Introduction
Cataract is a major cause of reversible blindness worldwide and surgery is currently the only treatment option.1 Cataract surgery has seen in recent years a considerable evolution with respect to the surgical techniques. Phacoemulsification is the preferred technique in the developed world2 while the surgery by MSICS is considered to be a cost effective way of cataract removal in the developing countries. Every cataract extraction, even in experienced hands and with modern techniques, involves some corneal decompensation, which has been reported to occur in about 1% of cataract extractions.3 Morphological stability and functional integrity of the corneal endothelium are necessary to maintain long term corneal transparency. Loss or damage of endothelial cells leads to an increase in corneal thickness, which may ultimately induce corneal decompensation and loss of vision.4 Corneal astigmatism is also a by-product of cataract surgery and it plays an important role in recovery of visual function post surgery.
In developing countries such as India, where there is a cataract backlog, MSICS with intraocular lens (IOL) implantation promises to be a viable cost-effective alternative to phacoemulsification.5 With approximately 6 million cataract surgeries being performed in India every year, it is important to determine the safest surgical technique for the cataract surgery. Hence, this study is an attempt to compare the anatomic and functional changes to the corneal endothelium in cataract patients undergoing MSICS & Phacoemulsification at Regional Institute of Ophthalmology, Govt. Medical College, Amritsar, in relation to endothelial structure, corneal topographic changes, visual acuity and induced astigmatism.
Materials and Methods
This randomized prospective study was conducted on 100 cataract patients visiting Regional Institute of Ophthalmology, Govt. Medical College, Amritsar, after taking permission from Institutional Ethical Committee. Patients were randomly divided into two groups by lottery method, comprising 50 patients each who underwent phacoemulsification (group 1) and manual small incision cataract surgery (group 2). Grading of the cataract was not taken into consideration while allotment of the patient`s to either of the two surgical techniques. Patients with senile cataract or presenile cataract of nuclear grade 2, 3 and 4 according to the LOCS III classification between the age group of 35-75 years, medically fit for cataract surgery under local anaesthesia and patients with normal corneal endothelium were included in the study. Patients with brown cataract, traumatic cataract, any corneal dystrophy and degenerations, past history of corneal or intraocular surgery, ocular diseases like glaucoma and uveitis and intraoperative complications i.e. posterior capsular rupture, vitreous loss were excluded from the study. The technique used in Manual small incision cataract surgery and phacoemulsification met the accepted standards worldwide. A written informed consent was taken in patient’s vernacular language. All surgeries were performed by single surgeon and same type of single piece foldable hydrophilic posterior chamber intraocular lens was implanted. All patients underwent complete ophthalmic examination followed by measurement of central corneal thickness, endothelial cell count (specular microscopy) and pentacam study to know the corneal topography was performed preoperatively and postoperatively at day 1, day 7, day 28 and on 42nd day. Best corrected visual acuity was recorded at 6 weeks. All the parameters were tabulated and data analysis was performed using statistical package for the social sciences, version 21.0 for windows (IBM corp. SPSS, 2012, Armonk, NY) applying Chi square test, student unpaired sample t test and paired sample t test. P value < 0.05 was considered statistically significant. The operative technique used in both procedures met the surgical standards prevalent worldwide.
Surgical technique
After administering peribulbar anaesthesia and achieving asepsis, 50 patients underwent phacoemulsification (group 1) and 50 patients underwent Manual small incision cataract surgery (group 2).
Phacoemulsification
A 2.8 mm superotemporal clear corneal incision was made and two side port incisions were given. Anterior capsule was stained with trypan blue dye. After filling viscoelastic in anterior chamber, continuous curvilinear capsulorrhexis was done using 26 gauge cystitome, hydrodissection and hydrodelineation was done and emulsification of the nucleus was done by chop technique. The remaining cortical matter was cleaned using bimanual irrigation and aspiration cannula. Foldable posterior chamber IOL was implanted in the capsular bag. Anterior chamber was formed with balanced salt solution.
Manual small incision cataract surgery (MSICS)
A fornix based conjuctival flap was made. After giving self-sealing 6 mm superior scleral incision, sclerocorneal tunnel was made upto 1 mm of clear cornea. Side port incision was given and anterior chamber was entered with 2.8 mm keratome blade. Anterior capsule was stained with trypan blue dye. After filling the anterior chamber with viscoelastic, continuous curvilinear capsulorrhexis was performed, sclerocorneal incision was enlarged by making side pouch incision on either side and hydrodissection was done. Viscoexpression of the nucleus was done and remaining lens matter was cleaned with reverse simcoe cannula. Foldable posterior chamber IOL was implanted inside the capsular bag. Anterior chamber was formed with balanced salt solution and conjunctiva was reposited back over the sclerocorneal incision.
Results
Demographical values
The mean age was 56.26±8.73 in group 1 and 59.96±9.93 in group 2. 46% were males and 54% were females in group 1 and 42% were males and 58% were females in group 2. The demographic variables i.e. age and sexes were not statistically significant between the 2 groups (p value > 0.05).
Endothelial cell count
The mean preoperative endothelial cell count in group 1 was 2558.72±354.61 cells/mm2. Postoperatively on day 1, the mean endothelial cell count was reduced to 2331.54±365.65 cells/mm2. On day 42 the mean cell count was further reduced to 2020.08±361.47 cells/mm2. In group 2 the mean preoperative endothelial cell count was 2525.50±289.34 cells/mm2. Postoperatively on day 1 the mean endothelial cell count was reduced to 2355.28± 268.77cells/mm2. On day 42 the mean endothelial cell count was further reduced to 2039.84 ± 268.22 cells/mm2. The difference in mean endothelial cell count was not statistically significant at different postoperative intervals in both the groups. (Table 2)
Table 1
Mean endothelial cell count (cells/mm2)
Endothelial cell loss
In group 1, on first postoperative day there was loss of 227.18± 186.25 cells /mm2 which further increased to 538.64± 350.08 (20.59%) on day 42. In group 2, a day after the surgery there was loss of 170.22± 152.40 cells /mm2 which further increased to 485.66 ± 164.37 (19.20%) on day 42. The difference in mean endothelial cell loss was not significant at different postoperative intervals in both the groups (p >0.05). (Figure 1)
Central corneal thickness
In group 1, the mean baseline central corneal thickness before surgery was 0.51±0.04 mm, which increased to 0.56±0.05 mm a day after surgery and in group 2, it was 0.50±0.04 mm before surgery which increased to 0.55±0.04 mm a day after surgery. The mean central corneal thickness was reduced closest to the preoperative value at day 42 in both the groups with a mean of 0.51±0.04 mm in group 1 and 0.50±0.03 mm in group 2. The difference in postoperative mean central corneal thickness was statistically not significant at all intervals in both groups.(Table 2)
Table 2
Postoperative Mean central corneal thickness (mm)
Visual Acuity
In both groups, 49 cases each (98%) had postoperative best corrected visual acuity better than 6/18. The difference in postoperative best corrected visual acuity at 6 weeks was not statistically significant (p value = 1.0) (Table 3).
Post operative Astigmatism
The mean postoperative astigmatism in Group 1 was 0.154±0.22 D at 6 weeks and 0.32±0.34 D in Group 2 at 6 weeks. The difference was statistically significant between two groups (p value = 0.022). The mean postoperative astigmatism was less in Group 1 compared with Group 2 at 6 weeks. (Figure 2)
Discussion
Phacoemulsification is the benchmark technique for cataract surgery. 6, 7 Manual small incision cataract surgery has emerged as a cost effective alternative to phacoemulsification in the developing world. 8 Endothelial alteration is considered an important parameter of surgical trauma and essential for estimating the safety of the surgical technique. The percentage endothelial cell loss postoperatively in present study was more in group 1 as compared to group 2 in all postoperative intervals but the difference was not statistically significant (p >0.05). Similar result was found in a study by Ganekal S et al. who compared the morphological and functional endothelial changes after phacoemulsification versus MSICS and found that at the end of 6 weeks the endothelial changes were not statistically significant between the 2 groups.9 Various other studies also comparing the endothelial cell loss at 6 weeks between phacoemulsification and manual small incision cataract surgery concluded statistically insignificant difference between the two groups.10, 11, 12 In our study, maximum increase in central corneal thickness was seen postoperatively on day 1 in both the groups. The mean central corneal thickness was reduced closest to the preoperative value at day 42 in both the groups with a mean of 0.512±0.038 mm in group 1 and 0.502±0.034 mm in group 2. Similar increase in central corneal thickness postoperatively was seen in studies by Bolz et al., Ventura et al. and Cheng et al. which reported maximal increase in central corneal thickness occurred within 24 hours following cataract surgery followed by gradual decrease in corneal thickness.13, 4, 14 Our results were also comparable to a study by Kongsap P, in which the central corneal thickness was greater in the phacoemulsification group on first day postoperatively (73 µ increase in MSICS group and 138 µ in phaco group, p=0.008) and it returned to preoperative levels 1 month postoperatively.15
In both the groups, 49 cases each (98%) had postoperative best corrected visual acuity better than 6/18. The difference in postoperative best corrected visual acuity at 6 weeks was not statistically significant (p value>0.05). The result of this study is comparable with numerous studies. In a study by Gogate et al., the corrected distance visual acuity at 6 weeks was better than 6/18 in 98.5% of patient’s eyes in the phacoemulsification group and 97.3% of patient’s eyes in the SICS group. Thus, there was no statistically significant difference in visual acuity between phacoemulsification and SICS.11 Similar results were found in a study by Ashok Rathi et al as there was no statistically significant difference between the MSICS & Phacoemulsification in terms of BCVA at post-operative 1 month.16
In our study, there was no significant difference in mean astigmatism between both the groups during preoperative period. The mean postoperative astigmatism at six weeks in Group 1 was 0.154±0.22D and 0.32±0.34D in Group 2. The difference was statistically significant between two groups (p value < 0.05). Mean astigmatism was much higher in MSICS group as compared to phaco group during all post-operative days and the mean differences were statistically significant. Similar results were found in a study conducted by Harakuni U et al. which observed SIA on 45th post-operative day in SICS group was +0.05 while in phaco group was -0.53 and this difference was statistically significant. SIA in phaco group was less compared to SICS group, showing phacoemulsification induced less post-operative astigmatism.17 Study conducted by Khalaf M. et al. observed, at 3 months follow-up, the mean SIA was 2.08 in phaco group and in SICS group it was 2.96.18
Conclusion
Our study concluded that both Phacoemulsification and MSICS gave similar statistically insignificant results in relation to endothelial cell loss, central corneal thickness and best corrected visual acuity at the end of six weeks, although the mean astigmatism was more in group 2 in comparison to group 1. As the Manual small incision cataract surgery does not depend upon advanced technology and is more cost effective, it may be a favourable surgical procedure in those areas where high cost phacoemulsification techniques are still not accessible.
