Three-year results of central corneal stromal thickness reduction in small-incision lenticule extraction for high myopia correction.

BACKGROUND: To investigate the long-term corneal stromal remodeling and central stromal thickness (CST) reduction accuracy after small-incision lenticule extraction (SMILE) for high myopia correction. METHODS: This prospective study included 30 patients (50 eyes) who had undergone SMILE. Measurements of CST reduction using optical coherence tomography were performed at 1 month, 6 months, 1 year, and 3 years after surgery. Correlations were performed between planned and achieved CST reductions. RESULTS: The study enrolled 50 eyes of 30 patients. The mean spherical equivalent was -9.25±1.52 D(diopters). The postoperative CST increased in the first month after surgery and remained stable for a year. Thereafter, it remained stable during follow-up from 1 to 3 years postoperatively. The predicted CST reduction was 146.4 ± 10.3 µm. The achieved CST reductions at 1 month, 6 months, 1 year, and 3 years after surgery were 135.3 ± 12.1 µm, 130.8 ± 10.6 µm, 125.9 ± 9.4 µm, and 122.2 ± 10.6 µm, respectively. An overestimation of CST reduction was observed three years after surgery. Correlation analysis revealed a strong correlation between planned and achieved CST reductions; however, no correlation was found between CST reductions predicted error and the planned CST reductions. CONCLUSION: During long-term follow-up, our findings revealed a significant stromal remodeling following SMILE in patients with high myopia. Therefore, clinicians should consider it when screening patients with high myopia for SMILE.

Epithelial and stromal thickness profile and lens decentration in myopic orthokeratology / Perfil de espesor epitelial y estromal y descentrado del cristalino en ortoqueratología miope

Purpose: To study topographic epithelial and total corneal thickness changes in myopic subjects undergoing successful orthokeratology treatment in connection with the objective assessment of contact lens decentration. Methods: A prospective-observational and non-randomized study in 32 Caucasian myopic eyes undergoing Ortho-k for 3 months. Total, epithelial, and stromal thicknesses were studied before and after Ortho-k treatment, using optical coherence tomography with anterior segment application software. Central, paracentral, and mid-peripheral values are taken along 8 semi-meridians. Results: The central average total corneal thickness was 4.72 ± 1.04 μm thinner after Ortho-K. The paracentral corneal thickness showed no significant changes (p = 0.137), while the mid-peripheral corneal thickness was increased by 3.25 ± 1.6 μm associating this increase exclusively to the epithelial plot (p<0.001). When lens centration was assessed, a lens fitting decentration less than 1.0 mm was found for the whole sample, predominantly horizontal-temporal (87.5%) and vertical-inferior (50%) decentring. Corneal topographical analysis revealed a horizontal and vertical epithelial thickness asymmetric change profile with paracentral temporal thinnest values, and mid-peripheral nasal thickest values. Conclusions: The present study found a central corneal thinning induced by Ortho-k lenses in subjects with moderate myopia, only associated with a change in epithelial thickness, as well as mid-peripheral thickening, that seems to be mainly epithelial in origin. The authors also found a tendency of contact lens decentration toward temporal and inferior areas conditioning an asymmetric epithelial redistribution pattern.(AU)

Assessment of Changes in Cap and Residual Stromal Thickness Values during a 6-Month Observation after Refractive Lenticule Extraction Small Incision Lenticule Extraction.

Background: In this study, the changes in corneal cap and residual stromal thickness (RST) values during a 180-day observation period after refractive lenticule extraction small incision lenticule extraction (ReLEx SMILE) were assessed. Methods: Fifty patients underwent ReLEx SMILE using the VisuMax 500 femtosecond laser, with corneal imaging conducted pre and post procedure via anterior segment optical coherence tomography (AS-OCT). Cap thickness in the center and 1.5 mm from the center in four meridians was measured at various intervals. Results: The results showed a significant decrease in cap thickness 180 days post procedure compared to earlier intervals (p < 0.05). Similarly, RST decreased gradually and significantly post procedure (p < 0.05). Notably, changes in cap thickness within the central 1.5 mm area were more dynamic than RST changes during the 6-month observation period following SMILE. Conclusions: The corneal cap thickness measured with swept-source AS-OCT within the central 1.5 mm area underwent more dynamic changes than the residual stromal thickness during the 6-month observation following SMILE.

Comparative study of small incision refractive lenticule extraction with 5 mm versus 6.5 mm optic zone for myopia.

Purpose: To compare residual stromal thickness (RST) in eyes undergoing small incision refractive lenticule extraction (SMILE) using a lenticular diameter of 6.5 mm versus those with a diameter of 5 mm. Methods: In this retrospective: comparative case series. , consecutive: patients who underwent SMILE between 2016 and 2021 with at least 6 months of follow-up were included. Preoperative best-corrected distance visual acuity (BCDVA), refractive error, contrast sensitivity, central corneal thickness, keratometry, higher order aberrations, and scotopic pupil size were recorded using a Placido disk topography with Sheimpflug tomography-based system. Patients underwent SMILE with a lenticular diameter of 6.5 mm until 2018 (n = 372 eyes). Thereafter, the lenticular diameter was reduced to 5 mm (n = 318). The RST, postoperative refraction, aberrations, subjective glare, and halos were compared across groups at 1 and 6 months. Results: The mean age of participants was 26.8 ± 5.8 years with a mean preoperative spherical equivalent of -4.48 D ± 2.16 D (range: -0.75 to -12.25 D) and mean scotopic pupil of 3.7 ± 0.75 mm. Eyes in the 5 mm group had 30.6 m (95% confidence interval [CI] = 28 to 33 m, P < 0.001) greater RST compared to the 6.5 mm group after adjusting for spherical equivalent and preoperative pachymetry. There were no differences in vision, contrast sensitivity, aberrations (wavefront error of 0.19 ± 0.2 vs. 0.25 ± 0.2, P = 0.19) or glare between the two groups. Conclusion: SMILE performed with a lenticular diameter of 5 mm leads to greater RST across the myopic range, but without inducing significant higher-order aberrations.

Descemet Membrane Endothelial Keratoplasty (DMEK) Reduces the Corneal Epithelial Thickness in Fuchs' Patients.

Fuchs' endothelial corneal dystrophy (FECD) is the occurrence of corneal edema due to endothelial cell dystrophy. Descemet membrane endothelial keratoplasty (DMEK) is considered to be the gold standard of treatment. The aim of this study was to investigate the changes in the corneal epithelial thickness of FECD patients before and after DMEK and to compare these results with a healthy control cohort. In this retrospective analysis, 38 eyes of patients with FECD that were treated with DMEK and 35 healthy control eyes received anterior segment optical coherence tomography (OCT; Optovue, XR-Avanti, Fremont, CA, USA). The corneal epithelial thicknesses in different locations were analyzed and compared between the preoperative, postoperative, and control cohorts. The median follow-up time was 9 months. There was a significant degression of the mean epithelial thickness after DMEK in the central, paracentral, and mid-peripheral zones (p < 0.01) of the cornea. The total corneal thickness and stromal thickness decreased significantly as well. No significant differences were observed between the postoperative and control cohorts. In conclusion, the FECD patients had an increased epithelial thickness compared to the healthy controls, which decreased significantly after DMEK and reached thickness levels comparable to those of healthy control eyes. This study emphasized the importance of distinguishing between the corneal layers in anterior segment pathologies and surgical procedures. Moreover, it accentuated the fact that the structural alterations in FECD extend beyond the corneal stroma.

Comparison of both eyes anterior segment structures of patients with unilateral blunt trauma.

BACKGROUND: To evaluate anterior segment optical coherence tomography (AS-OCT) data in patients with unilateral blunt ocular trauma (BOT), to determine the relationship of results with hyphema development. METHODS: 21 patients who received unilateral BOT were included in the study. Healthy eyes of patients were included in the control group. Iris stromal thickness (IST), schlemm canal area (SCA) and pupil diameter were measured by AS-OCT of the participants. In addition, eyes with ocular trauma were divided into those with and without hyphema and compared in terms of these parameters. RESULTS: The mean nasal and temporal (n-t) IST was measured as 373± 40 µm and 369 ± 35 µm in BOT in comparison with 344 ± 35 µm and 335 ± 36 µm in control eyes, respectively (p = 0.000 and p = 0.001, respectively). The mean nasal and temporal (n-t) SCA was measured as 12,571 ± 880 µm2 and 12,162 ± 1181 µm2 in developed hyphema in comparison with 10,455 ± 1506 µm2 and 10,188 ± 939 µm2 in did not develop hyphema, respectively (p = 0.016 and p = 0.002 respectively). CONCLUSION: The ISTs of the traumatized eyes in the nasal and temporal quadrants were statistically thicker than the other healthy eyes. SCA in both nasal and temporal quadrants of eyes with hyphema was statistically significantly larger than the group without hyphema.

Two-year stability of posterior corneal surface after transepithelial photorefractive keratectomy with a residual stromal thickness less than 350 µm.

PURPOSE: This study aimed to investigate the stability of posterior corneal surface 2 years after transepithelial photorefractive keratectomy (TPRK) in patients with a residual stromal thickness less than 350 µm. METHODS: In total, 408 eyes of 212 patients (160 women, 52 men) who underwent TPRK were enrolled in this retrospective study. All surgeries were performed in the Amaris 750S excimer laser platform with smart pulse technology. The posterior corneal elevation, anterior chamber depth, Q value, and curvature were measured using Pentacam preoperatively and postoperatively. All patients were followed up for 2 years. The relationship between percent tissue altered (PTA), age, and changes in posterior corneal surface was analyzed. RESULTS: The mean preoperative spherical equivalent was - 6.80 ± 1.18 D (range: - 9.00 to - 2.63 D). The mean residual stromal thickness was 336.46 ± 7.25 µm (range: 310-348 µm). The mean PTA was 30.93 ± 2.03% (range: 24.29-35.28%). At 2 years after surgery, the elevation of six points in the central area decreased by 1.91 ± 2.97 µm, 2.98 ± 3.23 µm, 1.17 ± 3.85 µm, 1.70 ± 2.88 µm, 1.36 ± 3.19 µm, and 1.65 ± 3.18 µm, compared with the preoperative value (P < 0.05). The elevation of three points in the peripheral area increased by 1.87 ± 6.34 µm, 0.68 ± 6.00 µm, and 0.95 ± 5.50 µm (P < 0.05). There was no significant linear relationship between PTA, age, and changes in posterior corneal surface, anterior chamber depth, and K2 (all P > 0.05). CONCLUSION: Within 2 years after TPRK, the posterior corneal surface remained stable in patients with a residual stromal thickness between 310 and 350 µm. There was no sign of iatrogenic ectasia during the follow-up period.

[Effects of SMILE with different residual stromal thicknesses on corneal biomechanical properties of rabbits in vivo].

Femtosecond laser small incision lenticule extraction (SMILE) with different residual stromal thicknesses (RST) is set to investigate its effect on corneal biomechanical properties of rabbits in vivo. In this study, 24 healthy adult Japanese rabbits were randomly divided into group A and B. The RST of group A was set 30% of the corneal central thickness (CCT), and the RST of group B was 50% of the CCT. The thickness of the corneal cap in both groups was set one third of CCT. Corneal visualization Scheimpflug technology (Corvis ST) and Pentacam three-dimensional anterior segment analyzer were used to determine corneal biomechanical and morphological parameters before surgery, and 1 week, 1 month and 3 months after surgery. Pearson correlation analysis was used to analyze factors affecting corneal biomechanical parameters after SMILE. The results showed that the corneal stiffness of group A was significantly higher than that of group B at 1 week and 1 month after surgery, and most biomechanical parameters returned to preoperative levels at 3 months postoperatively. The results of correlation analysis showed that postoperative CCT and RST were the main factors affecting corneal biomechanical parameters after SMILE. There was no significant difference in corneal posterior surface height (PE) between 3 months after surgery and before surgery in both two groups. It indicates that although the ability to resist deformation of cornea decreases in SMILE with thicker corneal cap and less RST, there is no tendency to keratoconus, which may be related to the preservation of more anterior stromal layer.

Anterior segment-optical coherence tomography and diabetic retinopathy: Could it be an early biomarker?

INTRODUCTION: To measure the corneal thickness (CT), corneal epithelial thickness (CET), and corneal stromal thickness (CST) in patients affected by type 2 diabetes mellitus with good glycemic control and without any signs of diabetic retinopathy using anterior-segment optical coherence tomography (AS-OCT). METHODS: 60 eyes of 30 diabetic patients and 60 normal eyes of 30 healthy subjects underwent AS-OCT, evaluation of best-corrected visual acuity (BCVA), intraocular pressure (IOP), slit-lamp biomicroscopy, tear film breakup time (TBUT), Schirmer I test and fundus examination. The CT, CET, and CST maps generated corresponded to a 6-mm diameter area of the cornea that was divided into 17 sectors. We compared the CT, CET, and the CST of each sector obtained in the diabetic group with those obtained in the control group. RESULTS: No significant difference in terms of age, gender, BCVA, IOP, TBUT, and Schirmer I test between the two study groups was observed. The CT, CET, and CST in the central section were significantly thickened in diabetic patients than in controls (p<0.001). Also, each paracentral and midperipheral sector was significantly increased in patients compared to controls (p<0.05). CONCLUSIONS: The evaluation of the CT, CET, and CST by AS-OCT could be a valid and non-invasive biomarker in patients effected by diabetes mellitus, useful in early diagnosis of diabetic retinopathy.

Comparison of stromal thickness and doppler findings in polycystic ovary syndrome and healthy women with ultrasonographic evidence of polycystic ovaries? A cross-sectional study.

The purpose of the study was to compare the ovarian stromal blood flow and stromal thickness (ST) of polycystic ovary syndrome (PCOS) patients, with healthy women with polycystic ovarian morphology (PCOM) and normal ovarian morphology (NOM). A total of 220 participants were recruited and the three study groups were determined by diagnostic criteria (PCOS n = 106, PCOM n = 68, NOM n = 46). Clinical, hormonal and ultrasonographic measurements of ovaries were assessed and compared. PCOS patients showed statistically higher androgen levels, insulin resistance, hirsutism score, ovarian ST and stromal blood flow compared to PCOM and NOM. The correlation between free androgen index (FAI) and ST was measured. FAI was significantly highly correlated with left ovarian ST (0.83; p < .001) and right ovarian ST (0.83; p < .001). According to the results of this study, the ovarian ST which can be considered as ultrasonographic indicator of FAI, can be used in PCOS diagnosis. Also, it can be suggested that there is no statistically significant difference in ovarian ST and doppler findings between healthy women with PCOM or NOM. ROC analysis was used to measure diagnostic utility of ST. Impact StatementWhat is already known on this subject? Although it is known that ovarian stromal blood flows and stromal thickness are increased in PCOS disease compared to healthy women, they are not included in the diagnostic criteria.What the results of this study add? In the results of this study, it was determined that ovarian stromal blood flow and stromal thickness were increased in PCOS patients, as previously reported in the literature. In addition, these ultrasound measurements were found to be increased in PCOS patients compared to healthy women with PCO morphology, and stromal thickness measurements were strongly correlated with the free androgen index in PCOS patients.What the implications are of these findings for clinical practice and/or further research? Ovarian ST and/or S/A ratio may be an ultrasonograpic indicator of FAI, and may be used in PCOS diagnostic criterias. In the future, it can be revealed whether they vary in patients with different components of the syndrome, by examining these parameters in different PCOS phenotypes.

Effect of Gender, Age, and Ocular and Growth-Related Factors on Corneal Epithelial and Stromal Thickness in Children.

Data on corneal epithelial and stromal thickness in school-aged children in relation to gender, age, and ocular and growth parameters are limited. In this retrospective study, we analyzed corneal epithelial and stromal thickness measured with the RTVue system (Optovue, Inc., Fremont, CA, USA) in 122 male and 201 female Korean children (mean age 9.59 ± 2.18 years) with myopia. We used simple and multiple regression analysis to establish the relationships between gender, age, refractive status, axial length, anterior chamber depth (ACD), corneal refractive power, white-to-white corneal diameter (WTW), height, and body weight. Age, body weight, height, and central corneal thickness were positively associated with corneal epithelial thickness, whereas WTW was negatively associated. The multiple regression analysis showed corneal epithelial thickness was affected by sex, body weight, WTW, and central corneal thickness (CCT), while stromal thickness was influenced by age, sex, and WTW. Both corneal epithelial and stromal thickness were significantly greater in male than in female children and were affected by growth. Neither corneal epithelial nor stromal thickness were associated with the severity of myopia, corneal refractive power, or axial length.

In vivo analysis and comparison of anterior segment structures of both eyes in unilateral Fuchs' uveitis syndrome.

PURPOSE: To compare corneal endothelial cell density (ECD), iris stromal thickness (IST), iris pigment epithelium optical density (IPE OD), and Schlemm's canal (SC) measurements in patients having unilateral Fuchs' uveitis syndrome (FUS). METHODS: This is a randomized, prospective study. Currently, diagnosed unilateral FUS and phakic cases were defined to be the inclusion criteria to the study. The specular microscope was used to measure ECD. Anterior segment images were acquired by using SD-OCT. The images were extracted and uploaded to the ImageJ program for further analysis. Two blinded investigators analyzed the IST, IPE OD, and SC area in both healthy (N) and affected eyes (FUS) and the comparative analysis was made by using SPSS program. RESULTS: Of twenty-one participants, 13 were female (62%). The mean age of the participants was 30 ± 9 (18-47) years. ECD was 2228 ± 365 and 2513 ± 209 cells/mm2 in the FUS and N, respectively (p < 0,001). In FUS, the mean nasal and temporal (n-t) IST was measured as 380 ± 44 and 347 ± 41 µm, compared to 393 ± 61 and 355 ± 62 µm in N, respectively (p = 0.3 and p = 0.4 respectively). The mean n-t IPE OD was measured as 1110 ± 499 and 937 ± 370 in FUS, compared to 1147 ± 528 and 1267 ± 428 in N, respectively (p = 0.008 temporal). The mean n-t SC area was measured as 5479 ± 1951 and 5624 ± 2722 µm2 in FUS, compared to 5736 ± 2574 and 5633 ± 1835 µm2 in N, respectively (p = 0.9 and p = 0.7 respectively). CONCLUSION: Decreased ECD in FUS may lead to serious complications after cataract surgery. Temporal IPE depigmentation occurs prior to the nasal side in FUS.

Corneal thickness, residual stromal thickness, and its effect on opaque bubble layer in small-incision lenticule extraction.

PURPOSE: To evaluate the effects of the central corneal thickness (CCT) and residual stromal thickness (RST) on the formation of opaque bubble layer (OBL) during small-incision lenticule extraction (SMILE). METHODS: A total of 345 eyes from Refractive Surgery Center database at Tianjin Eye Hospital that had been subjected to SMILE surgery and followed for 6 months were included in this study and divided into OBL and OBL-free groups. Preoperative, intraoperative, and postoperative data for all eyes were evaluated and analyzed using multivariate regression analysis. After adjustment for several confounding factors, potential associations of CCT and RST with OBL were elucidated by determining odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: In total, 22 of the 345 eyes developed various degrees of OBL during the femtosecond laser scanning phase of SMILE surgery. After adjustment for age, sex, and refractive errors, significant relationships were detected between CCT and RST and OBL formation (OR 1.04; 95% CI 1.02-1.06; OR 1.03; 95% CI 1.02-1.05, respectively, P < 0.001). Smooth curve fitting revealed an increased risk of OBL in the presence of an increased CCT or RST. However, visual outcomes were comparable between the two groups at both 3 and 6 months postoperatively. CONCLUSIONS: The results suggest that OBL formation during SMILE surgery is more likely in eyes with a thicker cornea. CCT and RST can be considered independent risk factors for OBL formation. Although this phenomenon may disturb the surgical procedure, it is unlikely to affect the postoperative visual outcome.

Age-related differences in corneal epithelial thickness measurements with anterior segment optical coherence tomography.

PURPOSE: To measure corneal epithelial thickness (CET) in healthy adults and to investigate its variation with age by use of anterior segment optical coherence tomography (OCT). METHODS: A total of 210 healthy individuals were enrolled and divided into four, almost equally sized groups on the basis of age: 18-29 years (group 1), 30-44 years (group 2), 45-59 years (group 3), and 60-80 years (group 4). The CET and total corneal thickness in the central area (diameter 6.0 mm) of each patient were obtained by Fourier-domain OCT, and the regional thickness and topographic variability were compared among the age groups. In addition, the correlations between the CET and age, gender, and refractive status were analyzed using partial correlation tests and multiple regression analysis. RESULTS: The CET of the central segment (diameter 2 mm) in groups 1, 2, 3, and 4 were 53.74 ± 3.82, 54.48 ± 3.33, 53.89 ± 3.73, and 53.30 ± 3.36 µm, respectively, demonstrating no significant change with age (P = 0.416). In most of the paracentral and all of the midperipheral zones (annuli 2-5 and 5-6 mm from the center, respectively), the CET differed significantly among the four groups. Correlation analysis suggested that the CET is greater in men than in women and that the CET of both the paracentral and the midperipheral zones is inversely correlated with age. Topographic variability was also inversely correlated with age. CONCLUSIONS: The CET became thinner with age in the paracentral and midperipheral zones, while the central CET seems to remain constant. Gender differences should be considered in the assessment of CET.

The roles of cornea and axial length in corneal hysteresis among emmetropes and high myopes: a pilot study.

PURPOSE: To observe the roles of cornea and axial length (AL) in corneal hysteresis (CH) among emmetropes and high myopes. MATERIALS AND METHODS: The CH, corneal resistance factor (CRF) and corneal-compensated intraocular pressure (IOPcc) of 40 young emmetropes (spherical equivalent +/-0.50 D) and 40 age-matched high myopes (-6D or more) were measured by the Ocular Response Analyzer. AL was measured using a partial coherence interferometer. The mean keratometry reading (meanK) and corneal volume (CV) in 4 zones were measured using the Pentacam. Full stromal thickness (FST) and epithelial and Bowman's thicknesses (Epi + BT) were evaluated using confocal microscopy. Valid confocal microscopic results from the more emmetropic eyes of 30 emmetropes and the more myopic eyes of 27 high myopes were studied. RESULTS: High myopes exhibited significantly longer AL (27.34 ± 0.90 mm versus 23.71 ± 0.79 mm), lower CH (10.17 ± 1.38 mmHg versus 11.11 ± 1.25 mmHg), and higher IOPcc (16.50 ± 3.05 mmHg versus 13.91 ± 2.49 mmHg) compared with emmetropes. The 2 groups showed similar CRF, CVs, meanK, FST and Epi + BT. By combining the results of both groups, CH and CRF were significantly correlated with FST (r(2)= 0.368 and r(2 )= 0.408, respectively), CVs (r(2)= 0.251-0.391 and r(2)= 0.201-0.346, respectively), but not with Epi + BT or meanK. Furthermore, AL and IOPcc were significantly correlated with CH (r(2)= 0.112 and r(2)= 0.161, respectively) but not with CRF. The multivariate analysis indicated that FST (standardized coefficients, ß = 0.591) and CV (ß = 0.575) had stronger association than IOPcc and AL for CH. CONCLUSIONS: High myopes exhibited lower CH than emmetropes. Although CH had stronger correlation with FST than AL, it might contain the biomechanical properties of components other than the cornea.