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Intraoperative aberrometry measurements in cataract surgery spur debate
Thomas S. Boland, MD, and Kenneth A. Beckman, MD, FACS, discuss the pros and cons of intraoperative measurements.
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Welcome to CEDARS-ASPENS Debates, a monthly feature in Ocular Surgery News.
CEDARS (Cornea, External Disease, and Refractive Surgery Society) and ASPENS (American Society of Progressive Enterprising Surgeons) is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.
Intraoperative aberrometry measurements have become much more utilized during cataract surgery in recent years for obvious reasons. Even when surgeons have access to this technology, there is still no consensus as to how to interpret the data. While many surgeons put all of their trust in these measurements, others may feel that the preoperative calculations are more reliable. This month, Dr. Tom Boland and I discuss the merits and pitfalls of using intraoperative aberrometry with routine cataract surgery. We hope you enjoy the discussion.
Kenneth A. Beckman, MD, FACS OSN CEDARS-ASPENS Debates Editor
ORA technology provides improved surgical outcomes
Intraoperative aberrometry measurements in cataract surgery have become more prevalent in recent years, but I know that there are many surgeons still unsure of the role the technology can play in their practice. Its usefulness in post-refractive surgery eyes has been demonstrated without question, but what is its role in more typical eyes? The longer that I use the technology (ORA with VerifEye, Alcon), the more frequent my use, and the better my surgical outcomes have become.
We routinely do multiple measurements for IOL calculations, with each patient having axial length measured by immersion ultrasound, IOLMaster (Carl Zeiss Meditec) and/or Lenstar (Haag-Streit), and keratometry values measured in a variety of ways, from manual keratometry, autorefractor, Pentacam (Oculus), Orbscan (Bausch + Lomb), IOLMaster, Lenstar, Cassini (i-Optics) or other automated topographer. The resulting stew of numbers can be enough to make your head spin. In most cases, there is good correlation of data, but occasionally there is wide disagreement in measurement. In the absence of intraoperative aberrometry, how do you make your IOL choice? We all have our favorite instruments and favorite formulas, but eventually you have to make a choice; aberrometry can eliminate the confusion, and I routinely use it as a “tiebreaker” in these cases of conflicting data. This comes in handy especially with your more discriminating or “fussy” patients.
In dense cataracts, or eyes with significant posterior subcapsular cataract, it can be difficult or even impossible to capture measurements with optical biometry, and even ultrasound can be inaccurate if the cataract is dense enough to interfere with fixation. By utilizing aphakic intraoperative measurements, you can be sure of the precision and make a much more accurate IOL selection.
Premium IOLs are another area in which the ORA can be invaluable. Since adopting the use of this technology, our enhancement rate after multifocal or toric IOL placement has plummeted. With multifocal IOLs, if you are not reducing postoperative refractive error to less than 0.5 D on a regular basis, then you are going to have many disappointed patients and a higher than necessary enhancement rate. The use of intraoperative aberrometry can reliably get you to this level of refractive error. With toric IOLs, I now use the ORA on every case to verify the power of the IOL, as well as the cylinder power of the IOL, and then to verify the proper axis of placement. In many cases, this can completely alleviate the need for any preoperative marking of the eye because the intraoperative measurements are more reliable and can account for posterior corneal changes.
As femtosecond laser-assisted surgery becomes more prevalent, another area in which the ORA is helpful is with management of astigmatism-correcting incisions. I program the laser to make astigmatic keratotomy incisions, but I do not routinely open the incisions at the beginning of the case. At the completion of the case, once the IOL has been inserted and the eye has been pressurized, the real-time streaming refractive data from the VerifEye system can tell you how much residual astigmatism you have and help you determine if your incisions need to be opened or potentially extended. This adds almost no time to the procedure and can save you much chair time in the clinic later.
The bottom line is that as our technologies advance and patient expectations continue to rise, I find this to be an indispensable tool. Aside from the indications discussed above, I face an ever increasing number of post-refractive surgery patients presenting for cataract surgery and have seen my use of intraoperative measurements steadily climb to the point at which some weeks more than 50% of my cases involve the ORA. Going forward, I could not see myself going backward to the days when we did not use it. Once you try it, I am sure you will agree.
- For more information:
- Thomas S. Boland, MD, can be reached at Northeastern Eye Institute, 200 Mifflin Ave., Scranton, PA 18503; email: tsboland@aol.com.
Disclosure: Boland reports no relevant financial disclosures.
Why I do not use intraoperative aberrometry
As the precision with cataract surgery continues to improve, the demand from patients for perfection continues to rise. With the increased use of premium IOLs, the importance of this precision becomes even greater. Surgeons now face the dilemma of how to truly select the proper IOL power, and for toric lenses, the proper axis of placement.
In recent years, there has been a tremendous amount of attention paid to optimization of the ocular surface before cataract surgery. There are numerous reasons why this has garnered so much attention. Obviously, cleaning up the ocular surface can decrease the risk of perioperative infections. In addition, improving the surface can decrease postoperative aberrations, which may alter the final visual outcome. The third reason is to allow for accurate corneal measurements and therefore accurate IOL calculations. Like many surgeons, I spend a significant amount of time focusing on the ocular surface before surgery. I typically perform a detailed dry eye evaluation, including checking the lid margins for meibomian secretion quality, as well as a tear film assessment with osmolarity testing and corneal staining.
For the preoperative measurements, I obtain multiple keratometry readings. I use the IOLMaster, manual keratometry and corneal topography. If these readings do not correspond, or if the mires are irregular, I treat the ocular surface and bring the patient back for repeat measurements. Occasionally, this may require multiple visits, and the surgery may need to be delayed for weeks or longer, until I am satisfied with the surface and the measurements. Once the surface has been optimized, I carefully select the proper lens based on what is now a healthy surface.
This is the point at which the conflict begins. Many surgeons prefer to use intraoperative aberrometry to determine which IOL to use and on which axis to place the IOL if it is a toric lens. This has caused me some concern. I just spent weeks improving the ocular surface to obtain corneal measurements from a pristine eye. Now, I am in the OR and have to decide if I trust these measurements. If I use the ORA, I am getting real-time measurements of the eye and theoretically the most accurate information to aid my IOL selection. There are several problems that I must deal with.
The eye has a speculum in place. This obviously can distort the surface. How much do I trust the measurements with the speculum in place? There is also an open corneal incision. Even with hydration, the wound is still not in its final state, and therefore the corneal curvature may be altered. Also, the patient has had the eye open for several minutes, relying on balanced salt solution irrigation to keep the epithelial cells intact. Was the irrigation consistent? Are the epithelial cells in their healthiest state? How were they affected by the numerous topical anesthetic drops the patient may have received before or during the case? How does the composition of the anterior chamber fluid, with potentially both aqueous and viscoelastic in the eye, affect the measurements? Does the fluid fill and optimal IOP affect the measurements? There are so many variables with each case. I do not know which variables may be affecting the situation and which are not.
Once the measurements are taken, and the IOL power is identified, the surgeon has a decision to make. What do I do if the new calculation does not agree with the preop measurements? Do I use the preop measurements? Do I ignore the preop measurements and use the ORA measurements? Do I hedge my bet and split the difference? I really do not know what is best. I do know that I spent an extensive amount of time and effort to optimize the surface and therefore obtain measurements from a surface that is likely as healthy as possible and hopefully will remain in this state postoperatively. I just am not convinced that the measurements I may get intraoperatively, with all of the variables described above, would be more accurate than the measurements I got preoperatively. Certainly there are cases in which the ORA adds tremendous value, such as in the case of post-refractive patients, in whom the keratometry and topography readings may not be accurate. Also, when the ORA measurements do agree with the preoperative measurements, I would have a significant amount of comfort that my measurements are indeed correct. But if they disagree, I am at a loss.
I realize that intraoperative aberrometry is the wave of the future. The technology will continue to improve and is actually already quite impressive. Until I really know how to interpret the information and am comfortable relying on those measurements, I will likely stick with my tried-and-true measurements that I bring with me to the OR.
- For more information:
- Kenneth A. Beckman, MD, FACS, can be reached at Comprehensive Eye Care of Central Ohio, 450 Alkyre Run Drive, Suite 100, Westerville, OH 43082; email: kenbeckman22@aol.com.
Disclosure: Beckman reports no relevant financial disclosures.