Combining placido and oct imaging technologies bringing diagnostic power to corneal analysis
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Combining placido and oct imaging technologies bringing diagnostic power to corneal analysis

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    Combining placido and oct imaging technologies bringing diagnostic power to corneal analysis Combining placido and oct imaging technologies bringing diagnostic power to corneal analysis Document Transcript

    • Combining Placido and OCT Imaging Technologies: Bringing Diagnostic Power to Corneal Analysis 8 Shareef Mahdavi • SM2 Strategic • Pleasanton, CA 7 The ability of ophthalmic clinicians to evaluate the cornea a direct and magnified view of the cornea; keratometry,has improved dramatically over the past quarter century. From measuring the change in curvature in the central 3 mmthe era of manual keratometry, new methods of imaging and of the cornea; and contact pachymetry, showing cor-analyzing corneal structure have emerged and have moved cor- neal thickness at each point of applanation. By the midneal care from an analog to a digital world. 1980s, published papers by Rowsey, et al showed how In the past 10 years, an explosion of technology has emerged Placido rings could be used to construct the cornea, andthat at times can overwhelm the eye care practitioner. SM2 in 1987 Stephen Klyce, PhD (along with Leo Maguire,Strategic was asked by Carl Zeiss Meditec (Dublin, CA) to help MD) introduced the color-coded contour map and scaleeye doctors understand the path of development that has taken to standardize interpretation, which evolved and becameplace and the tools that are now available to help with corneal an ANSI Standard. The following year saw the intro-analysis in everyday clinical practice. Three leading corneal spe- duction of the first computerized corneal topographercialists as well as a pioneer in corneal imaging were interviewed: (Computed Anatomy). The modern age of corneal imag-Amin Ashrafzadeh, MD (Modesto, CA), Robert Cionni, MD (Salt ing was officially underway.Lake City, UT), Roger Steinert, MD (Irvine, CA) and Stephen Since that first device, innovation in both imagingKlyce, PhD (Port Washington, NY). These doctors provided their and interpretation has been spurred by clinical needperspective on the technological milestones that have led to the and the rise of refractive surgery. In the 1990s, cornealcurrent state-of-the-art in corneal imaging. topography proliferated and gave refractive surgeons This report summarizes those interviews and intends to pro- the ability to measure the eye’s surface out to 10 mmvide ophthalmologists with an appreciation of how rapidly the (ie, beyond the optical zone) both before and after laserfield has changed, while offering guidance in terms of decision- vision correction. Devices from Tomey, EyeSys, andmaking with respect to future investment in corneal diagnostics. Humphrey (acquired from ORC) proved most popular with clinicians. By the late 1990s, surgeons realized thatTechnology Development they needed a better way to screen for corneal thinning The past quarter century has provided stellar innova- and determine which prospective LASIK patients weretion in the realm of imaging and diagnosis of the cornea most at risk for ectasia and/or keratoconus.(see Figure 1). For most of the 20th century, clinicians Product developers focused on new approaches tohad three basic tools available: the slit lamp, providing imaging. Orbtecs Orbscan device used a scanningFigure 1: 25 Years of Corneal Analysis Development Timeline 1987 Late 1980’s 2001 2005 2009 Klyce color scale Ultrasonic Scheimpflug Anterior Placido + to standardize biomicroscopy corneal segment OCT interpretation tomography OCT (Zeiss) (Oculus) (Zeiss) 1984 1987 Early 1990’s Mid & Late 1990s 2000 2002 2007 First papers on First Commercial Slit scanning Placido + Digital VHF Placido + use of Placido computerized Placido devices device wavefront ultrasound Scheimpflug to construct/ Placido + slit (Tomey, EyeSys, (Orbscan I) (Nidek) (Artemis 2) (Ziemer) model cornea device Humphrey) Slit scan + Placido (Computed (Orbscan II) Anatomy) 1984 1990 2000 2009
    • slit-beam to image the back surface of the cornea, giv- measuring corneal thickness manually at a handful ofing clinicians posterior measurements and the ability well-spaced locations in the central cornea.to calculate elevation from the front to the back of While this device could be used in tandem with athe cornea. It was limited to 4 diopters of elevation corneal topographer to provide greater information, itchange and required higher-skilled technicians to pre- initially lacked the interpretative power afforded by thevent patient eye movement and get reliable readings. In Holladay report. By 2007, corneal analysis software for2000, Nidek’s OPD Scan combined Placido + wavefront the ATLAS 9000 (known as Pathfinder II) gave clini-measurement in a single device. The use of ultrasound cians an anterior topographic screening module to help(e.g., ultrasonic biomicroscopy) gave high quality images identify abnormal corneal conditions. And by 2009,of corneal structure, but had fallen out of favor with Zeiss linked both the ATLAS and Visante together, call-clinicians due to the required contact via a probe or ing the merged technologies Visante Omni. Each devicewater bath. In contrast to Placido-based topographers, now accessed the other’s data, first to ensure properOculus Pentacam tomographer used slits to generate biometric registration of the eye, then to conduct pre-cross-sections of the cornea and reconstruct them into a cise analysis of corneal structure and changes over time.singular image. There were now two different technolo- Interpretation was greatly enhanced when Visante Omnigies popular for clinical incorporated the tradi-diagnosis, each deriving Figure 2: Corneal Imaging Technologies and Applications tional Holladay reportits final answer from plus several new color-different approaches: GALILEI ORBSCAN PENTACAM VISANTE OMNI scale maps to help diag-the Pentacam, using Placido + Placido + Placido nose, specifically earlyScheimpflug imaging, TECHNOLOGY: Scheimpflug Slit Scanning Scheimpflug + OCT corneal pathology suchmeasured elevation Anterior & Posterior as suspect keratoconus. Topographydirectly and then calcu- Narrow angle evaluation Clinical Significancelated corneal curvature, Clear Corneal Woundwhile Placido measured Evaluation Many diagnosticcorneal curvature Cataract Evaluation and innovations sought todirectly. IOL Placement Analysis improve upon Placido Surgeons were drawn Evaluation of Pars Plana measurements andto the Pentacam’s ease- Corneal Transplant render them obsolete, Planning & Follow-up of-use with patients yet hindsight reveals a Iris Tumors and the interpretive different outcome. “We Imaging Through Opaque/software developed by White Corneas have come full circle,”Jack Holladay, MD; as Phakic IOL Planning noted Roger Steinert,a result, the Pentacam Full Capability Limited Capability No Capability MD. “We now realizesold briskly to refractive Placido-based technolo-surgeons in the early 2000s. By 2005, Carl Zeiss had gies as the most reliable way to analyze anterior cornealdeveloped an anterior segment OCT device to comple- topography.” Cornea specialist Amin Ashrafzadeh, MDment their rapidly-adopted posterior segment version for has been using corneal topography to plan and analyzeuse in retina and glaucoma. The Visante OCT provided surgical outcomes since 2001 and believes the Placidoextremely crisp images of corneal structures, allow- disk “remains one of the most essential instruments foring both increased width of coverage (out to 16 mm) as imaging the corneal surface.” He lamented, however,well as depth of coverage (up to 6 mm). This advanced that “up until several years ago, you still had a lot oftechnology took multiple “Optical A-scan” images of work to do in figuring out why you had an odd-lookingthe cornea and then re-constructed these slices into a cornea.”“Optical B-scan” image, putting directly into the clinic That burden changed, according to both Steinertimages never before available (except in part from histol- and Ashrafzadeh, when surgeons gained the ability toogy slides). The new “map” of the eye included a differ- correlate topography with corneal thinning. Both hadent pachymetric approach that automated pachymetry attempted to use Scheimpflug – which had become com-measurement with exponentially greater data points monplace for routine refractive cases – to help with(2,048). This eliminated the potential inaccuracy from this more sophisticated analysis, but found that they
    • were too often led down in reaching diagnosis,” remarked Dr. Steinert. Figure 2“The real value of the wrong path in reach- shows the different capabilities of four popular cornealVisante Omni is its ing the correct diagnosis. imaging devices. An earlier survey by SM2 Strategic of 32 “Anterior topography from of the first users of Visante showed significantly greaterability to evaluate the Pentacam was pointing usage than anticipated once they had the device in theirnumerous data... to a completely different practice and had become familiar with its capabilities.all in one place” area for astigmatism, and treating this made cylinder Interpretation Becomes Critical Robert Cionni, MD worse not better,” said Dr. The sheer volume of data on the cornea now avail- Steinert. “I went back and able to clinicians places a premium on software analyticschecked the Placido images and found they were accurate; that can reliably distill the images and data points so theythis triggered the realization that we needed to go back to make sense in diagnosis. “The amount of informationPlacido based topography.” While the ability to use a sin- can be overwhelming,” according to Dr. Ashrafzadeh.gle device was indeed convenient, Dr. Ashrafzadeh found “The Holladay report helps tremendously but still hasthat the Pentacam software would “fill in” missing data deficiencies that cause me to evaluate the ring image over-points improperly on slightly irregular surfaces. “I liked laid atop the report.” The real value of Visante Omni,the way that Scheimpflug image looked, but even looks remarked Dr. Cionni, is it’s ability to evaluate numer-can be deceiving.” Both remarked that the presence of ous data such as topography, corneal aberrations, ICLartifacts in Scheimpflug images of suspicious corneas positioning, pachymetry, ectasia analysis, angle measure-has been a troublesome aspect of that technology. ments… all in one place. Indeed, clinicians should view This issue appears to have been solved through the Visante Omni as a workstation with multiple capabilitieslinking of Placido and OCT, and the applications extend rather than a niche device.beyond the cornea. Robert Cionni, MD has found thatthe Omni allows him greater ability to evaluate aberra- Early Detection Capabilitiestions relevant only to the cornea. “I get better astigmatic Each surgeon interviewed agreed that the Pentacamanalysis with Atlas and my toric IOLs are now more pre- itself is sufficient for the refractive surgeon who is mainlydictable,” according to Dr. Cionni. concerned about corneal elevation. If you are dealing Evaluation of glaucoma patients has been greatly only with normal corneas, they say, then the Pentacamenhanced by Omni. “Pupil size and the resultant angle is fine. The dividing line is drawn around earlier detec-opening are not influenced by Visantes non-visible light, tion of corneal abnormalities. Dr. Ash did a comparisonproviding an exquisitely accurate measure of physiologic study of 60 eyes, measuring them both on the Pentacamangle opening,” stated Dr. Ashrafzadeh. and the Visante Omni. His findings were that on corneas with no prior surgery and no opacities, there was goodEfficiency in the Clinic agreement between the devices. But in patients with Some clinicians view it a disadvantage to have to prior refractive surgery, significant differences emerge. Inuse two devices rather than one as part of their corneal this study, Visante showed much greater consistency inscreening. Dr. Ashrafzadeh finds it actually works to his posterior surface findings compared to the variability inadvantage. “I can counsel the patient while I’m doing readings from the Pentacam, which also tended to under-their Omni readings.” He described how this interaction detect post-LASIK ectasia. The findings on the Visanteallows him to educate the patient and discuss candidacy Omni correlated much more closely to what he was see-for refractive surgery, while also giving the patient “sig- ing clinically.nificant confidence in seeing the whole process in action. This type of study illus-Omni takes away a lot of the mystery by allowing me to “At present, Visante trates the sentiment of Dr.describe what I’m doing and what the images are telling Omni is the only Steinert regarding a surgeon’sme…in real time.” technology that I ability to trust the device Dr. Cionni added, “I am able to show a patient how you are using: “You needremoving their astigmatism will improve their quality of can truly rely upon confidence in your devicevision as well.” for subtle changes.” if you are doing refractive “If you use Visante for other applications such as Roger Steinert, MD surgery to pick up the subtleevaluating the angle, then you actually gain efficiency things like Form Fruste
    • Keratoconus. At present, Visante shown in Figure 3. As patient loads increase with the“You must use Omni is the only technology aging population, this justification becomes even morePlacido for early that I can truly rely upon for attractive and helps the ophthalmic practice harness the subtle changes.” power of these two innovative technologies.detection of Stephen Klyce, PhD, widelyKeratoconus” regarded as a pioneer in corneal Summary and Discussion Stephen Klyce, PhD imaging and analysis, believes Ophthalmic diagnosis and treatment paradigms have that Scheimpflug is not well evolved significantly in the past two decades. Better diag-suited to screening the cornea, as it is 20x less sensi- nostics for the cornea have improved surgeons’ abilities totive than Placido to changes in the amount of corneal the point that most recognize they can perform refractivecurvature. “The use of posterior corneal data has not surgery on patients who were not considered candidatesbeen shown convincingly to be useful for early detection. ten years ago…and vice-versa. The negative publicity sur-Anterior surface Placido is the standard; you must use rounding LASIK in the past several years can be attrib-Placido for early detection of Keratoconus.” uted in part to the lack of understanding of the cornea in the initial period following US commercialization. WhatReimbursement surgeons needed – and now have – is a clinical “safety Lastly, changes in reimbursement effective January net” as a result of technological innovation.2011 puts into effect a new code for Anterior Segment The power in diagnosis afforded by Visante OmniOCT (92132, a Category 1 CPT code). Prior to this, and its marriage of Placido and OCT technology raisesdoctors were treated unevenly. Some were able to bill the bar for all ophthalmic surgeons in several respects.and get reimbursed, while others’ claims were denied. First, increased understanding of the risks presented byThe presence of a new code – specifically for anterior abnormal corneas – and how to best mitigate those riskssegment OCT – will help achieve a consistency that is – puts a premium on being able to detect it earlier in itsbetter overall when one considers patient care standards development. Second, an aging population will bring anon a national basis. Although it is tempting to bemoan increasing prevalence of all eye diseases, including thosethe fact that the code now pays bilaterally (i.e., $36.35 in the anterior segment (e.g., glaucoma). Taken together,national average reimbursement for both eyes), the previ- these two issues put additional pressure on clinicians toous SM2 survey showed users billing an average of 18 get the right diagnosis in an efficient manner. And justuses per month out of 47 uses overall (including refrac- as the lines between refractive and cataract surgery aretive evaluation). With a specific billing code in place blurring, technology such as Visante Omni is making itto guide clinicians, one would expect the reimbursable possible for all ophthalmic clinicians to more accuratelyusage to increase significantly. A pro-forma analysis is diagnose disease. Figure 3: Return On Investment VISANTE VISANTE omni KEY ASSUMPTIONS Cost Cost Per Month $708 – $1,018 $982 – $1,382 Monthly lease cost includes device and service for 5 years. Range reflects value of trade-in, and new/refurbished unit. Reimbursed Procedures OCT (CPT code 92132) $647 $647 18 reimbursed procedures per month (from prior SM2 survey of Visante users); national average reimbursement of $36.35 bilateral Corneal Topography - $700 20 submitted claims per month (25% of 80 eyes per month) (CPT code 92025) $35 average reimbursement Non-Reimbursed Procedures OCT $1,044 $1,044 29 per month (from prior SM2 survey of Visante users); $36 per eye component of elective fee, built-in to refractive fee for LASIK and/or Premium IOLs Total Return per Month $1,691 $2,391 Return on Investment Ratio 1.7x – 2.4x 1.7x – 2.4x© Copyright 2011, SM2 Strategic. All Rights Reserved.