Epithelial Thickness Measurements Research Articles

Blepharoptosis and corneal epithelial thickness alterations, is there any relation?

BackgroundTo compare the epithelial thickness map of ptotic eyes of blepharoptosis patients with contralateral non- ptotic eyes.MethodsUnilateral blepharoptosis patients were enrolled consecutively. Patients were underwent full ophthalmologic examination and their demographic data such as age and gender and specific ptosis findings e.g. the cause and duration, MRD-1, and levator palpebralis superioris function were registered. Anterior segment imaging for epithelial thickness measurements was done using the Avanti RTVue-XR platform. The corneal epithelial thickness maps of ptotic and non-ptotic eyes were compared.Results44 patients with unilateral blepharoptosis were included in the study. 27 (61.4%) of them were female and 17 (38.6%) cases were male. The mean of the patients’ ages was 24.40 ± 15.16 years. Ptotic eyes had significantly thinner superior (p = 0.000), superior-temporal (p = 0.000) and superior-nasal (p = 0.005) sectors of the cornea and slightly thicker corneal epithelium (CE) in the inferior-nasal sector. The correlation of difference of superior-inferior CE was evaluated with different parameters including patient’s age (p = 0.457), type of blepharoptosis (p = 0.786), duration of blepharoptosis (p = 0.477) and MRD1 (p = 0.248), but no correlation was found.ConclusionsThis study revealed that lid position in blepharoptosis may have effects on the corneal epithelial thickness map. Because of the lower position of upper eyelid, a thinning effect on superior corneal sectors may happen.

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.

Intraoperative variability of corneal epithelium thickness in photorefractive keratectomy

PurposeTo evaluate the intraoperative central corneal epithelial thickness (ET) as measured by optical coherence pachymetry (OCP) in myopic eyes undergoing alcohol-assisted photorefractive keratectomy (PRK).MethodsA retrospective review of patients who underwent alcohol-assisted PRK was performed. Data were abstracted on age, gender, contact lens (CL) wear, preoperative refractive errors, keratometry, topographic and ultrasonic pachymetry, and intraoperative OCP measurements before and after epithelium removal. The central ET was calculated by subtracting OCP measurement after epithelium removal from the OCP measurement prior to epithelium removal.ResultsThe study comprised of 162 consecutive eyes from 81 patients. Mean age was 26.73 ± 6.47 years, 50.6% were males. CL was used in 92 eyes (56.8%). The mean sphere and spherical equivalent were −3.60 ± 1.84 D and −3.26 ± 1.85D, respectively. The mean intraoperative ET was 58.22 ± 17.53 µm (range, 15–121µm). Fifty-five percent of the eyes had an ET measurement above or below the range of 40-60µm. ET was significantly higher in the second operated eye compared to the first operated eye (p = 0.006), and an association was found to CL-wear (p = 0.03). There was no significant difference in thickness between genders (p = 0.62), and no correlation to patient age (p = 0.45, rp = 0.06), refractive errors (p > 0.30,rp=−0.07–0.08), nor keratometry(p > 0.80, rp=−0.01− (−0.02)).ConclusionThe intraoperative assessment of ET in alcohol-assisted PRK showed a high variability of the central corneal epithelium, with a significant difference between the first and second operated eyes. This difference may have implications when the epithelium is not included in the surgical planning in surface ablation.

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.

Evaluation of Neuromuscular Morphometry of the Vaginal Wall Using Protein Gene Product 9.5 (Pgp 9.5) and Smooth Muscle α-Actin (Sma) in Patients with Posterior Vaginal Wall Prolapse.

Background and Objectives: This study aims to compare the neuromuscular structure of the vagina in women with posterior vaginal wall prolapse with the neuromuscular structure of the vagina in women without prolapse, to determine the difference, and to demonstrate the role of neuromuscular structure in the physiopathology of prolapse. Materials and Methods: In this prospective study, women aged between 40 and 75 years who had not undergone any vaginal surgery and had not undergone any abdominal prolapse surgery were included. Thirty-one women diagnosed with rectocele on examination were included in the study group. Thirty-one patients who underwent vaginal intervention and hysterectomy for reasons other than rectocele (colposcopy, conization, etc.) without anterior or posterior wall prolapse were included in the control group. Biopsy material was obtained from the epithelium of the posterior wall of the vagina, including the fascia that fits the Ap point. Immunohistochemical staining with Protein Gene Product 9.5 and smooth muscle α-actin was performed in the pathology laboratory. The epithelial thickness measurement and smooth muscle density parameters obtained with these immunohistochemical stainings were compared between the two groups. The collected data were analyzed using the SPSS 23 package program. p values less than 0.05 were considered statistically significant. Results: In the control group, muscle thickness and the number of nerves per mm2 of fascia were statistically significantly higher than in the study group (p < 0.05). Conclusions: We found that smooth muscle tissue and the number of nerves per mm2 of fascia were decreased in posterior vaginal wall prolapse compared to the general population. Based on the correlation coefficients, age was the parameter that most affected the degree of prolapse, followed by parity, number of live births, and number of vaginal deliveries.

Repeatability of ANTERION in subjects with keratoconus

Aims/Purpose: The aim of this study was to study the repeatability of ANTERION in subjects diagnosed with keratoconus.Methods: The subjects selected had a previous diagnosis of keratoconus. These subjects were divided into three groups, according to the keratoconus treatment: subjects without treatment, intrastromal ring implantation and crosslinking. Subjects with pathologies with ophthalmological repercussion or previous surgeries were excluded.Three measures were performed with ANTERION in patients with keratoconus to evaluate the repeatability. These exams were performed with Cataract and Metricts module; therefore, six measurements were performed per patient and eye.Results: The parameters that showed values of coefficient of variation (CV) &gt;5% in all the evaluated groups were: the vertical coma value, the difference between the thickness of the inferior–superior stroma and the eccentricity of the anterior and posterior corneal surface. In the groups with intrastromal ring segments and crosslinking, a CV &gt;5% was obtained in the measurements of the minimum epithelial thickness and in the difference between the inferior–superior epithelial thickness. In the crosslinking and untreated groups, a CV &gt;5% was obtained in the horizontal coma value. In the groups with intrastromal ring segments and without treatment, a CV &gt;5% was obtained in the corneal RMS value and in the Score, which gives a value of the degree of keratoconus.The subjects implanted with intrastromal rings segments, a CV &gt;5% was obtained in the measurements of the epithelial thickness at the point of greatest thickness.Conclusions: A parameter was considered to show low repeatability when its CV was &gt;5%. The topographic measurements of K corneal and elevation values show good repeatability in subjects diagnosed with keratoconus. However, ANTERION shows a low repeatability in aberrometric values, and in measurements related to the stage and progression of the keratokonus.

Diagnostic Accuracy of Corneal and Epithelial Thickness Map Parameters to Detect Keratoconus and Suspect Keratoconus.

To establish the diagnostic accuracy of corneal and epithelial thickness measurements obtained by spectral-domain optical coherence tomography (SD-OCT) in detecting keratoconus (KC) and suspect keratoconus (SKC). This retrospective study reviewed the data of 144 eyes separated into three groups by the Sirius automated corneal classification software: normal (N) (n = 65), SKC (n = 43), and KC (n = 36). Corneal thickness (CT) and epithelial thickness (ET) in the central (0-2 mm) and paracentral (2-5 mm) zones were obtained with the Cirrus high-definition OCT. Areas under the curve (AUC) of receiver operator characteristic (ROC) curves were compared across groups to estimate their discrimination capacity. ROC curve analysis revealed excellent predictive ability for ET variables: minimum (Min) ET (0_2), minimum-maximum (Min-Max) ET (0_2), superonasal-inferotemporal (SN-IT) ET (2_5), Min-Max ET (2_5), and Min ET (2_5) to detect keratoconus (AUC > 0.9, all). Min-Max CT (0_2) was the only CT parameter with excellent ability to discriminate between KC and N eyes (AUC = 0.94; cutoff = ≤-32 μm). However, both ET and CT variables were not strong enough (AUC < 0.8, all) to differentiate between SKC and N eyes, with the highest diagnostic power for Min-Max ET (2_5) (AUC = 0.71; cutoff = ≤-9 μm) and central corneal thickness (CCT) (AUC = 0.76; cutoff = ≤533 μm). These results demonstrate that OCT-derived CT and ET are able to differentiate between KC and N eyes, with a high level of certainty. However, Min-Max ET (2_5) was the parameter with the highest ability to detect suspect keratoconus.

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 Pulsed and Continuous Accelerated Corneal Cross-Linking Protocols.

To compare between two accelerated corneal cross-linking (A-CXL) protocols in the management of keratoconus (KC) as regard to the extent of corneal treatment. This retrospective, comparative study included patients having mild to moderate, progressive KC. The study population was divided into two groups; group 1 enrolled 103 eyes of 62 patients who received pulsed light A-CXL (pl-CXL) at a power of 30 mW/cm2 with an irradiation time of 4 minutes, while group 2 comprised 87 eyes of 51 patients who received continuous light A-CXL (cl-CXL) at a power of 12 mW/cm2 with an irradiation time of 10 minutes. Recordings of the central and peripheral demarcation line depths (DD), and the maximum (DDmax) and minimum (DDmin) DD, using anterior segment optical coherence tomography, were compared between the two studied groups one month after the treatment protocol. Treatment stability was also evaluated pre and postoperatively (one year following surgery) by comparing the refractive and keratometric outcomes in both groups. The differences between the preoperative corneal thickness (minimum and central) and the epithelial thickness measurements between both groups were not statistically significant. Although group 1 had slightly larger central DD (223.4 ± 62.3 um), DDmax (240.4 ± 61.8 um), and DDmin (201 ± 54 um) than those of group 2 (221.8 ± 37 um, 229.1 ± 38.4 um, and 212 ± 37.2 um, respectively), the differences between both groups' measurements were not statistically significant. Also, the two groups showed statistically insignificant differences regarding the subjective refraction and the average and maximum keratometry pre and postoperatively, denoting visual, refractive, and keratometric stability in both groups. Longer duration cl-CXL seems to be as effective as pl-CXL regarding both postoperative stability and the extent of corneal tissue penetration by the ultraviolet treatment.

Repeatability of corneal pachymetry and epithelial thickness measurements with spectral-domain optical coherence tomography (SD-OCT) and correlation to ocular surface parameters.

To assess the repeatability of corneal pachymetry and epithelial thickness measurements with spectral-domain optical coherence tomography (SD-OCT) and identify correlations between epithelial thickness and ocular surface parameters. Adults who happened to have prolonged computer use were recruited, excluding those with conditions interfering with corneal measurements or tear production. All subjects filled in the ocular surface disease index (OSDI) questionnaire. Three consecutive measurements of central and peripheral corneal and epithelial thickness were performed with SD-OCT (RTVue XR). Schirmer test I and tear film break-up time (TBUT) were performed. Repeatability was evaluated with intraclass correlation coefficient (ICC), coefficient of variation and repeatability limit. Spearman correlation was used for non-parametric variables. 113 eyes of 63 subjects were included in the study. ICC was ≥ 0.989 for all corneal and ≥ 0.944 for all epithelial pachymetry segments. The best repeatability was found centrally and the worst superiorly both for corneal and epithelial measurements. Central epithelial thickness was weakly correlated with Schirmer test I (rho = 0.21), TBUT (rho = 0.02), OSDI symptoms and OSDI score (rho <|0.32|). OSDI symptoms and OSDI score were weakly correlated with Schirmer test I (rho <|0.3|) and TBUT (rho <|0.34|). RTVue XR measurements of corneal and epithelial thickness are highly repeatable in all segments. The lack of correlation between epithelial thickness and ocular surface parameters could suggest the assessment of epithelial integrity with reliable methods such as SD-OCT.

Role of corneal epithelial mapping, Corvis biomechanical index, and artificial intelligence-based tomographic biomechanical index in diagnosing spectrum of keratoconus.

The aim of the study was to evaluate the utility of epithelial mapping, Corvis biomechanical index (CBI), and tomographic biomechanical index (TBI) in diagnosing the spectrum of keratoconus (KC). This was a retrospective study where KC subjects with an age between 11 and 50 years were enrolled. Subjects with ocular diseases, history of previous corneal surgery, corneal scars or hydrops, ocular trauma, ocular surface disorder, systemic disease, and poor-quality scans were excluded. KC was classified using Belin ABCD classification system. Epithelial thickness, corneal tomography, and corneal biomechanical measurements were recorded using Fourier-domain optical coherence tomography Avanti with corneal adaptor module, Pentacam HR, and Corvis® ST, respectively. To understand the utility of various corneal parameters in diagnosing spectrum of keratoconus, cutoff values for epithelial thickness at the thinnest location and its standard deviation (SD) were considered 45 and 3 microns, respectively, CBI of 0.5 and TBI of 0.29 was considered. Sixty-five eyes (45 - KC, 10 - subclinical KC (SBKC), and 10 - forme fruste [FF]) of 34 patients with a mean ± SD age of 30.73 ± 5.71 were included. In our keratoconic sample, epithelial mapping alone helped diagnose the 77.77% of cases, however, when combined with CBI, it helped diagnose 95.5% cases and when combined with TBI, it was useful in diagnosing 100% of cases. In SBKC group, 40% of cases were detected by epithelial mapping alone, and when combined with CBI, it helped diagnose 70% of cases and TBI further helped diagnose 90% of cases. We did not see any role of epithelial mapping in detecting FFKC cases whereas CBI and TBI helped diagnose 60% and 90% of cases, respectively. The utility of epithelial mapping as a solitary tool is limited in detecting the spectrum of KC, especially SB and FFKC. However, combining it with corneal biomechanical parameters could help improve the efficacy of diagnosis of KC.

Differential Diagnosis of Keratoconus Based on New Technologies.

Keratoconus (KC) must be distinguished from other corneal ectatic diseases and thinning disorders for stage-appropriate and suitable management of each condition. The most relevant corneal pathologies that may imitate the tomographic KC pattern are pellucid marginal degeneration (PMD), keratoglobus, posterior keratoconus, and Fuchs-Terrien marginal degeneration (FTMD). In moderate cases of KC, differentiation is typically possible using slit lamp examination and corneal tomography with evaluation of the location of the corneal thinning region. In early cases, however, differential diagnosis may be more challenging since the cornea may look relatively normal. In severe cases, the extended area of corneal thinning also complicates differentiation. Biomicroscopic findings cannot always give all the information needed to distinguish KC from related ectatic corneal conditions. The aim of this work is to discuss contemporary techniques and findings to assist physicians to identify the correct diagnosis. Corneal topography has been used in recent decades as the main tool for imaging in ectatic corneal diseases. Moreover, Scheimpflug cameras (corneal tomographers), which analyze both anterior and posterior corneal surfaces, curvatures, pachymetry, elevation data, higher order aberrations, Fourier analysis of keratometric data, and corneal density have become the most promising tools for diagnosis and follow-up of ectatic diseases. A noninvasive air pulse tonometer in conjunction with an ultrahigh-speed Scheimpflug camera complements tomographic findings by analyzing biomechanical corneal properties. Α confocal microscopy system, which is a novel clinical technique for the study of corneal cellular structure, could contribute effectively in the same direction. Moreover, anterior segment optical coherence tomography (AS-OCT) creates cross-sections, which can be generated into a three-dimensional structure to produce corneal epithelial thickness (ET) measurements. ET mapping is increasingly recognized as a sensitive tool for the diagnosis of ocular surface disorders. Combining information of all these systems could lead to a more effective identification and differential diagnosis of ectatic corneal disorders.

Accurate In Vivo Bowman's Thickness Measurement Using Mirau Ultrahigh Axial Resolution Line Field Optical Coherence Tomography.

PurposeThe purpose of this study was to assess the accuracy, repeatability, and performance limits of in vivo Mirau ultrahigh axial resolution (UHR) line field spectral domain (LF-SD) optical coherence tomography (OCT) for the measurement of Bowman's and epithelial thickness, and to provide a reference range of these values for healthy corneas.MethodsVolunteers with no history and evidence of corneal disease were included in this study. An in vivo graph search image segmentation of the central cornea was obtained at the normal interface vector orientation. The Mirau-UHR-LF-SD-OCT system used has an axial resolution down to 2.4 µm in air (1.7 µm in tissue), with an A-scan speed of 204.8 kHz and a signal to noise ratio (sensitivity) of 69 (83) dB.ResultsNine volunteers were included, one of whom wore contact lenses. The repeatability of mean Bowman's and epithelial thicknesses were 0.3 and 1.0 µm, respectively. The measured 95% population range for healthy in vivo thickness was 13.7 to 19.6 µm for the Bowman's layer, and 41.9 to 61.8 µm for the epithelial layer.ConclusionsThe measured thicknesses of Bowman's layer and the corneal epithelium using the Mirau-UHR-LF-SD-OCT were both accurate, with the range for healthy in vivo thicknesses matching prior confocal and OCT systems of varying axial resolutions, and repeatable, equaling the best value prior reported.Translational RelevanceT1. Development of a commercially viable clinical UHR OCT technology, enabling accurate measurement and interpretation of Bowman's and epithelial layer thickness in clinical practice.

EPITHELIAL MAPPING AND TOPICAL ANTIGLAUCOMA TREATMENT: EARLY DETECTOR OF OCULAR SURFACE SUFFERING?

The corneal epithelium is one of the major structures that undergo changes to the ocular surface. It is for this reason that the central epithelial thickness measurement has been proposed as an objective indicator to monitor the health of the ocular surface. We report the case of a 60-year-old patient who has bilateral open-angle glaucoma under dual therapy and diffuse bilateral central epithelial thinning in epithelial mapping. Thickness variability can be correlated with patientÂ’s dry eye symptoms, and that epithelial thickness profiles could be used to monitor a patients response to treatment. The thinning is usually moderate and its exact therapeutic implication in terms of stopping or changing therapy remains to be determined by future studies.

Corneal epithelial thickness in keratoconus patients compared to healthy controls

In keratoconus (KC) aprogressive deformation and thinning of the cornea occurs. In contrast to Scheimpflug-based examinations, optical coherence tomography (OCT) can precisely measure the corneal layers separately, allowing separate analyses of corneal epithelial and corneal stromal thicknesses. The aim of this work was to analyze the corneal epithelial thickness measured by optical coherence tomography (OCT) in patients with KC in comparison to the corneal epithelial thickness in healthy subjects. The diagnostic value of the observed changes was evaluated. In aretrospective analysis 125eyes of patients with KC and 140eyes of healthy subjects were included. Corneal measurements were performed by OCT (Optovue, XR-Avanti, Fremont, CA, USA). Corneal stromal thicknesses and corneal epithelial thicknesses in different locations were measured and analyzed. There were significant differences in stromal and epithelial thickness measurements. Of the derived epithelial thickness parameters four showed agood discriminatory power between healthy controls and KC patients (area under the curve in the receiver operating characteristic analysis > 0.7). Patients with KC showed an altered epithelial thickness compared to healthy controls. The derived calculated parameters based on corneal epithelial thickness can distinguish between KC and ahealthy cornea.

An Evaluation of Central Corneal Epithelial Thickness and Central Corneal Thickness Determined On Optic Coherence Tomography Before and After Applanation Tonometry

Objective: To determine the changes in corneal epithelial thickness and central corneal thickness using optic coherence tomography taken after Goldmann applanation tonometry measurements. Material and Methods: The study included 25 patients who presented at our clinic for routine ophthalmological examination. Before taking tonometry measurements of the patients, epithelial corneal thickness and central corneal thickness values were determined using optic cohence tomography (OCT). The intraocular pressure (IOP) was measured with tonometry and then the corneal OCT measurements were repeated. All the OCT and tonometry measurements were taken by the same clinician. Results: Evaluation was made of 25 patients comprising 18 males and 7 females with a mean age of 36.6 years (range, 17-55 years). The mean epithelial corneal thickness was 52.58 microns before the applanation tonometry measurement, and 52.02 microns after the tonometry (p=0.059). Central corneal thickness was measured as mean 530.96 microns before tonometry and 529.88 microns after (p&amp;gt;0.05). No statistically significant difference was determined in the changes of both measurements. Following tonometry, a change was seen in corneal epithelial thickness, but not of a statistically significant level (p=0.059). Conclusion: The study results showed no statistically significant difference in the measurements of corneal epithelial thickness and central corneal thickness following applanation tonometry. Although not statistically significant, the difference seen in thickness indicates desquamation in the epithelial cells as a result of the procedure. This may cause complaints such as a reduction in visual acuity and the feeling of burning or pricking in the eye. If glasses are to be prescribed for patients, this should be taken into consideration and the examination should be made before the tonometry measurement. To the best of our knowledge, there has been no previous study in literature of central corneal epithelial thickness measured before and after tonometry, and therefore the results obtained in this study are the first on this subject.

Commentary: Usefulness of corneal epithelial thickness measurement.

Commentary: Usefulness of corneal epithelial thickness measurement.

Corneal and Epithelial Thickness Mapping: Comparison of Swept-Source- and Spectral-Domain-Optical Coherence Tomography.

Objective To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Enhanced Spectral-Domain-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes. Methods 30 normal eyes of 30 patients were assessed by 3 trained operators with ESD-OCT and SD-OCT. Results The central and minimum ET obtained with both devices were correlated: central ET, r = 0.86, p < 0.05; minimum ET, r = 0.72, p < 0.05. Compared with SD-OCT, ESD-OCT tended to underestimate these figures by 1.4 and 1.9 μm on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, r = 0.994, p < 0.05; minimum CT, r = 0.995, p < 0.05. ESD-OCT tended to overestimate these figures by 11 and 14 μm on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for ESD-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT. Conclusion ESD-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.

High-Resolution Quantitative Mapping of Macaque Cervicovaginal Epithelial Thickness: Implications for Mucosal Vaccine Delivery.

Vaginal mucosal surfaces naturally offer some protection against sexually transmitted infections (STIs) including Human Immunodeficiency Virus-1, however topical preventative medications or vaccine designed to boost local immune responses can further enhance this protection. We previously developed a novel mucosal vaccine strategy using viral vectors integrated into mouse dermal epithelium to induce virus-specific humoral and cellular immune responses at the site of exposure. Since vaccine integration occurs at the site of cell replication (basal layer 100-400 micrometers below the surface), temporal epithelial thinning during vaccine application, confirmed with high resolution imaging, is desirable. In this study, strategies for vaginal mucosal thinning were evaluated noninvasively using optical coherence tomography (OCT) to map reproductive tract epithelial thickness (ET) in macaques to optimize basal layer access in preparation for future effective intravaginal mucosal vaccination studies. Twelve adolescent female rhesus macaques (5-7kg) were randomly assigned to interventions to induce vaginal mucosal thinning, including cytobrush mechanical abrasion, the chemical surfactant spermicide nonoxynol-9 (N9), the hormonal contraceptive depomedroxyprogesterone acetate (DMPA), or no intervention. Macaques were evaluated at baseline and after interventions using colposcopy, vaginal biopsies, and OCT imaging, which allowed for real-time in vivo visualization and measurement of ET of the mid-vagina, fornices, and cervix. P value ≤0.05 was considered significant. Colposcopy findings included pink, rugated tissue with variable degrees of white-tipped, thickened epithelium. Baseline ET of the fornices was thinner than the cervix and vagina (p<0.05), and mensing macaques had thinner ET at all sites (p<0.001). ET was decreased 1 month after DMPA (p<0.05) in all sites, immediately after mechanical abrasion (p<0.05) in the fornix and cervix, and after two doses of 4% N9 (1.25ml) applied over 14 hrs in the fornix only (p<0.001). Histological assessment of biopsied samples confirmed OCT findings. In summary, OCT imaging allowed for real time assessment of macaque vaginal ET. While varying degrees of thinning were observed after the interventions, limitations with each were noted. ET decreased naturally during menses, which may provide an ideal opportunity for accessing the targeted vaginal mucosal basal layers to achieve the optimum epithelial thickness for intravaginal mucosal vaccination.

Repeatability of corneal and epithelial thickness measurements with anterior segment optical coherence tomography in keratoconus.

PurposeTo investigate the repeatability in corneal thickness (CT) and epithelial thickness (ET) measurements using spectral domain anterior segment optical coherence tomography (AS-OCT, REVO NX, Optopol) in keratoconus, and examine the effect of corneal crosslinking (CXL) on repeatability.MethodsA cross-sectional study of 259 eyes of 212 patients with keratoconus attending the corneal disease clinic at a university hospital tertiary referral center were enrolled. Two groups were analysed: eyes with no prior history of CXL (Group A) and eyes with prior CXL (Group B). Repeatability of measurements was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV).ResultsIn Group A, central corneal thickness (CCT) was 472.18 ± 45.41μm, and the ET was found to be the thinnest in the inferior-temporal aspect at 51.79 ± 5.97μm and thickest at the superior-nasal aspect at 56.07 ± 5.70μm. In Group B, CCT was 465.11± 42.28μm, and the ET was the thinnest at the inferior-temporal aspect at 50.63 ± 5.52μm and thickest at the superior aspect at 56.80 ± 6.39μm. When evaluating CT measurements, ICC was above 0.86 and 0.83 for Group A and Group B respectively. When evaluating ET measurements, ICC was above 0.82 for both groups. CXL had no statistically significant impact on the repeatability of measurements.ConclusionsAS-OCT provides repeatable CT and ET measurements in the central and peripheral cornea in patients with keratoconus. Repeatability is not affected by a history of CXL.