A Multicenter Study of the Prevalence of Dry Eye Disease in Chinese Refractive Surgery Candidates.

OBJECTIVE: The aim of this study was to determine the prevalence of preoperative dry eye disease and evaluate tear film function in refractive surgery candidates in China. METHODS: In this prospective noninterventional cross-sectional study, refractive surgical candidates from 13 preselected eye hospitals in China were recruited from July 2015 to February 2016. Patient histories, subjective symptoms, tear film breakup time (TBUT), ocular surface fluorescein staining, and Schirmer I tests (SIT), were assessed to conduct subgroup analysis. RESULTS: A total of 1,849 patients were recruited, 41.4% were diagnosed with dry eye disease (766/1,849) and 44.9% (830/1,849) of subjects had a positive history of contact lens (CL) wear. The overall mean TBUT and SIT values were 7.3 ± 3.7 s and 15.2 ± 8.8 mm, respectively. The total prevalence of ocular surface fluorescein staining was 23.46% (422/1,849); 44.62% of patients had TBUT <5 s and 23.20% of patients had SIT <5 mm. CL wearers were observed to have a higher prevalence of dry eye than non-CL wearers (54.1 vs. 35.2%, OR = 2.17, 95% CI: 1.77-2.65). CONCLUSIONS: In this study, the most common abnormal finding in dry eye disease was tear film instability. A high proportion of refractive surgery candidates have preexisting dry eye disease and a history of CL wear prior to surgery. Careful attention should be given to the evaluation of preoperative dry eye in refractive surgery candidates.

Comparison of planned versus achieved central corneal stromal thickness reduction in SMILE versus FS-LASIK: a retrospective study.

Accuracy of planned corneal stromal thickness (CST) reduction is essential to the safety of laser vision correction. This study was to compare the accuracy of the planned central CST reduction in small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK). A total of 77 patients (43 for SMILE, 34 for FS-LASIK using Custom-Q algorithm) were included in this retrospective study. At postoperative 6-18 months, the central CST reduction was overestimated by 18.49 ± 6.42 µm in the SMILE group (P < 0.001) and underestimated by 2.56 ± 7.79 µm in the FS-LASIK group (P = 0.064). The planned-achieved difference (PAD) of central CST reduction was positively correlated with preoperative manifest refraction spherical equivalent (MRSE) and with planned central CST reduction in both groups. When calculated by manifest refraction (MR) without nomogram adjustment, the central CST reduction was overestimated by 11.14 ± 6.53 µm in the SMILE group and underestimated by 2.83 ± 7.39 µm in the FS-LASIK group. The PAD of central CST reduction without nomogram was significantly narrowed in SMILE and maintained in FS-LASIK, suggesting estimation using MR without nomogram adjustment may be feasible for SMILE and FS-LASIK in clinical practice.

Early visual function outcomes of topography-guided FS-LASIK and SMILE in treatment of myopia and myopic astigmatism.

AIM: To compare the quality outcomes of vision at early phase after topography-guided femtosecond laser-assisted in situ keratomileusis (FS-LASIK-CV) and small incision lenticule extraction (SMILE) in treatment of myopia and myopic astigmatism. METHODS: Retrospective comparative analysis of 49 patients that underwent FS-LASIK (n=23) or SMILE (n=26) procedure for myopia and myopic astigmatism between April and September in 2019. Pre- and postoperative uncorrected visual acuity (UCVA), spherical equivalent refraction (SEQ), cylindrical refraction, contrast sensitivity function (CSF), and corneal higher-order aberrations (HOAs) were evaluated. Independent t-test was used for inter-group comparison, while repeated measures ANOVA was used to analyze changes at different time points. RESULTS: In both groups, 100% of the eyes obtained a UCVA of 20/20 or better at 1wk, 1, and 3mo postoperatively. At 1d and 3mo postoperatively, UCVA was better in FS-LASIK-CV group than in SMILE group. At 1wk postoperatively, SEQ was lower in SMILE group than in FS-LASIK-CV group (P=0.006). At 3mo postoperatively, the SEQ reached target refraction in both groups. The residual astigmatism was reduced in both groups without intergroup difference (P>0.05). At 3mo postoperatively, the spherical aberration and coma under 6 mm pupil size were higher than preoperative levels in both groups (P<0.05). However, the increase in the corneal HOAs in the FS-LASIK-CV group was less than the SMILE group (P<0.05). At 3mo postoperatively, the logCS were better than preoperative levels under scotopic conditions without glare and scotopic conditions with glare in both groups (P<0.05). At 1 and 3mo postoperatively, under scotopic conditions without glare and scotopic conditions with glare, FS-LASIK-CV group showed more improvement in logCS at two spatial frequencies (12.0 c/d and 18.0 c/d; P<0.05). CONCLUSION: Both FS-LASIK-CV and SMILE demonstrate to be safe, effective, and predictable in treatment of myopia and myopic astigmatism. Early postoperative improvement in UCVA and CSF at high spatial frequency under scotopic conditions were better after FS-LASIK-CV than SMILE.

Assessment of corneal biomechanics, tonometry and pachymetry with the Corvis ST in myopia.

To evaluate the repeatability of Corvis ST corneal biomechanical, tonometry and pachymetry measurements, and agreement of pachymetry measures with the Pentacam HR and RTVue OCT. Three consecutive measurements of the right eye of 238 myopic subjects were acquired with the Corvis ST, Pentacam HR, and RTVue OCT. Repeatability of Corvis ST was evaluated by within-subject standard deviation [Sw] and repeatability limit [r]. The agreement of central corneal thickness (CCT) measurements were compared among the three instruments using the Bland-Altman limits of agreement. Comparisons were further stratified by CCT (Corneathin ≤ 500 µm; Corneanormal = 500-550 µm; Corneathick > 550 µm). Sw was below 1 mmHg in Corneathin, Corneanormal, and Corneathick groups for IOP and bIOP. Sw for SP-A1 were 4.880, 6.128, 7.719 mmHg/mm respectively. Sw for CBI were 0.228, 0.157, 0.076, and correspondingly Sw for TBI and SSI were 0.094 and 0.056, 0.079 and 0.053, 0.070 and 0.053. The Bland-Altman plots for CCT implied poor agreement with mean differences of 29.49 µm between Corvis and OCT, 9.33 µm between Pentacam and OCT, and 20.16 µm between Corvis and Pentacam. The Corvis ST showed good repeatability with the exception of CBI in the various CCT groups. The CCT measured by Corvis ST was not interchangeable with Pentacam HR and RTVue OCT.