Using femtosecond laser to create customized corneal flaps for patients with low and moderate refractive error differing in corneal thickness.

This study is designed to evaluate the visual outcomes, accuracy, and predictability of corneal flaps with different thicknesses created by 60-kHz femtosecond laser according to different corneal thicknesses in the patients with low and moderate refractive error. A total of 182 eyes were divided according to the central corneal thickness (470 μm-499 μm in Group A, 500 μm-549 μm in Group B, and 550 μm-599 μm in Group C) and underwent femtosecond laser-assisted LASIK for a target corneal flap thickness (100 μm for Group A, 110 μm for Group B, and 120 μm for Group C). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and refractive status were examined. The flap thickness of each eye was measured by anterior segment optical coherence tomography (AS-OCT) on 30 points at 1-month follow-up to assess the accuracy and predictability. Postoperatively, at least 75% of eyes had a UDVA of 20/16 or better, less than 2% of eyes lost one line, over 30% of eyes gained one or more lines in CDVA, at least 95% of eyes had astigmatism of less than 0.25 D, all eyes achieved a correction within ± 1.00 D from the target spherical equivalent refraction. The visual and refractive outcomes did not differ significantly in all groups (P >0.05). The mean flap thickness was 100.36 ± 4.32 μm (range: 95-113 μm) in Group A, 111.64 ± 3.62 μm (range: 108-125 μm) in Group B, and 122.32 ± 2.88 μm (range: 112-128 μm) in Group C. The difference at each measured point among the three groups was significant (P < 0.05). The accuracy and predictability were satisfactory in all three groups. In conclusion, this customized treatment yielded satisfactory clinical outcomes with accurate and predictable flap thickness for patients with low and moderate refractive error

Preoperative characteristics of the three groups of patients with refractive error.

<p>IOP, intraocular pressure; CCT, central corneal thickness. All data of IOP, CCT, and K value are presented as mean ± standard deviation (SD) of all eyes in relevant groups.</p><p>Preoperative characteristics of the three groups of patients with refractive error.</p

Preoperative corrected distance visual acuity (CDVA) and 1-month postoperative uncorrected distance visual acuity (UDVA) for Group A (A), Group B (B), and Group C (C).

<p>The central corneal thickness was 470–499 μm in Group A, 500–549 μm in Group B, and 550–599 μm in Group C; the target corneal flap thickness was 100 μm for Group A, 110 μm for Group B, and 120 μm for Group C. Preoperative CDVA was 20/20 or better, and 1-month postoperative UCVA was 20/20 or better for all the groups.</p

Postoperative spherical equivalent refraction for the three groups at 1 month after operation.

<p>The percentage of eyes with spherical equivalent refraction within ±0.50 D ranges from 75% to 85%. In all eyes, spherical equivalent refraction was within ±1.00 D.</p

The 1-month postoperative refractive astigmatism for Group A (A), Group B (B), and Group C (C).

<p>The percentage of eyes with refractive astigmatism less than 0.50 D ranges from 95% to 100%. Refractive astigmatism between 1.01 D and 1.25 D was observed only in 2% of the eyes in Group B.</p

Stability of postoperative spherical equivalent refraction for Group A (red), Group B (green), and Group C (blue).

<p>A change of more than ±0.50 D was found in only 1.6%–9.3% of eyes in the three groups.</p

Changes in Snellen CDVA for the three groups at 1 month after operation.

<p>The percentage of eyes lost 1 line of preoperative CDVA ranges from 1% to 2%, and the percentage of eyes gained 1 or more lines ranges from 34% to 49% for the three groups.</p

Comparison of the 1-month postoperative central, paracentral, and peripheral mean flap thicknesses among the three groups.

<p>“+” denotes superior side, and “-” denotes inferior side.</p