View clinical trials related to Keratoconus.
Filter by:Primary objective of this study was to assess the intrasession, intersession and interobserver variability of the Pentacam-derived curvature and zernike coefficients in back surface of normal, keratoconic and crosslinked corneas.
The primary goal of the trial is to show that optical coherence tomography (OCT) technology can be used to effectively screen for diseases of the eye including glaucoma, macular diseases and keratoconus. Glaucoma is a disease that causes permanent vision loss and is usually accompanied by increased eye pressure. Macular diseases affect sharp, central vision. Keratoconus is a disease that affects the cornea (clear surface covering the colored part of the eye).
The purpose of this study is to evaluate the corneal pachymetric variations during and after corneal collagen cross-linking (CXL) treatment with ultraviolet-A irradiation (UVA) and hypo-osmolar riboflavin solution in thin corneas.
Primary objective of this study was to assess the intrasession, intersession and interobserver variability of the Pentacam-derived posterior corneal elevation measurements in keratoconus eyes and eyes that underwent Corneal Collagen Cross-liknking (CxL) treatment due to progressive keratoconus.
Corneal collagen crosslinking (CXL) has been proposed as an effective method of reducing progression of both keratoconus and corneal ectasia after surgery, as well as possibly decreasing the steepness of the cornea in these pathologies. During previous studies of the CXL procedure, the surface epithelial cells have been removed. Transepithelial crosslinking in which the epithelium is not removed has been proposed to offer a number of advantages over traditional crosslinking including an increased safety profile by reducing the risk for infection as no epithelial barrier will be broken, faster visual recovery and improved patient comfort in the early postoperative healing period.
The objectives of this study are to evaluate and compare the safety and efficacy of three treatment regimens for corneal collagen cross-linking performed with VibeX (riboflavin ophthalmic solution) and the KXL System in impeding the progression of, and/or reducing maximum corneal curvature.
The present study attempts to evaluate the diagnostic capacity of a) anterior segment parameters b) biomechanical metrics and c) a combination model, in differentiating Forme Fruste Keratoconus (FFK) from healthy corneas. The study adhered to the tenets of the Declaration of Helsinki and written informed consent was given by all participants. The study was conducted at the Eye Institute of Thrace (ΕΙΤ), in Alexandroupolis, Greece. EΙΤ is a Democritus University research institute focusing primarily on the conditions of the anterior segment of the eye. All participants underwent a complete clinical evaluation including review of medical history, visual acuity measurements, uncorrected and best corrected visual acuity, placido disc topography, Scheimpflug camera measurements, ORA measurements , slitlamp biomicroscopy and fundoscopic examination. All study participants were divided in two groups. The FFK group (FFKG) consisted of patients with unilateral KC. The control group (CG) was formed by refractive surgery candidates who visited EIT's outpatients service for their preoperative examination. CRF and CH parameters were obtained while the patient was sitting on a chair in front of the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) device. Upon successful fixation of the patient's eye on a red blinking target, the operator activated the device. An air puff was released by a non-contact probe, which scanned the central area of the eye and sent a signal to the ORA. In brief, the air puff causes the cornea to move inward, past applanation, and into slight concavity. After milliseconds, the air pumps shut off, the pressure decreases, and the cornea begins to return in its normal state. The system monitors the entire process and measures two pressure values, which are determined from the inward and outward applanation processes. The aforementioned measuring procedure enables the determination of CH which is related to the viscoelastic structure of the corneal tissue, and is calculated as the difference between the two pressure values at the two applanation processes, and CRF which is indicative of the overall resistance of the cornea and is calculated as a linear function of the two pressures associated with the two applanation. In order to ensure accurate results, ORA was done four times for each eye, by the same operator. Signals that differ significantly in appearance from the other signals from the same eye were deleted. Corneal Astigmatism (Cyl), Anterior Chamber Depth (ACD), Corneal Volume at 3mm (CV3), at 5mm (CV5), and overall (CV), Central Corneal Thickness (CCT), Thinnest Corneal Thickness (TCT) and TCT co-ordinates (TCTx, TCTy) were obtained using Pentacam. KISA index was calculated using Pentacam derived topography. Pentacam is based on a rotating Scheimpflug camera and monochromatic slit light source (a blue light emitted diode at 475 nm) which rotate together. After proper alignment of the patient's head, a fixation target is shown which guides the patients gaze. A real time image of the patient's eye is shown to the examiner on the computer screen, and the image is manually focused and centered. Acceptable maps had at least 10.0mm of corneal coverage. Moreover, images with extrapolated data in the central 9.0mm zone were excluded. Regarding the measuring procedure itself, patients were asked to blink and then look at the fixation device. In case of low-quality image, the procedure was repeated until the acceptable criteria were met. The data from the FFKG were compared with those from the CG in separate series analyses. Receiver operating characteristics (ROC) curves were applied to determine the overall predictive accuracy of the test for each studied parameter, as described by the area under the curve. We also used this approach to identify the cut-off points for studied parameters to maximize sensitivity and specificity in discriminating FFK cases from normal corneas. Logistic regression was used to support the cut-off point identified in the ROC curve analysis. We determined a cutoff value that will gave us the best predictive fit for our sample data. Furthermore, logistic regression analysis was performed to determine the predictive capability of a model that combined both corneal biomechanical properties and pentacam derived anterior segment parameters. Differences between groups were evaluated using the Welch modified Student's two sample t-test and Mann-Whitney U test, according to normality of distribution for each parameter. A Kolmogorov-Smirnov test of normality was applied to all variables of each group. The level of significance for each parameter was set at p<0.05. The Pearson and Spearman tests were performed in order to assess correlations between anterior segment parameters and biomechanical properties, depending on their parametric evaluation.
The objective of this twelve month dispensing study is to evaluate the clinical performance, particularly comfort and vision, of KeraSoft IC Soft Contact Lenses.
This study attempts to compare Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) in a series of keratoconic eyes before and after Corneal collagen cross-linking (CXL). Furthermore, among the objectives of the study is to reveal correlations between CH and CRF and a series of corneal indexes like the Corneal Thickness (CT), mean keratometry (Km) and corneal astigmatism (Astig). The study adhered to the tenets of the Declaration of Helsinki and written informed consent was given by all participants. The study was conducted at the Eye Institute of Thrace (ΕΙΤ), in Alexandroupolis, Greece. EΙΤ is a Democritus University research institute focusing primarily on the conditions of the anterior segment of the eye. Participants were recruited from the Outpatients Cornea service of the EIT in a consecutive if eligible basis. Fifty (50) eyes of thirty (30) patients with keratoconus were recruited for the sake of the study and formed the keratoconus group (KG). Eligible subjects for the keratoconus group had to present progressive keratoconus in consecutive corneal topographies, changes in refractive power, and deterioration of the visual acuity within a period of two years. Exclusion criteria included glaucoma, glaucoma suspicion, and intraocular pressure (IOP) lowering drugs administration. Further to glaucoma, exclusion criteria included central corneal thickness (CCT) less than 400μm, K-readings more than 60D, a history of herpetic keratitis, corneal scarring, severe eye dryness, pregnancy or nursing, current corneal infection, or underlying autoimmune disease. Fifty (50) eyes of fifty (50) non-keratoconic, age-matched, individuals who visited our outpatient service formed the control group (CG). Further to keratoconus, and a spherical equivalent error above 3D, the same exclusion criteria applied to the control group members, as well. All participants wearing contact lenses were instructed to discontinue contact lens wear at least a month before measurements. CRF and CH parameters were obtained while the patient was sitting on a chair in front of the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) device. Upon successful fixation of the patient's eye on a red blinking target, the operator activated the device. An air puff was released by a non-contact probe, which scanned the central area of the eye and sent a signal to the ORA. In brief, the air puff causes the cornea to move inward, past applanation, and into slight concavity. After milliseconds, the air pumps shut off, the pressure decreases, and the cornea begins to return in its normal state. The system monitors the entire process and measures two pressure values, which are determined from the inward and outward applanation processes. The aforementioned measuring procedure enables the determination of CH which is related to the viscoelastic structure of the corneal tissue, and is calculated as the difference between the two pressure values at the two applanation processes, and CRF which is indicative of the overall resistance of the cornea and is calculated as a linear function of the two pressures associated with the two applanation. In order to ensure accurate results, ORA was done four times for each eye, by the same operator. Signals that differ significantly in appearance from the other signals from the same eye were deleted. The same surgical procedure was applied to all keratoconus patients that included: Instillation of proparacaine hydrochloride 0.5% drops for topical anaesthesia, application of a sponge saturated with 10% alcohol to the central cornea for 30 seconds and subsequent de-epithelialization by means of a hockey knife. Following de-epithelialization, a mixture of 0.1% riboflavin in 20% Dextran solution was instilled to the cornea for 30 minutes (2 drops every 2 minutes) prior to the irradiation, until the stroma was completely penetrated and aqueous was stained yellow. The ultraviolet A (UVA) radiation source that was used is UV-XTM (IROC AG, Zurich, Switzerland). In details, an 8.0mm diameter of central cornea was irradiated for 30 minutes by UVA light with a wavelength of 370nm and an irradiance of 3mW/cm2. Instillation of riboflavin drops (1 drop every 2 minutes) was continued during irradiation, as well, in order to sustain the necessary concentration of the riboflavin. Moreover, balanced salt solution (BSS) was applied every 6 minutes to moisten the cornea. After treatment all patients were prescribed topical ofloxacin drops qid, fluorometholone qid and diclofenac nitrate qid, accompanied by frequent instillation of artificial tears. Soft therapeutic lens was applied until complete re-epithelialization of the cornea was detected. Follow up visits were performed on the 1st day, 7th day, 1st, 3rd, 6th and 12th month after the operation.
Keratoconus (KC) is a corneal disease which will in many cases ultimately require corneal transplantation to maintain vision. Early detection, which is not possible with current technology, would allow early treatment and prevent severe damage to KC corneas inadvertently operated upon for correction of vision. The investigators' aim is to combine measurements of different properties of the cornea to develop means for early detection of KC.