Effect of neodymium: yttrium aluminum garnet laser posterior capsulotomy on intraocular pressure

Neha Verma; Ashish K Ahuja

doi:10.4103/PAJO.PAJO_26_19

ORIGINAL ARTICLE

Year : 2020 | Volume : 2 | Issue : 1 | Page : 6

Effect of neodymium: yttrium aluminum garnet laser posterior capsulotomy on intraocular pressure

Neha Verma, Ashish K Ahuja
Department of Ophthalmology, Sant Parmanand Hospital, New Delhi, India

Date of Submission	30-Nov-2019
Date of Acceptance	28-Jan-2020
Date of Web Publication	24-Mar-2020

Correspondence Address:
Neha Verma
436, Civil Lines, Sardar Patel Hospital, Chhatra Sangh Bhawan, Gorakhpur - 273 001, Uttar Pradesh
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/PAJO.PAJO_26_19

Abstract

Objective: To find out whether there exists a correlation between the quantum of energy used and the amount of rise of intraocular pressure (IOP) following neodymium: yttrium aluminum garnet (Nd: YAG) laser capsulotomy.
Materials and Methods: A total of 110 patients who had undergone Nd: YAG laser posterior capsulotomy for the management of posterior capsule opacification with a minimum of 3 months following cataract surgery were enrolled after taking written informed consent. After detailed history and ocular examination, Nd: YAG laser capsulotomy was performed. Prelaser IOP was noted. Nd: YAG laser posterior capsulotomy was performed. Laser energy used was noted following which postlaser IOP was also recorded after 1, 2, and 4 h postprocedure. Paired t-test was used for the comparison of means of IOP and energy levels. Receiver operating characteristic analysis was used to predict the cut-off value of energy on the basis of change of IOP from baseline.
Results: The mean energy used in the Nd: YAG laser posterior capsulotomy procedure for all patients was 58.57 ± 34.63 mJ. The mean IOP at 1^st h follow-up was 15.32 ± 2.91 mmHg, at 2^nd h follow-up was 16.24 ± 3.23 mmHg, and at 4^th h follow-up was 16.18 ± 3.35 mmHg. At all three follow-ups, the mean change in IOP was found to be statistically significant (P < 0.001).
Conclusion: Postlaser IOP rise is minimal and transient; it varies with the amount of energy used.

Keywords: Intraocular pressure, laser capsulotomy, posterior capsular opacification

How to cite this article:
Verma N, Ahuja AK. Effect of neodymium: yttrium aluminum garnet laser posterior capsulotomy on intraocular pressure. Pan Am J Ophthalmol 2020;2:6

How to cite this URL:
Verma N, Ahuja AK. Effect of neodymium: yttrium aluminum garnet laser posterior capsulotomy on intraocular pressure. Pan Am J Ophthalmol [serial online] 2020 [cited 2023 Jun 3];2:6. Available from: https://www.thepajo.org/text.asp?2020/2/1/6/281369

Introduction

Cataract is the major cause of blindness in India accounting for about 62.6% among all causes of blindness.^[1] Cataract surgery is probably the most common ophthalmic surgical procedure being carried out throughout the world. Posterior capsular opacification (PCO) is a frequent complication of cataract surgery. It varies from 7% to 31%, 2 years postcataract surgery. Although the incidence of PCO varies among studies, the rates as high as 11.8% at 1 year after cataract surgery, 20.7% at 3 years, and 28.4% at 5 years have been reported.^[2] Neodymium: yttrium aluminum garnet (Nd:YAG) laser capsulotomy is a safe, noninvasive, and time-trusted procedure for the management of PCO.^[1] PCO occurring within 3 mm of the central posterior capsule affects visual acuity significantly.^[3]

Since 1980, Nd:YAG laser capsulotomy has become a standard treatment to improve visual acuity in pseudophakic patients with PCO.^[4],[5] Improvement in visual acuity after Nd: YAG laser capsulotomy in patients with significant PCO has been well documented.^[6],[7],[8] Improvements in glare and contrast sensitivity may also be important outcome measures for many patients.^{[9],[10],[11]} Although Nd: YAG laser capsulotomy is accepted as a standard treatment for PCO and has been found to be safe and effective, it is not without complications, some of which can be sight-threatening such as retinal edema and detachment.^[12]

It is important to evaluate the anterior- and posterior-chamber parameters before and after Nd:YAG laser capsulotomy because it can cause complications, such as elevation of intraocular pressure (IOP) and corneal injury.^{[13],[14],[15]} In our study, we tried to evaluate the correlation between the quantum of energy used during Nd:YAG laser capsulotomy for PCO after cataract surgery, with an objective to find out if there exists a correlation between the two, which would help us determine those patients who require prophylactic antiglaucoma drugs and a closer follow-up and avoid any inadvertent usage of antiglaucoma drugs in all pseudophakes undergoing laser capsulotomy.

Materials and Methods

This was a prospective observational study, carried out at the Department of Ophthalmology, Sant Parmanand Hospital, New Delhi, and involved 110 pseudophakic eyes with PCO following cataract surgery studied over a 12-month period after taking written informed consent from the patients and approval from the ethical committee.

Inclusion criteria

Patients with pseudophakic eye with visual impairment due to significant PCO following a minimum of 3 months of uneventful cataract surgery, with no other complications, were included in the study.

Exclusion criteria

Patients with glaucoma or any antiglaucoma medications
Cases with postoperative complications such as endophthalmitis
Any active ocular inflammation
PCO in aphakic eyes
Case who had undergone any anterior-segment laser procedure or any intraocular surgery other than cataract surgery
Uncooperative patients, e.g., patients with mental retardation or neurological problems<
Having baseline (prelaser) IOP ≥22 mm of Hg
Patients having any corneal abnormality or physical/mental limitation.

A total of 110 consecutive patients were recruited in this study. An evaluation of the patients requiring Nd:YAG laser capsulotomy was carried out before the procedure. Amount of total laser energy used was recorded. IOP was also recorded.

After thorough history and ocular examination including visual acuity, slit lamp biomicroscopy, and fundus and applanation tonometry, Nd:YAG laser capsulotomy was carried out using a Zeiss laser model VISULAS II PLUS. Only one eye underwent the procedure on 1 day. In case the capsulotomy was required in both the eyes, the second eye was undertaken independently and was recruited in the study to avoid any confounding factors related to the subject. Dilatation of the pupil was carried out using tropicamide 1%. The procedure was carried out after anesthetizing the eye with topical proparacaine hydrochloride 0.5%, while a capsulotomy size of 3 mm or more was considered adequate. Postlaser all patients were prescribed loteprednol etabonate 0.5% eye drops four times a day along with carboxymethylcellulose sodium 0.5% lubricating eye drops four times a day, beginning immediately after laser and for 1 week.

The postlaser IOP was recorded using Goldmann applanation tonometer at 1, 2, and 4 h.

Case definitions

Mild rise of IOP: Any elevation of IOP, <5 mm of Hg above the baseline prelaser IOP. For all considerations including data analysis, this was clubbed with no rise of IOP
Moderate rise of IOP: A rise of ≥5 mm of Hg above the baseline prelaser IOP
Severe rise of IOP: A rise of ≥10 mm of Hg above the baseline prelaser IOP.

The data were analyzed using Statistical Package for the Social Sciences, version 23.0 (IBM, USA). All data were reported as averages and standard deviations. Independent samples or paired t-test and ANOVA were used to compare the data recorded before and after capsulotomy. Receiver operating characteristic (ROC) analysis was used to predict the cut-off values of energy with respect to IOP change (from baseline to follow-up). A P < 0.05 was considered statistically significant.

Results

The mean age of the study sample was found to be 56.83 ± 8.14 years (ranging from 42 to 75 years), implying that the majority of patients were in their sixties. Regarding gender, 62 (56.4%) were males and 48 (43.6%) were females with a male-female ratio of 1.29:1. The mean time difference between cataract surgery and current procedure was 2.68 ± 1.34 years. The mean baseline (precapsulotomy) best-corrected visual acuity value was 0.539 ± 0.242 LogMAR, and the mean IOP value was 14.52 ± 2.86 mmHg [Table 1].

Table 1: Demographic and preoperative findings for all patients

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The elevation in IOP was recorded at 1, 2, and 4 h following Nd: YAG laser capsulotomy, and it was mostly found that the patients showed 1–5 mmHg rise in IOP [Table 2]. The mean IOP elevation with respect to time interval after laser capsulotomy measured at 1, 2, and 4 h was found to be highly statistically significant (P < 0.001) [Table 3]. The association between amount of energy used and rise in IOP at different follow-up intervals after Nd: YAG laser posterior capsulotomy was also found to be statistically significant (P < 0.05) [Table 4].

Table 2: Number of patients with intraocular pressure elevation after laser capsulotomy according to time interval

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Table 3: Mean intra ocular pressure elevation with respect to time interval after neodymium yttrium aluminum garnet laser capsulotomy

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Table 4: Association between amount of energy used and rise in intra ocular pressure at different follow up intervals after neodymium yttrium aluminum garnet laser posterior capsulotomy

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A positive significant correlation between change in IOP following posterior capsulotomy and total energy use was observed. The magnitude of this correlation was mild at 1 h (r = 0.35) and moderate at 2 h (r = 0.553) and 4 h (0.633) intervals [Figure 1].

Figure 1: Scatter plot showing correlation between energy used and intraocular pressure rise at different follow-up intervals

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ROC analysis was used to predict the cut-off value of energy on the basis of their IOP change from baseline [Table 5]. For ≥ 5 mm of Hg IOP from baseline, area under curve of energy at 1, 2, and 4 h after Nd: YAG laser posterior capsulotomy procedure was 0.655, 0.802, and 0.918, respectively. The optimal cut-off point of energy at 1, 2, and 4 h after procedure was 58.50, 65.0, and 71.0, respectively, for IOP rise from baseline. It was observed that YAG energy determination 4 h after procedure has high accuracy for the prediction of IOP rise[Graph 1], [Graph 2], [Graph 3].

Table 5: Receiver operating characteristic analysis showed that the optimal cutoff values of energy for all follow up

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Discussion

PCO causes glare, impairs contrast sensitivity, and remains a major concern of decreased vision after cataract surgery. The use of Nd:YAG laser has definitely simplified the treatment of PCO. It is an entirely noninvasive technique, has become popular for doing posterior capsulotomy, and has been established as a standard treatment for PCO replacing surgical capsulotomy.^[16]

Nd:YAG laser breaks the posterior capsule following a pressure wave created by infrared light of 1064 nm which is amplified and focused so that electrons are ripped away from nuclei to form energy plasma and corresponding shock wave.^[16] In our study of 110 cases, majority of the patients were males (62, 56.4%), mostly above 50 years of age; it was also the most common age group that underwent cataract surgery. A similar trend was noted by Shetty and Sridhar,^[1] who depicted 60% males and 40% females, and 68.6% of the studied patients were in the age group ranging 50–70 years. Kaur et al.^[16] and Havale et al.^[17] also reported a higher proportion of males over females in their respective studies. However, gender difference does not indicate any gender fondness neither for cataract surgery nor for PCO.

The mean age of the studied patients was found to be 56.83 ± 8.14 years, similar to Bhargava et al.,^[18] where the mean age was 55.6 ± 8.7 years. The mean time elapsed between cataract surgery and laser capsulotomy procedure was reported as 2.68 ± 1.34 years, similar to Khanzada^[19] where the mean period was 2.5 years, while Bhargava et al.^[18] reported this period to be 22.9 months. PCO development rates vary at different postcataract surgery durations, and the mean duration after cataract surgery might generally ranges from 2 to 3 years.^[2]

In our study, 81.8% of patients showed transient rise in IOP after 1 h of procedure, whereas after 2 h and 4 h of the procedure, it was 91.9% and 88.2% of patients showed transient rise in IOP, respectively. Similar to Flohr et al.^[20] and Mohammad et al.,^[21] they found IOP elevation in >75% and 84% of cases, respectively, in their studies. In the study by Kaur et al.,^[16] only 62.47% of patients showed transient rise in IOP after procedure. In this study, the mean IOP at 1^st h follow-up was 15.32 ± 2.91 mmHg, at 2^nd h follow-up was 16.24 ± 3.23 mmHg, and at 4^th h follow-up was 16.18 ± 3.35 mmHg, thus showing a mean increase of 0.80 ± 2.29, 1.72 ± 2.90, and 1.66 ± 3.04 mmHg from baseline, respectively. At all three follow-ups, the mean change in IOP was found to be statistically significant (P < 0.001). Similar trend was reported by Richter et al.^[22] This relatively lower rise in the present study could be attributed to reduced levels of energy used. In another study, it was observed that there was statistically significant increase in IOP at 1 and 4 h postlaser when higher energy was used.^[23] In the study by Barnes et al.,^[24] the change in IOP was also relatively lower. Compared to this in the present study during the entire evaluation period, the rise of >5 mmHg was seen to be maximum at 2 h when 18.2% of patients showed a rise of >5 mmHg. In the present study, >10 mm rise was observed in only 1 (0.9%) case at 4-h interval. When topical hypotensives are used, the rise in IOP could also be reduced. In a study by Singh,^[25] the rise of IOP from baseline to 1, 3, 5, and 24 h postprocedure was not found to be significant in the groups receiving ocular hypotensive drug. Shetty and Sridhar^[1] reported that almost all the patients had a rise in IOP 2 h postprocedure. Hence, IOP documentation of IOP 2 h postprocedure was observed to be more predictive of persistent IOP rise compared to immediate postprocedure IOP. In our study, the duration of IOP elevation study was only up to 4 h postoperative interval, and the reason for limiting this assessment only up to 4 h interval was because we had used a limited range of laser energy only.

In our study, the mean energy required for Nd:YAG laser posterior capsulotomy was 58.57 ± 34.63 mJ. Patil et al.^[23] observed almost similar findings and reported a mean energy used as 62.47 ± 33.65 mJ. In our study, the patients were divided into three groups, in maximum number of cases 46 (41.8%), 40–80 mJ was used with a mean energy 58.70 ± 11.84 mJ; in 24 (21.8%) patients, >80 mJ energy was used with mean 110.46 ± 29.59 mJ; and in rest of the patients, <40 mJ energy with a lowest mean energy 27.87 ± 7.08 mJ was used being highly significant (P < 0.01). In a study by Waseem and Khan^[26] the low-energy group was exposed to laser energies below 50 mJ with a mean energy of 36.46 ± 6.42 mJ while the high-energy group had IOP above 50 mmHg with a mean of 56.84 ± 2.65 mJ. In their study, they found rise of about 5.51 ± 1.58 mmHg in the high-energy group and 3.83 ± 1.84 in the low-energy groups.

Similar results were reported by Ari et al.^[27] were 58 ± 18 mJ and 117 ± 36 mJ energy were used among two groups of patients receiving 14–80 mJ and 84–200 mJ of energy, respectively. Kaur et al.^[16] also used similar mean energy levels among two study groups (38.01 ± 9.34 mJ and 62.46 ± 10.07 mJ.

In the present study, there is a relationship between the amount of energy used and rise in IOP at different intervals of follow-up; we observed that the mean rise in IOP was nominal for cases in which <40 mJ energy was used, followed by 40–80 mJ energy used, and maximum for cases in which >80 mJ total energy was used. We observed statistically significant association between energy used and rise in IOP (P < 0.05). The results of the present study showed that the frequency of “raised IOP” was associated with the high laser energy delivered to the eyes and must be expected to be greater in patients who receive excessive amount of YAG laser energy. Our results correspond with Kaur et al.'s^[16] study results as the prelaser mean IOP was 14.45 ± 2.52 mmHg which raised to 16.08 ± 3.69 mmHg at 1 h and peaked to 16.83 ± 3.69 mmHg by 2 h after laser capsulotomy procedure. Similarly, Ge et al.^[28] and Dawood et al.^[29] concluded transient IOP rise within 1.5–4 h and 1–3 h after laser capsulotomy procedure, respectively, in their study. Higher energy was required for higher grades of PCO. The possible mechanisms could be: More the energy used during the procedure, more particles were liberated from posterior capsular breakdown, thus clogging of angle of anterior chamber and subsequently increasing the IOP. In addition, the acoustic shock waves release inflammatory mediators that alter the trabecular meshwork and the aqueous dynamics causing IOP rise.

In the end, we would also like to lay emphasis on the fact that preventing the formation of PCO through a good cortical-cleaving hydrodissection is also very important. The use of hydrodissection during cataract surgery helps in easy removal of cortex and lens epithelial cells, thereby minimizing the chances of development of a PCO. Hence, this would prevent patients from being unnecessarily subjected to the complications of Nd:YAG capsulotomy.

Conclusion

Raised IOP is a frequent complication of Nd: YAG laser posterior capsulotomy. It depends on the amount of laser energy delivered to the eye during the procedure. The higher the energy used, the greater the rise in IOP.

Hence, it is recommended that each patient undergoing Nd: YAG laser posterior capsulotomy should receive minimum possible laser energy and should be followed up for raised IOP. Further, limiting the use of amount of energy levels (<50 mJ/sitting) during Nd: Yag laser procedures can prevent postlaser IOP spikes. This will prevent unnecessary use of antiglaucoma drugs in most patients.

Recommendations

It was difficult to compare different studies due to different techniques of cataract surgery and different intraocular lens implant materials, their designs, and the thickness of PCO. We recommend further studies with larger sample size and variable energy use with the same follow-up intervals as used in the present study to explore this relationship further.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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