Mini-simple limbal epithelial transplantation and conjunctival-limbal autograft for the treatment of primary pterygium: Study protocol for a randomized controlled trial

Abstract

Background

Pterygium is a wing-shaped fibrovascular growth over the cornea that may require surgical removal due to recurrence and cosmetic concerns. This randomized controlled trial compares the recurrence rate of conjunctival-limbal autograft (CLAu) with a modified mini-simple limbal epithelial transplant (mini-SLET) technique.

Methods

68 patients will be randomly assigned to two equally sized groups via simple randomization. Group I will undergo a pterygium excision with CLAu, while Group II will undergo a pterygium excision using a mini-SLET. Allocation concealment will be ensured using sealed envelopes, and procedures will be performed by two surgeons. Patients will be followed postoperatively at regular intervals for up to 12 months.

Discussion

This study builds on previous research by modifying the mini-SLET technique to enhance corneal stem cell viability and reduce recurrence. By refining this method, we aim to offer patients a more effective and minimally invasive alternative to the gold-standard procedure.

Trial registration

ClinicalTrials.gov, NCT06402643. Registered on April 15, 2024.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-025-09075-3.

Background

Pterygium refers to a benign elastotic degeneration, wing-shaped growth of fibrovascular tissue that extends over the cornea [1, 2]. The prevalence ranges from 7% to 15% [3–7], with the higher end of that spectrum occurring in countries closer to the equator. An initial approach to managing pterygia involves conservative interventions, including the use of lubricating agents and protective eyewear in the form of sunglasses. Surgical interventions may be undertaken in instances where patients express a desire for amelioration of symptoms, enhancement of visual function, or improvement in aesthetic appearance. To optimize aesthetic outcomes and minimize the likelihood of recurrence, many approaches can be employed to manage a specific problem following the determination of the need for surgical intervention.

For both primary and recurring pterygia [8], using conjunctival-limbal autograft (CLAu) on the exposed sclera has been suggested as a way to stop the infiltration of fibrovascular tissue after surgery removal. CLAu and conjunctival autograft (CAG) are considered the gold standard treatments [9–11]. On the other hand, an alternative approach involves the utilization of an amniotic membrane (AM) graft to cover the exposed scleral area in conjunction with a minor autologous limbal epithelial transplant (mini-SLET) to introduce stem cells into the limbal area [1]. Oliva-Biénzobas et al. [6] performed a randomized controlled trial study comparing these two techniques and observed a higher recurrence rate in the mini-SLET group with the use of two amniotic membranes. Alok et al. [12] reported a 2.5% recurrence with reduced postoperative symptoms and other complications in the patients treated with the mini-SLET technique. They used only one AM graft, with an additional 1 mm length, which was tucked under the conjunctival margins and secured onto the bare sclera with fibrin glue.

The utilization of CLAu has been found to present a reduced recurrence rate and a decreased occurrence of problems. Nonetheless, it is essential to note that this procedure is unsuitable for situations where there is a need to address a substantial defect or for patients who require preservation of the conjunctiva for potential future surgical interventions. To prevent conjunctival scarring during the extraction procedure, glaucoma may be considered a precautionary measure. The purpose of this randomized controlled trial was to compare the recurrence rate of CLAu with a modified mini-SLET technique.

Methods/design

Study objective and hypotheses

In this study, we aim to demonstrate that the modified mini-SLET technique decreases the recurrence rate better than the gold standard procedure (conjunctival-limbal autograft) for treating pterygium. Potential pterygium recurrence is a persistent concern among ophthalmologists due to its negative impact on surgical outcomes. The range of recurrence rates reported in a recent meta-analysis conducted by the Cochrane Collaboration on conjunctival autograft outcomes varies from 3.33% to 16.7% [13, 14]. The study will exclude individuals who had rheumatoid arthritis and collagenopathies, were pregnant, had ocular surface abnormalities, had experienced trauma, had glaucoma, or had undergone previous ocular procedures. A thorough ocular assessment will be conducted on all trial participants.

Trial design

The participants will be randomly distributed into two equally sized groups through the process of simple randomization using a table of random numbers. Group I will be treated with pterygium excision with the use of conjunctival-limbal autograft (CLAu), while Group II will be treated with pterygium excision and mini-SLET. A sole author (GRVD) will generate the random allocation sequence and then assign participants to their respective intervention groups. The process of allocation concealment will be implemented by the utilization of sealed envelopes.

Sample size calculation

Based on an expected recurrence rate of 3.33% to 16.7% for CLAu and a power of 80%, a total of 68 patients (34 per group) is required, accounting for a 20% loss to follow-up. The sample size was determined to ensure statistical significance in detecting differences in recurrence rates.

All procedures will be performed by two surgeons (EOGH and NKL). Ethics approval was obtained from our Institutional Review Board (CIRB Ref No.: CI-049–2023), and this trial has been registered (Clinical Trials Registration NCT06402643).

Participants and recruitment

Individuals who have been diagnosed with primary pterygium will be invited to take part in the study once they have provided formal authorization through a letter of informed consent. Clinical grading of pterygium will be based on the classification of Tseng et al. [15].

Inclusion: Adults diagnosed with primary pterygium.

Exclusion: Patients with autoimmune diseases, collagenopathies, glaucoma, prior ocular surgery, or significant ocular surface disease.

All subjects will be recruited and provided with written informed consent that explains the details of the trial, interventions, and study protocol in accordance with the principles of the Declaration of Helsinki. Inclusion and exclusion criteria are detailed in Table 1.

Table 1.

Inclusion and exclusion criteria for the trial participants

Inclusion criteria	Exclusion criteria
I. Patients over 18 years of age	I. Patients with rheumatoid arthritis
II. Patients with primary nasal pterygium with invasion equal to or greater than 2 mm into the cornea on its horizontal axis	II. Patients with collagenopathy
III. Patients who can present and continue follow-up for the duration of the study	III. Pregnancy
IV. Acceptance to participate in the study by signing the informed consent	IV. Infection, conjunctival inflammation, or ocular trauma
	V. Glaucoma
	VI. Previous ocular surgeries

CLAu procedure

The pterygium will be surgically removed utilizing conventional resection techniques, entailing a blunt resection of the head, neck, and body of the pterygium. After the resection, the surgical site will be polished using a surgical diamond burr if deemed necessary, and hemostasis will be achieved using bipolar cautery. In the case of CLAu, an autograft will be procured from the superior temporal bulbar conjunctiva. The autograft will be affixed to the surgical site using fibrin glue (Tisseel, Baxter AG Production Laboratory, Vienna, Austria).

Mini-SLET procedure

In addition to the standard resection technique, the surgical procedure will include the application of AM with surgical adhesive at the surgical site. Following this, limbal cells will be harvested from the limbus in a resection measuring 2 × 2 mm, divided into six fragments, and positioned along the limbus border on the AM. Unlike the approach in the previous study [6], this technique will omit the use of a second AM to cover the fragments. Instead, a bandage contact lens will be employed (Fig. 1).

Fig. 1.

A Nasal pterygium. B Resection of pterygium with exposed sclera. C Defect is covered with an AM and a 2 × 2 mm limbal stem cell resection. D Selected limbal epithelium tissue is cut into 6 to 8 pieces. E Alignment of the small limbus transplant in the AM near the limbus. F Place a bandage contact lens

After both surgical procedures, tobramycin will be administered three times a day until the corneal epithelium is healed. In addition, a topical fluorometholone will be given five times a day and tapered over 2 months. A systemic analgesic (Ketorolac) will be administered (3 times a day) to those patients with postoperative pain.

Environmental factors such as UV exposure and seasonal variations will be documented through structured patient questionnaires and clinical observation logs. Patients will be instructed to use UV-protective eyewear consistently, and adherence will be monitored at each visit. To further analyze the effects of these environmental factors, subgroup analyses will be conducted based on self-reported exposure levels. Additionally, we will collect meteorological data on UV index and humidity to correlate with recurrence trends. This approach ensures that the analysis systematically evaluates and accounts for these potential confounding factors.

Outcomes and data collection

Each patient will have a complete ophthalmological evaluation to measure the outcomes on the initial day following surgery, as well as during the second week and at monthly intervals of 1, 3, 6, and 12 months post-surgery. The main outcome is the recurrence rate, defined as any fibrovascular growth that passes onto the cornea across the limbus, according to the Tseng scale[15]. Postoperative symptoms (pain, foreign body sensation, irritation, and epiphora) will be assessed using the scale by Lim-Bon-Siong et al.[16]. During each visit, clinical observations will be documented using a digital slit lamp camera (Photo-Slit Lamp BX 900; Haag-Streit, Koeniz, Switzerland). The camera is equipped with 6×and 16×magnification capabilities. The results will be assessed by a sole author (GRVD) in a manner that ensures the masking of the evaluator’s identity.

Primary Outcome:

• Pterygium recurrence rate at 12 months.

Secondary Outcomes:

• Postoperative symptoms (pain, irritation, foreign body sensation, epiphora).

• Surgical complications.

• Cosmetic appearance.

Data will be collected using standardized forms and stored securely in a password-protected institutional database.

Randomization and blinding

Randomization for the study will be conducted on the day of surgery using simple randomization with a random numbers table: group I (control group) underwent pterygium excision with CLAu, and group II underwent pterygium excision with mini-SLET.

Randomization for the study will be conducted on the day of surgery utilizing a web-based, online platform with a sealed envelope system, available at https://www.sealedenvelope.com.

Data collection

Every patient will be provided with data collection forms that outline the details of each follow-up appointment and the specific data to be gathered during each visit. This includes assessments of visual acuity, findings from slit lamp clinical examinations, and the outcome above measures. The data will be saved securely and subsequently inputted into a desktop computer located at the Conde de Valenciana Ophthalmology Research Institute. This computer is password-protected and physically secured to ensure the confidentiality of the data. Additionally, daily backups of the data will be made onto hard drives. Access to the research data will be limited to designated investigators only. GRVD will exercise supervision and control over all access to the data. Upon the conclusion of the study, the research assistant will input the research data and ensure its storage for a period of up to five years. This practice is under the need to address any potential integrity concerns that may arise from subsequent publications. After this duration, the data shall be preserved under the supervision of NKL and EOGH.

Adverse events

The study will involve monitoring all subjects across all disciplines to identify any potential adverse effects that may arise during their participation. All untoward incidents will be documented and communicated to the institution’s review board.

Statistical analyses

The study will include a description of the demographic and baseline information, as well as the distinct characteristics of the eye for each treatment. The data analysis was conducted using the Statistical Package for the Social Sciences (SPSS; IBM, USA) version 17. The chi-square test was employed to assess the association between categorical variables. The Mann–Whitney U test, a statistical test suitable for nonparametric data, was employed to compare variables of a quantitative nature. Survival analysis following the Kaplan–Meier method will be employed. A specific methodology was employed to determine the recurrence rate from the intervention period until the study's conclusion.

The duration from the intervention’s implementation until the trial’s conclusion was determined using the Kaplan–Meier method. The mini-SLET’s safety evaluation will be conducted based on the assessment of its complication rate, using a cut-off threshold of less than or equal to the CLAu. The study of efficacy will be conducted after the follow-up period, utilizing the identical cut-off threshold.

Discussion

This study aims to establish the equivalence or superiority of the mini-SLET approach compared to CLAu concerning cosmetic results and recurrence. Furthermore, this clinical experiment may illustrate the potential extra benefits of mini-SLET, as its utilization may not be contingent upon individual variables or the conjunctival condition of the patient. In this study, we employed a research design aimed at assessing the comparative efficacy of two surgical procedures for treating primary pterygium. Additionally, we sought to examine the influence of these approaches on cosmetic outcomes and the likelihood of recurrence.

Potential risk factors for recurrence in surgical procedures include excessive suturing, poor peripheral dissection, undersized conjunctival graft, thick conjunctival graft with remnants of Tenon tissue, and postoperative graft retraction due to inadequate fixation [14, 17]. Superior results have been documented when employing conjunctival autografts in comparison to AM transplantation [1]. However, a recurrence incidence of 1% was observed in the published findings of surgical outcomes utilizing a pterygium excision approach that incorporated a limbal conjunctival autograft and a prophylactic subconjunctival AM graft [11]. Our hypothesis posits that including the stem cells found in the mini-SLET fragments may lead to decreased recurrence rates and, consequently, enhanced cosmetic effects, so we decided to implement a modification to the technique that was previously described (Fig. 2).

Fig. 2.

Schedule of enrolment, interventions, and assessments *Recommended content can be displayed using various schematic formats. See SPIRIT 2013 Explanation and Elaboration for examples from protocols. **List specific timepoints in this row

Because of the high rate of recurrence seen in the previous study (53%) [6], this one will also look at how environmental factors, specifically UV ray exposure and seasonal effects, affect both groups. Additionally, a modification to the technique will be implemented, involving the utilization of a single layer of AM. The knowledge that the high recurrence rate is due to the negative effects of this particular approach on the viability of the limbal graft is what inspired this adjustment.

In conclusion, this study aims to implement a substantial improvement to the technique employed in the last randomized clinical trial of mini-SLET [6], with the objective of enhancing the viability of corneal stem cells. The significance of this alteration has been recognized as important in enhancing the efficacy of this groundbreaking therapeutic approach. The present study builds upon prior research findings and knowledge gained to refine this methodology to provide patients with a more viable and efficacious therapeutic alternative.

Trial status

At the time of manuscript submission, we are in the process of recruiting patients.

Authors’ contributions

GRVD, GOM, CAMM: follow the patient, collect data, writing. ARM, AN: collected data, validation, and visualization. EOGH, NKL: planning, supervision, validation, visualization. All authors discussed the results and contributed to the final manuscript.

Funding

No funding or grant support.

Data availability

This study protocol is officially registered with ClinicalTrials.gov (Identifier: NCT06402643; registered on April 15, 2024). Data and materials will be publicly available upon the final report.

Declarations

Ethics approval and consent to participate

This study was conducted ethically following the World Medical Association Declaration of Helsinki. Being a case report, ethical approval was obtained. However, written informed consent was obtained from the patient to publish the details of their medical case and any accompanying images. The patient provided written consent regarding the publication of the present case report.

Consent for publication

The patient will be asked to give written informed consent to the publication of the details of their medical case and any accompanying images.

Competing interests

The authors declare no competing interests.