Study of Variation in Intraocular Pressure Spike (IOP) Following Nd- YAG Laser Capsulotomy

Neodymium-doped yttrium aluminum garnet (Nd: YAG) laser treatment in ophthalmology: a review of the most common procedures Capsulotomy and Iridotomy

Nowadays, lasers are used in various medical fields. Ophthalmology was the first medical specialty to utilize lasers in patient treatment and still remains the leading medical field that uses laser energy for both therapeutic and diagnostic purposes. The neodymium: yttrium-aluminum-garnet (Nd: YAG) laser is one of the most common lasers used in ophthalmology. It is a solid-state laser with a wavelength of 1064 nm that works on the principle of photodisruption. Since its introduction in ophthalmology over 40 years ago, it has found various applications, mainly for procedures where cutting or disruption of ocular tissue is required. Compared to surgical alternatives, the use of Nd: YAG lasers on ocular tissue is minimally invasive. In this review, we focus on the two most common ophthalmic applications of Nd: YAG laser - laser peripheral iridotomy and posterior capsulotomy. The history of the techniques, current trends, potential complications, and the prognosis for future use is discussed.

Intraocular pressure increase after Nd:YAG laser capsulotomy and anterior segment optical coherence tomography analysis

This study is to determine whether post-procedure intraocular pressure (IOP) increase is associated with the anterior chamber angle in cases of Neodymium: yttrium-aluminum garnet (Nd: YAG) laser capsulotomy. The study included 51 eyes with posterior capsule opacification. Initial IOP values of the patients were compared with IOP values without intraocular pressure-lowering administration at the end of the 1st hour, 1st day, 3rd day, and 7th day after Nd:YAG laser capsulotomy. The anterior segment angle configuration was evaluated using anterior segment optical coherence tomography analysis without dilatation before the procedure. The anterior chamber angle (ACA) and angle opening distances of 500 and 750 μm (AOD500 and AOD750) in the nasal and temporal quadrants were examined. The mean pre-laser IOP value only increased significantly at 1st hour post-laser (13.02 ± 3.02 mmHg vs 14.16 ± 4.07 mmHg, p = 0.016). In eyes with ACA below 40° in both the nasal and temporal quadrants, mean IOP increased significantly at 1st hour post-laser (p = 0.025 and p = 0.032, respectively), while it was not significant in eyes with ACA above 40° (p > 0.05). No correlation was found between ACA, AOD500, and AOD750 values and IOP changes at the first hour (p > 0.05). Except for the first hour after Nd:YAG laser capsulotomy, no significant increase in IOP was observed. This elevation was higher in eyes with ACA less than 40°. In patients with a narrow ACA, first-hour follow-up may be beneficial in terms of susceptibility to increased IOP.

Acute Effects of Neodymium-Doped Yttrium Aluminum Garnet Laser Capsulotomy on Anterior Segment Parameters in Capsular Bag Distension Syndrome

Background: Capsular bag distension syndrome (CBDS) can be effectively treated using either Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser capsulotomy or surgery. Assessing anterior segment, particularly immediately after Nd:YAG laser capsulotomy, could provide clinically relevant information on ocular dynamics, refractive changes, and complication mechanisms, especially in late postoperative CBDS. Objective: To explore the acute effects of Nd:YAG laser posterior capsulotomy on anterior segment parameters in late postoperative CBDS. Methods and results: In this study, 20 patients underwent Nd:YAG laser posterior capsulotomy after cycloplegia, during which milky-white fluid material migrated into the anterior vitreous. Anterior segment parameters were assessed before and immediately after laser using Scheimpflug-Placido topographer. The main outcome measures were differences in best-corrected visual acuity (BCVA), aqueous depth (AqD), anterior chamber volume (ACV), iridocorneal angle (ICA), corneal volume (CV), and central corneal thickness (CCT) at the baseline versus at immediately after laser. The mean age and duration since surgery for CBDS presentation were 70.25 ± 6.21 and 6.15 ± 1.31 years, respectively. The AqD, ACV, ICA, and spherical equivalent increased significantly compared with baseline (4.18 vs. 4.02 mm, p = 0.001; 177 vs. 173.55 mm3, p = 0.004; 51.15° vs. 50.15°, p = 0.023; -1.00 vs. -2.00 D, p = 0.003, respectively). These changes were also associated with significantly improved BCVA an hour after capsulotomy [0.2 (0.05-0.2)] relative to baseline [0.3 (0.2-0.5)], (p = 0.001). CCT and CV decreased nonsignificantly; horizontal AC diameter and K1 and K2 increased nonsignificantly (p > 0.05). Conclusions: Nd:YAG laser posterior capsulotomy appears to be an effective CBDS treatment for acutely improving vision, potentially due to immediate refractive changes caused by altered anterior segment parameters.

"Comparing outcomes of advanced nurse practitioners to ophthalmologists performing posterior YAG capsulotomy, a six-year study of 6308 eyes"

PURPOSE

To primarily report the baseline characteristics and visual acuity (VA) outcomes of advanced nurse practitioners (ANP) compared to ophthalmologists following YAG posterior capsulotomy (YAGPC). We secondarily looked to characterise the risk factors that lead to a repeated YAGPC.

METHOD

Retrospective consecutive case series of 6,308 eyes attending the Birmingham and Midlands Eye Centre.

RESULTS

ANPs performed 33.1% of YAGPC compared to 66.9% ophthalmologists. Compared to ophthalmologists, ANPs performed YAGPC in lower proportion of patients with ocular co-morbidities (p < 0.001) and had lower proportion of patients requiring further YAGPC compared to ophthalmologists (p < 0.001). Median pre, post-operative and LogMAR gain in VA of 0.48 (IQR 0.30-0.78), 0.18 (IQR 0.10-0.40) and 0.30 (0.08-0.48) LogMAR units, respectively. Multivariate regression showed that ANPs had a significantly lower rate of repeat YAGPC compared to ophthalmologists even when adjusting for age, ethnicity, training grade and ocular co-morbidities. No difference in visual outcomes was found between operator grade and ethnicity on multivariate analysis.

CONCLUSION

YAGPC leads to excellent visual outcomes. ANPs can deliver safe and effective YAGPC.

Micro-Computed Tomography (µCT) as a Tool for High-Resolution 3D Imaging and Analysis of Intraocular Lenses: Feasibility and Proof of the Methodology to Evaluate YAG Pits

INTRODUCTION

Posterior capsule opacification (PCO) is the most frequent late sequelae after successful cataract surgery. Neodymium:yttrium aluminum garnet (Nd:YAG) laser capsulotomy is considered the gold standard and a well-accepted, safe, and effective measure in treating PCO. However, iatrogenic damage of the intraocular lens (IOL) due to inappropriate focusing is a quite common side effect. These permanent defects (YAG pits) can critically affect overall optical quality.

METHODS

In this laboratory study, we used the micro-computed tomography (µCT) technique to obtain high-resolution 3D images of the lens and the YAG pits.

RESULTS

To the best of our knowledge, this is the first description of a detailed analysis of IOLs with µCT technology. This non-destructive technique seems to be ideal for comparative studies, measuring dimensions of the damage, and visualizing shooting channels within the material.

CONCLUSION

µCT is excellently suited to examine an IOL in detail, analyze optics and haptics in three dimensions, and to describe all kinds of changes within the IOL without damaging it.

Evaluation of Nd:YAG laser capsulotomy results in patients who underwent cataract extraction and intraocular lens implantation with the endocapsular phacoemulsification method

Background/Aim: Posterior capsular opacification (PCO) is a common complication that develops after cataract surgery, and it can be treated neodymium-doped yttrium aluminum garnet (Nd:YAG) laser capsulotomy. In this study, we aimed to investigate the effects of different intraocular lenses (IOLs) on the development of posterior capsule opacification (PCO), to determine the time between surgery and Nd:YAG laser capsulotomy, and to evaluate the efficacy, effectiveness, and complications of capsulotomy in patients who underwent cataract surgery with the phacoemulsification method and subsequently developed PCO. Methods: The cohort study included one eye of each of 153 cases (63 males, 90 females) who underwent cataract surgery with the phacoemulsification method in our clinic from August 1, 2006, through August 1, 2008, and subsequently developed PCO. According to the type of IOL implanted, the cases were divided into three groups: polymethylmethacrylate IOL (Group 1), hydrophilic acrylic IOL (Group 2), and hydrophobic acrylic IOL (Group 3). The control examinations of the patients who underwent Nd:YAG laser capsulotomy were undertaken before capsulotomy and at the first week, first month, and third month after capsulotomy. Results: Visual acuity improvement was detected in 96.7% of the 153 cases. It was determined that 9.1% of the cases had an intraocular pressure (IOP) increase of more than 5 mmHg at the third hour after capsulotomy and approached baseline values at the end of 1 week. The mean   total energy used in all the cases was 37.20 (14.70) mjl. The mean total energy used in 14 patients with an IOP elevation of above 5 mmHg was 71.07 (10.59) mjl. Nd:YAG laser capsulotomy was performed at an average of 6.29 (4.91) months in Group 1, 7.81 (4.35) months in Group 2, and 17.7 (12.35) months in Group 3. After capsulotomy, clinically significant cystoid macular edema was observed in 1.9% of the cases, IOL damage in 3.9%, and vitreous hemorrhage in 0.6%. Conclusion: In this study, the incidence of PCO development was found to be lower in the patients who underwent hydrophobic acrylic IOL implantation; therefore, this type of lens should be preferred for implantation. Although Nd:YAG laser capsulotomy is an outpatient treatment method that can be applied quickly and can increase visual acuity, it can also lead to complications. To eliminate most of these complications, it would be beneficial to minimize the energy used during the laser procedure.

Evaluating impact of Nd: YAG laser associated defects on optical quality of hydrophilic and hydrophobic intraocular lenses using visualization of light propagation and USAF test targets

BACKGROUND

Neodymium:yttrium aluminum garnet (Nd:YAG) laser capsulotomy is a well-accepted, safe, and effective measure in the treatment of posterior capsule opacification. However, iatrogenic intraocular lens damage is a relatively common side effect that happens due to inappropriate focusing during the procedure. This experimental study analyzes the impact of YAG-pits to obtain qualitative information.

METHODS

Acrylic, monofocal hydrophilic and hydrophobic intraocular lenses (IOLs) with 6.0 mm optic and the with the same power (21D) were studied. First, all measurements were done with unmodified IOLs. Damage was intentionally created, performing YAG-pits (n = 5) in the central area of the lens optic (3.0 mm) using a photodisruption laser with the same energy level of 1.8 mJ. To simulate the cruciate pattern, the 5 defects were created in a cross shape within the 3.0 mm optical zone. Afterwards, all laboratory measurements were repeated: These included the United States Air Force (USAF) resolution test chart to study the imaging performance of the IOL, light field measurements to show the course of the rays behind the IOL and the modulation transfer function (MTF) measurements were analyzed.

RESULTS

Evaluating USAF showed that unmodified lenses produced a sharper image. Damaged lenses led to a more blurred image and to the impression of a lower contrast with a kind of halo/glare effect. The light field measurement showed that YAG-pits led to a kind of dispersion and scattering effect, which was higher in hydrophobic IOLs. MTF showed a deterioration in damaged hydrophilic and hydrophobic IOLs, respectively.

CONCLUSION

Our experimental study confirms that YAG-pits can reduce imaging quality of intraocular lenses. These defects behave as a new Huygens source, distribute a spherical wave that additionally illuminate the background of the USAF target. It can be assumed that material properties of the IOL (water content, refractive index) play an important role and affect results. The impact level is strongly dependent on the number, size and position of YAG-pits within the optic.

LIMITATION

Only monofocal IOLs have been investigated so far, further tests with various IOL optics have to follow. In addition, simulating the circular pattern of YAG capsulotomy is necessary.

Comparison of Anterior Capsule Polishing on the Rate of Neodymium: YAG Laser Capsulotomy After Two Multifocal Intraocular Lens Implantation

Purpose

To compare the impact of anterior capsule polishing (ACP) during cataract surgery on the rate of neodymium: YAG (Nd: YAG) laser capsulotomy in pseudophakic eyes with two multifocal intraocular lenses (MIOLs).

Methods

Data were collected on patients who underwent cataract surgery and implanted segmental refractive MIOLs (SBL-3, Lenstec) or diffracted MIOLs (AT LISA tri 839MP, Carl Zeiss Meditec). The participants were divided into ACP and non-ACP groups based on whether the anterior capsule was polished. The primary outcome measure was whether Nd: YAG capsulotomy was performed during the 3 years follow-up. We used Kaplan–Meier survival curves to determine the time from IOL implantation to Nd: YAG laser capsulotomy.

Results

ACP and non-ACP groups comprised 70 and 60 eyes, respectively. One year postoperatively, 7.14% of ACP group eyes and 8.33% of non-ACP group required Nd: YAG laser capsulotomy (P &gt; 0.99). After 2 years, it was 24.29 and 18.33%, respectively (P = 0.52), while after 3 years, it reached 30.0 and 28.33% (P = 0.85). No distinct difference existed in the probability of using Nd: YAG laser in both groups evaluated using Kaplan-Meier survival curves (P = 0.81). Patients with diffractive MIOLs (AT LISA tri 839MP) implantation were more likely to require Nd: YAG laser capsulotomy (P &lt; 0.01).

Conclusion

Polishing the anterior capsule had no remarkable effect on reducing the rate of Nd: YAG laser capsulotomy following phacoemulsification in MIOLs. Patients with diffractive MIOLs implantation had a high probability of requiring Nd: YAG laser capsulotomy.

Corneal Endothelial Changes Following Early Capsulotomy Using Neodymium:Yttrium-Aluminum-Garnet Laser

We aimed to survey whether the timing of neodymium:yttrium–aluminum–garnet (Nd:YAG) laser capsulotomy would alter the corneal endothelial morphology and density. A retrospective cohort study was conducted, and 48 patients with unilateral posterior capsular opacity (PCO) and Nd:YAG laser capsulotomy performance were enrolled. The participants were divided into the early Nd:YAG group (timing ≤ 12 months, n = 20) and late Nd:YAG group (timing > 12 months, n= 28) depending on elapsed months between phacoemulsification and Nd:YAG laser capsulotomy. Endothelial cell density (ECD), coefficient of variant (CV), hexagonality (HEX), and central corneal thickness (CCT) between the two groups were collected. A generalized estimate equation was conducted to evaluate the corneal endothelial parameters between the two groups with an adjusted odds ratio (aOR) and 95% confidence interval (CI). The CDVA was improved after treatment in both groups (both p < 0.001). Chronically, ECD in the early group was significantly decreased one week after treatment (2221.50 ± 327.73/mm² vs. 2441.55 ± 321.80/mm², p < 0.001), which recovered to 2369.95 ± 76.37/mm² four weeks after the treatment but was still lower than the preoperative status (p < 0.001). In addition, the HEX percentage showed a significant reduction at four weeks after treatment (p = 0.028). The ECD in the early group was significantly lower than that in the late group (aOR: 0.167, 95% CI: 0.079–0.356, p = 0.003) in both week 1 (p < 0.001) and week 4 (p = 0.004) after laser treatment. In conclusion, the early application of Nd:YAG laser capsulotomy within one year after cataract surgery may be the reason for postoperative ECD decrement without known etiology.

The effect of retaining intact posterior capsule in congenital cataract surgery in children aged 4-8 years

Background

The present study sought to observe the effect of retaining intact posterior capsule in congenital cataract surgery in children aged 4–8 years.

Methods

This is a retrospective case control study. Seventy-seven children (130 eyes) aged from 4 to 8 years who underwent cataract surgery were divided into two groups. In Group A, 50 eyes underwent phacoemulsification, intraocular lens implantation and posterior capsule capsulotomy combined with anterior vitrectomy. In Group B, 80 eyes underwent cataract phacoemulsification and intraocular lens implantation. The postoperative visual acuity and the rate of complications were compared.

Results

In all patients, cataract surgeries were performed evenly without intraoperative complications. The follow-up time ranged from 6 months to 42 months. No apparent visual axis opacity was detected in group A during the follow-up. By the last visit, apparent visual axis opacity was detected in 31 eyes (38.75%) in group B. Among them, 9 eyes (29.03%) with mild posterior capsule opacification (PCO) were treated with Nd:YAG laser, 3 eyes (9.68%) with thick proliferative membranes were treated with posterior capsule capsulotomy combined with anterior vitrectomy and proliferative membranes in 19 eyes (61.29%) were completely aspired and the posterior capsule was retained. During follow-up, only 2 (6.45%) eyes had PCO recurrence and were treated with Nd:YAG laser. The visual acuity was significantly higher than that before surgery in all patients.

Conclusions

For older children, the incidence of PCO will be low even if intact posterior capsule is retained. Either Nd:YAG laser or surgical treatment for PCO will be able to maintain good vision.

Study of Intraocular Pressure following Neodynium Yttrium Aluminium Garnet Laser Capsulotomy with the Use of Brimonidine: A Descriptive Cross-sectional Study

Introduction:

Posterior capsular opacification is a common complication after cataract surgery. Neodynium Yttrium Aluminium Garnet laser capsulotomy is still the preferred treatment for posterior capsular opacification. This study was done to determine the use of Brimonidine eye drop in preventing the rise of intraocular pressure post-Neodynium Yttrium Aluminium Garnet laser capsulotomy.

Methods:

A descriptive cross-sectional study was conducted in Lumbini eye institute and research center, Bhairahawa, Nepal, in 200 eyes with posterior capsular opacification using Brimonidine from Feb 1, 2019, to July 30, 2019. The Institutional Review Committee approved the study with approval number 0237. A convenient sampling method was used. Pre-capsulotomy best-corrected visual acuity, slit-lamp examination of the anterior segment, and dilated fundus examination were done. Intraocular pressure was measured with Goldmann Applanation Tonometer. Post capsulotomy patients were evaluated after one hour, two hours, and two weeks for intraocular pressure and any complications. The statistical analysis was done using Statistical Package of Social Sciences version 20.0 statistical analysis software. The descriptive statistical analysis of the study was done after the collection of the data.

Results:

Mean age of patients at presentation was 61.61 ±SD 1.09. The mean intraocular pressure following Neodynium Yttrium aluminum garnet laser capsulotomy using brimonidine at 1 hour was 12.73±3.3 mmHg. and two hours was 11.98±3.2 mmHg. The mean energy per pulse was 2.3 ±SD 0.3 mJ. The mean duration of posterior capsular opacification from cataract surgery was 22.28 weeks.

Conclusions:

Neodynium Yttrium Aluminium Garnet laser capsulotomy had lower intraocular pressure after the Brimonidine eye drop procedure. The maximum mean reduction in intraocular pressure was observed after two hours.

Analysis of YAG Laser-Induced Damage in Intraocular Lenses: Characterization of Optical and Surface Properties of YAG Shots

PURPOSE

To assess differences in neodymium:yttrium aluminum garnet (Nd:YAG)-induced defects in hydrophilic and hydrophobic intraocular lenses (IOLs) and describe optical and surface properties of YAG shots/pitting. Describing and measuring the iatrogenic produced defects should achieve higher awareness on this topic and change the mindset of such a trivial procedure to be proceeded with more caution and calmness in the future.

MATERIALS

Twelve IOLs from different manufacturers made of hydrophilic and hydrophobic materials were evaluated before and after treatment with the Nd:YAG laser. Microscopy and environmental scanning electron microscopic (ESEM) images were used to visually analyze the defects. Additionally, wavefront measurements were taken for power mapping and Raman spectroscopy was performed. Vertical and horizontal dimensions of the defects were analyzed and compared, and Raman line scans assessed the changes in the chemical structure in the defect area of the IOL.

RESULTS

Microscopically, pitting of the surface could be observed in both lens types. Defects in hydrophobic lenses appeared bigger and were visible with less magnification than in hydrophilic lenses. Similar results were obtained with ESEM images where the defects in hydrophobic IOLs seemed to be frayed while defects in hydrophilic IOLs were of circular shape. Raman spectroscopy revealed deeper defects in hydrophobic lenses. Vertical dimensions of the defects were statistically significant (p = 0.036) and greater in hydrophobic materials while horizontal dimensions did not reach significance (p = 0.056). The area of chemical changes was greater than the visible defect area and smaller in hydrophilic than that in hydrophobic materials.

CONCLUSION

Nd:YAG seems to have greater impact on hydrophobic IOL materials as that damage was greater and more frayed than that in hydrophilic materials. Moreover, there seems to be larger, distinctive damage area in IOLs (with chemical changes in the material) than that is visually recognizable. Therefore, a very cautious approach is recommended when performing capsulotomy, as defects in the surface structure can occur. This might come along with problems in quality of vision in monofocal and primarily premium IOLs (multifocal, enhanced depth of focus, and toric IOLs), dependent on the size, dimension, and position in the IOL. YAG capsulotomy should not be considered trivial but should be carried out with precision and without time pressure, just like surgery itself.

Effect of anterior capsule polish on visual function: A meta-analysis

PURPOSE

To investigate the relationship between anterior capsule polish and visual function.

METHODS

Data were obtained from Pubmed, Embase, Web of Science, WanFang, VIP and CNKI up to the end of May 2018, without any date or language restrictions for trials. The modified Jadad scale and the newcastle-ottawa scale were used to assess the quality of included studies. Uncorrected visual acuity (UCVA) and posterior capsule opacification (PCO) were used as outcome variables. Data on anterior capsule polish were pooled using weighted, random-effect meta-analysis.

RESULTS

One randomized controlled trial and 4 observational cohort studies involving 2533 patients were included in the analyses. There was a statistically significant difference of UCVA (OR 1.92, 95% CI 1.41-2.61) between the polish group and the control group, indicating that anterior capsule polish improved UCVA. Further studies with continuous data also suggested that anterior capsule polish was associated with good UCVA (MD 0.11, 95% CI 0.06-0.16). Posterior capsule opacification rate for 1-year or longer follow-up were extracted for 2561 eyes in 3 studies. Posterior capsule opacification rate was lower in the anterior capsule polish group according to summary odds ratio on PCO rate (OR 0.42 95% CI 0.24-0.73).

CONCLUSIONS

Anterior capsule polish prevents complication of modern cataract surgery and benefits on visual function in short term follow-up period.