Image-guided technologies enhance drive for cataract surgery perfection

The drive to perfection in cataract surgery is enhanced by intraoperative real-time appreciation of the status of individual patients.

Reviewed by Zaina N. Al-Mohtaseb, MD

Patient expectations for cataract surgery are at an all-time high. As a result, to reach excellent refractive outcomes, great emphasis is placed on the preoperative steps taken in preparation for cataract surgery, such as keratometry, biometry, and IOL power calculations. With technologic advances, that list has lengthened to include intraoperative considerations.

Newer technologies that provide intraoperative imaging are continuously improving to aid surgeons with toric IOL alignment, IOL centration, and wound and astigmatic keratotomy placement to lessen errors as much as possible, according to Zaina Al-Mohtaseb, MD.

“Greater importance is being placed specifically on capsulorhexis and IOL centration, astigmatic keratotomy placement, and toric IOL alignment with the introduction of presbyopia-correcting IOLs that include both a multifocal and a toric component,” said Dr. AlMohtaseb, assistant professor of ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston. “Their optimization is definitely important to get excellent refractive outcomes.”

The impact of alignment errors is great and demonstrates the need for precision, and the degree of alignment errors increases exponentially in the more complex commercially available lenses. If the alignment is off-axis by about 10°, the result is a 34% error, and when an IOL is off-axis by 30°, this results in an error of 100% with almost no effective astigmatic correction but a resultant change in the axis, she said.

Errors can occur in a few key areas when placing a toric IOL, i.e., in determining the initial reference axis when the eye is marked for example at the 3, 6, and 12 o’clock positions, when marking the axis intraoperatively, and then aligning the lens to that axis.

Image-guided technologies

Dr. Al-Mohtaseb provided a brief overview for some of the newer instrumentation technologies (including the Zeiss Callisto, Alcon Verion, and TrueVision) that aid in aligning toric IOLs with the goal of lessening potential errors. ZEISS CALLISTO. A reference image is acquired during routine biometry with the IOLMaster 700. This reference image is then viewed intraoperatively to center the capsulorhexis and multifocal IOLs, place incisions, and align toric IOLs.

She cited a study (Mayer et al. J Cataract Refract Surg. 2017;43:1281–1286) in which the accuracy and outcomes were compared between the Callisto (n = 28 eyes) and manual markings (n = 28 eyes). The study showed less degrees of postoperative IOL misalignment were in favor of Callisto digital marking, i.e., 2.0° for digital marking compared with 3.40° for manual marking, a difference that reached significance (p = 0.026).

Another finding was that the time required to perform IOL alignment was significantly shorter with the digital approach compared with manually, i.e., 37.2 seconds versus 59.4 seconds, respectively; p< 0.001). Titiyal et al. (Clinical Ophthalmology. 2018;12:747-753) compared toric IOL alignment assisted by image-guided technology (Callisto) vs. manual marking methods and its impact on visual quality and reported a significant (p = 0.003) difference with lower refractive cylinder postoperatively, –0.89 D versus –0.64 D, respectively.

The study also found less deviation from the target axis with the Callisto both on postoperative days 1 and 30 (p = 0.005 for both comparisons).

• Alcon Verion
  This system has a reference unit that obtains images preoperatively with a digital marker that captures the image. This image then is used intraoperative to aid in centration of the capsulorhexis and multifocal IOLs, incision placement, and IOL alignment. Elhofi and Helaly conducted a study (Medicine. 2015;94:1–4) in which they compared the Verion and manual marking capabilities for aligning toric IOLs. The results also pointed to the superiority of digital marking in the degrees of misalignment between the two methods (2.40° versus 4.33°, respectively).
  
  Hura and Osher (J Refract Surg. 2017;33:482– 7) compared the accuracy of the Callisto and the Verion for toric IOL alignment found that the two technologies, interestingly, were not interchangeable. “Both did not necessarily have the same axis, but neither system was superior,” she said.
   

• Truevision
  This system differs slightly from the previous two by offering toric IOL alignment with data integration with the preoperative data obtained from the Cassini, Pentacam, or Lenstar.
  
  The system obtains an image preoperatively that can then be used intraoperatively to account for cyclotorsion in real time using the overlay. When Dr. Al-Mohtaseb, Dougles D. Koch, MD, and colleagues at Baylor conducted a study in which they compared the manual markings with TrueVision, they found no significant difference between the two. (The three-dimensional, TrueVision digital imaging technology/visualization system with heads-up display is partnership with Alcon Laboratories and is being used in both retina and cataract surgeries [NGENUITY]).
   

• Ora System
  This platform differs from the other three systems in that it is an intraoperative wavefront aberrometer that can perform aphakic and pseudophakic refractions. One situation in which this technology is helpful is in cataract patients who have had previous refractive surgery, she said. A study by Ianchelev et al. (Ophthalmology. 2014;121:56– 60) found that ORA provided a significant improvement in predicting the lens power after a previous myopic refractive surgery. The technology also is helpful for toric IOL alignment.
  
  A study by Woodcock et al. (J Cataract Refract Surg. 2016;42:8107–825) found that more patients had less than 0.5 D of astigmatism when the ORA was used compared with standard preoperative biometry, she recounted.

Disclosures:

Zaina N. Al-Mohtaseb, MD
E: zaina1225@gmail.com
This article was adapted from Dr. Al-Mohtaseb’s presentation during Cornea Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology. Dr. Al-Mohtaseb is a consultant to Alcon Laboratories, Bausch + Lomb, Carl Zeiss Meditec, and Johnson & Johnson.