Corneal Topography Measurements Research Articles

Regional Summed Corneal Refractive Power Changes in Myopic Orthokeratology and Their Relationships With Axial Elongation.

To determine the relationship between regional summed corneal refractive power changes (CRPCs) in myopic orthokeratology and axial elongation. This retrospective study included 70 eyes of 70 patients aged 8 years to 13 years who underwent orthokeratology lens (OK lens) treatment, and all patients underwent regular follow-ups at 1 week, 1 month, 6 months, and 12 months at Zhongshan Ophthalmic Center between January 2019 and May 2021. Axial length (AL) was measured at baseline and 12 months by an IOLmaster 5.0. Refractive error power was measured using cycloplegia. Regional summed CRPCs were calculated by MATLAB software using difference tangential power maps at the sixth month acquired by corneal topography measurements (Medmont E300 Corneal Topographer; Medmont Pty, Victoria, Australia) and defined as changes in corneal refractive power at the sixth month from baseline. The regional summed CRPCs were then subdivided into 4-mm diameter circles, 4- to 5-mm diameter chords, and 5- to 6-mm diameter chords according to the distance from the central of the pupil and into negative, positive, and total according to the values. Pearson correlation, multiple linear regression analysis, and stepwise multiple linear regression analysis were performed to analyze the relationships among these parameters. Axial elongation had a negative relationship with positive regional summed corneal refractive power in the central 4-mm diameter circle and age (r=-0.282, P=0.018; r=-0.473, P<0.001, respectively) and a positive relationship with negative regional summed corneal refractive power in the 5- to 6-mm diameter chord (r=0.361, P=0.002). Stepwise multiple linear regression analysis identified age (standardized β=-0.434, P<0.001) and negative regional summed corneal refractive power in the 5- to 6-mm diameter chord (standardized β=0.305, P=0.004) as factors influencing AL elongation. Negative regional summed corneal refractive power in a 5- to 6-mm diameter chord after OK lens treatment may be an important index for evaluating the control effects of axial elongation.

Higher Order Aberrations in Patients with Unilateral Nasolacrimal Duct Obstruction.

To compare corneal higher order aberrations (HOAs) in patients with epiphora caused by unilateral primary acquired nasolacrimal duct obstruction (PANDO) and their fellow eyes. One hundred twenty two eyes of 61 patients with unilateral PANDO were included. Affected eyes named as Group 1 and contralateral eyes named as Group 2. Munk scale and fluorescein dye disappearance test (FDDT) were assessed. Corneal topographic and HOAs measurements were taken by Sirius topography. There were 47 female and 14 male patients. The mean Km were 43.84± 1.4 in Group 1 and 43.96± 1.4 in Group 2 (p=0.73). The mean corneal topographic astigmatism were 0.81± 0.7 in Group 1 and 0.78± 0.5 in Group 2 (p=0.57). The mean coma-like aberration was 0.19± 0.2 in Group 1 and 0.1± 0.1 in Group 2 (p=0.03). The mean spherical-like aberration was 0.16± 0.1 in Group 1 and 0.11± 0.1 in Group 2 (p=0.04). The mean total corneal HOA was 0.3±0.5 in Group 1 and 0.23±0.2 in Group 2 (p=0.04). The mean munk score was 3.47± 1 in Group 1. There was a positive correlation between munk score and coma-like aberration and total corneal HOAs levels (r=0.53; p=0.003 and r=0.44; p=0.01 respectively). The mean FDDT was grade 2.6± 0.1 in Group 1. There was a positive correlation between FDDT grade and coma-like aberration and total corneal HOAs levels (r=0.48; p=0.001 and r=0.33; p=0.001 respectively). Epiphora in patients with PANDO can affect corneal HOAs. As patients symptoms and tear pooling were increased corneal HOA levels increased.

Relationship between hyperglycemia and intraocular pressure, corneal biomechanics, and corneal topography during the oral glucose tolerance test in nondiabetic patients.

Altered corneal biomechanics in patients with diabetes may affect intraocular pressure (IOP) measurements. Although a relationship between IOP and glucose levels has been reported in diabetic and nondiabetic patients, the mechanism by which hyperglycemia influences IOP is unclear. The aim of this study was to determine the effects of hyperglycemia on IOP, corneal biomechanics, and anterior segment parameters during the oral glucose tolerance test (OGTT) in nondiabetic patients. Twenty-one patients without DM who underwent OGTT were included in this study. A complete ophthalmologic examination was performed before the test. Blood glucose, insulin level, IOP (iCare rebound tonometer), Ocular Response Analyzer, and corneal topography (Pentacam) measurements were obtained at 0, 1, and 2h during the OGTT. Data from the patients' right eyes were included in the analysis. The mean age of the patients was 46.9 ± 11.0years. There was a statistically significant difference in IOP between 1 and 2h (p = 0.03) and a clinically significant difference between 0 and 1h (p = 0.06). Corneal resistance factor was lower at 2h than 1h (p = 0.03), while central cornea thickness was increased at 1h (p = 0.01) and 2h (p = 0.05) compared to 0h. There was positive partial correlation between hyperglycemia and IOP at 1h (p = 0.049, r = 0.67). The positive partial correlation between IOP and glucose level suggests that acute hyperglycemia may lead to increased IOP. However, further research is needed to explain the mechanism of IOP elevation in the hyperglycemic phase during OGTT.

Effect of Computer Tasks in Straight Gaze on Corneal Topographic Indices.

To investigate the effect of the near visual task of movie-watching in the straight gaze position on corneal topographic parameters. Thirty myopic young adults with an average age of 25.10 4.13 years were recruited for the study. The designed near visual task consisted of watching a movie in the straight gaze position at a distance of 40 cm for 30 minutes. Corneal topography was performed using Oculus Keratograph 4 (OCULUS, Wetzlar, Germany) before and immediately after watching the movie, as well as at 10, 20, and 30 minutes intervals after completing this near visual task. Zernike coefficients, asphericity indices, refractive parameters, and diagnostic indices of keratoconus were recorded for statistical analysis. Movie-watching at a close distance solely using the straight gaze position had no effect on Zernike coefficients (P 0.130). Also, watching the movie had no effect on other corneal topography parameters including irregularities (P = 0.208), spherical eccentricity (P = 0.270), maximum decentration (P = 0.553), axis of maximum decentration (P = 0.186), peripheral astigmatism (P = 0.179), and average asphericity of the quadrants at 10 to 30º (P 0.163). The results of the present study showed that watching movies in the straight gaze position had no effect on corneal topographic parameters and did not cause errors in corneal topographic measurements.

Corneal topography using a smartphone-based corneal topographer considering a biconical model for the corneal surface

In this paper, we propose a generalization in both null-screen design and corneal surface topography retrieval algorithms to assess the nonsymmetric surface of the human cornea using a compact smartphone-based corneal topographer. The proposed new null-screen design considers the corneal surface to be a biconic surface, and the evaluation algorithms assume a general biconic shape with decentering, defocus, tilt, and rotation around the z-axis. We discussed how to integrate the measurement system to obtain geometric parameters of the corneal surface such as radius of curvature, conic constants, as well as elevation map, and sagittal and meridional curvature maps. To demonstrate that our proposed smartphone-based corneal topographer provides reliable measurements of corneal topography, we conducted measurements on a well-known biconic surface and two human corneas.

Precision in IOL Calculation for Cataract Patients with Prior History of Combined RK and LASIK Histories.

This study aimed to evaluate the accuracy of 12 intraocular lens (IOL) power calculation formulae for eyes that have undergone both radial keratotomy (RK) and laser assisted in situ keratomileusis (LASIK) surgery to determine the efficacy of various IOL calculations for this unique patient group. Currently, research on this surgical topic is limited. In this retrospective study, 11 eyes from 7 individuals with a history of RK and LASIK who underwent cataract surgery at Hoopes Vision were analyzed. Preoperative biometric and corneal topographic measurements were performed. Subjective refraction was obtained postoperatively. Twelve different intraocular lens (IOL) power calculations were used: Barrett True K No History, Barrett True K (prior LASIK, Prior RK history), Barrett Universal 2, Camellin-Calossi-Camellin (3C), Double K-Modified Holladay, Haigis-L, Galilei, OCT, PEARL-DGS, Potvin-Hill, Panacea, and Shammas. The rankings of mean arithmetic error (MAE), from least to greatest, were as follows: 3C (0.088), Haigis-L-L (-0.508), Shammas (-0.516), OCT Average (-0.538), Barrett True K (-0.557), OCT RK (-0.563), Galilei (-0.570), IOL Master (-0.571), OCT LASIK (-0.583), Barrett True K No History (-0.597), Pearl-DGS (-0.606), Potvin-Hill SF (-0.770), Potvin-Hill TNP (-0.778), Panacea (-0.876), and Barrett Universal 2 (-1.522). The 3C formula achieved the greatest percentage of eyes within ±0.25 D of target range (91%), while Haigis-L, Shammas, Galilei, Potvin Hill, Barrett True K, IOL Master, PEARL-DGS, and OCT formulae performed similarly, achieving 45% of eyes within ±0.75D of target refraction. This study demonstrates the accuracy of the lesser known 3C formula in IOL calculation, particularly for patients who have undergone both RK and LASIK. Well-known formulae, such as Haigis-L, Shammas, and Galilei, which are used by the American Society of Cataract and Refractive Surgery (ASCRS), are viable options, although 3C formulae should be considered in this patient population. Furthermore, larger studies can confirm the best IOL power formulas for post-RK and LASIK cataract patients.

No Changes in Keratometry Readings and Anterior Chamber Depth after XEN Gel Implantation in Patients with Glaucoma.

Background: This study aimed to compare keratometry and anterior chamber depth (ACD) changes after XEN implantation in primary open-angle glaucoma (POAG) cases over a 3-month follow-up period. Methods: Twenty patients with POAG who underwent XEN63 implantation, either standalone or combined with cataract surgery, were included. Preoperative data, including best-corrected visual acuity (BCVA), refraction, gonioscopy, ophthalmoscopy, intraocular pressure (IOP) evaluation, and axial length, were collected. Corneal topography and ACD measurements were assessed preoperatively and at postoperative days 1, 7, 15, 30, 60, and 90. Each patient's eye that underwent XEN surgery was included in the study group, with the fellow eye serving as a control. Results: In the study group, there was a significant decrease in IOP after XEN stent implantation at all investigated time intervals (p < 0.05). However, changes in mean ACD did not show statistically significant differences at any follow-up examination in both the study and control groups. Additionally, keratometry readings revealed no significant changes in total astigmatism or steep keratometry values in either group. Conclusions: XEN implantation in POAG cases resulted in a significant decrease in IOP over the 3-month follow-up period. However, there were no significant changes observed in mean ACD or keratometry readings, indicating stability in these parameters post-XEN implantation. These findings suggest that XEN implantation may be an effective option for IOP reduction without affecting corneal curvature or ACD in POAG patients.

Predictability of Existing IOL Formulas After Cataract Surgery in Patients with a Previous History of Radial Keratotomy: A Retrospective Cohort Study and Literature Review.

This study aims to evaluate the accuracy of 12 different intraocular lens (IOL) power calculation formulas for post-radial keratotomy (RK) eyes. The investigation utilizes recent advances in topography/tomography devices and artificial intelligence (AI)-based calculators, comparing the results to those reported in current literature to assess the efficacy and predictability of IOL calculations for this patient group. In this retrospective study, 37 eyes from 24 individuals with a history of RK who underwent cataract surgery at Hoopes Vision Center were analyzed. Biometry and corneal topography measurements were taken preoperatively. Subjective refraction was obtained 6 months postoperatively. Twelve different IOL power calculations were used, including the American Society of Cataract and Refractive Surgery (ASCRS) post-RK online formula, and the Barrett True K, Double K modified-Holladay 1, Haigis-L, Panacea, Camellin-Calossi, Emmetropia Verifying Optical (EVO) 2.0, Kane, and Prediction Enhanced by Artificial Intelligence and output Linearization-Debellemanière, Gatinel, and Saad (PEARL-DGS) formulas. Outcome measures included median absolute error (MedAE), mean absolute error (MAE), arithmetic mean error (AME), and percentage of eyes achieving refractive prediction errors (RPE) within ± 0.50 D, ± 0.75 D, and ± 1 D for each formula. A search of the literature was also performed by two independent reviewers based on relevant formulas. Overall, the best performing IOL power calculations were the Camellin-Calossi (MedAE = 0.515 D), the ASCRS average (MedAE = 0.535 D), and the EVO (MedAE = 0.545 D) and Kane (MedAE = 0.555 D) AI-based formulas. The EVO and Kane formulas along with the ASCRS calculation performed similarly, with 48.65% of eyes scoring within ± 0.50 D of the target range, while the Equivalent Keratometry Reading (EKR) 65 Holladay formula achieved the greatest percentage of eyes scoring within ± 0.25 D of the target range (35.14%). Additionally, the EVO 2.0 formula achieved 64.86% of eyes scoring within the ± 0.75 D RPE category, while the Kane formula achieved 75.68% of eyes scoring within the ± 1 D RPE category. There was no significant difference in MAE between the established and newer generation formulas (P > 0.05). The Panacea formula consistently underperformed when compared to the ASCRS average and other high-performing formulas (P < 0.05). This study demonstrates the potential of AI-based IOL calculation formulas, such as EVO 2.0 and Kane, for improving the accuracy of IOL power calculation in post-RK eyes undergoing cataract surgery. Established calculations, such as the ASCRS and Barrett True K formula, remain effective options, while under-utilized formulas, like the EKR65 and Camellin-Calossi formulas, show promise, emphasizing the need for further research and larger studies to validate and enhance IOL power calculation for this patient group.

The effect of transepithelial corneal collagen cross-linking treatment on optical quality of the cornea in keratoconus: 12-month clinical results.

To evaluate the effect of transepithelial corneal collagen crosslinking (CXL) treatment on the optical performance of the cornea at 12-month follow-up after CXL in patients with progressive keratoconus. One hundred and ten eyes of 67 patients were included. The following corneal optical aberrations over the 4-mm-diameter pupil were recorded via Sirius dual-scanning corneal tomography: total, anterior and posterior amount of corneal higher order aberrations [HOAs], vertical coma, horizontal coma, vertical trefoil, oblique trefoil, and spherical aberration, and Strehl ratio of point spread function (PSF). There were significant improvements in mean root mean square error values for corneal total HOA, total coma, anterior HOA, anterior coma, and vertical coma following CXL (P > 0.05, for all). No significant changes were found in the posterior aberometric parameters.PSF value did not change after CXL (P > 0.05). The corneal topographic measurements not revealed a change in the mean simulated keratometry-1, simulated keratometry-2, and maximum keratometry compared with the baseline measurements (P > 0.05, for all). At 12months, there was a significant improvement in the uncorrected (UCVA) and best corrected (BCVA) visual acuity (P < 0.001, both). Most corneal aberrations correlated significantly with postoperative BCVA, but changes in HOAs were not statistically associated with improvements in visual acuity. Transepithelial CXL was effective in stabilizing the keratometric indices and improving the most corneal aberrations in keratoconic eyes 1year after the procedure. While the healing effect on aberrations after CXL was in total and anterior parameters, no significant changes were observed in the posterior surface. In addition, it was observed that transepithelial CXL treatment did not cause a significant change in PSF distribution data.

Effect of corneal diameter on preoperative screening results for corneal refractive surgery.

To investigate the impact of different corneal diameters on corneal morphology and biomechanical outcome during preoperative screening for corneal refractive surgery. A retrospective analysis was conducted on 300 patients who underwent corneal refractive surgery at Eye and ENT Hospital, Fudan University between October 2023 and December 2023. All patients had no history of keratoconus or previous corneal surgery. Patients were categorized into two groups based on corneal topography measurements: (1) normal corneal diameter group (n=159), those with corneal diameter ranging from 11.5 mm to 12.0 mm; (2) abnormal corneal diameter group (n=141), those with corneal diameter smaller than 10.0 mm or larger than 12.5 mm. Corneal thickness, morphologic data, and biomechanical data were measured using Pentacam corneal topography. Correlation analysis was conducted to explore the relationship between corneal diameter and various corneal topography and biomechanical data. Significant differences were observed in corneal topography data including BFSf (F=43.21), BFSb (F=30.24), Df (F=15.32), Dp (F=32.36), Da (F=9.66), D (F=58.36), PPIavg (F=32.64), and ARTmax (F=12.06) between the groups (P<0.05). Additionally, BFSf, BFSb, Db, Dp, D, and PPIavg exhibited statistically significant differences between any two groups (P<0.05). Significant differences were also found in Df, Da, and ARTmax between small and large corneas, as well as between normal-sized and large corneas (P<0.05). Correlation analysis indicated negative correlations between corneal diameter and A1V (r=-0.12), HCdArcLength (r=-0.17), CBI (r=-0.27), bIOP (r=-0.13), Df (r=-0.025), PPIavg (r=-0.028), and TBI (r=-0.27). Conversely, BFSf (r=0.009), BFSb (r=0.001), PD (r=0.15), and ARTH (r=0.37) displayed positive correlations with corneal diameter. Corneal diameter significantly affects preoperative screening for corneal refractive surgery. Smaller corneal diameters exhibit a greater influence on the corneal topography BAD analysis system.

Accuracy of Astigmatism Calculation with the Barrett, Panacea, and enVista Toric Calculators.

To evaluate residual refractive astigmatism using the Panacea and enVista toric calculators, compared to the gold-standard Barrett toric calculator. A retrospective and comparative study was conducted in one center. We reviewed the medical records of all patients with a diagnosis of senile cataracts and regular corneal astigmatism, without previous corneal or intraocular surgery, who underwent phacoemulsification with implantation of a toric intraocular lens, who had pre- and postoperative corneal topography, biometry, and refraction measurements. The frequency of preoperative astigmatism according to the axis was 70 (84%) eyes showing with-the-rule (WTR) astigmatism, 9 (14%) eyes with against-the-rule (ATR) astigmatism, and 1 (2%) eye with oblique astigmatism. Regarding astigmatism prediction errors, there were statistically significant differences between the enVista and Panacea calculators (median of 0.39, 0.18, and 0.52 for Barrett, enVista, and Panacea, respectively). The residual astigmatism prediction error centroid was similar for the Barrett and enVista toric calculators, and both were lower compared to the Panacea calculator (x-component p < 0.001). The enVista toric calculator incorporating the Emmetropia Verifying Optical (EVO) toric calculator provides similar results to the gold-standard Barrett calculator.

Comparison of Hybrid Contact Lenses and Rigid Gas-Permeable Contact Lenses in Moderate and Advanced Keratoconus.

We aimed to compare the clinical results and topographic data of the new generation hybrid contact lens (HCL) and rigid gas-permeable contact lens (RGPCL) in patients with moderate and advanced keratoconus. In this prospective study, HCL users comprised group 1 and RGPCL users comprised group 2. Snellen uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and lens-corrected visual acuity (LCVA); manifest spherical-cylindrical values; corneal topography measurements (flat keratometry [K1], vertical keratometry [K2], mean K, maximum K [Kmax], central corneal thickness [CCT], and thinnest corneal thickness [TCT]); and cone location were recorded. The study included 83 eyes of 51 patients in group 1 and 61 eyes of 40 patients in group 2. The groups were similar in age and gender (p>0.05). Mean LCVA (logMAR) was significantly lower than BCVA in both groups (p<0.001). The mean visual gain with contact lenses (Snellen chart) was 3.4±1.8 lines in group 1 and 4.0±2.1 lines in group 2. There was no significant difference between the two groups in BCVA, LCVA, or lines gained (p>0.05). There was also no significant difference between the two groups in terms of keratoconus stages, mean Kmax, CCT, TCT, or cone location (p>0.05), while mean UCVA (logMAR) and mean K were higher in group 2 (p<0.05). In both groups, the visual gain with lenses was higher in eyes with central cones, and there was significantly greater visual increase in group 2 (p=0.039). In moderate and advanced keratoconus, HCLs improved vision as much as RGPCLs and both lenses were more effective for central cones. Nevertheless, longer term of follow-up and larger numbers of patients are needed for long term follow-up results of HCL.

Analysis of corneal topographic and endothelial cell properties in newly diagnosed obstructive sleep apnea patients: A case-control study

PurposeTo investigate the topographic features and endothelial cell changes in the corneas of patients with newly diagnosed obstructive sleep apnea (OSA). BackgroundThis cross-sectional case-control study included 98 patients with OSA and 90 healthy controls. OSA was diagnosed on the basis of a polysomnographic sleep examination. Patients with OSA were grouped according to their apnea-hypopnea index (AHI) scores. Corneal topographic measurements were obtained using the Scheimpflug–Placido disk topographer, and keratometry values, anterior chamber parameters, thinnest corneal thickness, symmetry index (SI), keratoconus vertex (KV), and the Baiocchi-Calossi-Versaci index, including keratoconus (KC) screening indexes, were recorded. The corneal endothelium was visualizedby specular microscopy, and the endothelial cell density, coefficient of variability (CV), and percentage of hexagonal cells (HEX) were recorded. ResultsIn this study, 32 patients had mild, 34 patients had moderate, and 32 patients had severe OSA. The mean back KV (KVb) and back SI values were significantly higher in the OSA group than in the control group (P <0.001, P = 0.035, respectively). As body mass index (BMI) increased, KVb also increased significantly (r = 0.281; P = 0.009). The mean CV and HEX values differed significantly between the OSA and control groups (P = 0.012 and P = 0.002, respectively). In addition, a significant correlation was found between AHI and KVb and CV values (r = 0.315; P <0.001 and r = 0.231; P = 0.011, respectively). ConclusionsThis study revealed abnormal changes in the corneal endothelial morphology and topographic KC screening indexes in relation to OSA severity in patients and controls. Further research is required to determine the effect of BMI on corneal topographic findings in patients with OSA.

A strategy to treat coagulopathy in patients with massive hemorrhage

To investigate the topographic features and endothelial cell changes in the corneas of patients with newly diagnosed obstructive sleep apnea (OSA).This cross-sectional case-control study included 98 patients with OSA and 90 healthy controls. OSA was diagnosed on the basis of a polysomnographic sleep examination. Patients with OSA were grouped according to their apnea-hypopnea index (AHI) scores. Corneal topographic measurements were obtained using the Scheimpflug–Placido disk topographer, and keratometry values, anterior chamber parameters, thinnest corneal thickness, symmetry index (SI), keratoconus vertex (KV), and the Baiocchi-Calossi-Versaci index, including keratoconus (KC) screening indexes, were recorded. The corneal endothelium was visualizedby specular microscopy, and the endothelial cell density, coefficient of variability (CV), and percentage of hexagonal cells (HEX) were recorded.In this study, 32 patients had mild, 34 patients had moderate, and 32 patients had severe OSA. The mean back KV (KVb) and back SI values were significantly higher in the OSA group than in the control group (P <0.001, P = 0.035, respectively). As body mass index (BMI) increased, KVb also increased significantly (r = 0.281; P = 0.009). The mean CV and HEX values differed significantly between the OSA and control groups (P = 0.012 and P = 0.002, respectively). In addition, a significant correlation was found between AHI and KVb and CV values (r = 0.315; P <0.001 and r = 0.231; P = 0.011, respectively).This study revealed abnormal changes in the corneal endothelial morphology and topographic KC screening indexes in relation to OSA severity in patients and controls. Further research is required to determine the effect of BMI on corneal topographic findings in patients with OSA.

Effect of fixational eye movements in corneal topography measurements with optical coherence tomography.

There is an increasing interest in applying optical coherence tomography (OCT) to quantify the topography of ocular structures. However, in its most usual configuration, OCT data is acquired sequentially while a beam is scanned through the region of interest, and the presence of fixational eye movements can affect the accuracy of the technique. Several scan patterns and motion correction algorithms have been proposed to minimize this effect, but there is no consensus on the ideal parameters to obtain a correct topography. We have acquired corneal OCT images with raster and radial patterns, and modeled the data acquisition in the presence of eye movements. The simulations replicate the experimental variability in shape (radius of curvature and Zernike polynomials), corneal power, astigmatism, and calculated wavefront aberrations. The variability of the Zernike modes is highly dependent on the scan pattern, with higher variability in the direction of the slow scan axis. The model can be a useful tool to design motion correction algorithms and to determine the variability with different scan patterns.

Dynamic topography analysis of the cornea and its application to the diagnosis of keratoconus

ProposeTo establish a dynamic topography analysis method which simulates the dynamic biomechanical response of the cornea and reveals the variations of such response within the corneal surface, and thereafter to propose and clinically evaluate new parameters for the definite diagnosis of keratoconus. Methods58 normal (Normal) and 56 keratoconus (KC) subjects were retrospectively included. Personalized corneal air-puff model was established using corneal topography data by Pentacam for each subject, and the dynamic deformation under air-puff loading was simulated using finite element method, which then enabled calculations of corneal biomechanical parameters of the entire corneal surface along any meridian. Variations in these parameters across different meridians and between different groups were explored by two-way repeated measurement analysis of variance. New dynamic topography parameters were proposed as the range of the calculated biomechanical parameters within the entire corneal surface, and the AUC of ROC curve was used to compare the diagnostic efficiency of newly proposed and existing parameters. ResultsCorneal biomechanical parameters measured in different meridians varied significantly which were more pronounced in KC group due to its irregularity in corneal morphology. Considering such between-meridian variations thus led to improved diagnostic efficiency of KC as presented by the proposed dynamic topography parameter rIR with an AUC of 0.992 (sensitivity: 91.1%, specificity: 100%), significantly better than the current topography and biomechanical parameters. ConclusionsThe diagnosis of keratoconus may be affected by the significant variations of corneal biomechanical parameters due to corneal morphology irregularity. By considering such variations, the current study established the dynamic topography analysis process which benefits from the high accuracy of (static) corneal topography measurement while improving its diagnosis capacity. The proposed dynamic topography parameters, especially the rIR parameter, showed comparable or better diagnostic efficiency for KC than existing topography and biomechanical parameters, which can be of great clinical significance for clinics without access to instrument for biomechanical evaluations.

Age-related changes in Scheimpflug corneal densitometry and their correlations with corneal topographic measurements in a healthy Chinese population.

Objective measurement of corneal densitometry (CD) values can be used to assess corneal transparency and health status, to investigate corneal diseases, and to review anterior segment surgeries. However, literature regarding the association between CD and corneal parameters in healthy adolescent and older individuals is limited. This study investigated age-related changes in Scheimpflug CD values and their correlations with age, sex, and corneal topographic parameters. This retrospective cross-sectional observational study included 347 eyes from 181 consecutive healthy Chinese participants aged between 5 and 90 years. They were divided into 9 age groups: 5-9, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, and 80-90 years. CD and corneal topographic measurements were measured using the Oculus Pentacam. To evaluate CD, the cornea was divided into 3 layers according to depth (anterior 120 µm, central, and posterior 60 µm), and into 4 annular regions according to diameter (0-2, 2-6, 6-10, and 10-12 mm). CD across different depths and regions was positively correlated with age (all P values <0.001). Of the 3 layers of corneal thickness, CD was highest in the anterior 120 µm and lowest in the posterior 60 µm (all P values <0.05). Among the 4 annular regions spanning the corneal diameter, the lowest CD values were 6-10, 2-6, and 0-2 mm at 5-29, 30-69, and 70-89 years, respectively. The highest CD values were 10-12 mm at 5-79 years, and 6-10 mm at 80-90 years (all P values <0.05). CD values of 10-12 mm in the anterior 120 µm corneal layer were significantly lower in men than in women (Z=-2.353; P=0.019). CD of 0-10 mm in each layer was not significantly different between sexes (all P values >0.05). Corneal topographic measurements, including flat-axis keratometry (K1), steep-axis keratometry (K2), and spherical aberration, were slightly positively correlated with age and CD (all P values <0.05). However, central corneal thickness (CCT) and thinnest corneal thickness (TCT), and age or CD showed no correlation (all P values >0.05). With age, CD, keratometry, and spherical aberration gradually increased, while the corneal thickness did not change significantly.

Analysis of corneal topographic and densitometric properties in patients receiving systemic isotretinoin therapy

Purpose To evaluate dry eye parameters, corneal topographic features, corneal densitometric changes, and anterior segment parameters in patients receiving systemic isotretinoin treatment. Methods This prospective cross-sectional study included 66 eyes of 33 patients who were started on oral isotretinoin therapy for severe acne vulgaris. All patients were evaluated in terms of ocular surface tests such as tear break-up time (TBUT) and Schirmer-1 and were asked to fill in the ocular surface disease index (OSDI) questionnaire. Corneal densitometric and topographic measurements were obtained using the Scheimpflug imaging system. Results The mean age of the patients was 19.9 ± 1.6 years, and 21 (63.6%) of the participants were female. The mean OSDI score was significantly higher in the third month than before treatment (20.05 ± 19.38, vs. 26.96 ± 22.94, p = 0.00, respectively). The mean values of the TBUT test were significantly lower in the third month than before treatment (9.06 ± 4.40 sec, vs. 10.71 ± 4.61 sec, p = 0.02, respectively). Mean scores of the Schirmer 1 test showed no statistically significant difference between before treatment and the third month (16.08 ± 8.40 mm, vs. 16.08 ± 8.50 mm, p = 1, respectively). There was no statistically significant difference between before treatment and the third month in the majority of the densitometry measurements in concentric zones. However, the difference tended to be significant between the groups concerning posterior zone 0–2 mm (11.01 ± 0.85 GSU vs. 10.62 ± 0.89 GSU, p = 0.006). The RMS LOAs (front), RMS Total (Total), RMS LOAs Total (Total), RMS HOAs Total (Total), K max, CCT, and CoV values were significantly higher in the third month than before treatment (p < 0.05 for all). Conclusions The dermatology specialists should be aware of the ocular complications of systemic isotretinoin therapy. Therefore, a complete ophthalmologic examination for the prompt apprehension and management of ocular involvement is essential in patients under isotretinoin therapy to increase ocular comfort and adherence to the therapy.

The repeatability of corneal topography measurements in severe Dry Eye disease

BackgroundTo determine the repeatability of corneal topography measurements in severe dry eye disease (DED). A comparison of corneal topography parameters between severe DED and healthy subjects was a secondary goal of this study.MethodsSixty-nine patients with severe DED and 46 healthy subjects were enrolled in the study. All participants underwent repeated corneal topography measurements with Pentacam (Oculus, Germany) within a half hour time. Both eyes of the participants were used in statistical analysis. A further subcategorization of severe DED patients was performed according to Ocular Surface Disease Index (OSDI) scores: 32–50, 51–70 and 71–100. The repeatability of corneal parameters was assessed with correlation coefficients (CC).ResultsThe mean age of dry eye patients and healthy subjects were 40.8 ± 13.2 (17–66) and 39.8 ± 8.2 (18–61) years (p:0.604) respectively. No significant differences were found between severe DED and control groups according to analysed corneal parameters in both eyes (p:>0.05). All CCs were greater than 0.9 in severe DED group (p:<0.001). All CCs were also greater than 0.9 in severe DED patients among different OSDI groups (p:<0.001).ConclusionsCorneal topography measurements are highly repeatable in severe DED with Pentacam. This is the first report about this topic. Nonetheless, further studies are needed with different topography devices for validation.

Changes in retinal vessel and retinal layer thickness after cross-linking in keratoconus via swept-source OCT angiography.

To analyze the postoperative foveal avascular zone (FAZ) area, superficial capillary plexus (SCP), deep capillary plexus (DCP) vascular densities (VD), and retinal layers after cross-linking (CXL) for keratoconus treatment. Twenty-seven eyes with cross-linking treatment for keratoconus were included in the study. Foveal avascular zone (FAZ) area, SCP VD, DCP VD, and retinal layers were evaluated by using optical coherence tomography angiography (OCTA). OCTA measurements were made at preoperative, first week, and first and sixth months after the surgery. In addition, corneal topography measurements were also made. Although there was a decrease in corneal thickness in the follow-up of the patients, there was no significant difference in axial length and anterior chamber depth. There was no significant difference in full retinal thickness in the foveal and parafoveal areas. While there was a significant increase in retinal nerve fiber layer (RNFL) thickness in the foveal area (p = 0.032, p = 0.015, p = 0.017; preoperative values compared to first week, first month, and sixth month respectively), there was a decrease in ganglion cell layer (GCL) thickness in the parafoveal area in the postoperative sixth month (p = 0.028). There was no difference in FAZ measurements. In the parafoveal area, a decrease was observed in SCP VD in the sixth-month control (p = 0.019). There was a significant increase in DCP VD in the foveal area (p = 0.008, p = 0.043, p = 0.040). The preoperative mean CDVA (corrected distance visual acuity) was 0.37 ± 0.16 logMAR and postoperative sixth month mean CDVA was 0.39 ± 0.15. There was no significant difference in visual acuity(p = 0.71). Keratoconus patients successfully treated with CXL had significant changes in retinal layers and vessel density in the superficial and deep retinal plexus.