Flat Keratometry Research Articles

Topographic corneal changes in children with moderate to severe blepharokeratoconjunctivitis.

Purpose To determine the corneal topographic characteristics of children with blepharokeratoconjunctivitis (BKC), a chronic inflammatory ocular surface disease involving the lid margin, conjunctiva, and cornea. Methods The corneal topography of 21 children diagnosed with BKC between March 2008 and June 2019 at a single institution were reviewed retrospectively. Pachymetry and asymmetry indices were also analyzed. Results Mean flat keratometry (K1), steep keratometry (K2), maximum keratometry (Kmax), and topographic astigmatism (TA) were 42.61 ± 2.63 D, 46.00 ± 3.17 D, 51.00 ± 5.29 D, and 3.39 ± 2.60 D, respectively. Mean central corneal thickness (CCT) was 528.8 ± 72.2 μm; mean thinnest point (TP) was 487.00 ± 88.28 μm; 47% of eyes had a TP of <500 μm. Compared with previously published pediatric normative values, K2, Kmax, and TA were significantly higher (46.00 ± 3.17 vs 45.16 ± 0.27, 51.00 ± 5.29 vs 45.76 ± 0.28, and 3.38 ± 2.48 vs 2.81 ± 0.19 [P < 0.0001]), whereas mean CCT and TP were significantly lower in the BKC group. 72.2% of cases fulfilled the Rabinowitz diagnostic criteria for ectasia: 67% had a Kmax >47.2 D and 31% had an inferior-superior asymmetry value >1.2 D. Using topography-derived indices comparing the superior and inferior corneal characteristics, the index of height decentration, index of surface variance, and index of vertical asymmetry were found to be abnormal in 83%, 69%, and 64% of cases, respectively. Conclusions Children with moderate-to-severe BKC may present with significant topographic corneal changes that can mimic corneal ectasia. Corneal topography could be an important tool in evaluating corneal involvement and explaining reduced visual function due to refractive changes.

Comparison of Toric Intraocular Lens Axis Accuracy between Optical Biometry and Dual Scheimpflug Topography.

To evaluate the accuracy of toric intraocular lens (IOL) axis prediction between two preoperative measurement devices: the optical biometry (IOLMaster 500 or 700) and the dual Scheimpflug topography (Galilei G4). Medical records of 64 eyes from 44 patients who underwent phacoemulsification and posterior chamber toric IOL (Zeiss AT TORBI 709M) implantation between July 2017 and January 2022 were reviewed. All patients underwent preoperative evaluation by optical biometry (IOLMaster 500 or IOLMaster 700) and Galilei G4. The gold-standard axis that minimizes astigmatism was calculated by the online Toric Results Analyzer postoperatively and compared to the preoperative toric IOL axis calculated by the Z CALC online IOL calculator using parameters from either IOLMaster or Galilei G4. The axis error (AE) and the absolute axis error (AAE) between the gold-standard axis and the preoperative calculated axis were analyzed to assess the accuracy of each device. Mean flat keratometry (K) and steep K were 42.99 diopter (D) and 45.61 D in IOLMaster, and 43.04 D and 45.51 D in Galilei G4, which did not show any significant difference. Mean keratometric astigmatism (KA) was 2.62 D in IOLMaster and 2.46 D in Galilei G4, which also did not show any statistical difference. KA axis did not show any significant difference between IOLMaster and Galilei G4. The mean AE and AAE were 0.19° and 6.84° by IOLMaster, and -0.80° and 7.98° by Galilei G4. The AE and AAE by IOLMaster did not show any significant difference compared to those of Galilei G4 (p=0.583, p=0.346, respectively). This study suggests that the Galilei G4 demonstrated a similar level of accuracy to the IOLMaster in predicting the toric IOL axis, based on the gold standard axis provided by the toric results analyzer.

A study on the variability and correlation of ocular biological measurement parameters in adult myopic patients.

This study aims to explore the differences in ocular parameters among adult myopic patients with different degrees of myopia and axial lengths, and to investigate the correlations between these ocular parameters. This single-center observational study collected clinical data from myopic patients aged 18-45 years who visited the Eye Hospital of Nanjing Medical University between January and June 2023. The data included laterality, diopter of spherical power (DS), diopter of cylindrical power (DC), spherical equivalent (SE), axial length (AL), central corneal thickness (CCT), flat meridian keratometry (K1), steep meridian keratometry (K2), mean keratometry (Km), anterior chamber depth (ACD), corneal radius of curvature (CRC), and axial length/corneal radius of curvature ratio (AL/CRC). Following predefined inclusion and exclusion criteria, 1,026 eyes were included in the study. Patients were grouped based on SE and AL parameters into different degrees of myopia. Analysis of variance (ANOVA) and Welch ANOVA were used to compare intergroup differences. Spearman correlation coefficients were calculated to analyze the correlations between parameters, and linear regression and ROC curve analyses were performed. Significant differences (p < 0.05) were found among mild, moderate, and high myopia groups in parameters such as DS, DC, AL, K1, Km, ACD, CRC, and AL/CRC. Significant differences (p < 0.05) were also found in DS, DC, SE, CCT, K1, K2, Km, ACD, CRC, and AL/CRC among different axial length groups. Spearman correlation analysis showed a strong correlation between AL and DS, SE, and between AL/CRC and DS, SE, AL. Linear regression analysis revealed that the coefficient of determination (R2) for AL and SE was 0.699, and for AL/CRC and SE, it was 0.861. ROC curve analysis demonstrated high accuracy for both AL and AL/CRC in identifying high myopia, with an AUC of 0.952 for AL/CRC, which was superior to the AUC of 0.905 for AL (p < 0.05). This study found significant differences in ocular parameters among patients with different degrees of myopia and axial lengths. There was a significant negative correlation between AL, AL/CRC, and SE. Compared to AL, AL/CRC had a stronger correlation with SE and higher accuracy in identifying high myopia.

Repeatability of pentacam AXL in determining axial length and ocular indices in people with irregular cornea

Aims/Purpose: To determine the repeatability of Pentacam AXL in determining ocular axial length and some corneal indices in people with irregular corneas.Methods: Ocular biometry using Pentacam AXL underwent in this study. The Pentacam AXL measurements were done 3 times 10‐minutes apart. To evaluate the repeatability, the intraclass correlation coefficient (ICC), were calculated.Results: In this study, 141 eyes of 141 individuals with irregular cornea aged 60 to 91 years (64 ± 15.7) were included. The ICC of axial length, flat keratometry, steep keratometry, anterior chamber depth, central corneal thickness and corneal diameter measurements were 0.957, 0.981, 0.989, 0.980, 0.923 and 0.981 respectively. In cases with long axial length (&gt;24.5mm) the ICC of axial length, flat keratometry, steep keratometry, anterior chamber depth, central corneal thickness and corneal diameter measurements were 0.427, 0.946, 0.993, 0.988, 0.861 and 0.989 respectively.Conclusions: The results of this study showed that generally Pentacam AXL has a high repeatability in measuring the axial length and some corneal indices of the eye in irregular corneas. However, it should be note that Pentacam AXL has no repeatability in irregular corneas with long axial length.

Distribution and associated factors of keratometry and corneal astigmatism in general elderly population

Purpose: To determine the distribution and associated factors of keratometry and corneal astigmatism in people aged 60 years and above.Methods: In this cross‐sectional study, 160 clusters were randomly selected from Tehran city (Iran) using the multi‐stage cluster sampling method. All participants underwent optometric examinations including testing uncorrected and best‐corrected distance visual acuity, non‐cycloplegic autorefraction, and subjective refraction. Pentacam imaging for all participants was carried out using Pentacam AXL. Keratometry and corneal astigmatism were reported based on Pentacam's data.Results: 4244 eyes from 2268 individuals were analyzed. The average, standard deviation and 95% confidence interval of flat keratometry, steep keratometry, mean keratometry, and corneal astigmatism were 44.02±1.58 diopters (95% confidence interval: 43.94 to 44.1), 44.86±1.67 diopters (95% confidence interval: 44.78 to 44.94), 44.44±1.58 diopters (95% confidence interval: 44.36 to 44.52), and 0.84±0.74 diopters (95% confidence interval: 0.81 to 0.87), respectively. According to the multiple generalized estimating equation model, the mean keratometry was significantly higher in males, in myopes, and in those with higher systolic blood pressure. Moreover, the mean keratometry was inversely related to the axial length, height, anterior chamber depth, corneal diameter, and central corneal thickness. The prevalence of various types of corneal astigmatism &gt; 0.50 diopters was as follows; with‐the‐rule: 32.5%, against‐the rule: 18.2%, and oblique: 10.0 %.Conclusions: The present study investigated the normal distribution of keratometry and corneal astigmatism in elderly, and results can be used in clinical matters, especially in intraocular lens power calculation. Sex and some biometric components such as anterior chamber depth, corneal diameter, and central corneal thickness are significantly related to keratometry.

Corneal topographic and aberrometric changes in patients with acquired blepharoptosis after levator resection surgery

Objective: To evaluate changes in corneal topography and aberrometry in patients with acquired blepharoptosis after levator resection surgery. Methods: This prospective, interventional study evaluated 30 eyelids of 19 patients who underwent levator resection surgery for acquired blepharoptosis with fair and good levator function (LF). Patients underwent corneal topography before and 3 months after surgery. Results: Eleven patients had bilateral, and 8 patients had unilateral surgery. There were significant decreases in steep keratometry (K2) (preoperative: 46.21±5.02, postoperative: 44.58±2.11, P=0.046) and corneal astigmatism (preoperative: 2.98±0.61, postoperative: 1.59±1.50, P=0.034). There were no statistically significant differences between the preoperative and postoperative values of flat keratometry (K1) (P=0.585), mean keratometry (Kmean) (P=0.122), axis of corneal astigmatism (P=0.548), central corneal thickness (P=0.350), anterior chamber depth (P=0.747) and anterior chamber volume (P=0.679). The root mean square (RMS)-higher order aberrations (HOA) (P&amp;lt;0.001), RMS-Coma (Z₃¹) (P&amp;lt;0.001), and RMS-Trefoil (Z₃³) (P=0.005) decreased significantly. Preoperative and postoperative values of the seconder astigmatism (P=0.345), RMS-spherical aberration (Z₄⁰) (P=0.255), and RMS-Quadrafoil (Z₄⁴) values were found similar. Conclusions: Levator resection for acquired blepharoptosis can improve the topography and aberrometry measurements of the cornea 3 months after surgery.

Characteristics of corneal aberration in patients with bilateral keratoconus and unilateral corneal Vogt's striae.

To assess the corneal high-order aberration (HOA) and its correlation with corneal morphological parameters in patients with bilateral keratoconus (KCN) and unilateral Vogt's striae. A total of 168 eyes of 84 patients with KCN, whose corneas had definite signs of unilateral Vogt's striae, were enrolled. Corneal HOA and morphological parameters were measured using Pentacam HR. The corneal morphological parameters between KCN eyes with and without Vogt's striae were evidently different (P<0.001). The 3rd coma 90°, 4th spherical aberration, 5th coma 90°, root-mean-square (RMS) (total), and RMS (HOA) in the front, back surfaces and total cornea in KCN eyes with Vogt's striae were significantly higher than those in KCN eyes without Vogt's striae (P<0.001). In KCN eyes with Vogt's striae, the 3rd coma 90° and 4th spherical aberration in the front surface and total cornea were negatively correlated with flat keratometry value (K1), steep keratometry value (K2), mean keratometry value (Km), maximum keratometry value (Kmax), anterior corneal elevation (ACE), and posterior corneal elevation (PCE; P<0.05). The 3rd coma 90°, 4th spherical aberration in back surface and RMS (total), RMS (HOA) in the front, back surfaces, total cornea were positively correlated with K1, K2, Km, Kmax, ACE, and PCE (P<0.05). Corneal HOA especially vertical coma and spherical aberration may increase when Vogt's striae appeared in KCN eyes. The scale of increase is significantly related with changes in corneal shapes.

Repeatability and Agreement of Anterion with Pentacam HR and Orbscan II in Corneal Parameters after Photorefractive Keratectomy

Introduction: This study aimed to evaluate the repeatability and agreement of Anterion with Pentacam HR and Orbscan II in corneal parameters after photorefractive keratectomy (PRK). Methods: This prospective study involved 42 patients (42 eyes) aged between 20 and 40 years undergoing PRK surgery. Corneal measurements were measured two times using Anterion in order to assess the repeatability of this device. Then, the same parameters were measured using Pentacam and Orbscan in order to determine the agreement of Anterion and the other two devices in measuring corneal parameters after PRK. Intraclass correlation coefficient (ICC) checked Anterion’s repeatability. Also, ICC and means of the 95% limits of agreement (LoA) were used to assess the agreement of Anterion results with those of the two other devices. Results: Anterion demonstrated high to moderate repeatability in corneal parameters post-PRK, except for anterior flat keratometry (ICC = 0.73), 4th order root mean square (RMS), and horizontal trefoil (ICC &lt; 0.75). While Anterion and Pentacam showed good agreement in corneal topography and tomography (ICC &gt; 0.90, P &lt; 0.05), they were only interchangeable in keratometric parameters. Additionally, no agreement was observed between Anterion and Pentacam in aberration parameters after PRK. Although Anterion and Orbscan exhibited agreement in anterior average keratometry and central corneal thickness (CCT) (ICC &gt; 0.90, P &lt; 0.05), it was not clinically interchangeable. Conclusion: Anterion demonstrated notable repeatability in most corneal parameters after PRK. Although there was good agreement between Anterion and Pentacam HR in measuring corneal topography and tomography, their interchangeability was limited to other values. Furthermore, Anterion and Orbscan II were not clinically interchangeable.

Correlation analysis between myopia growth and physical development parameters of school-age children in Shihezi area, Xinjiang Uyghur Autonomous Region

Objective: To study the correlation between myopia growth and physical development of primary school student in Shihezi area of Xinjiang Uyghur Autonomous Region by measuring the ocular biometry and physical parameters of the eye, and to provide an objective basis for the development of myopia prevention and control. Methods: A cross-sectional study design was used. The Grade 1-6 students from 33 schools in Shihezi area were randomly selected in October 2023. The children were classified according to age into the low age group (6-9 years) and the high age group (10-13 years).The children's height, weight, axial length (AL), maximum keratometry (steepest keratometry, K1), and minimum keratometry (flattest keratometry, K1) were measured. The body mass index (BMI), keratometric astigmatism (ΔK), mean keratometry (K), corneal radius (CR) and AL/CR were calculated. Correlation analyses were performed between ocular biometry and physical parameters. LASSO regression analysis was used to screen the best variables, and linear regression models were constructed after adjusting for confounding factors of age and sex. Results: A total of 3 986 children aged 6-13 years were included in this study, including 2 094 boys (52.53%) and 1 892 girls (47.47%); 2 162 in the lower age group and 1 824 in the upper age group. Girls had higher K, ΔK and AL/CR values than boys (43.38 D vs 42.7 D, t=-7.84,P<0.01; 1.1 D vs 1.01 D, t=-2.14,P=0.03; 2.97 vs 2.96, t=3.32,P=0.02). Boys had higher AL, height, weight and BMI than girls (23.47 mm vs 23.02 mm, t=13.77,P<0.01; 1.34 m vs 1.33 m, t=3.02,P=0.03; 32 kg vs 29.5 kg, t=7.82,P<0.01; 17.4 vs 16.52, t=10.36, P<0.01). LASSO regression was used to screen the 3 physical parameter variables (height, weight, and BMI) to determine that height was the best physical parameter variable for AL/CR. After adjusting for confounders, it was shown that in the low age group (6-9 years), there was a significant positive correlation between children's height and AL/CR (b=0.174, 95%CI: 0.106 to 0.241, P<0.001), whereas in the high age group (10-13 years), there was no correlation between children's height and AL/CR (b=0.086, 95%CI:-0.038 to 0.21, P=0.174). Conclusion: There was a positive correlation between height and myopia growth in the lower age group of children in Shihezi area, Xinjiang Uyghur Autonomous Region; there was no correlation between height and myopia growth in the higher age group.

Effects and safety of combined corneal collagen crosslinking and intrastromal corneal ring segment treatment in patients with keratoconus: a retrospective study

PurposeTo evaluate the safety and efficacy of different time-point combinations of intrastromal corneal ring segment (ICRS) implantation using femtosecond technology) and corneal collagen crosslinking (CXL) for the treatment of moderate-to-severe keratoconus (KCC).MethodsThis study included 69 eyes of 69 patients with keratoconus who underwent ICRS and CXL treatment at an Eye Hospital between March 2020 and March 2023. The patients were divided into two groups: Group 1 (n = 33 eyes of 33 patients), which received ICRS and CXL treatment in one session, and Group 2 (n = 36 eyes of 36 patients), which included treatment with ICRS for at least 6 months following CXL application. Preoperative and postoperative evaluations included visual acuity, autorefractometer refraction, corneal tomographic measurements using the Sirius (CSO) Scheimpflug camera and the TONOREF™ III device, and documentation of observed complications. Uncorrected visual acuity (UCVA) and best-corrected spectacle visual acuity (BCVA) were measured in each eye individually, and visual acuity was assessed using the logarithm of the minimum angle of resolution (logMAR).ResultsIn Group 1, mean UCVA improved from 0.81 ± 0.34 to 0.45 ± 0.25 (p < 0.01), and mean BCVA improved from 0.76 ± 0.35 to 0.38 ± 0.20 (p < 0.01). In Group 2, mean UCVA improved from 0.71 ± 0.32 to 0.43 ± 0.30 (p < 0.01), and mean BCVA improved from 0.65 ± 0.25 to 0.31 ± 0.23 (p < 0.01). Both groups showed significant reductions in manifest spherical and cylindrical refraction (p < 0.01). Group 1 exhibited greater reductions in maximum keratometry (Kmax), flat keratometry (K1), steep keratometry (K2) (p < 0.05), and astigmatic aberration compared with group 2 (p < 0.01). The use of simultaneous or separate CXL and ICRS does not significantly increase the incidence of complications.ConclusionsBoth combined and separate CXL and ICRS treatments resulted in significant improvement in UCVA and BCVA and reduced manifest refraction. Although improvements were observed in groups 1 and 2 in terms of K1, K2, and Kmax at 6 months, the improvements were more pronounced in Group 1. These results highlight the potential benefits of simultaneous ICRS + CXL treatment and underscore the importance of optimising the timing of CXL treatment to achieve the best visual outcomes.

Observations on relative peripheral refraction in Chinese adults with myopia based on a novel application of multispectral refraction topography

In this population-based observational cross-sectional study, we investigated retinal peripheral refraction in Chinese adults with myopia. We categorized 1511 Chinese adults with myopia (18 − 55 years) into low (LM), moderate (MM), and high myopia (HM) groups. Axial length, central corneal thickness, steep keratometry, flat keratometry, and intraocular pressure were measured. Refractive difference values (RDVs) for different eccentricities (RDV0–53) and the superior (RDV-S), inferior (RDV-I), temporal (RDV-T), and nasal (RDV-N) retinal regions were measured using multispectral refractive topography. The hyperopic defocus was higher for the MM group than for the LM group in RDV20–53, RDV-S, and RDV-T and HM group in RDV20–53, RDV-S, RDV-T and RDV-N. The hyperopic defocus was higher for the HM group than for the LM group in RDV20-53, RDV-S and RDV-T but lower for the LM group in RDV-N. RDV-N decreased with age (R2 = 0.0191, slope = − 0.01, p < 0.0001), whereas RDV-S (R2 = 0.0112, slope = 0.01,p < 0.0001) and RDV-T increased (R2 = 0.0038, slope = 0.01, p = 0.0160). RDV correlated with central spherical equivalent and axial length. Flat keratometry explained the most RDV variation (RDV20–30: β = 0.0714, p < 0.0001; RDV-N: β = 0.1801, p < 0.0001; RDV-S: β = 0.1426, p < 0.0001; RDV-T: β = 0.1239, p < 0.0001). Reference values for peripheral retinal defocus are provided for Chinese adults with different myopia ranges.

Comparative analysis of a novel spectral-domain OCT biometer versus swept-source OCT or OLCR biometer in healthy pediatric ocular biometry

With the advancements in ocular biometric technology, there have been significant improvements in accurately and efficiently measuring ocular parameters. The aim of this study is to compare the reliability of biometric parameters obtained using a new frequency-domain optical coherence tomography (SD-OCT) biometer with the measurements obtained from swept-source OCT (SS-OCT) and optical low coherence reflectometry (OLCR) biometers. This study employed an observational cross-sectional design. Measurements of axial length (AL), flat and steep corneal keratometry (K1 and K2), and central corneal thickness (CCT) obtained using the The Colombo IOL were compared with those obtained with the IOLMaster 700 and SW-9000 devices. The agreement were evaluated using intraclass correlation coefficient (ICC) and Bland–Altman analyses. The differences of the measurements of the three increments were assessed by one-way ANONA. 73 right eyes of 73 healthy pediatric subjects were analyzed. The AL difference measured by Colombo IOL compared with IOLmaster700 and SW-9000 were 0.00 ± 0.02 mm and − 0.07 ± 0.05 mm, respectively (P > 0.05, ANOVA). There was no statistically significant difference in CCT, K1, and K2 among the three instruments (all P > 0.05, ANOVA). The ICC values for AL, K1, K2, and CCT were 0.999, 0.996, 0.995, and 0.998, respectively. The Bland-Altman analysis showed an agreement of AL, K1, K2, and CCT with Colombo IOL and IOLMaster 700 spanned over 0.08 mm, 0.71D, 0.69D, and 12.17 μm, respectively. The agreement of AL, K1, K2, and CCT with Colombo IOL and SW-9000 spanned approximate 0.21 mm, 0.75D, 1.06D, and 14.37 μm, respectively. The new SD-OCT biometer and the SS-OCT biometer showed strong agreement in measuring AL and CCT in healthy pediatric subjects. This supports the reliability of the new SD-OCT biometer as an alternative for assessing these parameters. However, K1 and K2 could not be used interchangeably in clinical practice. Further research is needed to explore their applicability in different clinical settings and patient populations."light" />

Optical quality changes of the eye during peak SARS-CoV-2 pandemic in young adults

IntroductionTo determine whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection affects corneal morphology and optical quality. MethodsIn this cross-sectional study, ophthalmological indicators were examined during the peak of SARS-CoV-2 infection after adjusting for public health control measures. Participants were divided into control (remained uninfected), A (infected during follow-up), and B (infected prior to the first consultation) groups. Effects of varying SARS-CoV-2 infection levels were determined using reverse transcription polymerase chain reaction. Changes in corneal morphology, backscatter, and aberrations were measured. Corneal parameters, such as flat keratometry, steep keratometry, and surface variance, vertical asymmetry, height asymmetry, and height decentration indices were considered. ResultsOverall, 110 participants (208 eyes, 42.7 % male; age 17–31 years) were enrolled. Eighteen (16.3 %) were infection-free during the outbreak with unchanged corneal morphology, backscatter, and aberration. In group A, 34.73 ± 9.30 days after infection, the backscatter of the anterior corneal layer and central layer (both p = 0.000) decreased. Total low-order aberration, defocus, horizontal coma, and spherical aberration of the cornea increased (p < 0.05), while corneal morphology after infection did not change (p > 0.05). In group B, a decrease in backscattering in the corneal middle layer and an increase in horizontal coma (p < 0.05) were noted. ConclusionBackscattering of the anterior and intermediate layers of the cornea decreased and corneal aberrations increased after SARS-CoV-2 infection, which affected corneal optical quality. However, corneal morphology and thickness remained unchanged. Ophthalmological indicators and optical quality should be monitored during SARS-CoV-2 infection.

Agreement in anterior segment measurements between swept-source optical coherence and dual Scheimpflug tomography devices in keratoconus eyes

PurposeTo evaluate the agreement of ocular biometry measured using a swept-source optical coherence (Casia 2) and a dual Scheimpflug (Galilei G6) tomography in keratoconus.MethodsThis retrospective study included 102 eyes from 102 keratoconus patient examined using both devices. Parameters compared included flat (Kf) and steep (Ks) keratometry, astigmatism of anterior, posterior, and total keratometry, central (CCT) and thinnest (TCT) corneal thickness. To assess the agreement, intraclass coefficient (ICC) and Bland-Altman analysis with 95% limits of agreement (LoA) were used.ResultsAnterior and total Ks and Kf showed moderate or good agreement with 95% limits of agreement (LoA) range over 9.75 D. Posterior Ks and Kf were lower in the Galilei G6 (all p < 0.001). Astigmatism showed moderate, poor, and moderate agreement for anterior, posterior, and total keratometry, respectively. CCT and TCT showed excellent agreement; however, the 95% LoA range was over 60 μm.ConclusionThe agreement between the two devices was not excellent for most parameters used to diagnose keratoconus and assess disease progression, and the differences were clinically significant. Therefore, the measurements from these two devices are not interchangeable for patients with keratoconus.

Corneal topographic changes in thyroid eye disease

Background Thyroid eye disease (TED) causes lid retraction, extraocular muscle enlargement, and tear film changes, which can affect corneal topography. Aim To assess the corneal topographic changes associated with TED and relate these changes to disease activity and severity. Patients and methods This prospective cross-sectional case-control study was carried out on 50 eyes of 25 patients aged less than or equal to 50 years old, both sexes, diagnosed with TED and present or past serological evidence for thyroid disease (TED group). Patients were divided into two groups: the TED group: 30 eyes of 15 patients with TED and the control group: 20 eyes of 10 patients with age-matched and sex-matched without TED. Results In the TED group, axial proptosis was negatively correlated with minimal corneal thickness. Both upper and lower lid infrared meibography showed a positive correlation with axial proptosis. Active patients had considerably greater Baiocchi-Calossi-Versaci front and upper lid meibomian glands loss than inactive cases. In moderate to severe instances, upper and lower lid meibomian gland loss was much greater than in mild cases. Baiocchi-Calossi-Versaci front, Baiocchi-Calossi-Versaci back, Baiocchi-Calossi-Versaci total, and meibomian glands loss were considerably greater in TED than the control group. The TED group had significantly lower flat, steep, and average keratometry than the control group. Conclusion Corneal anterior surface flattening is the most characteristic topographic change in TED not related to disease activity or severity. TED increases meibomian gland loss, which is a major factor of ocular surface alteration in TED.

Association between Tomographic Characteristics of Pterygium and Preoperative Anterior and Posterior Topography Measured by Anterior Segment Optical Coherence Tomography.

Background: The utilities of anterior segment optical coherence tomography (AS-OCT) for characterization, differential diagnosis, postoperative monitoring, and evaluation/comparison of surgical techniques in pterygium are described. Through AS-OCT, it is also possible to study the corneal astigmatic effect of pterygium. Our purpose is to study the associations between the anatomical characteristics of pterygium and the corneal topography through AS-OCT. Methods: Fifty eyes with primary pterygium in a tertiary hospital were evaluated before surgery by measuring 10 anatomical variables of pterygium and 13 topographic variables using AS-OCT (Casia 2; Tomey Corp., Nagoya, Japan). Statistical analysis was used to study the association between them. Results: Pterygium classified as flat pattern exhibited lower preoperative values of flat keratometry (K1), real flat keratometry (K1r), average keratometry (AvgK), and real average keratometry (AvgKr) compared to nodular ones. The flat pattern showed greater cylinder (CYL) and real cylinder (CLYr) values. The horizontal corneal invasion proportionally increased CYL and CYLr. Overall, larger anatomical pterygium measurements (limbus thickness (LimbusT), central pterygium thickness (CentreT), head pterygium thickness (HeadT), epithelial thickness at 1 mm (EpitT1mm), stromal thickness at 1 mm (stromT1mm), total thickness at 1 mm (TotalT1mm), total thickness at 2 mm (TotalT2mm), and total thickness at 3 mm (TotalT3mm)) resulted in lower anterior K1, K1r, AvgK, and AvgKr, and posterior K1 and AvgK values. CentreT was greater in astigmatisms against the rule than in oblique ones. Conclusions: This study demonstrates associations between preoperative topography and the NF (nodular or flat) classification of pterygium and its anatomical measurements assessed by AS-OCT.

Comparison of measurements and calculated lens power using three biometers: a Scheimpflug tomographer with partial coherence interferometry and two swept source optical coherence tomographers

PurposeTo compare the biometric measurements obtained from the Pentacam AXL Wave, IOLMaster 700, and ANTERION and calculate the recommended intraocular lens power using the Barrett Formulae.MethodsThis was a retrospective cross-sectional study of patients who underwent biometry using the Pentacam AXL Wave, IOLMaster 700, and ANTERION. Flat keratometry (K1), steep keratometry (K2), anterior chamber depth (ACD), and axial length (AL) from each device were measured and compared. These parameters were used to calculate the recommended IOL powers using the Barrett formula.ResultsThe study included 252 eyes of 153 patients. The IOLMaster had the highest acquisition rate among the two biometers. The Pentacam obtained the shortest mean AL, the IOLMaster measured the highest mean keratometry values, and the ANTERION measured the highest mean ACD. In terms of pairwise comparisons, keratometry and axial length were not significantly different between the Pentacam-IOLMaster and ANTERION-IOLMaster groups, while the rest of the pairwise comparisons were statistically significant. In nontoric and toric eyes, 35–45% of patients recommended the same sphere of IOL power. In another 30–40%, the Pentacam and ANTERION recommended an IOL power one step greater than that of the IOLMaster-derived data. 50% of the study population recommended the same toric-cylinder IOL power.ConclusionsThe Pentacam AXL Wave, IOLMaster 700, and ANTERION can reliably provide data for IOL power calculations; however, these data are not interchangeable. In nontoric and toric eyes, 35–45% of cases recommended the same sphere IOL power, and in another 30–40%, the Pentacam and ANTERION recommended one-step higher IOL power than the IOLMaster-derived data. In targeting emmetropia, selecting the first plus IOL power is advisable when using the Pentacam and ANTERION to approximate the IOL power calculations recommended by the IOLMaster 700.

Distribution and associated factors of keratometry and corneal astigmatism in an elderly population

To determine the distribution of keratometry and corneal astigmatism (CA) and their association with demographic factors, systemic parameters, anthropometric measures, ocular biometric indices, and refractive errors in people aged 60 years and above. In this cross-sectional study, 160 clusters were randomly selected from Tehran city (Iran) using the multi-stage cluster sampling method. All participants underwent optometric examinations including testing uncorrected and best-corrected distance visual acuity, non-cycloplegic autorefraction, and subjective refraction. Pentacam imaging for all participants was carried out using Pentacam AXL. Keratometry and CA were reported based on Pentacam’s data. The average, standard deviation (SD) and 95% confidence interval (CI) of flat keratometry (Kf), steep keratometry (Ks), mean keratometry (mean K), and CA were 44.02 ± 1.58 D (95% CI 43.94–44.1), 44.86 ± 1.67 D (95% CI 44.78–44.94), 44.44 ± 1.58 D (95% CI 44.36–44.52), and 0.84 ± 0.74 D (95% CI 0.81–0.87), respectively. The 95% and 99% percentiles of mean K were 47.1 and 48.6 D, respectively. According to the multiple generalized estimating equation model, the mean K was significantly higher in males, in myopes, and in those with higher systolic blood pressure. Moreover, the mean K was inversely related to the axial length, height, anterior chamber depth (ACD), corneal diameter, and central corneal thickness (CCT). The prevalence of various types of CA based on a cut-off > 0.50 D was as follows; with-the-rule: 32.5% (95% CI 30.6–34.4), against-the-rule: 18.2% (95% CI 16.7–19.7), and oblique: 10.0% (95% CI 9.1–11.0). The present study investigated the normal distribution of keratometry and CA in individuals ≥ 60 years, and results can be used in clinical matters, especially in intraocular lens power calculation. Sex, systolic blood pressure, height, and some biometric components such as ACD, corneal diameter, and CCT were significantly related to keratometry and should be considered.

Comparison of ocular biometric parameters between two swept-source optical coherence tomography devices and Scheimpflug tomography in patients with cataract.

To assess and compare the variations and agreements across different ocular biometric parameters using swept-source optical coherence tomography (SS-OCT) and Scheimpflug tomography in patients diagnosed with cataract. This prospective case series was conducted at Tianjin Medical University Eye Hospital. In total, 212 eyes from 212 patients scheduled for phacoemulsification were included. Eyes were evaluated preoperatively using two SS-OCT devices (IOLMaster700 and CASIA2) and Scheimpflug tomography (Pentacam). Central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), white-to-white distance (WTW), flat simulated keratometry (Kf), steep simulated keratometry (Ks), mean keratometry (Km), and total corneal keratometry (TKm) were measured. Intraclass correlation coefficient (ICC), 95% confidence intervals (CI) and limits of agreement (LoA) widths were conducted to assess differences and correlations between devices. All parameters, except for Ks, were significantly different. Pairwise comparison revealed no significant differences between keratometry obtained by IOLMaster 700 and Pentacam. LoA widths of all paired comparisons for Ks were >0.80 D. Except for WTW between IOLMaster 700 and CASIA2 and between CASIA2 and Pentacam, other Pearson's coefficients between devices showed a strong correlation (all r>0.95). The ICC of WTW (ICC=0.438, 95%CI 0.167-0.625) showed poor reliability. The reliability of CCT, ACD, and AQD was excellent (all ICC>0.95), whereas that of TKm was good (ICC=0.827, 95%CI 0.221-0.939). A significant linear correlation was also observed among devices. The ocular parameters derived from the use of IOLMaster700, CASIA2, and Pentacam exhibit significant discrepancies; as such, measurements from these devices should not be deemed as interchangeable.

Three optical intervention methods for low myopia control in children: a one-year follow-up study

ObjectiveThis study aimed to compare the one-year efficacy of myopia prevention and control using three optical intervention methods - single vision lens (SVL), highly aspherical lenslet (HAL), and orthokeratology (OK) lens - in children with low myopia.MethodsA cohort of 150 children aged 7–13 years with low myopia was recruited and divided into three groups: SVL (n = 50), HAL (n = 50), and OK lens group (n = 50), based on their preference for glasses. Follow-up assessments were carried out over one year, focusing on data from the right eye for statistical analysis. Baseline characteristics such as gender, age, axial length (AL), spherical equivalent refractive error (SER), flat keratometry (K1), steep keratometry (K2), anterior chamber depth (ACD), white-to-white corneal diameter (WTW), and non-contact tonometry (NCT) measurements were gathered and compared among the three groups before any intervention. Changes in AL growth after 1 year of intervention were assessed across the three groups. Subsequently, the AL growth control rates between the HAL and OK lens groups were compared, with the SVL group serving as the reference standard.ResultsThe study found no statistically significant variances in baseline characteristics (gender, age, SER, AL, K1, K2, WTW, and NCT) among the SVL, HAL, and OK lens groups (all p > 0.05). Following a one-year intervention, AL growth rates were as follows: HAL group (0.163 ± 0.113 mm) < OK lens group (0.280 ± 0.170 mm) < SVL group (0.516 ± 0.190 mm), with statistically significant disparities (p < 0.05). The HAL group demonstrated a higher 1-year AL growth control rate (68.41%) compared to the OK lens group (45.74%) for children aged 7–13 with low myopia, with a statistically significant differences (p < 0.001). And there was significant difference in the SER change between SVL group and HAL group (p < 0.001).ConclusionCompared to SVL, HAL and OK lens are more effective in controlling axial growth in mild myopia. Specifically, HAL maybe shows superior outcomes in both preventive and corrective measures, also it needs to be supported by more studies from randomized controlled experiments.