LLLT and IPL for Dry Eye Before Cataract Surgery: Why It Matters and When to Do It

Dry eye disease is present in a significant proportion of patients presenting for cataract surgery and is the most important modifiable factor affecting the accuracy of preoperative biometry and IOL power calculation. When dry eye is not identified and treated before cataract surgery, the resulting inaccuracy in keratometry measurements can lead to a refractive surprise after surgery that is difficult to correct and may require further intervention. Two technologies, low-level light therapy (LLLT) and intense pulsed light (IPL), have emerged as effective treatments for the meibomian gland dysfunction that underlies most evaporative dry eye. This post covers why cataract surgery makes dry eye worse, how dry eye compromises biometry, what the evidence shows for LLLT and IPL, when these treatments should be performed before cataract surgery in Melbourne, and when repeat therapy is needed.

Why cataract surgery makes dry eye worse

Cataract surgery worsens dry eye through several documented mechanisms. The corneal incision transects the nerve fibres that drive tear production and blink reflex. Surgical inflammation disrupts goblet cell function. Postoperative preserved antibiotic and steroid drops add a further ocular surface insult. The effect is most significant in patients with pre-existing meibomian gland dysfunction or dry eye disease. For patients in whom a premium IOL was implanted, postoperative dry eye is one of the most common sources of dissatisfaction because the optical quality of a premium lens is highly dependent on a stable tear film.

Dry eye disease is a multifactorial condition in which the tear film is inadequate or unstable. In most patients presenting for cataract surgery, the primary underlying mechanism is evaporative dry eye caused by meibomian gland dysfunction (MGD). The meibomian glands in the eyelids produce the lipid layer of the tear film that prevents evaporation. When meibomian gland function is impaired, the lipid layer is absent or of poor quality, the tear film evaporates too rapidly, and the corneal surface becomes irregular between blinks.

Cataract surgery reliably worsens dry eye in the postoperative period through several mechanisms, all of which have been documented in the peer-reviewed literature.

Corneal nerve transection is the most important mechanism. The corneal incision made during phacoemulsification transects the superficial corneal nerve fibres. These nerves are responsible not only for corneal sensation but also for the neural reflex arc that drives lacrimal gland secretion and regulates blink rate. Transecting these nerves reduces lacrimal gland stimulation and impairs the blink reflex, directly reducing both the aqueous and lipid components of the tear film. A review published in PubMed confirmed that corneal nerve transection is one of the primary mechanisms underlying postoperative dry eye after cataract surgery, alongside goblet cell loss and meibomian gland dysfunction (PubMed 26569526).

Surgical inflammation from the incision and phacoemulsification process disrupts goblet cell function and contributes to conjunctival inflammation that further destabilises the tear film. Benzalkonium chloride-preserved antibiotic and steroid drops used postoperatively add a further preservative-mediated ocular surface insult during the period of peak nerve disruption and healing.

The practical consequence is that patients who had mild or subclinical dry eye before surgery frequently develop symptomatic dry eye after surgery. Patients with pre-existing moderate dry eye consistently experience worsening symptoms and signs postoperatively. For guidance on managing dry eye in the cataract surgery recovery period, see the dedicated recovery guide.

How dry eye compromises biometry and IOL power calculation

Dry eye causes tear film instability that directly distorts keratometry measurements during biometry. Modern biometers measure corneal curvature by reflecting light from the anterior corneal surface, which is coated by the tear film. An unstable tear film produces inaccurate and variable keratometry readings that propagate through any IOL power formula, regardless of which formula is chosen. This is a measurement input error, not a formula error, and cannot be corrected by switching formulas.

Modern optical biometers including the IOLMaster 700 and Lenstar use optical coherence tomography or partial coherence interferometry to measure axial length, anterior chamber depth, lens thickness, and corneal curvature. The corneal curvature measurement (keratometry) is particularly sensitive to tear film quality because it is derived from the reflection of light from the anterior corneal surface. The anterior surface of the cornea is coated by the tear film. If the tear film is irregular or unstable, the reflected image used for keratometry is distorted, producing inaccurate keratometry readings.

A 2023 hospital-based study of 190 cataract patients found that tear film instability was present in 54.7 percent of patients presenting for surgery. Patients with tear film instability demonstrated significantly greater refractive prediction error (0.58 plus or minus 0.34 D) compared with those with a stable tear film (0.32 plus or minus 0.21 D). This difference in prediction error is clinically meaningful: a 0.25 D error in the intended refraction is detectable to most patients and a 0.50 D or greater error is likely to require glasses correction that the patient did not expect.

A 2024 study published in PMC found that corneal astigmatism measurements showed significant variability between repeated measurements in patients with dry eye disease (DED) but not in controls. After four weeks of lipid-containing artificial tear treatment, keratometric stability improved significantly, with significant changes in predicted IOL power observed between pre-treatment and post-treatment biometry. This study directly demonstrated that treating dry eye before biometry produces more accurate and more reproducible measurements (PMC12843478).

A further study using the OA-2000 biometer found that mean keratometry variation was significantly higher in dry eye patients than in non-dry eye controls (mean delta Km of 0.28 D versus 0.09 D in controls, p equals 0.005), with the percentage of eyes showing variation exceeding 0.5 D significantly different between groups.

The implications for surgical planning are clear. Performing biometry in a patient with undiagnosed or untreated dry eye produces measurements that are less accurate and less reproducible than those taken after the ocular surface has been optimised. The error introduced by dry eye cannot be corrected by choosing a better IOL power formula; it is a measurement input error that propagates through any formula used.

For toric IOL planning, the consequences of dry eye-related biometry error are compounded. Toric IOL power calculation depends not only on the magnitude of corneal astigmatism but on its axis. An unstable tear film produces not only variable magnitude readings but variable axis readings, increasing the risk of toric IOL misalignment and residual astigmatism after surgery.

What is LLLT and how does it work for dry eye?

Low-level light therapy (LLLT) applies near-infrared and red light to periocular tissue to stimulate meibomian gland function and reduce eyelid inflammation. The light increases eyelid temperature, liquefies inspissated meibum, improves gland secretory activity, and reduces inflammatory cytokines in the gland acini. Sessions take approximately 10 to 15 minutes, require no anaesthesia, and no light enters the eye during treatment.

LLLT, also known as photobiomodulation (PBM), involves the application of near-infrared and red light wavelengths to periocular tissue. The light penetrates the eyelid skin and meibomian gland tissue, activating intracellular photoreceptors and mitochondrial cytochrome c oxidase. This produces a cascade of cellular effects including increased ATP production, reduction of reactive oxygen species, anti-inflammatory cytokine modulation, and stimulation of cellular repair processes in the meibomian gland acinar cells.

In clinical terms, LLLT improves meibomian gland function by reducing gland inflammation, improving meibum quality, and stimulating meibomian gland secretory activity. It also raises eyelid temperature, which liquefies inspissated meibum in obstructed glands and facilitates expression of the secretion.

LLLT is typically delivered using a dedicated periocular device (such as the EYE-LIGHT PBM device or similar platforms) that applies light to the periocular skin and eyelids with the patient's eyes closed. Each session takes approximately 10 to 15 minutes and is comfortable and well-tolerated. No anaesthesia is required. No light enters the eye during closed-eye LLLT treatment.

What is IPL and how does it work for dry eye?

Intense pulsed light (IPL) therapy delivers polychromatic pulsed light to the periocular skin and lower eyelid margin to treat the meibomian gland dysfunction underlying most evaporative dry eye. IPL coagulates abnormal eyelid margin telangiectasia, warms gland tissue to liquefy obstructed secretions, and reduces Demodex populations. Sessions take 15 to 20 minutes with metallic corneal shields protecting the eye.

IPL, originally developed in dermatology for the treatment of skin conditions including rosacea and telangiectasia, has been used in ophthalmology for the treatment of MGD-related dry eye since the late 1990s. IPL delivers polychromatic pulsed light in wavelengths of approximately 500 to 1200 nm to the periocular skin and lower eyelid margin using a handheld device with a protective corneal shield in place.

The mechanisms by which IPL benefits MGD and dry eye include:

Photothermocoagulation of abnormal lid margin telangiectasia: these dilated vessels on the eyelid margin are a hallmark of MGD-associated rosacea and chronic blepharitis. IPL coagulates these vessels, reducing the inflammatory mediators they deliver to the meibomian gland tissue.

Thermal warming of meibomian glands: the light energy heats the eyelid tissue, melting inspissated meibum and facilitating expression of gland secretions.

Anti-inflammatory and anti-bacterial effects: IPL reduces Demodex mite populations on the eyelid margin and has direct anti-inflammatory effects on the conjunctiva and eyelid tissue.

IPL is performed with a conductive gel applied to the periocular skin, with metallic eye shields protecting the cornea. Each session takes 15 to 20 minutes and is generally well-tolerated. Mild transient erythema is common. It is contraindicated in patients with very dark skin types (Fitzpatrick type V to VI) due to the risk of skin pigmentation changes, and in patients with active skin infections or inflammatory dermatological conditions in the treatment area.

Evidence for LLLT in dry eye before and after cataract surgery

LLLT has a growing evidence base for dry eye treatment, including a 2024 prospective randomised double-masked controlled trial specifically evaluating LLLT before and after cataract surgery. That trial found that two perioperative LLLT sessions improved tear film stability and reduced ocular discomfort in cataract patients, establishing the first RCT evidence specifically for LLLT in the peri-operative cataract setting.

A prospective randomised double-masked controlled clinical trial published in the British Journal of Ophthalmology in 2024 specifically evaluated two sessions of LLLT performed before and after cataract surgery for prophylaxis of postoperative dry eye. The study found that LLLT was effective in ameliorating tear film stability and reducing ocular discomfort symptoms in patients undergoing cataract surgery. This is the first randomised controlled trial to directly evaluate LLLT in the cataract surgery setting and establishes a specific evidence base for its use as peri-operative treatment (Giannaccare et al., BJO 2024;108(8):1172-1176. doi: 10.1136/bjo-2023-323920).

A prospective randomised observer-masked trial published in Scientific Reports in 2022 found that LLLT significantly improved corneal fluorescein staining scores, OSDI scores, tear break-up time, Schirmer test results, and meibomian gland dysfunction index compared with placebo. Significant improvement was observed within four weeks of commencing treatment, suggesting relatively rapid onset of benefit (Park et al., Sci Rep. 2022. doi: 10.1038/s41598-022-07427-6).

A systematic review published in Ophthalmic and Physiological Optics in 2024 found that LLLT significantly improved non-invasive tear break-up time, tear meniscus height, tear film lipid layer thickness, OSDI score, Schirmer test, and meibum quality score, with eyelid temperature increases of approximately 7 degrees Celsius confirming the thermal mechanism of meibomian gland stimulation (Antwi et al., Ophthalmic Physiol Opt. 2024. doi: 10.1111/opo.13371).

Evidence for IPL in dry eye

IPL has a larger and more established evidence base than LLLT for meibomian gland dysfunction-related dry eye. Multiple randomised trials and systematic reviews confirm that IPL with meibomian gland expression significantly improves tear break-up time, meibum quality, and OSDI scores. A 2024 systematic review and meta-analysis confirmed IPL as an effective treatment for MGD-related dry eye.

A randomised controlled study published in PLOS ONE in 2022 evaluated four sessions of IPL plus meibomian gland expression (MGX) at two-week intervals against sham plus MGX. IPL significantly improved fluorescein tear break-up time, meibomian gland score, eye dryness score, and the expressibility and quality of meibum in both upper and lower eyelids compared with sham. The combination of IPL with meibomian gland expression at the same session is the current standard approach in clinical practice (Toyos et al., PLOS ONE 2022. doi: 10.1371/journal.pone.0270268).

A 2024 systematic review and meta-analysis published in PubMed evaluating the effectiveness and safety of IPL for dry eye due to MGD concluded that IPL significantly improved dry eye symptoms and signs including OSDI scores, tear break-up time, and lipid layer thickness. The review confirmed IPL as an effective treatment for MGD-related dry eye (PubMed 39611367).

A 2024 study published in Healthcare analysing temporal changes in tear film stability across multiple IPL sessions found significant improvements in non-invasive first break-up time, non-invasive average break-up time, tear meniscus height, and ocular surface inflammation markers across sequential sessions. Improvements accumulated across sessions with meaningful changes observable after the first session and continuing to improve through subsequent sessions (Pac et al., Healthcare 2024. doi: 10.3390/healthcare12111119).

A randomised controlled trial published in PMC in 2023 comparing combined IPL plus LLLT against a control group found significant improvements in tear break-up time and symptomatology in the treatment group at one and two months after the final treatment session, with no adverse effects including skin pigmentation or burns observed (PMC10276683).

Time to maximum efficacy and the need for repeat sessions

The time course of treatment response determines when biometry should be repeated after LLLT or IPL. For IPL, maximum benefit is typically reached four to six weeks after the last session of a standard course. For LLLT, significant improvement is measurable at four weeks from commencement. Most patients require maintenance sessions every six to twelve months to sustain the benefit, as MGD is a chronic condition that does not resolve permanently after a single treatment course.

For IPL, the standard initial treatment course is three to four sessions at two-week intervals. Published evidence shows that improvements in tear film parameters accumulate progressively across sessions, with measurable benefit after the first session and maximum benefit typically achieved four to six weeks after the last session of the initial course. A retrospective study found that improvements in non-invasive tear break-up time, Oxford staining scale, and OSDI scores achieved at three months post-treatment were maintained at six months, suggesting durability of the initial response over a medium-term period.

For LLLT, a typical initial course involves two to four sessions performed over two to four weeks. The 2022 Scientific Reports randomised trial used six sessions over three weeks (twice weekly) and demonstrated significant improvement measured at four weeks from treatment commencement. The RCT in the cataract surgery setting used two sessions perioperatively and showed meaningful benefit on tear film stability and discomfort symptoms.

Repeat therapy: the improvement from both IPL and LLLT is sustained but not permanent. MGD is a chronic condition and the underlying gland dysfunction does not resolve permanently after a single treatment course. Published studies with extended follow-up report that most patients require maintenance sessions at six to twelve monthly intervals to sustain the treatment benefit. The need for repeat therapy is similar to other chronic disease management strategies. Patients who have responded well to an initial course typically maintain their response with a single maintenance session every six to twelve months.

When to perform LLLT and IPL before cataract surgery

LLLT and IPL should be completed before biometry, not merely before surgery. Biometry should be performed on an optimised ocular surface after treatment. The typical timeline from commencing IPL to surgery is eight to twelve weeks, accommodating three sessions at two-week intervals and a four-week observation period before repeat biometry and surgical planning.

The most important principle is that biometry should be performed after the ocular surface has been optimised, not before treatment. Performing biometry before treating dry eye captures the inaccurate measurements produced by the unstable tear film. Performing biometry after treatment captures the improved and more stable surface.

The recommended sequence is:

Step 1: Dry eye assessment at the pre-operative consultation. This includes tear break-up time, fluorescein and lissamine green staining, meibomian gland assessment, and OSDI questionnaire. Any patient with evidence of significant dry eye or MGD is a candidate for pre-operative treatment.

Step 2: Initiate treatment. For patients with significant dry eye before planned cataract surgery, an initial IPL and meibomian gland expression course of three sessions at two-week intervals is the typical approach, followed by LLLT sessions concurrently or in sequence. Simple supplementary measures including preservative-free lubricating drops, omega-3 supplementation, and warm compresses should also be initiated.

Step 3: Re-perform biometry four to six weeks after completing the treatment course. This allows time for the meibomian gland response to take full effect and for the tear film to stabilise. The repeat biometry is performed on the optimised ocular surface and produces more accurate and reproducible measurements. Significant differences between pre-treatment and post-treatment biometry in the same patient confirm that the initial measurements were unreliable.

Step 4: Surgery is planned using the post-treatment biometry. If pre-treatment and post-treatment measurements agree within clinically acceptable limits (typically within 0.25 to 0.50 D on keratometry), the initial measurements can be used with confidence. If they differ significantly, the post-treatment measurements are more reliable.

The timeline from treatment commencement to surgery is typically eight to twelve weeks, which accommodates three IPL sessions at two-week intervals and a four-week observation period before repeat biometry.

For patients with mild dry eye where treatment is initiated with lubricating drops and simple measures rather than IPL or LLLT, a minimum of four weeks of ocular surface optimisation before biometry is recommended based on the evidence from the artificial tear study showing keratometric stabilisation at four weeks.

Recommendations for optometrists and GPs

Optometrists typically see patients first and are in the best position to identify dry eye before cataract surgery referral. Patients with known dry eye, blepharitis, rosacea, long-term preserved glaucoma drops, a history of LASIK or PRK, diabetes, or inconsistent keratometry readings should have dry eye specifically documented in the cataract referral so that pre-operative surface optimisation can be planned.

Optometrists play the most important role in identifying dry eye before cataract surgery referral because they typically see patients first and perform the initial assessment.

The following patients presenting for cataract assessment should have dry eye specifically identified and documented in the referral:

Patients with known dry eye disease, blepharitis, or rosacea.

Patients on long-term preserved glaucoma drops, for whom the impact on biometry and IOL accuracy is detailed in our guide to dry eye from glaucoma drops and its effect on biometry.

Patients with a history of LASIK or PRK, which causes corneal nerve transection and dry eye by the same mechanism as cataract surgery.

Patients with diabetes, where autonomic neuropathy and tear film dysfunction frequently affect the ocular surface. See our guide to dry eye in diabetic patients having cataract surgery for the full preoperative assessment framework in this group.

Patients with irregular or variable keratometry readings on autorefraction or topography that do not correlate with the patient's visual acuity. This pattern strongly suggests an unstable tear film producing variable measurements.

The single most helpful piece of information to include in a referral for a patient with suspected dry eye is whether the corneal topography or autorefraction was consistent and repeatable on the day of the assessment, or whether it showed variability suggesting an unstable ocular surface.

For full referral information and guidance for optometrists and GPs, see our referral information for optometrists page.

Arranging an assessment

If you have dry eye disease and are considering cataract surgery, or if your optometrist has identified an irregular or unstable corneal surface at your assessment, a preoperative evaluation that includes ocular surface assessment alongside biometry planning is the most important step in ensuring an accurate surgical outcome.

I consult at Northern Eye Consultants, Northpark Private Hospital, Bundoora, and at Bass Coast Eye Centre, Wonthaggi. A referral from your GP or optometrist is required.

Contact Northern Eye Consultants to arrange an appointment. For referral information for GPs and optometrists, visit the Northern Eye Consultants for-referrers page. Further information on cataract surgery Melbourne including a published five-year surgical outcomes audit is available at drmacintyre.com.

References

1. Giannaccare G, et al. Outcomes of low-level light therapy before and after cataract surgery for the prophylaxis of postoperative dry eye: a prospective randomised double-masked controlled clinical trial. Br J Ophthalmol. 2024;108(8):1172-1176. https://pubmed.ncbi.nlm.nih.gov/37890879/
2. Park Y, Kim H, Kim S, Cho KJ. Effect of low-level light therapy in patients with dry eye: a prospective, randomized, observer-masked trial. Sci Rep. 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC8897458/
3. Antwi JD, et al. Effect of low-level light therapy in individuals with dry eye disease. Ophthalmic Physiol Opt. 2024. https://onlinelibrary.wiley.com/doi/abs/10.1111/opo.13371
4. Toyos R, Desai NR, Toyos M, Dell SJ. Intense pulsed light improves signs and symptoms of dry eye disease due to meibomian gland dysfunction: A randomized controlled study. PLOS ONE. 2022. https://pubmed.ncbi.nlm.nih.gov/35737696/
5. Effectiveness and safety of intense pulsed light therapy for dry eye symptoms due to meibomian gland dysfunction: A systematic review and meta-analysis. PubMed 39611367. https://pubmed.ncbi.nlm.nih.gov/39611367/
6. Pac CP, et al. Intense Pulsed Light Therapy for Dry Eye Disease: Analyzing Temporal Changes in Tear Film Stability and Ocular Surface between IPL Sessions. Healthcare. 2024. https://pubmed.ncbi.nlm.nih.gov/38891194/
7. Randomized controlled study evaluating outcomes of IPL and LLLT for treating meibomian gland dysfunction and evaporative dry eye. PMC10276683. https://pmc.ncbi.nlm.nih.gov/articles/PMC10276683/
8. Impact of Dry Eye Disease and Lipid-Containing Artificial Tears on Keratometric Reproducibility and IOL Calculation in Cataract Patients. PMC12843478. https://pmc.ncbi.nlm.nih.gov/articles/PMC12843478/
9. Mechanisms and management of dry eye in cataract surgery patients. PubMed 26569526. https://pubmed.ncbi.nlm.nih.gov/26569526/
10. Nibandhe AS, Donthineni PR. Understanding and Optimizing Ocular Biometry for Cataract Surgery in Dry Eye Disease: A Review. Semin Ophthalmol. 2023;38(1):24-30. https://pubmed.ncbi.nlm.nih.gov/35989638/
11. Management of Dry Eye Disease Pre- and Post-Cataract Surgery: A Personalized Approach. J Pers Med. 2026. https://doi.org/10.3390/jpm16020086