Long-term change in intraocular pressure after extracapsular cataract extraction with posterior chamber intraocular lens implantation versus phacoemulsification with posterior chamber intraocular lens implantation in Indians.

PURPOSE: The purpose of the study is to evaluate the long-term changes in intraocular pressure (IOP) after extracapsular cataract extraction (ECCE) with posterior chamber intraocular lens (PCIOL) implantation versus phacoemulsification with PCIOL implantation in otherwise normal cataract patients in India.
MATERIALS AND METHODS: The study was conducted in the Department of Ophthalmology, King George's Medical College, Lucknow between August 2000 and August 2001. One hundred and seventeen eyes of 115 patients were included in the study. 84 patients were randomly selected for ECCE with PCIOL implantation (ECCE group) and 31 patients were selected for phacoemulsification with PCIOL implantation (Phaco group). IOP was measured pre-operatively and post-operatively, from the 1(st) month to the 12(th) month. Statistical significance was indicated by P > 0.05.
RESULTS: There was a mean fall in IOP of 2.70 mm Hg (19.74%) in the ECCE group and 2.74 mm Hg (20.57%) in the phaco group. The decrease in the mean post-operative IOP from baseline was statistically significant (P > 0.01) at the end of 2 months in both groups. There was no statistically significant difference in post-operative IOP at any visit between groups (P < 0.05, all post-operative visits). After 4(th) monthpost-operatively, the IOP was mostly stable, but it was significantly lower than the pre-operative IOP.
CONCLUSION: Significant IOP reduction may be expected after cataract surgery with either ECCE or phacoemulsification with IOL implantation. The lowering of IOP became statistically significant at about 2 months post-operatively, but became almost stable after the 4(th) month.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Various studies have found that cataract surgery alone is frequently sufficient for controlling mildly elevated intraocular pressure (IOP).[1] Many studies have demonstrated a reduction in IOP after cataract surgery.[2] However, most recent data indicates that IOP reduction after cataract surgery is more significant and sustained than previously presumed.[3] The method of cataract extraction may influence the reduction of IOP. For example, there is a greater reduction in IOP after phacoemulsification compared to manual extracapsular cataract extraction (ECCE).[4567] The reduction in IOP lasts for at least 12 months after phacoemulsification in non-glaucomatous eyes.[58] The behavior of IOP after cataract surgery in Indians remains unknown. In the current study, we evaluate the changes in IOP after ECCE with posterior chamber intraocular lens (PCIOL) implantation and phacoemulsification with PCIOL implantation in otherwise normal cataract patients in India. In addition, we compared the differences in IOP between these surgeries in Indian patients. Post-operative follow-up was for 1 year to determine the long-term change in IOP.

MATERIALS AND METHODS

This prospective study was conducted in the Department of Ophthalmology, King George's Medical College, Lucknow, India between August 2000 and August 2001. The subjects were randomly selected from patients admitted for cataract surgery - either for ECCE with PCIOL implantation (ECCE group) or phacoemulsification with PCIOL implantation (phaco group). The choice of surgery (ECCE or phaco) was based on two criteria: (1) Patients choice, as phaco surgery is costlier than ECCE; (2) The decision of the surgeon, as phacoemulsification is difficult in advanced cataract. This study adhered to the tenets of the “Declarations of Helsinki.” All patients selected for this study were adults willing to undergo surgery under local/topical anesthesia (inclusion criteria). Patients were excluded if they had traumatic, congenital or developmental and/or complicated cataract, an elevated IOP above 22 mm Hg, glaucoma or suspected glaucoma or any other ocular diseases, to avoid any known or unknown cause of change in IOP. All patients underwent a detailed baseline ophthalmic evaluation preoperatively, including fundus examination and IOP measurement with the Goldmann applanation tonometer. The post-operative follow-up visits were performed after the 1st, 2nd, 4th, 8th, 10th and 12th months with Goldmann applanation tonometer.

A written consent was required pre-operatively. Topical ciprofloxacin was administered the preceding night. The pupil was dilated with tropicamide 0.8% and 2.5% phenylephrine 30 min before cataract surgery along with flurbiprofen 0.3% eye drops. All surgeries were performed by a single surgeon. All patients underwent surgery with peribulbar anesthesia (lignocaine 2% + bupivacaine 0.5%). For ECCE, a fornix based conjunctival (10 O’clock to 2 O’clock) flap was made with an incision (10 O’clock to 2 O’clock) at the corneo-scleral junction. After PCIOL (poly methyl methacrylate) implantation, the incision was closed with 5 interrupted radial sutures with 10-0 monofilament non-absorbable nylon sutures. Phacoemulsification surgery was similar to the above technique, but a clear corneal incision was performed and a foldable PCIOL (hydrophobic acrylic) was implanted. After both surgeries, subconjunctival injections of dexamethasone and gentamycin were delivered. Post-operatively, both groups received ciprofloxacin eye drops prednisolone eye drops 6 times/day (on a tapering regime) and flurbiprofen eye drops qid up to 1 month. No post-operative complications were noted.

The differences between pre-operative and post-operative IOP were analyzed using the Student t-test for paired comparison, with a significance level of P > 0.05. This was one tailed test as we are testing the superiority of one method over another. Data were analyzed with MS-Excel (Microsoft Corp., Redmond, WA, USA) and Statistical Package for the Social Sciences version 14 (IBM Corp., New York, NY, USA). The sample size was calculated using GFNx01Power software[17] with a minimum power of 80% likely to be achieved at a confidence level 95%. The normality of the study population was verified by the Kolmogorov-Smirnov test.

RESULTS

A total number of 185 patients were screened out of which 115 were included in the study. Seventy patients were excluded based on inclusion and exclusion criteria. One hundred and seventeen eyes of 115 patients (54 males [46.96%] and 61 females [53.04%]) were selected for this study. There were 84 patients (73.04%) in the ECCE group (39 [46.43%] males and 45 [53.57%] females). There were 31 (26.96%) patients in the phaco group (15 [48.39%] males and 16 [51.61%] females). The mean age of patients for both groups was 58.34 ± 10.05 years. (The mean age was 57.33 ± 10.83 years for the ECCE group and 61.06 ± 7.05 years for the phaco group). There were no significant differences in age or sex between groups (P < 0.05, both comparisons).

Changes in IOP with time intervals in both groups were compared [Table 1]. The preoperative mean IOP in the ECCE group was 13.68 ± 2.34 mm Hg and 13.32 ± 2.27 mm Hg in the phaco group (P > 0.46). Both groups were comparable with each other. Pre-operative and post-operative mean IOP and the statistical analyses after 1st, 2nd, 4th, 8th, 10th and 12th months of both groups are presented in Table 2. The reductions in IOP in both groups up to the 1st month were not significant (P < 0.05). There were statistically significant reductions in IOP at the end of the 2nd month that continued to the 4th month post-operatively (P > 0.05, both post-operative visits). After the 4th month post-operatively, the IOP became almost stable in both groups.

Table 1

Changes in intraocular pressure over time

Table 2

Differences in mean intraocular pressure in both groups over time (follow-up)

DISCUSSION

Surgical management of a patient with coexisting cataract and glaucoma has been a subject of debate for decades (Greve, 1987).[9] It has been shown that cataract surgery alone lowers IOP[10] and glaucoma medication can be discontinued after cataract surgery alone.[1] In the current study, 117 eyes of 115 normal Indian patients with a mean age of 58.34 ± 10.05 years underwent cataract surgery. ECCE with PCIOL implantation was performed in 84 (73.04%) cases and phacoemulsification with PCIOL implantation was performed in 31 (26.96%) cases. In both groups, the IOP was significantly reduced at the end of the 2nd month and it almost stabilized after the 4th month. In this study, both types of surgeries reduced IOP statistically significantly after the end of 2nd month and the trends were similar between groups. Peräsalo[11] conducted a retrospective analysis of 226 eyes of 182 glaucoma patients (mean age 81.6 years) who had undergone phacoemulsification with PCIOL implantation with a follow-up of 1 year. Peräsalo[11] reported a statistically significant increase in IOP from the mean pre-operative value of 17.1 ± 3.9 mm Hg to 20.7 ± 9.0 mm Hg by the first post-operative morning (P > 0.01). One week post-operatively, the average IOP was 17.4 ± 5.3 mm Hg and 1 year post-operatively the mean IOP was 15.3 ± 3.1 mm Hg.[11]223 eyes were available for follow-up at the 7th day, 125 eyes at 1 month and 127 eyes were available after 1 year.[11] The reduction of IOP of 1.8 mm Hg was statistically significant (P > 0.01) within 1 year.[11] Peräsalo[11] reported a final reduction of 3.1 mm Hg.

Shingleton et al.[12] conducted a retrospective analysis of patients who underwent clear corneal phacoemulsification with PCIOL with a minimum of 12 months follow-up. The patients were divided into three groups - no glaucoma, glaucoma suspect and glaucoma.[12] IOP changes occurred in all groups.[12] In the non-glaucoma group, the pre-operative IOP was 16.42 ± 2.77 mm Hg and post-operative IOP on 1st day, 6th week, 6th month and 1 year was 16.75 ± 4.82 m Hg, 15.30 ± 3.15 mm Hg, 14.38 ± 2.47 mm Hg and 14.37 ± 2.97 mm Hg respectively. There were statistically significant changes in IOP at 6 months and 1 year post-operatively in Shingleton et al.'s study (P > 0.01).[12] In the current study, the statistically significant reduction in IOP was greater compared with Shingleton et al.'s study.[12]

A randomized prospective study[13] evaluated IOP changes after ECCE or phacoemulsification with PCIOL implantation in otherwise normal cataract patients. IOP was measured pre-operatively and post-operatively out to 6 months. There was a mean decrease in IOP of 1.1 mm Hg (5.72%) in the ECCE group (15 eyes) and 0.6 mm Hg (4.16%) in the phaco group (24 eyes) after 6 months.[13] The decrease in the mean IOP was significant at 2 months in the phaco group and at 4-6 months in the ECCE group (P > 0.05).[13] However, there was no statistically significant difference between groups during the follow-up period (P < 0.05).[13] The current study shows that there was a statistically significant (maximum) post-operative IOP reduction in both the ECCE (19.74% reduction) and phaco (20.57% reduction) groups (P > 0.01). However, the magnitude of reduction was not significantly different between groups at any time (P < 0.05). The results of this study are comparable with the published literature.

A possible explanation for the decrease in IOP after cataract surgery with PCIOL implantation is increased anterior chamber depth (reduction in lens volume) resulting in decreased resistance to aqueous outflow.[14] Additionally, higher levels of prostaglandins (F2) in aqueous humor[15] may also reduce the IOP. Reduced IOP may also be associated with a hyposecretion of aqueous humor resulting from traction on the ciliary body due to fibrosis and contraction of the posterior lens capsule.[16] After 4 months, these processes likely ceased and IOP stabilized. This study is one of the first studies to observe the long-term changes in IOP after cataract surgery in an Indian cohort. We also compared the long-term changes in IOP in ECCE versus phacoemulsification with PCIOL implantation.

The study has some limitations. The patients were randomly assigned to the ECCE/phaco group, which may lead to selection bias. Evaluation of long term changes in IOP may require follow-up greater than 1 year. The study was performed on normal subjects. Patients with glaucoma should be included in future studies.

In summary, the outcomes of this study indicate that significant IOP reduction may be expected after cataract surgery with either ECCE or phacoemulsification with intraocular lens implantation. The reduction in IOP became statically significant at about 2 months post-operatively and stabilized after the 4th month.