Argon laser pretreatment in Nd: YAG iridotomy

Argon laser pretreatment prior to Nd:YAG laser iridotomy may decrease the incidence of operative hemorrhage. In a prospective, randomized clinical trial involving 12 patients (24 eyes), one eye was randomly assigned treatment with the Nd:YAG laser alone, while the other eye was pretreated with argon laser photocoagulation immediately prior to Nd:YAG laser. Eight of the 12 eyes (67%) treated with Nd:YAG laser alone had operative hemorrhages; only 2 of the 12 (17%) pretreated eyes did. Thus, argon laser pretreatment significantly reduced the incidence of hemorrhage during Nd:YAG iridotomy (P = .012).     

Prostaglandin release following Nd:YAG iridotomy in rabbits

In this study, iridotomies were performed in nine rabbit eyes using an Nd:YAG laser at 5.2 mJ, three pulses/burst, for one burst. Prostaglandin E2 (PGE2) in aqueous humor obtained at timed intervals after treatment was then measured using a sensitive and specific radioimmunoassay. Concentrations of PGE2 (mean +/- SD pg/ml) were: pretreatment, 377 +/- 89; 30 minutes, 1858 +/- 241; 120 minutes, 735 +/- 308; and 240 minutes, 401 +/- 59, postoperatively. The release of PGE2 into the aqueous humor parallels the rise in intraocular pressure following Nd:YAG iridotomies in rabbits and thus may contribute to this phenomenon.     

Argon laser pretreatment 4 to 6 weeks before Nd:YAG laser iridotomy.

Argon laser pretreatment followed by Nd:YAG laser iridotomy 4 to 6 weeks later was performed in the right eye of 10 patients. Primary Nd:YAG laser iridotomy was performed in the left eye. Significantly more Nd:YAG laser energy was needed to produce an iridotomy in pretreated eyes (P less than .001). Pretreated eyes developed a significantly larger pigment epithelium defect around the iridotomy site and a greater degree of pigmentation of the inferior part of the trabecular meshwork 6 months following treatment. Argon laser pretreatment followed by Nd:YAG laser iridotomy 4 to 6 weeks later appears to offer no advantages over primary Nd:YAG laser iridotomy.     

Use of apraclonidine to reduce acute intraocular pressure rise following Q-switched Nd:YAG laser iridotomy

We evaluated the effectiveness of topical apraclonidine (ALO 2145, p-amino clonidine hydrochloride) in suppressing an acute postoperative intraocular pressure (IOP) rise following Nd:YAG laser iridotomy. Fifty-eight eyes (45 patients) with chronic primary angle-closure glaucoma underwent Q-switched Nd:YAG laser iridotomy. Twenty-nine eyes followed prospectively underwent Nd:YAG laser iridotomy following the topical administration of 0.5% apraclonidine prior to and immediately following the procedure. A retrospective control group of 29 eyes underwent Nd:YAG laser iridotomy without topical apraclonidine. Only one eye (3.4%) treated with apraclonidine experienced an IOP rise greater than 10 mm Hg over baseline, while five among 29 untreated eyes (17.2%) developed an IOP rise greater than 10 mm Hg.     

Peripheral iridotomy using Nd:YLF laser.

We used the Nd:YLF Oscillator/Regenerative Amplifier Laser (ISL, San Diego, Calif) at 1053 nm to perform peripheral iridotomies in three eyes. The total amount of energy required was greater than the usual amount needed in Nd:YAG peripheral iridotomies. However, each laser pulse uses a much smaller quantity of laser energy and produces a smaller and more refined optical breakdown. The postoperative courses for these patients were uneventful, without postoperative intraocular-pressure spike or increasing anterior-chamber reactions.     

Endophthalmitis following Nd:YAG laser posterior capsulotomy

We report the development of Propionibacterium acnes endophthalmitis following Nd:YAG laser posterior capsulotomy. The patient previously underwent uncomplicated extracapsular cataract extraction with intraocular lens insertion and was free of inflammation prior to laser capsulotomy. Diagnostic vitrectomy and aqueous tap were performed, and P. acnes was isolated from the aqueous in thiol broth media after nine days of incubation under anaerobic conditions. The patient was managed with topical and systemic antibiotics and steroids. Complete resolution of inflammation with return of vision to 20/25 was achieved without removal of the intraocular lens or lenticular remnants.     

Acute glaucoma following Nd: YAG laser membranotomy

A 65-year-old aphake with a functioning filtration bleb underwent neodymium:YAG laser membranotomy. Shortly thereafter, he acutely developed pain, nausea, and visual blur with an intraocular pressure of 42 mm Hg. The mechanism of the acute glaucoma is believed to be occlusion of the fistula by herniated vitreous.     

Histological evaluations following 1,064-nm Nd:YAG laser resurfacing

BACKGROUND AND OBJECTIVES: The long pulse 1,064-nm Nd:YAG laser is used clinically to decrease rhytid formation. The dermal level at which this change occurs has not been established. This study attempts to answer these questions using a porcine skin model. STUDY DESIGN/MATERIALS AND METHODS: Non-randomized prospective experimental trial involving the domestic piglet treated serially with the long pulse 1,064-nm Nd:YAG laser. RESULTS: Collagen formation occurred at the level of the reticular dermis. After one laser treatment, a significant level of collagen formation was induced in the reticular dermis compared to controls. The greatest gain was observed after four laser treatments. Energy levels of 20, 30, 40, and 50 J/cm2 were evaluated. Although not statistically significant, 30 J/cm2 had the greatest effect on collagen formation. However, at 50 J/cm2, marked ablative changes to the epidermis were observed. CONCLUSIONS: The long pulse 1,064-nm Nd:YAG laser induces collagen formation in the reticular dermis in porcine skin.     

Marked intraocular pressure rise following Nd:YAG laser capsulotomy

A Nd:YAG laser was used to perform a posterior capsulotomy on a patient one and a half years after phacoemulsification. Within 24 hours the intraocular pressure had increased to 67 mm Hg despite pre-treatment with timolol and acetazolamide. Intraocular pressure eventually returned to pre-capsulotomy levels after several days. A mechanism is postulated for the particularly high pressures encountered in this case.     

Reopening cyclodialysis cleft with Nd:YAG laser following trabeculectomy

A patient with primary open-angle glaucoma (POAG) underwent a trabeculectomy according to Watson's technique. Postoperative intraocular pressure (IOP) ranged from 8 to 11 mm Hg. However, repeat slit lamp evaluation revealed the absence of bleb formation. Two months post-filtration surgery the patient developed the sudden onset of nausea, vomiting, supraorbital pain, and blurred vision. The IOP was 46 mm Hg and gonioscopy revealed a hyaline membrane covering a cyclodialysis cleft. A Nd:YAG laser was used to reopen the cleft, with normalization of IOP.     

Nd:YAG laser bipolar dissector--preliminary results.

We have developed a laser bipolar dissector (LBD) which uses the 1,064 nm Nd:YAG wavelength. The laser emits from the inner surface of the distal 7 mm of each probe made of synthetic sapphire. With low laser power (15-25 W), the bipolar provides hemostatic cutting of larger blood vessels. Animal experiments were carried out using New Zealand white rabbits. The LBD hemostatically cut through veins up to 5 mm and arteries up to 2 mm in diameter. Rebleeding did not occur. Transection of parenchymal organs such as liver and lung was easily performed with complete hemostasis. In chronic experiments a partial hepatectomy with splenectomy and left nephrectomy was performed using the LBD alone without any ligation. Up to 3 weeks postoperatively there were no direct complications related to using the LBD. In conclusion the LBD could perform a hemostatic transection of large vessels and might have clinical application in the dissection of vascular parenchymal organs.     

Corneal edema following argon laser iridotomy.

Laser iridotomy is generally a safe and effective procedure for narrow-angle glaucoma. However, since surgical success with the argon laser depends on a focal thermal effect, a corneal burn is a possible complication. I describe five patients with occludable anterior chamber angles and bilateral corneal guttata who developed uniocular progressive corneal edema with visual loss following argon laser iridotomy. These five patients underwent iridotomy with a total laser energy of 63, 48.5, 7, 25, and 25 J, respectively, and began to lose vision due to corneal edema immediately, and 5, 2, 4, and 2 years later, respectively. Following penetrating keratoplasty with cataract surgery, histopathology of the corneal buttons showed generalized endothelial cell loss in all five. Microstructural findings of guttata and thickened Descemet's membrane implied that prior endothelial dystrophy had predisposed these patients to laser-induced damage. Risk factors for immediate or delayed-onset bullous keratopathy after argon laser iridotomy include prior angle closure, preexisting endothelial guttata, and high laser energy with multiple applications. Recognizing the potential of this complication offers opportunities for preventive strategies.     

Ocular hypertension following Nd:YAG laser capsulotomy: a potentially blinding complication

A dense secondary membrane was treated with a Nd:YAG laser capsulotomy with marked improvement in visual acuity, from count fingers to 6/9 (20/40). Four hours following therapy, visual acuity in the treated eye was no light perception, due to extreme ocular hypertension (over 80 mm Hg). The extreme elevation in intraocular pressure appears to have been caused by cellular debris obstructing the trabecular meshwork in an angle already compromised by angle recession. An emergency paracentesis was successful in restoring the visual acuity.     

Nd:YAG laser augmented pneumatic retinopexy

We present the first ten consecutive cases of rhegmatogenous retinal detachment treated by one surgeon using pneumatic retinopexy with Nd:YAG laser disruption of vitreoretinal adhesions. In nine cases the retina has remained reattached, after a follow-up period of 11 to 18 months. The use of the Nd:YAG laser to disrupt vitreoretinal adhesions at the sites of retinal tears is discussed.     

Ultrastructural changes of human dentin after irradiation by Nd:YAG laser

BACKGROUND AND OBJECTIVE: The use of Nd:YAG laser has been proposed for endodontic treatment. However, its ability to reduce dentin permeability, which is important for the success of root canal treatment, remains controversial. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human dentin. The parameters were: pulse energy (100 mJ), rate (10 pps), and total irradiation time (4 seconds). The crystalline phases, electron diffraction patterns, morphology, and microstructure of specimens after laser irradiation were observed by dark-field emission transmission electron microscope (TEM). RESULTS: Three ultrastructural zones could be delineated in the dentin: (1) an outer zone with an ordered columnar structure composed of hydroxyapatite and beta-tricalcium phosphate, (2) an intermediate zone composed of an amorphous substance (about 40-70 nm in diameter), and (3) an inner zone of well-crystallized hydroxyapatite grains. These three zones were free of pores or voids. CONCLUSIONS: Our study demonstrated that laser-irradiation might be used to reduce dentin permeability.     

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND AND OBJECTIVE: The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining. RESULTS: The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality. CONCLUSION: Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.     

Probe orientation in contact Nd:YAG laser cyclophotocoagulation.

We investigated the effect of the angle orientation of the probe during Nd:YAG transscleral cyclophotocoagulation. We found, based on histologic evaluation of the ciliary processes and surrounding structures, that the angle at which the probe was placed on the eye was critical. A probe angulation as little as 15 degrees off the perpendicular destroyed sites less than optimal for achieving the goal of decreasing aqueous humor production.