It is an exciting time for refractive surgery with next-generation diagnostics becoming available to physicians that will have a significant impact on the level of treatment they can offer to their patients. Improvements in anterior segment imaging using high-frequency ultrasound and optical coherence tomography (OCT) are providing ophthalmologists with tools that allow them to evaluate pathologic corneas, eyes with corneal or anterior disease, and the results of anterior segment surgery.
The utilization of several recently developed or evolving tomographers will prove advantageous for opthalmologists. The instruments offer a higher degree of detail because the wavelength of light is much shorter in the anterior segment. These tomographers can detect minute changes in corneal thickness, thus allowing the successful identification and disqualification of patients who may have early keratoconus or other corneal-thinning disorders that would contraindicate corneal refractive surgery. In addition, the devices permit ophthalmologists (1) to determine the exact position of both phakic and aphakic IOLs in the anterior segment and (2) to evaluate the fixation, centration, and location of these lenses within the eye. The tomographers can also calculate curvatures in the central cornea in a 1.5-mm diameter, a measurement not provided by topographers or keratometers.
Ophthalmologists are able to achieve a higher level of accuracy with IOL power calculations by means of new devices that facilitate precise optical axial length measurements, even in eyes that have fairly transparent media. Combination units now provide topography, wavefront analysis, and refractions. By ensuring that the patient's fixation is the same for all three tests, these devices eliminate the problems of alignment and differences between the measurements that would make comparability inadequate. These new technologies have given anterior segment surgeons imaging instruments that enable them to monitor each patient's optical system better.
The biggest deterrent to the clinician's adoption of new diagnostic technologies will be their cost. Although the devices represent significant investments, the equation does not simply involve economics. The existence of reimbursement rates and the benefits gained through utilization of the devices (such as physician access to useful information not previously provided) will also be factors that dictate how quickly the different technologies will penetrate the ophthalmic market.
In today's environment, obtaining reimbursement for new diagnostic tests is difficult due to the coding process that must be completed through the Centers for Medicare and Medicaid Services (CMS). The establishment and implementation of CMS codes that reflect the value of certain procedures involves a somewhat lengthy process, and actual reimbursement may be significantly delayed. The expense involved in buying an instrument before a substantial reimbursement code is in place is hard to justify. As a result, it is taking a long time for these products to make an impact on the market.
Physicians must balance the quality of care they can provide and that which the CMS regulatory system will enable them to afford. Quality of care always prevails, but it is a slow process, as evidenced by the eventual integration of topographers in the 1980s and tomographers in the 1990s. Nevertheless, I believe that new diagnostic instruments will be commonly available in clinical practices within 1 to 2 years.
Jack T. Holladay, MD, MSEE, FACS, is Clinical Professor of Ophthalmology at Baylor College of Medicine in Houston, and he is Founder and Medical Director of the Holladay LASIK Institute in Bellaire, Texas. Dr. Holladay may be reached at (713) 668-7337; fax: (713) 668-7337; firstname.lastname@example.org; Web site: http://www.docholladay.com.
Zeiss IOLMaster Non-Contact Laser Biometry
Carl Zeiss Meditec Inc., Dublin, California
(925) 557-4100 or (877) 486-7473
• Allows personalization of integrated lens constant
• Supplies IOL formulas for standard and postrefractive surgery
• Offers electronic medical record integration and data transfer capability to the Holladay IOL Consultant Professional program
The IOLMaster provides patients with non-contact, no-water bath comfort, while technicians benefit from the ease of use and quick measurement time that facilitates patient flow. The multifunction platform offers surgeons a high level of confidence in IOL power calculations and resulting outcomes. The IOLMaster reportedly eliminates the technician-dependent results that often limit ultrasound accuracy.
Marco 3-D Wave*
Marco, Jacksonville, Florida
(800) 874-5274 or (904) 642-9330
• Quantifies internal aberrations and astigmatism
• Detects decentered IOLs
• Shows progression of lenticular changes in difference maps and measures angle kappa
The 3-D Wave, a combination autorefractor/keratometer, corneal topographer, and wavefront aberrometer, may be a useful tool for any refractive IOL practice. The product effectively separates the cornea from the entire optical system for evaluation and analysis, with Zernike graphs clearly indicating optical aberrations. Lens vaulting is visible. Refractions are displayed in 2.6-, 3.0-, and 5.0-mm increments to examine how the patient's vision varies throughout the day as pupil size changes.
The 3-D Wave aids physicians with IOL selection by providing negative and positive spherical aberrations and displaying mesopic and photopic pupil sizes for each patient prior to implantation. The combination unit reportedly measures 100% of a patient's optical system in a matter of seconds, thus allowing the clinician to observe and diagnose every aspect of the visual system.
*This product is manufactured for Marco by Nidek, Inc. (Fremont, CA), a company that produces and markets the device as the OPD-Scan.
HRT Corneal Microscope
Heidelberg Engineering GmbH, Dossenheim, Germany
• Allows the monitoring of LASIK flaps and of the regeneration of nerves following surgery
• Performs functions of a powerful histological detection instrument
• Monitors long-term contact lens wear
• Semi-automated cell counting
• Epithelial and intracorneal pachymetry
The HRT Corneal Microscope uses confocal scanning laser technology to image the entire cornea, layer by layer, with a 1-µm resolution. The properties of the microscope, combined with confocal laser scanning, make in vivo imaging possible and provide the clinician with the capability to see the complete structural histology of the cornea from the superficial epithelium to the endothelium. Diseases such as Fuch's dystrophy, lattice dystrophies, bacterial keratitis, and Acanthamoeba may be monitored. In addition, the conjunctiva and sclera may be imaged with the microscope to allow applications such as the examination of glaucoma filtering blebs. The HRT Corneal Microscope features multiple acquisition modes, including movie formats, cell-counting abilities, and image export features.
Oculus, Inc., Lynnwood, Washington
• Displays and quantifies opacification of the crystalline lens
• Achieves keratoconus detection and Zernike analysis of the cornea
• Provides tomographic images of the anterior segment
• Calculates the cornea's true net power for more accurate IOL power calculations in postrefractive surgery patients
• Measures the vault of an IOL from any surface in the eye
Oculus, Inc., offers the Pentacam, a rotating Scheimpflug camera that performs topographic measurements (axial, tangential, and height maps) of the entire anterior and posterior surfaces of the cornea from limbus to limbus. The device analyzes the anterior segment with pachymetry readings at any location and calculates its angle, volume, height, and diameter. Chamber height may be measured at any location.
The rotating measurement takes 3-D Scheimpflug pictures in less than 2 seconds. An additional camera detects all eye movement and corrects the Scheimpflug image. In the 3-D mode, the Scheimpflug camera takes up to 50 scans, and each scan has 500 images for a total of 25,000 true measurements and elevation points, thereby providing the most accurate posterior cornea and other measurements available, according to the company.
Ultralink LLC, St. Petersburg, Florida
• Provides accurate measurements of corneal layers and anterior segment anatomy
• Performs scanning on multiple meridians
• Produces highly detailed pre- and postoperative imaging with radial, angle-to-angle, and sulcus-to-sulcus measurements
The Artemis-2 is a VHF high-resolution (50MHz) ultrasound system that provides the most accurate measurements of the corneal layers and anterior segment, according to Ultralink. Derived from technology developed at the Weill Medical College of Cornell University in New York, it is an evolving biometric platform technology that can assist the ophthalmologist with refractive surgery and other ocular challenges. The Artemis-2 is the only ultrasound system to provide a visual axis centration beam with a simultaneous optical image of the eye to ensure positional accuracy.
Advanced digital-signal processing exclusive to the Artemis achieves accurate measurements by avoiding problems related to the refractive distortion. The company asserts that only this imaging system can achieve direct quantitative measurements beyond opaque structures. The extension of the Artemis-2 technology to imaging and perfusion analysis of the retina, choroid, and underlying tissues has been demonstrated, which may lead to improved stratification, start- and end-point data for evaluation and treatment of age-related macular degeneration.
This technology can precisely determine the efficacy of microkeratomes in 3-D and facilitates the assessment of complications in LASIK and refractive implant surgery. “We are dealing with a technology that is enabling ophthalmologists to see beyond the surfaces they have been examining in the last few decades with microscopes,” stated Dan Z. Reinstein, MD, co-inventor of the Artemis-2. “We are now entering into an era of sub-surface anatomy and microstructure to better plan surgery and treatment modalities.”