Rabbit Eyes Research Articles

Measurement of vitreous humor pressure in vivo using an optic fiber pressure sensor

We conducted a study to assess the pressure difference between the aqueous and vitreous humors in rabbit eyes using a direct intraocular pressure (IOP) measurement method. A micro-optic-fiber pressure sensor was utilized for this purpose. Preliminary experiments with enucleated porcine eyes confirmed the sensor's accuracy in measuring both aqueous and vitreous humor pressure. The main study involved six healthy albino rabbits, where the sensor measured the pressure in the anterior chamber (aIOP) and posterior vitreous-cavity (pIOP). These measurements were compared to aIOP values obtained through rebound tonometry. Additionally, pre- and postoperative pressure comparisons were made after performing a vitrectomy. Results revealed a significant disparity between aqueous and vitreous humor pressures. Prior to vitrectomy, pIOP was 22.8 mmHg, over twice as high as aIOP (11.0 mmHg), but decreased to a similar level following the procedure. Comparison between the sensor measurements and rebound tonometry showed agreement in aIOP values. In conclusion, our study demonstrates that vitreous humor pressure is consistently higher than aqueous humor pressure, reaching the upper limit of normal IOP. Furthermore, vitrectomy effectively reduces pIOP, aligning it with aIOP. These findings contribute valuable insights into intraocular pressure dynamics and have implications for clinical interventions targeting ocular pressure regulation.

Study on the Dynamics of Microflora during Natural Fermentation of Different Blueberry Wines

Microflora play an important role in the fermentation of blueberry wine, influencing the flavor and nutrient formation. Commercial yeasts give blueberry wines an average flavor profile that does not highlight the specific aroma and origin of the blueberry. In the present study, ITS1-ITS2 region sequencing analysis was performed using Illumina MiSeq high-throughput technology to sequence fermented blueberry wine samples of three Vaccinium ashei varieties, Gardenblue, Powderblue, and Britewell, from the Majiang appellation in Guizhou province to analyze the trends of fungal communities and the diversity of compositional structures in different periods of blueberry wine fermentation. The study’s results revealed that 114 genera from seven phyla were detected in nine samples from different fermentation periods of blueberry wine. The main fungal phyla were Ascomycota, Basidiomycota, Kickxellomycota, Chytridiomycota, and Olpidiomycota. The main fungal genera were Hanseniaspora, Saccharomyces, unidentified, Aureobasidium, Penicillium, Mortierella, Colletotrichum, etc. Hanseniaspora was dominant in the pre-fermentation stage of blueberry wine, accounting for more than 82%; Saccharomyces was the dominant genera in the middle and late fermentation stages of blueberry wine, with Saccharomyces accounting for more than 72% in the middle of fermentation and 93% in the late fermentation stage. This study screened indigenous flora for the natural fermentation of blueberry wine in the Majiang production area of Guizhou, improved the flavor substances of the blueberry wine, highlighted the characteristics of the production area, and made the blueberry wine have the characteristic flavor of the production area.

A novel approach for 25-gauge transconjunctival sutureless vitrectomy to evaluate vitreous substitutes in rabbits.

To improve the standard three-port vitrectomy for establishing and evaluating an endotamponade model in rabbits. Three ports were prepared near the third eyelid of rabbits, and the infusion port was placed at the inferior nasal quadrant with the inserted cannula linking with a self-designed handheld rigid infusion catheter. All right eyes of rabbits underwent a modified 25-gauge vitrectomy and were subsequently filled with balanced salt solution, silicone oil, and eight-arm polyethylene glycols (8-arm PEGs) hydrogel separately for comparison. Ophthalmic examinations were performed regularly to record the changes after the surgery. Successful vitrectomy was achieved among 44 chinchilla rabbits. The mean operation time was 4.51±1.25min. Four eyes (9.1%) presented limited lens touch and two eyes (4.5%) showed retinal touch during surgery. Incision leakage was found in three eyes (6.8%) after surgery. There was no endophthalmitis, hemorrhage, or retinal detachment during the observation period and ophthalmic examinations after the implantation of vitreous substitutes. The modified technique of the standard vitrectomy applied in the endotamponade model in rabbits shows excellent safety and practicality.

Modeling experimental glaucoma for screening studies of antiglaucomatous activity

Introduction: In vivo screening studies, in which the efficacy of dozens of drugs is tested to select several applicants for further study of their safety in humans, are the main stage in the study of the pharmacodynamics of promising antiglaucoma drugs. This imposes a number of specific requirements both on experimental models of glaucoma and on laboratory animals used in the experiment.
 Materials and Methods: 32 male rabbits of the Soviet Сhinchilla breed, 6 male albino rabbits weighing 3-3.5 kg, and 20 outbred white rats weighing 220-250 g were used in total in experiments to reproduce the glaucoma process. All manipulations on the rabbit eye were performed by an ophthalmologist under general anesthesia with telazol. Triamcinolone (vitreous injection) was used to simulate glaucoma in rabbits, lauromacrogol 400 or fine kaolin (anterior chamber injection) was used to simulate glaucoma in rabbits; adrenaline hydrochloride (intraperitoneal administration) was used to simulate glaucoma in rats.
 Results and Discussion: Double intravitreal administration of a suspension of triamcinolone at a dose of 4 mg was the most attractive model in terms of the technique of reproducing the pathology and the results obtained in modeling glaucoma in rabbits. However, this model did not produce a stable increase in intraocular pressure (IOP). Doubling the dose of triamcinolone and replacing chinchilla rabbits with albinos did not lead to a positive result. The introduction of the venous sclerosing drug lauromacrogol 400 into the anterior chamber of the eye proved to be ineffective either. The introduction of finely dispersed kaolin into the anterior chamber of the eye of rabbits led to a persistent increase in IOP. The intraperitoneal administration of epinephrine hydrochloride to rats according to the described method gave no stable results. The increase in IOP became stable only after a significant increase in the dose of adrenaline.
 Conclusion: The conducted studies of four models of glaucoma and their three modifications in animals made it possible to select two of them, which contributed to a stable and fairly long-term increase in IOP in rabbits (introduction of finely dispersed kaolin into the anterior chamber of the eye) and rats (adrenaline-induced model).

EFFECTS OF MONDIA WHITEI ON THE TEAR FUNCTION OF RABBIT EYES

<p><strong>Background:</strong> Dry eye is a serious problem affecting up to 20% of the world’s population. <em>Mondia whitei</em>’s rich androgenic properties create an interest in research focused on its efficacy as an alternative and complementary therapy for the treatment and control of the symptoms of dry eye-related diseases associated with androgen deficiency. <strong>Aim: </strong>This study aimed to investigate the effect of <em>M. whitei</em> on the quality and quantity of tears in rabbit eyes.<strong> Setting: </strong>This study was carried out at the animal house at Masinde Muliro University of Science and Technology, Kakamega, Kenya. <strong>Materials and methods:</strong> The study adopted an experimental study design with 16 New Zealand rabbits. A simple random sampling technique was used to place the rabbits into 4 groups, each group with 4 rabbits. They were tested for tear function to establish a baseline before administration of Benzalkonium Chloride (BAC) (to induce dry eye) and <em>M. whitei</em> extract. Schirmer’s test and fluorescein staining were conducted to observe the tear quantity and quality over a period of 6 days after treatment. The data collected was then cleaned and analyzed. <strong>Results:</strong> The researchers found that the average mean during baseline tear quantity measurement for the groups was 26.5mm, during instilling of BAC the mean dropped to 24.0mm and when <em>M. whitei</em> was administered the mean rose to 27.94mm, indicating that <em>M. whitei</em> greatly improved tear quantity. During baseline tear quality assessment, the average mean for the groups was 0.00 which dropped to 0.94 showing mild staining and when <em>M. whitei</em> was administered dropped further to 1.67 indicating that <em>M. whitei</em> did not improve the tear quality. <strong>Conclusion and Recommendations:</strong> The researchers recommended that more research be done on <em>M. whitei </em>with fewer limitations such as time, to ascertain its effectiveness on tear quality and quantity.</p><p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/soc/0065/a.php" alt="Hit counter" /></p>

Development of dual-functional core-shell electrospun mats with controlled release of anti-inflammatory and anti-bacterial agents for the treatment of corneal alkali burn injuries

In this study, a novel dual-drug carrier for the co-administration of an anti-inflammatory and antibiotic agent consisting of core-shell nanofibers for the treatment of cornea alkali burns was designed. The core-shell nanofibers were prepared via coaxial electrospinning of curcumin-loaded silk fibroin as the core and vancomycin-loaded chitosan/polyvinyl alcohol (PVA) as the shell.Electron microscopy (SEM and TEM) images confirmed the preparation of smooth, bead-free, and continuous fibers that formed clear core-shell structures. For further studies, nanofiber mats were cross-linked by heat treatment to avoid rapid disintegration in water and improve both mechanical properties and drug release. The release profile of curcumin and vancomycin indicated an initial burst release, continued by the extended release of both drugs within 72 hours. Rabbit corneal cells demonstrated high rates of proliferation when evaluated using a cell metabolism assay. Finally, the therapeutic efficiency of core/shell nanofibers in healing cornea alkali burn was studied by microscopic and macroscopic observation, fluorescence staining, and hematoxylin-eosin assay on rabbit eyes. The anti-inflammatory activity of fabricated fibers was evaluated by enzyme-linked immunosorbent assay and Immunofluorescence analysis. In conclusion, using a robust array of in vitro and in vivo experiments this study demonstrated the ability of the dual-drug carriers to promote corneal re-epithelialization, minimize inflammation, and inhibit corneal neovascularization. Since these parameters are critical to the healing of corneal wounds from alkali burns, we suggest that this discovery represents a promising future therapeutic agent that warrants further study in humans.

New Nitinol-based Thermomechanically Adjustable IOL Technology.

To evaluate the feasibility of new adjustable intraocular lens (IOL) technology. The foldable adjustable IOL consists of a nitinol mechanism placed in a haptic-optic cradle. Heating actuators on the nitinol mechanism with a continuous green laser achieve controlled movement of the mechanism and optic. Activation occurs in controlled steps: rotation in 1-degree steps over 360 degrees, and anterior posterior movement in 0.25-diopter (D) steps with a range of +1.50 D. The IOL was tested in vitro and in vivo in a rabbit eye. Foldability and unfolding were demonstrated through a 2.6-mm cartridge. The adjustable lens mechanism was successfully tested in vitro and in vivo. Activation resulted in a change in optic position relative to the haptics and the capsular bag. Activation of the lever and ratchet mechanism showed radial advancement of the IOL clockwise and counterclockwise. In vivo rotatory movement was achieved after activation by the argon laser at 1 week after implantation. Anterior to posterior movement was accomplished by activating the circular spring actuator mechanism in the laboratory model. Uneventful folding and unfolding were performed. A new adjustable IOL with a mechanism that responds in measured steps had been shown to move as planned after activation by argon laser. This was successful in the laboratory in both radial and anterior posterior movement. The radial movement was also proven in vivo in an animal model. Further refinement of the prototype is currently being undertaken. [J Refract Surg. 2023;39(10):662-667.].

Влияние режима эндоскопической лазерной циклодеструкции на воспалительный ответ в передней камере глаза (экспериментально-клиническое исследование)

The selection of the surgical treatment method for glaucoma, as a means of controlling intraocular pressure and stabilizing the glaucomatous process, remains a major challenge in ophthalmology. Laser cyclodestructive interventions offer the possibility of regulating the power and duration of exposure, thus expanding the range of tasks the method can address. This study aimed to compare the degree of postoperative inflammatory response in the anterior chamber of the eye between cyclodestructive interventions with and without the realization of the vaporization biological effect. In the first experimental group of rabbit eyes, the intervention was performed before visual coagulation of the processes, with power ranging from 0.3 to 0.5 W. In the second group, the intervention was performed before the visual realization of the biological vaporization effect, with power ranging from 0.9 to 1.2 W. Clinical observations were retrospectively conducted within the studied group of patients who underwent combined (phacoemulsification + endoscopic laser cyclophotocoagulation) intervention. Throughout the comparison of experimental groups, no statistically significant differences were found. However, a significantly higher inflammatory reaction was observed almost three times more frequently (p = 0.008) in patients where the vaporization biological effect was not fixed. Therefore, despite the results of the experimental study suggesting that excessive damage to the ciliary processes due to the realization of the vaporization effect does not lead to a significant increase in the intensity of the inflammatory response, the clinical observations suggest avoiding such damages whenever possible. Keywords: postoperative iridocyclitis, endoscopic laser cyclodestruction, optical coherence tomography.

Predicting clinical outcome of sulfur mustard induced ocular injury using machine learning model

The sight-threatening sulfur mustard (SM) induced ocular injury presents specific symptoms in each clinical stage. The acute injury develops in all exposed eyes and may heal or deteriorate into chronic late pathology. Early detection of eyes at risk of developing late pathology may assist in providing unique monitoring and specific treatments only to relevant cases. In this study, we evaluated a machine-learning (ML) model for predicting the development of SM-induced late pathology based on clinical data of the acute phase in the rabbit model.Clinical data from 166 rabbit eyes exposed to SM vapor was used retrospectively. The data included a comprehensive clinical evaluation of the cornea, eyelids and conjunctiva using a semi-quantitative clinical score. A random forest classifier ML model, was trained to predict the development of corneal neovascularization four weeks post-ocular exposure to SM vapor using clinical scores recorded three weeks earlier.The overall accuracy in predicting the clinical outcome of SM-induced ocular injury was 73%. The accuracy in identifying eyes at risk of developing corneal neovascularization and future healed eyes was 75% and 59%, respectively. The most important parameters for accurate prediction were conjunctival secretion and corneal opacity at 1w and corneal erosions at 72 h post-exposure.Predicting the clinical outcome of SM-induced ocular injury based on the acute injury parameters using ML is demonstrated for the first time. Although the prediction accuracy was limited, probably due to the small dataset, it pointed out towards various parameters during the acute injury that are important for predicting SM-induced late pathology and revealing possible pathological mechanisms.

Role of NLRP3 in the immunopathogenesis of neurodegenerative eye diseases

Neurodegenerative eye pathology is one of the leading causes of visual impairment and blindness worldwide. Primary open-angle glaucoma (POAG) belongs to the group of neurodegenerative ophthalmic diseases and is characterized by a permanent or periodic increase in intraocular pressure, followed by development of typical visual field defects, decreased visual acuity and optic nerve atrophy. Recent studies show that local inflammation, triggered by the innate immune system is the first line of defense against the pathogens and tissue destruction products, playing an important role in the POAG pathogenesis. The aim was to study the neurodegenerative ophthalmic disorder in a rabbit model, and to compare the data on distribution of alleles and genotypes of the polymorphic marker rs7525979 of NLRP3 gene in the patients with POAG. At the first stage, we studied the complex tissue samples of the retina/retinal pigment epithelium (TCS/RPE) isolated from the eyes of 14 experimental animals and 7 intact rabbits without eye damage. Neurodegenerative pathology of the eye in rabbits was carried out in the Experimental Center at the Helmholtz National Medical Research Center by a single subretinal injection of 0.01 ml of 0.9% sodium chloride solution. NLRP3 gene expression levels in TCS/RPE samples were evaluated by real-time polymerase chain reaction (PCR-RV). At the second stage, peripheral blood samples were examined in patients who were diagnosed with POAG of various stages, as well as without glaucoma. DNA was isolated from blood samples, which was subsequently analyzed for the polymorphic markers study using PCR-RT technique. According to the results of the study, we noted an increased expression of the NLRP3 gene in the TCS/RPE samples from experimental animals with simulated retinal degeneration. Moreover, an association of alleles and genotypes of the NLRP3 gene was revealed in patients with POAG. The data obtained may be indicative for involvement of NLRP3 inflammasome components in development of neurodegenerative retinal lesions in POAG.

Development of Osthole-Loaded Microemulsions as a Prospective Ocular Delivery System for the Treatment of Corneal Neovascularization: In Vitro and In Vivo Assessments.

Osthole (OST), a natural coumarin compound, has shown a significant inhibitory effect on corneal neovascularization (CNV). But, its effect on treating CNV is restricted by its water insolubility. To overcome this limitation, an OST-loaded microemulsion (OST-ME) was created to improve the drug's therapeutic effect on CNV after topical administration. The OST-ME formulation comprised Capryol-90 (CP-90), Cremophor® EL (EL-35), Transcutol-P (TSP) and water, and sodium hyaluronate (SH) was also included to increase viscosity. The OST-ME had a droplet size of 16.18 ± 0.02 nm and a low polydispersity index (0.09 ± 0.00). In vitro drug release from OST-ME fitted well to the Higuchi release kinetics model. Cytotoxicity assays demonstrated that OST-ME was not notably toxic to human corneal epithelial cells (HCECs), and the formulation had no irritation to rabbit eyes. Ocular pharmacokinetics studies showed that the areas under the concentration-time curves (AUC0-t) in the cornea and conjunctiva were 19.74 and 63.96 μg/g*min after the administration of OST-ME, both of which were 28.2- and 102.34-fold higher than those after the administration of OST suspension (OST-Susp). Moreover, OST-ME (0.1%) presented a similar therapeutic effect to commercially available dexamethasone eye drops (0.025%) on CNV in mouse models. In conclusion, the optimized OST-ME exhibited good tolerance and enhanced 28.2- and 102.34-fold bioavailability in the cornea and conjunctiva tissues compared with suspensions in rabbit eyes. The OST-ME is a potential ocular drug delivery for anti-CNV.

Photosynthetic Response of Blueberries Grown in Containers.

Recently, there has been increased interest in container blueberry production as a viable alternative to open-field blueberry planting. Container production of blueberries offers numerous advantages, among these, a lack of limitation by suboptimal soil conditions in the open field and the ability to control substrate pH, drainage, and organic matter. The photosynthetic response for three container-grown Southern highbush blueberry (interspecific Vaccinium hybrids) cultivars including 'Jewel', 'Meadowlark', and 'Victoria' and a rabbiteye blueberry (Vaccinium virgatum) 'Baldwin', were measured during the spring and summer of 2022. It was hypothesized that the three cultivars evaluated would have different photosynthetic responses. The objective of this study was to determine the photosynthetic activity of different blueberry cultivars during the first year of crop establishment. A series of measurements were conducted every 2 h throughout the day and for different dates using a gas exchange data analyzer on newly matured fully expanded leaves located in the top middle section of the canopy for each cultivar. The response curves showed that net photosynthesis (A) became saturated at moderate light, with saturation occurring at a photosynthetic photon flux density (PPFD) of 1932 µmol m-2 s-1. At this point, the rate of CO2 assimilation was approximately 16.84 µmol CO2 m-2 s-1. No differences in (A) were found among cultivars. Overall, the attained values of photosynthesis provide a strong conceptual basis for understanding the cultivar variation response when grown in containers; therefore, the containerized system may serve as a production system for early fruiting blueberries in Alabama, USA.

Therapeutic effects of low-color-temperature light-emitting diodes on dry eye.

As a new technology for treating dry eye diseases, phototherapy has attracted great attention, but the research on its safety and effectiveness is limited. In this study, the therapeutic effects of low-color-temperature light-emitting diodes on dry eye in humans, rabbits, and rats were investigated. In clinical experiments, subjects in both groups read the same paper for 3 h under light sources of two color temperatures: 1900 K (low-color-temperature light-emitting diodes) or 4000 K (artificial fluorescent white light-emitting diodes). The differences in the non-invasive tear film breakup time, tear meniscus height, and conjunctival congestion scores before and after the experiment were compared between the two groups. In animal experiments, corneal epithelial barrier function and tear production of Sprague-Dawley rats and New Zealand white rabbits with dry eye were compared before and after low-color-temperature light-emitting diodes treatment. TUNEL staining and Western blotting were used to detect the apoptosis of corneal and conjunctival cells and the expression of inflammatory factor IL-1β. Low-color-temperature light-emitting diodes prolonged tear film breakup time in patients with dry eye. Moreover, it increased tear secretion, decreased fluorescein sodium staining scores, corneal and conjunctival cell apoptosis, and inflammatory factor expression in rabbits and rats with dry eye. Low-color-temperature light-emitting diodes phototherapy can be used as an effective treatment for dry eye, reducing its symptoms and related ocular surface damage in humans, rabbits, and rats.

Diffusion Depth and Efficacy of Different Infiltration Times for Rose Bengal/Green Light Corneal Cross-linking in Rabbit Eyes.

To explore the diffusion depth and green light corneal cross-linking efficacy of different rose bengal (Rb) infiltration times in rabbit eyes. Twenty-eight fresh rabbit eyes were deepithelialized and infiltrated in 0.1% Rb solution for 2 to 30 minutes. Corneal frozen sections were cut and Rb diffusion depth was observed under the confocal microscope. A further 36 rabbits were randomly divided into eight groups according to the type of treatment (control, Rb infiltration only without irradiation, rose bengal/green light [RGX] for different infiltration times, or riboflavin/ultraviolet radiation [UVX]). The corneas' resistance to keratolysis and biomechanical properties were measured after treatment. After 2, 10, 20, and 30 minutes of infiltration, Rb penetration depths in the corneal stroma were 100, 150, 200, and 270 µm, respectively. The times for complete digestion of the RGX 10 minutes (14.0 ± 1.4 hours), RGX 20 minutes (18.8 ± 1.1 hours), and UVX (51.2 ± 7.2 hours) groups were statistically greater than that of the control group (7.2 ± 1.1 hours). At 10% extension, the Young's modulus of the RGX 20 minutes (36.59 ± 4.90 MPa) and UVX (40.89 ± 2.57 MPa) groups was statistically greater than that of the control group (21.76 ± 5.69 MPa). The diffusion depth of Rb in corneal stroma increased by prolonging the infiltration time. The longer the infiltration time, the better the RGX effect. RGX for 20 minutes showed the best cross-linking efficacy among all RGX groups, albeit not as good as UVX. [J Refract Surg. 2023;39(9):620-626.].

Validation of a novel rebound tonometer (Tono-Vera® Vet) in normal ex vivo rabbit eyes.

The purpose of this study was to validate the use of the Reichert Tono-Vera® Vet tonometer rabbit setting in normal ex vivo rabbit eyes and to compare the rabbit setting to the dog, cat, and horse settings of this tonometer. Six freshly enucleated normal rabbit eyes were cannulated and connected to a fluid reservoir and physiologic monitor. Triplicate measurements were obtained with the four available settings: dog, cat, horse, and rabbit at various intraocular pressures (IOP) ranging from 5 to 80 mmHg. Bland-Altman analysis was utilized to determine bias and 95% limits of agreement for each setting. Linear regression equations for the dog, horse, cat, and rabbit settings were y = 0.8101x + 2.5058, y = 0.7594x - 3.4673, y = 0.6635x + 0.3021, and y = 0.8935x + 1.3295, respectively. All settings demonstrated strong positive linear trends (dog r2 = 0.9644, horse r2 = 0.9456, cat r2 = 0.9309, and rabbit r2 = 0.9558). Bland-Altman plots revealed that the average bias and 95% limits of agreement (mmHg) were -4.73, -12.65, -12.86 and -2.73 and (-15.31, 5.86), (-29.03, 3.74), (-25.67, -0.05), and (-12.21, 6.76) for the dog, horse, cat, and rabbit settings, respectively. The Tono-Vera® Vet rabbit setting provided the most accurate and precise measurements compared with the other settings, but slightly underestimated actual IOP, especially as IOP was increased. This tonometer, using the rabbit setting, is likely to be appropriate for the estimation of IOP in rabbits with the appropriate correction formula applied.

Safety, biocompatibility, and potential functionality of a new accommodative intraocular lens: An experimental study in rabbits

This study aims to evaluate the safety, biocompatibility, and functionality of a new accommodative intraocular lens (IOL) (LUZ, patent PCT/ES2016/070,813) after implantation in rabbit eyes. LUZ (Study) and EyeCee® plus a capsular ring (Control) were implanted in rabbits (n = 8 each) after phacoemulsification. Intraoperative follow-up, long-term clinical follow-up, and functional IOL studies were carried out periodically for up to 180 days. A macroscopic examination of the eyeballs to reveal abnormalities and determine the implant centering and a microscopic examination to semi-quantify cell and tissue response were performed. Statistical analysis of the collected data was finally achieved. During follow-up, no significant changes in the general condition nor the clinical evaluation were observed between both groups. However, Study IOL remained centered throughout the study and did not present severe complications as observed in the Control group. Functional studies did not reveal significant differences between both materials. Study showed better centering, fewer adhesions, and maintenance of an opening capsular bag compared to the Control. Local biological effects caused by Study implantation are minimal and comparable to the Control. Therefore, LUZ showed no clinical signs or histological response of adverse reaction to the implanted material, according to UNE-EN ISO 11979-5 and 10993-6. Functionality must be confirmed in another animal species with greater lens accommodation capacity than the rabbit. LUZ keeps the capsular bag open, favoring its centering and avoiding fibrosis and adherence to the bag; this allows potential accommodation of this IOL and theoretically enables the patient to focus dynamically.

Poster Session: Estimation of scleral biomechanical properties from air-puff-coupled optical coherence tomography.

Progression of myopia is usually accompanied by axial overgrowth of the eyeball, which affects scleral biomechanics (BM). To study scleral biomechanics, we propose the use of air-puff deformation swept-source OCT imaging. Air-puff deformation imaging was performed at different sites of ex vivo porcine (n=5) and rabbit (n=3) eyes, (<24hr postmortem): Nasal/temporal equatorial and posterior sclera (NE, NP, TE, TP), superior (S) and inferior (I) sclera, and cornea (C). Intraocular pressure was kept at 15mmHg. Deformation data were used as input to inverse finite element model (FEM) algorithms to reconstruct BM properties. Experimental deformation amplitudes showed dependence on the animal model, with porcine scleras exhibiting greater inter-site variation (displacement of S, I was up to four times greater than that of N, T), while rabbit scleras exhibited at most 40% of displacement differences between all sites. Both models showed significant (p<.001) differences in the temporal deformation profile between sclera and (C), but similarities in all scleral locations, suggesting that the scleral temporal profile is independent of scleral thickness variations. The FEM estimated an elastic modulus of 1.84 ± 0.30 MPa (I) to 6.04 ± 2.11 MPa (TE) for the porcine sclera. The use of scleral air-puff imaging is promising for noninvasive investigation of structural changes in the sclera associated with myopia and for monitoring possible modulation of scleral stiffness with myopia treatment.

Poster Session: Experimental assessment of scleral anisotropy using multi-meridian air-coupled ultrasonic optical coherence elastography.

Scleral biomechanics plays a key role in the understanding of myopia progression. In this study, we characterized the elastic properties of sclera using an air-coupled ultrasonic (ACUS) optical coherence elastography (OCE) system. New Zealand rabbit eyes (n=7) were measured (<24hr postmortem) in four scleral locations: superior/inferior temporal (ST, IT), and superior/inferior nasal (SN, IN) maintaining an intraocular pressure of 15 mmHg. Elastic waves were induced in the sclera, and wave propagation velocity and shear modulus were measured along two directions: circumferential (superior-inferior) and meridional (nasal-temporal). Wave velocity in scleral tissue ranged from 6 to 24 m/s and shear modulus from 11 to 150 kPa. Velocity was significantly higher (p<.001) in the circumferential vs. meridional directions in the following locations: ST:15.83±2.85 vs 9.43±1.68 m/s, IT:15.00±3.98 vs 8.93±1.53 m/s; SN:16.79±4.30 vs 9.27±1.47 m/s; and IN:13.92±3.85 vs 8.57±1.46 m/s. The average shear modulus in the circumferential was also significantly higher (p<.001) than in the meridional direction for all locations: 65.37±6.04 vs 22.55±1.36 kPa. These results show that the rabbit sclera is mechanically anisotropic with higher rigidity in the circumferential direction compared to the meridional direction. ACUS-OCE is a promising non-invasive method to quantify the biomechanical changes in scleral tissue for future studies involving myopia treatments.

A workflow to visualize vertebrate eyes in 3D.

To establish a workflow to visualize the surgical anatomy in 3D based on histological data of eyes of experimental animals for improving the planning of complex surgical procedures. Four C57BL/6J wild-type(wt) mouse eyes, three Brown Norway rat eyes and four Chinchilla Bastard rabbit eyes were enucleated and processed for standard histology with serial sections and hematoxylin and eosin staining. Image stacks were processed to obtain a representation of the eye anatomy in 3D. In addition, virtual image stacks and 3D point clouds were generated by processing sagittal sections of eyes with stepwise 180° rotation and projection around the eye axis to construct a rotationally symmetric 3D model from one single sagittal section. Serial sections of whole eyes of mice, rats and rabbits showed significant artifacts interfering with a practical image stack generation and straightforward 3D reconstruction despite the application of image registration techniques. A workflow was established to obtain a 3D image of the eye based on virtual image stacks and point cloud generation by rotation of a single sagittal section of the eye around the symmetry axis. By analyzing the tissue shrinkage during histological processing true biometric reconstructions of the eyes were feasible making the resulting model usable for 3D modeling and simulation, e.g. for planning of complex surgical procedures in different species. Because serial sections of the eye with standard histological protocols yielded too many artifacts for a straightforward 3D visualization we reconstructed a pseudorealistic 3D model based on virtual image stacks and point cloud generation calculated from a single sagittal section of the eye. Such a model detailing microscopic structures of the whole eye will allow for a specific planning of surgical procedures in small animal eyes in order to prevent surgical complications in a very early stage of an experiment and it will support the design and development of complex intraocular implants. It will therefore be helpful in surgical teaching and improve laboratory animal welfare by an expected reduction of experimental animal numbers. Further processing including integration of mechanical tissue properties is needed to convert these 3D models into a practical virtual reality teaching and simulation platform for eyes of several species.

Effect of Fluid Flow Direction on Intravitreal Injections of Drugs into Eye

The amount of drug in the eye depends on various factors such as genetics, layers structure, temperature distribution, and aqueous humor flow field. The heat transfer, fluid flow field, and drug delivery in the eye are numerically simulated using a three-dimensional model. The results are compared with experimental data on human and rabbit eyes. The effect of ambient temperature on the flow field in standing and supine positions was investigated. Then the transfer of drug concentration by intravitreal injection method was simulated using the obtained flow field. The results showed that the temperature distribution and the position of the eye relative to the direction of gravity have a significant role in the process of concentration transfer in the anterior segment of the eye. The results showed that in an intravitreal injection method, the drug has a significant concentration in the posterior part of the eye. In the intravitreal injection method with the injection of 1.25 mg of the drug, the maximum concentration in the vitreous humor is 1575.5 μg/ml, and the drug vanishes into the eye after 30 days. In this case, the maximum drug concentration in the aqueous humor is 30.16 μg/ml, which occurs after 1.5 days.