Article Date: 4/1/2010

Elevate Your Practice With Topography

Elevate Your Practice With Topography

Here's a look at how corneal topography can increase patient satisfaction and practice revenue.

DIANNE ANDERSON O.D., F.A.A.O., Naperville, Ill.

When you're lost or unsure of how to reach a destination, you seek Rand McNally or Garmin to guide you. When you, as the O.D., are unsure about a specific corneal diagnosis or how to treat it, you should seek a corneal topographer, or map of the cornea, to guide you.

Here, I explain how topographers' many features can increase patient care and satisfaction, and what is involved with practice integration.

A projection of benefits

Corneal topography offers three main features that can benefit your practice:

It illustrates higher order aberrations. Most topographers measure wavefront data. This data reveals the higher order aberrations of the cornea (corneal wavefront) or the entire eye, including the lens and accommodation (optical wavefront).

For example, if a patient presents complaining of blurred distance vision that occurs especially at night, you can use the topographer to determine whether you can correct these symptoms with spectacles (defocus and astigmatism) or specialty contact lenses (coma and trefoil). Also, certain higher order aberrations are associated with specific corneal conditions. Spherical aberration is associated with LASIK and corneal reshaping, coma is associated with keratoconus, and trefoil is associated with pellucid marginal degeneration. Topographers that have wavefront capabilities illustrate these higher order aberrations in several displays: Zernicke tables, image simulation, point spread function or modulation transfer function. (See figures 1 and 2.)

Figure 1: The Zernicke table on this topographer displays a high amount of vertical coma as characteristic of keratoconus.

Figure 2: The Zernicke table shows a high amount of horizontal trefoil in pellucid marginal degeneration.

The ability to define and illustrate these higher order aberrations with your topographer facilitates your ability to decide the type of vision correction or treatment with which the patient will likely find success. Understanding and applying this type of cutting edge technology results in high levels of patient satisfaction, which can lead to numerous referrals and an increase in your bottom line.

Many offer pathology detection software. This software analyzes corneal topographic indices and identifies those that fall out of the normal range. Currently, software is available that analyzes shape factor, provides corneal irregularity measurement and toric keratometric mean and identifies these values as normal (green), suspect (yellow) or abnormal (red). Other software includes an additional nine indices, such as mean curvature, I-S value (average dioptric value of the inferior corneal curvature as compared with the superior curvature) and convexity.

Some elevation systems include keratoconus screening displays that graph corneal thickness and rate the degree of keratoconus based on thickness (or pachymetry) deviations above and below normal.

Because these types of software take the guesswork out of searching for the appropriate indices to evaluate in suspicious cases, they facilitate your ability to accurately detect and appropriately manage a wide variety of corneal disorders. The result: an increase in patient satisfaction, which, again, leads to a stream of new patients and revenue.

Several offer contact lens designing programs. These programs are extremely helpful in determining the best type of RGP lens to fit on a given cornea. They include simulated NaFl patterns, enabling you to visualize the tear film clearance beneath an RGP lens and modify the parameters to optimize the fit. Although these simulated patterns don't take into consideration lens movement due to lid tension and/or a decentered corneal apex, they do save you time in designing custom RGP lenses or choosing the best diagnostic lens for an irregular cornea.

These programs are ideal for advancing your contact lens fitting skills to the point of attracting several hard-to-fit patients — a group I've personally found to be extremely loyal and lucrative. In fact, most of these patients with whom I've worked are willing to pay the out-of-pocket fees associated with high-level contact lens evaluations and specialty contact lenses because they're so grateful for the ability to wear lenses after being told for years that it just wasn't possible. (Note: Corneal topography associated with elective procedures, such as toric or multifocal contact lens fitting, overnight corneal reshaping or refractive surgery is not covered by medical insurance, nor is the procedure itself. Therefore, topography generates income in the form of high-level contact lens fitting fees in addition to the fee associated with the procedure itself.)

Something else to keep in mind: As of Jan. 1, 2007, corneal topography has been identified by CPT code 92025 as “Computerized corneal topography, unilateral or bilateral, with interpretation and report.” Commonly covered diagnoses include irregular astigmatism (367.22), keratoconus, stable (371.61) and complication of corneal graft (996.51). (See “Corneal Codes,” below.) (Corneal topography is not bundled by Medicare with either eye exams or other tests.) Medicare will consider claims prior to cataract surgery if a diagnosis, such as anterior basement membrane dystrophy, in addition to the cataract, supports medical necessity. (See figure 3.) More often than not, testing with corneal topography prior to cataract surgery is associated with planning for concurrent limbal relaxing incisions, toric or multifocal intraocular lens measurements. Thus, it's not covered. Note that you may find additional indications and reimbursement rates when checking your local coverage determination (LCD) policy. (See “Selecting Your Topographer,” below.)

Figure 3: This patient has anterior basement membrane dystrophy, which is illustrated by the uneven mires (right) and corresponding asymmetric axial curvature topography presentation (left).

Corneal Codes

367.22…Irregular Astigmatism
371.50…Corneal Dystrophy, Unspecified
371.52…Other Anterior Corneal Dystrophies
371.61…Keratoconus, Stable
371.62…Keratoconus, Acute Hydrops
371.20…Corneal Edema, Unspecified
371.24…Corneal Edema Secondary to Contact Lens Wear
371.82…Disorder Secondary to Contact Lens Wear (not edema)
996.51…Complications of Corneal Graft

92015…Refraction, Refractive Visit
92070…Contact Lens Fit for Treatment of Disease/Lenses Supplied
92310…Contact Lens Design, Fit and Follow-up (Non-Aphakic)
92325…Contact Lens Modification/Supervision of Adaptation
92326…Replacement of Contact Lens
92025…Corneal Topography

V2510…GP Spherical
V2511…GP Toric
V2512…GP Multifocal
V2513…GP Extended Wear
V2520…Soft Spherical
V2521…Soft Toric
V2522…Soft Multifocal
V2523…Soft Extended Wear
V2530…Scleral Lens
V2599…Other (such as corneal reshaping lens)

Selecting Your Topographer

Two main types of topographers are currently available: Placido-disc systems and elevation systems.

Placido-disc systems are curvature-based, and thus, directly measure the curvature of the anterior corneal surface. These devices do so by projecting a series of concentric light rings on the cornea, capturing an image of the reflected rings and analyzing the thousands of data points along the rings. By measuring the distances between the rings and their relationships with each other, these systems can reconstruct the corneal surface with a high degree of precision and identify even micro-irregularities, such as tear layer insufficiency and anterior basement membrane dystrophy.

Placido-disc topographers are classified into two categories: small cone and large cone. Small cone Placido-disc topographers have a shorter working distance, project a greater number of rings onto the cornea than large-cone Placido-disc topographers and require a bit more skill when acquiring images on deep-set eyes. Large cone Placido-disc topographers use a longer working distance and project fewer rings onto the cornea than the small cone Placido-disc topographers, allowing for easier acquisition of images on deep-set eyes.

A Placido-disc system is ideal for toric lens fitting, multifocal lens fitting, evaluating keratoconus, corneal reshaping and for achieving a corneal disorder diagnosis. For toric lens fitting, the device enables you to rule out irregular astigmatism and pinpoint true cylinder axis. For multifocal lens fitting, the Placido-disc system allows you to accurately measure Horizontal Visible Iris Diameter (HVID), pupil diameter and palpebral fissures width for precise contact lens parameters. To evaluate the cornea for keratoconus, you can use the instrument to measure curvature out to 10mm for a true picture of the entire cornea. For corneal reshaping, the instrument enables you to use a baseline curvature map for initial qualification and comparison to subsequent corneal shape changes as a result of lens wear. Finally, these systems allow you to diagnose corneal disorders, such as dry eye, epithelial basement membrane dystrophy, Salzmann's nodular degeneration and Terrien's marginal degeneration.

Elevation systems use light rays to scan the entire cornea. These light rays directly measure the elevation of both the anterior and posterior surfaces, and, therefore, generate corneal thickness/pachymetry data. These systems derive corneal curvature from the elevation data via sophisticated algorithms. This technology includes slit scanning and anterior segment optical coherence tomography (AS-OCT). Slit scanning and AS-OCT devices display the elevation of the front and back surfaces of the cornea as anterior and posterior elevation maps.

Because elevation topographers offer pachymetry and posterior curvature and elevation data, they are ideal for pre- and post-surgical evaluations for LASIK or photorefractive keratectomy, collagen crosslinking and penetrating keratoplasty.

Topographer Models

Small-Cone Placido Disc Models:
Medmont E300 (Medmont)
Scout and Keratron (EyeQuip)
Magellan Mapper (Nidek)

Large-Cone Placido Disc Models:
ATLAS 9000 (Carl Zeiss Meditec)
ReSeeVit (Veatch Ophthalmic Instruments)
CA-200 (Topcon Medical Systems)

Slit Scanning Devices:
Orbscan (Bausch + Lomb)
Pentacam (Oculus)
Galilei (Zeimer Ophthalmic Systems)

Anterior Segment OCT Systems:
Visante omni (Carl Zeiss Meditec)
RTVue (Optovue)
SL-OCT (Heidelberg)
Spectral OCT-SLO (OPKO Health)

Practice integration

To integrate topography data with existing ancillary testing or link it with your Electronic Medical Records (EMR) software, consult your topographer vendor. I've found that most vendors offer network packages, including software for multiple review stations in your office. These packages allow you to integrate other ancillary testing, such as visual fields testing, retinal photography and anterior segment photography into one file for each patient. Many of these packages are vendor specific, meaning they require that you purchase each instrument from the same vendor. In my experience, purchasing multiple pieces of equipment from a single vendor can have cost and service advantages. For example, you'll likely receive a bulk discount on the initial purchase and service agreement as well as multiple training sessions and discounts on future system upgrades.

Integrating topography, as well as other ancillary testing, into EMR systems is dependent on the partnership between the specific vendors. Therefore, it's essential you make sure the EMR system you're currently using is compatible with the topographer you plan to purchase.

Initial training on your chosen topographer begins with the vendor at the time of purchase and continues as you learn from your experience. The vendor should also train your staff on the technical aspects of topography, such as careful image acquisition and map selection. As a result of this training, your staff should be able to use your topographer quickly and accurately within a few weeks. Within a few months, workflow will improve as you work with your staff to discover patients who can benefit from the device.

To shorten the learning curve, many continuing education courses are available on topography and advanced contact lens fitting at both the local and national levels. Further, many RGP contact lens manufacturers offer basic topography training on their websites via web seminars and as a part of their specialty lens design tutorials. Also, these companies have expert consultants who can help you interpret your patients' topography maps via e-mail and even schedule in-office fitting sessions.

Because topography maps enable you to cut short the journey toward diagnosis for patients who have corneal issues and provide the most accurate treatment, a topographer is an invaluable diagnostic device to both increase patient satisfaction and your practice revenue. OM

Dr. Anderson practices in suburban Chicago, specializing in orthokeratology, keratoconus, post-surgical lens fits and anterior segment disease. E-mail her at

Optometric Management, Issue: April 2010