This study was approved by the Ethics Committee of Zhongshan Ophthalmic Center in Guangzhou (2015MEKY081) and complied with the Declaration of Helsinki. Informed consent was obtained from each participant after a thorough explanation of the procedures and its risks by principal investigator (S.Y.Z).
Study Design and Participants
This was a prospective, randomized, parallel-group, and controlled trial that included participants with recurrent pterygium, and conducted at the Cornea Division of Zhongshan Ophthalmic Center at Sun Yat-sen University. Consecutive patients with recurrent pterygium were assessed for eligibility from February 2012 to October 2021, and 135 eyes were evaluated. Figure 1 shows the flow of the participant (eye) enrollment throughout the study. Finally, A total of 132 patients were enrolled and randomly assigned to either the LCAG + MMC or CAG + MMC group.
Inclusion and exclusion criteria
Inclusion criteria: recurrent pterygium with a history of at least 6 months after the last pterygium surgery, patients between the ages of 18 and 80 with no ocular or systemic contraindications for surgery, and a willingness to participate in this study. The exclusion criteria included having systemic collagen vascular diseases or other autoimmune diseases, being pregnancy, having a history of corneal infection, ocular hypertension (> 21mmHg) or glaucoma, retinal detachment, having undergone ocular surgeries such as anti-glaucoma surgery or ocular trauma surgery, receiving treatment with glucocorticoid, anti-metabolic drugs or immunosuppressive drugs within two weeks.
Sample Size
The primary outcome is to detect the recurrence rate. The sample size was calculated based on a RCT report comparing limbal and conjunctival autografts for recurrent pterygia.9 In previous RCT study, the recurrence rate for limbal autograft was 0%, while the recurrence rate for conjunctival autograft was 12.5%.9 Using a 2-sided 5% significance level (α = 0.05) and power of 80% (β = 0.20), with an assumed 10% participant dropout rate during follow-up, a sample size of 132 eyes was determined necessary for this study. A sample size calculator (Formula) (http://www.rad.jhmi.edu/jeng/javarad/samplesize/) was used to calculate (P1 = 12.5%, P2 = 0%; Difference Test).
$$\text{N}=2\times \frac{{\left[{\text{Z}}_{{\alpha }}\sqrt{2\text{p}\left(1-\text{p}\right)}+{\text{Z}}_{{\beta }}\sqrt{{\text{p}}_{1}\left(1-{\text{p}}_{1}\right)+{\text{p}}_{2}\left(1-{\text{p}}_{2}\right)}\right]}^{2}}{{\text{D}}^{2}}$$
Randomization
The participants were randomly assigned to two groups using a computer-generated random (block randomization, the block size is four) number table (SAS, Version 8.0, Cary, NC, USA) prepared by a biostatistician (Professor Futian Luo). The allocation was concealed using sequentially numbered, sealed envelopes prepared by a research assistant who was not involved in the study. The eyes that were listed for recurrent pterygium excision surgery were randomly assigned into two groups: Group LCAG received a combination of LCAG and intraoperative 0.02% MMC for 5 minutes, while Group CAG received a combination of CAG and intraoperative 0.02% MMC for 5 minutes. For eyes with recurrent pterygia on both the nasal and temporal sides, the nasal side were covered with either LACG or CAG, and the temporal side was covered with an amniotic membrane graft after applying MMC on both sides during the operation.
Surgical Procedures
Ocular examinations were conducted before the surgery, which included noncontact tonometry, slit-lamp biomicroscopy, ophthalmoscopy, and uncorrected distance visual acuity (UDVA) assessment using the Standard Logarithmic Visual Acuity Chart for analysis. The size of cornea invasion (length and chord width) and the degree of vascularization (grades 1 to 3) were recorded as our previous report.6 The patients’ demographic and clinical data were recorded.
The surgical procedure was performed by a single surgeon (S.Y. Zhou) following our previously described methods.6 Briefly, after administering local anesthesia, the head of the recurrent pterygium was first separated, and extensive excision of scar tissue and release of symblepharon were performed. Following gentle cauterization, a moist cotton pad soaked with 0.02% MMC (2 mg/vial; Kyowa®, Tokyo, Japan) was applied to the bare sclera and the undersurface of the surrounding residual conjunctival bed for 5 minutes. Each cotton pad was soaked in 0.15 ml 0.02% MMC per 1 cm2 area, ensuring that the cotton surface was only slightly wet but not saturated. Before applying the MMC-soaked cotton pad, the exposed scleral bed was dried, and a cotton swab was used along the corneal limbus to prevent any contact between the cornea and MMC. Then, after rinse with at least 100 ml of 0.9% normal saline solution, the exposed sclera was covered by a free conjunctival flap (Video 1) or limbal conjunctival flap (Video 2) obtained from the superior bulbur conjunctival area. The graft was sutured with interrupted 10 − 0 nylon sutures (Alcon®, Alcon Laboratories, Inc., Fort Worth, TX, USA) to stretch the graft by suturing through the sclera. During surgery, a caliper was used to measure the size of autograft, the distance from rectus musle to the cornea and the suture stitches were also recorded. A desired-sized LCAG graft was obtained by dissecting the conjunctiva along the marks until it reached the clear cornea through the limbus, and the limbus would be placed on the corneal side of the wound bed, in order to restore the normal anatomy. A conjunctival autograft was dissected without touching the corneal limbus. The graft donor site was left untouched, with Tenon’s tissue exposed. At the end of the surgery, 0.3% tobramycin drops (Tobrex®, Alcon, Couvreur, Belgium) and a therapeutic bandage contact lens (PurevisionR, Bausch & Lomb, Inc., Rochester, NY, USA) were applied.
Postoperative Treatment and Follow-up
All patients were prescribed topical 0.5% levofloxacin eye drops (Cravit®, Santen Pharmaceutical Co., Osaka, Japan) for the first week, then followed by 0.3% tobramycin/0.1% dexamethasone eye drops (Q.I.D) and ointment (TobraDex®, Alcon, Couvreur, Belgium) for the next two weeks. Subsequently, 0.1% pranoprofen eye drops (Pranopulin®, Sunju Pharmaceutical Co., Ltd., Japan) and 0.1% sodium hyaluronate eye drops (Hialid®, Santen, Japan) were administrated for another five weeks. The bandage contact lens and interrupted sutures were removed 2 weeks postoperatively in both groups. Patients were scheduled for follow-up examinations on 1 day, 2 weeks, 1 month, 6 months, and 12 months after the surgery.
Clinical Outcomes
The primary outcome was the recurrence rate of pterygia within 12 months postoperatively, which was graded from 1 to 4, as described by Ma etal 5 and Chen et al.6 and according to the classification of Prabhasawat et al.13. Grade 1 indicated no recurrence, and the surgical area was indistinguishable from the normal eye. Grade 2 presented episcleral vessels without fibrous tissue in the surgical area. Grade 3 manifested fibrovascular tissue without invavsion onto the cornea. Grade 4 had fibrovascular tissue encroached onto the cornea. In our study, grade 4 was defined as pterygia recurrence in the surgical area.
The secondary outcome included the residual conjunctival bed status and associated complications. Host conjunctival inflammation was graded 0 (none), I (mild), II (moderate), or III (severe) as described previously14.
The evaluations were verified by two independent trained observers ( Dr. K. Yu and Dr. W.Y. Peng) through photography, who were blinded to the group allocation.
An assistant (J.K.Pi) was assigned to call patients and encourage their compliance with follow-up. During lockdown due to the coronavirus pandemic, patients were asked for follow-up and photography in a close clinic or through close-up macro photography of their eyes via “We Chat” instead. All the patients were checked and photographed by the principle investigator after the end of coronavirus pandemic.
Complications
Scleral thinning or ulceration, corneal perforation, iritis, cataract formation, glaucoma, the donor site of the LCAG/CAG graft, any localized pannus formation, and pseudopterygium were recorded.
Statistical Analysis
The Shapiro-Wilk test was used to determine the normal distribution of baseline and postoperative data. The Mann-Whitney U test was employed to compare demographic data such as age, height, weight, the exposure area, number of suture bites, distance from the rectal muscle to the cornea, and visual acuity. The Chi-square test was utilized to analyze the recurrence rates between the two groups. Binomial logistic regression analysis was conducted to investigate the relationship between recurrent rate and baseline conditions. P<0.05 was considered significant difference.