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Corneal topography makers discuss their latest offerings

Issue: November 1997

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Alcon EyeMap EH-290 Corneal Topography System

Alcon Laboratories Inc.
6201 South Freeway
Fort Worth, TX 76134
(817) 551-4571
Fax: (817) 551-4030
Dean Burns, product marketing manager for topography

The Alcon EyeMap EH-290 Corneal Topography System is an electro-optical instrument capable of measuring the shape of the cornea in very fine detail. The EH-290 will analyze the data collected using two separate algorithms: axial or instantaneous rate of change. This type of analysis provides the practitioner with fine details regarding the condition of the corneal surface. The EyeMap EH-290 also uses a 23 narrow ring modified placido disk configuration that aids in the sensitivity of the system and provides total corneal coverage. The system, with its patented auto features, icons and on-screen help text make it easy for any technician to operate the unit with minimal training. Additionally, the unit's auto focus and centering simplify the collection of data and eliminates operator bias. A 23-ring, aspheric pattern with more than 8,000 X-Y-Z data points facilitates greater accuracy, particularly in the peripheral corneal region. Finally, the EyeMap EH-290 offers very versatile software including: Advanced Contact Lens software, Keratoconus Detection, Corneal Statistical Information and Advanced Communication software.

Keratron Corneal Analyzer

Alliance Medical Marketing Inc. (Distributor for Optikon)
2250 Third Street South
Jacksonville Beach, FL 32250
(800) EYE-TOPO
Fax: (904) 247-3133
Scott Lewis, president

"The Keratron corneal topographer automatically captures only properly focused images, guaranteeing accurate, reproducible maps,'' Mr. Lewis said. "It is the only topographer measuring the Instantaneous Rate of Curvature using its own original Arc Step Method of mapping that maps from vertex to periphery without smoothing or shadows to fill in with guesswork or extrapolation to make maps larger."

The Keratron uses corneal heights (to a 0.25-micron central zone and a 1-micron periphery accuracy) and tear clearance as contact lens fitting parameters, allowing the optometrist to fit abnormal corneas. The Keratron can map from the corneal apex, from the line of sight or from any corneal positions. The focusing system has a sensor that detects the corneal apex and permits capture of only perfectly focused images.

Dicon CT 200

Dicon
10373 Roselle Street
San Diego, CA 92121
(800) 426-0493
Fax: (619) 554-0332
Michael L. McKay, VP, marketing & sales

"We at Dicon feel we've reinvented corneal topography with the introduction of our new system, the CT 220," Mr. McKay said. "The Dicon CT 200 is the result of years of research and experience with many innovative features that address the shortcomings of current instrumentation. The CT 200 is simple to operate, with auto self-align, and auto self-focus systems that ensure consistent, accurate reading, without a joystick. Designed on a 32-bit platform, the CT 200 produces color maps in less than 4 seconds, making it many times faster than competitive models. Affordable pricing and product innovation improves the standard of care in any eye care office."

Mark R. Miehle, president and CEO of Dicon, said, "This corneal topographer is not just another pretty picture. With the extraordinarily low introductory price, the CT 200 is the best value for a corneal topographer capable of replacing the keratometer."

Euclid ET-800

Euclid Systems Corp.
2810 Towerview Road
Herndon, VA 20171
(888) 3EUCLID
Fax: (201) 773-6334
Dennis Telischak, VP, marketing

"The Euclid ET-800 uses a revolutionary new technique called Fourier Profilometry, that measures true corneal elevation without assumptions about corneal shape, providing accurate graphic representations using X, Y, Z coordinates," Mr. Telischak said. "With an image field of 22 mm X 17 mm, the ET-800 provides full scleral and corneal coverage. Conventional corneal topographers measure a much smaller area, with accuracy dropping off significantly towards the periphery. To achieve true elevation coordinates, this method analyzes over 300,000 data points with each point accurate to approximately 1 micron."

Mr. Telischak said Fourier Profilometry is a new technology in which two identical sine wave patterns are projected in rapid sequence onto the corneal surface. The resulting image is captured with a CCD array camera, and the Euclid ET-800 produces an extract mapping of the corneal elevation.

"Elevation mapping is true topography," Mr. Telischak said. "Fourier Profilometry provides meaningful measurement of the central cornea. The Euclid ET-800 also features a normalized relational database, elevation mapping of the sclera, low light level for maximum patient comfort, adjustable diameter for corneal analysis, adjustable diameter for simulated keratometry, exact measurement of corneal diameter, our new Exam Wizard proprietary software, which simplifies and automates the examination process, and our Patient Finder proprietary software, eases operation and streamlines the patient file management process."

EyeSys Vista Hand Held Corneal Topographer, EyeSys System 2000

EyeSys Technologies
3 Morgan Drive
Irvine, CA 92618
(714) 859-0656
Fax: (719) 951-7218
Beth Soper, clinical affairs specialist

The newest instrumentation from EyeSys Technologies is the EyeSys Vista, a hand-held corneal topography system utilizing EyeSys System 2000 software.

"This small and lightweight unit brings with it the quality, accuracy and reproducibility standards that have become the hallmark of EyeSys products for more than 10 years," Ms. Soper said. "The EyeSys Vista has a footprint of 8" x 5 1/2" and quickly captures and processes exams using automatic focusing and automatic image acquisition."

Currently, EyeSys Technologies also offers the three-camera design of the System 2000, which uses an aspheric algorithm for image processing, producing highly accurate and repeatable exam results. Included is state-of-the-art software such as Pro-Fit Contact Lens Fitting, the Holladay Diagnostic Summary 2000, EyeSys 3D Cornea Studio, and EyeSys DirectNet e-mail transfer of patient exams. "LAN PAKS (for local networks) complete with EyeSys ViewStations are available for optimum office efficiency in a network environment," company representatives said.

Humphrey Atlas Corneal Topography System Model 991, Humphrey Atlas Eclipse Corneal Topography System Model 992

Humphrey Systems
2992 Alvarado Street
San Leandro, CA 94577-0700
(800) 227-1508
(510) 895-9110
Fax: (510) 483-8025
Thomas McKay, product manager

The Atlas Model 991 has a 12" X 18" footprint, thousands of data points, a powerful computer and superior central and peripheral coverage. It includes powerful software and hardware to complement any refractive, surgical or contact lens practice. Optional software includes Pathfinder Corneal Analysis, Advanced Refractive Diagnostics, PRK Simulated Ablation and Healing Trend Display as well as the MasterFit Contact Lens module. Hardware features include ethernet and modem ports for LAN compatibility and Internet exam transfer.

The Atlas Eclipse Model 992 features a powerful computer and streamlined software, reducing chair time and increasing patient throughput. Unique ultra-low illumination reveals true pupil size and eliminates sensitivity for recent post-ops. An optimized placido design provides maximal peripheral coverage and allows complete visualization of developing pathologies and surgical ablation zones.

Orbshot, Orbscan II

Orbtek
3030 South Main St., Ste. 600
Salt Lake City, UT 84115-3554
(801) 484-8777
Fax: (801) 484-3982
Trudy Warner, marketing assistant

Orbshot is a placido-based corneal topographer designed for quick, initial screening of the anterior surface of the cornea. This small, hand-held portable topographer operates from a laptop computer, making it ideal for comanagement programs and data exchange between OD and MD offices.

Using a combination of reflection and scan technology, Orbscan II is a useful diagnostic tool for any aspect of refractive surgery and the surgical enhancements of problem patients. The new Orbscan II features hybrid imaging, analyzes 12,000 to 14,000 data points per exam and processes images in less than 1 minute.

PAR Vision Accugrid

PAR Vision Systems
8383 Seneca Turnpike
New Hartford, NY 13413
(315) 738-0600
Fax: (315) 738-0562
John Nabors, product manager

PAR Vision's new Accugrid Corneal Topography System features the same patented rasterstereography technology used in the original slit lamp mounted-PAR CTS product line. Beyond this basic similarity, the Accugrid is a completely different instrument. Packaged as a stand-alone instrument, this new unit employs a video based alignment mechanism that provides graphic positioning feedback to the operator through the computer monitor. An Accugrid unique autofire feature permits the instrument to automatically capture the topography when focus and alignment are optimal. This provides accuracy, repeatability and ease of use.

Starting with a detailed, elevation-based, 3-dimensional model of the corneal surface, the Accugrid provides data to the practitioner in terms of surface elevation, axial/tangential curvature and true refractive power. With a field of view of 20 mm X 17 mm, accurately measured (not interpolated) corneal coverage that extends out onto the sclera is typical.

Available programs for the Accugrid include the CL-CTS contact lens fitting program utilizing its elevation-based model of the cornea and large area of directly measured coverage to fit a wide range of soft and rigid contact lenses. The lens professional can use any number of standard or custom fitting approaches. Fit quality can be gauged using a simulated fluorescein pattern or number of numerically based indices.

Technomed C-Scan/Color Ellipsoid Topometer

Technomed Technology
5132 Bolsa Ave., Ste. 104
Huntington Beach, CA 92649
(714) 899-2133
Fax: (714) 899-2131
Herbert von Wallfeld, president
Dirk Keune, product manager

Color ellipsoid topometry was developed in cooperation with the Division of Experimental Ophthalmic Surgery, University Eye Clinic of Tubingen, Germany.

The patented color system made up of multicolored placido rings and a high-resolution PAL color video camera ensures detection of up to 10,800 measurement points. The C-Scan can localize the reflection of the fixation light inside the smallest measuring ring.

The C-Scan is set up on a real point of reference ("line of sight"). Within the central area (0 to 3 mm) alone, the system detects about 4,000 measurement points. With the captive field focusing, the system mathematically corrects defocusing due to the Z-axis correlation within a defined area shown on the unit's monitor. In addition to many standard reports, new software provides some powerful mapping capabilities, such as 3-D/Elevation maps, Snell's Power Maps, statistics, Astigmatism Analysis, the unique Ray Tracing software and a highly sophisticated SRM/Toptest contact lens fitting program.

There are no misleading measurements by virtue of the colored placido rings. Information about the visual center by locating line of sight and a rapid and user-friendly archiving system are also important attributes to the Technomed C-Scan/Color Ellipsoid Topometer.

Tomey AutoTopographer

Tomey Corporation
325 Vassar Street, Second Floor
Cambridge, MA 02139
(617) 864-6488
Fax: (617) 864-6897
Anne Moskowitz, PhD, OD (ext: 726)

The TMS-3 is a new, portable, low-cost topography unit that provides the same accuracy and software features as Tomey's previous high-end systems. It offers several new features such as automatic acquisition. The patient looks into the device, which autofocuses, autoaligns and autoacquires an image of the cornea, with no operator intervention. The TMS-3 requires no in-service. The unit permits the user to supply his or her own computer, allowing for continual self upgrading. The fine ring spacing and short working distance provide high resolution and extensive corneal coverage. The low light level of the mires promotes patient comfort. Data collected from the TMS-3 may be represented via standard axial, refractive power, instantaneous radius of curvature or height maps, with multiple display formats available. Simulated K values, minimum K value, surface regularity index, surface asymmetry index and potential visual acuity are reported for every map. The TMS Contact Lens Wizard software automatically suggests the appropriate lens category and parameters, and modifications of the fit can be quickly assessed via interactive fluorescein displays. File handling software allows easy transfer of data to a mass storage device and communication software allows efficient use of the Internet or e-mail for file transfer.

Guide to Corneal Topography Systems

The following companies were also invited to submit information for the table and overview article: Marco Technologies, Nikon Inc. and Topcon America Corp.