Corneal Contact Research Articles

Comparison of central corneal thickness in dogs measured by ultrasound pachymetry and ultrasound biomicroscopy

Ultrasound pachymetry (UP) is currently the most common technique used to evaluate central corneal thickness (CCT). New devices which allow assessment of CCT without corneal contact have been compared, but there are discrepancies among instruments. The aim of this study was to compare CCT measurements obtained by UP and ultrasound biomicroscopy (UBM) in 28 eyes of 14 healthy Beagles dogs. Mean CCT±standard deviation (SD) were 552±63μm for UP and 551±55μm for UBM. UBM showed both a fixed and proportional bias when compared to ultrasound pachymetry, but this was not considered to be clinically important. Measured CCT did not differ between UP and UBM (P=0.796). The intra-class correlation coefficient indicated a strong agreement between methods (0.990). The CCT measurements between left (548±61μm) and right (555±59μm) eyes did not differ (P=0.760). Male dogs had higher CCT measurements than female dogs (P=0.038).

Molecular and morphological characterization of Acanthamoeba isolated from corneal scrapes and contact lens wearers in Argentina

In this study, we describe the frequency of Acanthamoeba keratitis (AK) in patients that assisted in the Ophthalmology Department and determine the species/genotypes of free living amoebas (FLA) isolates. FLA from Corneal scrapes (CS) and contact lens (CL) wearers were studied by morphological and molecular characterization. A database was constructed with sociodemographic, clinical findings and history of use of CL variables. During January 2000 and September 2016 patients with corneal pathology admitted to the Ophthalmology Service of the University Hospital in Córdoba city, Argentina were included in the study. FLA were detected in 1.5% (11/739) and in 17% (11/65) of CS and CL analyzed respectively. FLA isolates from CL users evidenced an 80.9% of inappropriate lens maintenance, 4.8% (1/21) were not CL users that have been in contact with waters in outdoor environment and 14,3% (3/21) with no data about CL users. Acanthamoeba was confirmed in 100% and 82% of CS and LC respectively. The most frequent symptom associated with AK was red eye and photophobia. FLA from CS belonged to group II but 82% (9/11) and 18% (2/11) from CL belonged to group II and III respectively. T4 genotype and A. polyphaga species were detected in 100% of Acanthamoeba isolates. Poor CL hygiene practices, highlights the need for improved education about the severity of AK and consequences of improper CL hygiene. Genotype T4 detected in 100% of both CS and CL samples, consistently with previous findings indicating that this genotype is by far the most prevalent isolated from ocular infection.

Application effects of individualized nursing in excimer laser for phototherapeutic keratectomy

Objective To explore application effects of individualized nursing in excimer laser phototherapeutic keratectomy (PTK) . Methods Randomly 24 cases of bullous keratopathy underwent PTK surgery were divided as the control group and the observation group, and patients of control group received routine care while patients of observation group implemented personalized care. The curative effect, pain score, anxiety score and satisfaction degree of the two groups were observed. Results In observation group, patients were better than the control group in the degree of anxiety, postoperative pain and satisfaction (P<0.05) . Control group had two cases lost corneal contact lens. There were no postoperative complications in the two groups. Conclusions The security of PTK is high to treat bullous keratopathy, and personalized nursing can enhance the awareness of cooperation and psychological ability of patients during operation, and improve patient's satisfaction. Key words: Laser, excimer; Keratectomy; Bullous keratopathy; Individualized nursing

Fundus imaging in newborn children with wide-field scanning laser ophthalmoscope.

Current fundus imaging in newborn babies requires mydriatics, eye specula and corneal contact. We propose that a scanning laser ophthalmoscope (SLO) allows ultra wide-field imaging with reduced stress for the child. This prospective observational single centre study was conducted in Landspítali, University Hospital, Reykjavik, Iceland. In this study, a noncontact wide-field SLO (Optomap 200Tx) was used to image the retina in healthy full-term newborns without the use of mydriatics or eye specula. The child was held by one of the parents, while one of the researchers supported the child's head in front of the SLO camera for alignment and opened the eye with either a finger or a cotton tip. Fifty-nine participants were recruited (34 females). The mean age was 16days, and the mean gestational age was 40±1weeks at the time of imaging. Ultra-wide-field (200°) images were obtained of 44 participants. Twenty-seven participants (61%) had at least one ultra wide-field image with the optic disc and vessel segments in all quadrants of the fundus visible and in focus. No retinal pathology was found in the participants with the exception of one participant with small retinal haemorrhages. Scanning laser ophthalmoscope (SLO) ultra-wide-field fundus imaging is feasible in healthy full-term newborns without corneal contact, eye speculum or mydriatics. This approach could be an improvement for retinal imaging in newborn infants. Eye movement of the infant, whether asleep or awake, influenced which part of the fundus was captured, but focus and image quality were generally good.

Preparation and Evaluation of Chloramphenicol as Thermosensitive Ocular in- situ Gel

The purpose of this study was to develop poloxamer-based in-situ gel of chloramphenicol aiming to increase bioavailability and prolong corneal contact time, controlling drug release, and enhancing ocular bioavailability. The in-situ gel was prepared using different concentrations of poloxamer 407 combined with hydroxypropyl methyl cellulose (HPMC) or carbapol 940 to achieve gelation temperature about physiological temperature and improve rheological behavior and gelling properties of poloxamer gel. The prepared formulations were evaluated for their appearance, pH, and sol-gel transition temperature. The formulations F2, F3, and F5 have a gelation temperature within the accepted range 35-370C and were evaluated for their isotonicity, rheological studies, ocular irritation test, sterility and release studies. The selected formulations (F2,F3, and F5) isotonic, pseudoplastic, non irritant, pass sterility test, and the in vitro release demonstrated a diffusion-erosion controlled release of chloramphenicol over a period of 4 hr., 6 hr., and 6 hr. respectively.&#x0D; Key words: Chloramphenicol, in-situ gel, ocular dosage form, poloxamer.

Treatment of large irregular rabbit corneal penetrating injury with fibrin glue

Background Suture stitching is currently the standard treatment for corneal penetrating injuries.The shortcomings of suture stitching have led to the exploration of non-sutured surgical methods.Tissue adhesive is a promising non-suture replacement procedure. Objective This study was to observe the effect of fibrin glue on large irregular rabbit corneal penetrating injury. Methods Eighteen pure white healthy rabbits were randomly divided into suture group and adhesive group.A total length of 6-mm non-self-sealing corneal penetrating injury in non-pupillary-area of the right eye formed with a 15° corneal puncture knife was repaired with fibrin glue plus temporary suture and therapeutic corneal contact lens (9 eyes) or with 3 to 5 interrupted 10-0 nylon sutures (9 eyes) with the fellow eyes acted as the internal controls respectively.Operative time was compared between the two groups.Clinic observation was performed with slit lamp microscope.Animals were humanely sacrificed for histologic examination at week 1, 3, and 8 to evaluate wound healing. Results The average operation time was (3.48±0.48) minutes in the adhesive group, which was significantly lower than that in the suture group ([7.77 ± 1.30]minutes) (t=9.28, P<0.01). The postoperative slit lamp microscope observation indicated corneal wounds were quickly and regularly healed in the glued corneas compared with the stitched ones.The histologic examination revealed that glued corneas had regular healing, mild inflammation, and no corneal neovascularization, while sutured corneas showed irregular fibrin arrays, a large number of inflammatory cells and macrophages infiltration around the suture, heavy inflammatory response.Neovascularization was found at week 3 postoperatively. Conclusions Fibrin glue combined with temporary suture and therapeutic corneal contact lens is an effective treatment in sealing large irregular corneal wounds with considerable advantages over traditional sutures, including simplified operative technique, short surgery time, less postoperative irritation, mild inflammation, more regular wound healing, short healing time, and no corneal neovascularization. Key words: Fibrin glue; Suture; Full-thickness corneal penetrating injury; Disease model/animal; Corneal contact lens/therapeutic

Distinguishing between contact lens warpage and ectasia: Usefulness of optical coherence tomography epithelial thickness mapping

To distinguish between corneal ectasia and contact lens-related warpage by characteristic patterns on corneal topography and optical coherence tomography (OCT) epithelial thickness maps. Casey Eye Institute, Portland, Oregon, USA. Prospective and retrospective case series. Axial and mean power maps were obtained on corneal topography systems. Epithelial thickness maps were generated using RTVue OCT. A sector divider was applied to all maps. The locations of the minimum epithelial thickness, maximum epithelial thickness, maximum axial power, and maximum mean power were determined based on sector averages. Agreement was defined as the extremums occurring in the same or adjacent sectors. Twenty-one eyes with keratoconus, 6 eyes with forme fruste keratoconus (better eye of asymmetric keratoconus), and 15 eyes with contact lens-related warpage were identified. The keratoconus and forme fruste keratoconus eyes had coincident topographic steepening with epithelial thinning. The locations of minimum epithelial thickness and maximum axial power agreed in 90% of the keratoconic eyes, while the minimum epithelial thickness and maximum mean power agreed in 95% of them. Conversely, the warpage eyes had coincident topographic steepening with epithelial thickening and normal pachymetry maps. The locations of maximum epithelial thickness and maximum axial power agreed in 93% of the warpage eyes, while the maximum epithelial thickness and maximum mean power agreed in all warpage eyes. Results show that epithelial thickness maps and corneal topographic maps are powerful synergistic tools in evaluating eyes with abnormal topography and can help differentiate between keratoconus and nonectatic conditions.

Ocular ketoconazole-loaded proniosomal gels: formulation, ex vivo corneal permeation and in vivo studies

Context: Vesicular drug carriers for ocular delivery have gained a real potential. Proniosomal gels as ocular drug carriers have been proven to be an effective way to improve bioavailability and patient compliance.Objective: Formulation and in vitro/ex vivo/in vivo characterization of ketoconazole (KET)-loaded proniosomal gels for the treatment of ocular keratitis.Materials and methods: The effect of formulation variables; HLB value, type and concentration of non-ionic surfactants (Tweens, Spans, Brijs and Pluronics) with or without lecithin on the entrapment efficiency (EE%), vesicle size and in vitro KET release was evaluated. An ex vivo corneal permeation study to determine the level of KET in the external eye tissue of albino rabbits and an in vivo assessment of the level of KET in the aqueous humors were performed.Results and discussion: In vivo evaluation showed an increase in bioavailability up to 20-folds from the optimum KET proniosomal gel formula in the aqueous humor compared to drug suspension (KET-SP). The selected formulae were composed of spans being hydrophobic suggesting the potential use of a more hydrophobic surfactant as Span during the formulation of formulae. Factors that stabilize the vesicle membrane and increase the entrapment efficiency of KET (namely low HLB, long alkyl chain, high phase transition temperature) slowed down the release profile.Conclusions: Proniosomal gels as drug delivery carriers were proven to be a promising approach to increase corneal contact and permeation as well as retention time in the eye resulting in a sustained action and enhanced bioavailability.

Isolation and genotyping of Acanthamoeba strains (T4, T9, and T11) from amoebic keratitis patients in Iran.

The continuous increase in Acanthamoeba keratitis, a severe corneal infection, worldwide is mainly due to the increase in the number of soft contact lens users. In the present study, which involves a 5-year study, a total of 138 corneal scraps and contact lenses together with their paraphernalias were obtained from suspected amoebic keratitis patients. All samples were cultured using culture-enrichment method. Pathogenic assay, using thermotolerance and osmotolerance tests were also performed on the positive strains. Sequencing of the isolated strains was done by targeting the DF3 region of 18s rRNA gene. The results revealed that 18 (13%) of patients were infected with Acanthamoeba spp. As expected, T4 genotype was the most common genotype among the clinical samples; however, in three cases, Acanthamoeba belonging to T11 and T9 were detected. Interestingly, T9 genotype, commonly classified as non-pathogenic amoebae, was identified as a causal agent of a patient with amoebic keratitis. From the pathogenic assay, four strains belonging to T4 genotypes were highly pathogenic. This is the first report of Acanthamoeba T9 genotypes isolated in Iran and the first report of T9 type occurring in amoebic keratitis patients worldwide. Due to the increasing trend of amoebic keratitis (AK) and the identification of new genotypes, such as T9 as the causative agent of AK, more researches in this field are necessary in the region and the world at large.

Clinical Features, Antibiotic Susceptibility Profiles, and Outcomes of Infectious Keratitis Caused by Achromobacter xylosoxidans.

Reports on Achromobacter xylosoxidans ocular infections are increasing, drawing attention to its emerging role in infectious keratitis. The purpose of this study is to report the clinical features, antibiotic sensitivities, and visual outcomes of infectious keratitis secondary to Achromobacter xylosoxidans. A microbiology database and clinical chart review was performed in all patients diagnosed with A. xylosoxidans keratitis at the Bascom Palmer Eye Institute between the years 1987 and 2014. Initial presentation, antimicrobial susceptibilities, minimum inhibitory concentrations (MICs), treatment course, and outcomes were recorded. Twenty-eight patients were identified. The main risk factors were corneal graft (n = 8, 28.6%) and contact lens wear (n = 8, 28.6%). On presentation, visual acuity was 20/100 or worse in 20 (71.2%) patients. Hypopyon was present in 7 (25.0%) patients. In most cases, topical fluoroquinolones or tobramycin were the initial treatment, often accompanied by vancomycin. High susceptibility rates were found for piperacillin [100%, minimum inhibitory concentration for 90% of isolates (MIC90) = 8] and ticarcillin (100%, MIC90 = 16). Low susceptibility rates were documented for ciprofloxacin (46.7%, MIC90 = 8), tobramycin (26.7%, MIC90 = 16), and gentamicin (20%, MIC90 = 16). One (3.6%) patient suffered endophthalmitis. Six (21.4%) patients underwent therapeutic penetrating keratoplasty, and 2 (7.1%) patients had conjunctival flap surgery. Visual acuity at final follow-up was 20/100 or worse in 16 (57.1%) patients. Infectious keratitis caused by A. xylosoxidans is associated with poor visual outcomes. Fluoroquinolones and aminoglycosides are not appropriate treatments for these ocular infections. Further studies are needed to define the clinical application of compound piperacillin and ticarcillin eye drops.

A review of African studies on central corneal thickness

Recently, there has been increasing interest in understanding central corneal thickness (CCT) measurements in various populations. This may be related to the influence of CCT in the diagnosis, classification and management of glaucoma. In addition, CCT measurements are also important for monitoring corneal diseases and contact lens wear, indicating the overall health of the cornea and assessing eligibility for refractive surgery. This article reviews studies that have reported CCT measurements in non-glaucomatous African sub-populations. The CCT measurements, gender associations and limitations of these studies are highlighted. The findings of these studies and their implications are discussed in relation to global studies reporting on CCT measurements.

Study on mechanical and optical properties of poly(vinyl alcohol) hydrogel used as soft contact lens

Highly transparent hydrogel has been proposed as promising soft corneal contact lenses. In this paper, poly(vinyl alcohol) (PVA) hydrogels with high transparence were prepared by dissolving PVA powders into dimethyl sulfoxide (DMSO) aqueous solutions and followed by freeze–thaw cycle technology. The various influences such as PVA concentration, freeze–thaw cycle times and DMSO concentration on the tensile mechanical and transparent characteristics of the PVA hydrogel have been investigated. Results of the tensile mechanical investigation revealed that the tensile strength of PVA hydrogel increased with the rise of PVA concentration and freeze–thaw cycle times, but decreased with the increasing DMSO concentration. The results of optical tests indicated that the light transmittance of the PVA hydrogel increased with the increasing light wavelength, PVA and DMSO concentrations. Moreover, the light transmittance of the PVA hydrogel first increased and then decreased with the rise of freeze–thaw cycle times.

Norfloxacin Loaded pH Triggered Nanoparticulate in-situ Gel for Extraocular Bacterial Infections: Optimization, Ocular Irritancy and Corneal Toxicity.

In order to achieve prolong corneal contact time of norfloxacin (NFX) for treatment of extra ocular diseases, a pH triggered nanoparticulate in-situ gelling system was designed to explore dual advantage of nanoparticles and in-situ gelling system, for its ocular delivery. NFX loaded nanocarriers were developed by ionotropic gelation technique using chitosan as a matrix forming polymer, cross-linked by an anionic crosslinker sodium tripolyphosphate (TPP). Optimization of nanoformulations was done by 3(2) full factorial design using chitosan and TPP concentration(s) as the independent variables and particle size, % entrapment efficiency and % cumulative drug release as the responses. The experimental design was validated by extra design check point formulation (N10). The optimized formulation (N4) selected on the basis of highest desirability factor (0.895) was developed as in-situ gelling system using carbapol934 and evaluated. The best in-situ gelling formulation (N4G5) was sufficiently mucoadhesive, corneal toxicity, antibacterial activity and free from ocular irritancy.

In-vitro method for determining corneal tissue friction and damage due to contact lens sliding

It is postulated that frictional energy due to contact lens rubbing against corneal tissue correlates positively with cell damage; where the damage is due to a fatigue mechanism (repeated stressing). Efforts were made to develop a relatively rapid in-vitro method capable of exploring this postulate. Measurements of the dynamic coefficient of friction (DCoF) between corneal epithelium and contact lenses, associated frictional forces, frictional energy, and corresponding cell damage were made using SkinEthic (Lyon, France) human corneal epithelial (HCE) constructs and commercially available contact lenses. Five silicone hydrogels (SiHs) and two polyhydroxyethlymethacrylate (p-HEMA) lens types were employed. Frictional forces were measured while the lens was rubbed against a construct that was moistened using a tear-like fluid. The exposed constructs were stained, imaged, and processed using a custom Matlab code. The range of DCoF values observed here extended from about 0.04 to 0.07. The frictional energy varied from about 0.03mJ to 0.08mJ. The results indicated a moderate correlation (Pearson's R=0.79, P=3.4%) between the frictional energy and cell damage. The authors believe that these results support the notion that cell damage can be caused by fatigue. Future efforts should explore how cell damage relates to a potentially more relevant metric, power density.

Clinical comparison between brachytherapy of 0.5% loteprednol etabonate eye drops and long-term therapy of 0.1% fluorometholone eye drops after LASEK

Background Conventional corticosteroid therapy after laser epithelial keratomileusis (LASEK) is topical application of 0.1% fluorometholone eye drops for 4 months, but this therapy increases the ocular hypertension risk and leads to poor compliance in patients. It is necessary to explore a safe and effective brachytherapeutic drug. Objective This study was to compare the clinical outcomes between the brachytherapy of 0.5% loteprednol etabonate eye drops and the long-term therapy of 0.1% fluorometholone eye drops after LASEK. Methods Clinical data were retrospectively analyzed from 208 right eyes in 208 mild and moderate myopia patients who received LASEK at Peking University Third Hospital from 2009 to 2013. The eye drops of 0.5% loteprednol etabonate was used 6 times daily since operation day until postoperative day 5, and 4 times daily for a week, and then tapered for three consecutive weeks in 104 eyes of the loteprednol group after LASEK, and 0.1% fluorometholone eye drops was applied topically 4 times daily for initial one month and then tapered for three consecutive months in another 104 eyes in the fluorometholone group after LASEK. Corneal epithelial healing time was compared between the two groups by recording the wearing duration of corneal contact lens. Noncontact intraocular pressure (IOP) was detected and corrected 5 days, 2 weeks, 1 month and 3, 6 months after LASEK. Haze was scored based on the criteria of Cheng under the slit lamp microscope and apparently optometry was performed 1 month and 3, 6 months after LASEK. Results The number of eyes removed corneal contact lens in 5, 6 and 7 days after LASEK was not significantly different between the loteprednol group and the fluorometholone group (χ2=1.180, P=0.554). No considerable differences were seen in the eye numbers with the equivalent spherical lens (absolute value) ≤0.5 D in 1 month, 3 months and 6 months after LASEK (Z=-1.028, P=0.304; Z=-0.398, P=0.691; Z=-0.445, P=0.656). In the fifth days after surgery, the median corrected IOP was 13.52 mmHg and 13.12 mmHg in the loteprednol group and the fluorometholone group, respectively, showing a significant difference between them (Z=-1.985, P=0.047), but no significant differences were found in IOP in 2 weeks, 1 month and 3 months, 6 months after surgery between the two groups (all at P>0.05). IOP elevated (postoperative IOP-preoperative IOP≥5 mmHg) after LASEK in 5 eyes in the loteprednol group and 4 eyes in the fluorometholone group (χ2=0.116, P=0.733). In 1 month after surgery, the number of eyes in different grades of haze was significantly decreased in the loteprednol group compared with the fluorometholone group (χ2=13.506, P=0.009), however, there was no significant differences in haze grading in postoperative 3 months and 6 months between the two groups (χ2=2.199, P=0.699; χ2=1.154, P=0.562). Conclusions Brachytherapy of 0.5% loteprednol etabonate eye drops appears to have a similar effect in anti-inflammation and inhibition of haze to the long-term therapy of 0.1% fluorometholone eye drops after LASEK. Furthermore, topical application of 0.5% loteprednol etabonate eye drops dose not increase the risk of ocular hypertension. Key words: Adrenal cortex hormones/therapeutic use; Anti-inflammatory agents/therapeutic use; Keratomileusis, laser epithelial; Myopia/surgery; Postoperative complications/drug therapy; Loteprednol etabonate; Fluorometholone; Eye drops; Comparative study

In vitro and in vivo ocular safety and eye surface permanence determination by direct and Magnetic Resonance Imaging of ion-sensitive hydrogels based on gellan gum and kappa-carrageenan

Gellan gum, kappa-carrageenan and alginates are natural polysaccharides able to interact with different cations that can be used to elaborate ion-activated in situ gelling systems for different uses. The interaction between fluid solutions of these polysaccharides and cations presents into the tear made these biopolymers very interesting to elaborate ophthalmic drug delivery systems. The main purpose of this study is to evaluate the ability of mixtures of these polymers to obtain ion-activated ophthalmic in situ gelling systems with optimal properties for ocular use. To achieve this purpose different proportion of the biopolymers were analyzed using a mixture experimental design evaluating their transparency, mechanical properties and bioadhesion in the absence and presence of simulated tear fluid. Tear induces a rapid sol-to-gel phase transition in the mixtures forming a consistent hydrogel. The solution composed by 80% of gellan gum and 20% kappa-carrageenan showed the best mechanical and mucoadhesive properties. This mixture was evaluated for rheological behavior, microstructure, cytotoxicity, acute corneal irritancy, ex-vivo and in vivo ocular toxicity and in vivo corneal contact time using Magnetic Resonance Images (MRI) techniques. Result indicates that the system is safe at ophthalmic level and produces an extensive ocular permanence higher than 6h.

A randomized controlled clinical trial of the effectiveness and safety between aspherical and NUV soft hydrophilic contact lenses for myopia patients

Background The clinical effectiveness of soft corneal contact lens for correction of myopia has been confirmed.Theoretically, aspherical soft hydrophilic corneal contact lens has better visual qualify for myopic eyes, and the lenses have been applied widely.But abnormal tear film, even many cornea and conjuctiva diseases caused by soft contact lens have been reported, so the effectiveness and safety of aspherical soft hydrophilic corneal contact lens are worth concerning. Objective This clinical trail was to compare the effectiveness and safety between aspherical and NUV soft hydrophilic contact lens for myopic eyes. Methods A randomized, double-blind and controlled clinical study was performed under the approval of Ethic Committee of Qingdao Municipal Hospital and informed consent of each patient.One hundred and forty eyes of 70 myopic patients were enrolled in Qingdao Municipal Hospital from July to October, 2012.The subjects were randomized into the trial group and control group using random number table.Aspherical soft hydrophilic contact lenses were worn in the trial group and NUV soft hydrophilic contact lenses were worn in the control group.The characteristics of the lens surface, outcomes and the eye number in different scores of ocular signs and symptoms were assessed before and 15 minutes, 1 week, 2 weeks and 1 month after wearing lenses. Results The sores of humidity of anterior surface, the sediment in anterior and posterior surface are 0 in both lenses in various time points after wearing.The corrected visual acuity of all the subjects were ≥1.0.The eye number of 2-3 scores in various ocular signs was 0 in both groups, but the eye number of 1 score in palpebral conjunctival congestion and limbus congestion were more in the trail group than those in the control group in different time points (all at P 0.05). There was no eye for 2-3 scores of eye symptoms in both groups.The eye number for 1 score in foreign body sensation increased in the target-trail group compared to the control group at various time points (P=0.002, 0.006, 0.005, 0.005). However, there was no statistically significant differences in the eye number for 1 score in visual clearness and stability between the two groups at the follow-up duration (all at P>0.05). Conclusions Aspherical soft hydrophilic corneal contact lens has good outcomes in corrected visual acuity for myopia like NUV soft hydrophilic contact lens, but the wearing of aspherical soft hydrophilic corneal contact lens induces more ocular discomfortableness. Key words: Contact lenses, hydrophilic/adverse effects; Myopia; Aspherical lens; Effectiveness; Safety; Randomized controlled clinical trail

Corneal health and contact lens wear: Ion chromatography as an electrolyte probe

Purpose: Tear osmolarity and the concentrations of ocular electrolytes in the eye are known to influence corneal health. Similarly, corneal cells are known to be sensitive to changes in electrolyte balance. Ion transport through contact lenses can influence electrolyte equilibration between preand post-lens tear film. Until now no suitable technique has been identified to quantify these effects. This study utilised ion chromatography to examine multiple ion transport through lenses and the measurement of ex-vivo tear samples. Methods:AmodifiedDionex ion chromatographenabled simultaneous measurement of Na+/K+/Ca2+ and Mg2+ concentrations in both single (5 l) tear samples and lens/membrane permeation studies. In addition to commercial contact lenses, conventional HEMA membranes (40% water) and acrylamide-based corneal model hydrogel membranes (ca 90% water) were mounted in purpose-designed permeability cells and the transport of mixed electrolytes (e.g. 0.25M NaCl, KCl and CaCl2) measured. Results: In baseline studies, the relative ratio of the main tear cations measured in healthy tear film samples was found to be Na+:K+:Ca2+:Mg2+ =140:11:1.2:1. This accord with the observation that the range of K+ concentrations in tears (ca 15–30mM) is high and Ca2+ and Mg2+ concentrations (ca 0.4–0.8 and 0.5–1.1mM) is low, relative to serum. The relative permeability coefficients of lenses and membranes were consistent (i.e. NaCl <KCl » CaCl2) ranging between 141.2×10−7: 148.2×10−7: 98.2×10−7 cm2/s (±5% for 90% acrylamide based hydrogel) and 2.8×10−7:3.2×10−7:0.7×10−7 cm2/s (±5% for 40% HEMA hydrogel). Conclusions: Ion chromatography enables tear electrolytes to be accurately monitored in 5 l samples. This, coupled with tear envelope sampling, provides a means of correlating clinical signs and symptoms with post-lens electrolyte concentrations and the ion permeability coefficients of individual lenses. Anisa Mahomed completed an MEng in Chemical Engineering and then obtained her PhD from the Biomaterials Research Group at Aston University. Her thesis discussed the aspects of the fabrication of novel hydrogels for dermal and ocular applications. She is currently a postdoctoral researcher and her interests include investigating factors that affect the uptake, release and transport of various species from hydrogels and developing analytical techniques to enable the understanding of clinical adverse events related to the use multipurpose solutions.

Corneal epithelial wound healing and bactericidal effect of conditioned medium from human uterine cervical stem cells.

To evaluate the effect of conditioned medium from human uterine cervical stem cells (CM-hUCESCs) on corneal epithelial healing in a rat model of dry eye after alkaline corneal epithelial ulcer. We also tested the bactericidal effect of CM-hUCESCs. Dry eye was induced in rats by extraocular lacrimal gland excision, and corneal ulcers were produced using NaOH. Corneal histologic evaluation was made with hematoxylin-eosin (H&E) staining. Real-time PCR was used to evaluate mRNA expression levels of proinflammatory cytokines. We also studied the bactericidal effect of CM-hUCESCs in vitro and on infected corneal contact lenses (CLs) using Escherichia coli and Staphylococcus epidermidis bacteria. In addition, in order to investigate proteins from CM-hUCESCs that could mediate these effects, we carried out a human cytokine antibody array. After injury, dry eyes treated with CM-hUCESCs significantly improved epithelial regeneration and showed reduced corneal macrophage inflammatory protein-1 alpha (MIP-1α) and TNF-α mRNA expression as compared to untreated eyes and eyes treated with culture medium or sodium hyaluronate ophthalmic drops. In addition, we found in CM-hUCESCs high levels of proteins, such as tissue inhibitors of metalloproteinases 1 and 2, fibroblast growth factor 6 and 7, urokinase receptor, and hepatocyte growth factor, that could mediate these effects. In vitro, CM-hUCESCs showed a clear bactericidal effect on both E. coli and S. epidermidis and CLs infected with S. epidermidis. Analyses of CM-hUCESCs showed elevated levels of proteins that could be involved in the bactericidal effect, such as the chemokine (C-X-C motif) ligands 1, 6, 8, 10, and the chemokine (C-C motif) ligands 5 and 20. Treatment with CM-hUCESCs improved wound healing of alkali-injured corneas and showed a strong bactericidal effect on CLs. Patients using CLs and suffering from dry eye, allergies induced by commercial solutions, or small corneal injuries could benefit from this treatment.

Congenital Corneal Anesthesia and Neurotrophic Keratitis: Diagnosis and Management.

Neurotrophic keratitis (NK) is a rare degenerative disease of the cornea caused by an impairment of corneal sensory innervation, characterized by decreased or absent corneal sensitivity resulting in epithelial keratopathy, ulceration, and perforation. The aetiopathogenesis of corneal sensory innervation impairment in children recognizes the same range of causes as adults, although they are much less frequent in the pediatric population. Some extremely rare congenital diseases could be considered in the aetiopathogenesis of NK in children. Congenital corneal anesthesia is an extremely rare condition that carries considerable diagnostic and therapeutic problems. Typically the onset is up to 3 years of age and the cornea may be affected in isolation or the sensory deficit may exist as a component of a congenital syndrome, or it may be associated with systemic somatic anomalies. Accurate diagnosis and recognition of risk factors is important for lessening long-term sequelae of this condition. Treatment should include frequent topical lubrication and bandage corneal or scleral contact lenses. Surgery may be needed in refractory cases. The purpose of this review is to summarize and update data available on congenital causes and treatment of corneal hypo/anesthesia and, in turn, on congenital NK.