To investigate the changes in posterior corneal elevation within 6mo after small incision lenticule extraction (SMILE) surgery for myopia and myopic astigmatism in patients with thin corneas.

A prospective study included patients with thin corneas (preoperative thinnest corneal thickness ranging from 480 to 520 μm) who underwent SMILE for myopia or myopic astigmatism. Corneal topography and posterior corneal elevation were assessed using Pentacam HR at three time points: preoperatively, 1mo, and 6mo postoperatively. The measured parameters included thinnest point elevation (PTE), posterior maximal elevation (PME), posterior central elevation (PCE), and 24 additional reference points.

A total of 106 eyes from 106 patients (age range: 18-34) were included in the study. Uncorrected distance visual acuity (UDVA) improved significantly, with a mean logMAR value of -0.07±0.06 at the final follow-up visit. Measurements of posterior corneal elevation showed no significant changes in most points, hemispheres, and meridians at 6mo postoperatively. Notably, only two points, ∆E_2mm-45° and ∆E_2mm-90°, exhibited statistically significant elevation changes: the elevation of ∆E_2mm-45° increased from -2.3±4.99 to -1.0±5.9 μm (P=0.0037), and that of ∆E_2mm-90° increased from -16±7.53 to -15±7.4 μm (P=0.016). However, these changes were within the measurement error range of the Pentacam HR (±5 μm in a 5 mm area).

SMILE surgery is a safe and stable procedure for correcting myopia or myopic astigmatism in patients with thin corneas, as evidenced by the stability of posterior corneal elevation.

To investigate the ocular surface parameters in patients with moderate to high myopia.

This prospective study was conducted in May 2023, enrolling patients with moderate to high myopia (spherical equivalent refraction ≤-3.0 D). After completing the Ocular Surface Disease Index (OSDI) questionnaire, refractive parameters and non-invasive tear film parameters were measured, followed by the Schirmer Ⅰ test and fluorescein sodium staining. The diagnosis of dry eye disease was based on OSDI score, non-invasive tear breakup time (NIBUT), Schirmer Ⅰ test, and fluorescein sodium staining results, according to the 2020 Chinese Expert Consensus on Dry Eye. The Mann-Whitney U test was used to compare ocular surface parameters between moderate and high myopia, as well as between patients with and without dry eye. Pearson correlation analysis was employed to assess the relationship between the lipid/muco-aqueous layers and tear film parameters. A general linear mixed model (GLMM) was used to analyze the impact of refractive parameters on ocular surface parameters after adjusting for age and sex.

A total of 35 eyes with moderate to high myopia (12 males; mean age, 30.30±5.45y) were included in the study. Among them, 26 eyes were classified as normal and 9 as dry eye. Of the 9 dry eye cases, 7 were observed in the high myopia group (n=18) and 2 in the moderate myopia group (n=17). Among the enrolled patients, those with high myopia demonstrated significantly higher OSDI scores than those with moderate myopia (P=0.0417). Patients with dry eye exhibited significantly shorter interblink intervals (P=0.0081) and higher OSDI scores (P=0.0001) than those without dry eye. Pearson correlation analysis revealed a significant positive correlation between lipid layer thickness (LLT) and tear meniscus height (r=0.395, P=0.023), and a significant negative correlation between the muco-aqueous layer thickness change rate (MALTR) and OSDI score (r=-0.466, P=0.016). After adjusting for age and sex using the GLMM, spherical refraction (SPH, β=-1.802, P=0.048) and axial length (AL, β=2.784, P=0.048) significantly impacted OSDI score. Corneal front astigmatism significantly influenced Schirmer Ⅰ test results (β=8.377, P=0.024). The difference between central corneal thickness and the thinnest corneal thickness significantly affected LLT (β=-2.294, P=0.026). White-to-white diameter significantly impacted MALTR (β=-81.758, P=0.037).

In moderate to high myopia, higher SPH and AL correlate with increased dry eye symptoms, which are associated with muco-aqueous and lipid layer alterations. Corneal regularity and diameter also affect tear film dynamics.

To investigate the long-term changes of corneal densitometry (CD) and its contributing elements after small incision lenticule extraction (SMILE).

Totally 31 eyes of 31 patients with mean spherical equivalent of -6.46±1.50 D and mean age 28.23±7.38y were enrolled. Full-scale examinations were conducted on all patients preoperatively and during follow-up. Visual acuity, manifest refraction, axial length, corneal thickness, corneal higher-order aberrations, and CD were evaluated.

All surgeries were completed successfully without complications or adverse events. Ten-year safety index was 1.17±0.20 and efficacy 1.04±0.28. CD value of 0–6 mm zones in central layer was statistically significantly lower 10y postoperatively, compared with preoperative values (0–2 mmΔ=-1.62, 2–6 mmΔ=-1.24, P<0.01). There were no correlations between CD values and factors evaluated.

SMILE is a safe and efficient procedure for myopia on a long-term basis. CD values get lower 10y postoperatively, whose mechanism is to be further discussed.

To investigate the effect of 0.01% low-concentration atropine (LA) on quantitative contrast sensitivity function (qCSF) in children with myopia.

This paired case-control study included 90 eyes of 58 children who were sex-, age-, and refraction-matched and equally divided into two groups: the 0.01% LA group had undergone 6mo use of daily 0.01% atropine and control group was naïve to LA. Routine ophthalmic examinations and qCSF test without refractive correction were performed. Two groups were compared in monocular and binocular qCSF parameters, including the area under logCSF, CSF acuity, and contrast sensitivity (CS) at 1.0-18.0 cycle per degree (cpd).

In the monocular comparison, the CSF acuity of the LA group was significantly higher than that of the control group (7.58±5.51 vs 6.37±4.22 cpd, P<0.05). The subgroup analysis showed that in the 6-9y group, CSF acuity was significantly higher in the LA group than the control group (8.76±6.19 vs 6.54±4.25 cpd, P<0.05), and in the Female group, low refraction sphere group, and high refraction cylinder group, the CS at high spatial frequencies (12.0 and 18.0 cpd) were significantly higher in the LA group than in the control group (all P<0.05). In the binocular test, CSF acuity and CS at 12.0 cpd were significantly higher in the LA group than in the control group (10.95±7.00 vs 8.65±5.12 cpd; 0.17±0.33 vs 0.06±0.16, respectively; both P<0.05).

Use of LA may result in improved CS in children with early onset myopia.