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This article describes the development of a surgical technique employing a carbon dioxide laser for endodontic periapical procedures. The advantages of laser application for sterilization and removal of the infected root apex, as well as enhanced hemostasis, are cited. A case in which the "laser apicoectomy" technique was performed successfully for treatment of secondary apical abscess is presented.
To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (lambda = 620 nm, tau p = 3 x 10(-13) S, fp = 0.5 Hz, Ep = 1.1 x 10(-3) J cm-2, Iav = 5.5 x 10(-4) W cm-2, Ip = 10(9) W cm-2) and continuous wave (CW) laser radiation (lambda = 632.8 nm, I = 1.3 W cm-2). The irradiation dose required to produce a similar biological effect (a 160%-190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 10(3) lower for pulsed radiation than for CW radiation (3.3 X 10(-1) and 7.8 X 10(2) J cm-2 respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 A, which corresponds to the size of the chromophores of hypothetical primary photoacceptors--respiratory chain components.
PURPOSE: To report the first case of macular hemorrhage following laser in situ keratomileusis (LASIK) with femtosecond laser flap creation. DESIGN: Observational case report. METHODS: A 36-year-old woman underwent uncomplicated, bilateral, simultaneous LASIK procedures for correction of moderate myopia (-5.00 diopters OD and -6.00 diopters OS). LASIK flap creation was performed using the IntraLase femtosecond laser. RESULTS: On postoperative day 1, the patient's uncorrected and best-corrected visual acuities were 20/20 OD and 20/40 OS. A dilated fundoscopic examination revealed a one-third disk diameter macular hemorrhage OS. An intravenous fluorescein angoiogram ruled out the presence of predisposing macular pathology. Two months after LASIK, the macular hemorrhage had cleared, and 6 months later, the BCVA improved to 20/25 OS. CONCLUSIONS: Macular hemorrhage may occur after LASIK, even in the absence of previously identified risk factors, such as high myopia, pre-existing choroidal neovasculaization, lacquer cracks, and sudden changes in intraocular pressure associated with microkeratome-assisted flap creation.
PURPOSE: To compare laser in situ keratomileusis (LASIK) results obtained with the femtosecond laser (IntraLase Corp.) to those obtained using 2 popular mechanical microkeratomes. SETTING: Private practice, Greensboro, North Carolina, USA. METHODS: This retrospective analysis compared LASIK outcomes with the femtosecond laser to those with the Carriazo-Barraquer (CB) microkeratome (Moria, Inc.) and the Hansatome microkeratome (Bausch & Lomb, Inc.). The 3 groups were matched for enrollment criteria and were operated on under similar conditions by the same surgeon. RESULTS: There were 106 eyes in the IntraLase group, 126 eyes in the CB group, and 143 eyes in the Hansatome group. One day postoperatively, the uncorrected visual acuity (UCVA) results in the 3 groups were similar; at 3 months, the UCVA and the best spectacle-corrected visual acuity results were not significantly different. A manifest spheroequivalent of +/-0.50 diopter (D) was achieved in 91% of eyes in the IntraLase group, 73% of eyes in the CB group, and 74% of eyes in the Hansatome group (P<.01). IntraLase flaps were significantly thinner (P<.01) and varied less in thickness (P<.01) than flaps created with the other devices. The mean flap thickness was 114 microm +/- 14 (SD) with the IntraLase programmed for a 130 microm depth, 153 +/- 26 microm with the CB using a 130 microm plate, and 156 +/- 29 microm with the Hansatome using a 180 microm plate. Loose epithelium was encountered in 9.6% of eyes in the CB group and 7.7% of eyes in the Hansatome group but in no eye in the IntraLase group (P =.001). Surgically induced astigmatism in sphere corrections was significantly less with the IntraLase than with the other devices (P<.01). CONCLUSIONS: The IntraLase demonstrated more predictable flap thickness, better astigmatic neutrality, and decreased epithelial injury than 2 popular mechanical microkeratomes.
PURPOSE: To compare the visual and refractive outcomes of laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK) in the treatment of high myopia. SETTING: Institute of Vision Research, Department of Ophthalmology, College of Medicine, Yonsei University, and Balgeunsesang Ophthalmology Clinic, Seoul, South Korea. METHODS: Four hundred seventy eyes of 240 patients with manifest refraction spherical components greater than -6.00 diopters (D) were assigned to 2 groups: 324 eyes (167 patients) were treated with LASIK and 146 eyes (73 patients), with LASEK. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), remaining refractive error, corneal haze, and complications were followed in both groups for 12 months. RESULTS: At 12 months, the mean spherical equivalent (SE) was within +/-0.50 D of emmetropia in 205 eyes (63.3%) in the LASIK group and 81 eyes (55.5%) in the LASEK group and within +/-1.00 D in 261 eyes (80.6%) and 104 eyes (71.2%), respectively. The UCVA was 20/25 or better in 269 LASIK eyes (83.0%) and 111 LASEK eyes (76.0%). There was more than a 1-line loss of BSCVA in 4 LASIK eyes (1.2%) and 21 LASEK eyes (14.3%). The between-group differences in SE, magnitude of cylinder, UCVA, and haze were statistically significant (P<.05). CONCLUSIONS: Both LASIK and LASEK were safe and effectively treated eyes with high myopia. Laser in situ keratomileusis provided superior results in visual predictability and corneal opacity.
PURPOSE: To evaluate the efficacy, predictability, and safety of custom laser in situ keratomileusis (LASIK) using the Visx wavefront platform CustomVue for the treatment of myopia and myopic astigmatism. SETTING: Stanford University Eye Laser Center, Stanford, California, USA. METHODS: This retrospective analysis was of the initial 140 eyes of 78 patients treated consecutively with LASIK for myopia using the Visx Star S4 excimer laser. Primary outcome variables, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and complications, were evaluated at 1 week and 1 and 3 months. Vector analysis was performed on eyes that received astigmatic correction. RESULTS: Mean preoperative spherical equivalent (SE) was reduced from -3.89 diopters +/- 1.48 (SD) to an SE of -0.21 +/- 0.36 D at 1 month and -0.28 +/- 0.36 D at 3 months (P < .001). At 1 and 3 months, UCVA was 20/20 or better in 84.3% and 87.9%, respectively. Eighty-six percent of eyes at 1 month and 81.4% of eyes at 3 months were within +/-0.5 D of emmetropia. No eyes lost more than 2 lines of BSCVA. Vector analysis yielded an index of success of 0.39, indicating a 61% success rate in achieving the astigmatic surgical correction at 3 months. The preoperative root-mean-square value of 0.28 +/- 0.08 microm increased slightly to 0.33 +/- 0.11 microm at 1 month and 0.34 +/- 0.11 microm at 3 months. CONCLUSION: Wavefront-guided LASIK using the Visx CustomVue system was effective, predictable, and safe for correction of low to moderate myopic refractive error.
PURPOSE: To compare the effectiveness of subthreshold grid laser treatment (SGLT) with an infrared micropulse diode laser with that of threshold grid laser treatment (TGLT) for macular edema secondary to branch retinal vein occlusion (BRVO). DESIGN: Randomized clinical trial. PARTICIPANTS: Thirty-six patients (36 eyes) were randomized either to infrared SGLT (17 eyes) or to krypton TGLT (19 eyes). METHODS: Complete ophthalmic examinations, including determination of visual acuity (VA) with Early Treatment Diabetic Retinopathy Study charts, optical coherence tomography (OCT), and fluorescein angiography, were performed at the time of the study entry and at 6-month intervals, with a planned follow-up of 24 months. MAIN OUTCOME MEASURES: Primary: decrease in mean foveal thickness (FT) on OCT. Secondary: changes of the total macular volume (TMV) over the follow-up, proportion of eyes that gained at least 10 letters (approximately > or =2 lines of VA gain) at the 12- and 24-month examinations, and timing of macular edema resolution. RESULTS: Changes in mean FT and TMV from the initial values were statistically significant for TGLT from the 6-month examination (P<0.001) and for SGLT from the 12-month examination (P<0.001). After 1 year, there was no difference in mean FT and TMV between the 2 groups. At the 12-month examination, 10 patients of the SGLT group (59%) and 11 of the TGLT group (58%) gained at least 10 letters (2 lines) in VA. At the 24-month examination, this gain was achieved by 11 patients (65%) of the SGLT group and 11 (58%) of the TGLT group. Moreover, at the 24-month examination 59% and 26% gained 3 lines in the SGLT and TGLT groups, respectively. CONCLUSIONS: Resolution of macular edema and VA improvement are similar to those obtained with conventional TGLT, but SGLT is not associated with biomicroscopic and angiographic signs. A multicenter randomized clinical trial would be needed to ascertain the real efficacy and the most appropriate settings of SGLT for macular edema secondary to BRVO.
BACKGROUND: The purpose of this investigation was to assess postoperative survival and quality of life with transmyocardial laser revascularization (TMR) in high-risk patients. METHODS: During a 24-month period, 81 consecutive patients underwent either sole therapy TMR (n = 34) or TMR with coronary artery bypass grafting (n = 47) using a holmium:yttrium-aluminum-garnet (YAG) laser. Outcomes were assessed in three high-risk groups, including patients with left ventricular dysfunction (ejection fraction < or = 0.40) (n = 37), unstable angina (n = 30), and congestive heart failure (n = 33). Disease-specific quality of life was assessed using the Seattle Angina Questionnaire in 58 late survivors and compared with an age-matched cohort undergoing coronary artery bypass grafting only (no TMR) (n = 20). RESULTS: Overall mortality was 6% +/- 3% (+/- 70% confidence limit) and appeared higher with left ventricular dysfunction (11% +/- 5% vs 2% +/- 2%), but the difference did not reach statistical significance (p = 0.17; power = 0.16). There was also no statistical difference with unstable angina (10% +/- 6% vs 4% +/- 3%; p > 0.53) or congestive failure (9% +/- 5% vs 4% +/- 3%; p > 0.66). However, survival at 18 months was significantly lower with left ventricular dysfunction (62% +/- 9% vs 90% +/- 5%; p < 0.003) and congestive failure (48% +/- 10% vs 96% +/- 3%; p < 0.001). For sole therapy TMR, quality of life was diminished comparing TMR with coronary artery bypass grafting (p < 0.004) and coronary artery bypass grafting only (p < 0.002). CONCLUSIONS: Transmyocardial laser revascularization can be performed in high-risk patients, but survival is significantly impaired in patients with left ventricular dysfunction and congestive failure, and quality of life is diminished without some degree of direct revascularization.
OBJECTIVE: To assess the effectiveness of low-intensity laser therapy in the treatment of musculoskeletal low back pain. DESIGN: A double-masked, placebo-controlled, randomized clinical trial. SETTING: A physical medicine and rehabilitation clinic. PARTICIPANTS: Sixty-three ambulatory men and women between the ages of 18 and 70yrs with symptomatic nonradiating low back pain of more than 30 days' duration and normal neurologic examination results. INTERVENTION: Subjects were bloc randomized into two groups with a computer-generated schedule. All underwent irradiation for 90 seconds at eight symmetric points along the lumbosacral spine three times a week for 4 weeks by a masked therapist. The sole difference between the groups was that the probes of a 1.06 microm neodymium:yttrium-aluminum-garnet laser emitted 542mW/cm2 for the treated subjects and were inactive for the control subjects. MAIN OUTCOME MEASURES: Subject's perception of benefit, level of function as assessed by the Oswestry Disability Questionnaire, and lumbar mobility. RESULTS: The treated group had a time-dependent improvement in two of the three outcome measures: perception of benefit and level of function. These results were most marked at the midpoint evaluation (p < .005, p < .01) and end of treatment (p < .017, p < .001) but tended to lessen at the 1-month follow-up (p < .10, p < .004). Lumbar mobility did not differ between the groups at any time. All tests were two-sample t tests with unequal variances. CONCLUSIONS: Treatment with low-intensity 1.06 microm laser irradiation produced a moderate reduction in pain and improvement in function in patients with musculoskeletal low back pain. Benefits, however, were limited and decreased with time. Further research is warranted.
We have demonstrated that flame laser-enhanced ionization (LEI) and flame laser-induced atomic fluorescence (LIAF) techniques can be used as, alternative sensitive detectors for gas chromatographic (GC) analysis of organotin compounds. These two element-specific detection methods are free from interferences from the organic solvent. Two types of LEI schemes for Sn detection are employed. For the two-step LEI scheme (TLEI), the tin atoms in the flame were stepwise excited and then ionized collisionally. In contrast, in detection with the single-step LEI scheme (SLEI), only one dye laser is used. For the analysis of tetramethyltin and tetraethyltin, the GC-TLEI, GC-SLEI, and GC-LIAF systems yield linear dynamic ranges of 0.015-400, 0.39-600 and 0.5-600 ng, respectively. The corresponding detection limits reach 0.15, 3.9 and 5.0 mg/l, with absolute quantities corresponding to 15, 390 and 500 pg, respectively, for an injection volume of 0.1 microl. These detection methods prove to be more sensitive and selective than the conventional flame ionization detection, which achieves absolute detection limits of 800 and 1667 pg for tetraethyltin and tetramethyltin, respectively, under identical GC conditions.
Among other things, the fragmentation efficiency of laser lithotripsy using a dye laser depends upon the physical properties of the surface of the calculus, especially optical absorption. In this in vitro study we were able to increase the fragmentation efficiency on white, nonabsorbing calculi by introducing an absorbing liquid between the distal end of the fiber and the stone surface. This absorbing liquid (in our case potassium dichromate) provides a reliable plasma ignition and thus makes the fragmentation independent of the properties of the stone surface. Furthermore, we examined and documented the existence of liquid jets that were produced by the collapse of a cavitation bubble near a stone. We observed considerable fragmentation effects on artificial stones that were, however, inferior to those achieved with the fiber in contact with the stone. This work suggests that the effects of a liquid jet should be taken into consideration when using a holmium:YAG laser for lithotripsy.
A total of 25 patients with symptomatic bladder outlet obstruction due to benign prostatic hyperplasia was entered into a prospective, randomized trial comparing laser prostatectomy performed with the Urolase right angle firing neodymium:YAG laser fiber to standard transurethral electroresection of the prostate. Overall acute perioperative morbidity, including blood loss and fluid absorption, was significantly less for patients undergoing laser prostatectomy. Efficacy of treatment was assessed by standardized American Urological Association symptom scores, patient assessment of symptom improvement, peak urinary flow rates and post-void residual urine volumes, and was equivalent for the 2 treatment groups at 3 and 6 months.
The goal of the present study was to analyze the interaction between incident laser light and retinal tissue in confocal scanning laser ophthalmoscopy and tomography. We examined the change in axial intensity distribution during evaluation of the retinal surface topography in macular and optic nerve head evaluation in normal volunteers and patients with different retinal diseases. Additionally, we examined a model eye with a model cyst and human globes in an eye mounting chamber. We found that confocal scanning laser tomographs record specular reflected light originating from intraocular surfaces as well as light scattering from deeper retinal structures. Concave and convex retinal surfaces and eye movements may influence accurate topographic detection. Knowledge of the exact mechanism of image formation in confocal tomography is of great importance for the understanding of validity of these measurements. Proper identification of observed artifacts and preventive measures will increase the utility, reproducibility, and validity of this technology.
OBJECTIVE: To evaluate the efficacy, safety, and predictability of hyperopic laser in situ keratomileusis (H-LASIK) using modified software. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: The first 72 consecutive eyes of 44 patients with up to +5.00 diopters (D) hyperopia. INTERVENTION: Hyperopic LASIK using the Automatic Corneal Shaper (ACS; Chiron Vision, Claremont, CA) and the Nidek EC-5000 excimer laser (Nidek, Tokyo, Japan). MAIN OUTCOME MEASURES: Uncorrected visual acuity, manifest spherical equivalent (MSE), best-corrected visual acuity (BCVA), and complications were studied. RESULTS: At 6 months, in the low hyperopia group (<3.00 D), mean MSE was +0.30 +/- 0.71 D, with 88.9% eyes within 1 D of emmetropia compared with +1.09 +/- 0.92 D and 51.8% within 1 D of emmetropia in the moderate hyperopia group (> or =3.00 D; P = 0.003). Uncorrected visual acuity was 20/40 or better in 43 of 45 eyes (95.6%) and in 21 of 27 (77.8%) eyes in the low and moderate hyperopia groups, respectively. Only one eye (1.4%) from the moderate hyperopia group lost two lines of BCVA. Eighteen eyes (25%) required retreatment to correct residual hyperopia, 9 eyes (20.0%) in the low hyperopia group and 9 eyes (33.3%) in the moderate hyperopia group. Retreatments resulted in an MSE of +0.02 +/- 0.45 D and +0.04 +/- 0.73 D in the low and moderate hyperopia groups, respectively. No flap-related complications were seen. CONCLUSIONS: Hyperopic LASIK with the ACS and the Nidek EC-5000 excimer laser using our modified software is a safe, effective, and predictable procedure for low hyperopia. Results are satisfactory up to moderate hyperopia. Significant regression can occur for low and moderate hyperopia. Retreatment can be performed safely and effectively to improve the visual and refractive results.
BACKGROUND: To evaluate the safety and efficacy associated with the clinical use of a Q-switched neodymium:yttrium-aluminum-garnet (ND:YAG) laser for cataract removal. DESIGN: Multicenter, prospective, noncomparative case series. PARTICIPANTS/INTERVENTION: A total of 1000 consecutive eyes underwent cataract extraction with the photolysis Q-switched ND:YAG laser at 12 international clinical sites. MAIN OUTCOME MEASURES: Visual acuity improvement; total energy used; mean operative time for cataract removal; complications, both intraoperative and postoperative; with a minimum follow-up of 3 months. RESULTS: The mean values were visual acuity improvement from 20/70.2 to 20/24.4. Mean intraocular energy used was 5.65 J per case. Mean operative photolysis time among the surgeons was for up to +1 nuclear sclerosis, 2.15 minutes; up to +2 nuclear sclerosis, 4.8 minutes; and for up to +3 nuclear sclerosis, 9.8 minutes. Three cases were completed by intraocular lens implantation through the original sub-2-mm incision, using a prefolded, by dehydration, acrylic intraocular lens. Minor complications were encountered in 18 cases. CONCLUSIONS: These data suggest this photolysis laser technology may be a safe and effective alternative for cataract extraction in human eyes. By use of small clear cornea incisions, the ability to perform cataract extraction and intraocular lens implantation with incisions less than 2 mm has been shown for the first time.
Tissue absorption lengths for infrared radiation at 2.8 to 3.1 micron are very short due to strong absorption by water. Corneal ablation using pulsed lasers at these wavelengths can potentially produce incisions similar in quality to cuts produced by excimer lasers at 193 nm. The authors have used 8-ns pulses at 2.80 and 2.92 micron, generated by a Raman-shifted neodymium:YAG (Nd:YAG) laser, to make slit-like incisions in bovine and human corneas. At 2.8 micron, etch depth per pulse increases sigmoidally from 0.15 micron at 390 mJ/cm2 to 3.8 micron at 2200 mJ/cm2. No ablation occurs at fluences below 250 mJ/cm2. Light and transmission electron microscopy show smooth-walled incisions bordered by a thermally damaged region that varies in width from 1.5 micron at 600 mJ/cm2 to 10 micron at 2200 mJ/cm2. The small amount of tissue damage produced at low fluences suggests that infrared ablation may be useful in keratorefractive surgery.
PURPOSE: To learn the long-term outcome of ciliary ablation with diode laser contact transscleral cyclophotocoagulation (TSCPC) in eyes with recalcitrant, severe glaucoma. METHODS: Twenty-seven eyes of 27 patients with medically and surgically uncontrollable glaucoma and no previous ciliary ablation enrolled in this study. After baseline measurements and informed consent, the authors performed contact TSCPC. There were 14 pseudophakic, 7 aphakic, and 6 phakic eyes; 15 of these had primary open angle glaucoma and the remainder had various secondary or open- or closed-angle glaucomas. Median follow-up was 19 months (range, 6 weeks to 27 months). Initially after laser surgery, glaucoma medications were continued, except for a 2-week interruption of miotics; the ophthalmologist later adjusted medications in accordance with the patient's status. The authors define failure of TSCPC in two ways, based on IOP measurements during two consecutive study examinations 6 weeks or more after intervention or at the final examination: (1) less than 20% intraocular pressure (IOP) reduction from baseline, and (2) either less than 20% reduction of IOP from baseline or IOP greater than 22 mmHg. RESULTS: For 27 eyes, the baseline IOP (mean +/- standard deviation) was 36.4 +/- 12.4 mmHg (range, 20-70 mmHg). The mean IOP at last examination was 20.3 +/- 8.7 mmHg. With failure definition 1, the cumulative probability of success was 84% at 1 year and 62% at 2 years. With failure definition 2 the cumulative probability of success was 72% at 1 year and 52% at 2 years. At the last examination, 19 eyes (70%) had visual acuity improved within one line of visual acuity at eligibility. One of these eyes, with light perception vision at entry, declined to no light perception. Three eyes (11%) lost two lines of vision and five (19%) lost three or more lines. CONCLUSIONS: Contact diode laser TSCPC yields long-term improvement of IOP and preservation of visual acuity in a substantial proportion of eyes with severe, medically uncontrolled glaucoma.
PURPOSE: To evaluate objectively and subjectively the long-term outcome of laser in situ keratomileusis (LASIK) in patients with high and very high myopia. SETTING: Department of Ophthalmology, Philipps University, Marburg, Germany. METHODS: Thirty-three eyes of 19 patients were followed for a mean of 76 months (range 50 to 84 months) after primary LASIK using the Keratom I excimer laser (Schwind) and the ALK microkeratome (Chiron). Refraction, glare, pachymetry, corneal topography, and tear-film secretion and stability were measured. At the last examination, patients also answered a 14-item questionnaire. RESULTS: Preoperatively, the mean spherical equivalent was -13.65 diopters (D). At 1 year, it was -0.25 D and after 6 years, -0.88 D. Fifteen percent of eyes lost > or =2 lines of best spectacle-corrected visual acuity (BSCVA), and 9% gained > or =2 Snellen lines. At the end of the study, 46% of eyes were within +/-1.0 D of the attempted corrected and 88% were within +/-3.0 D. There were 5 microkeratome-associated complications; 3 resulted in loss of BSCVA. The latest pachymetry showed a mean corneal thickness of 498.5 microm (range 396 to 552 microm). There were no cases of keratectasia. Seventy-five percent of patients noted an increase in their quality of life. Seventy-one percent were satisfied with their postoperative visual acuity; however, 75% noticed glare and halos at night. CONCLUSIONS: Laser in situ keratomileusis correction of very high myopia did not cause keratectasia in the long term provided the corneal thickness was respected. A flap thickness setting of 130 microm with a first-generation microkeratome resulted in a high number of cut failures. Most patients were happy with the results despite a modest level of accuracy and glare.