Cataract surgery diagnostics spotlight continues to shine on integration with surgical technologies

Reviewed by Samuel Masket, MD, and Mark Packer, MD

The trend for advances in intraoperative imaging systems and linking of diagnostic and surgical technology continued in 2015, bringing cataract surgeons more opportunity for increasing workflow efficiency and improving patient outcomes.

Much of this innovation has involved automation of femtosecond laser applications, and it is these developments that will confer real advantages for the femtosecond laser systems, according to Mark Packer, MD.

“Until now, use of the femtosecond laser has brought only incremental advantages to cataract surgery,” said Dr. Packer, clinical associate professor of ophthalmology, Oregon Health and Science University, Portland. “By lessening the amount of ultrasound energy needed for lens removal, femtosecond laser-assisted cataract surgery (FLACS) may allow for quicker visual recovery.

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In addition, final visual outcomes may be a little bit better with FLACS than conventional phaco, and safety wise, there may be some advantage for FLACS, depending on the individual surgeon’s skills, he noted.

“However, in each of those areas, the difference compared to standard phacoemulsification is small, and overall, it is hard to say that FLACS is significantly better than standard phacoemulsification in terms of effectiveness and safety outcomes,” Dr. Packer said.

“Now, however, I think that FLACS is really beginning to shine because of the integration of preoperative and intraoperative diagnostic technology that allows for image-guided automated surgery,” Dr. Packer said. “These developments translate into huge time savings in terms of surgical planning, and they can improve outcomes by increasing treatment accuracy and eliminating the potential for errors that can occur with manual data entry.”

Enhancing asitmatism correction

Enhancing astigmatism correction

Alcon was the first to offer a suite of instruments to streamline and automate surgery through acquisition and electronic transfer of preoperative keratometry to the femtosecond laser and with intraoperative verification of astigmatic correction using arcuate incisions or toric IOLs. With its acquisitions of the ophthalmic division of SensoMotoric Instruments in 2012 and WaveTec Vision in 2014, Alcon introduced its portfolio of Cataract Refractive Diagnostics Technologies, comprised of the VERION Image Guided System and the ORA System with VerifEye.

In March 2015, LENSAR received 510k clearance from the FDA for its Streamline software package that introduced six application upgrades to the LENSAR Laser System, including wireless integration of the LENSAR laser and the Cassini Corneal Shape Analyzer (i-Optics), iris registration, and arcuate incision planning among others.

The wireless integration automatically brings the infrared image of the undilated eye captured preoperatively with the Cassini to the femtosecond laser for intraoperative guidance. Compatibility with the OPD-Scan III (Nidek) and other topographic and corneal analyzer systems is forthcoming.

The preoperative image is used with proprietary iris registration and landmark technology to automatically compensate for ocular cyclorotation, allowing for increased accuracy in the placement of laser-created arcuate incisions and of corneal intrastromal marks for toric IOL alignment.

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The new software for the laser also brings capability for automation of nomograms for arcuate incisions that apply the diagnostic information acquired with the Cassini to the surgeon’s preferred treatment parameters for incision location, depth, and length. The topographic information can also be used to guide placement of the main and sideport incisions.

In addition, the LENSAR laser integrates with the TrueVision Refractive Cataract Toolset surgical guidance system so that surgeons can make a final check of toric IOL positioning and correction of astigmatism.

Bausch + Lomb is currently developing a system (Spectrus) for image-guided surgery that will link preoperative topography to its femtosecond laser (Victus).

Also in 2015, Abbott Medical Optics unveiled Steep Meridian Registration Technology (SMRT) for its Catalys Precision Laser System that makes astigmatic correction easier and more accurate.

“SMRT is an integrated method for measuring and displaying the steep meridian of astigmatism,” Dr. Packer said. “The information is then used to guide laser-placed arcuate incisions or toric IOL alignment incisions.”

SMRT captures keratometry intraoperatively with use of a separate accessory that is placed into the patient interface instead of the suction ring. It thereby not only eliminates the need for and inherent drawbacks of ink markings, but it also obviates the need for another device to measure astigmatism.

Image-guided lens fragmentation

Image-guided lens fragmentation

The Streamline software for the LENSAR laser also introduces cataract density imaging and density-based customized fragmentation patterns. With the patient under the laser, the LENSAR imaging system grades cataract density and then suggests a fragmentation pattern based on that determination. Surgeons can then accept the treatment or select a pattern of their own.

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“It has been known for some time that cataract nuclear density could be graded based on a Scheimpflug imaging, and there have been several publications, the first by Don Nixon in 2010, showing correlations between the image-based cataract grade and the total phacoemulsification energy or effective phaco time needed to remove the cataract,” Dr. Packer said “The new software on the LENSAR applying this principle increases efficiency in the OR because the surgeon does not have to think about how the cataract looked at the slit-lamp and then choose the fragmentation pattern based on the preoperative assessment.”

Optimizing intraoperative aberrometry

Samuel Masket, MD, clinical professor of ophthalmology, Jules Stein Eye Institute, University of California Los Angeles, observed that interest in intraoperative aberrometry guidance is increasing among cataract surgeons as they are faced with a growing population of patients from the babyboomer generation who are expecting refractive and vision outcomes matching those achieved with LASIK.

He noted that refractive accuracy in cases performed with the ORA aberrometry system has improved thanks to various enhancements to the platform. However, reliability of the measurements still depends on the surgeon’s attention to technique.

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Raising and maintaining IOP to an appropriate level is critical for attaining an accurate aphakic measurement, and it is achieved by filling the eye with balanced salt solution (BSS) or an ophthalmic viscosurgical device (OVD).

Dr. Masket noted that surgeons using the ORA system to determine IOL spherical power intraoperatively in the aphakic eye should be aware of the findings from a study he conducted showing how the reading can vary depending on the choice of material used to inflate the eye. A manuscript describing the research is currently in editorial review for the Journal of Cataract and Refractive Surgery.

The study looked at aberrometry readings obtained after filling the eye with BSS or one of six OVDs-sodium hyaluronate 1.0%, (ProVisc, Alcon Laboratories); sodium hyaluronate 1.2% (Amvisc, Bausch + Lomb); sodium hyaluronate 1% (Healon, Abbott Medical Optics); sodium chondroitin sulfate 4%/sodium hyaluronate 1.7% (DisCoVisc, Alcon Laboratories); sodium hyaluronate 1.6% (Amvisc Plus, Bausch + Lomb); and sodium hyaluronate 1.4% (Healon GV, Abbott Medical Optics).

Results

The results showed the readings obtained using BSS were not significantly different than those using any of the low molecular weight sodium hyaluronate products (ProVisc, Amvisc, and Healon). There was a borderline difference between the readings with BSS and those obtained using the higher molecular weight sodium hylauronate product (Healon GV), whereas the readings obtained with BSS were significantly different compared with those obtained using DisCoVisc or Amvisc Plus.

“With use of the IOL power suggested by the aberrometer when the eye was filled with DisCoVisc or Amvisc Plus, a patient would wind up with about 0.5 D of hyperopia, and there was a trend toward a hyperopic outcome if the power suggested in an eye filled with Healon GV was used,” Dr. Masket said. “The explanation for the findings lies in the difference in index of refraction of the various OVDs compared with BSS.”

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Dr. Masket observed that many surgeons using the intraoperative aberrometer prefer to fill the eye with OVD rather than BSS. Stromal hydration to insure watertightness of the incision is critical using BSS, which can otherwise leak out. However, if not done carefully, stromal hydration can distort the cornea.

“As the use of OVD for inflating the eye is becoming more popular, we did this study to give surgeons certainty about whether or not it introduces the potential for erroneous measurements,” Dr. Masket said. “We think we have sorted out the answer, and our advice is that surgeons use either BSS with limited wound hydration or a lower molecular weight hyaluronic acid OVD.”

Samuel Masket, MD

E: [email protected]

Dr. Masket is a consultant for Alcon Laboratories, MST Surgical, Ocular Therapeutix, PowerVision, VisionCare Ophthalmic Technologies, and WaveTec Vision; an investor for Ocular Therapeutix; and earns royalties from Morcher GmbH and Haag-Streit AG.

Mark Packer, MD

E: [email protected]

Dr. Packer is a consultant to Advanced Vision Science, Aerie Pharmaceuticals, Alcon Laboratories, Bausch + Lomb, International Biomedical Devices, i-Optics, LENSAR, Oculeve, Promedica International, Rayner Intraocular Lenses, Refocus Group, SOLX, STAAR Surgical, Transcend Medical, and VisionCare Ophthalmic Technologies. He holds equity in Eyenovia, Iantech, International Biomedical Devices, LENSAR, mTuitive, Refocus Group, Transcend Medical, TrueVision Systems, and WaveTec Vision Systems.