To observe longitudinal changes in the corneal endothelium after pediatric cataract surgery with intraocular lens implantation.
Prospective, longitudinal study.
settings: Iladevi Cataract and IOL Research Centre, Ahmedabad, India. study population: This study included 100 pediatric eyes undergoing cataract surgery with intraocular lens implantation. Posterior capsule management was based on the status of the posterior capsule. Two-port anterior limbal vitrectomy was carried out after posterior capsule plaque peeling. observation procedures: Corneal endothelial morphologic features: endothelial cell density (cell/mm 2 ), coefficient of variation, percentage of hexagonality, and central corneal thickness were assessed. main outcome measures: To evaluate whether there is a difference in endothelial cell morphologic features before surgery and 3 months after surgery and also whether pediatric cataract surgery with and without anterior vitrectomy has any impact on the endothelial cell morphologic features.
A comparison of preoperative and postoperative specular microscopy is given here: endothelial cell density, 3225.1 ± 346.8 cells/mm 2 versus 3057.7 ± 330.1 cells/mm 2 ( P < .001); coefficient of variation, 27.5 ± 10.6 versus 37.7 ± 16.3 ( P < .001); percentage of hexagonality, 58.1 ± 15.3 versus 48.6 ± 13.4 ( P < .001); and central corneal thickness, 529 ± 30 μm versus 527 ± 34 μm ( P = .64). There was 5.1% decrease in mean endothelial cell loss at 3 months after surgery. No statistically significant difference was noted in the percentage decrease in mean endothelial cell density between eyes undergoing cataract surgery with intact posterior capsules, eyes undergoing manual posterior capsulorrhexis without anterior limbal vitrectomy, and eyes undergoing anterior limbal vitrectomy ( P = .543).
Endothelial cell loss with currently practiced techniques of pediatric cataract surgery is within acceptable limits by adhering to the principles of close chamber technique.
Advances in microsurgical techniques and a better understanding of the intricacies of a child’s eye and its response to surgery have helped to improve the results of pediatric cataract surgery. Although the principles of adult cataract surgery are adopted during pediatric cataract surgery, several features of the child’s eye render the surgical management of pediatric cataract distinctly different. Low scleral rigidity predisposes the eye to recurrent shallowing of the anterior chamber. Further, these eyes display an increased propensity for postoperative inflammation and glaucoma. These complications can be deleterious to the corneal endothelium.
The endothelial monolayer is a finite pool of cells in which mitotic division does not occur routinely. Measures must be taken during all intraocular surgeries to minimize endothelial damage. Endothelial cell loss has been reported to be 4.6% to 15.6% after phacoemulsification in adult eyes. A few pediatric studies have reported corneal endothelial morphologic features in eyes with clear lenses and in pseudophakic eyes. However, most of these studies have been cross-sectional. Because of the paucity of available literature, this prospective, longitudinal clinical trial compared the preoperative and the early postoperative corneal endothelial cell morphologic features in children who underwent cataract surgery with primary intraocular lens (IOL) implantation.
A prospective, longitudinal, clinical trial in 106 eyes of 70 patients undergoing pediatric cataract surgery with IOL implantation between January 2009 and April 2011 was conducted at Iladevi Cataract & IOL Research Center, Ahmedabad, India. Children older than 4 years undergoing cataract surgery with IOL implantation were included. Exclusion criteria were as follows: eyes with traumatic or subluxated cataract and inability to obtain a preoperative specular count. During surgery, sulcus-fixated IOLs and eyes with no IOL implantation were excluded. A thorough preoperative evaluation was performed. A slit-lamp biomicroscopy was carried out after pupillary dilatation. Intraocular pressure (IOP) was measured with a Perkins handheld applanation tonometer. Initially, the eye was anesthetized with 0.5% proparacaine eye drops (Sunways, Mumbai, Maharashtra, India). The central corneal thickness (CCT) then was assessed by ultrasonic pachymetry (Ocuscan; Alcon, Mumbai, Maharashtra, India). Axial length and anterior chamber depth were measured with optical coherence biometry (IOL Master; Zeiss) or an ultrasound A-scan using the immersion technique (Ocuscan; Alcon).
After a routine ophthalmic examination, all the children underwent specular microscopy with a noncontact specular microscope (SP2000; Topcon Corp, Tokyo, Japan). A single examiner (M.R.P.) obtained all the measurements. From the central cornea, the examiner obtained a single image of at least 100 contiguous cells and manually marked it with a mouse using a built-in software program. The computer automatically evaluated, calculated, and displayed the mean endothelial cell density (ECD; cells/mm 2 ), coefficient of variation (CV) in cell size, and percentage of 6-sided cells (6A).
The same surgeon (A.R.V.) performed all the surgeries under general anesthesia using a standardized surgical technique. Initially, 2 1-mm paracentesis incisions were created, followed by manual anterior continuous curvilinear capsulorrhexis. In eyes with total cataract, the anterior capsule was stained with trypan blue solution before performing anterior capsulorrhexis (0.1 mL/0.6 mg; 0.0125%; pH, 7.39; osmotic pressure, 1.22 mm Hg). After this, bimanual irrigation and aspiration were performed. Posterior capsule management was based on the status of the posterior capsule (manual posterior continuous curvilinear capsulorrhexis [PCCC] or plaque peeling). Two-port anterior limbal vitrectomy was carried out on completion of posterior capsule plaque peeling. Later, a temporal clear corneal incision of 3.2 mm was created for in-the-bag single-piece hydrophobic acrylic IOL (SA60AT; Alcon) implantation. The implantation was carried out using the shooter type injector (ASICO; Royale Injector, USA). The residual ophthalmic viscosurgical device was removed by 2-port anterior limbal vitrectomy. The incisions were sutured using 10-0 nylon. The pupil was constricted by injecting Carbachol (0.01%; Biotech Ophthalmics, Ahmedabad, Gujarat, India) intracamerally. In all the eyes at the end of the procedure, 0.1 mL intracameral moxifloxacin 0.5% ophthalmic solution containing 500 μg moxifloxacin was injected. After surgery, patients were examined at 3 months for CCT and corneal endothelium.
The results were analyzed for ECD, CV, 6A, and CCT at 3 months after surgery. A comparison was drawn between the preoperative and postoperative values using the Wilcoxon paired test. We further analyzed the percentage difference in mean CCT and mean ECD and between mean CV and mean 6A between the preoperative period and 3 months after surgery. The percentage difference was calculated as follows, for example, in case of ECD: ((difference between preoperative and postoperative ECD counts)/(preoperative ECD counts)) × 100. Further, preoperative age at surgery, axial length, and anterior chamber depth were correlated with ECD loss at 3 months after surgery using the Spearman correlation coefficient.
A comparison also was drawn between the values recorded for mean ECD, CV, 6A, and CCT at 3 months after surgery among the 3 groups: eyes with intact posterior capsules, manual PCCC without 2-port anterior limbal vitrectomy, and posterior capsule plaque peeling with 2-port anterior limbal vitrectomy. The data were not normally distributed; nonparametric tests were used. The Wilcoxon signed-rank test was used to compare preoperative values with values obtained 3 months after surgery. The Kruskal-Wallis test was used to compare changes in ECD, CV, 6A, and CCT among the 3 groups.
Sample Size Calculation
After carefully considering and evaluating published data from a study of children undergoing cataract surgery with IOL implantation, observations published in a report on preoperative values of ECD, and discussions with the expert panel, we assumed that there would be a 4% decline in endothelial cell density at 3 months after surgery with a correlation of 0.5% (preoperative minus postoperative). Using these inputs and allowing for a 10% dropout rate, we concluded that a sample size of 69 eyes would have 90% power to detect the difference in preoperative and postoperative ECD.
We excluded 6 eyes (100/106) from the analysis because we did not receive the postoperative specular microscope results as a result of poor cooperation. Thus, we evaluated 100 eyes. Of 70 patients, 40 were unilateral cases and 30 were bilateral cases. The mean age was 6.6 ± 2.3 years (range, 4 to 13 years). The distribution of different types of cataract was as follows: lamellar cataract in 77 (77%) eyes, total cataract in 18 (18%) eyes, and posterior subcapsular cataract in 5(5%) eyes. Mean axial length was 22.27 ± 1.7 mm (median, 21.95 mm), mean lens thickness was 3.81 ± 0.89 mm (median, 3.35 mm), mean anterior chamber depth was 3.29 ± 0.54 mm (median, 3.40 mm), and mean IOP was 15.09 ± 2.2 mm Hg (median, 15 mm Hg).
In 18 (18%) eyes, the anterior capsule was stained with trypan blue solution before anterior capsulorrhexis was performed. Ultrasound phaco energy was not required for any eye. Bimanual irrigation and aspiration were used. Manual posterior capsulorrhexis was performed in 42 (42%) eyes; 16 (16%) eyes had intraoperative posterior capsule plaque and had to undergo plaque peeling with 2-port limbal anterior vitrectomy. None of the eyes had to undergo pars plana vitrectomy. Another 42 (42%) eyes had an intact posterior capsule. No major intraoperative complications were noted during cataract surgery.
Table 1 illustrates endothelial cell morphologic features and CCT values both before and 3 months after surgery. There was a significant change in ECD ( P < .001), CV ( P < .001), and 6A ( P < .001) from the preoperative period to 3 months after surgery. There was an increase in CCT from the preoperative period to 3 months after surgery, but this did not attain statistical significance ( P = .64). There was a 5.1% decrease in the mean percentage of ECD cell loss, a 19.84% increase in CV, a 9.20% decrease in hexagonal cells, and a 2.1% increase in mean CCT from the preoperative period to 3 months after surgery. Further, there was no statistical correlation between endothelial cell loss and the change in CCT after surgery at the 3-month follow-up (Pearson correlation coefficient, −0.20; P = .11).
|Endothelial Cell Density (cell/mm 2 )||Coefficient of Variation||Hexagonality||Central Corneal Thickness (μm)|
|Before Surgery||Three Months After Surgery||Before Surgery||Three Months After Surgery||Before Surgery||Three Months After Surgery||Before Surgery||Three Months After Surgery|
|Mean||3225.1 ± 346.8||3057.7 ± 330.1||27.5 ± 10.6||37.7 ± 16.0||58.1 ± 15.3||48.6 ± 13.4||529 ± 30||527 ± 34|
|Range||2724 to 3977||2446 to 3748||11 to 54||15 to 13||22 to 92||21 to 90||453 to 592||432 to 596|
|P value a||.001||.001||.001||.64|
The preoperative mean age at surgery, axial length, anterior chamber depth, and IOP did not show any significant correlation with the percentage of endothelial cell loss after surgery at the 3-month follow-up (age at surgery: Pearson correlation coefficient, 0.159; P = .114; axial length: Pearson correlation coefficient, −0.04; P = .69; anterior chamber depth: Pearson correlation coefficient, −0.124; P = .128; IOP: Pearson correlation coefficient, −0.02; P = .86).
Table 2 illustrates a comparison between eyes with intact posterior capsules, manual PCCC without anterior limbal vitrectomy, and posterior capsule plaque peeling with anterior limbal vitrectomy. There was no significant difference observed between these 3 groups with respect to ECD, CV, and 6A before surgery and after surgery at 3 months (ECD, P = .06; CV, P = .286; 6A, P = .301). Further, there was no statistically significant percentage decrease in mean ECD, percentage difference in CV, or percentage difference in 6A among the 3 groups (Kruskal-Wallis test: ECD, P = .543; CV, P = .57; 6A, P = .06; Table 3 ).
|Endothelial Cell Density (cell/mm 2 )||Coefficient of Variation||Hexagonality||Central Corneal Thickness (μm)|
|Before Surgery||After Surgery||Before Surgery||After Surgery||Before Surgery||After Surgery||Before Surgery||After Surgery|
|Posterior capsule plaque peeling + anterior limbal vitrectomy (n = 16 eyes)|
|Mean||3356.1 ± 357.7||3249 ± 330.3||29.2 ± 13.5||37.2 ± 6.3||60.4 ± 13.7||43.0 ± 11.9||519.5 ± 34.6||531.9 ± 42.8|
|Range||2777 to 3881||2630 to 3687||12.0 to 54.0||30.0 to 56.0||39.0 to 82.0||21.0 to 67.0||453 to 568||455 to 596|
|Manual posterior capsulorrhexis (n = 42 eyes)|
|Mean||3259.2 ± 357.8||3080.0 ± 341.6||29.2 ± 11.0||38.6 ± 19.1||60.9 ± 15.3||49.6 to 13.9||525.2 ± 26.6||529.5 ± 31.9|
|Range||2724 to 3977||2501 to 3748||12.0 to 54.0||15.0 to 13.0||33.0 to 92.0||22.0 to 90.0||477 to 589||432 to 573|
|Posterior capsule intact (n = 42 eyes)|
|Mean||3141.3 ± 317.1||2991.8 ± 308.2||25.3 ± 8.8||37.1 ± 16.3||54.6 ± 15.6||49.8 ± 13.4||535.8 ± 31.3||521.6 ± 31.4|
|Range||2777 to 3881||2446 to 3712||11.0 to 47.0||15.0 to 98.0||22.0 to 82.0||29.0 to 83.0||474 to 592||445 to 568|