In this episode of Interventional Mindset, Preeya K. Gupta, MD, and Vance Thompson, MD, discuss why the tear film should be evaluated and treated as a refractive structure before cataract and refractive surgery.
Dr. Thompson is the founder and director of refractive surgery at Vance Thompson Vision in Sioux Falls, South Dakota, a professor of ophthalmology at the Sanford School of Medicine at the University of South Dakota, and a past president of the American Society of Cataract and Refractive Surgery (ASCRS). Dr. Gupta is a cornea, cataract, and refractive surgeon at Triangle Eye Consultants, a member of the ASCRS Refractive Surgery Clinical Committee, and a past president of the Vanguard Ophthalmology Society.
Tear film stability in cataract surgery fast facts
- Together, the tear film and anterior corneal surface provide approximately 80% of the eye's refractive power; tear film instability induces irregular astigmatism and higher-order aberrations that produce fluctuating vision even when best-corrected acuity (BCVA) is normal.1
- In a prospective study of 218 cataract surgery candidates, 55.5% met TFOS DEWS II criteria for dry eye disease, 66.5% had abnormal tear osmolarity, and approximately 80% showed meibomian gland dropout; no objective sign correlated with OSDI symptom scores.2
- Cataract surgery stresses the ocular surface through corneal nerve transection, topical drop toxicity, microscope light exposure, and increased inflammatory mediators,3 producing what is now termed surgical temporary ocular discomfort syndrome (STODS).4
- Blink rate decreases during both printed and digital reading, regardless of task duration, difficulty, or viewing distance.5
- Demodex blepharitis contributes to meibomian gland dysfunction and tear film breakdown, and lotilaner ophthalmic solution 0.25% (XDEMVY, Tarsus Pharmaceuticals) targets the mite directly.6
Treating "tear anemia" before biometry
“So to go into it with a dry eye that's about ready to get drier, I like to use this phrase that I call ‘tear anemia,’ because again the tears are the blood of the cornea.”
Dr. Thompson compares an unstable tear film to pre-operative anemia: an elective procedure should not proceed until the deficit is corrected. The practical question is whether correcting it changes the intraocular lens (IOL) a surgeon selects. A 2024 prospective trial from the University of Toronto indicates that it does.3
Yang et al. enrolled 40 eyes of 21 patients with DEWS II–confirmed dry eye scheduled for cataract surgery with a monofocal IOL. Patients used lifitegrast 5% twice daily plus preservative-free sodium hyaluronate tears four times daily for 6 weeks; biometry was then repeated on the IOLMaster 700 using the Barrett Universal II formula.3
After treatment:3
- Mean OSDI improved from 26.35 to 20.97 (P = .03)
- Eyes with corneal staining decreased from 62.5% to 30.0% (P = .01)
- Calculated IOL power changed by ≥0.5D in 50% of eyes
- Eyes within 0.25D of the predicted refraction rose from 67.5% with baseline biometry to 87.5% with post-treatment biometry (P = .05)
- Mean tear osmolarity did not change (318.15 vs. 318.08 mOsm/L)
How tear film instability can impact surgical timing
The osmolarity result bears on surgical timing. In a previous Interventional Mindset episode, Dr. Thompson described delaying premium IOL and LASIK procedures until osmolarity falls below 300mOsm/L, noting that current therapies often improve the surface within 2 to 4 weeks.7
In Yang's cohort, staining resolved in many eyes while osmolarity remained elevated, which supports remeasuring osmolarity before final biometry rather than inferring improvement from a clear cornea.3
Treatment intensity matters as well. In a randomized trial of 131 cataract patients, 2 weeks of preservative-free artificial tears alone produced no significant change in keratometry variability or refractive prediction error, and the authors concluded that therapy beyond artificial tears may be required to stabilize the tear film before surgery.8
Dr. Thompson's approach reflects this. For the patient he describes in the video—elevated osmolarity, no staining, and Demodex blepharitis—he started lotilaner, counseled her on her blink rate, planned to consider punctal occlusion, and postponed surgery by 1 to 2 months.
Screening patients who don't report symptoms
Because signs and symptoms diverge in cataract candidates,2 questionnaires alone miss patients with an unstable surface. Dr. Gupta uses biometry acquisition itself as a screening step.
“I always tell them … put a little sticky note on the biometry … if it wasn't a really good quick test—if they struggled or had to blink 20 times—that's information for me.”
She also asks every cataract patient whether their vision fluctuates, which helps separate cataract-related blur from surface-related blur before committing to a surgical plan.
Setting expectations before surgery
Dr. Thompson asks patients how aggressively they want to treat the surface pre-operatively. If the eye is no longer red or staining, he may proceed and intensify treatment after surgery, but only after explaining that the dryness predated the procedure.
“[T]hose sorts of conversations help keep doctors out of trouble because patients are going to say ‘this surgery caused my dry eye,’ if they don't understand they were dealing with dryness pre-operatively also.”
Both surgeons report that many "20/20 unhappy" second opinions after premium IOL or corneal refractive surgery resolve with tear film treatment alone. Dr. Thompson has documented one such case: a 72-year-old man requesting trifocal explantation had tear osmolarity of 320 and 322mOsm/L. After dry eye treatment and bilateral YAG capsulotomy, osmolarity fell to 302 and 300mOsm/L, and he refracted to a crisp 20/20 in each eye without exchanging either lens.9
In closing
Premium IOL outcomes depend on the tear film twice: at biometry and again at post-operative image quality. Prospective data show that anti-inflammatory treatment can shift IOL power selection by half a diopter or more in half of eyes with dry eye,3 while artificial tears alone may not change biometric measurements.8
Objective screening of every candidate, treatment of root causes such as Demodex, repeat osmolarity testing before final measurements, and documentation of preexisting disease allow surgeons to hit the refractive target and manage STODS without being blamed for it.
For more information on pre-operative osmolarity testing, check out: The Importance of Osmolarity Testing in Cataract Care.
