Clinical Evaluation and Procedures

A comprehensive preoperative evaluation was performed (under anesthesia when necessary) on the slit lamp or the slit lamp attachment of an operating microscope. Type of cataract was documented as lamellar, cortical, total, and preexisting posterior capsule defect. Axial length was measured with immersion ultrasound (Ocuscan; Alcon, Fort Worth, Texas, USA). Intraocular pressure (IOP) was measured with a Perkins handheld applanation tonometer. Blood investigations were performed for every child (prothrombin time and activated prothrombin time) to rule out any bleeding tendency.

The eye to be operated upon first was selected by a computer-generated table of random numbers by one of the authors (V.V.). The second eye underwent cataract surgery after a gap of at least 2 weeks following surgery in the first eye. Pupillary dilation was achieved using cyclopentolate 1% (Sunways, Mumbai, Maharashtra, India) eye drops instilled twice, 12 and 2 hours before surgery. In addition, phenylephrine 10% (Sunways) eye drops were administered 15 minutes apart, twice, 30 minutes before surgery. Patients were randomized to either receive enoxaparin in the intraocular infusion fluid (Group I) or not receive enoxaparin (Group II). The randomization code was allocated inside the operating room just before the surgery on the first eye. The second eye received alternate treatment. If an eye received a randomization code to use low-molecular-weight heparin, enoxaparin (Clexane; Aventis Pharmaceuticals, Mumbai, Maharashtra, India) was added to the irrigating solution (balanced salt solution) in a concentration of 40 mg/500 mL.

Surgical standardization and consistency was maintained throughout the study by ensuring that a single surgeon (A.R.V.) carried out all the surgical procedures using the principles of the closed chamber technique. The surgeon was masked to the intervention received. The surgical procedure used in both groups is as follows: corneal tunnel, multiquadrant hydrodissection, bimanual irrigation/aspiration, posterior continuous curvilinear capsulorrhexis (PCCC) in children below 6 years of age, and anterior vitrectomy in children below 2 years of age. A single-piece hydrophobic acrylic aspheric IOL (AcrySof IQ, SN60WF; Alcon Laboratories, Fort Worth, Texas, USA) was implanted in the capsular bag in all eyes. If in-the-bag IOL implantation could not be achieved, the eye was planned to be excluded from the study. No patient was administered subconjunctival steroids. The postoperative treatment regime was also standardized for both groups. This included prednisolone acetate (1%) eye drops (Allergan Pharma, Bangalore, Karnataka, India), 6 times a day tapered every 2 weeks; moxifloxacin (Vigamox, Alcon Laboratories) eye drops, thrice a day for 4 weeks; cyclopentolate eye drops (Sunways), twice a day for 2 weeks; and timolol maleate 0.5% eye drops (Alcon), twice a day for 2 weeks. Postoperatively, administration of eye drops commenced 2 hours after surgery. Data collection was carried out using a standardized form. The parameters of data collection were age, sex, surgical details including intraoperative trauma (if any), and postoperative examination.

The follow-up visits were in the first week (allowed anywhere from day 2 to day 7) and subsequently at 1 month (allowed between 20 and 40 days postoperatively) and 3 months (allowed between 80 and 100 days postoperatively) . The follow-up duration was deliberately maintained as a range rather than as a fixed time period, keeping in mind logistical reasons (eg, the patient’s inability to come on a specific day). All the examinations were performed by a single skilled observer (S.S.) who was masked to the intervention, under anesthesia when required. The operating surgeon and the examiner were masked to the type of irrigating fluid used during surgery. Postoperative assessment was performed by slit-lamp microscopy in the clinic or in the operating room, using the slit lamp attachment of the operating microscope. As described below, anterior chamber cells and flare were analyzed using Hogan’s criteria while cell deposits were analyzed using the method published previously.

Hogan’s criteria grades anterior chamber cells as: 0 = no cells; 1 = 5 to 10 cells; 2 = 11 to 20 cells; 3 = 21 to 50 cells; and 4 = >50 cells per high-power field. Hogan’s criteria grades anterior chamber flare as: 0 = no flare; 1 = faint and just detectable flare; 2 = moderate flare with iris details clear; 3 = marked flare with iris details hazy; and 4 = intense flare with severe fibrinous exudates per high-power field. Number of small cell deposits on IOL was graded as: grade 0 = no cells; grade 1 = up to 2 cells; grade 2 = 2 to 5 cells; grade 3 = 6 to 10 cells; grade 4 = more than 10 cells. Number of large cell deposits on IOL was graded as: grade 0 = none; grade 1 = less than 5; grade 2 = 6 to 10; grade 3 = up to 20; grade 4 = more than 20.

In addition, the presence and extent (in clock hours) of posterior synechiae were recorded.

Sample Size Calculation

Anterior chamber cells and flare are the earliest indicators of early postoperative inflammation. Early postoperative inflammation may be correlated to long-term inflammatory sequelae. In the absence of available literature, we used data from a pilot study of 11 patients (11 eyes in each group) to arrive at the sample size. The main outcome measure was the presence of grade 2 anterior chamber cells in the first postoperative week. In the first week, cells with grade 2 were seen in 18% of the eyes in Group I (enoxaparin group) and 55% of the eyes in Group II (no enoxaparin group). To detect the difference of 33% between the 2 groups, using the test of proportions at 5% level of significance, a sample size of 24 in each group was necessary to achieve 80% power.

Data Analysis

The differences in anterior segment inflammation, cell deposits on the IOL, and posterior synechiae between the 2 groups were analyzed using the test of proportions. Data were stratified to evaluate any difference between first eyes and second eyes (irrespective of the use of enoxaparin), as inflammation, compliance with medications, and familiarity with evaluation techniques may influence results. We also analyzed eyes that underwent anterior vitrectomy vs eyes that did not undergo vitrectomy.

All statistical analysis was performed using the SPSS software (version 12.0; IBM, Morrisville, North Carolina, USA). A P value of less than .05 was considered statistically significant.