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The Cassini diagnostic device (i-Optics; Figure 1) offers a suite of examinations including cor-neal topography, mesopic and photopic pupillometry, and

color photography for diagnos-tic purposes. The Cassini uses red, green, and yellow LEDs to perform what the manufacturer calls “true corneal shape analysis.”1 According to i-Optics, each LED is positioned in relation to its neighbors in order to give a GPS-like coordinate to each point. Patented multicolored LED point-to-point ray tracing, combined with second-Purkinje imaging technology, is used to measure the relative position of each point, with the three colors facilitating triangulation of the points (Figure 2). Elevation increases the distance between points, and depression decreases the distance. These prin-ciples allow accurate and repeatable measure-ments of total corneal astigmatism.

The Cassini does not use edge detection in its algorithms, as does conventional Placido-disc–based topography. Therefore, smeared or double-reflected LEDs

cannot skew results. This allows the device to image all corneas, even highly irregular ones.

The technology particularly supports toric IOL implanta-tion, providing information to select the power and proper positioning of toric IOLs. The device repeatably measures

the axis of cylinder to an accuracy within 3° (as com-pared with 13° with Placido technology) and the

magnitude to within clinical margins (2%), accord-ing to the company. Data capture is instanta-

neous, with submicron accuracy provided by the color LED triangulation technology. Alignment for data capture is intuitive, with color changes indicating the degree of correct alignment. Each image is stamped with the quality factor of the capture.

According to the company, the Cassini addresses the four most common problems

associated with astigmatism correction: (1) surgically induced

astigmatism, addressed by its accu-rate postoperative measurements; (2) preoperative measurement errors, addressed by its accuracy and preci-sion, (3) correct toric IOL alignment, addressed by its highly accurate marking capabilities, and (4) marking errors, addressed by its real-time eye-tracking systems.

With the Cassini tech-nology, there is no central corneal scotoma. The

Because the system does not use edge detection in its algorithms, smeared or double-reflected LEDs cannot skew results.

BY TIM DONALD, CONSULTING EDITOR

TRUE CORNEAL SHAPE ANALYSIS WITH THE CASSINI

(Images courtesy of i-Optics)

Figure 1. The Cassini diagnostic device offers a suite of examinations including corneal topography,

mesopic and photopic pupillometry, and color photography for diagnostic purposes.

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Commentary

Expertsfrom the

Highlights of the Cassini in Clinical Practice By Jonathan D. Solomon, MD

What is your overall impression of the Cassini?I have had the pleasure of working with the Cassini Corneal Analyzer (i-Optics) for more than 2 years. At first glance, it looks like any other topographer; however, when you see it in action and evaluate the performance, it is clear that the Cassini is indeed a differ-

ent breed. Trichromatic LEDs provide a detailed depiction of the anterior corneal surface that was not possible before with other devices, and, as a result, I have changed how I approach the corneal maps I traditionally use for assessing corneal shape. I tend to scrutinize the axial maps of other elevation-based devices—for instance, the Placido-ring display to evaluate a dry eye or the curvature maps for irregular corneas. The multipoint discrimination of the Cassini enables a more accurate and nearly complete representation of the anterior surface elevation and curvature, and its posterior corneal analysis provides infor-mation on total corneal power.

How do you use the Cassini in clinical practice?The Cassini delivers the preoperative data for my refractive cata-

ract platform. In conjunction with the Streamline upgrades to the Lensar Laser System (Lensar), the corneal refractive information is seamlessly and efficiently fed to the laser for arcuate incision plan-ning and reproducible clear corneal incision placement. (Editor’s Note: See Lensar to Integrate Wirelessly With Cassini for more information on the Streamline upgrades.) These features help to standardize my surgically induced astigmatism.

Furthermore, I have grown particularly fond of the Cassini Corneal Shape Analyzer for surgical management of corneal dis-ease. For patients with corneal ectasia, preoperative planning for intrastromal corneal ring segments and intraoperative guidance for conductive keratoplasty is driven by the Cassini system with remarkable precision.

What are the advantages of the Cassini compared with other ocular biometry technologies?

The distinct advantage is the enhanced assessment of the anterior corneal shape that is provided with the Cassini analyzer (Figure 1). The pseudorandomized color LEDs are superior to

traditional monochromatic Placido rings for detailed interpreta-tion of the anterior corneal curvature. For example, evaluation of an irregular, asymmetric cornea is frequently limited and a source for confusion with a traditional Placido device, and poor extrapolation with Scheimpflug tomography is frequently depicted as data dropout. By comparison, using the Cassini Corneal Shaper Analyzer, the indices over the focal areas of irregularity are preserved. In my clinic, the Cassini provides a wealth of knowledge regarding front and back corneal surfaces across the full spectrum of patient presentations.

Jonathan D. Solomon, MDn Surgical/Refractive Director of Solomon Eye Associates, Bowie,

Maryland n jdsolomon@hotmail.comn Financial disclosure: Consultant (i-Optics, TrueVision)

Figure 1. Capture screen of the Cassini (A). View of the corneal

topography examination (B).

A

B

(Courtesy of Jonathan D. Solomon, M

D)

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multicolored LED coverage is uniform across the entire cornea.

The information screen displays all rele-vant data, including the captured image with axis details, corneal elevation maps, tangen-tial and axial curvatures, corneal refractive power, and an overview of Zernike terms, in addition to measurement of steep and flat keratometry readings and astigmatism. Any two exams can be compared differentially. Measurable keratoconus indices include sur-face asymmetry and surface regularity.

The system’s topographic map displays include axial, refractive, tangential, eleva-tion, and higher-order aberrations, and its topographic indices include shape factor, eccentricity, asphericity, and form factor. The device can connect to femtosecond lasers, operative guidance systems, and toric IOL calculators. A patient manage-ment program is incorporated. n

1. Cassini True Technology. i-Optics website. http://i-optics.com/us/products/cassini-2/true-technology-2/. Accessed June 22, 2015.

LENSAR TO INTEGRATE WIRELESSLY WITH THE CASSINI Lensar announced recently that it has received the CE Mark for

Streamline application upgrades, a suite of five new applications integrated into the Lensar Laser System, according to a company news release. With the addition of Streamline, the Lensar is now the first femtosecond laser platform for cataract surgery that enables wireless integration with a preoperative diagnostic device, according to the company (Figure 1). The suite also enables iris registration, cataract density imaging, creation of customized frag-mentation patterns, and arcuate incision planning.

“The Streamline upgrades to the Lensar Laser System … allow surgeons to fully automate and customize critical planning and execution of refractive cataract surgery for the first time,” Nicholas T. Curtis, Lensar’s CEO, said in the news release.

According to the company, one benefit of this integration is the ability to wirelessly transfer preoperative undilated iris images from a diagnostic device to the femtosecond laser. This feature allows surgeons to evaluate the image while the eye is fully docked under the laser. Additionally, the system can automatically compensate for cyclorotation by adjusting incision placement for improved refractive outcomes.

The Streamline upgrade is currently available only with the Cassini (i-Optics); Lensar is working to integrate additional topog-raphers, including the Aladdin Biometer (Topcon).

“Lensar’s integration of preoperative diagnostics represents

significant innovation in the femtosecond cataract procedure that we anticipate will result in improved surgical efficiency and outcomes for patients,” Gerd U. Auffarth, MD, PhD, Medical Director, University Eye Clinic Heidelberg, said in the news release. n

Figure 2. Patented multicolored LED point-to-point ray tracing provides a GPS-

like analysis of the cornea.

Figure 1. The Lensar Laser System now integrates wirelessly

with the Cassini.

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