Perioperative low-level light therapy for ocular surface protection in patients undergoing Femto-LASIK: a prospective double-masked,randomized controlled study

Abstract

Background:

Dry eye disease (DED) is among the most common complications experienced after femtosecond laser-assisted in situ keratomileusis (Femto-LASIK), often affecting visual recovery, as well as patient satisfaction. Low-level light therapy (LLLT) has shown benefits in various ocular surface diseases, but its role in refractive surgery remains underexplored. This study aimed at evaluating the efficacy of perioperative LLLT in preserving tear film parameters and reducing ocular discomfort symptoms after Femto-LASIK.

Methods:

In this prospective multicentric, randomized, double-masked, sham-controlled clinical study, adult patients undergoing Femto-LASIK were randomized (1:1) to receive periocular LLLT (633 ± 10 nm, 15 min/session) or sham treatment 7 ± 2 days before and after surgery. Ocular surface evaluation was performed at baseline (T0), and 1 week (T1), 1 month (T2), and 3 months (T3) postoperatively. Outcomes were tear meniscus height (TMH), Schirmer test values, and Dry Eye Questionnaire-5 (DEQ-5) scores, noninvasive tear break-up time (NIBUT), and interferometry.

Results:

Forty eyes of 40 patients (mean age: 34.58 ± 5.67 years) were analyzed. In the LLLT group, tear film parameters and subjective symptoms remained stable throughout follow-up, with no statistically significant changes over time. Conversely, the control group showed a significant decline in TMH (0.27 ± 0.05 mm to 0.20 ± 0.05 mm; p < 0.001), Schirmer test (20.39 ± 10.84 mm/5’ to 15.65 ± 9.02 mm/5’; p = 0.022), and a significant worsening in DEQ-5 scores (3.53 ± 4.10 to 5.94 ± 2.79; p = 0.005). Between-group comparisons demonstrated in the LLLT group significantly higher TMH at T2 (p = 0.034) and T3 (p = 0.016), higher Schirmer values at T2 (p = 0.048) and T3 (p = 0.018), and lower DEQ-5 scores at T1 (p = 0.041), T2 (p = 0.029), and T3 (p = 0.018). NIBUT and interferometry showed no significant between-group differences at any time point. No treatment-related adverse events were observed.

Conclusion:

Perioperative LLLT appears to be a safe and well-tolerated adjunctive treatment that may help preserve tear volume and support postoperative comfort after Femto-LASIK. These findings suggest a potential role for LLLT in perioperative refractive surgery care, although further studies are warranted to confirm its clinical benefit.

Keywords

DED dry eye disease Femto-LASIK low-level light therapy ocular surface photobiomodulation refractive surgery

Introduction

Dry eye disease (DED) is one of the most frequent complications following laser refractive surgery, including femtosecond laser-assisted in situ keratomileusis (Femto-LASIK). It can adversely affect visual quality, patient comfort, and satisfaction, and may influence overall surgical outcomes.^1,2 Femto-LASIK is a refinement of conventional LASIK in which the corneal flap is created with a femtosecond laser rather than a mechanical microkeratome.³ Compared with photorefractive keratectomy (PRK), it offers faster visual recovery, less postoperative pain, and reduced epithelial healing time.⁴ Compared with microkeratome-assisted LASIK, it provides more precise and reproducible flap architecture, with a lower incidence of flap-related complications.⁵ Nevertheless, after surgery, ocular discomfort symptoms are still frequently reported, highlighting the need for strategies that protect the tear film and ocular surface integrity in the perioperative period.^6–9

Low-level light therapy (LLLT) is a non-thermal photobiomodulation technique that delivers light in specific wavelengths, typically in the red and near-infrared spectrum, to stimulate cellular activity without causing tissue damage.¹⁰ Originally developed for dermatological uses such as wound healing and skin rejuvenation, more recently it has been applied in the ophthalmic field for conditions like meibomian gland dysfunction (MGD) and DED.¹¹ Evidence suggests that LLLT can enhance meibomian gland secretion quality, modulate inflammatory pathways, improve mitochondrial function, and increase local microcirculation, ultimately supporting tear film stability.¹²

While its benefits have been demonstrated in various ocular surface diseases (OSD) and in the perioperative management of cataract surgery,¹³ its role in preventing postoperative DED after refractive procedures has not been extensively investigated. This study was designed to evaluate whether perioperative LLLT can reduce postoperative ocular discomfort symptoms and preserve ocular surface status after Femto-LASIK.

Methods

Study design and participants

This prospective multicentric, randomized, double-masked, sham-controlled study was conducted between August 2024 and June 2025 at two centers: Centro Vista Eye Clinic and Cai Ferate Clinical Hospital. Ethical approval for the study was obtained from the Ethics Committee of the Cai Ferate Clinical Hospital of Iasi, Romania (approval number: 54/29.07.2024). All procedures performed in the study involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments. Written informed consent was obtained from all participants prior to inclusion in the study.

Consecutive adult patients (aged ⩾18 years) scheduled to undergo Femto-LASIK surgery were screened for eligibility and considered for enrollment. Eligible participants were required to meet the following inclusion criteria: age ⩾18 years, clinical suitability for Femto-LASIK based on refractive stability and corneal parameters, absence of preexisting OSD, and willingness to complete all follow-up visits with provision of written informed consent. Exclusion criteria for both study groups included a prior diagnosis of OSD or dry eye disease (DED), any history of ocular surgery in either eye, ocular comorbidities potentially affecting tear film or corneal integrity, current or regular use of topical ocular medications (e.g., lubricants, corticosteroids, and cyclosporine), device-based therapies, or oral supplements for OSD/DED, systemic medications known to be associated with DED (such as diuretics, antidepressants, antihistamines, or hormone replacement therapy), autoimmune diseases (e.g., Sjögren’s syndrome), and any intraoperative or postoperative complications that could interfere with reliable ocular surface assessment. The right eye of each patient was included in the study. Participants were randomly assigned in a 1:1 ratio to receive either perioperative LLLT or a sham procedure, using a computer-generated sequence (http://www.sealedenvelope.com). Allocation was concealed by means of sealed, opaque envelopes to ensure blinding. The study was double blinded: neither the participants nor the outcome assessors were aware of the treatment allocation, ensuring unbiased assessment of clinical outcomes.

Interventions

Participants assigned to the treatment group received periocular LLLT sessions using the Eye-light^® device (Espansione Marketing S.p.A, Bologna, Italy) with wavelengths of 633 ± 10 nm. Each session lasted 15 min and was conducted 7 days before and 7 days after refractive surgery. Sham-treated controls underwent the same procedure using the device’s demo light mode, which delivered <30% of the full treatment power, effectively simulating a standard LLLT session for patients without providing therapeutic exposure, as previously described.¹³

All surgeries were performed by two experienced surgeons using the same standardized surgical techniques under topical anesthesia. A femtosecond laser was used to create a corneal flap with a target thickness of approximately 110 µm and a diameter of 8.5–9.0 mm. The flap was lifted, and stromal ablation was performed with an excimer laser according to the patient’s refractive error and corneal topography. The flap was repositioned without sutures and aligned carefully to avoid striae. Standard postoperative therapy included topical antibiotics and corticosteroids for 1 week, followed by tapering steroids for an additional 2 weeks, and preservative-free artificial tears for at least 3 months. Only eyes without intraoperative or postoperative complications were included in the final analysis.

Outcome measures

Clinical assessments were conducted at four time points: 1 week preoperatively before the first LLLT/sham session (T0), 1 week postoperatively before the second LLLT/sham session (T1), 1 month postoperatively (T2), and 3 months postoperatively (T3). At each visit, a standardized, non-invasive ocular surface evaluation was carried out. The IDRA^® Ocular surface analyzer (SBM SISTEMI, Inc., Torino, Italy) was utilized to automatically measure and analyze several key parameters related to tear film stability. These included: noninvasive tear break-up time (NIBUT), interferometry, and tear meniscus height (TMH). In addition, the Schirmer test and the Dry Eye Questionnaire-5 (DEQ-5) were also performed.

All assessments were performed under consistent environmental conditions by the same experienced examiner for each center, who was masked to the treatment allocation to ensure unbiased data collection. Figure 1 illustrates the timeline of ocular surface evaluations and treatment interventions.

Figure 1.

Schematic overview of the timing of ocular surface assessments and treatments. Patients underwent an ocular surface evaluation 1 week before and 1 week after Femto-LASIK surgery, followed by either low-level light therapy (LLLT, left panel) or sham treatment (right panel). Further ocular surface examinations were performed in both groups 1 month and 3 months postoperatively.

Statistical analysis

Statistical analyses were performed using SPSS for Macintosh (version 30.0.0.0, SPSS Inc., Chicago, IL, USA). Quantitative variables were expressed as mean ± standard deviation (SD), and the Shapiro–Wilk test was used to assess data normality. Between-group comparisons for continuous variables were conducted using Mann–Whitney U tests. Categorical variables were compared using Fisher’s exact test. To evaluate interaction effects between treatment and time, a two-way mixed ANOVA was applied. Within-group changes were analyzed using repeated-measures ANOVA, and one-way ANOVA was used to compare groups at each follow-up time point.

Sample size calculation

An a priori power analysis was conducted using G*Power (version 3.1.9.6) for a repeated-measures ANOVA with a within–between interaction (F-test). The analysis assumed a medium effect size (f = 0.25), α = 0.05, desired power (1−β) = 0.95, two groups, four repeated measurements, a correlation among repeated measures of 0.5, and a nonsphericity correction ε = 1. The required total sample size was 36 participants. Our actual sample size (n = 40) exceeded this requirement, providing sufficient power to detect an effect of the specified magnitude. A p value < 0.05 was considered statistically significant.

Results

Study population

A total of 105 patients were evaluated for eligibility during the study treatment. Among these, 44 were excluded for the following reasons: lack of inclusion/exclusion criteria (n = 25), refusal to participate (n = 15), and other reasons (n = 4). The remaining 61 patients were randomized, with 31 assigned to the LLLT group and 30 to the sham group. During the study period, 16 patients were lost to follow-up (6 in the LLLT group and 10 in the sham group) primarily due to scheduling conflicts or other personal issues, while 5 were excluded due to postoperative complications unrelated to the study treatment. Ultimately, 40 patients (19 males, 21 females; mean age of 34.58 ± 5.67 years) completed the entire study, and the right eye of each participant was included in the final analysis. Of these, 23 patients received LLLT and 17 received sham treatment. No significant differences in baseline demographics were observed between the groups in terms of age (34.96 ± 5.83 vs 34.06 ± 5.47 years; p = 0.118, Mann–Whitney U test) or sex distribution (10 males (43.5%) and 13 females (56.5%) vs 9 males (52.9%) and 8 females (47.1%); p = 0.498, Fisher’s exact test). The patient recruitment and allocation processes are illustrated in Figure 2.

Figure 2.

CONSORT flow diagram of the randomized controlled trial. This diagram depicts the flow of participants through the study, including those screened for eligibility, randomized, assigned to each intervention group, and monitored for the duration of the trial.

Ocular surface parameters

A comprehensive assessment of ocular surface status was performed at baseline (T0), 1 week (T1), 1 month (T2), and 3 months (T3) after refractive surgery to evaluate the effect of perioperative LLLT on both subjective symptoms and objective parameters of DED. Time-dependent changes within each group and comparisons between the treatment groups at each time point were analyzed to identify statistically and clinically meaningful effects, as summarized in Table 1.

Table 1.

Ocular parameters measured during each time point in patients undergoing Femto-laser in situ keratomileusis (LASIK) surgery and randomized to receive low-level light therapy or sham treatment.

Parameter	Group	T0 (1 week before)	T1 (1 week after)	T2 (1 month after)	T3 (3 months after)	p Value*
NIBUT (s)	LLLT	14.52 ± 9.71	13.73 ± 6.66	18.37 ± 8.27	13.76 ± 5.21	0.125
	Control	16.74 ± 6.10	14.09 ± 7.23	14.96 ± 6.36	14.44 ± 6.89	0.061
	p Value^†	0.413	0.341	0.164	0.724
Interferometry (nm)	LLLT	76.48 ± 19.55	77.17 ± 16.97	77.09 ± 14.31	74.52 ± 13.93	0.926
	Control	73.35 ± 11.82	80.71 ± 13.54	83.06 ± 15.24	76.82 ± 15.10	0.179
	p Value^†	0.563	0.484	0.212	0.621
TMH (mm)	LLLT	0.25 ± 0.08	0.24 ± 0.07	0.26 ± 0.07	0.28 ± 0.08	0.443
	Control	0.27 ± 0.05	0.23 ± 0.03	0.22 ± 0.04	0.20 ± 0.05	<0.001
	p value^†	0.472	0.643	0.034	0.016
Schirmer test (mm/5’)	LLLT	20.09 ± 10.97	17.65 ± 10.03	20.87 ± 9.88	20.95 ± 9.29	0.357
	Control	20.39 ± 10.84	15.18 ± 11.14	15.12 ± 7.57	15.65 ± 9.02	0.022
	p Value^†	0.953	0.466	0.048	0.018
DEQ-5	LLLT	3.78 ± 3.30	4.13 ± 2.92	3.87 ± 3.30	3.83 ± 2.60	0.948
	Control	3.53 ± 4.10	6.18 ± 3.56	5.83 ± 2.96	5.94 ± 2.79	0.005
	p Value^†	0.830	0.041	0.029	0.018

Bold indicates statistical significance.

Time effect in each group; repeated-measures ANOVA.

†

Treatment effects at each time point; one-way ANOVA.

ANOVA, analysis of variance; DEQ-5, Dry Eye Questionnaire-5; LLLT, low- level light therapy; NIBUT, Non-invasive break-up time; TMH, tear meniscus height.

Tear meniscus height

TMH values remained stable in the LLLT group across all time points (from 20.09 ± 10.97 mm/5’ at T0 to 17.65 ± 10.03 mm/5’ at T1, 20.87 ± 9.88 mm/5’ at T2, and 20.95 ± 9.29 mm/5’ at T3; p = 0.357), suggesting no significant postoperative changes of tear film volume. In contrast, the control group showed a significant decrease in TMH values (from 0.27 ± 0.05 mm at T0 to 0.23 ± 0.03 mm at T1, 0.22 ± 0.04 mm at T2, and 0.20 ± 0.05 mm at T3; p < 0.001). Between-group comparisons revealed no significant differences at T0 (p = 0.472) or T1 (p = 0.643), whereas TMH was significantly higher in the LLLT group at T2 (0.26 ± 0.07 mm vs 0.22 ± 0.04 mm; p = 0.034) and T3 (0.28 ± 0.08 mm vs 0.20 ± 0.05 mm; p = 0.016), supporting a protective effect of LLLT on tear film volume compared with controls.

Schirmer test

In the LLLT group, Schirmer test values remained stable in the LLLT group across all time points (from 19.50 ± 10.88 mm/5’ at T0 to 18.63 ± 9.87 mm/5’ at T1, 20.43 ± 9.57 mm/5’ at T2, and 20.02 ± 9.25 mm/5’at T3; p = 0.636). In contrast, the control group showed a significant decrease in Schirmer test values (from 20.39 ± 10.84 mm/5’ at T0 to 15.18 ± 11.14 mm/5’ at T1, 15.12 ± 7.57 mm/5’ at T2, and 15.65 ± 9.02 mm/5’ at T3; p = 0.022), indicating a reduction of tear production. Between-group comparisons showed no significant differences at baseline (p = 0.953) or at T1 (p = 0.466), whereas Schirmer values were significantly higher in the LLLT group at T2 (20.87 ± 9.88 mm/5’ vs 15.12 ± 7.57 mm/5’; p = 0.048) and T3 (20.95 ± 9.29 mm/5’ vs 15.65 ± 9.02 mm/5’; p = 0.018), supporting a protective effect of LLLT on tear production.

Dry Eye Questionnaire-5

In the LLLT group, DEQ-5 scores remained stable throughout follow-up (from 3.78 ± 3.30 at T0–4.13 ± 2.92 at T1, 3.87 ± 3.30 at T2, and 3.83 ± 2.60 at T3; p = 0.948), indicating no significant change in subjective symptoms over time. Conversely, the control group exhibited a significant worsening, with DEQ-5 scores increasing from 3.53 ± 4.10 at T0 to 6.18 ± 3.56 at T1, 5.83 ± 2.96 at T2, and 5.94 ± 2.79 at T3 (p = 0.005). Between-group comparisons showed no significant difference at baseline (p = 0.830), whereas statistically significant differences were observed at T1 (4.13 ± 2.92 vs 6.18 ± 3.56; p = 0.041), T2 (3.87 ± 3.30 vs 5.83 ± 2.96; p = 0.029), and T3 (3.83 ± 2.60 vs 5.94 ± 2.79; p = 0.018), supporting better control of subjective symptoms in patients treated with LLLT.

Noninvasive break-up time

No statistically significant within- or between-group differences were observed in NIBUT values.

In the LLLT group, mean NIBUT values were 14.52 ± 9.71 s at T0, 13.73 ± 6.66 s at T1, 18.37 ± 8.27 s at T2, and 13.76 ± 5.21 s at T3, with no significant time effect (p = 0.125). Similarly, in the control group, NIBUT values were 16.74 ± 6.10 s at T0, 14.09 ± 7.23 s at T1, 14.96 ± 6.36 s at T2, and 14.44 ± 6.89 s at T3, also without a significant time effect (p = 0.061). Between-group comparisons showed no statistically significant differences at any time point (T0 p = 0.413; T1 p = 0.341; T2 p = 0.164; T3 p = 0.724), indicating that tear film stability, as assessed by NIBUT, was not significantly influenced by LLLT in this cohort.

Interferometry

No statistically significant within- or between-group differences were observed in interferometry values. In the LLLT group, mean interferometry values were 76.48 ± 19.55 nm at T0, 77.17 ± 16.97 nm at T1, 77.09 ± 14.31 nm at T2, and 74.52 ± 13.93 nm at T3, with no significant time effect (p = 0.926). Similarly, in the control group, values were 73.35 ± 11.82 nm at T0, 80.71 ± 13.54 nm at T1, 83.06 ± 15.24 nm at T2, and 76.82 ± 15.10 nm at T3, without significant changes over time (p = 0.179). Between-group comparisons showed no statistically significant differences at any time point (T0 p = 0.563; T1 p = 0.484; T2 p = 0.212; T3 p = 0.621), indicating that tear lipid layer thickness, as assessed by interferometry, was not significantly influenced by LLLT in this cohort.

Safety and tolerability

No adverse events related to the treatment sessions were reported in either group throughout the treatment and follow-up periods. The procedure was well tolerated and did not interfere with the standard postoperative course.

Discussion

The present study demonstrated that prophylactic LLLT administered 1 week before and 1 week after Femto-LASIK surgery was associated with a preservation of TMH, Schirmer values, and patient ocular comfort; in contrast, these parameters worsened postoperatively in the control group due to the well-known surgery-induced detrimental effects on ocular surface. These findings suggest that LLLT may maintain the ocular surface status and mitigate postoperative decline of its parameters.

DED following corneal refractive surgery remains one of the most prevalent postoperative concerns, with a multifactorial pathophysiology involving both structural and functional alterations of the ocular surface system.¹⁴ The afferent sensory nerves of the cornea and conjunctiva interact with efferent autonomic pathways to the lacrimal gland to regulate tear production and composition. The surgical disruption of this reflex arc leads to hyperosmolarity, inflammation, and epithelial cell apoptosis.^15–17 In Femto-LASIK, the main mechanism involved is the transection of corneal nerves occurring during flap creation, extending over more than 300°, followed by excimer laser ablation. This extensive denervation decreases corneal sensitivity, impairs the blink reflex, reduces tear secretion, destabilizes the tear film, and disrupts the release of neurotrophic factors.¹⁸ Further contributors include loss of conjunctival goblet cells from the suction ring, postoperative neurogenic inflammation, as well as impairments in corneal curvature that affect lid-cornea interaction and meibomian gland function.^19–21 The epidemiology of post-LASIK DED varies widely, with reported prevalence from 36% to 75% depending on diagnostic criteria; almost all patients experience some degree of dryness immediately after surgery, peaking in the first week(s), and while most recover within 6–12 months, 8%–48% remain symptomatic thereafter.²² The PROWL study showed that one-third of patients with normal preoperative Ocular Surface Disease Index (OSDI) scores reported dryness 3 months postoperatively, with 4% experiencing severe symptoms.²³ Comparative evidence shows that SMILE, with only a 25°–50° side incision, preserves more nerve fibers and results in less severe, faster-resolving DED compared to LASIK. PRK avoids flap creation entirely, generally preserving the sub-basal plexus but still inducing temporary sensitivity loss from epithelial removal.^24–26

Management of refractive surgery-induced DED is multifaceted, ranging from first-line therapies like lubricants to anti-inflammatory, regenerative, and device-based treatments. Tear substitutes differ in composition: liposomes and lipid-based emollients, such as castor oil or flaxseed oil, reduce tear film evaporation, whereas demulcents, including carboxymethylcellulose, hyaluronic acid, and trehalose, enhance corneal surface coverage, hydration, and protection against oxidative stress. However, no single formulation has been conclusively demonstrated to be superior.^27–29 Topical cyclosporine A, an FDA-approved calcineurin inhibitor, increases goblet cell density, reduces apoptosis, and has demonstrated efficacy in post-LASIK DED, outperforming tear substitutes and diquafosol in some trials.^30,31 The latter, a P2Y2 receptor agonist, promotes aqueous and mucin secretion and is effective alone or in combination with sodium hyaluronate.³¹ Autologous serum and platelet-rich plasma supply growth factors, vitamins, and fibronectin, aiding epithelial repair; platelet-rich plasma may offer superior results in severe cases.³² Punctal plugs reduce tear drainage and are useful in selected patients, especially for postoperative aqueous deficiency.³³ Omega-3 fatty acids exert anti-inflammatory effects, improve goblet cell density, and support nerve regeneration.³⁴ Thermal eyelid therapies, including moist heat masks, vectored thermal pulsation (Lipiflow), and intense pulsed light, improve lipid layer quality and tear stability.^13,35,36 Intense pulsed light (IPL) has emerged as an effective device-based therapy for MGD and evaporative dry eye disease. By delivering high-intensity, polychromatic light to the periocular skin, IPL reduces telangiectatic vessels, decreases inflammatory mediator release, improves meibomian gland secretion quality, and enhances tear film stability.³⁷ Several clinical studies have demonstrated significant improvements in lipid layer thickness, tear break-up time, and patient-reported symptom scores following IPL treatment.^37–39 Given that evaporative mechanisms and meibomian gland alterations may contribute to postoperative tear dysfunction after refractive surgery, IPL represents an additional therapeutic modality that warrants consideration within the perioperative management algorithm. Less conventional methods, such as acupuncture, may enhance lacrimal secretion, though evidence is poor.⁴⁰

LLLT has emerged as a promising adjunct for OSD, exerting photobiomodulatory effects through enhanced mitochondrial function, modulation of inflammatory cytokines, increased local blood flow, and improved meibomian gland secretion.^10,41 In MGD and evaporative DED, LLLT has been shown to improve tear film stability and reduce symptoms, with Antwi et al. reporting that three sessions of 633 nm LLLT administered 7 days apart significantly enhanced TMH, lipid layer thickness, meibomian gland secretion quality, and OSDI scores without adverse effects.⁴² Perioperative use of LLLT in cataract surgery is particularly well documented. In fact, two prospective randomized controlled clinical trials demonstrated that pre- and postoperative LLLT significantly improved tear stability and osmolarity and reduced ocular discomfort symptoms in patients undergoing cataract surgery.^13,43 Such findings provide a compelling rationale for evaluating LLLT in refractive surgery, where postoperative DED is multifactorial, involving nerve transection, ocular surface inflammation, tear film instability, and meibomian gland alterations.

Our results confirm previous results in the setting of cataract surgery, with LLLT selectively improving tear film parameters while preserving epithelial integrity. In our cohort, maintenance of tear metrics and ocular comfort suggests that LLLT may preserve ocular surface health and mitigate postoperative symptoms. These effects are likely mediated through simultaneous targeting of multiple pathogenic pathways, including mitochondrial activation, cytokine modulation, and enhancement of lipid secretion.^10,11 The absence of adverse events further supports its favorable safety profile and noninvasive nature, suggesting that LLLT may be a feasible adjunct within perioperative protocols, although confirmation in larger studies is warranted. From a practical standpoint, preservation of tear volume and maintenance of subjective comfort during the early postoperative phase may translate into a smoother recovery experience for patients undergoing Femto-LASIK. Post-LASIK tear dysfunction syndrome encompasses a heterogeneous spectrum of postoperative alterations, including transient or persistent neurotrophic disease, tear film instability, true aqueous deficiency, and, in some cases, neuropathic pain states.⁴⁴ Within this complex pathophysiological framework, the stability of TMH and Schirmer values observed in our cohort, together with improved symptom control, suggests that perioperative LLLT may help mitigate the aqueous-deficient component of early postoperative dysfunction following corneal nerve transection.

Clinically, this may reduce early postoperative discomfort, decrease reliance on intensive lubricating regimens, and support a more favorable patient-perceived visual recovery during the first postoperative months. In an era where patient-reported outcomes and quality-of-vision metrics increasingly influence refractive surgery success, perioperative LLLT may represent a supportive adjunct to standard care, provided that its benefits are confirmed in larger randomized studies with longer follow-up and comprehensive assessment of tear film stability and corneal nerve function.

Limitations

Nonetheless, the following limitations must be acknowledged. The follow-up period was limited to 3 months, patients with preexisting OSD/DED were excluded, and all surgeries were performed in high-volume specialized centers, potentially limiting generalizability. Further research should explore optimal wavelength and energy parameters, the potential benefits of repeated postoperative sessions, and long-term effects over 6–12 months, as well as more in-depth analysis of corneal nerve metrics and function (sensitivity). An additional limitation of the present study is the absence of a direct comparison with other established device-based therapies for OSD, such as IPL or thermal pulsation systems (e.g., LipiFlow). While LLLT demonstrated beneficial effects on tear volume preservation and symptom control, the lack of a head-to-head comparison precludes conclusions regarding its relative efficacy or cost-effectiveness compared with these modalities. Future randomized trials directly comparing LLLT with other perioperative therapeutic strategies would help clarify its position within the broader management algorithm of post-refractive surgery tear dysfunction and define the most appropriate patient selection criteria.

Conclusion

Perioperative LLLT appears to be a safe and effective adjunctive strategy for preserving ocular surface health in patients undergoing Femto-LASIK. In this multicentric randomized controlled trial, LLLT was associated with better preservation of selected tear film parameters and improved postoperative comfort compared with sham treatment. These findings suggest that LLLT may represent a promising adjunct in perioperative refractive surgery protocols. However, given the modest sample size, limited 3-month follow-up, and the lack of significant effects on tear film stability parameters such as NIBUT and interferometry, larger randomized studies with longer follow-up are needed before routine clinical adoption can be recommended.

Footnotes

Acknowledgements

None.

Declarations

ORCID iDs

Valerio Calabresi

Filippo Lixi

Giuseppe Giannaccare

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