Changes In Corneal Curvature Research Articles

Changes in corneal curvature and astigmatism in senile cataract patients after phacoemulsification.

Analysis of changes in corneal curvature and astigmatism after phacoemulsification for senile cataracts. Retrospective collection of clinical data from patients who underwent uncomplicated phacoemulsification at the First Affiliated Hospital of Soochow University. The changes in total corneal curvature, anterior surface curvature, posterior surface curvature, and astigmatism were measured by the Sirius system. The axial length was measured by Lenstar 900. The total corneal curvature and anterior surface curvature at 3 months were all larger than those before phacoemulsification, and the difference was statistically significant (p < 0.05). Compared with preoperative results, there was no significant change in corneal posterior surface curvature and astigmatism 3 months after surgery (p > 0.05). Changes in corneal curvature and astigmatism were not significantly correlated with age at 3 months after surgery (p > 0.05). Postoperative astigmatism was increased with the growth of axial length, while corneal curvature was decreased (p < 0.05). Phacoemulsification can lead to increased postoperative corneal curvature in elderly cataract patients, and with the growth of the axial length, the corneal astigmatism was increased.

Corneal Curvature Change After Strabismus Surgery: An Experience from a Single-academic Center

Objective: This study aimed to explore corneal curvature changes following strabismus surgery using a quadric surface fitting model to address ocular misalignment. Material and Methods: In this prospective cross-sectional study, 54 completed cases (84 eyes) of patients aged 6–60 years old (mean 10 years old) undergoing horizontal rectus muscle surgery were examined using placido-based keratometry with the Oculus Keratograph 5M system. Data on corneal curvature were collected one week pre-operation, and again one week, one month, and three months post-operation. Asphericity in the vertical meridian (Qy) and horizontal meridian (Qx), and surgical-induced astigmatism (SIA) were calculated. Results: The 84 eyes included were categorized into three groups: horizontal muscle surgeries, oblique muscle surgery, and combined horizontal and oblique muscle surgeries. Significant corneal prolation (steep central, flat peripheral) was revealed in the vertical meridian (Qy) at 3 months postoperatively for lateral rectus (LR) recession in the first group (p &lt; 0.001), and the mean SIA was 0.45 D (95% CI: 0.35–0.56 D). A similar effect was seen in the vertical meridian of the third group (p &lt; 0.01), with a mean SIA at 3 months of 0.27 D (95% CI: 0.23–0.32 D). Conclusion: Lateral rectus muscle recession induces corneal vertical prolation for up to 3 months post-operation. Surgeons are thus advised to re-evaluate refraction and defer contact lens refitting, refractive surgery, and intraocular lens calculations for at least 3 months after the procedure.

To Investigate the Changes in Corneal Curvature and Its Correlation with Corneal Epithelial Remodeling After Trans-PRK and FS-LASIK

Purpose To evaluate curvature changes in different regions and their correlation with corneal epithelial remodeling in myopic patients undergoing femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and transepithelial refractive keratectomy (Trans-PRK) after surgery. Methods One hundred and sixty-three patients (163 right eyes) undergoing Trans-PRK and LASIK were evaluated for up to 6 months using anterior segment optical coherence tomography (OCT) to measure the epithelial thickness and corneal topography to measure corneal curvature in different areas (2 mm, 5 mm, and 7 mm). We calculated the curvature ΔK (ΔK = preoperative - postoperative), ΔK5-2 (ΔK5-2 = K5mm - K2mm), ΔK7-5 (ΔK7-5 = K7mm - K5mm), and the epithelial thickness ΔET5-2 (ΔET5-2 = ET5mm - ET2mm) and ΔET7-5 (ΔET7-5= ET7mm - ET5mm). Results Corneal curvature flattened in each region of the two groups (all p < 0.001) and gradually steepened during the follow-up period. The Trans-PRK group flattened more significantly within 2 mm and 5 mm, while the FS-LASIK group at 7 mm. Both groups of ΔK decreased over time. Both groups of ΔK5-2 and ΔK7-5 gradually decreased during the follow-up period (P5-2=0.025 and P7-5 < 0.001 for Trans-PRK, P5-2 = 0.011 and P7-5 < 0.001 for FS-LASIK). The corneal epithelium of the two groups gradually thickened during the follow-up period, with Trans-PRK significantly thickening in the central and peripheral regions and FS-LASIK in the central and paracentral regions. There is a significant correlation between the ΔK5-2 and ΔET5-2, ΔK7-5 and ΔET7-5 (all r > 0.37, p < 0.001). Conclusions All groups showed significant curvature flattening after surgery and gradually steepening during the follow-up period. The corneal epithelium thickness in both groups of 17 regions became thicker,. In contrast, Trans-PRK group showed more significant thickening to the periphery and the central 5 mm area of the FS-LASIK. This study indicates a significant positive correlation between differences in epithelial thickening in different regions and differences in curvature changes in the corresponding areas PRK, FS-LASIK, curvature, corneal epithelial thickness

Effects of orthokeratology on corneal reshaping and the delaying of axial eye growth in children

PurposeTo investigate the inhibition of myopia progression and axial elongation in children wearing orthokeratology (OK) lenses, as well as to evaluate the status of corneal reshaping, this study explores the relationship between changes in central corneal curvature (K-value) and e-value induced by OK lenses and axial elongation. MethodsIn this study, it is planned to select children aged 8–15 who wear orthokeratology lenses at the Pediatric Ophthalmology and Strabismus Clinic of the Second Affiliated Hospital of Dalian Medical University. All children will undergo slit lamp examination, visual acuity assessment, computerized refraction, intraocular pressure measurement, biometry, and corneal topography examination before lens wear and at 1 month, 3 months, and 6 months after lens wear in the pediatric ophthalmology clinic. Based on age (lower age group (8 < age ≤12 years); higher age group (12 < age ≤15 years)) and baseline equivalent spherical (SE) value (mild myopia group (−1.00 D < SE ≤ −3.25D); moderate myopia group (−3.25 D < SE ≤ −6.00 D)), four groups will be formed by pairing these factors. Suitable data will be selected according to inclusion and exclusion criteria, and different groups will be included. Data will be organized, and statistical analysis will be performed using SPSS software to obtain the results. The expected results will be discussed and analyzed. ResultsAfter wearing OK lenses, all four groups achieved good visual acuity at follow-up. At 6 months, there were no significant differences in visual acuity among the four groups (P = 0.149, >0.05). There were no significant differences in refractive error among the four groups (P = 0.066, >0.05). Baseline axial length differed significantly among the four groups (P = 0.000, <0.001), with the LM group having longer axial length than the LL group (P < 0.001, paired samples t-test), and the HM group having longer axial length than the HL group (P < 0.001, paired samples t-test). However, there were no significant differences in axial length change compared to baseline among the groups at 1 month, 3 months, and 6 months (P1 = 0.053; P3 = 0.557; P6 = 0.329, >0.05). Significant differences were observed in corneal flat K-value change compared to baseline among the four groups at 1 month, 3 months, and 6 months (P1 = 0.001, P3 = 0.001, P6 = 0.004, <0.05). There were no significant differences in e-value change among the groups at 1 and 3 months (P1 = 0.205, P3 = 0.252, >0.05), but significant differences were found in e-value change compared to baseline at 6 months (P6 = 0.010, <0.05). Multiple regression analysis with changes in central corneal flat K-value and e-value as independent variables and axial elongation as the dependent variable showed a correlation between e-value change at 6 months and axial elongation (P = 0.004, <0.05), indicating a negative correlation. ConclusionOrthokeratology (OK) lenses effectively improve myopic children's vision by reshaping the cornea, leading to reduced central corneal curvature and flattening of its anterior surface. The effectiveness of OK lenses is not significantly affected by age or initial myopia severity. Children of varying ages and myopia levels experience similar levels of axial length control with OK lens wear. Changes in corneal shape due to OK lenses affect axial elongation, with greater changes in corneal morphology associated with smaller increases in axial length.

Redistribution of Epithelium and Stroma and Their Relationship With Corneal Curvature After 1-Month Cessation of Overnight Orthokeratology.

To investigate the changes in the thickness of epithelium and stroma and their relationship with corneal curvature following the cessation of overnight orthokeratology for a period of 1 month. This prospective study consecutively included 20 juveniles (20 right eyes) who had undergone overnight orthokeratology for a minimum of one year and were willing to discontinue the treatment. The study measured and compared epithelial and corneal curvature using optical coherence tomography and Medmont topographer at the first day of cessation and 1 month after cessation. In addition, changes in uncorrected visual acuity and refractive error before and after the cessation of the treatment were analyzed. The study found a significant increase in the thickness of the epithelium in the central 2-mm area after the cessation of the treatment (t = -4.807, P <0.001). Moreover, the stroma in the paracentral area (2-5 mm) and peripheral area (5-6 mm) showed a general thinning trend ( P =0.016, P =0.016). Regarding the correlation analysis, the change in central epithelial thickness (ΔCET) was significantly correlated with the change in paracentral corneal curvature (ΔPCCC) (r=0.610, P =0.007) and the change in peripheral corneal curvature (ΔPCC) (r=0.597, P =0.009). Similarly, the change in central stromal thickness (ΔCST) was significantly correlated with the change in central corneal curvature (ΔCCC) (r=0.500, P =0.035), ΔPCCC (r=0.700, P =0.001), and ΔPCC (r=0.635, P =0.005). The study found that the corneal remodeling induced by orthokeratology was reversible after the cessation of the treatment. Specifically, changes in the epithelium were found to be more prominent in the central area, while changes in the stroma were more pronounced in the paracentral and peripheral areas. In addition, the study established a significant correlation between central corneal remodeling and changes in curvature.

Scleral lens induced short term corneal changes in eyes with Pellucid Marginal Degeneration

PurposeTo investigate the short-term effect of scleral lens (SL) on corneal curvature and corneal oedema in Pellucid Marginal Degeneration (PMD) eyes. MethodsCorneal anterior, posterior curvature and corneal thickness were measured in 14 eyes of 14 PMD participants with Schiempflug imaging at different corneal diameters and meridians at baseline and after 6 h of SL wear. ResultsThere was a significant flattening (up to 0.26 mm) of the anterior corneal curvature noted in the inferotemporal quadrant (from 210 to 255 degree at 2 mm, 8 mm and 10 mm corneal diameter), inferonasal quadrant (from 285 to 345 degree at 6 mm and 8 mm corneal diameter), and inferiorly at 2 mm and 10 mm corneal diameter (p < 0.05). Similarly, posterior corneal curvature showed statistically significant steepening mostly in inferotemporal quadrants (from 195 to 255 degree from 4 mm to 8 mm corneal diameter) and inferonasally at 2 mm and 4 mm corneal diameter (p < 0.05). A statistically significant increase in the corneal thickness noted in different corneal diameters with corneal oedema ranging from 2.10 % to 4.00 % after 6 h of SL wear. A gradual increase in corneal oedema was noted form centre to periphery. The baseline central fluid reservoir thickness (FRT) was 341.07 ± 139.8 which reduced to 276.71 ± 114.32 µm after 6 h of lens wear. No significant correlation was noted between corneal oedema with different parameters like initial and final FRT, change in anterior and posterior corneal curvature, and lens thickness (p > 0.05). ConclusionsShort-term SL wear induced a clinically acceptable range of corneal oedema. A clinically significant flattening in anterior curvature and minimal steepening in posterior curvature were noted. Practitioners should be careful while measuring corneal parameters in PMD eyes wearing SL, as these alterations can provide false impression of disease progression.

Altering optical zone diameter, reverse curve width, and compression factor: impacts on visual performance and axial elongation in orthokeratology

PurposeTo investigate the effects of modifications in back optical zone diameter (BOZD), reverse curve width (RCW), and compression factor (CF) on refractive error changes and axial elongation in myopic children undergoing orthokeratology (ortho-k) over a 12-month period. MethodIn this retrospective study, data from 126 myopic children undergoing ortho-k fitting were analyzed. Subjects were categorized into four distinct groups based on lens design parameters: Group A (BOZD 6.0 mm, RCW 0.6 mm, CF 0.75 D); Group B (BOZD 6.0 mm, RCW 0.6 mm, CF 1.25 D); Group C (BOZD 5.4 mm, RCW 0.9 mm, CF 1.25 D); and Group D (BOZD 5.0 mm, RCW 1.1 mm, CF 1.25 D). The study evaluated uncorrected visual acuity (UCVA), corneal topography, and axial length (AL) at intervals, using Linear Mixed Models (LMMs) for time-based changes, and ANOVA or Kruskal-Wallis tests for group differences in AL elongation. A multivariable regression analysis identified factors independently associated with AL elongation. ResultsWithin the first day and week, all four groups displayed significant improvements in UCVA and alterations in corneal curvature, which subsequently stabilized. Although UCVA variations between groups were subtle, Group D had less corneal curvature change than Groups A and B initially and exhibited significantly less AL elongation after one year. No significant difference in corneal curvature change or AL elongation was observed between Group C and the other groups. Multiple regression analysis indicated that older baseline age, greater baseline spherical equivalent refractive error, and smaller BOZD were associated with less AL elongation. ConclusionThe study reveals a positive correlation between BOZD and axial length growth over the 12-month period. A pure 0.5 D CF increment demonstrates a nonsignificant impact. This study provides new ideas into optimizing the parameters of ortho-k lenses.

Efficacy comparison of combining cross-linking and refractive laser ablation in progressive keratoconus: systematic review and meta-analysis

ObjectiveThis study assessed the effect of combining corneal collagen cross-linking (CXL) with refractive laser ablation techniques for the treatment of keratoconus, a progressive corneal disorder. MethodsWe performed a systematic review and meta-analysis to assess the effect of combined CXL and refractive techniques. We included all published clinical trials or observational studies published by September 1, 2023. We calculated and compared the standardized mean difference (SMD) between CXL alone and CXL plus laser ablation for uncorrected distance visual acuity, best-corrected distance visual acuity, spherical equivalent manifest refraction, sphere and cylinder, flat keratometry (K1), steep keratometry (K2), and central corneal thickness. ResultsWe identified 13 studies that fulfilled our inclusion and exclusion criteria. The average follow-up was 21.3 ± 11.8 months. The CXL plus laser ablation group showed improvement in uncorrected distance visual acuity logMAR (SMD, –0.35; 95% CI, –0.67 to –0.04; p = 0.029), best-corrected distance visual acuity logMAR (SMD, –0.17; 95% CI, –0.30 to –0.03; p = 0.014), spherical equivalent manifest refraction (SMD, –0.28; 95% CI, 0.06–0.50; p = 0.013), and change in maximal corneal curvature (Kmax; SMD, –0.41; 95% CI, –0.69 to –0.13; p = 0.004) compared with CXL alone. However, central corneal thickness decreased further among patients who underwent CXL plus laser ablation (SMD, –0.37; 95% CI, –0.66 to –0.07; p = 0.016). No effect was observed in terms of sphere (p = 0.878), cylinder (p = 0.859), K1 (p = 0.907), or K2 (p = 0.169). Ectasia was not observed as an adverse effect resulting from the additional corneal ablation performed during the CXL treatments. ConclusionsThis study showed that combining refractive laser ablation techniques with standard or accelerated CXL treatment improved visual and refractive outcomes and anterior corneal curvature values.

Intraocular lens power calculation after corneal refractive surgery

Challenges in IOL power calculation in eyes after corneal refractive surgery are caused by difficulties in accurately determining corneal refractive power and in predicting the effective lens position. Three factors contribute to inaccurate corneal refractive power estimation ‐ inaccurate measurement of anterior corneal curvature by standard keratometry or corneal topography, inaccurate calculation of total corneal power from the anterior corneal curvature can result from using the standardized value for the refractive index of cornea (1.3375) and finally changes in posterior corneal curvature. There are three categories of methods proposed based on the use of historical data acquired prior to the corneal refractive surgery (formulas using only historical data, no historical data or a combination of historical data and current data). The most frequently used methods of IOL power calculation in eyes after corneal refractive surgery are discussed and their accuracy are compared. The latest studies and meta‐analyses in this area are presented. Despite availability of new measurement technologies and development of new IOL calculation formulas, further advances are needed to improve outcomes of cataract surgery in eyes that have undergone corneal refractive surgery.

COVID-19 related changes in corneal curvature and endothelium after mild infection

PurposeTo investigate subclinical corneal changes using corneal topography in the evaluation of corneal curvature and specular microscopy in the evaluation of the endothelial layer after mild coronavirus disease 2019 (COVID-19). MethodsIn this prospective study, 112 eyes of 56 individuals with mild COVID-19 who recovered were investigated. Mean cell density (CD), mean coefficient of variation (CV), mean percentage of hexagonal cells, mean cell area (AVG), and central corneal thickness (CCT) were recorded from specular microscopy. K readings, including simulated keratometry flat (K1), simulated keratometry steep (K2), average keratometry (Kmean) and maximum keratometry (Kmax), pachymetric measurement and central corneal thickness (CCT), corneal volume (CV), topographic astigmatism (TA), curvature asymmetry front (CAf) and curvature asymmetry back (CAb) were recorded from corneal topography. Best corrected visual acuity (BCVA), spherical equivalant and biometric measurements were recorded. ResultsThe mean time interval between examinations before and after COVID-19 infection was approximately one year. Analysis of specular microscopy data showed a statistically significant change in all endothelial cell parameters (p<0.001) except the cell count (p = 0.358). The median (range) endothelial cell density (ECD) value was significantly lower after COVID-19 at 2356 (2289–2400) than before, when it was 2596 (2545–2640). Furthermore, CCT values showed a significant increase (p<0.001). The topographic values including K2, Kmax and TA and biometric measurements did not change. The Spherical Equivalant (SE) values showed significant myopic progression after COVID-19 (p<0.001). ConclusionEndothelial parameters changed more than the changes in corneal curvature and ocular biometric measurements after mild COVID-19. The decrease in endothelial cell number and hexagonality and increase in polymorphism after COVID-19 were striking.

Changes in the Ocular Biometric Measurements of Korean Children with Myopia and Hyperopia

Purpose: To document changes in the optical coherence biometry data over 1 year of Korean children aged 6 to 9 years with myopia and hyperopia.Methods: We used fluorescein angiography to retrospectively study changes in refractive errors over 1 year in 60 children who visited our hospital between December 2019 and June 2022. The IOL master 700 platform was used to derive axial length, corneal curvature (the K value), central corneal thickness, anterior chamber depth, lens thickness, and the white-to-white size at 1-year intervals. The Mann-Whitney and Wilcoxon signed-ranked tests were used to compare the values. A p-value &lt; 0.05 was taken to indicate a significant difference.Results: The mean ages of hyperopic and myopic children were 6.27 ± 0.87 and 6.93 ± 0.87 years at initial presentation. Significant 1-year changes in axial length, anterior depth, and lens thickness were apparent. The mean corneal curvature, and central corneal and lens thicknesses were significantly higher in hyperopic than myopic children but the axial length and anterior chamber depth were significantly greater in myopic children. However, after 1 year, the lens thicknesses did not significantly differ between the two groups.Conclusions: Over 1 year of early life, changes in the mean corneal curvature and lens thickness were significant in hyperopic children and changes in the axial length and anterior depth were significant in myopic children. Thus, the eye growth pattern may differ between hyperopic and myopic children.

Does Corneal Topography Using 3-Dimensional Optical Coherence Tomography Suggest Different Subtypes of Terrien Marginal Degeneration?

The aim of this study was to analyze corneal topography relative to astigmatism, higher order aberrations, and corneal curvatures in Terrien marginal degeneration using 3-dimensional anterior-segment optical coherence tomography. Twenty-nine eyes of 15 Finnish patients from a tertiary referral center had topographic axial power maps classified into 4 patterns by visual grading: crab claw (CC), mixed (M), arcuate (A), and normal. Regular astigmatism, keratometry, higher order aberrations, maximal corneal thinning, apex thickness, and curvature changes relative to best fit sphere toward maximal peripheral thinning were compared. Four, 9, and 12 eyes were classified as CC, M, and A, respectively; 1 as normal with clinical disease; and 3 as normal with unilateral disease. Median follow-up was 2.3 (range, 0-7.2) years. Three eyes changed pattern. Patients with the CC pattern were the youngest when diagnosed, progressed more rapidly, exhibited cavities in superior quadrants with anterior bulging, and had greater higher order posterior aberrations. Patients with the M pattern were older, progressed slower, and showed superonasal asymmetric corneal steepening extending centrally, often with asymmetric bow tie. Patients with pattern A showed little progression and were the oldest when diagnosed, with maximal corneal thinning equally in all quadrants. According to the Wang classification, the median stage was 4, 2, and 2 in CC, M, and A patterns, respectively, whereas it was always 2 by the Süveges classification. Terrien marginal degeneration is characterized by distinct corneal topographic patterns that differ in tomographic features, suggesting existence of subtypes in addition to different stages of disease. Patients representing CC and M patterns might benefit from more frequent monitoring.

Orthokeratology in controlling myopia of children: a meta-analysis of randomized controlled trials

BackgroundDelaying the development and lowering the progression of myopia in children is the focus of current ophthalmology researches. We aimed to evaluate the role of orthokeratology in controlling myopia of children, to provide insights to the clinical treatment and care of children with myopia.MethodsTwo investigators searched the The Cochrane Library, Embase, Pubmed, China national knowledge infrastructure, China biomedical literature database, WanFang and Weipu databases for randomized controlled trials(RCTs) on the role of orthokeratology in controlling myopia of children up to November 5, 2022. Two researchers independently searched, screened and extracted the studies according to the inclusion and exclusion standards. RevMan5.3 software was used for statistical analysis.ResultsA total of 14 RCTs involving 2058 children were included in this meta-analysis. Synthesized outcomes indicated that orthokeratology improved the uncorrected visual acuity(MD = 0.40, 95%CI: 0.05 ~ 0.74), reduced the diopter change(MD=-3.19, 95%CI: -4.42~-1.95), changes of corneal curvature(MD=-3.21, 95%CI: -3.64~-2.79), the length of ocular axis (MD=-0.66, 95%CI: -1.27~-0.06) and amount of ocular axis change(MD=-0.42, 95%CI: -0.64~-0.21) after 1 year of wearing orthokeratology(all P < 0.05). Besides, orthokeratology reduced the diopter change (MD=-3.22, 95%CI: -4.86~-1.58), the length of ocular axis (MD=-1.15, 95%CI: -2.25~-0.06) and the amount of ocular axis change after 2 year of wearing orthokeratology (MD=-0.53, 95%CI: -0.96~-0.11) after 2 year of wearing orthokeratology (all P < 0.05). No publication biases were found amongst the synthesized outcomes (all P > 0.05).ConclusionsOrthokeratology delays the progression of myopia in children, the long-term effects of orthokeratology need further investigations in future studies.

Posterior keratometry changes after steep axis phacoemulsification: a prospective study.

Purpose: To measure changes in posterior corneal curvature after steep axis phacoemulsification and investigate the possibility of its effect on SIA. Methods: This was a prospective longitudinal study on 60 consecutive eyes of age-related cataract with regular astigmatism and absence of co-morbidities undergoing uneventful cataract surgeries with main incision at steep meridian. Preoperative and 4 weeks postoperative measurements of anterior and posterior corneal curvatures using Scheimpflug based corneal topographer were performed. Posterior corneal curvature was assessed at 3, 5- and 7-mm diameters. Results: The study found a statistically significant change in posterior corneal K1, K2 and mean astigmatism in all zones (3, 5 and 7 mm) at 4 weeks postoperative, when compared to preoperative readings. Conclusion: Posterior keratometry is likely to be an important determinant of Surgically Induced Astigmatism (SIA) and should be factored in for refractive cataract surgery.

Depth-resolved reconstruction of anisotropic elastic moduli in a crosslinked cornea with wave-based optical coherence elastography

Ectatic changes in the cornea are typically marked by corneal thinning with increased corneal deformation and curvature, often leading to high levels of myopia and irregular astigmatism. The most common form of ectasia is keratoconus. Corneal collagen crosslinking (CXL) is commonly used to prevent or treat keratoconus. Limited penetration of CXL into the cornea may lead to a demarcation between treated and untreated regions, suggesting a two-layer structure after the treatment. Although corneal topography can be used to monitor corneal curvature changes pre- and post-surgery, it cannot predict surgical outcomes without mapping corneal elasticity. Recent studies in non-contact dynamic optical coherence elastography (OCE) demonstrated promise in quantifying changes in corneal anisotropic stiffness induced by CXL. However, depth dependent reconstruction of corneal elastic moduli following CXL remains challenging. Here, we show that the thickness of the crosslinked corneal layer can be determined from structural OCT, whereas its mechanical moduli can be reconstructed from acoustic micro-tapping (AuT) OCE using an analytical two-layer model of guided wave propagation. In addition, we discuss how the elastic moduli of partially CXL-treated cornea layers reflect the effective engineering stiffness of the entire cornea to properly quantify corneal deformation.

Investigation of ocular biometry in 4– to 9-year-old Chinese children

PurposeTo investigate the distribution and changes in ocular biometry in 4-to to 9-year-old Chinese children and to compare the differences between age and genders in these parameters.MethodsThis was a school-based cross-sectional study. A total of 1,528 Chinese children, aged 4–9 years, from one primary school and 12 kindergartens, were included in the study. Axial length, corneal curvature, anterior chamber depth, and corneal diameter were measured for each child.ResultsAL and anterior chamber depth gradually increased with age in both genders. No significant changes in corneal curvature or corneal diameter were detected at different ages in either genders group. The mean ALs of males and females were 22.94 ± 0.80 mm and 22.38 ± 0.79 mm, respectively. The mean corneal curvatures of males and females were 43.05 ± 1.37 D and 43.75 ± 1.48 D, respectively. The mean anterior chamber depth of males and females were 3.47 ± 0.24 mm and 3.38 ± 0.25 mm, respectively. The mean corneal diameter of males and females were 12.08 ± 0.43 mm and 11.94 ± 0.44 mm, respectively. Females had consistently shorter ALs, shorter anterior chamber depth, smaller corneal diameter, and steeper corneal curvatures than males at any age.ConclusionsBoys had larger dimensions than girls for all ocular parameters except corneal curvature (flatter). Boys and girls showed similar trends for all parameters. Axial length and anterior chamber depth increased from 4 to 9 years of age, whereas corneal diameter and curvature did not change with age in either genders.

Comparison of Changes in Corneal Thickness and Curvature After Myopia Correction Between SMILE and FS-LASIK.

To comparatively investigate the changes in corneal thickness and curvature between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Data were collected preoperatively and postoperatively at 1 week, 1 month, and 3 months, including central corneal thickness (CCT), midperipheral corneal thickness (MPCT), peripheral corneal thickness (PCT), central keratometry (CK), midperipheral keratometry (MPK), and peripheral keratometry (PK), using a dual rotating Scheimpflug analyzer. At 1 week postoperatively, changes in CCT, MPCT, PCT, and PK were significantly greater in the SMILE group than in the FS-LASIK group (P = .003 for CCT and < .001 for MPCT, PCT, and PK), but no significant inter-group differences were found between changes in CK and MPK (P = .883 and .513, respectively). CCT, MPCT, and PK values showed a similar increase in both groups, but significantly more increase in PCT and significantly less increase in CK and MPK was observed in the SMILE group from 1 week to 3 months after surgery. At 3 months postoperatively, CCT and MPCT were significantly thinner in the SMILE group than in the FSLASIK group (P = .018 and .022, respectively), and there was no significant difference in PCT, CK, MPK, and PK between the two groups. SMILE caused significantly more corneal thinning at the center, midperiphery, and periphery, and more corneal flattening at the periphery, compared to FS-LASIK. A different pattern of corneal remodeling was observed between the two surgeries during the 3-month follow-up period. [J Refract Surg. 2023;39(1):15-22.].

Change in Stromal Thickness and Anterior Curvature After Refractive Corneal Lenticule Extraction With the CLEAR Application

To measure the changes in stromal thickness and anterior corneal curvature after corneal lenticule extraction for the correction of myopia and myopic astigmatism with the Corneal Lenticule Extraction for Advanced Refractive correction (CLEAR) application (Ziemer Group). The correlations between achieved correction on maximum myopic meridian and stromal thinning and spherical equivalent of achieved correction and anterior corneal flattening were evaluated by optical coherence tomography 6 months after CLEAR in 78 eyes of 78 patients in a retrospective, consecutive, non-comparative case series study. With an optical zone of 6.5 mm (52 eyes), the mean correction achieved was -5.80 ± 1.52 diopters (D) (range: -2.25 to -9.25 D), the mean stromal thinning was 104 ± 15 µm (range: 76 to 138 µm), and the regression line was: µm of thinning = 8.46 • D of correction + 55.25. With an optical zone of 6 mm (26 eyes), the mean correction achieved was -8.33 ± 1.61 D (range: -5.50 to -11.00 D), the mean stromal thinning was 114 ± 12 µm (range: 93 to 144 µm), and the regression line was: µm of thinning = 6.35 • D of correction + 60.92. With 6.5 mm, the mean corneal flattening was 4.27 ± 0.88 D, and the regression line was: D of flattening = 0.50 • D of correction + 1.60. With 6 mm, the mean corneal flattening was 6.40 ± 0.70 D, and the regression line was: D of flattening = 0.37 • D of correction + 2.36. Stromal thinning and anterior corneal flattening were correlated with the amount of myopic correction in a linear fashion. The thinning was significantly less than predicted by the laser software. [J Refract Surg. 2022;38(12):797-804.].

The effect of different thickness scleral lens on corneal parameters in eyes with keratoconus.

To investigate the impact of different-thickness scleral lenses (SLs) on corneal thickness, curvature, and fluid reservoir thickness in keratoconic eyes. Schiempflug imaging and AS-OCT was captured before and immediately following 6 h of SL wear. Different-thickness lenses were used while keeping the other parameters the same. The timing of the measurement for day 1 and day 2 was matched to allow for the control of the confounding influence of diurnal variation. Immediately after 6 h of lens wear, no statistically significant difference (P > 0.05) was noted in corneal edema in any region and quadrants between thin- and thick-lens wearers. The calculated percentage of corneal edema was also within the range of overnight closed eye physiological swelling. Pentacam measured higher central corneal thickness compared to AS-OCT in both baselines and after 6 h of lens wear. The current investigation reported minimal but not statistically significant (P > 0.05) flattening in anterior and steepening in posterior curvature parameters in both thin and thick SLs. The mean reduction in the fluid reservoir thickness was 80.00 ± 3.99 and 79.36 ± 3.84 microns after 6 h of thin- and thick-lens wear, respectively, which was not statistically significant (P > 0.05). A statistically significant positive correlation (r = 0.67, P = 0.02) was found between lens thickness and change in anterior steep k with thick-lens wear. Central lens thickness of 200-400 μm did not cause any significant change in corneal curvature and fluid reservoir thickness and did not induce clinically significant corneal edema after short-term SL wear.

Regional Changes in Posterior Corneal Surface During a 6-Month Follow-up Period After tPRK, FS-LASIK, and SMILE.

To investigate changes in corneal curvature in different zones of the posterior corneal surface during a 6-month follow-up period after transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted excimer laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). The study included a total of 202 eyes, including 65, 77, and 60 that underwent tPRK, FS-LASIK, and SMILE, respectively. Elevation data for the posterior surface were obtained preoperatively (pre), as well as 1 week (pos1w), 1 month (pos1m), 3 months (pos3m), and 6 months (pos6m) postoperatively. Changes in posterior corneal curvature (M) were analyzed in the central (diameter: 0 to 3 mm), paracentral (diameter: 3 to 6 mm), and peripheral (diameter: 6 to 9 mm) regions. Over all follow-up periods, the central region of the posterior surface in all patients became flatter (P < .05), with FS-LASIK showing the largest change, whereas the paracentral and peripheral regions became steeper. The posterior curvature changes between pre and pos6m, determined before and after correction for ablated stromal depth, tended to follow similar trends in the three regions and after the three surgeries. There was also no significant correlation (P > .05) between the changes in the mean curvature (M, recorded between pre and pos6m) and each of the refractive error corrections, the changes in spherical aberration postoperatively, the optical zone diameter, ablated stromal depth, and residual stromal bed thickness in the central and peripheral regions, but the correlation was significant in the paracentral region. The postoperative changes in posterior corneal shape followed different trends in the central, paracentral, and peripheral regions. The FS-LASIK group exhibited the most notable changes in posterior corneal curvature, especially in the central region. These changes were statistically correlated with variations in spherical aberration, and ablated and residential stromal thickness in the paracentral region. [J Refract Surg. 2022;38(11):708-715.].