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 Table of Contents    
ORIGINAL ARTICLE
Year : 2022  |  Volume : 15  |  Issue : 3  |  Page : 321-325  

A cross-sectional study on the complications of inferotemporal laser peripheral iridotomy


Department of Ophthalmology, Amrita School of Medicine, Amrita Hospital, Amrita Vishwa Vidyapeetham University, Kochi, Kerala, India

Date of Submission07-Jan-2021
Date of Decision22-Dec-2021
Date of Acceptance06-May-2022
Date of Web Publication02-Nov-2022

Correspondence Address:
Shreeya Pareshbhai Rughani
KJ Traders, Xiomi Store, Ground Floor, Perry Plaza, Near Alkapuri Flats, Sardarbaug, Zanzarda Road, Junagadh - 362 001, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ojo.ojo_8_21

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   Abstract 


PURPOSE: The purpose of this study was to identify the incidence of dysphotopsia and other associated complications after inferotemporal laser peripheral iridotomy (IT-LPI).
METHODS: This is a cross-sectional study on patients who underwent IT-LPI with neodymium: yttrium–aluminum–garnet laser who were followed up for a minimum of 3 months.
RESULTS: In our study, out of a total of 116 patients, new-onset dysphotopsia was reported in 6.03% and significant pain during the procedure in 12.93% of patients. Other complications noticed were photophobia in 29.31% (34/116), rise in intraocular pressure at the end of 3 months in 1.72%, pigment dispersion in 0.86%, epiretinal membrane formation in 04.31%, and cystoid macular edema in 1.72%. No patients had hyphema or diplopia.
CONCLUSIONS: The incidence of dysphotopsia following IT-LPI was relatively low in our study and was comparable to the superior PI under full lid cover from the literature. Although dysphotopsia rates were not superior, no patient developed hyphema, which could be due to the remoteness of the laser spot to the larger blood vessels located at 3 and 9 o'clock positions. Furthermore, the procedure was well tolerated as significant pain was reported by only less than a quarter of the patients. Hence, IT-LPI can be considered an easy to perform, safe, and comfortable procedure for the patient.

Keywords: Complications, dysphotopsia, inferotemporal, laser peripheral iridotomy, pain


How to cite this article:
Prathapan M, Rughani SP, Shyam P, Shah KN, Sujithra H, Pillai GS. A cross-sectional study on the complications of inferotemporal laser peripheral iridotomy. Oman J Ophthalmol 2022;15:321-5

How to cite this URL:
Prathapan M, Rughani SP, Shyam P, Shah KN, Sujithra H, Pillai GS. A cross-sectional study on the complications of inferotemporal laser peripheral iridotomy. Oman J Ophthalmol [serial online] 2022 [cited 2022 Dec 2];15:321-5. Available from: https://www.ojoonline.org/text.asp?2022/15/3/321/360425




   Introduction Top


Laser peripheral iridotomy (LPI), generally considered a safe procedure, is the current first-line management for pupillary block, with dysphotosia being a common postprocedural complaint. The old schoolteaching to reduce this has been the placement of LPI underneath the upper lid cover, but dysphotopsia has been observed to persist in spite of it. Literature shows a lower incidence of dysphotopsia but more pain with temporal PI compared to superior LPI.[1]

In this study, we are trying to identify the rate of dysphotopsia associated with an inferotemporal LPI (IT-LPI).


   Methods Top


This is a cross-sectional study on patients who underwent IT-LPI with neodymium: yttrium–aluminum–garnet (Nd: YAG) laser.

Inclusion criteria

  1. Primary angle-closure (PAC) disease:


    • PAC suspect (PACS)(≥180° iridotrabecular contact [ITC], normal intraocular pressure [IOP], and no optic nerve damage);
    • PAC (≥180° ITC with peripheral anterior synechiae [PAS] or elevated IOP, but no optic neuropathy);
    • PAC glaucoma (PACG) (≥180° ITC with PAS, elevated IOP, and optic neuropathy).


  2. Secondary angle-closure disease without retinal pathology:


    • Pseudoexfoliation glaucoma (PXFG).


Exclusion criteria

  • Visual acuity <6/60
  • Tubular fields
  • Other retinal pathologies.


Procedure

Before laser, age, gender, and corrected distance visual acuity were recorded for all patients. Antiplatelet drugs were not stopped before the procedure.

All patients were pretreated with pilocarpine 1% to achieve miosis, and proparacaine 0.5% eye drops for topical anesthesia.

All iridotomies were performed by a single person using an Abraham lens with hydroxypropyl methylcellulose as a coupling agent and were placed inferotemporally over iris crypts while avoiding the extreme peripheral crypt, using Nd: YAG laser between 7 and 8 o'clock in the right eye and between 4 and 5 o'clock in left.

Settings

Energy: 3 mJ; number of shots: 1–3 shots or more; Size of PI:150 microns.

All patients were prescribed prednisolone acetate 1% eye drops tapered weekly over 1 month from four times a day to once a day.

Patients were followed up at 1 month, 3 months, 6 months, 12 months, and then yearly once. On follow-up visits, the onset of any new dysphotopsia, headache, or photophobia post laser was enquired, and they were asked to grade the pain experienced during the LPI on a scale of 1–10 classified as mild, (1–3) moderate (4–6), and severe (7–10). Moderate-to-severe pain was considered significant pain.

Best-corrected distance visual acuity and IOP by applanation tonometry, PI patency, and gonioscopy were recorded on all visits. If required, repeat treatment was given.


   Results Top


In our study, 116 patients were included [Table 1].
Table 1: Baseline characteristics of patients

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An average duration of follow-up was noted to be of 9 months.

The most common indication requiring LPI was noted to be PAC, followed by PACG, PACS, and PXFG.

New-onset dysphotopsia was reported in a fairly minority of the patients, 6.03% (7/116) [Figure 1].
Figure 1: Incidence of dysphotopsia with inferotemporal LPI. LPI: Laser peripheral iridotomy

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A total of 41.38% (48/116) of patients experienced pain during the procedure. Of which, significant pain was experienced by only 12.93%, whereas 58.62% (68/116) of patients did not complain of any significant pain. Mild pain was reported by 28.44% (33/116), moderate by 10.34% (12/116), and severe by 2.59% (3/116) of the patients [Figure 2].
Figure 2: Grading of pain during LPI. LPI: Laser peripheral iridotomy

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Photophobia post-IT-LPI procedure was present in 29.31% (34/116) of the patients.

Our study looked at the IOP rise at the end of 3 months instead of 1 month to avoid those with steroid response. An increase in IOP (>5 mmHg from baseline) was recorded at 1.72% (2/116).

Pigment dispersion was seen only in one patient (0.86%).

The incidence of macular pathologies such as epiretinal membrane (ERM) formation was seen in a total of five patients (4.31%), and one patient (0.86%) had associated submacular detachment.

Cystoid macular edema (CME) was noted in a total of 1.72% (2/116) of the patients.

None of the patients in our study had post-LPI hyphema or diplopia.

[Figure 3] shows the incidence of various events postinferotemporal LPI in our study.
Figure 3: Incidence of various complications postinferotemporal LPI. LPI: Laser peripheral iridotomy

Click here to view



   Discussion Top


Aqueous humor produced from the ciliary body travels through pupil into the anterior chamber and exits the eye from the angle of the anterior chamber. All individuals have some amount of physiological resistance offered by the iridolenticular space to the movement of aqueous from the posterior chamber to the anterior chamber, an exaggeration of which causes pupillary block glaucoma. Conventionally, YAG PI has been the first line of management for PACG and PAC, which is still being followed in practice by most of the ophthalmologists in India. However, a recently done EAGLE study suggests that clear lens extraction in such cases is more efficacious and safer, and it can be considered the first line of treatment in PACG and PAC patients.[2]

LPI establishes a bypass for aqueous into the anterior chamber, thereby neutralizing the chamber differential pressure which causes reversal of the convex iris configuration, flattening out the iris, thereby opening the peripheral angle. The need for further antiglaucoma medications or trabeculectomy depends upon the post-PI IOP levels and status of the optic disk.

Dysphotosia post-LPI is not uncommon morbidity experienced by patients which is seen as a horizontal or vertical shaded light in a linear or curved fashion which comes and goes with variation in the lid and eye position as well as the incident ray of light. The classical old schoolteaching to reduce this complication has been the placement of LPI underneath the upper lid cover, validation being that the light is directly entering though the LPI opening was causing it. However, over time, its persistence has been noted even in a properly placed superior PI. Few recent studies have shown that the temporal location of PI has a lower incidence of dysphotopsia. Furthermore, previous studies report the incidence of pain more with temporal LPI as compared to superior LPI.[1]

The optics underlying the development of dysphotopsia is the triangular lake of tear film formed at both upper and lower eyelid margins which acts as a base-up prism for the incident ray of light, with the light being refracted toward the base of this tear prism at the lid margin. Hence, the light will be redirected superiorly by the upper lid tear meniscus. Depending upon the position of the eyelid and the size of the tear meniscus, the light can be refracted superiorly through the superior LPI placed just behind the eyelid with the tear meniscus just below it. Patients will be more symptomatic in such cases as compared to a fully exposed PI. When light passes through a small opening like LPI, it gets diffracted or spread in an annular fashion before striking the retina. A longer path will result in more spread, hence making it more defocused on the retina. In the case of superior LPI, light travels a shorter path and gets focused on the superior peripheral retina which can be perceived by the patient as opposed to the light traveling through the temporal iris will follow a linear path to strike the temporal posterior pole with this path being longer and hence producing a defocused image on retina which is less appreciated by the patient. This can probably explain the difference in the incidence of dysphotopsias with superior versus temporal LPI.

A well-accepted practice is to avoid the areas where the lid bisects the PI. When trying to place PI superiorly, since there is greater variation in lid position and palpebral fissure among individuals, choosing the correct superotemporal location becomes a challenge. Doing a PI right at 12 o'clock increases the chance of intraprocedural bleed, which may move in front of the pupils, thus producing visual difficulty for the patient. Temporal location avoids the trouble of lid bisecting the LPI, but placing PI right at temporal location (9 o'clock for the right eye and 3 o'clock for the left eye) produces greater intraprocedural pain and higher incidence of hyphema due to the proximity to the long ciliary artery and nerve. The inferotemporal location gives the advantage of lesser incidence of dysphotopsia, hyphema, and intraprocedural pain due to its remoteness to the long ciliary vessels and nerves.

The primary objective of our study was to look at the dysphotopsia rate, which was noted to be 6.03%. The reported incidence from the literature ranges from 2.4% to 10.7%. The rates from superior PI are 8.4% to 10.7%.[1],[3] The incidence of fully exposed superior PI was 6.5%.[1]

The study by Vera et al. found a lower incidence of dysphotopsia from a temporal placed PI.[1]

A more recent study by Srinivasan et al. demonstrated that approximately 1 in 11 patients experienced ≥1 new dysphotopsia 2 weeks after LPI, with no difference between superior versus nasal/temporal LPI (8.4% vs. 9.5%).[3]

Our rates of dysphotopsia were similar to Vera et al. rate of 6.5% and Spaeth et al. rate of 8.9%, with completely covered superior PI.[1],[4] This shows no definitive difference in the rate of occurrence of dysphotopsia between a superior versus the temporal or inferotemporal location of PI.

We also looked at the symptomatic course of those who had dysphotopsia where 3/7 (42.85%) patients had a reduction over 3-month time. However, there is no available literature to compare the rates of dysphotopsia and its reduction over time with that of ours.

Literature suggests that the incidence of pain is more with temporal LPI as compared to superior LPI.[1] Our study clearly demonstrates superiority of inferotemporal location over the temporal location in terms of pain during the procedure as significant pain was observed in the minority (12.93%) only which can be due to the LPI being away from the long ciliary nerve, while 58.62% (68/116) had no significant pain during the procedure. There are no available data on this from literature to compare our results with.

Similarly, no patient developed hyphema in our study. From literature, the rates of hyphema were 8.9%–34.6%, with temporal location having a higher incidence than superior.[1],[5],[6],[7],[8] This again gives IT location superiority over the temporal location.

In literature, the incidence of IOP spike post-LPI has been 9.8%–30% which can likely be due to pigment dispersion or new-onset PAS formation.[5],[6],[7] It is fairly low in our study, that being 01.72% (2/116).

Furthermore, PAS formation was noted in 03.03% (1/33) of PACS patients.

Breaks in retinal pigment epithelium and release of pigments are known to be responsible for ERM formation, which can explain the occurrence of ERM postLPI due to pigment post laser. Ocular inflammation postLPI may explain the occurance of CME in nondiabetics. Hence, it should be kept in mind for a patient coming with a drop in vision or metamorphopsia post-LPI.

Our incidence of repeat LPI was 3.40% (4/116) which is consistent with that in the literature of 2%–9% [Table 2].[5],[6],[9]
Table 2: Comparisons between postinferotemporal laser peripheral iridotomy complication rates from that in the literature

Click here to view


In our study, all the inferotemporal LPI were performed by a single person. Hence, results can be considered more consistent. Furthermore, our study looked at the severity of pain during the LPI procedure which has not been studied earlier.


   Conclusions Top


The incidence of dysphotopsia following IT-LPI was relatively low in our study and was comparable to the superior PI from the literature. Although dysphotopsia rates were not superior, no patient developed hyphema, which could be due to the remoteness of laser spots to the larger blood vessels located temporally. Furthermore, the procedure was well tolerated as significant pain was reported by only less than a quarter of the patients. Hence, IT-LPI can be considered an easy to perform, safe, and comfortable procedure for the patient.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Vera V, Naqi A, Beloway 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. 1
    
2.
Azuara-Blanco A, Burr J, Ramsay C, Cooper D, Foster PJ, Friedman DS, et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): A randomised controlled trial. Lancet 2016;388:1389-97.  Back to cited text no. 2
    
3.
Srinivasan K, Zebardast N, Krishnamurthy P, Abdul Kader M, Raman GV, Rajendrababu S, et al. Comparison of new visual disturbances after superior versus nasal/temporal laser peripheral iridotomy: A prospective randomized trial. Ophthalmology 2018;125:345-51.  Back to cited text no. 3
    
4.
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. 4
    
5.
Jiang Y, Chang DS, Foster PJ, He M, Huang S, Aung T, et al. Immediate changes in intraocular pressure after laser peripheral iridotomy in primary angle-closure suspects. Ophthalmology 2012;119:283-8.  Back to cited text no. 5
    
6.
Schwartz LW, Moster MR, Spaeth GL, Wilson RP, Poryzees E. Neodymium-YAG laser iridectomies in glaucoma associated with closed or occludable angles. Am J Ophthalmol 1986;102:41-4.  Back to cited text no. 6
    
7.
Golan S, Levkovitch-Verbin H, Shemesh G, Kurtz S. Anterior chamber bleeding after laser peripheral iridotomy. JAMA Ophthalmol 2013;131:626-9.  Back to cited text no. 7
    
8.
Kam JP, Zepeda EM, Ding L, Wen JC. Resident-performed laser peripheral iridotomy in primary angle closure, primary angle closure suspects, and primary angle closure glaucoma. Clin Ophthalmol 2017;11:1871-6.  Back to cited text no. 8
    
9.
Lewis R, Perkins TW, Gangnon R, Kaufman PL, Heatley GA. The rarity of clinically significant rise in intraocular pressure after laser peripheral iridotomy with apraclonidine. Ophthalmology 1998;105:2256-9.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2]



 

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