Manual relaxing incision versus femtosecond laser-assisted arcuate keratotomy. A systematic review

Author: González-Cruces T, Cano-Ortiz A, Sánchez-González MC, Sánchez-González JM.

Geographical coverage: Not reported

Sector: Cataract surgery

Sub-sector: Treatment comparison

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Cataract surgery is performed chiefly to improve distance visual acuity, yet residual corneal astigmatism can limit postoperative satisfaction. About 1 dioptre of corneal astigmatism is typical in age-related cataract, and values above 0.50 D should be addressed in surgical planning. Correction options include toric IOLs, excimer-laser surgery and corneal incisions made either manually or with femtosecond-laser assistance. Manual techniques—limbal relaxing incisions (LRI), opposite clear-corneal incisions (OCCI) and arcuate keratotomy (AK)—are widely accepted for astigmatism up to 2–3 D. Femtosecond-laser arcuate keratotomy (FLAK) permits precise intrastromal cuts with lower complication risk, but involves higher capital cost. A careful appraisal of the cost–benefit ratio and refractive predictability of laser-assisted versus manual methods remains necessary.

Objective:

To compare the correction of corneal astigmatism achieved with manual relaxing incisions and with femtosecond-laser-assisted arcuate keratotomy during cataract surgery.

Main findings:

Forty case-series studies published between 2010 and 2021 were included in the review: 1,025 eyes (946 patients) in the manual-incision group and 1 905 eyes (1 483 patients) in the FLAK group.

• Visual outcomes:
  • Mean uncorrected distance visual acuity (UDVA) post-operatively was 0.19 ± 0.12 logMAR for manual incisions and 0.15 ± 0.05 logMAR for FLAK (non-significant difference, p = 0.39).
  • The correction index (CI) indicated mild under-correction in both groups: 0.77 ± 0.18 (manual) vs 0.79 ± 0.17 (FLAK; p = 0.70).
• Astigmatic reduction:
  • Manual relaxing incisions (MRI): keratometric astigmatism fell from 1.86 ± 0.53 D to 1.04 ± 0.48 D; refractive astigmatism from 1.96 ± 0.62 D to 0.98 ± 0.36 D.
  • FLAK: keratometric astigmatism decreased from 1.16 ± 0.26 D to 0.64 ± 0.21 D; refractive astigmatism from 1.41 ± 0.17 D to 0.57 ± 0.22 D.
  • All reductions were statistically significant (p < 0.01).
• Safety: Both techniques were reported as safe, with no serious adverse events attributed directly to the incisions.

Overall, authors concluded that manual and femtosecond-assisted arcuate keratotomies are similarly effective and safe for correcting mild-to-moderate corneal astigmatism during cataract surgery, though both tend towards slight under-correction.

Methodology:

PubMed, Web of Science and Scopus were searched for English-language human studies published from January 2010 to 30 March 2021. Prospective, retrospective and case-series designs evaluating manual or femtosecond-laser-assisted corneal relaxing incisions performed during cataract surgery in otherwise healthy eyes were eligible. One reviewer screened titles and abstracts; two reviewers extracted data, removed duplicates, assigned studies to intervention groups and independently assessed risk of bias with the NHLBI Quality Assessment Tool for Case Series. Disagreements were resolved by a third reviewer. Findings were synthesised narratively.

Applicability / external validity:

Language restriction to English, variability in surgical parameters and short follow-up periods limit external validity. Randomised controlled trials with standardised protocols and longer follow-up are required to establish comparative superiority and cost-effectiveness.

Geographic focus:

No geographical limits were applied, but the locations of included studies were not reported.

Summary of quality assessment:

Overall confidence in the review’s conclusions is low. Searches covered three databases and inclusion criteria were explicit, with dual-reviewer data extraction and quality appraisal. However, only one reviewer performed initial screening, an excluded-studies list was not provided, grey literature was not searched, and all included studies were uncontrolled case series.