Base curves of bandage contact lenses and their effects on post Trans-PRK vision and pain: the study protocol for a randomized clinical trial

Abstract

Background

Transepithelial photorefractive keratectomy (Trans-PRK) is an effective and safe laser surgery for myopia. Following this procedure, a bandage contact lens is used to promote epithelial healing, reduce postoperative pain, and improve visual recovery. The base curve of these lenses may affect vision post-surgery, particularly in patients with steep corneas and high myopia. This study aims to investigate the impact of using bandage contact lenses with base curves of 8.4 mm versus 8.8 mm on visual recovery after Trans-PRK in patients with steep corneas and high myopia.

Methods

This is a randomized, double-blind, binocularly controlled, single-center trial. The study subjects are myopic patients scheduled for Trans-PRK. Both eyes in each patient will be treated consecutively with single-step Trans-PRK. After surgery, a contact lens with an 8.8-mm base curve will be placed on one eye, and a lens with an 8.4-mm base curve will be placed on the other. The primary objective is to determine the difference in early postoperative uncorrected visual acuity between the two eyes of patients with steep corneas and high myopia. Randomization will be conducted using a computer-generated random allocation sequence without blocks or restrictions. The sequence will be recorded in sealed opaque envelopes, maintained by the principal investigator until the trial’s conclusion. In this double-masked trial, subjects will not know which treatment each eye receives.

Discussion

This novel trial will provide information on how bandage contact lenses with different base curves promote epithelial healing and visual recovery after Trans-PRK, thus offering evidence for clinical practice.

Trial registration

ClinicalTrials.gov NCT06393855. Registered on May 1, 2024. https://clinicaltrials.gov/study/NCT06393855.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-025-09115-y.

Background

Refractive errors are the leading cause of visual impairment globally [1]. Laser corneal refractive surgery has emerged as an efficacious alternative for correcting refractive errors, potentially replacing traditional glasses or contact lenses [2]. Transepithelial photorefractive keratectomy (Trans-PRK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and small-incision lenticule extraction (SMILE) currently stand as the three most frequently employed corneal refractive surgeries [3]. The advantages of Trans-PRK include its effectiveness and safety. Trans-PRK does not require flap creation and provides greater postoperative corneal biomechanical stability compared to LASIK [4], especially in cases of corneal epithelial basement membrane lesions and thin corneas with high myopia [5]. A study demonstrated that Trans-PRK has favorable safety, efficacy, and predictability for correcting high myopia. Clinical outcomes of Trans-PRK were slightly superior to those of FS-LASIK [6]. Nevertheless, Trans-PRK is characterized by the lengthiest recovery period, heightened discomfort, and the potential for postoperative corneal haze [7]. In single-step Trans-PRK surgery, the epithelial layer and stroma are ablated in a single session. In Trans-PRK, there is no direct contact between surgical equipment and the cornea, eliminating the need for manual scraping or alcohol solutions [8]. Therefore, Trans-PRK requires a shorter surgical duration, reduces postoperative discomfort, accelerates wound healing, and facilitates faster visual recovery [9].

However, in cases of high myopia, a larger stromal ablation is necessary, leading to more extensive wound healing [10]. The epithelium typically repairs gradually within 7 days following surgery. The exposure of corneal nerve endings due to the loss of corneal epithelium is the primary cause of severe pain after photorefractive keratectomy [11]. After this procedure, a bandage contact lens is used to promote epithelial healing, reduce postoperative pain, and enhance visual recovery [12, 13]. Critical parameters for bandage contact lenses include oxygen permeability, moisture content, materials, and base curves, all of which influence the treatment process [14, 15]. Multiple studies have compared the healing durations and comfort levels of different types of bandage contact lenses [16–18]. A study compared outcomes using bandage contact lenses with base curves of 8.4 mm and 8.8 mm after Epi-LASIK, observing that the base curve impacted vision post-surgery, especially in patients with steep corneas and high myopia [19]. This study showed that individuals with preoperative high myopia (− 6 D to − 9 D) and high keratometric values (≥ 43 D) had superior uncorrected visual acuity (UCVA) with 8.8-mm base curve lenses compared to 8.4-mm base curve lenses. Nevertheless, it is essential to note that this study had a limited sample size, especially patients with steep corneas and high myopia.

Hence, we initiated a randomized, controlled, double-blind trial to investigate the impact of using bandage contact lenses with base curves of 8.4 mm versus 8.8 mm on visual recovery after Trans-PRK in patients with steep corneas and high myopia. Comparing bandage lenses in the contralateral eyes of the same individual after Trans-PRK may provide reliable conclusions about the optimal choice of bandage lenses.

Methods/design

Aim of study

This prospective, randomized controlled, double-blind, non-inferiority clinical trial aims to compare the efficacy of bandage contact lenses with two different base curves in promoting vision recovery and epithelial healing after Trans-PRK. The study is conducted at the outpatient Department of Ophthalmology, Dongyang People’s Hospital, located at No. 60 Wuning West Road, Dongyang City, Zhejiang Province, China. Ethical approval was obtained from the Dongyang People’s Hospital Ethics Committee. Written informed consent was obtained from participants prior to enrollment. The schedule for enrollment, intervention, and assessment was by the Standardized Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines (Fig. 1). We followed the SPIRIT reporting guidelines during the drafting of this article [20]. The study flow schedule is shown in Fig. 2.

Fig. 1.

Standardized Protocol Items: Recommendations for Interventional Trials (SPIRIT)

Fig. 2.

Study flow schedule

Participant eligibility

Inclusion criteria

The participants were aged 18–40 years. These participants intended to undergo Trans-PRK. The inclusion criteria were as follows: spherical equivalent refractive error between −6.00 and −8.00 D in either eye, astigmatism of no more than 2.0 D in either eye, and best spectacle-corrected visual acuity (BCVA) of 0 logMAR or better in both eyes. Participants had to be willing and able to participate in all required activities of the study.

Exclusion criteria

The exclusion criteria were as follows: patients with diabetes mellitus, systemic connective tissue disease, cardiovascular disease, epilepsy, eyelid abnormalities, corneal disease, glaucoma, or a history of ocular disease. Noncompliance with measurement at enrollment was also an exclusion criterion.

Randomization and masking

Implementation

Participants will be consecutively enrolled by the investigators and then randomly assigned to either group A (8.4 mm base curve lens in the right eye and 8.8 mm base curve lens in the left eye) or group B (8.8 mm base curve lens in the right eye and 8.4 mm base curve lens in the left eye).

Sequence generation

Randomization will be performed using a computer-generated random allocation sequence with no blocks or restrictions. After confirming all inclusion and exclusion criteria, participants will sign a written informed consent form. The randomization process will be accomplished using a web-based program.

Concealment mechanism

A researcher not involved in the follow-up study will create the randomization sequence in advance. The lead researcher randomly divided the participants into two groups; the groups (A and B) will be recorded, sealed in opaque envelopes, and kept by the principal investigator until the trial concludes. The principal investigator will open the opaque envelopes in case of emergencies, such as serious complications. When adding patient information, the data will be recorded on a printed form that includes the patient’s number and corresponding name. Each participant will be assigned a unique research identifier (participant number). This form is securely stored in a locked space, not on the server, and is accessible only to the principal investigator. It may be used to disclose personal data when unblinding is required.

Masked researchers were responsible for the ophthalmic measurements. The contact lens was placed by a single surgeon. The principal investigator will unpack the contact lenses at the end of the procedure and hand them to the surgeon. During the clinical trial, the surgeon, participants, data analysts, and masked researchers will be unaware of group assignments. Study data will be analyzed by masked data analysts.

Intervention

Both eyes were treated consecutively in each patient using single-step Trans-PRK with the SCHWIND Amaris 500 S excimer laser platform (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). Topical proparacaine hydrochloride eye drops 0.5% (Alcaine, Alcon, Fort Worth, TX, USA) were used to anesthetize the eyes, and povidone-iodine was used to disinfect the eyelid skin. After a Lid speculum was inserted, the other eye was blocked. Epithelial and stromal ablations were performed in a single continuous laser session on an excimer laser platform. After this step, mitomycin C 0.02% was applied to the stromal surface for 20 s, then rinsed with cold saline. A contact lens was placed on the cornea, with an 8.4-mm base curve in one eye and an 8.8-mm base curve in the fellow eye. Postoperative treatment was the same for all patients. Postoperatively, patients were given 0.5% topical levofloxacin four times a day until corneal re-epithelialization was complete. Fluorometholone (0.1%) drops were given four times a day for the first 4 weeks and then reduced every 4 weeks, depending on clinical appearance and haze level. Sodium hyaluronate eye drops were given four times a day for 4 months. Patients were followed up for 2 weeks postoperatively.

Primary outcome

Following surgery, eyes will be allocated to either group I (8.4 mm base curve bandage contact lenses) or group II (8.8 mm base curve bandage contact lenses). The primary outcome is to determine which base curve of bandage contact lenses is better for eyes with steep corneas and high myopia after Trans-PRK, by evaluating the uncorrected visual acuity (UCVA) (according to the logMAR scale) at 1 week postoperatively in these two groups. Other postoperative measurements were regarded as secondary outcomes.

Secondary outcome

The trial’s endpoint was set at 2 weeks post-surgery. The secondary outcomes were to compare differences in re-epithelialization, postoperative pain scores, and spherical equivalent after Trans-PRK. The ophthalmologist will examine the corneal epithelium of all eyes 1 day, 4 days, 1 week, and 2 weeks after surgery. The assessment of corneal epithelial defects involves measuring the horizontal and vertical diameters using a slit lamp beam with a ruler. The extent of corneal epithelial defects is determined by calculating the area of the ellipse (S = πa × b). Patients will be asked to complete a pain questionnaire at postoperative 0, 2 h and 1, 4, 7, 14 days. A visual analog scale (VAS) was employed to assess the severity of pain in each eye. The scores were defined as follows: 0 points: no pain; 1–3 points: mild pain, does not affect work or Life; 4–6 points: moderate pain, affects work but not Life; 7–10 points: severe pain, affects both work and life [13]. The ophthalmologist will perform computer optometry on all eyes 1 week and 2 weeks after surgery. Optometry is performed using a computerized optometer. The spherical equivalent (SE) was calculated using the formula DS + DC/2, where DS denotes the diopter sphere and DC denotes the diopter cylinder.

Sample size calculation

The sample size determination was based on the primary outcome, uncorrected visual acuity (UCVA) at 4 days postoperatively. This hypothesis was based on prior research findings [19]. Parameters for the sample size calculation included a significance level of 0.05, a power of 90%, an attrition rate of 10%, and a 1:1 allocation ratio. According to previous research, individuals with an 8.8-mm base curve demonstrated superior UCVA on day 4 postoperatively (0.21 ± 0.14) compared to those with an 8.4-mm base curve (0.31 ± 0.11) (P = 0.037). Two-sided calculations were performed using MedSci Sample Size tools. We need a total of 36 participants. The final sample size will be 36 eyes per group, totaling 72 eyes for the two groups.

Recruitment

At Dongyang People’s Hospital, nearly 500 patients undergo Trans-PRK for myopia every year, ensuring an ample pool of participants for our studies. Participants for this study were recruited from the pool of ophthalmology outpatients. The masked clinical research coordinator provided a comprehensive introduction to the study for potential participants. Those who expressed interest were invited to undergo a screening examination to evaluate their eligibility. During the enrollment visit, participants signed the informed consent document before the examination began.

Data collection, management, and monitoring

Before the study begins, all investigators received training in clinical trial protocols, data collection and management, and assessment methods. All original data of this trial will be recorded in the Microsoft Access database. All data entry will be done on a dedicated laptop by a trained operator assigned exclusively to this role during the trial. This is a mandatory procedure after surgery, and in order to minimize data loss, all participants signed an informed consent and promised to participate in the scheduled treatment period and follow the treatment. The researcher will maintain a friendly relationship with participants and regularly contact them through various methods (phone calls, text messages, WeChat) to promote retention and follow-up completion. All participants will not be charged for any examinations during the study period. Confidentiality and security of participant data will be guaranteed. All study-related data will be stored in secure, password-protected databases. Access to these databases will be restricted to authorized personnel only, such as the principal investigator, study coordinators, and authorized data analysts. These personnel will be trained in confidentiality and privacy procedures and will be required to sign confidentiality agreements. Each participant will be identified by a participant number (the subject’s identity will be withheld). After the study is completed, relevant documents will be stored in the Department of Ophthalmology, Dongyang People’s Hospital. All data will be retained for 5 years. Subjects’ data will not be used for other ancillary research. After this retention period, all personal information, whether electronic or paper-based, will be securely destroyed to ensure participant confidentiality is maintained.

Participants who cannot be followed up throughout the study period will be considered withdrawn from the study. If the subject has adverse reactions, such as keratitis and bandage lens rupture, the researchers have the right to withdraw participants from the study to ensure their safety. Additionally, participants can withdraw from the study at any time for any reason.

Any modifications to the study protocol require prior approval from the institutional ethics committee at Dongyang People’s Hospital. All changes will be recorded. Major protocol changes will be effectively communicated to trial participants through oral explanations, written notifications, and other means. Participants can ask questions, express any concerns, and seek clarifications.

The principal investigator and data analyst are responsible for securing and monitoring data collection and interpretation, as well as being involved in project management, analysis of data, data collection, and observations, and they will jointly interpret the results. To ensure the integrity of the study and compliance with regulatory standards, an audit will be conducted after participant enrollment and data collection phases. The audit will be performed by an independent team, not involved in the direct conduct of the study, comprising physicians and medical statisticians. Any findings from the audit will be documented in an audit report, which will be reviewed by the principal investigator and relevant stakeholders. If necessary, corrective actions will be implemented to address any issues identified during the audit.

Statistical analysis

Statistical analysis will be performed using SPSS software (version 25.0, SPSS, Chicago, IL, USA). Descriptive statistics will summarize the data, presenting mean (standard deviation, SD) for normally distributed continuous variables, median (interquartile range, IQR) for non-normally distributed continuous variables, and frequency (percentage) for categorical variables. Categorical variables will be expressed as numbers and frequencies. Group differences will be assessed using Fisher’s exact test. Continuous variables will be presented as mean ± SD. The normality of continuous variables will be evaluated using the Kolmogorov–Smirnov test. Normally distributed data will be analyzed using an independent t-test, whereas non-normally distributed data will be analyzed using the Wilcoxon signed-rank test. All statistical tests will be two-sided, and a P value less than 0.05 will be considered statistically significant. Participants who do not follow the protocol (e.g., missing follow-up visits, or incorrect medication use) may be withdrawn from the study or excluded from the analysis. For cases where post-treatment outcomes are missing, the last available data point may be used to estimate the missing values.

Dissemination

The trial results will be disseminated through publication in a peer-reviewed journal and shared with the media and the public. Approval from all researchers will be obtained prior to the submission of any study-related paper for publication. No additional participant data or biospecimens will be collected without further consent. Moreover, any presented or published data will not contain information that could disclose the identity of the participants.

Availability of data and materials

The datasets generated during this trial will not be made publicly available. However, researchers may request access to the data for research purposes. The comprehensive study protocol and statistical analysis plan will initially be uploaded to ClinicalTrials.gov or, if required, included as a supplement in a scientific journal publication.

Post-trial care

The bandage contact lenses will be removed after one week. The trial’s endpoint was set at two weeks post-surgery. The trial’s endpoint was set at two weeks post-surgery. After the trial, participants’ post-trial care will follow standard clinical practice. Fluorometholone (0.1%) drops will be administered four times a day for the first 4 weeks, then reduced every four weeks depending on clinical appearance and haze level. Sodium hyaluronate eye drops will be used four times a day for 4 months. At the end of the trial, participants will be asked whether they received any other interventions. During the trial, the use of ocular medications or treatments, other than essential ones, is prohibited. The use of medications for conditions other than ocular diseases is allowed, and this will be reported in the study results.

Adverse events

Adverse events that may occur, though very rare, include haze, broken bandage contact lens, infection, bandage contact lens dislodgement, and periocular swelling. If adverse events occur, appropriate therapies will be promptly administered. All adverse events will be recorded and reported to the centralized institutional review board and institution heads within 24 hours. Any damage caused by the test will be compensated according to the contract terms.

Discussion

Bandage contact lenses are used to protect the cornea, promote epithelial healing, and relieve pain during postoperative recovery. While comparisons of bandage contact lenses made from different materials exist, there is no clear conclusion on the protective effect of lenses with different base curves after myopic laser surgery. This trial aimed to investigate the effects of two bandage contact lenses with different base curves on promoting epithelial healing and visual recovery after Trans-PRK. This is the first randomized controlled trial to evaluate the efficacy of two different bandage contact lenses with base curves of 8.4 mm and 8.8 mm after Trans-PRK for high myopia. Dissemination strategies will include publications in peer-reviewed journals and presentations at conferences. In summary, the results of this trial may influence clinical practice and help select better bandage contact lenses for clinical use.

Trial status

This is the first version of the protocol 2024.06 (published on 01.05.2024). Recruitment for the study commenced in June 2024. Due to the slow pace of recruitment, it is initially planned to conclude by December 2025.

Abbreviations

Trans-PRK

Transepithelial photorefractive keratectomy

BCVA

Best spectacle-corrected visual acuity

BC

Base curves

BCL

Bandage contact lenses

Authors’ contributions

Gengmin Tong conceived the study, initiated the study design, developed the methodology, and commented on the initial drafts of the manuscript. Hangshuai Zhou and Yanhua Jin contributed to the study design and the critical revision of the manuscript. Yuanhui Jin was involved in the study design and the revision of the manuscript. All authors read and approved the final manuscript. All authors are affiliated with the Dongyang People’s Hospital.

Funding

This study has no sponsor.

Data availability

The datasets generated during this trial will not be made publicly available. However, 40 researchers may request access to the data for research purposes. The comprehensive study 41 protocol and statistical analysis plan will initially be uploaded to ClinicalTrials.gov or, if 42 required, included as a supplement in a scientific journal publication.

Declarations

Ethics approval and consent to participate

The trial protocol (dated April 19, 2024) adheres to the principles of the Declaration of Helsinki and has been approved by the Ethics Committee of Dongyang People’s Hospital (Approval No. [Dongrenyi 2024-YX-112]). The protocol was publicly registered on ClinicalTrials.gov (NCT<06393855>) on May 1, 2024. Informed consent will be acquired from all study participants at the time of their recruitment. Modifications to the protocol that may impact the study’s conduct, such as changes in study objectives, design, sample size, or procedures, will require formal protocol amendments. These amendments must be approved by the Institutional Review Board before implementation. Minor protocol adjustments, deemed to have no impact on the study, will be sanctioned by the principal investigator and documented in a memorandum.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.