May 2019


Review of “Correcting astigmatism at the time of cataract surgery: comparing results with toric intraocular lenses and corneal relaxing incisions planned with an image guidance system and intraoperative aberrometer versus manual planning and surgery”

by Brett Gudgel, MD, Valerie Lobodiak, MD, Alice Kim, MD, Finny John, MD, Douglas Jin, MD, Shehzad Batliwala, MD, Gerta Mane, MD, Dean McGee Eye Institute residents, David Jackson, MD, faculty preceptor

R. Michael Siatkowski, MD
Residency program director
Dean McGee Eye Institute

Dean McGee Eye Institute residents, from left: Alice Kim, MD, Gerta Mane, MD, Douglas Jin, MD, Finny John, MD, Brett Gudgel, MD, Shehzad Batliwala, MD, and Valerie Lobodiak, MD
Source: Dean McGee Eye Institute

Do the outcomes justify the expense of using intraoperative aberrometry and digital guidance for toric IOLs? I invited the Dean McGee residents to review this study in the current JCRS edition.

—David F. Chang, MD,
EyeWorld Journal
Club Editor

Outcomes in cataract surgery continue to improve and patient expectations continue to increase. An abundance of evolving technology and surgical techniques allow today’s cataract surgeon to optimize and improve surgical outcomes. However, cataract surgeons must be thoughtful when considering new technology, as not every new innovation translates to improved patient outcome. As these technologies increase in number, ongoing research attempts to quantify the actual benefit these technologies have on patient care.
Alongside advancements in cataract surgical technique have been improvements in intraocular lens technology that aim to correct both spherical and astigmatic errors. Residual astigmatism is an important cause for not achieving postoperative emmetropia. Currently multiple options exist for astigmatic correction at the time of cataract surgery including corneal astigmatic incisions and toric intraocular lenses. There are also many variables that affect the accuracy of astigmatic correction, including the method used to measure astigmatism, incision location, lens selection and alignment, and the method of surgical guidance/correction. Ideal case selection is critical in the preoperative phase in order to ensure patient satisfaction and optimal outcomes.
In their recent article, Solomon et al. set out to analyze multiple variables involved in astigmatism correction to help provide insight into the best techniques and treatments. Specifically, they designed a randomized, contralateral eye study aimed at comparing postoperative results with toric intraocular lenses and corneal astigmatic incisions (CAI) planned with image guidance utilizing intraoperative aberrometry and femtosecond incisions, capsulotomy, and lens fragmentation versus manual planning and surgery.
Solomon et al. primarily wanted to see if laser-assisted phacoemulsification utilizing image guided surgical planning and intraoperative aberrometry yielded any improvement in outcomes when compared to the surgeon’s standard of care in the absence of these technologies. Thirty-nine patients (78 eyes) underwent bilateral cataract surgery with astigmatism correction. They randomized the patient’s initial eye into either Group A or Group B, with the second eye defaulting to the other group. Eyes in Group A were treated with the surgeon’s standard of care, which included the Barrett Universal II formula for sphere power selection, IOLMaster (Carl Zeiss Meditec) and LENSTAR (Haag-Streit) for biometry, LENSTAR for keratometry, the Barrett Toric Calculator for toric IOL selection, and the Johnson & Johnson Vision LRI calculator for LRI planning. Blue ink marks were used for toric IOL axis guidance and LRIs were made manually. The cataract surgery was done manually as well. Group B eyes underwent laser-assisted phacoemulsification, preoperative planning with the VERION Image Guided System and the VERION planner (Alcon), which determined spherical power selection (using optimized Holladay 2), toric IOL power selection and CAI planning. The LENSTAR was used to determine axial length and AC depth. VERION digital markers were used for axis placement and ORA intraoperative aberrometry (Alcon) was used to evaluate need for spherical or toric IOL power/orientation modification. The cataract was removed using femtosecond laser-assisted phacoemulsification (primary incision, capsulorhexis, and lens fragmentation), and the femtosecond laser was used to create CAIs as well. In each group patient astigmatism was corrected with either toric IOLs or CAIs depending on the degree of astigmatism, and the same method for astigmatic correction (IOL vs. CAI) was used in each of the patient’s eyes. Each patient had one eye randomly assigned to each surgical group. Multiple measurements were recorded preoperatively including uncorrected visual acuity, best corrected visual acuity, manifest refraction, and keratometry. The same measurements were recorded postoperatively with the addition of toric lens rotation, which was determined by a single examiner at the slit lamp.
Eventually 38 eyes were treated with toric IOLs, and 40 eyes were treated with CAIs. The authors found a statistically significant difference in the mean residual cylinder when comparing toric IOLs to CAIs, with toric IOLs having nearly 0.25 D less residual cylinder on average than CAIs. Interestingly, the study found no statistically significant difference in residual astigmatism by surgical group. Additionally, there was no statistically significant difference in mean spherical equivalent refraction, uncorrected visual acuity or best corrected visual acuity by treatment (toric IOL vs. CAI). When analyzing postoperative toric IOL rotation, they found that 11% (four eyes) were greater than 10 degrees away from intended axis. These four eyes were distributed evenly between the two surgical groups, with two in the standard group and two in the image guided system/intraoperative aberrometry group. Also, all four of the rotated lenses were T3 (low cylinder) torics. Finally, while comparing VERION keratometry to LENSTAR, they found the magnitude of the astigmatism measured to be equal, but the mean keratometric value was 0.16 D higher in the VERION system.
The finding of this study is that femtosecond laser-assisted cataract surgery utilizing the VERION Image Guided System and the VERION planner in combination with intraoperative aberrometry did not improve astigmatic outcomes when compared to manually created corneal astigmatic incisions and standard cataract surgery utilizing modern formulas to determine spherical and net cylindrical correction. Though it is tempting to think that technologically advanced tools should automatically lead to improved astigmatic outcomes, this study highlights that this is not always the case. This study also confirmed prior reports of toric IOLs being a more accurate way to correct astigmatism than CAIs.
The contralateral eye and randomized nature of the study design where subjects are used as their own controls is ideal. Correcting smaller amounts of astigmatism with arcuate incisions and higher amounts with toric intraocular lenses is common practice and enhances the applicability of the study. The number of patients included in the study, however, is relatively low, possibly leading to an inadequate power to establish a statistically significant difference in the residual astigmatism measured between the surgical groups. The article needs to mention how the surgeon marks his manual LRI and toric IOL patients preoperatively when not using VERION and intraoperative aberrometry. The VERION Image Guided System and intraoperative aberrometry account for cyclorotation. There is also a lack of information on how intraoperative aberrometry was used to change management. It is unclear if any changes were made in IOL power selection or axis alignment based on intraoperative aberrometry recommendations. Additional studies that document the modifications suggested by intraoperative aberrometry and analyze the correlation between intraoperative aberrometry and VERION recommendations would be beneficial. Lastly, the article describes the use of different formulas between the groups (Barrett Universal II vs. Holladay 2), which may also affect the outcomes.
Overall, we find this to be a fascinating study that sheds light on multiple facets of modern cataract surgery. In this study, the results of precise manual astigmatic axis identification and placement of a toric intraocular lens or corneal astigmatic incision using modern formulas to identify correct spherical and net astigmatic correction cannot be distinguished from femtosecond laser-assisted cataract surgery with preoperative digital astigmatic axis identification and intraoperative guided astigmatic correction. We agree with the authors that additional studies with more patients are needed to further investigate and validate the conclusions proposed by this study. We appreciate the authors’ dedication to critically evaluating the available technologies, and we hope that the results will guide both providers and industry to continue to strive for the best possible patient outcomes.

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In memoriam

Arnold Robert Bellows, MD
May 14, 1937–March 15, 2019

Clarence “Bill” Billingsley, MD
Dec. 30, 1932–March 15, 2019

Robert Boomer, MD
April 16, 1923–March 3, 2019

Robert Lewis Copeland, MD
Feb. 5, 1923–March 5, 2019

Michael Kottler, MD
Sept. 24, 1940–March 9, 2019

Richard “Tony” Levacy, MD
July 2, 1945–March 6, 2019

Merrick Wyble, MD
Aug. 9, 1933–March 13, 2019

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Review of “Correcting astigmatism at the time of cataract surgery: comparing results with toric intraocular lenses and corneal relaxing incisions planned with an image guidance system and intraoperative aberrometer versus manual planning and surgery” Review of “Correcting astigmatism at the time of cataract surgery: comparing results with toric intraocular
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