Transitioning from mechanical microkeratome to femtosecond laser flap creation: Visual outcomes of an experienced and a novice LASIK surgeon

The impact of learning curve on flap thickness outcome in femtosecond laser assisted LASIK performed with new LenSx dual platform

Purpose

To evaluate the effect of learning curve on flap thickness (FT) outcome in femtosecond (FS) laser-assisted laser in situ keratomileusis (LASIK) operation for myopia performed with recently introduced LenSx dual platform using curved applanation cone.

Methods

Seventy eyes of 36 patients with myopia or myopic astigmatism operated with FS laser-assisted LASIK with recently introduced LenSx dual platform were evaluated in this retrospective study. Operations were divided into two groups: first 20 operations (20 eyes of 10 patients) and next 50 operations (50 eyes of 26 patients). Data on patient demographics, preoperative and postoperative keratometric and aberrometric parameters, and FT related outcome, including mean central FT, mean total FT, intra-FT range, and FT homogeneity were compared in study groups.

Results

Except for significantly lower preoperative steepest keratometry values in the next 50 operations versus first 20 operations (p = 0.033), no significant difference was noted between study groups in terms of preoperative and postoperative parameters. When compared to first 20 operations, next 50 operations were associated with significantly higher values for mean central FT (median, 123 μm vs. 114 μm; p = 0.007) and mean total FT (median, 123 μm vs. 113 μm; p = 0.015), whereas significantly lower intra-FT range (median, 4.0 μm vs. 4.5 μm; p = 0.003).

Conclusions

In conclusion, our findings related to FS laser-assisted LASIK surgery for myopia with new LenSx dual platform using curved applanation cone revealed significant impact of learning curve on the corneal FT outcome in terms of closer FT to the intended value and lower intra-flap range.

Outcomes of Resident-Performed FS-LASIK for Myopia and Myopic Astigmatism

PURPOSE

To evaluate the outcomes of resident-performed femtosecond laser-assisted in situ keratomileusis (FS-LASIK).

METHODS

Records of 138 eyes of 69 patients treated by residents for myopia or myopic astigmatism between March 2018 and June 2020 were reviewed. All preoperative visits, procedures, and postoperative visits were supervised by attending physicians. Follow-up examinations were performed 1 day and 1 month postoperatively. Complications and enhancements were noted. Outcome measures included postoperative uncorrected distance visual acuity (UDVA), refractive accuracy, and complications.

RESULTS

Eighteen residents performed FS-LASIK on a median of 8 eyes (interquartile range: 1.75). Fifty-nine patients (118 eyes) returned for a 1-month postoperative examination. UDVA was 20/40 or better in 117 eyes (99%) and 20/20 or better in 108 eyes (92%). The mean preoperative spherical equivalent (SE) refractive error was -4.01 ± 1.82 diopters (D) in 138 eyes, decreasing to -0.12 ± 0.35 D at 1 month after surgery in the 102 eyes that were refracted. The SE was ±1.00 D in 100 eyes (98%) and ±0.50 D in 94 eyes (93%). The CDVA change was within one line in 100% of eyes. Intraoperative complications occurred in 5 eyes (3.62%), enhancements were performed in 3 eyes (2.17%), and postoperative complications developed in 3 eyes (2.17%).

CONCLUSIONS

Resident-performed FS-LASIK is relatively safe and effective in comparison to published U.S. Food and Drug Administration premarket approval studies. Early resident experience performing LASIK can improve the training of ophthalmic surgeons while simultaneously increasing patient access to laser vision correction. [J Refract Surg. 2021;37(8):545-551.].

Incidence and Outcomes of Optical Zone Enlargement and Recentration After Previous Myopic LASIK by Topography-Guided Custom Ablation

PURPOSE

To report the incidence, visual and refractive outcomes, optical zone enlargement, and recentration using topography-guided CRS-Master TOSCA II software with the MEL 80 excimer laser (Carl Zeiss Meditec AG, Jena, Germany) after primary myopic laser refractive surgery.

METHODS

Retrospective analysis of 73 eyes (40 patients) with complaints of night vision disturbances due to either a decentration or small optical zone following a primary myopic laser refractive surgery procedure using the MEL 80 laser. Multiple ATLAS topography scans were imported into the CRS-Master software for topography-guided ablation planning. The topography-guided re-treatment procedure was performed as either a LASIK flap lift, a new LASIK flap, a side cut only, or photorefractive keratectomy. Axial curvature maps were analyzed using a fixed grid and set of concentric circles superimposed to measure the topographic optical zone diameter and centration. Follow-up was 12 months.

RESULTS

The incidence of use in the population of myopic treatments during the study period was 0.79% (73 of 9,249). The optical zone diameter was increased by 11% from a mean of 5.65 to 6.32 mm, with a maximum change of 2 mm in one case. Topographic decentration was reduced by 64% from a mean of 0.58 to 0.21 mm. There was a 44% reduction in spherical aberration, 53% reduction in coma, and 39% reduction in total higher order aberrations. A subjective improvement in night vision symptoms was reported by 93%. Regarding efficacy, 82% of eyes reached 20/20 and 100% reached 20/32 (preoperative CDVA was 20/20 or better in 90%). Regarding safety, no eyes lost two lines of CDVA and 27% gained one line. Regarding predictability, 71% of re-treatments were within ±0.50 diopters.

CONCLUSIONS

Topography-guided ablation was effective in enlarging the optical zone, recentering the optical zone, and reducing higher order aberrations. Topography-guided custom ablation appears to be an effective method for re-treatment procedures of symptomatic patients after myopic LASIK. [J Refract Surg. 2018;34(2):121-130.].

Visumax femtolasik versus Moria M2 microkeratome in mild to moderate myopia: efficacy, safety, predictability, aberrometric changes and flap thickness predictability

Introduction

This is an interventional prospective clinical study which was conducted to evaluate the efficacy, safety, predictability, ocular aberrations, and flap thickness predictability of Visumax femtosecond laser (FSL) compared to Moria M2 microkeratome (MK) in mild to moderate myopia.

Methods

This study included 60 eyes who were divided into two groups. Thirty eyes in group (I) in which the flap was created with Visumax FSL, while in group II (30 eyes) the Moria M2 MK was used. Keratometric, refractive, and aberrometric measurements were compared preoperatively and 3 months postoperatively. The intraoperative subtraction pachymetry (the SP 100 Handy pachymeter (Tomey, Nagoya, Japan) was used for preoperative pachymetry and flap thickness measurement.

Results

No significant difference was found between the two groups in regards to postoperative manifest sphere, spherical equivalent, astigmatism, safety indices nor ocular aberrations. Twenty six eyes (86.6%) in group I and 23 eyes in group II (76.6%) were within ±0.5D of the intended correction and 23 eyes (76.6%) in group I and 15 eyes in group II (50%) were within ±0.25D of the intended correction. In group I, the mean postoperative actual flap thickness was 100.12 ± 16.1 μm (81 to 122 μm), while in group II, it was 104.6 ± 20.1 μm (62 to 155 μm). The difference was statistically significant (p = 0.001).

Conclusions

Both Visumax and Moria M2 MK are safe and effective in treating myopia with no statistically significant difference in induction of ocular aberrations but with potential advantage for Visumax regarding predictability. More accurate flap thickness is achieved with Visumax femtolasik.

Trial registration

This study was retrospectively registered on 19/6/2017. Trial registration number NCT03193411, clinicalTrials.gov.

Opaque Bubble Layer Risk Factors in Femtosecond Laser-assisted LASIK

PURPOSE

To determine the characteristics and risk factors for occurrence of opaque bubble layer (OBL) during femtosecond laser-assisted flap creation for LASIK.

METHODS

One hundred ninety-eight eyes of 102 consecutive patients who underwent LASIK flap creation performed with the Alcon WaveLight FS200 laser (Alcon Laboratories, Inc., Fort Worth, TX) were retrospectively analyzed in a cohort study. Preoperative manifest refraction, corneal keratometry, central corneal thickness, white-to-white corneal diameter, corneal hysteresis, corneal resistance factor, and programmed flaps parameters were collected. Digital images automatically recorded after flap creation were analyzed to measure OBL areas. Correlation tests were performed between preoperative corneal parameters and OBL areas.

RESULTS

The incidence rate of OBL was 48% (103 eyes). The mean OBL area as a percentage of the corneal flap area in the OBL group was 4.25% ± 7.16% (range: 0% to 32.9%). The central corneal thickness, corneal resistance factor, and corneal hysteresis were significantly positively correlated with the OBL area (r = 0.242, P = .001; r = 0.254, P = .028; and r = 0.351, P < .0001, respectively). Corneal hysteresis and OBL area were positively correlated, independently of the central corneal thickness and other confounder factors with standardized coefficient (r = 0.353 ± 0.227, P = .002).

CONCLUSIONS

This study confirms the already known OBL risk factors with a larger cohort and suggests for the first time that an elevated corneal hysteresis is an independent predictive risk for OBL occurrence.

Femtosecond laser versus mechanical microkeratome-assisted flap creation for LASIK: a prospective, randomized, paired-eye study

Purpose

To compare a femtosecond laser with a microkeratome for flap creation during laser in situ keratomileusis (LASIK) in terms of flap thickness predictability and visual outcomes.

Patients and methods

This was a prospective, randomized, masked, paired-eye study. Forty-four patients (34 females) who received bilateral LASIK were included. Patients were stratified by ocular dominance, and they then underwent randomization of flap creation using the femtosecond laser on one eye and undergoing the microkeratome procedure on the other one. The visual outcome differences between the corrected distance visual acuity (CDVA) at baseline and the uncorrected distance visual acuity (UDVA) on the first day postoperatively were set as the efficiency index for both groups. All visual acuity outcome results and the deviation of flap thickness were evaluated. P-values <0.05 were considered statistically significant.

Results

The index of efficiency regarding the postoperative visual outcomes in the microkeratome group was lower (P<0.0001). This result was correlated with the difference between intended and achieved flap thickness (P=0.038; r=0.28), and a negative relationship in the regression analysis was confirmed (P<0.04; R²=0.1428). The UDVA in the microkeratome group improved significantly by the end of the first month (P<0.0271) in comparison to the baseline CDVA. The deviation between intended and postoperative flap thickness using either optical coherence pachymetry or Heidelberg Retinal Tomography II confocal microscopy was statistically significant (paired t-test; P<0.001) between the groups. The flap thickness deviation in the microkeratome group was higher. In the femtosecond laser group, the efficiency index was stable postoperatively (P=0.64) The UDVA improved significantly by the end of the first postoperative week (P=0.0043) in comparison to the baseline CDVA. Six months after surgery, improvement in the UDVA was significant in both groups (all P<0.001; one way analysis of variance).

Conclusion

Femtosecond laser was superior to microkeratome-assisted LASIK in terms of flap thickness predictability and the speed of visual acuity recovery. A negative relationship in the regression analysis between increasing flap thickness deviation and visual acuity recovery was confirmed.