A prospective consecutive case series was performed at Gleneagles Hospital, Singapore, to evaluate the early visual and aberrometric outcomes after WF-guided myopic LASIK treatments.

All patients underwent a complete preoperative ophthalmological examination including ocular and medical history, measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest and cycloplegic refraction, slit-lamp examination, computerized Orbscan to pography (Bausch & Lomb), pachymetry, applanation tonometry and fundoscopy. Wavefront-aberration measurements (iDesign aberrometer; Johnson and Johnson Vision) were performed to calculate RMS-HOAs, spherical aberration (SA), and primary coma-like aberration for a pupil diameter of 6 mm. If applicable, patients were asked to discontinue the use of soft or rigid gas permeable contact lenses prior to the preoperative examination for at least one or 3 weeks, respectively.

Exclusion criteria for corneal refractive procedure included a myopic spherical equivalent over −10 D, monocular CDVA of less than 20/20, unstable refraction during the last 12 months, inability to return for the scheduled follow-up examinations, diagnosis of dry eye, any corneal opacity, significant pathology of the anterior segment, significant residual, recurrent or active ocular disease, previous intraocular or corneal surgery, history of herpetic keratitis, diagnosis of immunodeficiency, systemic connective tissue diseases or atopic syndrome, insulin-dependent diabetes mellitus, subjects taking systemic medications likely to affect wound healing or vision, unstable or irregular topography readings, specifically corneal ectatic diseases, intraocular pressure over 23 mmHg by Goldmann applanation tonometry, history or suspect of glaucoma, media opacities, iris coloboma or any other irregularity of the pupil margin, and pregnancy or breastfeeding. There was no restriction on patients with large mesopic pupil diameter measured with an infrared pupillometer.

All eyes were treated with a WF-guided ablation profile (Advanced CustomVue) calculated according to the aberrometric measurements obtained with the high-resolution Hartmann-Shack aberrometer iDesign (Johnson and Johnson Vision). This aberrometer is an optimized wavefront sensor based on the WaveS can system. It has been developed with a higher quantity and density of lenslets to allow the analysis of 1257 points for a 7.0 mm-pupil and a higher dynamic range (−16 D to +12 D of sphere, 0 to 8 D of cylinder and up to 8 µm of HOA RMS) [5] .

The laser ablation was performed using the VISX STAR S4 excimer system (Johnson and Johnson Vision) according to the wavefront aberration data measured preoperatively. Treatments were programmed to ensure complete coverage of the mesopic pupil. The refractive target was emmetropia in all cases. All aberrometric measurements were performed under physiologic conditions in dim illumination by experienced operators and without pupil dilation.

All surgeries were performed by the same surgeon (Dr Lee Hung Ming) under topical anesthesia. Preoperatively, the eyes were prepared by cleansing the periocular zone and instillation of two drops of a topical anesthetic. Corneal flaps were created using the femtosecond laser system (IntraLase, Johnson and Johnson Vision). In all eyes, the VISX STAR S-4 IR laser with a wavefront guided ablation was used considering a torsional registration that was previously performed and applied if necessary. Standard topical postoperative treatment was administered to all patients consisting of a combination of Pred Forte and Cravit 5 times a day for one week, tapering the frequency during the two following weeks. Also, patients were instructed to use an artificial tear solution at least every two hours the day after the surgery and at least four times a day during one month.

Follow-up examinations were performed one and 3 months after surgery and included UDVA, CDVA, manifest refraction, and aberrometric outcomes for a 6-mm pupil diameter.

Data analysis was performed using the software SPSS for Windows version 19.0 (IBM, Armonk, NY, USA). Normality of data samples was evaluated by means of the Kolmogorov-Smirnov test. When parametric analysis was possible, the Student t test for paired data was used for comparisons between the preoperative and postoperative data, whereas the Wilcoxon rank sum test was applied to assess the significance of such differences when parametric analysis was not possible. In addition, the Chi-square test was used for comparing percentages between consecutive visits. For all statistical tests, a p-value of less than 0.05 was considered as statistically significant.

Pre- and postoperative visual acuity and refraction outcomes are summarized in Table 1. Mean logMAR UDVA improved from 1.05 ± 0.48 (SD) preoperatively to −0.04 ± 0.06 (SD) at one month and −0.06 ± 0.06 (SD) at 3 months postoperative. P-values associated to the changes between the follow-up periods are summarized in Table 2. Regarding the longitudinal changes in UDVA, statistically significant differences were found between all 3 postoperative visits (p ≤ 0.001).

The mean preoperative SE (spherical equivalent) decreased from −4.63 D ± 1.79 (SD) to 0.33 D ± 0.31 (SD) and 0.20 D ± 0.31 (SD) one and 3 months after surgery (p < 0.001), respectively. Statistically significant differences were also found in SE between one and 3 months postoperative (p = 0.002). The mean preoperative sphere decreased from −4.07 D ± 1.78 (SD) to 0.44 D ± 0.32 (SD) and 0.32 D ± 0.30 (SD) one and 3 months postoperatively, respectively (p < 0.001). Small in magnitude but statistically significant differences were found in sphere between one and 3 months postoperative (p = 0.012). The mean preoperative cylinder decreased from −1.09 D ± 0.88 (SD) to −0.21 D ± 0.27 (SD) and −0.26 D ± 0.28 (SD) one and 3 months after surgery, respectively (p < 0.001). No statistically significant differences in cylinder were found between the one and 3-month postoperative examinations (p = 0.051). Regarding predictability, all

Abbreviations: UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity; SD, standard deviation; D, diopter.

Abbreviations: UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity; SD, standard deviation.

eyes had a SE within ±1 D along the complete follow-up and 92% of eyes were within ±0.50 D at the end of the follow-up (Figure 1). Figure 2 shows a scattergram demonstrating the high correlation factor (r²) between the intended and the attempted refractive outcome.

Postoperative UDVA was 0.00 logMAR (20/20 Snellen scale) or better in 100% of eyes and 65.3% of eyes reached a 3-month postoperative UDVA of −0.20 logMAR (20/12.5 Snellenscale) or better (Figure 3). As expected, the improvement in UDVA after surgery was statistically significant (p < 0.05), while the change in CDVA was not statistically significant (p > 0.05) (Figure 4). Regarding safety, no eyes lost lines of CDVA and 73% of eyes gained one line of CDVA at the end of the follow-up (Figure 5).

Preoperatively, total ocular HOA RMS (6-mm pupil) was 0.20 µm ± 0.06 (SD), spherical aberration was −0.05 µm ± 0.11 (SD) and coma-like aberration was 0.10 µm ± 0.06(SD). After 3 months, the induction of total ocular HOA was

statistically not significant (p = 0.050). Total ocular HOA RMS increased to 0.23 µm ± 0.10 (SD), spherical aberration changed to 0.03 µm ± 0.08 (SD) nd coma-like aberration RMS increased to 0.15 µm ± 0.11 (SD) (p < 0.01) (Table 3).