Optimizing FLACS Parameters Can Lower Surgically-Induced Astigmatism Incidence

Optimized parameters in femtosecond laser-assisted cataract surgery (FLACS) can lead to low surgically-induced astigmatism (SIA), solid predictability, and effective self-sealing, according to a case series published in Clinical Ophthalmology. 

Researchers examined records of patients who presented a healthy cornea, preoperative astigmatism of 1.0 diopter (D) or less, and experienced uneventful FLACS at a private ophthalmology hospital in Brazil from May 2018 to December 2018. The study analyzed SIA and incision opening success rates.

The analysis that concentrated on opening success included a cohort of 79 patients (156 eyes; mean age, 65.0±9.65 years). In this group, optimal incision opening occurred for 87.7% of eyes, with average time to opening 7.50±6.83 seconds, ranging from 2 seconds to 40 seconds. Among 4 subgroups categorized by primary incision site, success meaningfully differed by position (P =.012), including the following:

• Temporal; between 150° and 210° right eye, 330° to 30° left eye, success rate 98.36%
• Nasal; between 30° and 120° right, 120° to 150° left, success rate 90.0%
• Oblique; between 120° and 150° right, 30° to 60° left, success rate 81.5%
• Superior; between 60° and 120° in each eye, success rate 75.0%

Two incision sizes exhibited differences in success rate; 93.48% with 2.4 mm, and 85.45% with 2.8 mm. Further, a logistic regression model to adjust for eye laterality, and between the two surgeons revealed no significant differences.

The analysis examining SIA involved a cohort of 61 patients (101 eyes; mean age, 66.49±8.11 years) who met specified criteria. Total mean SIA resulted at 0.44±0.33 D. In general, the SIA centroid was gauged at 0.11, including centroid for 2.4 mm incision of 0.12, and those with 2.8 mm at 0.1. Size and axis had no statistically significant impact regarding SIA, according to the analysis.

“Although there appears to be no advantage in terms of corneal astigmatism and higher-order aberrations, CCIs in FLACS, particularly the multiplanar configuration, are better designed and more reproducible than manual techniques,” the researchers report. “In the present study, we found that CCIs preserved the anatomy of tri-planar incisions, exactly as planned intraoperatively, even 3 months after the procedure.”

Researchers note femtosecond’s plane configuration allows for depth control. The third plane may promote good self-sealing and uses corneal strength to support the incision; the second points to the anterior chamber; and the first plane can be precisely set — 60% anterior plane depth was chosen. Investigators explain that femtosecond technique is like a “Velcro zipper.” Since the incision needs to be very close to the limbus, surgeons avoided directing the laser into semi-opaque tissues in the perilimbal region by employing a 70° forward angle.

Prior studies proposed that a reverse side-cut angle toward the limbus from the cornea which then slants back to the eye’s center may seal better. In contrast, the current surgeons used a 70° angle and 60% depth, resulting in no endophthalmitis, leakage, or hypotony.

Limitations of this investigation included a retrospective design and potentially non-diverse sample. On the other hand, this is the first exploration of associations between time needed for incision opening and ideal wound construction.

Disclosures: This research was supported by Alcon Laboratories, Inc. Multiple study authors have declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.