You Can Diagnose Dry Eye Preoperatively

This surgeon avoids postop dry eye issues

KEVIN L. WALTZ, OD, MD, AND BRENDA J. WAHL, OD

Optimizing the ocular surface for best visual outcomes with refractive surgery and cataract surgery is a universal goal of eye surgeons. The question has become not if, but how, do we best diagnose and treat the ocular surface peri-operatively There are endless opinions and suggestions. This article will present yet another, with a twist. This time, there are easily obtained objective images to assist the busy surgeon in the evaluation and follow-up process.

We have been offering refractive surgery and refractive cataract surgery in our practice since the mid 1990s. Treating the ocular surface has become an integral part of our practice as we have grown more sophisticated in our understanding of what it takes to make our patients consistently happy. We began to notice that our topographies were more consistent and more accurate when done prior to instilling any drops. We decided to perform topography on all of our patients prior to instilling drops. This helped our outcomes. We then noticed that we obtained better-quality topographies on some patients with a wetting drop or two. Lately, we have realized that patients who require wetting drops to obtain a good topography are giving us useful clues about the degree of their ocular surface problems.

Diagnosing Dry Eye Preoperatively

We are now evaluating all of our preoperative topos for evidence of dry eye. We find clear evidence of dry eye in about 10% of our cases preoperatively. The evidence is in the form of an irregular ocular surface with increased higher-order aberrations (HOAs) from the cornea. In these cases, we initiate therapy delay the surgery date, and re-evaluate prior to surgery to confirm the dry eye is better. This process regularly leads to changes in the surgical plan and an improved preoperative discussion. Sometimes, it leads to canceling the surgery because the patient is so improved on the dry eye treatment they no longer feel the need to proceed with surgery.

In every case where we identity a poor-quality ocular surface, the patient is made aware that it is a serious problem. It is serious enough to delay their surgery. They are made aware of the problem preoperatively. This, of course, means the surgery did not cause their dry eye. How many times does the surgeon do perfect surgery with a great outcome only to have to put the patient on wetting drops postop for improved comfort or improved vision? The patient often interprets this sequence to mean the surgery caused their dry eye. Even in the kindest patient, this is not a good impression to leave. At the very least, identifying and treating dry eye preoperatively leaves the patient with the impression that the dry eye is not related to the surgery and the surgeon is acting in the patient's best interest.

A Scenario You Don't Want

Imagine this scenario. A patient is evaluated for Prelex or refractive lens exchange. The patient has significant dry eye that is asymptomatic, but is causing identifiable HOAs on the topography.

The technician has trouble obtaining a reliable topography due to the dry eye. The technician then applies wetting drops to improve the quality of the image. The first images are thrown out by the technician as poor-quality images. The surgeon performs the surgery without difficulty but the patient reports more than the usual amount of discomfort and glare postop.

The patient is then evaluated for dry eye with the usual means — Schirmer, dye, SLE, history — and a diagnosis of dry eye is made. Treatment to optimize the ocular surface is begun. The patient gets better. The patient must now stay on artificial tears to keep the ocular surface smooth. Did the surgery cause the patients dry eye? Is the dry eye a complication of the surgery? Is dry eye an expected outcome of intraocular surgery? Was the patient informed of this possibility pre-op? These are all questions a reasonable patient will ask. In our experience, these are not difficult questions to deal with, but they are potentially unnecessary questions.

The Scenario You Do Want

Imagine this alternative scenario. A patient is evaluated for refractive cataract surgery. The patient has a routine topography done preoperatively. The technician identifies a poor-quality scan. Wetting drops are applied. The scan is repeated. Both sets of scans are presented to the doctor. A diagnosis of poor ocular surface quality is made on the basis of the scan, presumably secondary to dry eye. Preoperatively, dry eye therapy is begun. The patient returns in one month with a much-improved ocular surface. The surgery goes as planned and the patient sees well with postoperative dry eye treatment. There is no question the surgery did not cause the dry eye. It was diagnosed and treated preoperatively. The patient has a smooth postoperative course and no nagging questions.

Early Diagnosis in Practice

Let's look at some real cases. Patient A presented for Prelex or refractive lens exchange. As part of the preoperative evaluation, topography was obtained.

The scan for the right eye shows significant irregularity of the ocular surface in the upper left-hand corner of the image sets (Figure 1). The convolved image in the upper right hand corner shows poor-image quality for this cornea. The isolated HOAs in the lower right-hand corner show an unusual amount of trefoil. The modulation transfer function (MTF) in the lower left-hand image is shows poor image quality.

Figure 1. An Atlas 9000 image from the initial preoperative exam. The upper left image is the usual axial image with additional customizable data. The upper right image is a convolved image using the topography as a lens to view the Snellen chart. The lower right image is a bar graph of the individual higher order aberrations. The lower left image is the MTF for the cornea, not the entire eye. Note the data analysis can be done at different pupil sizes. All images in this article were analyzed with a 6-mm pupil.

This patient was counseled about the poor-quality ocular surface and the potential adverse effects on the surgery. The patient was placed on artificial tears and re-evaluated approximately one month later with topography (Figure 2). The ocular surface has improved markedly in every part of the scan. The surface is more regular. The convolved image is much sharper. There are many fewer HOAs. In addition, the MTF is improved.

Figure 2. This is the same set of images on the same patient as Figure 1. It is from the follow-up preoperative exam. It shows improvement in all parameters after one month of dry eye treatment.

This eye had successful refractive cataract surgery. Of special note, the axis of the 1 D of astigmatism rotated approximately 25 degrees with dry eye therapy. If an astigmatic incision was placed at the time of the surgery, it would appear to have been ineffective. If a toric lens were placed based on topo and dry eye treatment begun postoperatively, the axis of the toric lens would have been significantly misplaced. It is likely that treating dry eye preoperatively will lead to better outcomes with toric IOLs by improving the axis and power determination.

Patient B presents for refractive cataract surgery. A routine topography is taken as part of the preoperative evaluation. The scan shows a number of problems (Figure 3). There is poor surface quality. The conformed image shows poor image quality. There are significant HOAs. The MTF is of a poor quality.

Figure 3. This image is a similar configuration as seen in Figure 1 and 2 from a different patient. It is from the initial preoperative exam. This person has poor ocular surface quality, poor image quality for the cornea, increased HOAs, and decreased MTF.

Dry eye treatment is begun and topography is repeated about a month later. There is dramatic improvement in the scan in all aspects (Figure 4) and dramatic rotation in the astigmatism axis of this eye with dry eye treatment. Surgical planning is improved with more accurate astigmatism vector analysis. The surgery goes well and there are no issues postop. The patient maintains artificial tear treatment postop.

Figure 4. This image is from the follow-up preoperative exam. It demonstrates improvement in all parameters with artificial tears.

Technology Makes A Difference

It is reasonable to ask why we have not noticed this trend prior to 2009. While we have used several topography systems over the years, none of them have provided the image detail and the software flexibility of the one we purchased in the spring of this year. The Zeiss Atlas 9000 has made a difference in how we evaluate and treat our patients. The data acquisition and manipulation allows us to see characteristics of the topography image we have not seen previously. The convolved image allows us to educate our patient in ways we could not previously.

When we educate the patient about why their surgery is being delayed, they are very appreciative as well as compliant. They will almost uniformly report subjective improvement in vision consistent with their objective improvement in ocular surface quality. That's not surprising, as ocular surface quality is a well-recognized determinate of successful intraocular surgery.

Poor-quality ocular surface is most often diagnosed post-operatively. We propose a method to evaluate the ocular surface preoperatively that is readily available. Careful attention to preoperative topography has significantly improved our patient education process and our surgical outcomes. OM

Kevin L. Waltz, OD, MD, and Brenda Wahl, OD, are in practice at Eye Surgeons of Indiana in Indianapolis. Dr. Waltz can be reached via-e-mail at klwaltz@aol.com. Neither Dr. Waltz nor Dr. Wahl has any financial interest to report.