In this study we fabricated free standing multilayer films of polyelectrolyte complexes for potential use in tissue engineering of corneal stroma by using the layer-by-layer (LbL) approach. In the formation of these LbL films negatively charged, photocrosslinkable (methacrylated) hyaluronic acid (MA-HA) was used along with polycations polyethyleneimine (PEI) and poly(L-lysine) (PLL). Type I collagen (Col) was blended in with PLL for improving the water absorption and cell attachment properties of the films. It was shown that the LbL films could be easily peeled off from glass substrates due to the photocrosslinking of one of the LbL components, the hyaluronic acid. Film growth and composition were monitored with FTIR-ATR. Heights of peaks at 3383 cm-1, and 2958 cm-1increased along with the bilayer number confirming the polymer build-up. Film integrity and thickness were investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Films thicker than 5 bilayers (BLs) were found to be uniform in appearance and 10 BL (PEI/MeHA) films were calculated to be ca. 6 &mu / m thick. Atomic force microscopy (AFM) revealed that as the number of BLs increased, surface roughness decreased. Activity of methacrylated hyaluronic acid was shown by the increased resistance of photocrosslinked multilayer films against hydrolysis by hyaluronidase. Patterns could be created on the films by photocrosslinking further proving that the crosslinking step is successful. Since the ultimate goal was to construct a corneal stroma PEI/MA-HA films were tested with corneal stroma cells, keratocytes. Cell proliferation on PEI/MA-HA films was quite poor in comparison to TCPS. In order to improve the cell adhesion the tests were repeated with PLL/MA-HA. Collagen was added to decrease the hydrophilicity and introduce cell adhesion sequences (Arg-Gly-Asp, RGD) to improve cell proliferation on the films and thus PLL+Col/MA-HA films were also tested. Introduction of collagen to the PLL/MA-HA films was found to decrease water retention of the multilayer films and improve cell viability and proliferation. Col+PLL/MA-HA LbL thus appear to be a promising platform for tissue engineering, especially of corneal stroma.

Polarized light has the ability to increase the specificity of the investigation of biomedical samples and is finding greater utilization in the fields of medical diagnostics, sensing, and measurement. In particular, this dissertation focuses on the application of polarized light to address a major obstacle in the development of an optical based polarimetric non-invasive glucose detector that has the potential to improve the quality of life and prolong the life expectancy of the millions of people afflicted with the disease diabetes mellitus. By achieving the mapping of the relative variations in rabbit corneal birefringence, it is hoped that the understanding of the results contained herein will facilitate the development of techniques to eliminate the effects of changing corneal birefringence on polarimetric glucose measurement through the aqueous humor of the eye. This dissertation also focuses on the application of polarized light to address a major downside of cardiovascular biomechanics research, which is the utilization of toxic chemicals to prepare samples for histological examination. To this end, a polarization microscopy image processing technique is applied to non-stained cardiovascular samples as a means to eliminate, for certain cardiac samples, the necessity for staining using toxic chemicals. The results from this work have the potential to encourage more investigators to join the field of cardiac biomechanics, which studies the remodeling processes responsible for cardiovascular diseases such as myocardial infarct (heart attacks) and congestive heart failure. Cardiovascular disease is epidemic, particularly amongst the population group older than 65 years, and the number of people affected by this disease is expected to increase appreciably as the baby boomer generation transitions into this older, high risk population group. A better understanding of the responsible mechanisms for cardiac tissue remodeling will facilitate the development of better prevention and treatment regimens by improving the early detection and diagnosis of this disease.

Age-related macular degeneration (AMD) is the leading cause for visual impairment and blindness in the elder population of developed countries. The primary underlying cause for significant visual loss is the choroidal neovascularization (CNV). Current treatment strategies for AMD include laser photocoagulation, photodynamic therapy (PDT) and excision of neovascular membranes, but have met with limited success. In our previous studies, we demonstrated that gene delivery of angiogenesis inhibitor vasostatin (VS) attenuated the corneal neovascularization in animals. The primary objective of this study was to investigate gene delivery of vasostatin (VS) attenuated the choroidal neovascularization in animals. Retinal and visual function will be evaluated. However, systematic expression of angiogenesis inhibitor may bring adverse effects to physiological processes. The feasibility, efficiency and safety of gene delivery with systemic and local routes were evaluated. Intramuscular polymer-based gene delivery had no side effect such as virus vector and revealed the safety. Recombinant adenovirus (Ad) was used gene delivery system because of its high titer, wide host range, and transduction efficiency. Adeno-associated virus (AAV) represents highly efficient that can facilirate long-term transduction. We propose to improve the efficacy and safety of VS gene delivery, and to search for the effective delivery route and other adjuvant therapy in conjunction with VS for treatment of CNV. Recently, PDT with veteporfin is an established treatment for subfoveal CNV secondary to AMD. We tried to compare the effect and safety of standard and reduced-dose light application PDT in an animal mocel of CNV. The 180-residue VS and its 48-residue (VS48) inhibited the migration and tube formation in cultured endothelial cells. Topical VS application suppresses the progression of laser-induced CNV via angiogenesis ihhibition, as well as in VS48. VS-48 inhibited the growthof vessels in arota rings. Electroretinograms (ERG) analysis revealed that topical VS-48 application for 21 days had no effect on rat retinal functions. Topical VS-48 treatment significantly reversed the CNV-induced alterations in ERG. Transfection of pCMV3-VS into muscle cells resulted in increased production and release of exogenous VS, which specifically inhibited the proliferation of endothelial cells. Rats treated with intrmuscular injection with PVP-VS also showed a significant reduction in the CNV lesions for at least 42 days. Subconjunctival injection with Ad vector revealed no retinal toxicity in ERG. Ad-luciferase via subconjunctival injections showed ocular expression for as long as 112 days by using bioluminescence image analysis in rodent. AAV-luciferase via subconjunctival injections showed ocular expression for as long as 365 days by using bioluminescence image analysis in mice, and AAV serotype 5-luciferase even showed expression lasting for 2 years. Suppression of laser photocoagulation¡Vinduced CNV by Ad-VS was documented in rat model. Combination therapies are important as treatment options. We demonstrated that PDT could effectively attenuate CNV in a rat model, and reduced doses, worked just as well as the standard dose. In the preliminary study of PDT combined topical VS application, treatment led to CNV attenuation more than alone with PDT. The above experiments would enable us to demonstrate that the vasostatin delivery might be a promising strategy for the treatment of AMD and other retinal or ocular disorders. Furthermore, the results from animal studies might be extrapolated for future clinical application.

Dissertation (Ph.D.)--University of South Florida, 2009. / Title from PDF of title page. Document formatted into pages; contains 91 pages. Includes vita. Includes bibliographical references.

Purpose: The purpose of this study was to compare corneal thickness measured both centrally and midperipherally, between two instruments using different measuring principles. The study also looked at correlation between corneal thickness and intraocular pressure (IOP). Methods: Central and midperipheral corneal thickness was measured on the right eyes of 31 subjects with two different instruments. Instruments were Scheimpflug-camera from Bon Sirius and an AS/OCT from Optos. Measurements were taken on central cornea (CCT) and midperipheral (nasal (NCT), temporal (TCT), superior (SCT) and inferior (ICT)) at a distance of 1.75 mm from the apex. Mean age of the subjects was 23.6 ± 4.5 years. (19-44 years). A CT-80A non-contact tonometer (NonCT) from Topcon was used to measure the intraocular pressure (IOP). Results: A mean-value for central corneal thickness was calculated to 542.4 µm and 540.4 µm for Bon Sirius and AS/OCT repectively. Remaining measured points had mean-values for corneal thickness of, NCT: 577.7 µm & 558.5 µm. TCT: 555.0 µm & 545.2 µm. SCT: 585.7 µm & 554.5 µm. ICT: 563.0 µm & 548.9 µm, respectively. Mean-difference for CCT was 2.4 µm and it showed a significant difference between the two instruments with a p-value of 0.007. Remaining measured points all showed a significant difference of p<0.05. NCT: 19.2 µm. TCT: 9.8 µm. SCT: 31 µm. ICT: 14 µm. A correlation between IOP and CCT measured in both Sirius and AS/OCT was positive with r = 0.7 and p<0.05. Conclusion: The results showed that Sirius gives higher values for corneal thickness then ASOCT in all five measurement points. The results show that these instruments can be used interchangeably when measuring central corneal thickness. However, caution should be used when measuring midperipheral corneal thickness as the there is a significant differences between these two instruments.

The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. It is desirable to possess an instrument that can measure the corneal shape and tear film surface with the same accuracy and resolution that is currently performed on common optical elements. A dual interferometer system for measuring the dynamic corneal topography is designed, built, and verified. The completed system is validated by testing on human subjects. The system consists of two co-aligned polarization splitting Twyman-Green interferometers designed to measure phase instantaneously. The primary interferometer measures the surface of the tear film while the secondary interferometer simultaneously tracks the absolute position of the cornea. Eye motion, ocular variation, and a dynamic tear film surface will result in a non-null configuration of the surface with respect to the interferometer system. A non-null test results in significant interferometer induced errors that add to the measured phase. New algorithms are developed to recover the absolute surface topography of the tear film and corneal surface from the simultaneous interferometer measurements. The results are high-resolution and high-accuracy surface topography measurements of the in vivo cornea that are captured at standard camera frame rates. This dissertation will cover the development and construction of an interferometer system for measuring the dynamic corneal topography of the human eye. The discussion starts with the completion of an interferometer for measuring the tear film. The tear film interferometer is part of an ongoing research project that has spanned multiple dissertations. For this research, the instrument was tested on human subjects and resulted in refinements to the interferometer design. The final configuration of the tear film interferometer and results from human subjects testing are presented. Feedback from this instrument was used to support the development and construction of the interferometric corneal topographer system. A calibration is performed on the instrument, and then verified against simulated eye surfaces. Finally, the instrument is validated by testing on human subjects. The result is an interferometer system that can non-invasively measure the dynamic corneal topography with greater accuracy and resolution than existing technologies.

Cornea is a part of the optical system of the eye, the condition of which is directly related with the eyesight and its quality. Due to the increasing popularity of the correction of refraction defects with the help of excimer laser, central cornea thickness acquires higher prognostic significance for the determination of the success of the operation and probable post-surgical complications. The objective of the survey is to measure the central corneal thickness of adult residents in Lithuania and the relevant factors having impact on it. In total 1650 residents of Lithuania in the age from 18 to 89 years of age were tested. The survey was carried out in the urban and regional primary health care institutions of the 10 counties of Lithuania and at the Centre of Eye Diseases of the Vilnius University Hospital Santariškių klinikos. The average central corneal thickness of men and women in Lithuania was defined in the survey. It was observed that central corneal thickness is neither conditioned by the gender, height or weight of an individual, nor by the eye refraction or the number and the size of corneal endothelia cells. The thickest cornea was observed in persons under 40 years of age, whereas it becomes thinner each decade from 2 to 8 µm after forty. It was identified in the survey that the thicker the cornea is - the smaller is its curvature. On the basis of the survey a table of central corneal thickness was developed for doctors ophthalmologists to be used in their... [to full text] / Ragena – tai akies optinės sistemos dalis, nuo kurios būklės tiesiogiai priklauso regėjimas ir jo kokybė. Populiarėjant refrakcijos ydų korekcijai eksimeriniu lazeriu, ragenos centrinės dalies storis turi vis didesnę prognostinę reikšmę operacijos sėkmės bei pooperacinių komplikacijų galimybės nustatymui. Darbo tikslas – nustatyti Lietuvos suaugusių gyventojų ragenos centrinės dalies storį bei jį veikiančius veiksnius. Ištirta 1650 Lietuvos gyventojų nuo 18 iki 89 metų amžiaus.Tyrimas vykdytas 10 Lietuvos apskričių miestų ir rajonų pirminėse sveikatos priežiūros įstaigose, bei VUL Santariškių klinikos Akių ligų centre. Tyrimo metu nustatytas Lietuvoje gyvenančių vyrų ir moterų vidutinis ragenos centrinės dalies storis. Nustatyta, kad ragenos centrinės dalies storis nepriklauso nuo žmogaus lyties, ūgio, svorio, bei akių refrakcijos ir ragenos endotelio ląstelių skaičiaus ir dydžio. Storiausia ragena nustatoma iki 40 metų amžiaus, vyresniems nei 40 metų ji plonėja kas dešimtmetį nuo 2 iki 8 µm. Nustatyta, kad kuo storesnė ragena, tuo jos gaubtumas yra mažesnis. Tyrimo pagrindu sukurta skirtingo amžiaus žmonių ragenos centrinės dalies storio lentelė, kuria savo praktiniame darbe galės naudotis visi gydytojai oftalmologai.

Ragena – tai akies optinės sistemos dalis, nuo kurios būklės tiesiogiai priklauso regėjimas ir jo kokybė. Populiarėjant refrakcijos ydų korekcijai eksimeriniu lazeriu, ragenos centrinės dalies storis turi vis didesnę prognostinę reikšmę operacijos sėkmės bei pooperacinių komplikacijų galimybės nustatymui. Darbo tikslas – nustatyti Lietuvos suaugusių gyventojų ragenos centrinės dalies storį bei jį veikiančius veiksnius. Ištirta 1650 Lietuvos gyventojų nuo 18 iki 89 metų amžiaus.Tyrimas vykdytas 10 Lietuvos apskričių miestų ir rajonų pirminėse sveikatos priežiūros įstaigose, bei VUL Santariškių klinikos Akių ligų centre. Tyrimo metu nustatytas Lietuvoje gyvenančių vyrų ir moterų vidutinis ragenos centrinės dalies storis. Nustatyta, kad ragenos centrinės dalies storis nepriklauso nuo žmogaus lyties, ūgio, svorio, bei akių refrakcijos ir ragenos endotelio ląstelių skaičiaus ir dydžio. Storiausia ragena nustatoma iki 40 metų amžiaus, vyresniems nei 40 metų ji plonėja kas dešimtmetį nuo 2 iki 8 µm. Nustatyta, kad kuo storesnė ragena, tuo jos gaubtumas yra mažesnis. Tyrimo pagrindu sukurta skirtingo amžiaus žmonių ragenos centrinės dalies storio lentelė, kuria savo praktiniame darbe galės naudotis visi gydytojai oftalmologai. / Cornea is a part of the optical system of the eye, the condition of which is directly related with the eyesight and its quality. Due to the increasing popularity of the correction of refraction defects with the help of excimer laser, central cornea thickness acquires higher prognostic significance for the determination of the success of the operation and probable post-surgical complications. The objective of the survey is to measure the central corneal thickness of adult residents in Lithuania and the relevant factors having impact on it. In total 1650 residents of Lithuania in the age from 18 to 89 years of age were tested. The survey was carried out in the urban and regional primary health care institutions of the 10 counties of Lithuania and at the Centre of Eye Diseases of the Vilnius University Hospital Santariškių klinikos. The average central corneal thickness of men and women in Lithuania was defined in the survey. It was observed that central corneal thickness is neither conditioned by the gender, height or weight of an individual, nor by the eye refraction or the number and the size of corneal endothelia cells. The thickest cornea was observed in persons under 40 years of age, whereas it becomes thinner each decade from 2 to 8 µm after forty. It was identified in the survey that the thicker the cornea is - the smaller is its curvature. On the basis of the survey a table of central corneal thickness was developed for doctors ophthalmologists to be used in their... [to full text]

The notion that forces from the eyelids can alter the shape of the cornea has been proposed for many years. In recent times, there has been a marked improvement in our ability to measure and define the corneal shape, allowing subtle changes in the cornea to be measured. These improvements have led to the findings that pressure from the eyelids can cause alterations in corneal shape following everyday visual tasks such as reading. There are also theories to suggest that pressure from the eyelids may be involved in the aetiology of corneal astigmatism. In this program of research, a series of experiments were undertaken to investigate the influence of the eyelids on the shape of the cornea. In the first experiment, an investigation into the diurnal variation of corneal shape was carried out by measuring corneal topography at three different times (approximately 9 am, 1 pm and 5 pm) during the day over three days of the week (Monday, Tuesday and Friday). Highly significant diurnal changes were found to occur in the corneal topography of 15 of the 17 subjects. This change typically consisted of horizontal bands of distortion in the superior, and to a lesser extent, inferior cornea, increasing throughout the day (and returning to baseline the next morning). These changes appeared to be related to forces from the eyelids on the anterior cornea. Some changes were also found in corneal astigmatism. Corneal astigmatism power vector J0 (astigmatism 90/180°) was found to increase slightly over the course of the week. Whilst the changes in astigmatism were small in magnitude, this result leaves open the possibility that pressure from the eyelid may cause changes in corneal astigmatism. If pressure from the eyelids is involved in the aetiology of corneal astigmatism, then one may expect associations to exist between certain characteristics of the eyelids and corneal shape. An experiment was then undertaken to explore these possible associations. We defined the average morphology of the palpebral fissure in different angles of vertical gaze for 100 young normal subjects. This was achieved through analysis of digital images that were captured in primary gaze, 20° downgaze and 40° downgaze. Parameters defining the size, position, angle and contour of the eyelids were determined. Highly significant changes were found to occur in the palpebral fissure with downward gaze. The palpebral aperture narrows in downward gaze, and the angle of the eyelids changes from being slightly upward slanted in primary gaze, to being slightly downward slanted in downward gaze. The eyelid margin contour also flattens significantly in downward gaze. The average topography of the central and peripheral cornea was also defined for this same population. A technique was used that allowed the capture and subsequent combination of topography data from both the central and the peripheral cornea. The use of this technique provided a large corneal topography map, with data extending close to the limbus for each subject. Marked flattening was found to occur in the peripheral cornea and a conic section was found to be a poor descriptor of corneal contour in the periphery (i.e. greater than 6 mm diameter). Corneal astigmatism was also found on average to reduce in the periphery. However a number of distinct patterns of peripheral corneal astigmatism were noted in the population. Corneal astigmatism in the peripheral cornea was either found to remain stable (59% of subjects), increase (10% of subjects) or reduce (31% of subjects) in magnitude in comparison to the amount of central corneal astigmatism. We also investigated associations between the parameters defining the palpebral fissure and parameters describing corneal shape in this population of subjects. A number of highly significant associations were found between the morphology of the palpebral fissure in primary gaze and the shape of the cornea. A general tendency was found for subjects with wider horizontal palpebral fissure widths to exhibit larger corneas and also flatter central corneal powers. There were also highly significant associations found between the angle of the eyelids and the axis of corneal astigmatism, but not the magnitude of corneal astigmatism. The associations found between corneal astigmatism and palpebral fissure morphology is further evidence supporting the hypothesis that pressure from the eyelids is involved in the aetiology of corneal astigmatism. The results of these investigations have shown that corneal changes as a result of eyelid forces occur in the majority of young subjects tested over the course of a normal working day. The average morphology of the palpebral fissure and topography of the central and peripheral cornea has also been defined in detail for a large population of young subjects. Significant associations were found between corneal astigmatism and the morphology of the palpebral fissure. Whilst these results support a model of corneal astigmatism development based on eyelid morphology, they do not prove causation. Further research including measurement of eyelid pressure and corneal rigidity may aid in understanding the exact aetiology of the magnitude and axis of corneal astigmatism.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 6 uppsatser.