|Year : 2014 | Volume
| Issue : 1 | Page : 56-60
Comparison of morphological and functional endothelial cell changes after cataract surgery: Phacoemulsification versus manual small-incision cataract surgery
Sunil Ganekal1, Ashwini Nagarajappa2
1 Nayana Superspecialty Eye Hospital and Research Center; Department of Ophthalmology, Jayadeva Jagadguru Murugarajendra Medical College, Davangere, Karnataka, India
2 Department of Ophthalmology, Jayadeva Jagadguru Murugarajendra Medical College, Davangere, Karnataka, India
|Date of Web Publication||1-Jan-2014|
Nayana Super Specialty Eye Hospital and Research Center, Davangere, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Purpose: To compare the morphological (cell density, coefficient of variation and standard deviation) and functional (central corneal thickness) endothelial changes after phacoemulsification versus manual small-incision cataract surgery (MSICS).
Design: Prospective randomized control study.
Materials and Methods: In this prospective randomized control study, patients were randomly allocated to undergo phacoemulsification (Group 1, n = 100) or MSICS (Group 2, n = 100) using a random number Table. The patients underwent complete ophthalmic evaluation and specular microscopy preoperatively and at 1and 6 weeks postoperatively. Functional and morphological endothelial evaluation was Noncon ROBO PACHY SP-9000 specular microscope. Phacoemulsification was performed, the chop technique and MSICS, by the viscoexpression technique.
Results: The mean difference in central corneal thickness at baseline and 1 week between Group 1 and Group 2 was statistically significant (P = 0.027). However, this difference at baseline when compared to 6 week and 1 week, 6 weeks was not statistically significant (P > 0.05). The difference in mean endothelial cell density between groups at 1 week and 6 weeks was statistically significant (P = 0.016). The mean coefficient of variation and mean standard deviation between groups were not statistically significant (P > 0.05, both comparisons).
Conclusion: The central corneal thickness, coefficient of variation, and standard deviation were maintained in both groups indicating that the function and morphology of endothelial cells was not affected despite an initial reduction in endothelial cell number in MSICS. Thus, MSICS remains a safe option in the developing world.
Keywords: Cataract Surgery, Endothelial Cell Changes, Endothelail Changes, Specular Microscopy
|How to cite this article:|
Ganekal S, Nagarajappa A. Comparison of morphological and functional endothelial cell changes after cataract surgery: Phacoemulsification versus manual small-incision cataract surgery. Middle East Afr J Ophthalmol 2014;21:56-60
|How to cite this URL:|
Ganekal S, Nagarajappa A. Comparison of morphological and functional endothelial cell changes after cataract surgery: Phacoemulsification versus manual small-incision cataract surgery. Middle East Afr J Ophthalmol [serial online] 2014 [cited 2017 Jun 27];21:56-60. Available from: http://www.meajo.org/text.asp?2014/21/1/56/124098
| Introduction|| |
The mean endothelial count (ECC) in the normal adult cornea ranges from 2000 to 2500 cells/mm 2 , and the count continues to decrease with age. Previous cross-sectional studies have shown the normal attrition rate of corneal endothelial cells is 0.3-0.5% per year. , Morphological stability and functional integrity of the corneal endothelium are necessary to maintain long-term corneal transparency after cataract surgery. Endothelial cell loss and corneal decompensation after cataract surgery is well-documented. All surgical procedures that involve entry into the anterior chamber damage a proportion of endothelial cells intraoperative corneal manipulation. After endothelial cell loss, the adjacent cells enlarge and slide over to maintain endothelial cell continuity, which is observed as a change in the endothelial cell density and morphology. Moderate damage to the endothelium during surgery can also lead to a transient increase in corneal thickness. Endothelial cell density and function can be assessed clinically using specular microscopy and pachymetry.
Studies, normal population to assess the response of the endothelium to cataract surgery, have shown a decrease in the endothelial density over a 3-month period postoperatively, with an increase in the coefficient of variation and decrease in the percentage of hexagonal cells. , Previous studies reported no significant difference in endothelial cell loss among the conventional extracapsular cataract extraction (ECCE), manual small-incision cataract surgery (MSICS) and phacoemulsification groups. 
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.  In India, approximately 5 million cataract surgeries are performed per year; therefore, it is important to determine the safest surgical technique for the endothelium. There is a paucity of data from India on the effect of small-incision cataract surgery (SICS) and phacoemulsification on the corneal endothelium (morphological and functional) was performed to assess the postoperative endothelial cell loss and change in endothelial morphology over a short period of time between the two commonly performed cataract techniques.
| Materials and Methods|| |
Study patients included 200 consecutive patients who were age-matched and had similar lenticular changes based on lens opacities classification system III). All patients had a minimum follow-up of 6 weeks. The duration of study was from January 2011 to October 2011. The consecutive patients were divided into two groups, Group 1 (n = 100, underwent phacoemulsification), Group 2 (n = 100, underwent MSICS). Both cataract surgery techniques met the accepted standards worldwide and had been used in many parts of the world for over a decade. All walk-in patients to the hospital with operable cataract were asked to participate. The study was approved by the local ethics committee and written informed consent was obtained from all subjects prior to participation. Some of the consents were in local language to ensure validity. Patients were free to withdraw from the study at anytime and were assured that the study would not compromise the quality of their eye care.
Subjects with active eye disease, history of serious eye injury, prior eye surgeries, diabetes, another cause of decreased vision (e.g., glaucoma or retinal pathology, pseudoexfoliation), a preoperative endothelial cell count of less than 2000 cells/mm 2 , intraoperative conversion of surgical technique from phacoemulsification to MSICS, intraoperative posterior capsular rupture with vitreous loss or those unable or unwilling to provide informed consent were excluded from the study. All the surgeries were performed by one surgeon (SG). The surgeon was masked to the technique until just prior to surgery. Optometrists and ophthalmologists examining the patient postoperatively were not masked to the type of surgery. Randomization was performed to minimize confounding, especially that which would result if the hardness of cataract and preoperative visual acuity were used to assign the type of surgery. Patients were randomly allocated using a randomization Table. The sample size estimation was based on an 80% power to detect a 20% difference in endothelial cell loss at a 5% level of significance and with a 20% loss to follow-up. The sample size meeting this requirement was 100 for each surgical technique (i.e., phacoemulsification and MSICS). All patients underwent complete ophthalmic examination and biometry followed by measurement of central corneal thickness, specular microscopy (endothelial images) was performed at baseline (preoperative) and postoperatively at 1 and 6 weeks. All the parameters were tabulated.
After a subtenon's block of 5-6 cc of lidocaine hydrochloride 2% with (1:20 000) adrenaline, the surgical area was cleansed and draped and the lids were separated using a wire speculum. A fornix-based conjunctival flap was made at the temporal limbus, and bleeding was cauterized with ballpoint cautery as required. A 6.0 mm incision was made on the sclera 1.5 mm from the temporal limbus. A tunnel was created with a stainless steel crescent knife. A side port was made at 12 or 6 O'clock. Hydroxypropyl methylcellulose (HPMC) 2% was injected to fill the anterior chamber. A 26-gauge bent capsulotomy needle/forceps was used to create a continuous curvilinear capsulorhexis (CCC). An entry was made through the tunnel using a 3.2 mm keratome. The tunnel was then extended using an extension blade. Hydrodissection was performed using balanced salt solution. The anterior chamber was refilled with viscoelastic (HPMC 2%) and the nucleus rotated and tumbled into the anterior chamber with a Sinskey hook. The viscoelastic was again injected below as well as above the nucleus to protect the endothelium. The nucleus was then delivered by viscoexpression. The remaining cortical matter was removed with an irrigation/aspiration (I/A) cannula. After which a polymethylmethacrylate posterior chamber IOL was implanted in the capsular bag under saline infusion from the side port. Just prior to the end of surgery, a subconjunctival injection (0.3 mL, 10 mg gentamicin and 2 mg dexamethasone) was performed.
Phacoemulsification Phaco machine was used for all the cases and all the cases were performed by one surgeon (SG). Under topical anesthesia with, 3.0 mm clear corneal temporal incision was made on the steeper meridian with a blade. Two side ports were made at 12 O'clock and 6 O'clock. Sodium hyaluronate 1% was injected through a side port. A CCC was made with a 26-gauge bent capsulotomy needle/forceps. Hydrodissection and hydrodelineation were performed using balanced salt solution. The viscoelastic was then injected and the nucleus stabilized with the chopper. The nucleus was fragmented and removed by direct chop technique. The rest of the cortical matter was removed using an I/A handpiece. A foldable posterior chamber IOL was inserted in the capsular bag with a lens injector under saline infusion from the side port. A subconjunctival injection (0.3 mL) of 10 mg gentamicin and 2 mg dexamethasone was. The eye was not patched since surgery was performed topical anesthesia. Postoperatively, a combination of antibiotic and steroid eye drops was used in both the groups for similar duration and taper along with cycloplegic eye drops.
Specular microscopy and image analysis
The NonCon Robo Pachy Model SP-9000 specular microscope was used to record two central corneal endothelial images .
Endothelial image analysis was performed with the KSS-300S image analysis system. The endothelial image from each subject with the greatest number of discernible cells was selected [Figure 1]. The "button on the main menu was chosen, prompting an analysis screen to appear.'' Left click of the mouse allowed to manually place a green dot at the center of each cell. Dots were placed in as many contiguous cells as possible and no cells were omitted in the middle of the group. After all the dots were placed, the "End" button was selected, and the main screen appeared with the results of the analysis, including cell density, coefficient of variation, and the percentage of hexagonal cells. Mean and standard deviation of baseline parameters were calculated for age, type of cataract, and endothelial microscopy parameters. Comparison of mean changes in the central corneal thickness, cell density, coefficient of variation, and standard deviation both within and between groups at 1 week and 6 weeks as compared to baseline. Comparisons were performed analysis of variance, with 95% level of significance, P < 0.05. Data were entered, an excel file format and subsequently analyzed with SPSS (Statistical Package for Social Sciences) version 17 (IBM Corp., New York, NY, USA).
| Results|| |
There were 100 patients who underwent phacoemulsification (Group 1) and 100 patients who underwent MSICS (Group 2). The mean age of Group 1 was 59.48 years [95% confidence interval (CI): 54.81-64.15 years) and 58.48 years (95% CI; 55.43-61.53 years) for Group 2. There were 110 (55%) males. There was no statistically significant difference in demographic variables (e.g., age, sex) between groups.
Comparison of the mean values of central corneal thickness between groups preoperatively and postoperatively at 1 and 6 weeks is presented in [Table 1]. At 1 week postoperatively, the mean increase in corneal thickness was 9.44 μm in Group 1 and 10.48 μm in Group 2. At 6 weeks postoperatively, the mean corneal thickness was decreased by 3.44 μm in Group 1 and increased by 1 μm in Group 2. The mean difference in central corneal thickness at baseline and 1 week between Group 1 and Group 2 was statistically significant (P = 0.027). However, this difference at baseline with 6 week and 1 week with 6 weeks was not statistically significant (P > 0.05, all comparisons).
|Table 1: Comparison of the mean values (standard deviation) of central corneal thickness between the two groups at preoperative and postoperatively at 1 and 6 weeks|
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Comparison of the mean cell density between groups preoperatively and postoperatively at 1 and 6 weeks is presented in [Table 2]. The mean endothelial cell density was 2247.80 ± 353.80 cell/mm 2 (95% CI: 2101.76 - 2393.84). 2018.88 ± 290.45 cell/mm 2 (95% CI: 1898.99-2138.77). There was a decrease in cell density of 76.12 cells/mm 2 (3.27%) in Group 1 and 315.08 cells/mm 2 (13.49%) in Group 2. This difference in mean endothelial cell density at 1 week and 6 weeks was statistically significant.
|Table 2: Comparison of the mean values of cell density between the two groups at preoperative and postoperatively at 1 and 6 weeks|
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Comparison of the mean values of the coefficient of variation between groups at preoperatively and postoperatively at 1 week and 6 weeks is presented in [Table 3]. The difference in mean coefficient of variation between groups was statistically significant.
|Table 3: Comparison of the mean values of coefficient of variation between the two groups at preoperative and postoperatively at 1 and 6 weeks|
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| Discussion|| |
Manual small-incision techniques are gaining popularity as quick, relatively inexpensive techniques for large-scale cataract management in the developing world. Phacoemulsification has been shown to be safe for the corneal endothelium. ,, However, postoperative visual acuity and complication rates are the same phacoemulsification and SICS. 
Endothelial alteration is considered an important parameter of surgical trauma and essential for estimating the safety of the surgical technique. After cataract surgery, endothelial cell density decreases at a greater rate than in healthy, unoperated corneas. There is a wide variation in endothelial cell loss between the various studies even when the mode of surgery is same (e.g., SICS). This is due to various factors including, different inclusion and exclusion criteria, different grades of cataract, different methods of nucleus delivery in SICS, different types of irrigating solution and viscoelastics. The reported endothelial loss varies between 4% and 25%, and the period of increased postoperative endothelial cell loss remains unknown.  Endothelial cell loss begins soon after surgery, continues for at least 10 years postoperatively and may throughout the patient's life.
A study comparing phacoemulsification and conventional ECCE  reported a 10% reduction in endothelial cells in both groups. In a study comparing endothelial cell loss after conventional ECCE, MSICS, and phacoemulsification,  the ECC decreased by 4.72%, 4.21%, and 5.41%, respectively, with no significant difference between the three groups. Another study  evaluated endothelial cell damage after phacoemulsification and planned ECCE with different capsulotomy techniques. The mean cell loss was 11.8% in the phacoemulsification group, 12.8% in the ECCE group that underwent CCC and 10.1% in the ECCE group that underwent letterbox capsulotomy. The occurrence of posterior capsular rupture and vitreous loss at surgery leads to a statistically significantly higher endothelial cell loss (18.9% vs. 11.5%; P = 0.003).  However, this factor did not affect the results of the current study as we excluded all cases with capsular rupture.
In our study, over 6 weeks there was decrease in cell density of 76.12 cells/mm 2 (3.27%) for phacoemulsification and 315.08 cells/mm 2 (13.49%) for MSICS. This difference in mean endothelial cell density at 1 week and 6 weeks was statistically significant (P = 0.016). This depicts that in Group 1 the mean endothelial cell density at 1 and 6 weeks stabilized and was maintained, whereas the cell density in the MSICS at 1 and 6 weeks was reduced significantly. The SICS technique carries greater risk of endothelial loss that is mainly attributed to surgical manipulation in the anterior chamber close to corneal endothelium and endothelial trauma during the nucleus delivery from the anterior chamber. The manipulation during nucleus delivery further increases by the temporal scleral tunnel approach used in this study (scleral tunnel approach was performed to reduce the postoperative astigmatism). Various modifications of SICS (irrigating vectis, viscoexpression of the nucleus, anterior chamber maintainer, high density viscoelastics) have significantly reduced the endothelial cell loss. In phacoemulsification, the maneuvering is mechanical and performed in the capsular bag, distantly from the endothelium and newer advanced phacoemulsification units with better fluidics may reduce the chances of endothelial damage.
One of the limitations of this study was that only 1 technique of phacoemulsification and one technique of SICS were compared; other techniques may give different results. In addition, stainless steel blades instead of diamond knives were used for phacoemulsification and sodium hyaluronate 1.4% (Healon GV) was not used in order to reduce the cost of the surgery. A viscoelastic with higher retention may have resulted in less endothelial cell loss. An Indian study has shown that safety to the endothelium was similar with the use of sodium hyaluronate for phacoemulsification and HPMC for MSICS.  Another study from Italy has show no significant decrease in mean endothelial cell density with the use of four different viscoelastics (HPMC, Healon, Healon GV, and Viscoat). Hence we opted for HPMC in MSICS. 
A study from Italy  compared endothelial cell damage between scleral tunnel incisions and clear corneal tunnel. Contrary to our study, t  concluded that scleral tunnels led to less postoperative endothelial cell damage than clear corneal tunnels. Because MSICS was performed through the scleral tunnel incision, it may have caused less endothelial cell loss than phacoemulsification performed through a clear corneal tunnel incision.
Another major weakness of our study was the short-term follow-up (6 weeks). However, a prospective study from United States evaluating the long-term safety (5 years) of phakic found that the rate of endothelial cell loss decreases over time.  This agrees with short term studies,  which report a higher rate of endothelial cell loss than longer studies but decrease with time. Endothelial cell loss is more likely related to corneal endothelial cell remodeling after the trauma of surgery than to ongoing age-related cell loss.  A study comparing the effect of different phacoemulsification techniques on corneal endothelial cells found similar outcomes at 3 months and 1 year, postoperatively.  Based on this outcome, we believe that short-term follow-up is adequate to predict the long-term outcomes. Additionally, we used 6 weeks follow-up to reduce the number of patients lost to follow-up, which increase the validity of the present study.
Even though postoperatively, there was statistical significant decrease in the cell density loss in MSICS compared to phacoemulsification over a short-term follow-up of 6 weeks. However, the central corneal thickness, coefficient of variation, and standard deviation were maintained in both groups indicating that the function and morphology of endothelial cells, was not affected despite a reduction in cell number in MSICS compared to phacoemulsification. Thus, there was no difference in safety between MSICS and phacoemulsification. MSICS is still a safe and cost-effective option in the developing world. Proper case selection, diligent surgery, and adequate postoperative care are essential to maintain a clear cornea.
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[Table 1], [Table 2], [Table 3]