Intact Cornea Research Articles

Corneal absorption of glycerylphosphorylcholine

This study documents the absorption of glycerylphosphorylcholine (GPC) into corneas ex vivo. Corneas in quadruplicate were incubated in preservation medium containing 30 mM GPC, which is used as a reference marker. The GPC reference marker is used to calibrate 31P nuclear magnetic resonance (NMR) spectral chemical-shift positions for identification of phosphatic metabolites and to calculate intracorneal pH in intact tissues ex vivo. Following baseline NMR ex vivo analysis, corneas were stored in eye bank chambers in preservation medium containing 30 mM GPC at 4 °C overnight for 8 h. After returning to room temperature, NMR analysis was repeated on the same corneas in fresh GPC-free preservation medium. NMR analysis also was performed on the 30 mM GPC preservation medium alone from the eye bank chambers for detection of the GPC signal. The elevated GPC signal unexpectedly persisted in corneas incubated at 4 °C overnight even though GPC was not present in the fresh GPC-free preservation medium. In fact, the concentration of GPC in the intact cornea was many times higher than that found in the cornea endogenously. The levels of phosphatic metabolites and the energy modulus, after subtracting the spectral contribution of the 30 mM exogenous GPC, as well as the intracorneal pH remained unchanged from pre-refrigeration analyses. Corneas also retained transparency through the time-course of this study irrespective of temperature or change in temperature. The GPC signal in the NMR analysis of the preservation medium from the eye bank chambers was nearly undetectable. GPC was unexpectedly absorbed into the corneal tissue without detectable metabolic or physical toxicity. The intracorneal uptake of GPC at reduced temperatures parallels the increase in GPC that occurs naturally in muscle tissue in animals during wintering periods and the very high concentration of GPC in sperm, a cryogenically compatible cell, suggestive of a potential role for GPC in cryopreservation.

Topical Vancomycin 5% Is More Efficacious Than 2.5% and 1.25% for Reducing Viable Methicillin-Resistant Staphylococcus aureus in Infectious Keratitis.

Topical vancomycin 5% (50 mg/mL) has been used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) keratitis, but patient comfort has many clinicians using lower concentrations. We compared the efficacy of different concentrations of vancomycin in the treatment of experimental MRSA keratitis. The corneas of 45 rabbits were infected with 2000 colony-forming units (CFUs) of MRSA. Corneal epithelium was abraded in the left eyes to mimic corneal ulceration. After 4 hours, the corneal CFUs were determined at the onset of treatment. The remaining rabbits were divided into 4 treatment groups (n = 9): 1) vancomycin 5%, 2) vancomycin 2.5%, 3) vancomycin 1.25%, and 4) saline. The rabbits were treated topically in both eyes every 15 minutes for 5 hours. One hour after treatment, the rabbits were clinically examined and euthanized, corneas were removed, and CFUs were determined to analyze vancomycin penetration, treatment efficacy, and bactericidal effect. Ocular toxicity was concentration dependent from mild to moderate. For the abraded corneas, the CFUs of the vancomycin 5% group were lower than 2.5% and 1.25%, and all vancomycin groups were lower than saline. The CFUs of 2.5% were lower but similar to 1.25%. The vancomycin 5% group demonstrated a bactericidal effect and the best penetration. The CFUs of the abraded corneas treated with saline were lower than those of the intact corneas, indicating a possible antibacterial effect from the ocular surface. Vancomycin 5% was most potent for treating experimental MRSA keratitis. The clinician may need to reassess treatment regarding antibacterial efficacy and patient comfort.

Optical Coherence Tomography Assessment of the Cornea During Corneal Swelling: Should the Term "Descemet Membrane Folds" Be Reconsidered?

Previous work has suggested that Descemet membrane (DM) folds arise in response to corneal swelling. However, their origin has not been closely explored. In this study, we used optical coherence tomography to evaluate whether DM folds arise secondary to folds in the middle stroma. Serial optical coherence tomography images of donor cornea pairs in deionized water were taken for each of the following corneal manipulations: 1) untreated, 2) DM and the endothelium removed, 3) excised in the region of the deep middle/posterior stroma, and 4) excised in the middle stroma. For intact corneas, increasing duration in deionized water was marked by a progressive increase in corneal thickness and number of folds along the posterior surface. With DM and the endothelium removed, a similar phenomenon was observed. In the third set of corneas, the plane of resection created a structural separation in the region of the deep middle/posterior stroma. Folds were seen originating anterior to the resection plane. For corneas with the posterior and part of the middle stroma removed, the typical folds on the posterior surface as seen in the previous conditions were not observed. Instead, less numerous and smaller irregularities of the posterior surface of the resection plane were present. Folds in DM associated with corneal edema originate in the middle and posterior stroma and are secondarily transmitted into DM. On the basis of the stromal origin of these anatomic changes, "stromal folds" should be considered a more accurate term to replace "Descemet membrane folds."

Blocking connexin 43 accelerates corneal healing and improves tissue remodeling during the healing of diabetic rat corneas: A histological and immunohistochemical study

Connexin 43 (Cx43) is a potential target for accelerating wound healing. This study aimed at evaluating the therapeutic efficiency of topical application of Gap27, a Cx43 mimetic peptide, on corneal tissue reorganization during wound healing in streptozocin-induced Diabetes in albino rats and its effect on the infiltration of inflammatory cells. Fifty adult male albino Wistar rats were divided equally into two groups: non-diabetic and diabetic. Twenty rats from each group were subjected to corneal injury: 10 untreated and 10 treated with Gap27. The remaining five rats from each group served as negative controls (intact corneas). All rats were sacrificed 3 days after injury. Histological studies were performed to assess signs of cell degeneration, the infiltration of inflammatory cells. Histomorphometric studies were performed to quantify the expression of Cx43. Gap27 promoted corneal wound healing in non-diabetic and diabetic rats. It reduced mononuclear cell infiltration and improved corneal tissue remodeling. However, minor structural changes were still seen in diabetic corneas after treatment with Gap27. Blocking Cx43 was a valuable tool to restore corneal tissue structure, reduce the infiltration of inflammatory cells in non-diabetic and diabetic rats.

Corneal Oxidative Damage in Keratoconus Cells due to Decreased Oxidant Elimination from Modified Expression Levels of SOD Enzymes, PRDX6, SCARA3, CPSF3, and FOXM1.

Purpose:To compare the levels of gene expression for enzymes involved in production and elimination of reactive oxygen/nitrogen species (ROS/RNS) in normal human corneal cells (NL cells) with those in human corneal cells with keratoconus (KC cells) in vitro.Methods:Primary NL and KC stromal fibroblast cultures were incubated with apocynin (an inhibitor of NADPH oxidase) or N-nitro-L-arginine (N-LLA; an inhibitor of nitric oxide synthase). ROS/RNS levels were measured using an H2 DCFDA fluorescent assay. The RT2 Profiler™ PCR Array for Oxidative Stress and Antioxidant Defense was used for initial screening of the NL and KC cultures. Transcription levels for genes related to production or elimination of ROS/RNS were analyzed using quantitative PCR. Immunohistochemistry was performed on 10 intact human corneas using antibodies against SCARA3 and CPSF3.Results:Array screening of 84 antioxidant-related genes identified 12 genes that were differentially expressed between NL and KC cultures. Compared with NL cells, quantitative PCR showed that KC cells had decreased expression of antioxidant genes SCARA3 isoform 2 (0.59-fold, P = 0.02) and FOXM1 isoform 1 (0.61-fold, P = 0.03). KC cells also had downregulation of the antioxidant genes SOD1 (0.4-fold, P = 0.0001) and SOD3 (0.37-fold, P = 0.02) but increased expression of SOD2 (3.3-fold, P < 0.0001), PRDX6 (1.47-fold, P = 0.01), and CPSF3 (1.44-fold, P = 0.02).Conclusion:The difference in expression of antioxidant enzymes between KC and NL suggests that the oxidative stress imbalances found in KC are caused by defects in ROS/RNS removal rather than increased ROS/RNS production.

Corneal Topographic and Biomechanical Changes after Small Incision Lenticule Extraction (SMILE) In Myopic Eyes

Background: Small incision lenticule extraction (SMILE) offers laser vision correction by using a less invasive technique that creates a lenticule inside the intact cornea. This procedure limits the biomechanical strength of the cornea and reduces flap-induced complications. Purpose: To evaluate outcome, post-operative corneal topographic and biomechanical changes in myopic patients who had undergone SMILE. Methods: The study included 40 eyes of 20 patients treated by SMILE for myopia and myopic astigmatism. Data included uncorrected and best corrected visual acuity (UCVA and BCVA), spherical equivalent (SE), central pachymetry Pentacam (oculus) topography to evaluate changes in keratometric readings (K1 and K2) and asphericity (Q). Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with ocular response analyzer. Patients were treated and followed for 12 months. Results: SMILE procedure for the correction of myopia and myopic astigmatism was performed on 40 eyes of 20 patients. There was highly significant difference between pre and postoperative keratometric regarding K1 and K2 was change from 42.9 ± 0.82 and 39.8 ± 1.14 to 43.9 ± 1.21 and 40.5 ± 1.18 respectively (P value <0.001).Corneal resistance factor and hysteresis were also change from 11.55 ± 1.29 mm Hg and 11.68±1.40 mm Hg to 9.47 ± 1.29 mm Hg and 8.49 ± 1.54 mm Hg, respectively) (P < .0001). At the end of follow up UDVA was 20/20 or better in 86 % of eyes. Conclusions: Biomechanical stability with small-incision lenticule extraction has been demonstrated with establishment of myopic and astigmatic corrective ability, so SMILE represents a safe and effective refractive option. The incidence of intraoperative and or postoperative complications remains minimal. Although visual recovery may be slower than LASIK in most cases.

Corneal Topographic and Biomechanical Changes after Small Incision Lenticule Extraction (SMILE) In Myopic Eyes

Background: Small incision lenticule extraction (SMILE) offers laser vision correction by using a less invasive technique that creates a lenticule inside the intact cornea. This procedure limits the biomechanical strength of the cornea and reduces flap-induced complications. Purpose: To evaluate outcome, post-operative corneal topographic and biomechanical changes in myopic patients who had undergone SMILE. Methods: The study included 40 eyes of 20 patients treated by SMILE for myopia and myopic astigmatism. Data included uncorrected and best corrected visual acuity (UCVA and BCVA), spherical equivalent (SE), central pachymetry Pentacam (oculus) topography to evaluate changes in keratometric readings (K1 and K2) and asphericity (Q). Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with ocular response analyzer. Patients were treated and followed for 12 months. Results: SMILE procedure for the correction of myopia and myopic astigmatism was performed on 40 eyes of 20 patients. There was highly significant difference between pre and postoperative keratometric regarding K1 and K2 was change from 42.9 ± 0.82 and 39.8 ± 1.14 to 43.9 ± 1.21 and 40.5 ± 1.18 respectively (P value <0.001).Corneal resistance factor and hysteresis were also change from 11.55 ± 1.29 mm Hg and 11.68±1.40 mm Hg to 9.47 ± 1.29 mm Hg and 8.49 ± 1.54 mm Hg, respectively) (P < .0001). At the end of follow up UDVA was 20/20 or better in 86 % of eyes. Conclusions: Biomechanical stability with small-incision lenticule extraction has been demonstrated with establishment of myopic and astigmatic corrective ability, so SMILE represents a safe and effective refractive option. The incidence of intraoperative and or postoperative complications remains minimal. Although visual recovery may be slower than LASIK in most cases.

The facilitation of corneal permeability of cyclosporine A loaded on chitosan-graft-cyclodextrin copolymers vector

Objective To investigate the corneal permeability of cyclosprin A (CsA) loaded on polymeric vector after topical application. Methods The grafted copolymer chitosan-graft-cyclodextrin (CS-g-CD) was synthesized, and the physicochemical structures of the polymer were investigated using nuclear magnetic resonance spectroscopy (NMR) and fourier transform infrared spectroscopy (FT-IR). A novel CsA eye drop was prepared using the grafted copolymer as carrier material.The physicochemical properties of eye drop, including drug-loading content, osmotic pressure and viscosity were investigated by high performance liquid chromatography-mass spectrometry (HPLC-MS), osmotic pressure gauge and viscometer, respectively.New Zealand albino rabbits were randomly divided into intact cornea CsA group, epithelium debrided CsA group and epithelium debrided control group.The corneal epithelia of the left eyes was debrided in the cornea epithelium debrided group.Cornea irritation test was performed on New Zealand albino rabbits.The aqueous humor was taken and the corneas were collected at 0.5 hour and 1 hour after instilled.The concentration of CsA was measured by HPLC-MS.Cy5 labeled vector loaded with Coumarin 6 served as model copolymers system, the penetration capabilities of the double fluorescent labeling copolymers system were monitored in vivo using two-photon scanning fluorescence microscopy on murine corneas after topical application.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission. Results The polymer of CS-g-CD was successfully synthesized and confirmed using NMR and FT-IR.The drug loading of CsA in eye drop solution was 0.06 %; the osmotic pressure was 305 mOsmol/kg and the viscosity was 36.5 cP.The CsA drug delivery system had a reversible temperature-sensitive drug release behavior and had no obvious irritation on the eyes of New Zealand rabbits.One hour after treatment, the concentration of CsA in the cornea and aqueous humor of epithelium debrided CsA group was (5.88±1.46)μg/g and (149.19±3.93)ng/ml, respectively, which was significantly higher than (3.98±0.95)μg/g and (30.25±11.43)ng/ml in epithelium debrided control group (both at P<0.05); the concentration of CsA in the aqueous humor of intact cornea CsA group was (7.23±1.31)ng/ml, which was significantly lower than that in epithelium debrided CsA group (P<0.05). Polymer vectors were mainly retained in the corneal epithelium, and coumarin 6 gradually diffused into the deep corneal stroma with time. Conclusions The grafted copolymer can load CsA, and the eye drop can effectively overcome the corneal barrier and increase the corneal permeability of CsA. Key words: Cyclosporine A; Immunosuppressive agents; Corneal barrier; Fluorescent double labeling; Corneal tissue distribution

Прочностные характеристики роговицы кролика после интрастромальной имплантации различных имплантов с применением фемтосекундного лазера

Purpose. Comparative experimental study of the effect of the implantation of various intrastromal implants using a femtosecond laser (FSL)on the strength properties of the rabbit cornea. Material and methods . The experimental work was performed on 24 corneas of isolated eyes of 12 rabbits enucleated 1 month after the slaughter. All eyes were divided into 4 groups, depending on the method of operation. Formation of intra-stromal pockets (IP) and tunnels (IT) was performed using the FSL Femto Visum. The eyes of rabbits with intact corneas were included into the first control group. In the group 2, the intrastromal segment 350° was implanted into the IT. In the group 3,the MyoRing was implanted into the IP. In the group 4, the intrastromal closing ring with a «lock» was implanted into the IT. Results. After the implantation of intrastromal implants in comparison with the control group it was noted that the strength of the examined cornea of rabbits was increased to break. The greatest increase in the strength properties of the rabbit cornea was observed after the implantation of the intrastromal closing ring with a «lock» in comparison with the implantation of the intrastromal segment of 350° and the MyoRing. Conclusions. Implantation of intrastromal rings and segments leads to an increase in the strength properties of the cornea. Implantation of an intrastromal closing ring with a «lock» leads to the greatest increase in the strength properties of the cornea compared with the implantation of the intrastromal segment of 350° and the MyoRing.

Formulation Development, Optimization, and In Vitro–In Vivo Characterization of Natamycin-Loaded PEGylated Nano-Lipid Carriers for Ocular Applications

The present study aimed at formulating and optimizing natamycin (NT)-loaded polyethylene glycosylated nano-lipid carriers (NT-PEG-NLCs) using Box-Behnken design and investigating their potential in ocular applications. Response surface methodology computations and plots for optimization were performed using Design-Expert® software to obtain optimum values for response variables based on the criteria of desirability. Optimized NT-PEG-NLCs had predicted values for the dependent variables which are not significantly different from the experimental values. NT-PEG-NLCs were characterized for their physicochemical parameters; NT's rate of permeation and flux across rabbit cornea was evaluated, in vitro, and ocular tissue distribution was assessed in rabbits, in vivo. NT-PEG-NLCs were found to have optimum particle size (<300 nm), narrow polydispersity index, and high NT entrapment and NT content. In vitro transcorneal permeability and flux of NT from NT-PEG-NLCs was significantly higher than that of Natacyn®. NT-PEG-NLC (0.3%) showed improved delivery of NT across the intact cornea and provided concentrations statistically similar to the marketed suspension (5%) in inner ocular tissues, in vivo, indicating that it could be a potential alternative to the conventional suspension during the course of fungal keratitis therapy.

THE PARTIAL TRANSPLANTATION OF DESCEMET’S MEMBRANE WITH ENDOTHELIUM (½ AND ¼ DMEK)

The lamellar keratoplasty is the first operation of choice under selective pathology of cornea. In view of satisfactory results of endothelium surgery similar operations are implemented at more earlier stages that increases need in donor tissue. The life-span of population increases hence number of patients in need of cornea transplantation also increases and number of intact cadaver corneas decreases because of stable increasing of number of surgical interventions at the frontal section of eye. The purpose of study is to analyze operations of partial transplantation of Descemet's membrane with endothelium (½ DMEK and ¼ DMEK). Material and methods. The analysis was applied to the results of 10 operations ½ DMEK (semi-DMEK, hemi-DMEK) and 10 operations ¼ DMEK, implemented at eyes of 20 patients with primary endothelium dystrophy. The average age of patients made up to 64,9±10,4 years. The average visual acuity prior to implementation of partial DMEK amounted to 0,14 ± 0,08, average central thickness of cornea, according data of optical coherent tomography, made up to 669 ± 91 мкм. Results. In 16 out of 20 cases of partial DMEK, restoration of transparency of cornea, resorption of edema and increasing of visual acuity was achieved. In other 4 cases, during one week after partial DMEK, a subtotal DMEK was implemented. In 16 cases, average visual acuity increased up to 0,8 ± 0,3 three months later after operation. Conclusion. The techniques of partial transplantation of Descemet's membrane with endothelium (¼ DMEK и ½ DMEK) are efficient for treatment of primary endothelium pathology of cornea and permit to apply donor's material as much as possible rationally.

Strength properties of rabbit cornea after femtosecond laser keratoplasty with and without different intracorneal implants

to conduct a comparative experimental study of the effect of the use of intracorneal implants during femtosecond laser-assisted intrastromal pocket (IP) and intrastromal tunnel (IT) formation on the strength properties of the cornea. The experimental study was performed on 24 corneas of 12 rabbit eyes enucleated 1 month after slaughtering. All eyes were divided into 6 groups according to the method of operation. IP and IT were created with IntraLase FS 60 kHz femtolaser. Group 1 (control group) consisted of rabbit eyes with intact corneas. In group 2 corneas, intrastromal tunnels were formed, in group 3 - intrastromal pockets, and in group 4 - intrastromal tunnels with 2 intracorneal segments (ICS). In groups 5 and 6, intrastromal pockets, each supplemented with an intrastromal ring, were created at the depth of 62-72% and 80% of pachymetry readings from the 5.0-mm optical zone, respectively. Higher voltage had to be applied to stretch the samples from group 2 as compared to those from groups 3 and 6. Distribution of the Young's modulus of the test corneas agreed with voltage distribution in the study groups. IP was associated with greater reduction in corneal biomechanical stability as compared with IT. Ring implantation into an IP yielded a more pronounced increase in the strength properties of the cornea than ICS implantation into an IT. The result was also more favorable at greater depths of intrastromal ring implantation.

Inhibitory Effect of Amitriptyline on the Impulse Activity of Cold Thermoreceptor Terminals of Intact and Tear-Deficient Guinea Pig Corneas.

Chronic dryness of the ocular surface evokes sensitization of corneal cold-sensitive neurons through an increase of sodium currents and a decrease of potassium currents, leading to the unpleasant dryness and pain sensations typical of dry eye disease. Here, we explored the effects of amitriptyline, a voltage-gated Na+ channel blocker used for the treatment of depression and chronic pain, on nerve terminal impulse (NTI) activity of cold-sensitive nerve terminals recorded in intact and tear-deficient guinea pig corneas. Main lachrymal gland was surgically removed in anesthetized guinea pigs to induce chronic tear deficiency. Four to 6 weeks afterward, animals were sacrificed and both corneas placed in a perfusion chamber superfused at 34°C. Thermal stimuli were induced by changing the solution temperature from 34°C to 20°C (cooling ramp) and from 34°C to 50°C (heating ramp). Spontaneous and stimulus-evoked NTIs of cold-sensitive nerve terminals were recorded before, during, and after perfusion with solutions containing amitriptyline at different concentrations (3-30 μM). Perfusion with amitriptyline inhibited irreversibly and in a concentration-dependent manner the spontaneous NTI activity of cold thermoreceptors of intact corneas. This effect was less evident in tear-deficient corneas. In addition, amitriptyline (10 μM) attenuated the maximal response to cooling ramps without changing cold threshold in intact but not in tear-deficient corneas. Only cold thermoreceptors with low cooling threshold values were sensitive to amitriptyline. Amitriptyline effectively reduces the activity of cold thermoreceptors, although its efficacy is different in intact and tear-deficient corneas, which might be due to the changes induced by ocular dryness in the expression of the various voltage-gated Na+ channels responsible of the action potential generation and propagation.

Transport mechanism of chitosan-N-acetylcysteine, chitosan oligosaccharides or carboxymethyl chitosan decorated coumarin-6 loaded nanostructured lipid carriers across the rabbit ocular

To facilitate the hydrophobic drugs modeled by coumarin-6 (Cou-6) acrossing the cornea to the anterior chamber of the rabbit eye, chitosan (CS) derivatives including chitosan-N-acetyl-l-cysteine (CS-NAC), chitosan oligosaccharides (COS) and carboxymethyl chitosan (CMCS) modified nanostructured lipid carriers (NLCs) were designed and characterized. We found that, with similar size distribution and positivecharges, different CS derivatives based on NLCs led to distinctive delivery performance. In vivo precorneal retention study on rabbits revealed that these CS derivatives coating exhibited a stronger resistant effect than Cou-6 eye drops and Cou-6-NLC (P<0.05), moreover, the AUC(0−∞), Cmax and MRT(0−∞) of them followed the sequence of CMCS-Cou-6-NLC<COS-Cou-6-NLC<CS-NAC-Cou-6-NLC. Confocal laser fluorescence microscopy (CLSM) for in vitro corneal penetration study showed that COS-, and CS-NAC-coated NLCs penetrated through the whole corneal epithelium barrier (about 40μm), while CMCS failed to significantly enhance the intraocular drug penetration as expected, displayed a negligible fluorescence at 30μm deep. In addition, penetration through the intact cornea was achieved and the penetration levels through the ocular tissues were increased thoroughly for the COS and CS-NAC coating ones compared with CMCS-NLC (P<0.05), and successfully reduced the conjunctival-to-corneal permeability ratio (ratio(C-S/C)) thus resulted in a higher bioavailability, which was confirmed by ex vivo fluorescence imaging on ocular tissues. In summary, CS-NAC-NLC and COS-NLC are promising ocular drug delivery systems to achieve prolonged precorneal retention, higher corneal permeability and enhanced ocular bioavailability. And comparatively speaking, CS-NAC-NLC possesses the highest potential for ocular drug delivery.

Esthesiometric evaluation of corneal analgesia after topical application of 1% morphine sulfate in normal horses.

To evaluate whether topical ocular application of 1% morphine sulfate would change corneal sensitivity and to identify the duration of action. Eight healthy adult horses. Corneal touch threshold (CTT) was measured in the center of one randomly selected eye of each horse by Cochet-Bonnet esthesiometer (Luneau Cochet-Bonnet Esthesiometer; Western Ophthalmics, Lynnwood, WA, USA). Immediately following baseline CTT measurement, 0.3ml of 1.0% preservative-free morphine sulfate (Morphine Sulfate 25mg/ml Preservative-free; Hospira, Lake Forest, IL, USA) (3mg) was applied to the tested eye. The same volume of artificial tear (LiquiTears; Major Pharmacauticals, Livonia, MI, USA) solution was then applied to the control eye following acquisition of baseline CTT. Corneal touch threshold was then subsequently measured at 1min after medication application, followed by every 5min until 60min post administration. If the corneal touch threshold had not returned to baseline by 60min, measurements were continued at 15-min intervals until corneal sensitivity returned to baseline CTT measurement up to 180min post administration if needed. The control eye was treated identically and measurements on the control eye stopped when the corresponding treated eye returned to baseline. Mean baseline CTT of both eyes was 21.8mm with an identical range of 15-30mm. Mean corneal touch threshold was not statistically different between morphine-treated and control eyes (P=0.22). There was a large degree of inter- and intrasubject variation in the CTT measurements obtained. All but three horses were considered to be at baseline values by 60min. Topical ophthalmic 1% morphine sulfate did not have a clinically significant analgesic effect on the corneal touch threshold of intact healthy equine corneas.

Effects of TRPM8 and TRPV1 agonists on the neural activity of corneal cold thermoreceptors in tear‐deficient guinea pigs

PurposeTo characterize the effects of menthol and capsaicin on the activity of corneal cold thermoreceptors in tear‐deficient guinea pigsMethodsThe main lachrymal gland was surgically removed in anesthetized animals. Four weeks later, cold‐sensitive nerve terminal impulse (NTI) activity was recorded from the superfused cornea. The spontaneous and stimulus‐evoked NTI activity was analysed. For thermal stimulation, temperature of perfusion solution was changed from 34°C (basal) down to 20°C (cooling ramp) or up to 50°C (heating ramp). TRP agonists (50–200 μM menthol, 1–10 μM capsaicin) were also added to the perfusion solution. The characteristics of the spontaneous and stimulus‐evoked NTI activity recorded in tear‐deficient and intact corneas before and during perfusion with TRP channel agonists were compared.ResultsRemoval of the lachrymal gland caused sustained reduction of basal and reflex tearing. NTI activity was significantly higher in cold thermoreceptors from tear‐deficient corneas compared with naïve corneas. Response to cooling ramps was also increased. Menthol increased ongoing and stimulus‐evoked activity of all cold thermoreceptors in both intact and tear deficient corneas. Menthol at high concentrations first excited and then inactivated cold thermoreceptors. Only 10% of thermoreceptors were activated by capsaicin.ConclusionsChronic tear deficiency alters the activity of corneal sensory nerve fibers, leading to the development of increased spontaneous activity and abnormal responsiveness to natural stimulation. These changes are particularly prominent in cold thermoreceptor fibers, whose injury‐evoked neuropathic firing seems to be due to altered expression of Na+ and K+ channels involved in impulse generation without changes in the activity of TRP channels involved in sensory transduction.

The rationale application of donor material: original ten years experience, possible ways of development and literature data

Lately, layer-wise keratoplasty became the first operation of choice in case of pathology of cornea. In view of satisfying results of endothelial surgery similar operations are implemented at earlier stages that increases need in donor tissue. With increasing of life span of population, also increases number of patients in need of transplantation of cornea. The number of intact cadaver cornea decreases because of stable increase of surgical interventions on front segment of eye. The present article presents original ten years experience concerning optimization of application of donor tissue and indicate on possibilities of further increasing of number of applied keratoplasties. From 2009 to 2015 in the Helmholtz Moscow research institute of eyes diseases 652 transplantations of cornea were implemented in various modifications: straight-through keratoplasty, transplantation of Descemet's membrane with endothelium (DMEK), deep front layer-wise keratoplasty, endokeratoplasty (DSEK) with various modes of transplant formation and 23 frontal layer-wise keratoplasties. In transplantation were also used eyes of donors with radial keratotomy, after laser keratomileusis and with artificial intra-ocular lens. To implement 652 operations 528 cadaver eyes with average age 41 ± 32,5 years (varying from 21 to 87 years) were required. The number of transplantations increased approximately on 50% at potential up to 75%. The lamellar surgery permits using corneal donor tissue with altered frontal surface and to increase number of transplantations of cornea. The renunciation of application of corneal donor tissue with altered frontal surface is inexpedient.

Visualization of precut DSAEK and pre-stripped DMEK donor corneas by intraoperative optical coherence tomography using the RESCAN 700.

BackgroundTo report the feasibility of intraoperative spectral domain optical coherence tomography (OCT) using the RESCAN 700 for the visualization and evaluation of precut Descemet’s stripping automated endothelial keratoplasty (DSAEK) and prestripped Descemet’s membrane endothelial keratoplasty (DMEK) donor tissue.MethodsPrecut DSAEK (n = 11), prestripped DMEK (n = 4) preserved in a viewing chamber were examined by intraoperative OCT. Wholly intact donor corneas for penetrating keratoplasty (PK) (n = 8) were also examined as controls. The obtained images were analyzed qualitatively for characteristics of each type of donor.ResultsFor each type of donor, characteristic images were consistently obtained by intraoperative OCT in both the front and back views through the viewing chamber. In wholly intact donors for PK, appearance of normal corneal curvature and stromal texture with high reflectivity of epithelium and endothelium cell layers were clearly visualized. In precut DSAEK donors, precut lines were characteristically visualized in addition to the intact donor cornea images. In prestripped DMEK donors, identical OCT images to the intact donor cornea were noted when observed from the anterior surface. However, peripheral partial detachments of Descemet’s membrane were characteristically observed in all prestripped DMEK donors when viewed from the back of the viewing chamber.ConclusionRapid visualization and rough evaluation of donor tissues for PK, precut DSAEK and prestripped DMEK donor corneas by intraoperative OCT was consistently possible through the viewing chamber. Therefore, this device may be used as an alternative of AS-OCT when the eyebank does not have their own AS-OCT. Although the peripheral detachment in DMEK donors are quite common and clinically non-problematic in DMEK donor quality and subsequent DMEK surgeries, it may be useful to distinguish between wholly intact PK donors and prestripped DMEK donors, enabling to prevent mix-ups of donors, especially when several different types of keratoplasties are scheduled in a same day in one operating theater.

In Vitro Corneal Tomography of Donor Cornea Using Anterior Segment OCT.

The aim of this study was to establish a tomographic screening method for revealing potential pathologies in corneal donors before keratoplasty so they may be excluded as candidates for corneal transplantation. Donor corneal tomographies were measured in a viewing chamber filled with preservation medium and with the use of a clinical optical coherence tomography (OCT) device. Custom-written software was developed to extract corneal surfaces from the raw data, which were analyzed in the central and peripheral regions. An adaptive nonlinear edge-enhancement algorithm was used to observe scars within the corneal volume. The thickness distribution map was analyzed to detect keratoconus and corneas with extreme topographic irregularities. Measurements were repeated 5 times to assess reproducibility. Eight corneas were investigated: 6 randomly selected intact donors, unsuitable for implantation because of low endothelial cell densities, and 2 keratoconus corneas, excised from patients during corneal transplantation. A major thickness abnormality was detected in one of the intact donor corneas, so it was excluded from further analysis. The keratoconus corneas were clearly evident in optical coherence tomography cross-sectional images, and similarly, they could easily be identified by analyzing the thickness map. Overall, the measurements were reliable and had a Cronbach's alpha coefficient greater than 0.8. Donor corneal examination using sterile viewing chambers was found to be suitable as a pre-keratoplasty advanced screening routine. A proof of concept was demonstrated, which could identify both irregular corneas and those affected by keratoconus.

ГІСТОЛОГІЧНЕ І ЕЛЕКТРОННО-МІКРОСКОПІЧНЕ ДОСЛІДЖЕННЯ КЕРАТОКСЕНОІМПЛАНТАТА ПРИ РІЗНИХ ВИДАХ КОНСЕРВАЦІЇ

&lt;p&gt;РЕЗЮМЕ. Досліджено структурну організацію компонентів інтактної рогівки свині та морфологічні структури&lt;br /&gt;кріоконсервованої рогівки без кріопротектора ікріоконсервованої рогівки з кріопротектором. Встановлено, що&lt;br /&gt;кріоконсервування ксенорогівки після проведення попередньої обробки в гліцерин-жовтковій суміші забезпечує&lt;br /&gt;високу збереженість всіх її структурних компонентів.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;КЛЮЧОВІ СЛОВА: рогівка, структура, кріоконсервування.&lt;/p&gt;