The effects of Nd:YAG laser iridotomy on the corneal endothelium

We studied 18 eyes of 18 patients undergoing Nd:YAG laser peripheral iridotomy for occludable anterior chamber angles. A Q-switched laser was used for all treatments. Preoperative and postoperative pachymetry and corneal endothelial cell counts were obtained centrally, in the nontreated superonasal quadrant, and in the treated superotemporal quadrant. No significant differences were found between preoperative and postoperative corneal thickness at any site. A small decrease in endothelial cell count (95 cells/mm2) at the treated site was statistically significant (P = .04).     

Influence of argon laser treatment of glaucoma on corneal endothelium

The morphometric study of the corneal endothelium was carried out by means of specular microscopy prior to and for one year following laser trabeculoplasty (LTP) or laser iridotomy. A significant increase in the endothelial cell size was demonstrated in 6 months after trabeculoplasty and in 3 months following iridotomy. The magnitude of increase in cell size following laser iridotomy was significantly correlated with the amount of laser energy delivered to the eye. However, such correlation was not demonstrated following LTP where the applied energy was kept fairly constant among the present treated cases. The increase in cell size failed to correlate with clinical factors including IOP before and after laser therapy, age and the presence or absence of endothelial burn. The treatment protocols using reduced energy are indicated to minimize endothelial damage induced by LTP or laser iridotomy.     

Retinal damage after argon laser iridotomy

We conducted a prospective clinical study to evaluate potential retinal damage after argon laser iridotomy in 25 eyes of 22 patients with primary chronic angle-closure glaucoma. Kinetic perimetry and ophthalmoscopy showed no detectable damage. Iridotomy required a mean of 11.4 +/- 10 joules to achieve a patent coloboma of 200 micron after one to three sessions. Dark-prone and mydriasis tests were performed one month after surgery. Pilocarpine was discontinued in all cases. Both static perimetry and fluorescein angiography of the midperiphery corresponding to the meridian of laser coloboma done six months after surgery showed focal damage. There was no damage in control tests of the same eyes in an opposite area of the retina.     

激光周边虹膜成形术及激光周边虹膜成形联合虹膜切开术对角膜内皮细胞的影响

目的 比较激光周边虹膜成形术及激光周边虹膜成形联合虹膜周边切开术对角膜内皮细胞的影响。方法 对15例20眼单纯行周边虹膜成形术；对17例23眼行周边虹膜成形联合虹膜切开术。采用接触型镜面反光显微镜(Konan SP-5500型，日本)检测术前、术后1小时、1周、1月、3月、6月的角膜内皮细胞。统计分析平均细胞密度、细胞面积的变异系数和六边形细胞的百分率。结果 两种激光术式治疗后1小时至6个月与治疗前相比较，角膜内皮平均细胞密度、平均细胞面积变异系数、六边形细胞的百分率均有显著性差异，两组间比较各时期内皮细胞密度没有显著性差异。术后3个月和6个月细胞面积变异系数和六角形细胞百分率两组间比较有显著性差异。结论 两种激光术式均可引起角膜内皮细胞的损害，联合激光术式对角膜内皮细胞的损害大于单纯术式。     

Corneal endothelial changes after argon laser iridotomy

We used a continuous-wave argon laser to produce iridotomies in 28 eyes of 17 patients (12 women and five men ranging in age from 44 to 84 years) with angle-closure glaucoma. We photographed the central corneal endothelium with a contact specular microscope before and after the laser iridotomy was produced. The mean number of cells before treatment was 2,516 cells/mm2 and the mean number after treatment was 2,391 cells/mm2. The mean decrease, therefore, was 125 cells/mm2. This decrease was not statistically significant (P = .09). Retrogression analysis failed to show a correlation between the amount of energy necessary to produce the iridotomy and a decrease in endothelial cell density. Retrogression analysis also failed to show a correlation between the change in endothelial cell density and the time between the laser iridotomy and the performance of postoperative specular microscopy (one to 41 weeks).     

Contribution of the argon laser in iridotomy using the Yag laser

Yag laser iridotomy was performed immediately after argon laser application in 59 eyes with chronic angle closure glaucoma, occludable angle and secondary glaucoma. Postoperative intraocular pressure was elevated temporarily more than 5 mmHg on 86.4% of patients. Iris haemorrhages occurred in 17% of cases when laser Yag iridotomy was carried out with a power of 4 to 6 mJ. Prior argon laser seemed to prevent iris haemorrhages.     

Acute intraocular pressure response to argon laser iridotomy

Argon laser iridotomy (ALI) was performed in 50 eyes for prophylactic treatment of anatomically narrow iridocorneal angles and in 50 eyes for therapy of chronic angle-closure glaucoma. Intraocular pressure was increased 6 mmHg or more 1 to 2 hours after ALI in 19 of 50 eyes with anatomical narrow iridocorneal angles and in 23 of 50 eyes with chronic angle-closure glaucoma. Increases greater than 20 mmHg over baseline value occurred in 5 of 50 eyes with narrow iridocorneal angles and in 7 of 50 eyes with chronic angle-closure glaucoma. A clinically significant increase in intraocular pressure (defined as a pressure 30 mmHg or greater and 40% or more increased over the pre-laser value) occurred 1 to 2 hours after ALI in 11 of 50 eyes with narrow iridocorneal angles and in 17 of 50 eyes with chronic angle-closure glaucoma. There was no statistical difference (chi square P greater than 0.3) in the incidence of this complication in the two groups. Additional medical therapy was effective in lowering the acute laser-induced elevation in intraocular pressure. Patient diagnosis, patient demographics, preoperative glaucoma medication and laser treatment parameters did not predict which eyes would develop this complication. Eyes which did not have a clinically significant elevation in intraocular pressure 1 to 2 hours after ALI did not show a later increase at 24 hours.     

Corneal endothelial decompensation after argon laser iridotomy.

Focal corneal edema overlying the site of argon laser iridotomy followed by generalized corneal decompensation developed in six eyes of five patients. The average interval between the iridotomy and the development of focal edema was 3 years, with generalized edema appearing an average of 3.5 months later. Light, scanning and transmission electron microscopy of tissue removed at the time of corneal transplantation showed abnormalities characteristic of Fuchs' dystrophy in two patients. Possible contributing factors include episodes of intraocular pressure elevation, cornea guttata and the use of high total amounts of energy during laser iridotomy.     

Choroidal and retinal detachment following argon laser iridotomy

This case report examines another of the many complications resulting from argon laser iridotomy. The authors believe that choroidal and retinal detachment subsequent to argon laser iridotomy are a product of the exceptionally high cumulative energy used in the procedure and might result from changes induced in the chamber angle. Although the authors could not prospectively find any choroidal or retinal detachment in the patient, they think that it might occur subclinically and must be suspected in a pale iris if the energy used is high and/or if vision is transiently lowered during the postoperative period.     

Evaluation of phototoxic retinal damage after argon laser iridotomy

We performed several visual function tests in 17 eyes (ten patients) before and after argon laser iridotomy in an effort to detect diffuse photochemical damage to photoreceptors caused by exposure to the intense, blue-green light that is transmitted into the posterior segment as the iridotomy is created and enlarged. No change was detected in static threshold sensitivity in the central 30 degrees of the field (Octopus perimeter), color sensitivity (Farnsworth-Munsell 100-Hue test), or visual acuity. Contrast sensitivity showed a small increase at low spatial frequencies and a small decrease at high spatial frequencies. The latter change was small and not necessarily laser related, but precautions to limit laser exposure of the posterior pole are prudent.     

Low-energy linear-incision neodymium: YAG laser iridotomy versus linear-incision argon laser iridotomy. A prospective clinical investigation

When the Q-switched neodymium: YAG (Nd: YAG) laser is focused through the Wise 103-diopter (D) iridotomy-sphincterotomy lens (103-D lens) at low energy levels, the peripheral iris fibers can be cut individually across the iris tension lines to produce large iridotomies of controllable size. Thirty patients had linear-incision Nd:YAG laser iridotomy in one eye and linear-incision argon laser iridotomy in the other. Two-hour post-laser IOP rises averaged 7.33 mmHg for the Nd:YAG laser and 8.64 mmHg for the argon laser. The argon laser produced lens burns in 9 of 30 eyes, including 7 of 9 blue eyes. No lens damage occurred with the Nd:YAG laser. No corneal or retinal damage was seen with either laser. Local oozing of blood inhibited optical breakdown and required a pause before completion in 5 of 30 eyes with Nd:YAG iridotomy, including 4 of 6 dark brown thick irides. Because the iris fibers must be cut by direct contact with the laser plasma, serial cutting of iris fibers by multiple low-energy plasmas is safer than a single-shot, high-power plasma occupying the full thickness of the iris. Because it is effective and because it avoids the hazards of argon laser iridotomy and of high-power Nd:YAG laser iridotomy, linear incision Nd:YAG laser iridotomy is recommended as the safest method of iridotomy.     

Combined thermal-photodisruptive iridotomy using the argon and neodymium:YAG laser

With the combined thermal-photodisruptive laser technique a large iridotomy of controllable size can be performed without any major complications. Using the Wise 103 diopter contact lens, primary coagulation is performed with short-duration argon laser burns. Subsequently, multiple low-energy single pulses are applied with the Nd:YAG. The iris can thus be perforated step by step. Compared with the pure Nd:YAG laser technique, this procedure reduces the risk of bleeding. Compared with the pure argon laser technique, each iris can be perforated easily, regardless of its color and thickness. The present paper reports on experience gathered in a first group of 50 eyes.     

Effect of laser peripheral iridotomy using argon and neodymium-YAG lasers on corneal endothelial cell density: 7-year longitudinal evaluation

Purpose

To evaluate the changes in corneal endothelial cell density (ECD) over a 7-year period after laser peripheral iridotomy (LPI) using argon and neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers.

Study design

Retrospective case series.

Methods

Eyes that underwent prophylactic LPI using argon and Nd:YAG lasers were followed up for 7 years. Central corneal endothelial cells were observed by use of noncontact specular microscopy preoperatively and at 1 and 7 years postoperatively. Changes in ECD and the associations between preoperative ECD and the total energy of the Nd:YAG laser were evaluated.

Results

Fifty-one eyes of 51 patients were followed up for 7 years. The ECD significantly decreased after LPI (P < 0.049), and the reduction rate at 1 year after the surgery (1.69 ± 4.80%, 95% CI: 0.34%–3.04%) was significantly higher than the annual reduction rates after 1 year (0.17 ± 0.85%/y, P = 0.036, 95% CI: -0.07% to 0.41%). No association was found between the preoperative ECD and the total laser energy.

Conclusions

Long-term evaluation indicated that the reduction in ECD after argon-Nd:YAG laser LPI was present but small during the initial year and was negligible after 1 year.