anastomoses in control animals repaired with sutures alone. This study supports investigation of laser welding and FTA in human beings for tracheal anastomosis and other procedures in which suturing may be difficult.

Sinus surgery: does mitomycin C reduce stenosis?

This experimental study investigates the effect of mitomycin C (MMC) on sinus mucosal healing. MMC has an antiproliferative action on fibroblasts. It is used in glaucoma surgery to prevent restenosis of fistulas. Antrostomies were drilled in rabbit maxillary sinuses. One side was used as a control and the other treated with MMC at a concentration of 0.04, 0.4, or 1 mg/mL. Two animals from each group were sacrificed at 1, 2, 4, and 12 weeks. The antrostomies in the control and 0.04-mg/mL groups had closed by 1 week; in the 0.4-mg/mL group by 4 weeks, and in the 1.0-mg/mL group by 12 weeks. Ciliary function was initially impaired but normalized within 1 week. Both light and scanning electron microscopy showed no permanent damage to the cilia. These results suggest that MMC can be used to delay closure of antrostomies in sinus surgery.

A combined endoscopic Co2 laser and external approach for treatment of glottic cancer involving the anterior commissure: an animal study.

Endoscopic laser resection usually has been discouraged for anterior commissure (AC) carcinoma because of inadequate exposure and close proximity to underlying cartilage. A new technique combining endoscopic CO2 laser incision and an external approach, creating a window in the thyroid cartilage, was tested in this in vivo study of six dogs. An en bloc specimen including adjacent cartilage was excised while preserving the thyroid framework. The glottic reconstruction was accomplished with external placement of a sternohyoid muscle flap, by either using a bipedicled muscle flap with overlying skin or a unipedicled muscle flap with a graft of free mucosa. The results showed a satisfactory anatomic reconstruction and acceptable functions. The bipedicled muscle flap was superior to the unipedicled muscle flap due to a better AC reconstruction. It is believed that this new combined technique may overcome limited access with endoscopic technique and excessive cartilage resection with the external partial laryngectomy.

Holmium: yttrium aluminum garnet laser-assisted endoscopic sinus surgery: laboratory experience.

Endoscopic sinus surgery has gained wide acceptance since its introduction into the United States. Complex sinus anatomy and troublesome bleeding have been associated with complications, which vary in severity from synechia to blindness and leakage of cerebrospinal fluid. Endoscopic sinus surgery using a holmium: yttrium aluminum garnet pulsed solid-state laser oscillating at 2.1 microns with fiberoptic delivery was performed in the laboratory, and the results were compared with those of conventional endoscopic sinus surgery. Three beagle dogs, six human cadaver heads, and one calf head were used in the in vivo and in vitro studies to evaluate the bone ablation, tissue coagulation, and hemostatic properties of the holmium: yttrium aluminum garnet laser. Modified endoscopic telescopes for sinus surgery, a newly developed handpiece for fiberoptic delivery, and other surgical instruments were used. The results indicate that the holmium: yttrium aluminum garnet laser and new delivery instrumentation provide good hemostasis and controlled soft-tissue ablation and bone removal. The access to all sinuses in the human cadaver model was very good. The canine in vivo study showed delayed but complete healing on the laser-treated side. Clinical evaluation of the holmium: yttrium aluminum garnet laser is warranted to increase the precision and safety of endoscopic sinus surgery.

Erbium laser in middle ear surgery: in vitro and in vivo animal study.

Cadaveric human temporal bones, cadaveric rabbits, and live rats were used to demonstrate the utility and safety of the erbium:yttrium-scandium-gallium-garnet (Er:YSGG) laser for otologic applications. The shallow penetration in water of this wave-length and its ability to ablate bony tissue with minimal collateral thermal effects spare underlying and adjacent structures and make it appealing for stapedotomy. The authors were able to satisfactorily perform small fenestra stapedotomy, atticotomy facial nerve decompression, and mastoidectomy. Temperature measurements from the round window area during Er:YSGG stapedotomy recorded an elevation of less than 2 degrees C, which is well within acceptable limits. An acoustic shock produced at the impact site is the major disadvantage and requires further in vivo investigation of the transient and sustained deleterious effects away from the application site. This work supports further investigation into potential applications of the Er:YSGG laser in otology.

New technique for laryngotracheal mucosa transplantation. 'Stamp' welding using indocyanine green dye and albumin interaction with diode laser.

OBJECTIVE: To investigate (1) the possibility of survival of free mucosa "stamp" grafts fixed in the airway with a new technique using indocyanine green-dyed albumin solder activated with a diode laser and (2) the degree of improvement of wound healing in the airway by applying modified microskin transplantation techniques from burn surgery to cover a relatively large wound with a few small pieces of mucosa anchored in place with the previously mentioned technique. DESIGN: Three (one control and two experimental) rectangular (10 x 8 mm) wounds in tracheal mucosa were produced in four experimental animals (dogs) using a carbon dioxide laser. The control wound was left uncovered. In the first experimental wound, a mucosal flap was raised and then fixed in place by a trapdoor flap method. In the second experimental wound, two small (each 2 x 3 mm) autogenous mucosa grafts were anchored onto the surface with indocyanine green-dyed albumin activated with an 810-nm diode laser. Histomorphologically, the postoperative results from three wounds were compared. RESULTS: The experimental wounds were completely covered by regenerated squamous cells in 1 week and by ciliated epithelium in 2 weeks after the operation despite the discrepancy in size of the graft to wound area (1:6.7) covered with the stamp mucosa. No thermal damage from the diode laser was noted in the second experimental wounds. In the control wounds, no coverage was observed at 1 week, and only squamous cells were noted 2 weeks postoperatively. All the wounds had normal ciliated epithelium coverage at 4 weeks. CONCLUSIONS: Transplanted stamp grafts provided similar or better healing than trapdoor flap transplants. This new technique made endoscopic mucosal grafting possible and offers a potential breakthrough in the management of laryngotracheal stenosis.

The holmium:YAG laser-assisted otolaryngologic procedures.

OBJECTIVE: To determine the effectiveness of the holmium: YAG (Ho:YAG) laser in otolaryngologic procedures that necessitate the ablation of osseous and soft tissue. DESIGN: Case series. SETTING: Lahey Clinic, Burlington, Mass. PATIENTS: Consecutive series of 37 patients; 29 with chronic sinusitis, five with chronic dacryocystitis, one with recurrent choanal stenosis, one with tracheopathia osteoplastica, and one with a sphenoid sinus mucocele. INTERVENTION: The Ho:YAG laser was used to assist in 37 procedures, including endoscopic sinus surgery, dacryocystorhinostomy, treatment of choanal stenosis, ablation of obstructive tracheopathia osteoplastica, and removal of a sphenoid sinus mucocele. MAIN OUTCOME MEASURES: Postsurgical success and complications, satisfaction of the patients, and the ability of the laser to remove tissue. RESULTS: Complications occurred in eight patients: intranasal or ethmoid scarring (four), persistent polyps (one), bleeding (one), stent dislodgment (one), and tracheitis (one). Three patients required revision surgery. None of the complications were related to use of the laser, although the laser may produce increased scarring. The laser was effective for osseous and soft-tissue ablation, but its usefulness was limited for hemostasis. CONCLUSIONS: The Ho:YAG laser can be used in otolaryngologic procedures when surgical access is difficult or when controlled, precise ablation of osseous tissue is necessary.

Mucosal intact laser tonsillar ablation.

BACKGROUND: A laser technique has been developed in the laboratory using a noncontact 810-nm diode laser. RESULTS: Mucosal intact laser tonsillar ablation (MILTA) coagulates tonsillar lymphoid tissue while preserving the overlying mucosa. A canine model was used to evaluate this new method. The canine tonsils were exposed to laser energy for 5 to 6 minutes each at 8 to 10 W of power. This technique was compared with standard "cold" knife tonsillectomy. The dogs were observed carefully during the postoperative period. When comparing parameters such as onset of eating solid food, amount of food ingested per day, onset of normal activity, and degree of weight loss, MILTA showed significant benefit over the standard technique. The operative sites were evaluated and compared at 1.5 hours and at 7, 21, and 45 days after treatment. CONCLUSIONS: None of the tonsils treated by MILTA showed mucosal ulceration. At the end of 45 days, histopathological examination showed complete absence of tonsillar tissue with normal mucosa in both the MILTA and standard groups. Traditional tonsillectomy techniques are associated with moderate morbidity and the potential for serious hemorrhage. With the preservation of the overlying mucosa, the possible clinical advantages of this approach to tonsillectomy are the absence of bleeding, avoidance of general anesthesia in older patients, less operating time, and decreased postoperative morbidity. The potential for office treatment exists. Additional laboratory studies, as well as careful clinical trials, are indicated based on these encouraging results.

New visualization techniques for in utero surgery: amnioscopy with a three-dimensional head-mounted display and a computer-controlled endoscope.

Endoscopic fetal surgery may reduce preterm labor associated with open hysterotomy but is partially limited by current visualization technology. We investigated a three-dimensional (3D) imaging system coupled to a head-mounted display (3D-HMD) and also employed a computer-controlled zoom endoscope for noninsufflated amnioscopy. Pregnant sheep were prepared in aseptic fashion for general anesthesia. Uterine access was obtained following maternal laparoscopy. A 10-mm zoom endoscope (Vista Medical Technologies, Carlsbad, CA) was used to examine the fetus and uterine contents. Fetal limbs were exteriorized for microsurgery. A new system (Vista Medical Technologies) was attached to an operative microscope, permitting projection of a 3D image via an HMD. The fetus and umbilical cord were inspected using the zoom endoscope, which changes the depth of focus under computer control. Basic manipulations of the fetus and cord were easily completed. Real-time 3D fetal imaging was accomplished. The added depth perception enabled detailed fetal and placental examination, fostering manipulation of the fetus and cord. The HMD was adjusted to fit several surgeons, permitting a natural operative posture. This unit has the capacity to display any video, CT, MR, or ultrasound image as a picture-in-picture. The success of minimally invasive fetal surgery is in part dependent on the development of video technologies capable of providing both magnification and optimal resolution. The zoom endoscope affords excellent visibility of multiple surgical targets without instrument repositioning. A 3D HMD system such as this provides greater anatomic detail and an appreciation of fetal movements that may make intrauterine procedures more feasible.

Autologous fibrin tissue adhesive in endoscopic sinus surgery.

Endoscopic sinus surgery may be complicated by bleeding, formation of synechia, and infection. This study investigated the application of autologous fibrin tissue adhesive during endoscopic sinus surgery in an attempt to avoid packing, to decrease complications, and to improve healing. Fibrin tissue adhesive from pooled human blood is a hemostatic and bacteriostatic agent. Autologous fibrin tissue adhesive avoids the potential infectious and immunologic risks of the pooled blood product. Twelve patients undergoing bilateral endoscopic sinus surgery participated in the study. Phlebotomy and preparation of the adhesive were performed during the procedure. Fibrin tissue adhesive was applied to only one side, with the contralateral side used as a control. Bacitracin ointment was applied to the adhesive-treated side, and packing coated with bacitracin was placed on the contralateral side. Patients were observed for a minimum of 3 months, and results were documented with photographic and video recordings. A uniformly high degree of patient satisfaction was achieved because of the elimination of packing and a sensation of increased nasal airway patency on the fibrin-treated side. Fibrin tissue adhesive provided hemostasis, decreased crusting, accelerated mucosal healing, and diminished synechia. Autologous fibrin tissue adhesive is beneficial in endoscopic sinus surgery, and its application should be considered, especially when the risk of hemorrhage or synechia is increased.

Does slow-release 5-fluorouracil and triamcinolone reduce subglottic stenosis?

The surgical management of subglottic stenosis may be complicated by reformation of strictures. A slow-release combination of 5-fluorouracil, which has an antiproliferative effect on fibroblasts, and the corticosteroid triamcinolone acetonide has been used experimentally to control scar production in ophthalmic operations. This study was performed to determine if this material also can be used to reduce formation of subglottic stenosis. Subglottic stenosis was induced in rabbits by means of injury to the subglottic mucosa and submucosa. A suspension of the compound at a concentration of 2.5 mg/ml or 12.5 mg/ml was injected into the adjacent soft tissues. A control group of rabbits received the same volume of the suspension fluid but no compound. Two rabbits from each group were killed 1, 2, and 12 weeks postoperatively. No stenosis was seen at 1 or 2 weeks, but at 12 weeks the rate of formation of subglottic stenosis was decreased to a mean of 15.20% in the experimental groups compared with 47.37% in the control group. There were no indications of local or systemic toxicity. The promising results from this preliminary study suggest that use of this compound may reduce restenosis among patients treated surgically for subglottic stenosis. Further studies are being conducted.

Endoscopic laser-assisted reshaping of collapsed tracheal cartilage: a laboratory study.

Repair of anterior tracheal wall collapse is a common and troublesome problem encountered by the head and neck surgeon. The standard treatment calls for an open procedure with or without stenting, depending on the extent of the damage. To avoid the morbidity of the open procedure, a new concept of endoscopic cartilage reshaping was investigated in a laboratory animal study. It involved the application of 1.44-micron pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) laser at relatively low power to restructure without devitalizing cartilage. An in vivo study was done in six dogs to determine appropriate laser dosimetry in a model of tracheal wall collapse created by a tracheotomy. The deformed cartilage was treated endoscopically with a noncontact 1.44-micron Nd:YAG laser, at 2 to 4 W of power with a repetition rate of 20 Hz, in three animals. As a control, three animals had endoscopic cartilage incisions followed by stent placement. Six weeks postoperatively, both groups had an adequate airway lined by healthy mucosa. In the animals with stenting, however, there was stenosis formation due to scarring at both ends of the stent, with significant inflammatory response in the local area. This study shows that it is possible to use low-power laser energy to reshape cartilage without destroying its viability, and to restore the tracheal wall to a normal contour without ablation or vaporization. The reshaped cartilage will tend to retain its shape with functional elastic force, as seen in in vitro studies. These preliminary results are encouraging, and it seems reasonable to consider using the technique in selected clinical cases as an alternative to conventional open surgery.

Resurfacing of a large laryngeal wound with mucosa grafting: a combined technique using endoscopic suture and laser soldering.

Resurfacing of a large laryngeal wound has traditionally been accomplished via an open approach--transplanting free mucosa either onto the wound directly or upon a stent. This study proposes a new approach for wound resurfacing that combines endoscopic suturing with a laser welding technique. By means of a carbon dioxide (CO2) laser, a large (20 x 25 mm) defect in laryngeal mucosa involving the glottic and subglottic area was created in five dogs. Two of the animals served as controls and received no further treatment. In the remaining three animals the wound was resurfaced with buccal mucosal grafts fixed in place by standard suture placement and a technique of CO2 laser-assisted tissue soldering. The accessible edges of the graft were soldered endoscopically with human albumin-based tissue adhesive "activated" by low power (0.8 to 1.0 W) of a CO2 laser. All animals were examined endoscopically 1 week after surgery and sacrificed painlessly 4 weeks after surgery. The treated animals showed a viable mucosal graft with improved wound healing and voice function compared to that of the control animals. This new approach combines suture fixation of the inferior aspect of the mucosal graft, an area not well exposed endoscopically, and endoscopic laser soldering techniques for the repair of large laryngeal wounds.

"Window" laryngoplasty: a new combined laser endoscopic and open technique for conservation surgery.

Endoscopic laser resection of early laryngeal carcinoma is an increasingly used treatment modality; however, the limited exposure achieved and the alteration of vocal function are still major problems. A new surgical procedure, "window" laryngoplasty, has been devised and tested in an in vivo study in 6 canines with 50 days' survival. The right vocal cord was incised endoscopically with the carbon dioxide laser, and the en bloc specimen with adjacent thyroid cartilage was removed through a window approach made in the thyroid cartilage. A sternohyoid muscle flap based superiorly was inserted into the cartilaginous window to reconstruct a pseudocord with coverage of either mucosa or fascia. A diode laser soldering technique was used to secure the mucosal graft in place. Epithelial transplantation can be accomplished externally with precise endoscopic guidance for reliable placement of the pseudocord. The results show that the new technique, a combination of endoscopic and open approaches, may be a better treatment choice than standard vertical partial laryngectomy in selected patients. Advantages of this technique include adequate en bloc resection, including adjacent cartilage for pathologic evaluation, preservation of the integrity of most of the laryngeal framework, avoidance of tracheotomy, and better functional results.

Brain tissue response to Holmium:YAG laser irradiation.

OBJECTIVE: To evaluate the usefulness of pulsed infrared solid-state Holmium:Yttrium-Aluminum-Garnet (Ho:YAG) laser in neurosurgery, acute responses of brain tissue to Ho:YAG irradiation and to investigate the healing processes in rats and rabbits. METHODS: Animals were divided into groups according to different survival time and laser irradiation mode. Craniotomy was made and laser energy was delivered to the brain surface by two irradiation modes: 1) contact mode with the fiber in contact with the brain surface; and 2) non-contact mode with the fiber tip 5 mm above the brain surface. Gross observations were made and histological changes were studied. RESULTS: Acute responses were studied on rats' brain. The contact mode produced a crater lined with less than 1 mm thick thermally coagulated layer of brain tissue. The non-contact mode effectively vaporized the brain tissue even with water irrigation. Good homeostatic effect was achieved. The shock waves generated by the pulsed delivery of laser energy, however, impacted on the brain resulting in debris spreading and brain vibration. The healing processes were studied on rabbits' brain one day to six weeks after irradiation. The lesions produced by the contact mode were narrow and sharply defined. With the non-contact mode, the thickness of the coagulated layer at the bottom of the crater varied between 0.8 and 1.1 mm. CONCLUSIONS: Ho:YAG laser should be a clinically useful tool in neurosurgery because of its good ablation effect, shallow penetration and convenient optic fiber transmission system. Meanwhile, a continuously waved Ho:YAG laser is desired to reduce the shock wave impact.

[A universal laser for intraocular treatment]. / Laser universel pour traitement intraoculaire.

The creation of a single apparatus incorporating the different lasers applicable to intraocular pathology derives from the idea of possessing the means, with one device, of objectively comparing the effects and parameters of various lasers in order to pursue a more precise line of treatment. This has led to our fabrication of the universal intraocular laser. The word universal means the ability of the machine to act on each kind of intraocular tissues with all of the various infrared or other-colored radiations, as well as with different modalities. The unit is transportable. It only requires a source of electric power (110 or 220 V) and includes an independent cooling system. The Nd: YAG laser has selectable operating parameters: pulsed or continuous excitation, Q-switched or mode-locked mode, mirror or fiber optic transmission. It is used also as the basic system of the coloured module. The colour module can provide the three clinically useful radiations: green, red, yellow. The green (532 nm) is obtained by transmission of the I.R. beam brought a birefringent crystal (KTP). Red (650 nm) and yellow (575 nm) come from two incorporated dye lasers excited by the green radiation.