Corneal Thickness Measurements Research Articles

Repeatability of Corneal Epithelial Thickness Map Using Anterior Segment Optical Coherence Tomography in Normal and Corneal Disease Patients.

To evaluate the repeatability of corneal epithelial thickness (CET) measurements in normal eyes and eyes diagnosed with corneal disease using the epithelial thickness map (ETM) of anterior segment optical coherence tomography (OCT). In this retrospective study, patients with 3 OCT scans using the ETM mode of Cirrus OCT (Carl Zeiss Meditec AG, Jena, Germany) between October 2021 and January 2024 were reviewed. Two groups of subjects were included: (1) normal subjects with no history of ophthalmic surgery, corneal diseases, and topical antiglaucoma medication uses; and (2) subjects with corneal diseases including dry eye syndrome, recurrent corneal erosion, pterygium, and others. 57 eyes of 57 normal subjects and 106 eyes of 76 patients with corneal disease were included. ETM was analyzed in 25 zones (1 zone within 0-2 mm diameter, 8 zones within 2-5 mm diameter, 8 zones within 5-7 mm diameter, and 8 zones within 7-9 mm diameter). Repeatability was evaluated by calculating intraclass correlation coefficient (ICC), coefficient of variation (CoV), within-subject standard deviation (Sw), and Bland-Altman plot. Among a total of 25 sectors, the normal eyes showed high repeatability (ICC > 0.75, CoV 2.17%-5.29%, and Sw 0.76-1.65 μm) in 23 sectors, and in corneal diseases patients also showed high repeatability (ICC >0.75, CoV 4.17%-9.61%, and Sw 1.29-3.34 μm) in 22 sectors. However, the wide range of 95% limit of agreement (LoA) width of Bland-Altman plot presented in corneal disease group and some peripheral zones in normal eyes indicates some variability of CET measurements. Except for a few peripheral sectors, ETM of Cirrus OCT provides repeatable CET measurements in normal eyes, however in corneal disease group, repeatability was not consistently high. To measure CET accurately, performing multiple measurements is advised especially in patients with corneal disease and patients in whom peripheral CET values.

Progression of corneal thinning and melting after collagen cross-linking for keratoconus.

To study the aetiology, diverse clinical manifestations, therapeutic interventions, and prognoses in patients with corneal thinning after collagen cross-linking (CXL) treatment. a retrospective observational study of all patients presenting with corneal thinning after collagen cross-linking, in a tertiary eye care hospital in south India from 2011 to 2017. Preoperative details were noted. Patients who presented with corneal thinning were subjected to investigative measures to assess thinning, received appropriate management, and underwent follow-up evaluations. Among the 12 patients, 8 were female and 4 were male, all of whom had undergone standard classical CXL. The duration between CXL and corneal melting/thinning onset varied from 5 to 12 years. Notably, among female patients, 2 were pregnant, 2 were lactating mothers, 1 was undergoing in vitro fertilization (IVF) treatment, and 1 had comorbid diabetes mellitus and hyperthyroidism. Clinical examination revealed corneal thinning accompanied by hypopyon in 1 patient, corneal perforation with shallow anterior chamber in 1 patient, and epithelial defect with crystalline deposit in another patient, the remaining patients exhibited corneal thinning. Corneal thinnest corneal thickness measurements ranged from 212 to 351 µm. Treatment approaches included penetrating keratoplasty (PKP) in 2 patients, deep anterior lamellar keratoplasty (DALK) in 1 patient, cyanoacrylate glue application in 1 patient, and awaiting DALK/PKP in three patients, 4 patients showing no signs of increased thinning. The incidence of corneal thinning after collagen cross-linking is less but fulminant, requiring timely and appropriate management to prevent visual complications.

Optical coherence tomography angiography analysis of the fellow eye in unilateral pseudoexfoliation syndrome

PurposeTo compare the macular and optic disc vascular parameters in the unaffected fellow eyes of subjects with unilateral pseudoexfoliation syndrome (PXS) and controls using optical coherence tomography angiography (OCTA).MethodsThe medical records of 61 eyes of 61 patients were analyzed in a retrospective study. Of these, 30 eyes were unaffected fellow eyes and 31 eyes were control eyes. The vessel density (VD), perfusion density (PD) and foveal avascular zone (FAZ)-related parameters of the superficial capillary plexus (SCP) in the circumpapillary and macular area and the VD and PD of the deep capillary plexus (DCP) in the macular area were measured using OCTA after dilatation and were compared between two groups after adjustment for age, sex and axial length.ResultsThere were no statistically significant differences in sex ratio or mean age, central corneal thickness measurements, refractive errors, intraocular pressures and axial length between both groups (all P > 0.05). In the circumpapillary area, inferior VD and PD in the inner zone, as well as average, temporal, inferior, and nasal VD and PD in the outer zone were significantly reduced in the unaffected fellow eyes with unilateral PXS, while the circumpapillary retinal nerve fiber layer (RNFL) thicknesses were similar between groups. In the macular SCP, VDs were significantly lower in all sectors in the inner area and in the outer zones (p < 0.05 for all), PDs were significantly lower in all sectors (p < 0.05 for all) except the nasal sector of the outer zone (p = 0.003 for average, p = 0.029 for superior sector, p = 0.004 for temporal sector, p < 0.001 for inferior sector), and the FAZ circularity (p = 0.037) were significantly lower in the unaffected fellow eyes with unilateral PXS, whereas macular ganglion cell inner plexiform layer (GCIPL) thickness was similar between the two groups.ConclusionsAlthough circumpapillary RNFL and GCIPL thicknesses were similar between the two groups, VDs and PDs in the circumpapillary and macular SCP and FAZ circularity were significantly lower in the fellow eye of subjects with unilateral PXS.

Comparison of Automated and Manual Measurement of Corneal Epithelial Thickness in Eyes With Limbal Stem Cell Deficiency.

The purpose of this study was to compare the outcomes of manual and automated corneal epithelial thickness (CET) assessments using anterior segment optical coherence tomography in eyes with limbal stem cell deficiency (LSCD). Eighty-seven eyes from 64 patients with LSCD and 65 eyes from 39 healthy subjects were included in this cross-sectional study. OCT images of corneas were acquired using a Fourier-domain anterior segment optical coherence tomography. The automated measurement of CET was obtained using the manufacturer's program and the manual measurements were obtained by 2 masked observers. The average CET was obtained from 3 consecutive epithelial profile maps. The average CET of manual measurement was obtained from 3 consecutive cross-line scans using 3-point measurement as previously described. The central CET was thinner in patients with LSCD compared with healthy individuals by both manual and automated measurements. Automated CET measurements were similar to the manually obtained CET in the healthy controls (r = 0.911). However, there is a lower correlation between the automated and manually obtained CET in the LSCD group (r = 0.497). Manual measurements of CET (39.8 ± 11 μm) in eyes with LSCD were significantly lower than the automated measurements (48.8 ± 7.2 μm, P = 0.001, 95% CI -11.0 to -6.9). The correlations between the automated and manually obtained measurements in the mild, moderate, and severe stages of LSCD were 0.623, 0.632, and 0.378, respectively. There is a large discrepancy between the manual and automated measurements in eyes with LSCD but not in normal eyes. Automated measurements in LSCD exhibited a higher rate of errors and nonuniform measurements due to the presence of subepithelial scars. Automated CET measurements appear to be unreliable in eyes with corneal scars in LSCD.

Low-cost do-it-yourself (DIY) kit for glaucoma procedures.

Surgical skill training in ophthalmology is pivotal for ensuring optimal and safe patient outcomes. Access to traditional training resources such as cadaveric or animal eyes, as well as modern alternatives such as silicone eyeballs and simulators, remains limited, especially in resource-constrained settings. We present a series of innovative and low-cost do-it-yourself (DIY) models for glaucoma training using readily available hospital waste materials. These models allow ophthalmic assistants, fellows, and junior consultants to practice various procedures before transitioning to live patients, thereby enhancing surgical proficiency and minimizing the financial burden on both trainees and training institutions. We were able to practice procedures such as tonometry, central corneal thickness measurement, laser suture lysis, laser iridotomy, anterior chamber decompression, bleb needling, trabeculectomy flap construction, and suturing. By providing a practical and easy training solution, these models have the potential to boost confidence among glaucoma trainees and thus address the growing demand for skilled glaucoma surgeons.

Integrated line-field optical coherence tomography and scheimpflug imaging for corneal imaging

Previously we demonstrated a combined scanning-point optical coherence tomography (OCT) and Scheimpflug Imaging (SI) system, to provide cross-section images of the corneal layers and the whole anterior segment of the eye simultaneously. However, to fully realise the benefits of this dual imaging modality concept towards clinical practice, it is required that the OCT part of the system can achieve ultra-high axial resolution (<3 µm in air) and faster imaging speeds, without using prohibitively expensive components. To achieve this, a new imaging device integrating line-field OCT and SI, using a supercontinuum light source, is demonstrated. This line-field configuration enables both OCT and SI B-scan to be captured using the same light illumination in a single shot, which is the most significant improvement over single point scanning. This achieves an OCT axial resolution down to 2.1 µm in air (1.6 µm in corneal tissue) and an imaging speed up to 213 kA-Scans/s. Since the OCT and SI capture the identical corneal position and serve as cross-validation, this technique offers a great method for accurately determining the individual corneal thickness and refractive index, thereby minimizing individual variations, which can help determine the extent of cutting or correction needed in vision correction. Moreover, the precise measurement of corneal thickness provided by this technique allows for a better understanding of the biomechanical properties of the cornea. We demonstrate the efficacy of the proposed system by evaluating porcine and bovine eyes ex-vivo for determining the corneal refractive index and thickness.

Comparison of the repeatability and reproducibility of corneal thickness mapping using optical coherence tomography according to tear film break-up time

BackgroundTo compare the repeatability and reproducibility of corneal and corneal epithelial thickness mapping using anterior segment optical coherence tomography (AS-OCT) according to tear film break-up time (TBUT).MethodsThe included eyes were divided into three subgroups according to TBUT (group 1: TBUT ≤ 5 s, group 2: 5 s < TBUT ≤ 10 s, and group 3: TBUT > 10 s). All eyes were imaged separately thrice by two operators to obtain the thickness maps (TMs) of the cornea and corneal epithelium based on spatial zones encompassing a 9-mm-diameter area. Each TM consisted of 25 areas. Intraoperator (repeatability) and interoperator (reproducibility) standard deviations (Sws), coefficients of variation (CoVs), and intraclass correlation coefficients (ICCs) among the tests were calculated and compared in all the areas.ResultsAltogether, 132 eyes of 67 subjects were included (50, 47, and 35 eyes in groups 1, 2, and 3; respectively). The ICCs of corneal epithelial thickness and corneal thickness were > 0.75 in most of the areas. Pairwise comparisons showed that AS-OCT exhibited lower repeatability in group 1 than in groups 2 and 3 (P < 0.05). However groups 2 and 3 showed similar results. Sws and CoVs of corneal epithelial thickness exhibited no significant interoperator differences. While no significant differences were observed in corneal thickness in most of the areas.ConclusionsTBUT significantly influences the repeatability of corneal and corneal epithelial thickness measurements. Poor tear film stability requires careful evaluation of corneal epithelial thickness.

Changes in corneal epithelial irregularity following treatment with artificial tears.

Dry eye sufferers have a highly irregular corneal epithelial surface compared with those without dry eye. This study demonstrated that corneal epithelial thickness irregularity can be significantly reduced after as little as 48 hours following treatment with regular use of topical ocular lubricants. This study aimed to compare changes in corneal epithelial thickness irregularity factor (EIF) and ocular symptoms in a population with symptoms of dry eye before and up to 4 weeks after treatment with two commercially available lubricating eye drops versus saline. We conducted a prospective single-center, investigator-masked, randomized, parallel-group dispensing study. Participants with moderate to severe symptoms of dry eye (Ocular Surface Disease Index score >23 at baseline) were enrolled and randomly assigned to receive either 0.15% hyaluronic acid + hydroxypropyl guar, 0.2% hyaluronic acid, or saline (16 in each group). Corneal epithelial thickness measurements were obtained along vertical and horizontal CASIA SS-1000 Optical Coherence Tomography scans at baseline and after 48 hours, 2 weeks, and 4 weeks. The Ocular Surface Disease Index questionnaire was administered at baseline, 2 weeks, and 4 weeks. Forty-eight participants (male-to-female ratio, 17:31) completed the study. Horizontal EIF was significantly lower at all follow-up visits compared with baseline (p=0.001), but there were no significant differences between study eye drops (p=0.34). No significant difference in vertical EIF was observed over time (p=0.32) or between eye drops (p=0.08). Ocular symptoms significantly improved after 2 and 4 weeks of treatment compared with baseline (p<0.001), but no differences were observed between eye drops (p=0.46). All treatments were effective for reducing EIF along the horizontal meridian 48 hours after initiation of treatment, and improvements were maintained for 4 weeks. Improvements in ocular symptoms were observed with all study treatments.

Corneal Characteristics of Myopic Malay School Children and Their Association with Axial Length.

Corneal characteristics are unique to each eye and can vary among different levels of refractive errors. However, minimal data are available in the literature on corneal characteristics in myopic Malay school children including the difference between the low myopic group and the moderate myopic group. Therefore, this study aims to determine the corneal characteristics of myopic Malay school children and their associations with axial length. A total of eighty-four data samples were extracted from forty-two myopic Malay school children. Measurements of the central corneal thickness (CCT), corneal curvature, corneal diameter, and axial length were measured using Lenstar LS900, a non-contact optical biometer. Data were later stratified by the spherical equivalent refraction (SER) into a low myopic group and a moderate myopic group, and paired t-test were employed to determine the differences in the corneal characteristics between these two groups. Univariate and multivariate linear regressions were performed to identify factors that are significantly associated with axial length. There was no significant difference in the CCT, corneal curvature and corneal diameter between the low myopic group and the moderate myopic group (t82=0.015, P=0.99), (t82=-0.802, P=0.43) and (t82=-0.575, P=0.57), respectively. Pearson univariate correlation analysis found that axial length significantly correlated with corneal curvature (r=-0.765, P<0.001) and corneal diameter (r=0.614, P<0.001) but no significant correlation found with CCT (r=0.046, P=0.68). Multiple regression analysis showed that axial length was significantly associated with a flatter corneal curvature (P<0.001), older age (P<0.001) and larger corneal diameter (P=0.02). This study reported the corneal characteristics in myopic Malay school children and its associations with axial length. Results of this study can serve as a reference value for the myopic Malay schoolchild population.

Assesment of Corneal Thickness in Type II Diabetic Patients Ageing between 40 to 60 Years

Objective: To assess the corneal thickness of type 2 diabetic patients ageing between 40 to 60 years. Methodology: This was cross sectional study in nature and data was collected from tree tops hospital and university of Lahore. After informed consent, all patients diagnosed with type 2 diabetes were included in this study followed by measurement of corneal thickness. The data was collected regarding age, duration of diabetes, level of HbA1c test result and medications. When it came to entering and analyzing the data, IBM Spss version was employed. Pearson’s correlation test was applied to find the significance of data. P-value less than 0.05 was considered as significant. Results: There were total 104 patient with age ranges between 40 years to 60 years. In this research there were 58 persons who were suffering type 2 diabetes from 5 years (55.8%). There 18 and 18 (17.3%) patients were suffering from the diabetes for last 10 and 15 years respectively. Only 10 patients had diabetes for last 20 years. The difference in corneal thickness values between the subsections of patients with no DR, with NPDR and PDR was statistically non-significant (p = 0.810). Pearson’s correlation analysis showed that duration of DM (r = 0.022, p = 0.809), HbA1c (r = 0.103, p = 0.251), and severity of DR (r = 0.022, p = 0.805) did not show any significant correlation with CCT. Conclusion: As the age of the patient increases the central corneal thickness is affected by these factors. Which results in loss or decreased vision and many other problems.

Intrasession repeatability and agreement of the anterior corneal assessment provided by a multidiagnostic device

ABSTRACT Clinical relevance Multidiagnostic systems have recently appeared on the market. Knowledge of the repeatability and validity of any instrument is mandatory before its introduction in clinical practice. Background The aim of this work is to examine the intrasession repeatability of anterior pole measurements provided by the multidiagnostic device Wave Analyzer Medica 700 (WAM700) and agreement with Pentacam measurements in normal eyes. Methods In the right eyes of 113 participants, three repeat measurements of central keratometry, central corneal thickness, anterior chamber depth and corneal eccentricity were made with the WAM700 and Pentacam in random order. Intrasession repeatability and agreement were determined. Results Employing WAM700, intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth was good (ICCs ≥ 0.992; CV 0.48–0.98%), yet worse than the values obtained for the Pentacam (ICCs ≥ 0.998; CV 0–0.33%). WAM700 showed excellent intrasession repeatability when used to measure the anterior chamber depth (Sw 0.03 mm). However, the repeatability of this device was inferior for central corneal thickness (Sw 4.24 μm) and keratometry measurements (Sw < 0.21 D) and was poor for corneal eccentricity (Sw 0.07; ICC 0.908; CV 14.58%). Agreement between WAM700 and Pentacam showed a high ICC for the keratometry measurements, central corneal thickness and anterior chamber depth (>0.972) but lower for corneal eccentricity (ICC 0.762). Conclusions In healthy eyes, the WAM700 multidiagnostic device showed good intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth measurements. Agreement between WAM700 and Pentacam was good for the anterior chamber depth measurement. However, these instruments cannot be considered interchangeable for keratometry, central corneal thickness and eccentricity readings.

Donor Cornea Storage Temperature: Investigation of the Time Period Immediately Before Cornea Transplantation Surgery

Purpose: Donor cornea storage temperature seems to affect tissue viability; however, the time period between removal from storage and transplant surgery has not been explored. We investigated the possible impact time at room temperature in the operating room may have on endothelial cell density (ECD) and corneal thickness (CT). Methods: In our simulation, transplant-ineligible corneas underwent 1 of 4 room temperature protocols. ECD (by specular microscopy) and CT (by anterior segment optical coherence tomography [OCT]), measured before and after protocols, were used to explore possible effects of time at room temperature. Control group tissue resided at room temperature only long enough for warming and subsequent ECD and CT measurements. Results: Corneas underwent one of the following protocols: 1) 17 (±1) minutes at room temperature (for baseline OCT measurements; n = 13) followed by 23 minutes at 35°C (to facilitate specular imaging, conducted for all 4 protocols), 2) 60 (±1) minutes (1 hour; n = 8) at room temperature, 3) 187 (±1) minutes (approximately 3 hours; n = 7) at room temperature, and 4) 416 (±1) minutes (approximately 7 hours; n = 7). Statistical analysis showed no significant difference in ECD change (P = 0.353) or CT change (P = 0.415) between protocol groups. Controlling for donor age and death-to-preservation time rendered no statistical significance. Conclusions: Time at room temperature did not seem to significantly influence ECD or CT measured soon after warming. Studies exploring ECD postoperatively and long-term graft survival are needed to assess the possible clinical impact of preoperative time at room temperature.

Corneal Tomography in a Commercially Available Optical Coherence Tomography Device and Comparison With a Rotating Scheimpflug Camera.

To compare the outcomes of corneal tomography obtained with an anterior-to-posterior segment optical coherence tomography device (Revo, Optopol Technologies Sp. z o.o.) and a rotating Scheimpflug camera (Pentacam AXL, Oculus Optikgeräte, Wetzlar, Germany). In healthy subjects, agreement in stereometric parameters commonly used in cataract and refractive surgery was assessed. Comparison between the devices was performed using correlation coefficients, the Bland-Altman method, and a paired t test. Results of right eyes of 78 patients (47 women) aged 25.24±5.56 years were analyzed. The flat and steep anterior keratometry values were significantly higher for Revo than Pentacam (43.65±1.58 D vs. 42.99±1.47 D; P = 0.000, and 44.53±1.57 D vs. 43.82±1.49 D; P =0.000, respectively) and showed excellent correlation ( r =0.978 and 0.974, respectively). The results for maximal keratometry manifested a higher difference (45.89±1.69 D vs. 44.27±1.51 D for Revo and Pentacam, P =0.000) but were also strongly correlated ( r =0.871). Revo showed significantly lower corneal thickness values than Pentacam, both for apex pachymetry (535.54±32.45 vs. 550.74±31.55 μm; P =0.000) and for thinnest pachymetry (522.58±32.16 vs. 547.25±31.95 μm; P =0.000). The correlation coefficients for anterior and posterior corneal elevation at the thinnest point showed weak positive correlation ( r =0.179 and 0.185), while the correlation for corneal asphericity was moderate ( r =0.317). There was a significant difference between keratometric values obtained with Revo and the Pentacam AXL, although the measurements showed excellent correlation. Similar results were found for corneal thickness measurements, but not for corneal surface elevation and corneal asphericity.

The biomechanical e‐staging—In vivo assessment of corneal biomechanics in keratoconus

Aims/Purpose: Keratoconus (KC) is biomechanically characterized by a decreased resistance to deformation when compared to healthy corneas. The aim of this presentation is to give an overview about the development and clinical application of the recently introduced Homburg Biomechanical E‐Staging (BEST) for KC.Methods: The Corvis ST (Oculus, Germany) non‐contact pneumotonometer measures the corneal deformation after applying a standardized air puff. It calculates the quasi‐binary indices Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI) to separate healthy from ectatic corneas, without, however providing a biomechanical KC severity stage. The Homburg BEST based on the linearized CBI provides information about biomechanical KC severity in form of E‐stages 0 to 4, thus augmenting the existing tomographic ABCD KC classification by including corneal biomechanics. Several studies and results about the development and clinical application of the Homburg BEST are presented.Results: The Homburg BEST was developed based on two independent KC datasets (Homburg: n = 448, Milano/Rio: n = 860). Since 2022, it has been integrated into the Corvis ST software, thus providing a biomechanical KC severity and progression assessment. The software based on several individual biomechanical parameters indicates KC progression like tomographic progression parameters. However, it is influenced by corneal thickness measurements, increases within the first postoperative months after corneal crosslinking (CXL) and indicates postoperative KC stabilization more than 1 year after CXL. Intracorneal ring segment implantation permanently affects corneal thickness in the midperiphery and contributes to slightly higher postoperative BEST values.Conclusions: Although with limitations, the Homburg BEST enables a biomechanical staging and progression assessment in KC by considering several biomechanical parameters as an addition to the previously purely tomographic or even topographic analysis.

Evaluation of eye and serum findings in different waters in rabbits by drowning and submersion modeling.

This study investigated serum, vitreous, and anterior chamber fluid electrolyte changes, corneal thickness (CT), corneal volume (CV), anterior chamber volume (ACV), and anterior chamber depth (ACD) as an auxiliary diagnostic method in the identification of drowning in fresh or salt water. The study used 35 healthy, adult, male, white New Zealand rabbits, seperated into five groups (control, saltwater drowning (SWD), saltwater immersion (SWI), freshwater drowning (FWD), freshwater immersion (FWI)). CT, CV, ACV, and ACD measurements were made with Pentacam topography at 0, 2, and 4 h in all groups. Magnesium (mg), sodium (Na), and chlorine (Cl) were measured in the blood at 0 and 2 h, and in blood, vitreous fluid, and humor aqueous at 4 h. It was determined that CT, CV, ACV, and ACD are not of great value in drowning diagnosis and are affected by the fresh or salt water rather than drowning. Vitreous Na, Cl, and Mg levels are ineffective in determining drowning after one h. Anterior chamber fluid may provide valuable information in the differentiation freshwater - saltwater drownings at the 4th h in corpses retrieved from water. Anterior chamber fluid Na and Cl levels, especially in corpses removed from salt water, can be an easily used test that can help diagnose drowning.

Repeatability and agreement of AOCT-1000 M, RTVue XR and IOL master 500 in measuring corneal thickness mapping and axial length applying principle of optical coherence tomography

PurposeTo evaluate the repeatability and agreement of Fourier-domain optical coherence tomography (AOCT-1000 M and RTVue XR) and partial coherence interferometry biometer (IOL Master 500) in measuring corneal thickness mapping and axial length respectively.MethodsCorneal thickness was measured by AOCT-1000 M and RTVue XR. Axial lengths were measured by AOCT-1000 M and IOL Master 500. The repeatability and agreement of corneal thickness and axial length were calculated in two groups of devices. The intraclass correlation coefficient (ICC) was used to verify the repeatability of the device. The 95% confidence interval of the difference compared to the set cut-off value was used to verify the agreement between the two devices.ResultsA total of 60 subjects with 58 eyes were included. The central corneal thickness measured by AOCT-1000 M and RTVue XR were 504.46 ± 42.53 μm and 504.43 ± 42.89 μm respectively. The average difference between groups was 0.03 ± 4.58 μm, and the 95% confidence interval was (-1.17, 1.24), which was far less than the set threshold value of 15 μm (P < 0.001). Both RTVue XR and AOCT-1000 M had very good ICC values of central corneal thickness (0.998 and 0.994, respectively). The average axial lengths measured by AOCT-1000 M and IOL Master 500 were 24.28 ± 1.25 mm and 24.29 ± 1.26 mm respectively and the 95% confidence interval was (-0.02, 0.01), which was less than the set threshold value of 0.15 mm (P < 0.001). The ICC for both devices were 1.000.ConclusionGood repeatability and agreement were seen in measurements of central corneal thickness and axial length by AOCT-1000 M.

Corneal epithelial thickness mapping by optical coherence tomography in normal and early keratoconic eyes

Background Keratoconus (KC) is a noninflammatory disease causing anatomical deformity of the cornea and is manifested by marked conical protrusion in addition to thinning of the corneal central part. There are currently no standardized screening criteria for KC, making early diagnosis difficult. Early diagnosis aids in stopping progression and better management. It has been proposed that spectral domain optical coherence tomography (SD-OCT) has a diagnostic advantage in the early detection of corneal thickness changes in early KC. Aim Detection of corneal epithelial thickness changes in early KC eyes versus normal eyes using SD-OCT. Methods The research involved 30 eyes with early KC and 30 eyes from healthy control patients. Both groups underwent detailed ophthalmological examination and measurement of regional corneal epithelial thickness with anterior segment SD-OCT. Results In the cases group, corneal epithelium thickness decreased significantly in all regions tested. Additionally, all parameters of the pentacam pachymetry indices showed a statistically significant increase in the cases group. All of the thinnest pachymetry at central 5 mm and 7 mm Area Under the Curve (AUC=0.822 and 0.804), the location Y at central 5 mm and 7 mm (AUC=0.796 and 0.738), the minimum-maximum at central 5 mm and 7 mm (AUC=0.878 and 0.934), and the standard of deviation at central 5 mm and 7 mm (AUC=0.935 and 0.941) showed a statistically significant predictive value for differentiation KC cases from control (P &lt; 0.001), with the highest AUC reported with the standard of deviation. The tested corneal thickness in various regions correlated positively and statistically significantly with pentacam pachymetry indices. Conclusions Early KC is associated with corneal thinning and increased pentacam pachymetry index parameters. The changes detected by pentacam pachymetry and epithelial thickness as detected by SD-OCT showed a significant correlation.

Comparison Between Ocular Biometric Parameters and Intraocular Pressure With and Without Contact Lenses.

To compare the values of central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), vitreous length (VL), axial length (AL), and corneal-compensated intraocular pressure performed with and without contact lenses (CL). Forty volunteer participants (16 men and 24 women, 24.2±2.9 years) were recruited. In a single visit, participants underwent autorefraction, keratometry, biometry, topography, pachymetry, and tonometry with the naked eye (without CL). Then, biometry, pachymetry, and tonometry were repeated twice wearing two CL (somofilcon A and nesofilcon A) fitted in a random order. Many of the ocular biometric values were affected by the use of CL during measurements (paired t test; all P ≤0.003), except for LT and VL (Wilcoxon test; both P ≥0.272). Corneal-compensated intraocular pressure was also affected by contact lens wear during measurements, obtaining lower values when wearing them (Wilcoxon test; all P ≤0.001). Central corneal thickness, ACD, AL, and corneal-compensated intraocular pressure measurements cannot be performed while wearing CL. However, LT and VL measurements were not affected by any contact lens use. In addition, it was observed that ACD results from both devices are not interchangeable either when measured with the naked eye or using any contact lens.

Effect of Cycloplegia on Anterior Segment Structures and Scleral Thickness in Emmetropic Eyes.

Purpose: To evaluate the effects of topical cyclopentolate hydrochloride-induced cycloplegia on anterior segment biomechanics in emmetropic eyes using anterior segment-optical coherence tomography (AS-OCT). Methods: Twenty-five emmetropic eyes of 25 volunteers were included. All underwent central corneal thickness (CCT) and anterior chamber depth (ACD) measurements. Anterior scleral thickness (AST) was measured at the level of the scleral spur (SS)(AST-0), 1,000 μm posterior of the SS (AST-1), and 2,000 μm posterior of the SS (AST-2) in the nasal and temporal quadrants using AS-OCT. All measurements were repeated after cycloplegia. Results: The mean age was 30.6 ± 12.4 (8-45) years. The mean CCT did not significantly change after cycloplegia (P = 0.7). The mean ACD was significantly increased [3.3 ± 0.2 (2.7-3.9) to 3.7 ± 0.3 (3-4.2) μm; P = 0.001]. In the nasal quadrant, the mean AST-1 and AST-2 were 512.3 ± 34.4 (433-570) and 529.6 ± 34.2 (449-599); decreased to 478 ± 26.8 (423-530) and 486.2 ± 28.3 (422-544) μm, respectively, after cycloplegia (P = 0.00; P = 0.00). In the temporal quadrant, the mean AST-1 and AST-2 were 522.5 ± 24.7 (473-578) and 527.2 ± 39.9 (450-604); decreased to 481.1 ± 33.7 (421-550) and 484.6 ± 26.6 (433-528) μm, respectively (P = 0.00; P = 0.00). There was no significant difference in AST-0 after cycloplegia in both quadrants [from 697.5 ± 46 (605-785) to 709.5 ± 64.7 (565-785) for nasal and from 718.4 ± 40.1 (632-796) to 722.9 ± 60.6 (596-838) for temporal; P = 0.2; P = 0.3, respectively]. Conclusion: After cycloplegia, there was a significant thinning of ASTs posterior to SS and a slight increase in AST in the SS level. ACD deepened after cycloplegia, and there was no significant change in CCT. Cycloplegic agents temporarily inhibit ciliary muscle contraction and may affect anterior segment parameters and sclera. Inhibition of forward-inward movement of the ciliary body by cycloplegia affects ASTs and ACD by causing a change in the mechanical force of the ciliary muscle on the sclera.

Comparison of the Central Corneal Thickness between a Scheimpflug Imaging-Based Device and an Optical Measurement-Based Device

Background Central corneal thickness is a critical parameter in corneal evaluation for a wide range of purposes in ophthalmology such as refractive surgeries including LASIK, cataract surgeries to assess endothelial pump function preoperatively to preserve the corneal transparency, and glaucoma in terms of diagnosis, management and follow up to avoid over/underestimation of intraocular pressure due to variations in CCT. Aim of the Work The study will investigate the discrepancy in measuring the CCT between Scheimpflug imaging using the Nidek AL-Scan and optical pachymetry using the Nidek Specular Microscope CEM-530. Patients and Methods In our study, we compared CCT measurements of both devices among 70 eyes of 35 normal subjects with a nonsignificant past ocular history. All subjects attended Ophthalmology Department at Ain Shams University Hospitals and all measurements were taken by the same examiner at the same time of the day. Our study is an observational comparative crosssectional study for six months in Ain Shams University Hospitals, Cairo, Egypt after approval of the research ethical committee on normal people without any history of ocular pathology except for refractive errors. Results The mean age of the study subjects was 29.49 ± 7.98 years (range 20-48 years). Regarding age, sex, and refraction, there was no statistically significant difference between CCT measurements by each individual device. However, there was a statistically significant difference between CCT measurements when compared by both devices. The difference between the mean ± SD of both devices was 7.17 ± 0.98 µm. Conclusion There is a statistically significant difference in central corneal thickness measurement between Nidek AL-Scan and Nidek Specular Microscope CEM-530. Several studies are needed to further correlate CCT with other parameters measured by both devices, namely anterior chamber depth and axial length.