Are you ready for corneal topography?

Optometric Management, Jul 2001 by Gupta, Deepak

Lower prices put this technology within your reach. Here are more reasons to consider investing.

In the old days, corneal topographers were bulky and expensive, with prices as high as $40,000. Now, the units are computerized and portable, with prices starting around $6,000. If you don't already have a corneal topographer in your practice, now may be a good time to take a look at what this technology can do for you.

In this article, I'll discuss the potential uses of corneal topography, as well as the financial benefits. First, let's review some key clinical applications - contact lenses, ocular disease and pre- and post-- surgical management.

Contact lens fitting help

You may not need a corneal topographer for routine fittings of spherical contact lenses, but this technology really pays off when you're fitting toric soft contact lenses and rigid gas permeable (RGP) lenses. The reason? A keratometer reads only the central 3 mm or so of the cornea, but topography provides information about the peripheral and midperipheral cornea. This is especially helpful because most toric soft lenses have a diameter of 14 mm or 15 mm.

If you're fitting RGPs, you can use a topographer's fitting software to simulate trial lenses on a patient and avoid having to call him back for appointment after appointment. The computer programs won't eliminate the trial lens step, but in many cases, they can help rule out a particular lens before you order it. By reducing the number of lenses you have to order, you can reduce cost and inconvenience for yourself and your patient.

Some other contact lens applications for corneal topography include:

* Orthokeratology. Corneal shaping by orthokeratology offers a viable alternative for patients who don't want to wear eyeglasses or contact lenses during the day, but who can't or don't want to undergo refractive surgery. A topographer lets you analyze changes in the corneal curvature and evaluate the effectiveness of the various contact lenses.

* Specialty lenses. Topography gives you a clear picture of the patient's entire cornea when you're fitting bitoric, postsurgical and bifocal RGPs.

* Corneal health. As we all know, despite what we tell patients, many of them overwear their contact lenses. Some even sleep in them for days at a time! By routinely performing topography on your contact lens patients, you can closely monitor changes to the cornea caused by this abuse.

Detect ocular disease

Another important use for the topographer is to detect and evaluate corneal abnormalities, such as those associated with:

* Keratoconus. This is probably one of the most common and useful applications of corneal topography. You should routinely order topography on any patient whose astigmatism shows a dramatic change from year to year or whose mires looks suspicious on keratometry or slit lamp examination.

Corneal topography will help you determine what stage of keratoconus your patient has. By performing topography on a biannual basis, you can monitor the progression of the condition. In conjunction with providing you with clinical findings, the corneal topographer can help you fit these patients in custom contact lenses or decide if they need surgery.

* Corneal transplants. Topography lets you see the entire cornea so you can monitor the healing process of post-phototherapeutic keratectomy (PTh) patients. The information that topography provides will help you decide when and if you should cut sutures or adjust running sutures. It also helps you evaluate surgically induced astigmatism and decide what to do about it.

* Epithelial dystrophy. On some patients, epithelial dystrophies show up initially as irregular astigmatism or corneal distortion. Corneal topography will help determine if Pm is needed.

Surgery management tool

Corneal topography is essential for refractive surgery patients and can be an asset for patients undergoing cataract surgery. Although topography isn't routinely needed for managing the pseudophakic patient, it can be helpful in dealing with corneal astigmatism. If the patient has significant astigmatism preoperatively, topography can help the surgeon plan the wound architecture to negate some of the astigmatism.

For patients with significant post-op astigmatism, topography can help you decide which sutures to remove. It can also help determine whether the patient will be best served with eyeglasses, contact lenses or astigmatic keratotomy.

For refractive surgery, corneal topography:

* Is mandatory for preoperative work-ups. It helps screen out poor candidates for surgery. The topographer helps identify corneal ectasia and irregular corneas as well as keratoconus; and it will show corneal warpage or distortion from contact lens wear, which may affect the manifest refraction. This information will help you determine how long a patient should be out of contact lenses before the refraction is stable.

* Helps detect postoperative problems. Using corneal topography to monitor post-refractive surgery patients is the standard of care for almost any procedure. With the topographer, you should be able to monitor central islands, depressions and irregular astigmatism. You can follow healing trends over time by comparing pre- and postoperative maps. The maps also let you know if you've achieved your targeted level of correction.