Evaluate Corneal Health
Evaluate Corneal Health
Non-contact specular microscope assists you in assessing corneal health.
ROBERT RIVERA, M.D.
Because corneal thickness and the health of the corneal endothelial cell layer dictate our course of action when dealing with contact lens patients and refractive surgery candidates, among other patients, it's imperative we have a device that enables us to accurately observe and document these characteristics.
I've discovered that the EM-3000 non-contact specular microscope, from Tomey, not only allows me to accomplish this task, but does so efficiently.
How it works
As soon as you touch the center of three oval reflections (similar to a bullseye) that appear on the device's large color touch screen, it's ready to accept a patient. In fact, you can control all the unit's operations via the touch screen — a real time saver.
Then, you place the patient's head on the EM-3000's chin rest. Because the device doesn't require you to place the heads of post-cataract and post-implantable contact lens (ICL) patients at a precise angle to capture images of the endothelial cells, it's particularly useful when examining these patients.
Now, instruct the patient to focus on a fixation dot of your choosing. The device offers a central fixation point for central cornea image acquisition and six peripheral points. The six peripheral points facilitate your ability to screen for and/or assess specific disease and irregularities, as peripheral images capture more endothelial cells than a central image. For instance, some corneal conditions, such as keratoconus or old herpetic scars, may display differing endothelial cell densities at different locations in the cell layer, while other conditions, such as Fuch's corneal dystrophy, show a diffusely decreased population of endothelial cells.
EM-3000 Non-Contact Specular Microscope
HEIGHT: 18 inches
WIDTH: 13 inches
LENGTH: 20 inches
WEIGHT: 38 lbs
After the device locks on to the cornea's apex, it activates a brief scanning L.E.D. exposure light to acquire images fast. (Photo acquisition takes an average of three seconds.) I've discovered that patients really appreciate this feature because it doesn't require them to focus on the fixation dot for a long period of time — an uncomfortable activity.
Depending on the shape of the cornea, the EM-3000 takes up to 15 photos in a range of 3.5mm × 0.54mm across the cornea's back (the endothelium) to reduce photo errors. The device measures corneal thickness at the same time. When the EM-3000 takes 15 pictures, it's capturing a photo of an area on the cornea that is 15 pictures wide. In other words, it takes photo no.1, then moves slightly to the right and takes the remaining shots. Therefore, acquiring 15 shots of a cone-shaped cornea is difficult because of the angle of the corneal slope. If the patient has a flat cornea, however, acquiring all 15 shots is easy.
The unit then uses its built-in computer to automatically assess the quality of the captured images before selecting what it deems to be the best image of the endothelial cells.
The EM-3000's ability to colorize the difference in the size and shapes of the cells along with two very easy-to-understand histograms helps you get a true picture of the health of the endothelial cell layer.
After the EM-3000 selects the image, however, you still have the option of scanning through the 14 other photos via the color touch screen, just in case some form of dystrophy, such as guttata, doesn't appear on the device's selected image. This allows you to correlate the test results with any clinical findings you might observe upon slit lamp exam to confirm the diagnosis.
You can then send the images and resulting data to a photo printer, your electronic medical record system or both. The EM-3000 comes with a USB-D connector for Pict Bridge compatible printer hook-up; a USB-H connector for barcode reader or electromagnetic card reader to enter patient ID data. Also, the device comes with a LAN connector so you can inspect result files assigned a patient ID, and save them on your personal computer after installing the device's "Data Transfer" software.
I've found that the ability to send images to one or both of these systems is extremely beneficial because it enables me to literally show the patient his anomaly, facilitating his understanding of the finding and therefore the importance of complying with my recommendations.
The EM-3000 has allowed me to help several categories of patients. For instance, I use it to screen all patients who are considering an implantable contact lens or LASIK surgery to ensure they have a normal endothelial cell density and corneal thickness. If a patient displays any amount of corneal dystrophy, I show him the device's findings and explain why he shouldn't undergo LASIK.
Most recently, the specular microscope has revealed that some contact lens wearers have a great deal of variance in the shape and sizes of their endothelial cells — most likely as a result of older (PMMA) lens designs. To prevent these patients' endothelial polymegathism from getting any worse, we, of course, recommend they switch to a higher DK lens. In fact, we recommend all contact lens wearers have this easy and straight-forward evaluation of their corneal endothelium.
The ideal diagnostic device is easy to use (i.e. a time saver), affords reliable data that can assist us in diagnosing or assessing a current condition, and provides a return on our investment. I've discovered that the Tomey EM-3000 meets all these criteria. OM
DR. RIVERA IS A PARTNER IN THE BARNET DULANEY PERKINS EYE CENTER IN PHOENIX, ARIZ., WHERE HE SPECIALIZES IN INTRAOCULAR LENS AND CORNEAL REFRACTIVE SURGERY. E-MAIL HIM AT RPRIVERAMD@AOL.COM.
Optometric Management, Issue: September 2008