Corneal Profile Research Articles

Conjunctival and Corneal Endothelium Profile in a Sample of Healthy Electronic Cigarette Smokers

Objective: Though e-cigarette is thought of as a healthy alternative way of smoking, the unknown nicotine concentration level and chemical compounds from the aerosol mist and flavourings are potentially harmful and may exert irritation or damage to the ocular surface. Thus, a cross-sectional study was conducted to identify the conjunctival and corneal endothelium profile among healthy e-cigarette smokers, and the relationship between smoking behaviour with the conjunctival and corneal endothelium profile. Material and Methods: Seventeen healthy e-cigarette smokers and 17 non-smokers were recruited for this study where their palpebral redness, bulbar redness, limbal redness, conjunctival roughness, central corneal thickness, endothelial cell density, and coefficient of variation of endothelium cell area were assessed using slit lamp biomicroscope and specular microscope. Results: There was a non-significant, higher mean rank observed in the total palpebral redness, total bulbar redness, total limbal redness, total conjunctival roughness, central corneal thickness, endothelial cell density, and coefficient of variation of the endothelium cell area in e-cigarette smokers compared to non-smokers (p-value>0.05). Only smoking frequency and total palpebral redness showed a statistically significant, positive, and fair correlation (r=0.349, p-value=0.043), while no other smoking behaviour showed a significant correlation (p-value<0.05). Conclusion: The use of e-cigarettes showed no significant impact on the conjunctival and corneal profile among the users, but further research with comprehensive evaluation is required in a larger sample size of more established e-cigarette smoking profiles.

The Corneal Epithelial Thickness Profile in a Healthy Saudi Population.

Epithelial mapping appears to be a valuable technique for acorneal and refractive surgeon, useful for distinguishing corneas with the true presence of corneal ectasia from those that are suspicious.Interpreting the epithelial thickness map data requires an understanding of corneal epithelial thickness (CET) normal values and variable patterns. Unlike corneal thickness, epithelial thickness assessment with anterior segment optical coherence tomography (AS-OCT) seems to be influenced by gender and age. The study aimed to investigate the detailed mapping of CETcharacteristics in normal eyes from the Saudi population and to assess its variation with age and sex using anterior segment 7-mm-wide OCT (AS-OCT) scans. Regional epithelial thickness was assessed using an anterior radial scanning protocol with REVO NX (Optopol Technology S.A, Zawiercie, Poland) in 596 eyes of 298 individuals aged 10 to 98. CET maps in a 7 mm diameter wereautomatically generated by the built-in software, displaying thickness in 17 sectors divided into three zones, i) a central zone within the 0-2 mm diameter, ii) ring 1 zone, a paracentral (P-CET) zone from 2 to 5-mm, and iii) ring 2 zone, a midperipheral zone (MP-CET) from 5 to 7 mm. Ring 1 and 2 zones were further divided into eight sectors each, including superior (S), inferior (I), nasal (N), temporal (T), superonasal (SN), inferonasal (IN), superotemporal (ST), and inferotemporal (IT). An analysis was done on correlations between age and gender and the CET across different zones. Males and older adults had a substantially thicker CET than females and younger participants, with the C-CET measuring 59.2±4.5µm. In three zones, no interocular asymmetry was seen. Superiorly, CET is significantly thinner than inferiorly (p<0.05), with temporal zones being thinner than nasal zones (p<0.05). The C-CET increases with age in the seven groups of both genders, but its dependence on age is weaker in paracentral sectors; C-CET was 3.5% thicker in males. Paracentral nasal and inferior zones showed 2.2-3.6% thicker CET while the superior and temporal paracentral zones showed 3-5% thicker CET among males compared to females. From 17 CET zones of central 7 mm cornea the C-CET was affected by gender and age.The CET distribution in these healthy Saudis' eyes was non-uniform with the CET being thinner in the superior cornea.This finding could aid in predicting corneal diseases and planning refractive procedures.

Salzmann Nodular Degeneration in Ocular and Systemic Diseases.

This review aimed to evidence the predisposing conditions for Salzmann nodular degeneration (SND), where particular attention was paid to its association with ocular and systemic diseases. SND is a rare disease characterized by bluish-white nodules located in the mid-periphery of the cornea, which are otherwise completely clear. SND has been found in association with different systemic and ocular diseases, and it may have unilateral or bilateral presentation. Initial forms are only diagnosed occasionally as they are asymptomatic, whereas, in advanced disease, the visual acuity might be seriously impaired. Although SND is well described, its exact etiopathology is currently still unknown and is frequently misdiagnosed. It is associated with ocular surface inflammatory conditions and previous corneal surgery, and it has been described in different systemic diseases. Diagnosis is clinically based with slit lamp examinations, and instrumental assessments with corneal topography permit one to observe the alterations of the corneal profile, whereas anterior segment-optical coherence tomography (AS-OCT) is used to investigate the stromal depth of the nodules. Therapy might be conservative with the objective of improving the ocular surface homeostasis and surgical outcomes, where the aim is to restore the corneal regularity and visual acuity. Ophthalmologists should pay particular attention when detecting nodules in patients with ocular and non-ocular inflammatory diseases to guarantee the patient a timely diagnosis and a better therapeutic outcome. Additionally, collaboration between specialists who deal with treating patients suffering from disorders potentially associated with SND is recommended.

Comparative evaluation of biomechanical changes and aberration profile following accelerated collagen cross-linking using hypo-osmolar and iso-osmolar riboflavin: A prospective study.

To compare the changes encountered in corneal biomechanics and aberration profile following accelerated corneal collagen cross-linking (CXL) using hypo-osmolar and iso-osmolar riboflavin in corneal thicknesses of <400 and >400 microns, respectively. This is a prospective, interventional, comparative study involving 100 eyes of 75 patients with progressive keratoconus. Eyes were divided into two groups based on corneal thickness: group 1 included eyes with a corneal thickness of <400 microns who underwent hypo-osmolar CXL, and group 2 included eyes with a corneal thickness of >400 microns who underwent iso-osmolar CXL. Corneal biomechanical and aberration profiles were evaluated and compared between groups. In group 1, all higher-order aberrations (HOA) except secondary astigmatism significantly decreased from baseline; however, in group 2, only coma and trefoil decreased. The corneal resistance factor and corneal hysteresis significantly improved in both groups, which was significantly greater in group 2 than in group 1. The change in inverse radius, deformation amplitude, and tomographic biomechanical index was significantly improved in group 2 as compared to group 1. Improvement in corrected distance visual acuity and decrease in HOA were significantly better in the hypo-osmolar CXL group; however, the improvement in biomechanical strength of the cornea was significantly better in the iso-osmolar group.

Corneal endothelial safety profile in minimally invasive glaucoma surgery.

To compare 5-year corneal endothelial safety of 3 minimally invasive glaucoma surgery (MIGS) devices (iStent inject , Hydrus Microstent, CyPass Micro-Stent). U.S. multicenter trials. Post hoc 5-year analysis from prospective randomized single-masked pivotal trials. Mild to moderate open-angle glaucoma subjects received a MIGS implant with phacoemulsification (implant + phaco) or phaco alone (control). In addition, 5-year end points comparing the implant and control groups included proportion of eyes with significant endothelial cell loss (ECL) (>30% or ≥30% vs baseline) and mean endothelial cell density (ECD). Comparable proportions of eyes in the iStent inject + phaco and control groups had significant 60-month ECL (9.4% vs 6.3%, respectively, diff: 3.2%, 95% CI, -5.0% to 11.3%, P = .77). Hydrus (20.8% vs 10.6%, diff: 10.2%, 95% CI, 3.2% to 17.2%, P = .01) and CyPass (27.2% vs 10.0%, diff: 17.2%, 95% CI, 5.6% to 28.7%, P = .02) had more eyes with ECL vs controls (iStent inject 1.49X, Hydrus 1.96X, CyPass 2.72X vs controls). Mean ECD over 60 months for iStent inject was indistinguishable vs control, whereas greater ECL was observed primarily 3 months postoperative (Hydrus) or accelerated after 2 years (CyPass). No iStent inject or Hydrus subjects developed persistent corneal edema, whereas 7 CyPass-implanted eyes developed ECL-related complications. Through 5 years postoperative, there were no differences in proportion of eyes with significant ECL or mean ECD between the iStent inject and control groups. There was greater 5-year ECL and lower ECD in the Hydrus and CyPass groups vs controls. The Hydrus ECL rate mirrored control after 3 months; the CyPass ECL rate accelerated vs control.

The extraction and application of antisymmetric characteristics of the cornea during air-puff perturbations

BackgroundA non-contact tonometer is used to measure intraocular pressure, and studies have primarily relied on apex displacements to assess corneal properties. However, previous studies have overlooked the asymmetric characteristics of lateral corneal perturbations, leading to a gap in understanding of the lateral mechanical properties and its application. MethodTo investigate these lateral perturbations, we designed an experiment to sequentially record the corneal profiles when two consecutive air-puffs were applied at the center of the same cornea within a short period. Moreover, we used modal decomposition to decompose anterior surface profiles into symmetric and antisymmetric modes to comprehensively analyze the asymmetric characteristics. To extract mechanical properties, we utilized high-pass frequency analysis (>250 Hz) to filter out noise and errors. ResultsSymmetric modes between the two consecutive air-puffs exhibited major similarities during vibration; however, antisymmetric modes exhibited minor differences in lateral perturbations of asymmetric vibration. The antisymmetric modes might be related to air-puff misalignment and mechanical properties. Through applying frequency analysis, the mechanical properties could be proven at high frequencies and misalignment shown at low frequencies. Furthermore, we compared the corneal vibration profiles of 259 healthy participants and 50 patients with keratoconus. Their properties showed that the antisymmetric modes of the keratoconus group exhibited a completely opposite direction of deformation compared to that in the healthy group. ConclusionsOur proposed algorithm not only extracts antisymmetric characteristics but also offers valuable insights into decompose misalignment and mechanical properties of healthy and keratoconus corneas, presenting a new perspective for corneal biomechanics.

The Effect of Upper Eyelid Blepharoplasty on Corneal Tomography and Epithelial Profile

The Effect of Upper Eyelid Blepharoplasty on Corneal Tomography and Epithelial Profile

Scleral Shape and Its Correlation With Corneal Topographic Parameters: A Review

Purpose. This review paper aims to summarize the outcomes of the different studies investigating the correlation between corneal and scleral profiles, outline the relationship between corneal and scleral curvatures and asymmetry, and describe the correlation between corneal astigmatism and scleral toricity in regular and irregular corneas. Material and Methods. Literature was reviewed from PubMed. A total of 48 articles were specifically selected for the current study. Results. The scleral and corneal radii are directly correlated; the greater the corneal radius, the larger the scleral radius. The cornea and sclera become gradually flatter and asym- metric as the distance from the corneal optical line increases. Similar to the central cornea, the limbal area is more likely to be spherical. The horizontal asymmetry between the nasal and temporal areas is greater than the vertical asymmetry, with the nasal region of the ocular surface being the flattest. In eyes with keratoconus, the sclera is steeper, more asym- metric, and irregular. Cone decentration predicts asymmetric sclera. Corneal and scleral toricity are more likely correlated when corneal astigmatism is greater than 2.00 D. Conclusion. Some correlations were found between corneal and scleral topography; however, performing both corneal and scleral topography are necessary when fitting contact lenses. Further investigation is needed with larger groups matched in age, refractive error, and biometry and comparing smaller or steepest eyes (i.e., Asiatic population) with larger or flatter eyes. It would also be interesting to compare such correlations in primary and secondary ectasia, investigating whether the scleral shape changes in secondary ectasia. Keywords Corneal topography, scleral profile, ocular surface asymmetry, profilometry, ocular surface radii, contact lens fitting

Keratoconus tomographic indices in osteogenesis imperfecta

PurposeOsteogenesis imperfecta (OI) is a rare inherited disease affecting collagen-rich tissues. Ocular complications have been reported such as thin corneas, low ocular rigidity, keratoconus, among others. The purpose of this study is to characterize corneal tomographic features in OI patients compared to unaffected patients, with particular focus on commonly studied keratoconus indices.MethodsCross-sectional case–control study including 37 OI patients and 37 age-matched controls. Patients and controls underwent comprehensive ophthalmological examination including corneal Scheimpflug tomography with a Pentacam HR device (Oculus Optikgeräte GmbH, Wetzlar, Germany) to analyse and compare topometric, tomographic, pachymetric and Belin-Ambrósio Enhanced Ectasia Display III (BAD-D) data of both eyes of each patient.ResultsMost OI patients had type I disease (n = 24; 65%) but type III–VII patients were also included. Two patients had clinically overt bilateral keratoconus. OI patients had significantly higher maximum keratometry (45.2 ± 2.1 vs. 43.7 ± 1.2; p = 0.0416), front and back elevation (3.0 ± 3.3 vs. 2.1 ± 1.3, p = 0.0201; 11.1 ± 8.2 vs. 5.0 ± 3.7, p < 0.0001), index of surface variance (25.5 ± 13 vs. 17.4 ± 8.3; p = 0.0016), index of vertical asymmetry (0.21 ± 0.14 vs. 0.15 ± 0.06; p = 0.0215), index of height asymmetry (9.2 ± 14 vs. 6.0 ± 4.5; p = 0.0421), index of height decentration (0.02 ± 0.01 vs. 0.01 ± 0.01; p < 0.0001) and average pachymetric progression (1.01 ± 0.19 vs. 0.88 ± 0.14; p < 0.0001) readings. Thinnest corneal thickness and maximum Ambrósio relational thickness were significantly lower (477 ± 52 vs. 543 ± 26; 387 ± 95 vs. 509 ± 49; p < 0.0001). Two-thirds of OI patients had corneas with a minimum thickness < 500 µm. BAD-D value was significantly higher in OI patients (2.1 ± 1.4 vs. 0.9 ± 0.2; p < 0.0001).ConclusionOI patients showed significant changes in corneal profiles compared with healthy subjects. A high proportion of patients had tomographically suspect corneas when using keratoconus diagnostic indices. Further studies are warranted to assess the true risk of corneal ectasia in OI patients.

Corneal Epithelial Remodeling in a 6-Month Follow-up Period in Myopic Corneal Refractive Surgeries

To investigate corneal epithelial thickness changes during a 6-month follow-up period after transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). This prospective study included 76 eyes of 76 participants who underwent myopic refractive surgery (23 FS-LASIK, 22 SMILE, and 31 tPRK). Epithelial thickness and anterior curvature were averaged over 4 regions (subdivided into 25 areas) and measured by spectral-domain optical coherence tomography and Scheimpflug tomography before the operation (pre) and at 1 or 3 days (pos1-3d), 1 week (pos1w), and 1 month (pos1m), 3 months (pos3m), and 6 months (pos6m) postoperatively. The epithelial thickness of the three groups was similar in both the pre and pos6m (all P > .05), but the tPRK group fluctuated the most during the follow-up period. The largest increase was in the inferior-temporal paracentral area (7.25 ± 2.58 μm for FS-LASIK; 5.79 ± 2.41 μm for SMILE; 4.88 ± 5.84 μm for tPRK; all P < .001). Only the epithelial thickness of tPRK increased from pos3m to pos6m (P < .05), whereas all changes for FS-LASIK and SMILE were not significant (P > .05). A positive correlation of thickness changes with curvature gradient in the paracentral region of tPRK was found (r = 0.549, P = .018), but not in other regions in all groups. Epithelial remodeling followed different trends after different surgeries from the early postoperative stage onward, but exhibited similar values at pos6m. Although remodeling after FS-LASIK and SMILE stabilized by pos3m, it remained unstable at pos6m after tPRK. These changes may affect corneal profile and lead to deviation from the intended surgical outcome. [J Refract Surg. 2023;39(3):187-196.].

The Impact of Corneal Epithelial Thickening and Inhomogeneity on Corneal Aberrations After Small Incision Lenticule Extraction.

To investigate the corneal epithelial remodeling profile after small incision lenticule extraction (SMILE), the correlated explanatory variables, and its potential impact on corneal higher order aberrations (HOAs). This single-center study prospectively evaluated 75 right eyes of 75 patients scheduled for SMILE. An anterior segment optical coherence tomography device was used to automatically obtain central 6-mm corneal epithelial thickness (ET), total corneal HOAs, and individual Zernike components before and after surgery. The ET inhomogeneity over the central 3- and 6-mm cornea was quantified with coefficient of variance (CV). Both ET and CV significantly increased 1 month postoperatively (all P < .05). The stepwise multiple regression analysis showed that ET and CV were significantly correlated with preoperative ET and CV, respectively (all P < .01). The corrected spherical equivalent also significantly influenced ET and CV (all P < .01). Over the central 6-mm zone, the alterations of total corneal HOAs and individual Zernike components such as vertical coma (Z7) and spherical aberration (Z12, Z24) were significantly correlated with ET and CV (all P < .05). The SMILE-induced epithelial remodeling involved both ET and ET inhomogeneity. The modulation was associated with preoperative and treatment parameters, and exerted a significant impact on corneal HOA alterations especially over the central 6-mm cornea. Together with the amount of correction and corneal curvature gradient change, preoperative assessment of ET and ET inhomogeneity might help predict postoperative epithelial remodeling. [J Refract Surg. 2023;39(1):23-32.].

Transcriptional Profiling Provides New Insights into Organ Culture-Induced Changes in Human Donor Corneas

Corneal transplantation is one of the most common forms of tissue transplantation worldwide. Donor corneal tissue used in transplantation is provided by eye banks, which store the tissue in culture medium after procurement. To date, the effects of cell culture on human corneal tissue have not been fully elucidated. Using the 3' RNA sequencing method for massive analysis of cDNA ends (MACE), we show that cultivation of corneal tissue leads to significant changes in a variety of molecular processes in human corneal tissue that go well beyond aspects of previously known culture effects. Functionally grouped network analysis revealed nine major groups of biological processes that were affected by corneal organ culture, among them keratinization, hypoxia, and angiogenesis, with genes from each group being affected by culture time. A cell type deconvolution analysis revealed significant modulations of the corneal immune cell profile in a time dependent manner. The results suggest that current culture conditions should be further refined and that prolonged cultivation may be detrimental. Recently, we showed that MACE enables transcriptional profiling of formalin-fixed and paraffin-embedded (FFPE) conjunctival tissue with high accuracy even after more than 10 years of storage. Here we demonstrate that MACE provides comparable results for native and FFPE corneal tissue, confirming that the technology is suitable for transcriptome analysis of a wide range of archived diseased corneal samples stored in histological archives. Finally, our data underscore the feasibility of bioinformatics cell-type enrichment analysis in bulk RNA-seq data to profile immune cell composition in fixed and archived corneal tissue samples, for which RNA-seq analysis of individual cells is often not possible.

Прогнозирование рефракционного сдвига при выполнении фототерапевтической кератэктомии на примере пациента с субэпителиальной муциновой дистрофией роговицы (клинический случай)

Purpose. To present the treatment results of a patient with subepithelial mucinous corneal dystrophy by phototherapeutic keratectomy (PTK) using the excimer-laser system WaveLight EX500 (Alcon, USA) taking into account the induced myopic refractive shift. Material and methods. Patient S., 67 years old, with subepithelial mucinous corneal dystrophy and compound hyperopic astigmatism of both eyes. To determine the possibility of surgical treatment, in addition to the general ophthalmological examination, there were performed: optical coherence tomography (OCT) of the cornea to evaluate the total corneal thickness and the opacity depth; Corneal topography to evaluate total corneal refractive power and maximal anterior refractive power. FTK calculations were made basing on OCT data considering clinical refraction. The follow-up period was 3 months. Results. As a result of treatment, the corneal transparency of both eyes was restored. The ablation of the left eye corneal stroma with the standard PTK protocol to a 90-micron depth caused an increase in the patient’s refractive power by 3.87 D in spherical equivalent, which led to excessive myopic refraction. When performing PTK on the right eye, decrease of the ablation depth to 80-micron, as well as the two-stage formation of the anterior corneal profile with the formation of its wider «base» and a smaller optical zone diameter led to less refractive power increase of 2.62 D in spherical equivalent, which caused an emmetropic refraction in this case. Conclusion. The presented clinical case shows that various protocols for PTK implementation in patients with superficial corneal opacities can make it possible to not only achieve corneal transparency, but also to control the refractive shift and to define the final clinical refraction. Keywords: corneal dystrophy, phototherapeutic keratectomy (PTK), refractive surgery.

Relationship between anterior chamber angle, IOP, corneal curvature and refractive status in young Caucasian adults

AbstractPurpose: To investigate the relationship between anterior chamber angle (ACA) measurement, intraocular pressure (IOP) and refractive status of the eye in a young adult population with good ocular health.Methods: Autorefractor (AR) captured data on corneal curvature and refractive errors in group participants and enabled comparison across refractive groups, gender, and age. Refractive errors were calculated in diopters as the spherical equivalent (SE). IOP was taken by Pulsar non-contact tonometer. All patients underwent the same optometric examinations of anterior eye data on corneal curvature, anterior chamber angle and corneal thickness captured with Topcon Maestro optical coherence tomography (OCT). Slit lamp was used for Van Herick method.Results: Measurements were obtained from 118 eyes (right), of 26 males and 92 females aged 19–40 years with no ocular disease. There was no significant change Relationship between anterior chamber angle, IOP, corneal curvature and refractive status in young Caucasian adults in ocular profile across age range or by sex, apart from slightly steeper corneal profile for females (p=0.03). There was no significant correlation between IOP and ACA (p&amp;gt; 0.05), nor IOP and SE (p&amp;gt;0.05); however, when those with hyperopic SE were examined separately, there was a significant decrease in IOP with higher levels of hyperopic SE (p &amp;lt;0.05).Conclusion: This study reports mean values for ACA were 39,39°, which gives a value of the open anterior chamber angle in young Caucasian adults. There was no significant relation between IOP, ACA or SE in the sample of young adults. However, higher level of hyperopic SE has a significant decrease in IOP and should be further investigated due to small sample of hyperopic subjects.

Corneal epithelial profile in psoriasis patients with and without dry eye disease

BackgroundPsoriasis is an immune-mediated systemic inflammatory disease in which corneal affection takes various forms such as dry eye disease (DED), punctate epithelial keratitis, and sterile corneal infiltrates.PurposeThe aim of this study was to evaluate the corneal epithelial profile of psoriasis patients using anterior segment optical coherence tomography (AS-OCT).Patients and methodsThis is a cross-sectional analytic study that included 81 eyes: 39 eyes of 20 psoriasis patients and 42 eyes of 21 healthy age-matched and sex-matched controls. They were divided into three groups: psoriasis patients with dry eye disease (PDED), psoriasis patients without DED (PS), and healthy subjects (HS). AS-OCT was done to study the epithelial profile data of each eye and to correlate any finding with the disease activity evaluated by the Psoriasis Area and Severity Index score and disease extent.ResultsThe PDED patients showed significantly lower central corneal thickness (CCT), higher central epithelial thickness (CET), and thicker inferior epithelium (P=0.004, 0.002, and 0.005, respectively). A significantly thinner superior epithelium was detected in the PS group compared with the PDED and HS groups (P=0.001 and 0.010, respectively). In addition, the topographic thickness variability (SD) and minimim–maximum were significantly higher in both the PDED and PS groups compared with the HS group (P&lt;0.001). The CCT showed a significantly positive correlation with the tear breakup time (r=0.373,P=0.020), while the CET showed a significantly negative correlation with it (r=−0.331,P=0.040). The CET also had a significant positive correlation with disease duration (r=0.390,P=0.014) and disease extent (r=0.323,P=0.045).ConclusionAS-OCT has proved to be a valuable method for screening and detecting the corneal whole thickness and epithelial thickness abnormalities in psoriasis patients in the presence or absence of DED. The presence of thicker epithelium and thinner CCT were significant findings in the PDED, while in psoriasis patients without DED, superior epithelial thinning was the significant finding. A statistically significant high topographic thickness variability was detected in both groups compared with the controls.

Corneal Confocal Microscopy Features and Tear Molecular Profile in Study Participants with Discordance between Ocular Surface Disease Clinical Signs and Discomfort.

Various ocular surface conditions such as dry eye disease can present with severe discomfort and pain. However, it is clinically challenging to establish etiology and prescribe correct treatment in patients who have a lot of discordance between symptoms and signs. To understand the basis of such discordance, we stratified subjects with ocular surface pain based on concordance between the severity of signs and symptoms and evaluated corneal structural features and tear molecular factors. All subjects underwent slit lamp examination, dry eye evaluation, and ocular surface disease index (OSDI) scoring. Subjects were stratified into group 1—without symptoms or clinical signs; group 2—without symptoms but with signs; group 3—with similar severity of symptoms and signs; and group 4—with symptom severity greater than that of the signs. Laser scanning in vivo confocal microscopy (IVCM) and tear fluid analysis for soluble factors by multiplex ELISA was performed for all subjects. Patients with a higher grade of symptoms and signs showed increased corneal dendritic cell (cDC) density (p < 0.05) which was more pronounced in subjects with discordance between the symptoms and signs (group 4). A significantly higher proportion of microneuroma-like structures and cDC were observed in group 4. IL-17A levels were significantly elevated in the tears of subjects with more discomfort. Our results demonstrate that corneal IVCM and the measurement of tear film factors can help clinicians improve diagnosis and treatment choice. Stratifying patients with ocular surface discomfort on the basis of discordance between symptoms and clinical signs may help identify patients who need additional adjunctive targeted therapy to resolve their condition.

The Effect of Lens Design on Corneal Power Distribution in Orthokeratology.

This study will enhance our understanding of the effects of orthokeratology lens design on corneal profile, the results of which may be useful in developing future orthokeratology lens designs. This study aimed to evaluate the effect of lens design on corneal power distribution after orthokeratology using mathematical methods. Sixty-five subjects were enrolled in this prospective study and assigned to four groups: Euclid with 6.2-mm back optic zone diameter (aged <14 years), Euclid with 6.2-mm back optic zone diameter (aged ≥14 years), double tear reservoir lens with 5.0-mm back optic zone diameter, and double tear reservoir lens with 6.0-mm back optic zone diameter. Manifest refraction and corneal topography were checked at baseline and 1 day, 1 week, 2 weeks, and 1 month after lens wear. Relative corneal refractive power change was calculated by a polynomial function and a monomial function. The maximum relative corneal refractive power change (Ymax) and the corresponding distance from the corneal center (Xmax) were analyzed. Relative corneal refractive power change over time and between groups was compared using repeated-measures analysis of variance. Refractive reduction and central corneal flattening were seen at all follow-up visits after orthokeratology lens wear, being fastest in the 5.0-mm back optic zone diameter group (P < .001). The cornea steepened in an aspheric way toward the midperiphery and peaked at approximately 2 to 3 mm off the apex. Overall, Ymax was not different among the four groups, but Xmax was smallest in the 5.0-mm back optic zone diameter group (P < .001). At 1/2 Xmax, relative corneal refractive power change of the 5.0-mm back optic zone diameter design was significantly higher than that of the other three groups (P < .001). The power exponent of the monomial of the 5.0-mm back optic zone diameter design was greater than that of the other three groups (P < .001). An orthokeratology lens design with smaller back optic zone diameter might yield a faster myopic reduction and a smaller aspheric treatment zone.

Novel Method of Measuring Corneal Viscoelasticity Using the Corvis ST Tonometer.

Background: The process of rapid propagation of the corneal deformation in air puff tonometer depends not only on intraocular pressure, but also on the biomechanical properties of the cornea and anterior eye. One of the biomechanical properties of the cornea is viscoelasticity, which is the most visible in its high-speed deformations. It seems reasonable to link the corneal viscoelasticity parameter to two moments of the highest speed of corneal deformations, when the cornea buckles. The aim of this work is to present a method of determining the time and place of occurrence of corneal buckling, examine spatial and temporal dependencies between two corneal applanations and bucklings in the Corvis ST tonometer, and correlate these dependencies with corneal viscoelastic properties. Methods: Images of the horizontal cross section of the Corvis ST deformed cornea from the air puff tonometer Corvis ST were used. 14 volunteers participated in the study, each of them had one eye measured eight times. Mutual changes in the profile slopes of the deformed corneas were numerically determined. They describe pure corneal deformation, eliminating the influence of rotation, and displacement of the entire eyeball. For each point in the central area of the corneal profile, the maximum velocities of mutual slope changes accompanying the applanations were estimated. The times of their occurrence were adopted as buckling times. Results: The propagation of buckling along the corneal profile is presented, as well as the repeatability and mutual correlations between the buckling parameters and intraocular pressure. Based on the relationship between them, a new parameter describing corneal hysteresis: Corvis Viscoelasticity (CVE) is introduced. It is characterized by high repeatability: ICC = 0.82 (0.69–0.93 CI) and low and insignificant correlation with intraocular pressure: r = 0.25 (p-value = 0.38). Conclusion: The results show for the first time how to measure the corneal buckling and viscoelastic effects with Corvis ST. CVE is a new proposed biomechanical parameter related to the viscoelastic properties of the cornea, which has high repeatability for the examined subject. The distribution of its values is planned to be tested on different groups of patients in order to investigate its clinical applicability.

A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear.

The aim of the study was to develop an automatic segmentation approach to optical coherence tomography (OCT) images and to investigate the changes in epithelial and stromal thickness profile and radius of curvature after the use of orthokeratology (Ortho-K) contact lenses. A total of 45 right eyes from 52 participants were monitored before, and after one month of, uninterrupted overnight Ortho-K lens wear. The tomography of their right eyes was obtained using optical OCT and rotating Scheimpflug imaging (OCULUS Pentacam). A custom-built MATLAB code for automatic segmentation of corneal OCT images was created and used to assess changes in epithelial thickness, stromal thickness, corneal and stromal profiles and radii of curvature before, and after one month of, uninterrupted overnight wear of Ortho-K lenses. In the central area (0–2 mm diameter), the epithelium thinned by 12.8 ± 6.0 µm (23.8% on average, p < 0.01) after one month of Ortho-K lens wear. In the paracentral area (2–5 mm diameter), the epithelium thinned nasally and temporally (by 2.4 ± 5.9 µm, 4.5% on average, p = 0.031). The stroma thickness increased in the central area (by 4.8 ± 16.1 µm, p = 0.005). The radius of curvature of the central corneal anterior surface increased by 0.24 ± 0.26 mm (3.1%, p < 0.01) along the horizontal meridian and by 0.34 ± 0.18 mm (4.2%, p < 0.01) along the vertical meridian. There were no significant changes in the anterior and posterior stromal radius of curvature. This study introduced a new method to automatically detect the anterior corneal surface, the epithelial posterior surface and the posterior corneal surface in OCT scans. Overnight wear of Ortho-K lenses caused thinning of the central corneal epithelium. The anterior corneal surface became flattered while the anterior and posterior surfaces of the stroma did not undergo significant changes. The results are consistent with the changes reported in previous studies. The reduction in myopic refractive error caused by Ortho-K lens wear was mainly due to changes in corneal epithelium thickness profile.

Comparison of Corneal Tissue Profile of Pseudophakic and Phakic Donors.

To compare the endothelial quality of corneas obtained from pseudophakic donors with age-matched phakic controls. Retrospective analysis of 100 corneas each from pseudophakic and phakic eyes with donor age ≥60 years in both the groups was performed. The endothelial cell density, coefficient of variation, and percentage of hexagonal cells obtained by specular microscopy were compared between the two groups. The cut-off level of endothelial cell density (ECD) taken for optical keratoplasty was 2,000 cells/mm2. The male and female donors constituted 60% (n=120) and 40% (n=80), respectively. The mean age of the donors was 66.9±7.3 years in the phakic group and 69.9±7.7 years in pseudophakic group. The mean ECD in the phakic group was 2757.6±328.5 cells/mm2 and that in the pseudophakic group was 2225.5±471.9 cells/mm2 (P<0.0001). The mean coefficient of variation in the phakic group was 37.1±5.0 and that in the pseudophakic group was 38.6±11.1 (P=0.234). The mean percentage of hexagonality in the phakic group and the pseudophakic group was 52.0±6.4% and 51.2±7.2%, respectively (P=0.414). Both in univariate and multivariate linear regression analysis, age of the donor was found to be negatively associated in predicting ECD (P=0.002 and P=0.003, respectively). Sixty-nine and thirty-three corneas from the phakic and pseudophakic donor pool were used respectively. Difference in ECD between the phakic and the pseudophakic donor group was found to be statistically significant. The ECD in the pseudophakic group was found to be above the cut-off limit required for keratoplasty. Hence, pseudophakic corneas may also be used for transplantation.