Subretinal neovascularization developing after prophylactic argon laser photocoagulation of atrophic macular scars

Twenty-eight anemic control dogs were subjected to isolated cerebral hypoxemic (PO2,35+/-5 mm Hg) perfusion for 2 hours. All were found to have functional pulmonary impairment. Two hours later, twenty were sacrificed and found to have the bilateral anatomic complex of the respiratory distress syndrome (RDS). All those not sacrificed expired within 20 hours with progressive respiratory distress and at autopsy had the bilateral anatomic complex. Twenty-three beagles with chronic denervation (autotransplantation) of the left lung also were subjected to the 2 hour isolated cerebral arterial hypoxemic perfusion. Minimal pulmonary functional impairment was measurable in all. Ten of sixteen were long-term survivors. The six that succumbed did not appear to suffer respiratory deaths. These six, as well as seven sacrificed 2 hours after perfusion, had the anatomic complex of RDS in the normally innervated right lungs. However, the denervated left lungs were anatomically normal. These findings are offered as additional evidence that RDS has a centrineurogenic etiology. We postulate the following sequence: "shock" causes cerebral (probably hypothalamic) cellular oxygen deprivation and dysfunction; there is autonomically mediated, increased resistance of the pulmonary venules ("postcapillary sphincters"); this leads to capillary hypertension, congestion, hemorrhage, edema, surfactant inactivation, and atelectasis. Pulmonary denervation blocks this sequence and protects the lung.     

Corneal neovascularization after penetrating keratoplasty

The purpose of this study was to delineate the patient and surgical factors that contribute to the development of corneal neovascularization (CNV) after penetrating keratoplasty (PK). Thirty-six eyes of 36 patients with no antecedent CNV were enrolled in the study. Grafts were sutured to the host with 16 10-0 nylon sutures with the knots buried alternately in either the host or donor corneal stroma. Multiple perioperative factors were recorded for each patient, and at each postoperative visit systematic corneal drawings were used to follow the development of neovascularization. The stroma adjacent to each suture of each graft was given a neovascularization score based on the extent of vessel growth toward the wound interface. Univariate and multivariate analyses were performed, including generalized estimating equations logistic regression where each eye is considered a cluster of observations. Thirty-four patients without preoperative CNV or inflammation were followed prospectively for 6-9 (mean, 7) months after PK. Fourteen eyes (41%) developed some degree of CNV. Indication for keratoplasty, age, gender, phakic status, and size of donor button were not risk factors for CNV development. The most significant risk factor identified for any degree of CNV was placement of the suture knot in the host stroma (p = 0.00007), with the overall relative risk of CNV associated with these knots over 2 (95% confidence interval, 1.1-4.2). Furthermore, the mean recipient size in eyes with postoperative CNV was larger than eyes that did not develop neovascularization (p = 0.015), and active blepharitis was associated with a fivefold increase in the risk of developing CNV to the wound edge (p = 0.008). Embedding suture knots in the host stroma, active blepharitis, and a large recipient bed are significantly associated with postkeratoplasty CNV.     

Suprachoroidal effusion following argon laser trabeculoplasty

PURPOSE: This is first report of suprachoroidal effusion occurring subsequent to argon laser trabeculoplasty (ALT). METHODS: Review of the records of the patients in question. RESULTS: A 77-year-old woman with bilateral pseudophakia and primary open-angle glaucoma was treated with ALT when her visual fields deteriorated despite topical timolol therapy. Although ALT was initially performed without complication in one eye, treatment of the other eye led to a choroidal detachment. This was associated with temporary reduction in visual acuity, shallowing of the anterior chamber and hypotony. CONCLUSION: Suprachoroidal effusion appears to be another complication of ALT. In the reported case, this application and its effects were temporary and resolved with conservative management.     

Physical properties of composites cured with conventional light or argon laser

PURPOSE: To evaluate and compare diametral tensile strength (DTS), compressive strength (CS) and flexural strength (FS) of a hybrid and a microfill resin composite restorative material polymerized by an argon laser for 10 seconds (AL10) and 20 seconds (AL20) vs. a conventional visible light for 40 seconds (VL40). MATERIALS AND METHODS: Five specimens of resin composite, Herculite XRV, shade A-2 and Durafill VS, shade B-2, were made for each set of physical properties tested, for a total of 18 groups and 90 specimens. ANSI/ADA Specification #27 for direct filling resins was used as the protocol for specimen preparation and physical properties testing. An argon laser at approximately 285 mW, 6 mm beam size, power density of approximately 1,000 mW/cm2, and a conventional visible light at approximately 470 mW, 13 mm beam size, power density of approximately 354 mW/cm2, were used to polymerize the composite. Samples were stored in water in light-proof containers at 37 degrees C for at least 7 days and then tested on a Zwick universal testing machine. Mean DTS, CS or FS (MPa) values were calculated for each group. RESULTS: Herculite XRV's physical properties were not significantly affected by light source or exposure time. Light source or exposure time had no significant effect on DTS for Durafill VS. Significantly lower FS was found for Durafill VS, when cured for 10 seconds with the argon laser compared to 20 seconds with the laser or 40 seconds with the conventional light. In addition, significantly lower CS was found for the Durafill VS when polymerized with the laser at 10 seconds compared to the conventional light at 40 seconds.     

Occlusion of the semicircular canal using argon laser

The effects of argon laser on the bony semicircular canals were studied in the guinea pig. After intraperitoneal administration of Nembutal, the bulla was opened in order to approach the lateral and posterior canals. The anterior canal was approached through the posterior fossa. The argon laser was applied through a probe which was connected to a device from HGM Medical Laser Systems. One of the three semicircular canals was irradiated one to several times by argon laser (1.0-1.5 W x 0.5 sec). Histopathologic examination of the temporal bones revealed that the semicircular duct shrank immediately after irradiation. The laser produced a charred area in the bony canal wall. The semicircular canals gradually became fibrotic and ossified and completely occluded within several weeks. Heat produced in the bony canal may be responsible for the morphologic changes. On delayed observation, the cochlea of the canal-irradiated animals showed no morphologic changes. Auditory brain stem responses were normal. Caloric stimulation using 5 ml/5 sec of ice water revealed no response in the lateral canal-irradiated animals.     

Corneal neovascularization induced by xenografts or chemical cautery. Inhibition by cyclosporin A

PURPOSE: Neovascularization of the cornea occurs in numerous pathologic states causing decreased visual acuity and blindness and is a major complication of corneal allotransplantation. The purpose of this study was to investigate the effect of topical and systemic cyclosporin A (CsA) on corneal angiogenesis induced by xenotransplantation or by chemical cauterization. The subcutaneous disc angiogenesis system (DAS) also was used to study the effects of CsA on angiogenesis in a nonocular site. METHODS: Corneal angiogenesis was provoked by either xenotransplantation or chemical cautery. Rats from experiments using both of these models were subdivided into four treatment groups. Topical treatment was administered by using 4% CsA eye drops or vehicle (castor oil) four times daily for 10 days. Systemic therapy consisted of daily (5 mg/kg per day) subcutaneous injections of CsA or vehicle. In the DAS experiments, rats received CsA or vehicle systemically or intradisc. The amount of neovascularization was quantitated by digital image analysis in corneal flat preparations and sections of discs. RESULTS: Rats that received xenografts or cautery manifested less corneal neovascularization than did control animals after topical of subcutaneous CsA treatment. CsA also enhanced the survival of corneal xenografts. A difference between CsA and vehicle-treated animals in the DAS experiments was not detected. CONCLUSIONS: CsA effectively retards the growth of new vessels in the cornea after xenotransplantation or chemical cauterization and prolongs xenograft survival. However, CsA does not suppress angiogenesis in all systems, because it was ineffective in blocking vessel growth in the subcutaneous DAS.     

Secondary ambulatory voice prosthesis implantation with the argon laser using local anesthesia

An alternative technique for secondary tracheo-esophageal puncture and voice prosthesis implantation in topical anesthesia on an outpatient basis was developed. With argon laser beam passed through a glass fibre in the instrument channel of a flexible endoscope a secondary puncture of the tracheo-esophageal wall is obtained. A voice prosthesis is fitted subsequently, so that the whole operation is performed in one session in about 30 minutes. We generally administer 7.5 mg Midazolam orally for light sedation; antibiotics are not required. This method expands the possibility of voice prosthesis fitting in patients who are not considered or willing to have general anesthesia for various reasons. In 33 cases we did not see any complication. In two cases the tracheal wall was too tight due to radiation therapy, so that an operation had to be performed later on in general anesthesia. In one case technical problems led to an operation in local anesthesia in two steps. In all cases the patients did not complain of any considerable discomfort.     

Indications for photocoagulation with an argon laser. I. Anterior eye segment

1. Renal lithium clearance in healthy men was elevated while the subject was reclining, decreased upon standing and increased upon lying down during 45-60 min tests. 2. Parallel changes in renal clearance of creatinine, sodium and potassium, and urine flow rate occurred in response to the changes in posture. 3. The findings demonstrate for the first time that posture is a factor that can influence lithium excretion. Control of posture during lithium excretion tests is recommended.     

Fiberoptic argon laser stapedotomy: is it safe?

The history of otosclerosis surgery has been marked by major advances in both surgical technique and instrumentation. Fenestration, stapes mobilization, total stapedectomy, and stapedotomy were important advances in technique. Loupes, binocular microscopy, speculum holders, and microdrills similarly advanced instrumentation. What about fiberoptic argon laser handpieces for use in laser stapedotomy? Do they represent a significant advance in instrumentation, or are they merely another gimmick? Are fiberoptic argon laser handpieces safe? Experimentally, the thermal effects of argon laser, delivered via fiberoptic handpieces to a cadaver stapes and model vestibule, were studied. No significant temperature elevations within a model vestibule were observed during stapedotomy. There were significant temperature elevations within the laser plume at the level of the facial nerve. These findings are consistent with our experience in over 2200 primary and revision stapedotomies. To date, there have been no cases of significant hearing loss or permanent facial paralysis related to the use of these fiberoptic handpieces. We believe fiberoptic argon laser handpieces are as safe as conventional microsurgical instruments in stapes surgery.     

Effective mechanisms of laser photocoagulation for neovascularization in diabetic retinopathy

The present study compared the effect of acetaminophen, ibuprofen and misoprostol on PGE2 synthesis and orthodontic tooth movement. Guinea pigs were randomly assigned into one of three test groups or a control group. Each group received study treatments every 12 hours as an orthodontic force was applied to the maxillary incisors. Direct linear measurements of tooth separation were recorded at days 2, 4, 6, 10, and 11, and inflammatory exudate from the periodontal ligament (PDL) space was extracted and quantitatively analyzed radioimmunologically for the presence of PGE2 at days 4 and 9. Comparing the concentration of PGE2 in sample extracts, a significant difference (P = 0.001) was found among drug groups. A highly significant difference was found between the mean tooth separation among the various drug groups (P < 0.001). At day 11 the misoprostol group exhibited 4.49 +/- 0.49 mm of separation; ibuprofen 2.56 +/- 0.11 mm, and the control and acetaminophen groups exhibited similar degrees of tooth separation: 3.31 +/- 0.07 mm and 3.31 +/- 0.08 mm, respectively. A highly significant difference occurred between the mean rates of tooth separation among the various drug groups after day 8 (P < 0.001). Results of this study suggest that acetaminophen is the analgesic of choice for the relief of minor discomfort associated with orthodontic treatment.     

The rationale of argon green laser photocoagulation for diabetic maculopathy

To determine the effect of glycemic control on vitamin B12 (B12) metabolism in diabetes mellitus, we studied B12 metabolism in 19 diabetic patients with poor glycemic control and 15 normal individuals. The diabetic patients had significantly higher total B12 binding capacity (3303 +/- 963 pg/ml), higher serum B12 levels (1173 +/- 503 pg/ml) and unsaturated B12 binding capacity (2131 +/- 902 pg/ml) when compared with the normal controls, but there was no difference in R-binder levels and the B12 binding ratio between the two groups. During a 2-week admission to establish glycemic control, the fructosamine levels in the diabetic patients decreased from 556 to 428 mumol/l and the total B12 binding capacity as well as unsaturated B12 binding capacity were significantly improved to the normal range (P < 0.01), but serum B12 levels, R-binder levels and the B12 binding ratio were not changed. There was a significant association between serum fructosamine levels and the total B12 binding capacity in poorly controlled diabetic patients and the decrease of fructosamine was correlated significantly with the change of total B12 binding capacity and serum B12 levels in diabetic patients. These results indicate the effects of glycemic control on B12 metabolism in diabetes mellitus.     

Experience in the argon laser therapy of port wine stains

A total of 202 patients with port wine stains have been studied and many aspects of their clinical condition detailed. Employing ther argon laser, 136 test spots have been carried out in 132 patients and the results have been analyzed and correlated with clinical aspects of the lesions. Altogether, 85 treatments were performed in 54 patients and the results were examined in the same way as the test spots. Good to excellent results were obtained in 75 percent of test spots and 60 percent of treatments in that significant lightening of treated areas was achieved. While elimination of lesions was rare, considerable amelioration was common. Scarring was uncommon but was the most appreciable complication. Residual lesion was the most common cause of fair or poor results. The value of secondary treatment is suggested but remains to be established. The directions of ongoing clinical study are outlined.     

Effects of argon laser curing on dentin shear bond strengths

Previous studies have demonstrated the ability of the argon laser to polymerize light-activated materials and improve enamel shear bond strengths. This study was conducted to evaluate the effects of the argon laser on dentin shear bond strengths of current dentin bonding systems. Argon laser (HGM Model 8) at 231 and 280 mW, 5 sec bonding agent, 10 sec composite, and a conventional curing light (Translux EC/Kulzer) at 10 sec bonding agent, 20 sec composite were used to polymerize samples of dentin bonding systems [Scotchbond Multi-Purpose Plus (3M) and Prime Bond (Dentsply/Caulk), both with TPH (Dentsply/Caulk) composite]. A flat dentin bonding site (600 grit) was prepared on the buccal surface of extracted human teeth. Twelve samples were made for each set of parameters for both laser and conventional light totaling 48 samples. Samples were stored in distilled water in light-proof containers for 24 h at 37 degrees C. Shear bond strengths (MPa) were determined for each sample on the Instron testing machine. Mean values were calculated for each set of data and ANOVA with Fisher PLSD were used for statistical analysis. The argon laser provided bond strengths that were 21-24% greater than those of the conventional curing light system.     

Corneal wound healing after laser in situ keratomileusis in rabbits

BACKGROUND: The aim of this study was to characterize the cell biology of wound healing in rabbit corneas subjected to laser in situ keratomileusis (LASIK). METHODS: Rabbit corneas underwent LASIK with various multizone photoablations or only a lamellar keratotomy followed by repositioning of the flap. We looked for indications for an active wound healing process. Immunohistochemistry for the extradomain A cellular fibronectin (EDA-cFn) or tenascin (Tn) and routine histology were examined. RESULTS: Four days after LASIK or lamellar keratotomy followed by repositioning of the flap, epithelial plugs and prominent keratocytes as well as Tn and EDA-cFn immunoreactions-indicative of a wound-healing process-appeared in the wound margins. Epithelial plugs were less conspicous, and prominent, presumably activated, keratocytes were no longer identified at the wound margin at 2.5 and 5 months after wounding. However, EDA-cFn and Tn immunoreactivities could still be observed. Only the stromal cells located in the periphery of the flap and in relatively close contact with the epithelium were surrounded by scar tissue expressing immunoreactivity for EDA-cFn or Tn. The central corneal stroma was devoid of scar tissue. CONCLUSION: Results indicate that the wound healing reaction after LASIK takes place only at the periphery of the microkeratome wound, leaving the central optical zone clear.