Correlation Between Extent of Preexisting Organic Angle Closure and Long-term Outcome After Laser Peripheral Iridotomy in Eyes With Primary Angle Closure

Lasers in Glaucoma: an Overview

Lasers have been in use as a treatment modality of glaucoma for more than last four decades. Each passing year has added newer dimensions to the existing laser technologies enhancing their safety and efficacy profile. This has become possible due to continuous research and innovations with proper understanding of the mechanism of action of different variety of lasers as treatment options. Each category of glaucoma has different underlying pathologies. Adequate knowledge and understanding of indications, limitations and hazards of these laser procedures are must before their application for improvising outcome. Recent years have witnessed a revolution this field. A thorough literature search was conducted in PubMed, Medline, the Cochrane Library Database, EMBASE, and Scopus and Google Scholar until May 2020 using the keywords, and all the articles pertaining to the relevant topics were included in this review. Purpose of this review is to summarize the important laser procedures currently in use for managing glaucoma along with updating the readers with recent advances in laser technologies, their extended applications and also analyzing possible future implications.

Lasers in glaucoma

While lasers have been used for many years for the treatment of glaucoma, proper indications and use of the procedures need to be considered before their application. This review summarizes the important laser procedures in Glaucoma.

Laser peripheral iridotomy versus laser peripheral iridotomy plus laser peripheral iridoplasty in the treatment of multi-mechanism angle closure: study protocol for a randomized controlled trial

BACKGROUND

China has the largest burden of primary angle-closure glaucoma (PACG) worldwide. The mechanism of the angle closure is complex and includes pupillary block and non-pupillary block. Currently, opinion is that laser peripheral iridotomy (LPI) alone is not sufficient to prevent disease progression. Laser peripheral iridoplasty (LPIP) is an alternative and effective way of widening the angle recess in eyes that are affected by primary angle closure (PAC). However, it is not known if greater benefit would be achieved using LPI plus LPIP for PAC with multiple mechanisms (MAC). Thus, the aim of this study is to demonstrate if LPI plus LPIP would be more effective than single LPI in controlling the progression of PAC with multiple mechanisms, based on ultrasound biomicroscopy (UBM) classification. A secondary aim is to determine whether or not this would result in the use of less medication and/or prolong the time to antiglaucoma surgery.

METHODS

This multiple-mechanism angle-closure study will comprise a 3-year, multicenter, randomized, parallel-group, open-label, superiority trial, the aim of which will be to evaluate the safety and efficacy of LPI plus LPIP versus LPI for PAC. It is anticipated that 240 adults, diagnosed with PAC (the mechanism of angle closure will be assessed by UBM and it will be determined whether or not it involves multiple mechanisms) will be recruited from ten ophthalmic centers in China. Participants will be randomly allocated to receive either single LPI or LPI plus LPIP. Participant assessment will be designed to test the rate of disease progression and who will be followed up for 3 years. The primary outcome will be the disease progression rate and a comparison will be made between the LPI and LPI plus LPIP groups using Pearson's χ² test. Logistic regression analysis will be performed to account for the central effect.

DISCUSSION

If the LPI plus LPIP is found to significantly decrease the rate of PAC progression, this intervention could potentially be a standard therapy to be used to treat PAC when multiple mechanisms are involved in angle closure. Subsequently, this would have the potential to delay the rate of PAC progression to PACG and delay the time to the administration of antiglaucoma medication or trabeculectomy surgery.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02613013 . Registered on 24 November 2015. In fact, the study was due to start in late October 2015, however, there were no patients recruited in October, and when we registered at ClinicalTrials.gov on 5 November 2015, we received suggestions on the English translation of our protocol from the PRS Team at Clinicaltrial.gov, so the final successful registration date was on 24 November 2015.

Changes in Anterior Segment Morphology After Laser Peripheral Iridotomy in Acute Primary Angle Closure

PURPOSE

To evaluate the anterior segment biometric changes measured by anterior segment optical coherence tomography (AS-OCT) in acute primary angle closure (APAC) after laser peripheral iridotomy (LPI).

DESIGN

Prospective interventional study.

METHODS

In this clinic-based study, 52 eyes of 52 patients with resolved APAC attack who underwent LPI were enrolled. Subjects underwent complete ophthalmic examination and AS-OCT imaging before and 6 weeks after LPI. Anterior chamber depth (ACD), anterior chamber area (ACA), iris thickness (IT), iris area, iris curvature, lens vault (LV), anterior vault, angle opening distance (AOD500, AOD750), and trabecular iris space area (TISA500, TISA750) were measured in qualified images and compared before and after LPI. A linear mixed-model analysis was performed for potential predictors of change in AOD750. Main outcome measure was change in AOD750 after LPI.

RESULTS

The mean age of participants was 60.7 ± 9.2 years. Mean angle width (Shaffer grade) changed from 0.25 ± 0.34 at baseline to 1.22 ± 0.86 after LPI (P < .001). However, 25 nasal angles (48.0%) and 28 temporal angles (53%) had iridotrabecular contact after LPI. All angle parameters (AOD500, AOD750, TISA500, TISA750; P ≤ .03), ACD (P = .001), and ACA (P < .001) increased significantly after LPI. Iris curvature and LV were reduced (P = .01 for both) after LPI, but there was no significant change in IT and iris area. After multivariate analysis, pre-LPI AOD750 was the only factor associated with change in AOD750 (β = -0.992, P = .02). Exaggerated LV, defined as LV greater than one-third of the anterior vault (sum of LV and ACD), was present in 61.5% of the cases (32 eyes). The extent of change in angle parameters was not significantly different between groups with and without exaggerated LV after LPI.

CONCLUSION

This study confirms that LPI results in a significant increase in the angle width, ACD, and ACA as well as flattening of the iris in APAC eyes. The extent of angle deepening is inversely related to baseline angle width. The lens shifts posteriorly after resolution of attack, especially in those with greater lens vault.

Peripheral yttrium aluminium garnet (YAG) iridotomy versus phacoemulsification in primary angle closure: prospective comparative study

PURPOSE

A study was designed to determine and describe the changes induced in the anterior segment of the eye and the intraocular pressure (IOP) after laser peripheral iridotomy (LPI) versus phacoemulsification in primary angle closure suspects (PACS) and primary angle closure (PAC).

METHODS

Forty-seven eyes (47 patients) with Shaffer gonioscopy 0-II were included and split into 2 groups: cataract surgery (n=29) or LPI (n=18), depending on the lens sclerosis and visual acuity. Tonometry, gonioscopy, funduscopy, and automated measurements of the anterior chamber by Pentacam were performed before the intervention, and one and 3 months after the technique.

RESULTS

Phacoemulsification reduces IOP after one and 3 months (P<.01). LPI reduces IOP after 3 months (P<.04), and after one month (P<.38). IOP was 16.2mmHg (SD: 3.59) in the phacoemulsification group vs. 16.83mmHg (SD: 2.36) in the LPI group after one month (P=.4), and 15.52 (SD: 2.95) vs. 16.05 (SD: 2.46) in the third month (P=.5). There were no significant differences in the antiglaucoma drugs. Shaffer gonioscopy grading was greater in the phacoemulsification group vs. in the LPI group one and 3 months after the intervention (P=.01). The highest difference between both techniques was found in the superior quadrant. The anterior chamber depth, angle and volume by Pentacam were wider in the phacoemulsification group after one and 3 months (P<.01).

CONCLUSIONS

Although phacoemulsification and LPI could both be effective techniques in the prevention of pupillary block in PAC, faster and greater amplitude of the angle and the anterior chamber can be obtained after phacoemulsification than after LPI.