FREQUENCY OF ACUTE RISE OF INTRAOCULAR PRESSURE FOLLOWING YAG LASER POSTERIOR CAPSULOTOMY.
KEY WORDS: Intraocular Pressure; Nd:Yag laser posterior capsulotomy; Posterior Capsular Opacification.
Posterior capsular opacification (PCO) is the most frequent complication of cataract surgery.1-3
Incidence of PCO is about 18-50% by two years post-operatively.4 Postoperative capsular opacification is a multifactorial physiological consequence of cataract surgery. Opacification involving the central posterior capsule has a significant impact on high- and low-contrast acuity and low-contrast sensitivity. The proliferation, migration and abnormal differentiation of residual lens epithelial cells and fibers in the capsular bag have been implicated in the pathogenesis of posterior capsule opacification. The incidence and severity of PCO correlates to the use of surgical techniques, intraocular lens (IOL) optic edge designs and IOL materials.
Advances in surgical techniques, IOL materials, and designs have reduced the PCO rate to quite an extent but it is still a significant problem.3 Posterior capsular opacification referred to as 'secondary cataract' or 'after cataract', develops over the clear posterior capsule a few months to a few years after an uneventful cataract surgery. Posterior capsular opacification results from the growth and abnormal proliferation of lens epithelial cells on the capsule at the time of cataract surgery. These cells migrate to the posterior capsule, where they approach the central visual axis and cause visual-axis obscuration, resulting in dimness of vision. The PCO has two forms, fibrous and pearl. Sometimes, a combination of both is also found.
Clinically, it is seen as a wrinkling on the posterior capsule at the site of fusion of the anterior and posterior capsules. A histological examination of the fibrous PCO shows extracellular matrix accumulation and the presence of elongated myofibroblast cells positive to vimentin and [alpha]-smooth muscle actin. Standard treatment of PCO consists of making an opening in the central part of posterior capsule. The Neodymium: Yag (Nd:Yag) laser has been used for about 35 years to treat Posterior Capsular O pacification.
The complications of this procedure are raised intraocular pressure (IOP), corneal damage, ruptured anterior vitreous face, retinal detachment, cystoid macular edema, IOL damage, iris hemorrhage, uveitis, macular hole, posterior subluxation of the IOL into the vitreous cavity, and backward movement of the IOL with resultant anterior chamber deepening.5-7
The raised IOP is the most common complication amongst the complications. Different proposed mechanisms that has been given for the pressure rise following Nd: Yag laser treatment include the deposition of inflammatory cells and debris in the trabecular meshwork, forward movement of vitreous and trabecular meshwork damage by laser shock waves that causes decrease drainage capacity.8 This acute IOP increase may be high enough to cause loss of vision to hand motion or light perception only or become persistent to cause visual field defects.9
A similar local study reported that raised IOP was noted in 53 (35.81%) cases while IOP remained normal in 95 (64.19%) cases.10 Another study reported acute rise in IOP was seen up to 8.3%.11
Although previously, studies were conducted on this particular topic reporting a wide range of raised IOP i.e. from 8.3%-35.8% 10, 11 following Nd: Yag laser posterior capsulotomy for PCO in pseudophakic patients. In our setup, no such study was conducted so we planned this study so that we can find the exact frequency of acute raised IOP in our patients and treatment modalities to be considered to prevent severe visual loss due to raised IOP. The raised IOP is most common complication following Nd: Yag laser treatment10. Different proposed mechanisms include the deposition of inflammatory cells and debris in the trabecular meshwork, forward movement of vitreous and trabecular meshwork damage by shock waves produced by laser that causes decrease drainage capacity12. This acute IOP increase may be high enough to cause loss of vision to light perception or become persistent to cause visual field defects13.
The objective of this study was to determine the frequency of acute rise of IOP following Neodymium-Yttrium Aluminum Garnet (Nd:Yag) laser posterior capsulotomy.
MATERIALS AND METHODS
This descriptive, cross-sectional study was conducted in the Department of Ophthalmology, Hayatabad Medical Complex, Peshawar, Pakistan, which is a one of tertiary eye care center in Khyber Pakhtunkhwa, from July 2016 to December 2016. Sample size of 325 patients was calculated with 95% confidence level, 3% margin of error and taking acute rise in IOP in 8.3% patients under WHO software for sample size determination. Sampling technique was consecutive, non-probability. Inclusion criteria were all patients having significant PCO after uneventful cataract surgery with intra ocular lens implant. Exclusion criteria were patients having glaucoma, corneal disease, diabetic retinopathy and inflammatory disease, dislocated IOL, history of trabeculectomy and retinal detachment surgery.
After obtaining approval from postgraduate medical institute ethical committee, data was collected from Out-patient department. The purpose, procedure and possible complications were explained to every patient. Informed consent was taken from the patients. The demographic variables were sex, age in years and age-groups (20-39, 40-70). Research variable was presence of acute rise of IOP following yag laser capsulotomy (yes, no). Pre-laser assessment included slit lamp examination and recording of IOP with Goldmann applanation tonometer. The Q-switched Nd: yag laser was used to make a hole in the opacified posterior capsule by following standard procedure. Intraocular pressure was measured 3 hours after Nd: yag laser capsulotomy. All the Nd: yag laser posterior capsulotomies, pre and post laser IOP measurements were performed by a single ophthalmologist.
Rise in IOP was labeled when IOP was found 5 mmHg or more from baseline. Mean +-SD was used to express quantitative variables like age. Categorical variables like age groups and presence of acute rise of IOP following yag laser capsulotomy were calculated in the form of frequency and percentage. Chi-square goodness-of-fit test was applied to compare the frequency of acute rise in IOP between sample and population. SPSS-20 was used for data entry and its analysis.
Out of 325 patients, 170 (52.3%) were men and 155 (47.7%) were women with male to female ratio of 1:0.9. (Table 1)
Table 1: Sex distribution in sample and population undergoing Yag laser posterior capsulotomy in Peshawar, Pakistan (n=325)
Sex###Frequency###%age###95% CI of Proportion
Men###170###52.3###46.8 - 57.7
Women###155###47.7###42.2 - 53.1
Table 2: Age group wise distribution in sample and population undergoing Yag laser posterior capsulotomy in Peshawar, Pakistan (n=325)
Age-groups###Frequency###Percentage###95% CI of Proportion
20-39 years###107###32.9###27.7 - 38.0
40-70 years###218###67.1###61.9 - 72.2
Table 3: Frequency of patients having acute rise of intraocular pressure after Yag laser posterior capsulotomy in sample and population in Peshawar, Pakistan (n=325)
Acute rise in Intraocular pressure###Frequency###Percentage###95% CI of Proportion
Yes###61###18.8###14.5 - 23.0
No###264###81.2###76.9 - 85.4
Table 4: Frequency of patients having acute rise of intraocular pressure after Yag laser posterior capsulotomy in sample versus population in Peshawar, Pakistan (n=325)
Acute rise in Intra- Observed###Expected###Chi-square
###O-E###(O-E)2###(O-E)2 /E###DF###P value
No###264###314.84###-50.84###2584.71###8.21###at alpha 0.05
Result is significant at alpha level .05
The mean age of the sample was 44.92+-23.843 years with minimum and maximum age of 20 and 70 years (range =50 years). A total of 107 (32.9%) patients were 20-39 years old whereas 218 (67.1%) were 40-70 years. (Table 2)
Intraocular pressure was raised in 61 (18.8%) patients while in 264 (81.2%) patients it was not raised. (Table 3)
The frequency of acute rise in IOP after Yag laser capsulotomy was significantly higher in sample compared to population. (Table 4)
Shaikh A14 determined higher prevalence of raised IOP (28%) after Yag laser capsulotomy .In our study we found IOP was raised in 61 (18.8%) patients while in 264 (81.2%) patients it was not raised.
Khanzada MA.8 in his study evaluated the complications during and following Yag laser posterior capsulotomy. He showed that out of 320 eyes, only 30 (9.37%) developed IOL pitting, 10 eyes (4.68%) developed rise in IOP, 2 eyes (0.62%) showed rupture in anterior vitreous face, 2 eyes (0.62%) developed Cystoids Macular Edema(CME). The best corrected visual acuity (BCVA) of 6/9 - 6/6 was achieved in 310 eyes (96.87%); whereas only 10 eyes (4.68%) did not have significant improvement in visual acuity. Their results were also comparable with our findings.
In another study from India complications of Yag Laser capsulotomy were studied. Immediate and persistent IOP rise was seen in 39.5% patients.15
Another more recent study in 2014 evaluated the complications of Yag laser capsulotomy showing a variety of complications noted after Yag laser capsulotomy. Intraocular lens pitting was the most common complication seen in 56 eyes (12.81%). Transient rise of IOP was seen in 38 eyes (8.69%) and cystoid macular edema was seen in 17 eyes (3.89%). Serious complications such as retinal detachment and endophthalmitis were seen in 2 eyes (0.45%) and 1 (0.22%) eye respectively.16
One other local study evaluated the complications of Yag laser when applied in post-op posterior capsule Opacification, following extra capsular cataract extraction with IOL. They reported raised IOP seen in 7 cases (5.83%) 17. Their findings were showing IOP rise in less percentage of patients than compared to our study. Karahan E.18 studied the influence of capsulotomy size on IOP and macular thickness. In both groups, IOP increased 1 week after Yag capsulotomy (p = 0.024, I!= 0.001, respectively. All of the patients with IOP elevation were treated successfully with anti-glaucoma medications.
Men were more than women, especially of old age. The frequency of acute rise in IOP after Yag laser capsulotomy was significantly different in sample compared to population.
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|Author:||Muhammad Adnan Khan, Muhammad Tariq Khan, Ashfaq ur Rehman, Mohammad Idris and Muhammad Ayub Khan|
|Publication:||Gomal Journal of Medical Sciences|
|Date:||Dec 31, 2018|
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