Effect of Anterior Chamber Depth on the Development of Post YAG LASER Capsulotomy Macular Edema

 INTRODUCTION

Remaining lens epithelial cells growth and migration, epithelial mesenchymal transition, collagen deposition, and lens fiber formation are the primary causes of posterior capsular opacification. ¹

By producing a central aperture in the opaque posterior capsule, Nd: YAG laser capsulotomy has become the gold standard therapy for pseudophakia eyes with visibly significant PCO. ²

When using the Nd:YAG laser, a series of focused ablations are made in the posterior capsule, which results in an aperture through which light may pass. Despite the fact that Nd:YAG laser posterior capsulotomy is safe and effective, the reported vision-related complications include cystoid macular edema (CME), retinal detachment ³, damage to the IOL, iris hemorrhage, corneal edema, IOL subluxation, macular hole and exacerbation of localized endophthalmitis. ⁴

Nd: YAG laser posterior capsulotomy is known to cause temporary elevations in intraocular pressure (IOP); however, this is not permanent. ⁵ IOP rises following Nd: YAG capsulotomy due to diminished outflow capacity caused by capsular debris and vitreous particles floating in the anterior chamber blocking the trabecular meshwork's flow. ⁶ According to certain studies, IOP rise is more likely to occur at greater laser energies and higher laser pulse counts. A substantial increase in IOP might put the eyesight at risk. ⁷

Intraocular pressure may be increased by the Nd:YAG laser capsulotomy treatment if debris is deposited in the trabecular meshwork, trabeculitis develops as a result of the radiating "shock waves," neurovascular processes are activated, and angle-closure pupillary block occurs. ⁸

It is possible that the location of the IOL implant in the eye will change during this treatment, which may impair the patient's visual acuity. The patient's eyesight may need to be further refracted. As a result of disruption to the blood-aqueous barrier, macular edema is caused by movement and injury inside the vitreous cavity, as well as the release of inflammatory mediators therefrom. ^{9, 10}

It's known to cause retinal tears and detachments, with rates ranging from 0% to 3.6%. 11. Retinal tear and detachment following the laser's rupture of the anterior vitreous hyaloid is hypothesized by some to be the result of this process. ¹¹

Reproducible and exact measurements of macular thickness may be made using optical coherence tomography. Symmetric or only one part of the retina may be affected by the edema. Starting off as a single lesion, it frequently evolves to a more widespread form. ¹²

The aim of the Work was to evaluate correlation between anterior chamber depth (ACD) using Anterior segment OCT (AC-OCT) and assess macular thickness after YAG LASER capsulotomy using macular OCT.

PATIENTS AND METHODS

This prospective, cross-sectional study involved 20 eyes of 20 patients underwent uncomplicated phacoemulsification and developed posterior capsular opacification (PCO). They are collected from the Ophthalmology outpatient clinic of Sayed Galal Hospital. The study was performed in the Faculty of Medicine, Al-Azhar University at the period of six months from June 2021 to December 2021.

A cross-sectional controlled study in which AC-OCT was performed to detect the ACD then doing Macular OCT to detect macular thickness before YAG Laser Capsulotomy then doing YAG Laser Capsulotomy and follow up the patients with Macular OCT at first and third month to detect macular thickness changes after YAG and correlates these changes with AC depth of these patients.

Twenty eyes of 20 patients who undergone successful phacoemulsification without complications and developed posterior capsule opacification represented the target population of this study beside 20 eyes of 20 patients who undergone successful phacoemulsification without complications and without PCO. They all matched our inclusion criteria.

Inclusion criteria of the Patients: Adult subjects: Age ranged between 40 to 70 years, both sexes included, patients underwent uncomplicated Phacoemulsification, subjects had no extraocular or intraocular diseases, not very dense PCO allowing posterior segment imaging, normal healthy subjects, i.e., non-diabetic, cooperative patients for the procedure, normal clear cornea and able to perform a confirmed consent.

Exclusion criteria: Low age patients < 40 years, patients with complicated phacoemulsification, patients presenting with dense PCO affecting posterior segment imaging, patients with active ocular disease such as corneal ulcer, corneal opacities, viral or bacterial infection, patients with history of previous retinal surgery, patients with corneal opacities, corneal degenerations and corneal dystrophies, congenital ocular disease as staphyloma, keratoconus, microcornea, and megalocornea, glaucomatous patients or with elevated intraocular pressure, history of ocular trauma or chronic inflammation, patients with posterior segment disorders as diabetic retinopathy, age related macular degenerations, systemic vascular diseases, patients on medications affecting macula, patients with autoimmune diseases.

Methodology: Complete assessment was done for each patient including:

Full history taking: Personal history: name, age, gender, residence and occupation, past history: history of previous medications and history of previous ocular surgery and present history: Any patient's complaint, onset of the vision diminution, duration since surgery and progression of vision diminution.

Preoperative assessment: Uncorrected and best corrected visual acuity assessment using Snellen’s chart: unaided and best corrected, converted to decimal values, manifest refraction using the autorefractometer, slit lamp biomicroscopy to examine the anterior segment of the eye to exclude any corneal or lens abnormalities as corneal opacities, corneal dystrophy, corneal degeneration and degree of opacification, intraocular pressure measurement by Air puff tonometer(TOPCON), fundus examination: using slit lamp and 90D lens to exclude any posterior segment disorder, OCT of the macula: Image processing and segmented en-face OCT images using TOPCON TRITON PLUS and AC-OCT: for determination of anterior chamber depth.

Postoperative assessment: Visual acuity, slit lamp biomicroscopy, fundus examination, macular OCT imaging and AC-OCT.

Patients were scanned using a prototype OCTA device. The prototype is a swept-source OCT system with a wavelength of 1050 nm and a scan rate of 400 kHz. ¹³

Fig. 1: Topcon Triton plus OCT

Procedure Steps: YAG laser offset adjusted to 10 degrees to avoid damaging or pitting the intraocular lens implant, laser power started from 0.4 mj and was increased by 0.1 mj increments until clinical objective of micro-puncture posterior capsulotomy was achieved, small punctures 4-8 shots in each quadrant for a total of 16-32 punctures in whole circumference were done and size of each puncture was attempted to be as small as clinically possible.

Fig. 2: Microruptor 6 Nd: YAG laser.

Follow up: Complete evaluation of the patients especially measurement of the macular OCT and ACD was determined preoperatively and at the first week, first month and then at third month after YAG capsulotomy to find the relation between macular changes and ACD.

Ethical considerations: The study was conducted after approval of the protocol by the Local Research Committee and the Studies Committee as well as the Research Ethics Committee. An informed written consent was obtained from all patients.

Statistical Data Analysis: The statistical software SPSS version 20.0 was used to examine the data (SPSS Inc., Chicago, IL, USA). The Kolmogorov–Smirnov test was used to determine if the variables had a normal distribution. The mean standard error (SE) was used to divide the subjects into two groups: those with PCO (group #1) and those without (group #2). Multiple analyses of variance (ANOVA) with the Bonferroni correction were used to examine the differences between the two groups (post hoc comparisons). The correlation coefficient (r) between central macular thickness and SE and ACD was calculated using linear regression. For the research variables, Pearson correlation coefficients were also used.

RESULTS

χ2 = Chi square, t: paired t-test, SD: standard deviation.

Both groups were matched in age and sex with p value >0.05.

Table 1: Patients characteristics of the two studied groups

This study involved 20 eyes of 20 patients underwent uncomplicated phacoemulsification and developed PCO (group 1): they were 14 males (70%) and 6 females (30%) and another 20 eyes of 20 control subjects underwent uncomplicated phacoemulsification and did not have PCO, they were 12 males (60%) and 8 females (40%). The ages of group (1) ranged from 48 to 70 years with mean ± SD of 61.1 ± 5.36 years and the ages of the control group (2) was ranged from 40 to 62 years with mean of 55.3 ± 6.42 years. Table (1)

*P

Table (2): Characteristics of studied eyes in both groups at presentation

IOP was statistically insignificant (P >0.05), while BCVA, spherical error, spherical equivalent, axial length and CMT showed statistically considerable variation (P <0.05) in comparison between the two studied groups. Table (2)

CMT: Central macular thickness. P

Table 3: Anterior chamber parameters of the two studied groups at presentation

Comparison between high myope and emmetrope showed considerable reduction in retinal thickness and central macular thickness in high myopes group compared to emmetropic control eyes, it was represented in detail in comparison between each retinal quadrant. Table (3)

#: F-test for comparison between pre-Laser and last follow-up period. *P

Table 4: Comparison between different parameters before and after the procedure in patients with PCO, group (1)

The best corrected visual acuity, spherical error, and spherical equivalent improved after YAG-Laser capsulotomy and vision markedly improved at the last follow-up period (3 months) with statistically highly considerable variation between the two periods (p <0.001), while the axial length decreased during the follow-up period with statistically different  value between the two periods (p <0.05). Table (4)

#: F-test for comparison between pre-Laser and last follow-up period. P

Table 5: Comparison between anterior chamber depth and macular thickness before and after the procedure in patients with PCO, group (1)

Anterior chamber depth decreased gradually from pre-laser value to the last follow-up period (3 months) with statistically highly considerable variation between the two periods (p <0.001), while the central macular thickness is markedly elevated after laser, then decreased gradually till the end of the follow-up period with statistically highly significant value between the two periods (p <0.001). Table (5)