Many years ago, cataract and refractive surgeon Marguerite McDonald, MD, shared this pearl about presurgical evaluations of the ocular surface: If you diagnose dry eye disease (DED) preoperatively, it is the patient’s problem; if you make the diagnosis post-op, it becomes your problem.¹ I have found it wise to take Dr. McDonald’s advice to heart and look for DED in every surgical candidate during the pre-op work-up.

PREVENTING A POST-OP SURPRISE

Pre-op measurements are susceptible to DED-driven inaccuracy.² Fluorescein staining of the cornea and uncovering superficial punctate keratitis (SPK) can lead to more accurate measurements and can prevent a post-op refractive surprise. For example, John Hovanesian, MD, and his group showed that using lifitegrast 5% (Xiidra, Bausch + Lomb) in cataract patients to treat pre-op SPK led to more accurate intraocular lens (IOL) power calculations.³ As long as someone takes the time to stain the tear film, you can potentially head off DED-driven refractive unhappiness.

But what about those patients who have what looks like a benign slit-lamp exam with a presumably normal tear film? We have all seen post-op patients with an unexpected outcome who had a work-up that seemed entirely benign. What can we do to avoid the frustrations both doctor and patient have when this happens? This is where measuring tear osmolarity (TO) in every surgical candidate comes in.

Hyperosmolarity (>310 mOsm/L) and inter-eye asymmetry (> 8 mOsm/L) are both diagnostic for the presence of DED of some form. Alice Epitropolous, MD, and her coauthors showed that elevated TO leads to increased variance in keratometry readings of all types.⁴ In the absence of traditional DED signs such as corneal staining, TO can be the only objective diagnostic finding, especially in asymptomatic patients.

Why is this important? Kursite, et al found patients with a refractive miss of >1.0 diopters were far more likely to have elevated TO.⁵

ADDING TEAR OSMOLARITY MEASUREMENT TO THE PRE-OP WORKFLOW

Adding TO measurement to your pre-op evaluation is surprisingly straightforward and adds very little time to your process. The only FDA-approved instrument cleared to measure TO is the TearLab family of instruments now owned by Bausch + Lomb. The new portable ScoutPro is a handheld instrument that can be carried from room to room. In our office, each technician working up patients in preparation for seeing one of our doctors carries it in their pocket.

After inserting the “lab on a chip” into the handpiece of the instrument, it takes 20 seconds or so per eye to do the test. That’s less than 1 minute to obtain results for both eyes. Osmolarity for each eye registers on the small screen of the handpiece, where the data from the 3 most recent patients is stored.

Pricing for both the handheld units and the disposable chips is volume based. Reimbursement is nearly universal and more than covers the cost of the chip. In 2026, Medicare has been paying roughly $28 per eye.

Asymptomatic DED patients can slip through the pre-op process if efforts to diagnose DED are not part of the standard work-up. Tests like fluorescein staining and tear break-up time will diagnose the majority of those patients who may have their post-op satisfaction derailed by hidden DED. Testing for elevated tear osmolarity helps make sure you diagnose the rest.

References:

1 Getz L. Dry eye: How pre-op treatment leads to post-op success. Ophthalmology Management. 2021;25(2).

2 Yang F, Yang L, Ning X, Liu J, Wang J. Effect of dry eye on the reliability of keratometry for cataract surgery planning. J Fr Ophtalmol. 2024;47(2):103999.

3 Hovanesian J, Epitropoulos A, Donnenfeld ED, Holladay JT. The effect of lifitegrast on refractive accuracy and symptoms in dry eye patients undergoing cataract surgery. Clin Ophthalmol. 2020;14:2709-2716.

4 Epitropoulos AT, Matossian C, Berdy GJ, Malhotra RP, Potvin R. Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning. J Cataract Refract Surg. 2015;41(8):1672-1677.

5 Kursite A, Laganovska G. Effect of tear osmolarity on postoperative refractive error after cataract surgery. J Ophthalmol (Ukraine). 2023;(2):11-15.

Darrell E. White, MD Darrell E. White, MD, is the founder of SkyVision Centers in Ohio. Over the past decade, his focus on the treatment of dry eye has made SkyVision a “Dry Eye Center of Excellence.”

This content sponsored by Bausch + Lomb