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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 2  |  Page : 155-159

Effect of position on the safety and efficacy of neodymium-doped: Yttrium aluminium garnet laser peripheral iridotomy in patients with primary angle-closure disease


Department of Ophthalmology, J J M Medical College, Davangere, Karnataka, India

Date of Submission25-Sep-2020
Date of Decision02-Nov-2020
Date of Acceptance03-Nov-2020
Date of Web Publication21-Aug-2021

Correspondence Address:
Dr. Anitha S Maiya
Department of Ophthalmology, J J M Medical College, Davangere - 577 004, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_152_20

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  Abstract 


Purpose: The aim is to evaluate the safety and efficacy of neodymium-doped: yttrium–aluminum–garnet laser peripheral iridotomy (LPI) in the superior versus inferior quadrant in the treatment of primary angle-closure (PAC) disease. Design: Randomized, prospective, single-masked, comparative clinical study. Materials and Methods: Patients with PAC or PAC suspects were recruited and randomized to receive LPI in the superior or inferior quadrant in both eyes. Patients were masked to the location of treatment in each eye. The main outcome measures assessed were patency of iridotomy, laser parameters, complications, and visual symptoms between the two groups at 1 week and 1 month after the laser intervention. Results: A total of 100 patients were recruited, 50 into each group. The mean age was 51.46 ± 7.91 years. Average intraocular pressure (IOP) measurements before LPI was 18.24 ± 5.37 mm Hg and 18.6 ± 5.63 mm Hg in superior LPI and inferior LPI eyes, respectively. After LPI, average IOP was 17.4 ± 3.31 mm Hg and 17.1 ± 3.13 mmHg in superior LPI and inferior LPI eyes, respectively. Inferior LPIs required less use of mean total laser energy (P = 0.001) and less number of laser shots (P = 0.016) to perforate the iris tissue. There was a lower incidence of iris bleeding and focal corneal damage at the time of treatment; a lower postlaser iritis and lower need for PI enlargement in the inferior LPI group. All the iridotomies were patent at 1 month follow-up. There was no statistically significant difference between the two groups in terms of the dysphotopsias and visual symptoms experienced after the LPI (P = 0.122). Conclusions: LPI in the inferior quadrant appears to be a safe and efficient alternative to superior LPI with fewer complications in the treatment of PAC disease. Dysphotopsias and visual symptoms following inferior LPI are similar to superior LPI.

Keywords: Dysphotopsias, laser peripheral iridotomy, neodymium: yttrium–aluminum–garnet laser, primary angle-closure suspect, primary angle closure


How to cite this article:
Maiya AS. Effect of position on the safety and efficacy of neodymium-doped: Yttrium aluminium garnet laser peripheral iridotomy in patients with primary angle-closure disease. Kerala J Ophthalmol 2021;33:155-9

How to cite this URL:
Maiya AS. Effect of position on the safety and efficacy of neodymium-doped: Yttrium aluminium garnet laser peripheral iridotomy in patients with primary angle-closure disease. Kerala J Ophthalmol [serial online] 2021 [cited 2021 Dec 5];33:155-9. Available from: http://www.kjophthal.com/text.asp?2021/33/2/155/324216




  Introduction Top


Laser peripheral iridotomy (LPI) with neodymium-yttrium-garnet laser is considered a standard treatment in patients with primary angle-closure (PAC) disease. It is performed in patients with narrow occludable angles to relieve the pupillary block by balancing the pressure between the anterior and posterior chambers. This can reduce the risk of acute and chronic angle-closure glaucoma. It has largely replaced surgical iridectomy as a simple, noninvasive outpatient procedure without the risks and complications of invasive surgery.[1],[2],[3] The complications associated with LPI include transient blurred vision, hyphema, anterior uveitis, the transient rise of intraocular pressure (IOP). Severe and sight-threatening complications such as corneal decompensation, cataract, and retinal detachment, although rare, have been reported after LPI.[4],[5],[6],[7],[8]

Conventionally, LPI is performed in the superior quadrant so that it is covered by the upper eyelid. Several studies have found superior LPI to be associated with dysphotopsias and visual symptoms in 2.7%–4% of patients.[9],[10],[11],[12] Inferior quadrant LPI is used widely in patients with silicon oil tamponade to prevent pupillary block.[13] There are few studies in the literature which have compared the safety and efficacy of LPI performed in the superior and inferior quadrants in patients with PAC glaucoma. A recent study by Ahmadi et al. and associates have found inferior LPI to be an efficient method of preventing pupil block with fewer complications.[14]

The purpose of our study was to evaluate the safety and efficacy of neodymium: yttrium–aluminum–garnet (Nd: YAG) LPI performed in the superior versus inferior quadrant in the treatment of PAC disease in phakic patients. The main outcome measures assessed were patency of iridotomy, laser parameters, complications, and visual disturbances postiridotomy between the two groups.


  Materials and Methods Top


This prospective, randomized, single-masked study was performed with the approval of the Institutional Ethical Committee. All PAC patients and PAC suspects (PACS) seen during the study period between June 2017 and December 2018 were invited to participate in the study. The inclusion criteria were patients older than 18 years with PACS/PAC posted for LPI who were willing to participate in the study, follow the study protocol and attend the required study follow-up visits. We excluded eyes with PAC glaucoma since we noted a gross difference in terms of best-corrected visual acuity (BCVA) and IOP from the eyes with PACS and PAC. Patients were excluded if they had any previous intraocular surgery, any active intraocular inflammation, or a history of acute angle-closure glaucoma. Before the laser procedure, age, gender, corrected distance visual acuity were recorded. All the patients underwent a comprehensive ophthalmic evaluation, including corrected distance visual acuity, slit-lamp examination, Goldmann applanation tonometry, gonioscopy, and undilated fundus examination. Patients with PAC who had high IOP were started on topical antiglaucoma medications and posted for LPI after normalization of IOP.

Patients were randomized to receive LPI in the superior or inferior location in both eyes by simple randomization. Patients were masked to the location of the LPI performed in each eye. The LPI was performed using the neodymium-yttrium-garnet laser using an Abraham iridotomy lens (Ocular Instruments Inc., Bellevue, Washington, USA). All patients received Pilocarpine 2% eye drops (three applications 10 min apart) 1 h before the procedure and Brimonidine 0.2% eye drops (single application) half an hour before the procedure. The superior LPIs were performed in the supero-temporal quadrant with an attempt to place it as peripheral as possible and under the upper eyelid. Inferior LPI was performed in the inferotemporal quadrant between 6 and 8 o' clock position (for right eyes) and 4 and 6 o' clock positions (for left eyes). The laser spots were applied at the base of iris crypts while avoiding the iris vessels. LPI in both eyes were performed sequentially in the same visit. Intraoperative data collected included laser energy, number of laser shots, and occurrence of any complications. The patients received a single application of Brimonidine 0.2% eye drops after the LPI and IOP was recorded 1 h after the procedure. All patients were put on topical steroid eye drops qid for 1 week.

Patients were followed up after 1 week and 1 month after the laser procedure. At each visit, the BCVA, IOP, gonioscopy, slit-lamp examination and fundus evaluation was performed. The location, size, and patency of the LPI, its distance from the limbus, presence of hyphaema, iritis, corneal damage, cataract was noted. Patients were enquired about the onset of new linear dysphotopsias, glare, haloes or any other visual disturbances at each follow-up visit.

One eye of each patient was included for statistical analysis. In patients with bilateral disease, the right eye was included for analysis.

Statistical analyses were performed using the Statistical Package for the Social Sciences version 15 (IBM, Chicago, Illinois, USA). Paired t-tests were used to compare the laser parameters. The Chi-square test was used for all other analyses. Significance was set at P < 0.05.


  Results Top


A total of 114 patients were eligible for recruitment into the study, among whom 109 patients underwent the intervention. Our study protocol mandated that each patient received the LPI in either the superior or inferior quadrant in both eyes. Patients in whom this could not be followed were excluded. We included 100 patients who underwent the correct treatment in both eyes and completed their 1-month follow up. Nine patients could not receive LPI in the same quadrant as the randomization protocol and hence were excluded. The baseline demographic and clinical characteristics of these patients are listed in [Table 1].
Table 1: Baseline clinical characteristics of the study patients

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Of the 100 patients, 78 patients had PACS and 22 patients had PAC [Table 1]. The IOP before LPI was 18.24 ± 5.37 mmHg in the superior group and 18.6 ± 5.63 mmHg in the Inferior LPI group. After the LPI, the IOP was 17.4 ± 3.31 mmHg in the superior group and 17.1 ± 3.13 mmHg in the inferior group. The difference in the IOP was not statistically significant.

There was no statistically significant difference in the mean laser energy per shot used (superior: 3.29 ± 0.23 mJ vs. inferior: 3.31 ± 0.16 mJ; P = 0.6149). However, there was a statistically significant difference between the two groups in the total energy (superior: 36.78 ± 10.5 mJ vs. inferior: 21.13 ± 7.32 mJ; P = 0.001) and the number of laser shots (superior: 10.55 ± 8.64 vs. inferior: 6.45 ± 2.25; P = 0.0016) required to perforate the iris.

There was no significant difference between the two groups in the presence of iris bleeding (P = 0.629), focal corneal damage (P = 0.307), or postlaser iritis (P = 0.249), although these complications were slightly higher in the superior LPI group [Table 2]. Eight patients in the superior group and 2 patients in the inferior group required retreatment for enlargement of the LPI, which was done at the 1st week follow-up. This difference was statistically significant (P = 0.0453).
Table 2: Laser parameters and postlaser complications

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All the LPI were patent at the end of 1 month.

In both, the groups, dysphotopsias and glare were the visual disturbances reported following the LPI. Dysphotopsias were reported by three patients in the superior LPI group. The LPI was completely covered by the eyelid in one patient and partially covered in two patients among these two patients in the superior LPI group. Seven patients in the inferior LPI group had visual symptoms in the form of seeing fine lines (three patients) and glare (four patients). The LPI was completely uncovered in six patients and partly covered in 1 among the seven patients reporting visual disturbances in the inferior LPI group. However, there was no statistically significant difference between the two groups in terms of the visual symptoms experienced after the LPI (P = 0.122). Since the number of patients reporting visual disturbances were few, a significant difference was not established between the two groups in terms of the number of laser shots or total energy used.


  Discussion Top


Pupillary block is a significant mechanism causing angle-closure glaucoma. Nd: YAG laser iridotomy to relieve the pupillary block is safe and effective in treating or preventing angle-closure glaucoma.[15],[16],[17]

Although LPI is routinely performed in the superior quadrant (superotemporal or superonasal quadrant) there may arise certain situations where we may need to perform it in the inferior quadrant such as significant corneal opacities, absence of crypts in the superior quadrant, inability to perforate iris in the superior quadrant and silicone oil tamponade in retinal surgeries. LPI in the inferotemporal quadrant offers several advantages like ease of access to the LPI site and availability of the superior quadrant in case of significant hyphema (occurring during the LPI) obscuring the inferior iris.

In our study, we found that inferior LPI was easy to perform, required less number of shots and lesser total energy to perforate the iris compared to the superior LPI. The rate of intraoperative and postoperative complications was also less in the inferior LPI group. These findings correlate with the study by Ahmadi et al., who have also found inferior LPI to be an efficient technique. Lower laser energy utilized during LPI reduces the incidence of corneal endothelial damage, postoperative rise of IOP, and postlaser iritis.

Many studies have reported the occurrence of dysphotopsias and other visual symptoms like glare, haloes, blurry vision following superior LPI, which can be a cause significant disability and concern.[9],[10],[11],[14],[18] In a recent study by Vanessa and associates,[18] 10.7% of patients with superior LPI demonstrated new linear dysphotopsias and were 3.6 times more likely to develop visual symptoms. Surprisingly, new linear dysphotopsias were four times more common in superior LPI that were partially or completely covered by the eyelid. This is in contrast to the previous knowledge that superior placement of LPI, ensuring complete lid coverage, can avoid dysphotopsias. In our study, there was no difference in the occurrence of visual symptoms in between the two groups.

The limitations of this study were small sample size, lack of long-term follow-up and the fact that we did not elicit a history of visual symptoms before performing LPI which could have helped us in detecting new-onset dysphotopsias after LPI.


  Conclusions Top


The results of this study may suggest that inferior LPI is a safe and efficient alternative to superior LPI. The low incidence of postoperative dysphotopsias and visual symptoms is an additional advantage. It may be ideal to customize the position of LPI to the individual patient based on ethnicities and eyelid position. A study with a larger sample size and longer follow-up is required to confirm the findings of this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Lee JR, Choi JY, Kim YD, Choi J. Laser peripheral iridotomy with iridoplasty in primary angle closure suspect: Anterior chamber analysis by pentacam. Korean J Ophthalmol 2011;25:252-6.  Back to cited text no. 1
    
2.
Boey PY, Singhal S, Perera SA, Aung T. Conventional and emerging treatments in the management of acute primary angle closure. Clin Ophthalmol 2012;6:417-24.  Back to cited text no. 2
    
3.
Ang LP, Higashihara H, Sotozono C, Shanmuganathan VA, Dua H, Tan DT, et al. Argon laser iridotomy-induced bullous keratopathy a growing problem in Japan. Br J Ophthalmol 2007;91:1613-5.  Back to cited text no. 3
    
4.
Drake MV. Neodymium: YAG laser iridotomy. Surv Ophthalmol 1987;32:171-7.  Back to cited text no. 4
    
5.
Hodes BL, Bentivegna JF, Weyer NJ. Hyphema complicating laser iridotomy. Arch Ophthalmol 1982;100:924-5.  Back to cited text no. 5
    
6.
Khodadoust AA, Arkfeld DF, Caprioli J, Sears ML. Ocular effect of neodymium-YAG laser. Am J Ophthalmol 1984;98:144-52.  Back to cited text no. 6
    
7.
Meyer KT, Pettit TH, Straatsma BR. Corneal endothelial damage with neodymium: YAG laser. Ophthalmology 1984;91:1022-8.  Back to cited text no. 7
    
8.
Berger CM, Lee DA, Christensen RE. Anterior lens capsule perforation and zonular rupture after Nd: YAG laser iridotomy. Am J Ophthalmol 1989;107:674-5.  Back to cited text no. 8
    
9.
Chung RS, Guan AE. Unusual visual disturbance following laser peripheral iridotomy for intermittent angle closure glaucoma. Graefes Arch Clin Exp Ophthalmol 2006;244:532-3.  Back to cited text no. 9
    
10.
Spaeth GL, Idowu O, Seligsohn A, Henderer J, Fonatanarosa J, Modi A, et al. The effects of iridotomy size and position on symptoms following laser peripheral iridotomy. J Glaucoma 2005;14:364-7.  Back to cited text no. 10
    
11.
Weintraub J, Berke SJ. Blurring after iridotomy. Ophthalmology 1992;99:479-80.  Back to cited text no. 11
    
12.
Congdon N, Yan X, Friedman DS, Foster PJ, van den Berg TJ, Peng M, et al. Visual symptoms and retinal straylight after laser peripheral iridotomy: The Zhongshan angle-closure prevention trial. Ophthalmology 2012;119:1375-82.  Back to cited text no. 12
    
13.
Madreperla SA, McCuen BW 2nd. Inferior peripheral iridectomy in patients receiving silicone oil. Rates of postoperative closure and effect on oil position. Retina 1995;15:87-90.  Back to cited text no. 13
    
14.
Ahmadi M, Naderi Beni Z, Naderi Beni A, Kianersi F. Efficacy of neodymium-doped yttrium aluminum garnet laser iridotomies in primary angle-closure diseases: Superior peripheral iridotomy versus inferior peripheral iridotomy. Curr Med Res Opin 2017;33:687-92.  Back to cited text no. 14
    
15.
Robin AL, Pollack IP. Argon laser peripheral iridotomies in the treatment of primary angle-closure glaucoma: Long-term followup. Arch Ophthalmol 1982;100:919-23.  Back to cited text no. 15
    
16.
Gieser DK, Wilensky JT. Laser iridectomy in the management of chronic angle-closure glaucoma. Am J Ophthalmol 1984;98:446-50.  Back to cited text no. 16
    
17.
Tomey KF, Traverso CE, Shammas IV. Neodymium-YAG laser iridotomy in the treatment and prevention of angle closure glaucoma. A review of 373 eyes. Arch Ophthalmol 1987;105:476-81.  Back to cited text no. 17
    
18.
Vera V, Naqi A, Belovay GW, Varma DK, Ahmed II. Dysphotopsia after temporal versus superior laser peripheral iridotomy: A prospective randomized paired eye trial. Am J Ophthalmol 2014;157:929-35.  Back to cited text no. 18
    



 
 
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  [Table 1], [Table 2]



 

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