Detection of a Tear Film Dysfunction through Keratometry Measurements

Advanced technology IOLs require equally advanced OSD workup

By Ivan Mac, MD, MBA

My practice philosophy is predicated on delivering outcomes that match the high expectations of patients. Toward that end, we invested in the latest diagnostic equipment and committed to being on the cutting edge, continuing to adopt new technologies that allow for better patient outcomes. 

Despite this investment in new technologies, we have come to realize the critical role that the ocular surface plays in the predictability and accuracy of our pre-operative measurements and to its overall effect in terms of the post-operative outcome. As our knowledge of ocular surface disease (OSD) evolved, so did our protocol for managing dry eye prior to surgery. Where once we just used to put all cataract patients on artificial tears, we now have a much more comprehensive treatment algorithm that considers the prevalence of meibomian gland dysfunction, which occurs in up to 86% of all cases of OSD.¹ If there is significant OSD, aggressive lid hygiene regimens, such as a course of intense-pulse light therapy or thermal lid pulsation, are paired with a short course of lower-potency steroids like Flarex (fluorometholone acetate ophthalmic suspension; Eyevance Pharmaceuticals) or loteprednol. At-home lid hygiene therapy (Avenova; NovaBay) is initiated along with artificial tears. We typically see patients back 3 weeks after treatment and if the ocular surface has improved significantly, we go ahead and proceed with the cataract surgery measurements. This regiment allows for rapid improvement in the ocular surface for most of our patients and if not, we add immunomodulators like lifitegrast or cyclosporine regimens and wait a few weeks longer before surgery.

Each evolution in our approach allowed us to achieve increasingly improved visual outcomes for all patients, regardless of them opting for a premium lens or not.

Accurate Measurements Require a Healthy Surface
Along with surgical skill, a healthy tear film is one of the most important factors for achieving excellent vision following cataract surgery. 

The tear film is the first refractive surface of the eye, so when the tear film is unstable, the quality of corneal reflections is affected. Tear film instability adversely impacts the accuracy of keratometry measurements,^2,3 leading to changes in the magnitude and axis of astigmatism. In turn, the variable K-readings can affect the accuracy of IOL calculations and result in suboptimal refractive outcomes.^2-6 Plus, dry eye symptoms often worsen after surgery,⁷ and the procedure itself can induce or exacerbate dry eye diease (DED).^8,9 This is why our golden rule is that no patient goes to cataract surgery with OSD. Optimizing the ocular surface allows for a more precise outcome and a smoother postoperative course.

Beyond the accuracy of astigmatism measurements, DED can cause higher-order aberrations, the most clinically significant of which are spherical aberration and coma. With treatment, the aberrations often improve. Clinically, this means not only a better outcome, but also allows more patients who otherwise would not qualify for a premium IOL to become candidates.

We are very particular about getting good measurements prior to cataract surgery, and we typically compare and contrast multiple K-readings from 3 different devices. We look for stability between measurements and are alerted to possible OSD if this is not the case. If there is a good correlation in terms of the magnitude and axis of astigmatism, then we feel comfortable that the patient has an accurate measurement, and we can proceed with surgery. However, if there are any signs of variation between the axis and magnitude of the K-readings and they don’t match up, that usually indicates that the ocular surface is not optimized.

Osmolarity is a Pivotal Marker
Evidence has confirmed the central role of increased tear osmolarity in the pathophysiology of DED, as described by the Dry Eye Workshop.¹⁰ Studies support the use of tear osmolarity as a tool to diagnose, grade severity, and track therapeutic response in DED.^11-18

We have instituted a protocol where if patients have osmolarity scores measured by TearLab Osmolarity testing above 315 to 320 mOsms/L, they do not proceed to the cataract workup. Those patients see me for further ocular surface examination. The cataract workup can take 45 minutes; our technicians’ time—and our patients’ time—is valuable and should not be wasted. We aim to avoid proceeding to the workup stage in patients who need ocular surface optimization.

Conversation
Surgeons may worry about telling patients there will be a delay in their progression to cataract surgery. I explain to them that although they have visually significant cataracts that are ready to come out, there is an issue. I inform them that the surface of their eye is too dry for cataract surgery. I use this analogy: “If the windshield of the car is not clean, you’re never going to really see very well, so if I do cataract surgery and if I rush you through it, if I don’t take care of the dry eye preoperatively, the outcome will be one that neither of us is proud of.”

In my experience, this sentence engenders patients’ trust, they are often willing to do whatever it takes because they know that I am looking out for their best interest to deliver a superior outcome. It is also important that patients understand that dry eye is a disease, just like high blood pressure or high cholesterol. We don’t wait for someone to have a heart attack before we initiate treatment, and after they’ve had a heart attack, we don’t stop treatment. Dry eye is the same; a lifelong disorder that we can manage, but not eliminate.

More Advanced Technology Candidates
As mentioned previously, by treating the ocular surface, we qualify more patients for premium technology. Some surgeons worry that doing any self-pay procedures prior to cataract surgery discourages patients from paying for advanced IOLs. I find the reality is the opposite.

After their surface has been optimized, and when patients are told they are a good candidate for a refractive lens, further excitement is generated. Their willingness to invest in advanced IOL technologies and OSD treatments increases because they realize the impact that good vision has on their quality of life. It is my experience that patients who are already invested in the process often opt for the most advanced technologies available to them, thereby increasing the financial return for my practice. We continually reinforce the idea that OSD is a life-long process, that requires life-long treatments to preserve the health of their eyes and achieve their best vision. Devoting time to optimizing the ocular surface is a win-win for both the patients and our practice. 

Ivan Mac, MD, MBA is the founder of Metrolina Eye Associates, North and South Carolina
Contact: [email protected]
Financial disclosure: Consultant to Alcon, Tarsus Inc, Eyevance/Santeen Pharmaceuticals, Sun Pharmaceuticals, Ellex Inc, NovaBay, Visionary Ventures Group, TearLab

Reference

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