Ophthalmology is a highly technical specialty, especially in the area of diagnostic equipment. While the field is innovative, the access to cutting-edge technology is limited with reference to the ...global population. A significant way to improve overall healthcare is to understand the needs and possibilities of all possible consumers when developing sophisticated and accurate medical devices. The Smartphone-based Keratograph (SBK), is an example of a new project that uses real world feedback, addresses an unmet medical need, and implements commercially available components to create a device that is affordable, portable and simplistic to operate. The long-term goal of the SBK is to collect data from users for supervised machine-learning. This machine-learning aspect will ultimately aid in the development of an artificial intelligence device to enable even earlier detection of keratoconus, especially in children and adolescents. Again, the ultimate goal of any medical device should be to improve patient care, and to make a significant improvement on vision healthcare for the global population, providing access to this technology is essential.
PURPOSE:Corneal collagen cross-linking by UVA/riboflavin (X-linking) represents a new method for the treatment of progressive keratoconus and currently is under clinical study. To avoid UVA ...irradiation damage to the corneal endothelium, the parameters for X-linking are set in a way that effective treatment occurs only in the first 300 μm of the corneal stroma. Here, X-linking not only strengthens the biomechanical properties of the cornea but also induces keratocyte apoptosis. To date, the effectiveness of treatment could be monitored only indirectly by postoperative follow-up corneal topographies or using corneal confocal microscopy. Here we describe a corneal stromal demarcation line indicating the transition zone between cross-linked anterior corneal stroma and untreated posterior corneal stroma. The demarcation line is biomicroscopically detectable in slit-lamp examination as early as 2 weeks after treatment.
METHODS:X-linking was performed in 16 cases of progressive keratoconus, and corneas were examined biomicroscopically and by means of corneal topography and pachymetry before and after treatment.
RESULTS:In 14 of 16 cases, a thin stromal demarcation line was visible at a depth of approximately 300 μm over the whole cornea after X-linking treatment.
CONCLUSION:This newly observed demarcation line may result from differences in the refractive index and/or reflection properties of untreated versus X-linked corneal stroma and represents an effective tool to biomicroscopically easily monitor the depth of effective X-linking treatment in keratoconus.
To report a patient who developed a left paracentral stromal scar due to infectious keratitis that occurred after corneal collagen cross-linking (CXL) for progressive keratoconus. The flattening ...effect of the scar led to an increase in visual acuity.
The corneal scar and flattening effect on the anterior corneal curvature were assessed by slit-lamp photography, high-resolution Scheimpflug imaging, and corneal confocal microscopy.
Three days after CXL, a corneal bacterial infection occurred in the left cornea and was treated with local antibiotics that led to a paracentral scar. Twenty-one days after CXL, a flattening of the anterior curvature of >11.00 diopters was observed. As a consequence, corrected distance visual acuity improved by five lines.
Corneal remodeling may lead to a homogenization of the anterior corneal surface and an increase in visual acuity. Remodeling may not only occur spontaneously following CXL, but also following an event that results in focal corneal scarring, such as corneal infection. In a highly irregular keratoconic cornea, the benefit of the flattening effect of a scar may outweigh the increase in aberrations and light scatter.
New corneal cross-linking (CXL) devices are capable of using higher UV-A light irradiances than used in original CXL protocols. The Bunsen-Roscoe law states that a photochemical reaction should stay ...constant if the delivered total energy is kept constant; however, little clinical data are available to support this hypothesis.
We investigated the biomechanical properties of four groups (n = 50 each) of porcine corneas. Three groups were exposed to riboflavin 0.1 % and UV-A irradiation of equal total energy (3 mW/cm(2) for 30 minutes, 9 mW/cm(2) for 10 minutes, and 18 mW/cm(2) for 5 minutes). Controls were exposed to riboflavin 0.1% without irradiation. Young's modulus of 5-mm wide corneal strips was used as an indicator of corneal stiffness.
We observed a decreased stiffening effect with increasing UV-A intensity. Young's modulus at 10% strain showed significant differences between 3 mW/cm(2) and 9 mW/cm(2) (P = 0.002), 3 mW/cm(2) and 18 mW/cm(2) (P = 0.0002), 3 mW/cm(2) and the control group (P < 0.0001), and 9 mW/cm(2) and the control group (P = 0.015). There was no difference between 18 mW/cm(2) and the control group (P = 0.064) and between 9 mW/cm(2) and 18 mW/cm(2) (P = 0.503).
The biomechanical effect of CXL decreased significantly when using high irradiance/short irradiation time settings. Intrastromal oxygen diffusion capacity and increased oxygen consumption associated with higher irradiances may be a limiting factor leading to reduced treatment efficiency. Our results regarding the efficiency of high-irradiance collagen cross-linking (CXL) raise concerns about the clinical efficiency of the new high-irradiance CXL devices already used in clinical practice without proper validation.
Abstract Since its inception in the late 1990s, corneal cross-linking has grown from an interesting concept to a primary treatment for corneal ectatic disease worldwide. Using a combination of ...ultraviolet-A light and a chromophore (vitamin B2, riboflavin), the cornea can be stiffened, usually with a single application, and progressive thinning diseases such as keratoconus arrested. Despite being in clinical use for many years, some of the underlying processes, such as the role of oxygen and the optimal treatment times, are still being worked out. More than a treatment technique, corneal cross-links represent a physiological principle of connective tissue, which may explain the enormous versatility of the method. We highlight the history of corneal cross-linking, the scientific underpinnings of current techniques, evolving clinical treatment parameters, and the use of cross-linking in combination with refractive surgery and for the treatment of infectious keratitis.
Ehlers-Danlos syndrome (EDS) is a genetic disease leading to abnormalities in mechanical properties of different tissues. Here we quantify corneal biomechanical properties in an adult classic EDS ...mouse model using two different measurement approaches suited for murine corneal mechanical characterization and relate differences to stromal structure using Second Harmonic Generation (SHG) microscopy. Quasi-static Optical Coherence Elastography (OCE) was conducted non-invasively during ambient pressure modulation by - 3 mmHg. 2D-extensometry measurements was conducted invasively consisting of a pre-conditioning cycle, a stress-relaxation test and a rupture test. In a total of 28 eyes from a Col5a1
mouse model and wild-type C57BL/6 littermates (wt), Col5a1
corneas were thinner when compared to wt, (125 ± 11 vs 148 ± 10 μm, respectively, p < 0.001). Short-term elastic modulus was significantly increased in OCE (506 ± 88 vs 430 ± 103 kPa, p = 0.023), and the same trend was observed in 2D-extensometry (30.7 ± 12.1 kPa vs 21.5 ± 5.7, p = 0.057). In contrast, in stress relaxation tests, Col5a1
corneas experienced a stronger relaxation (55% vs 50%, p = 0.01). SHG microscopy showed differences in forward and backward scattered signal indicating abnormal collagen fibrils in Col5a1
corneas. We propose that disturbed collagen fibril structure in Col5a1
corneas affects the viscoelastic properties. Results presented here support clinical findings, in which thin corneas with global ultrastructural alterations maintain a normal corneal shape.
To investigate the effect of high-fluence corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A in the management of progressive keratoconus.
Preliminary results from a prospective ...cohort study. Seven eyes from 7 patients with progressive keratoconus subjected to CXL were included. CXL was performed as a standard epithelium-off procedure, irradiating with high-fluence settings (18 mW/cm(2) for 5 minutes). Endothelial cell density (ECD), speed of postoperative epithelial healing, maximal and average keratometric readings (Kmax and Kmean, respectively) of the anterior corneal surface, and corrected distance visual acuity (CDVA) were evaluated preoperatively and at 1 and 6 months after CXL. One-way analysis of variance was applied for statistical analysis. P values less than .05 were considered significant.
ECD did not change significantly postoperatively and complete epithelial healing occurred in all eyes within 96 hours postoperatively. No morphological alterations in the corneal limbus were observed. Kmax, Kmean, and CDVA showed no significant changes at 1 and 6 months postoperatively. No complications were observed postoperatively.
Although the preliminary results are not sufficient for a valid evaluation of the biomechanical effect and the overall safety profile of high-fluence CXL in vivo, they demonstrate that CXL at 18 mW/cm(2) for 5 minutes affects neither endothelial cell density nor the speed of epithelial healing, an indirect indicator of limbal stem cell function.
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