Silicone oil (SO) is widely used as the long-term intraocular tamponade in treating various eye diseases such as complicated retinal detachment, proliferative vitreoretinopathy, proliferative diabetic retinopathy, giant retinal tear and ocular trauma. However, its propensity to emulsify is an inherent problem of its long-term use in-vivo. Dispersal of SO into many tiny oil droplets causes numerous complications such as inflammation, glaucoma and reproliferation. It may also be responsible for possible toxicity to both retina and optic nerve. Emulsification is one of the problems associated to the use of SO as a long-term intraocular tamponade. This study focused on the understanding on the physical nature and formation of in-vivo SO emulsion and the development of methods to reduce the complications associated with emulsification of SO by engineering approaches. A stepper motor driven mechanical platform was built to study the fluid flow of SO within an eye model chamber during eye-like movements and a quantitative method was established to study SO emulsification, both in-vivo and in-vitro. This method was used to compare the relative resistance of different SO against emulsification. In the last part of the thesis a novel rinse was proposed which aimed at removing the emulsified SO droplets in-vivo in an effective way. In the dynamic eye model experiment, both the increase in shear viscosity of SO and the extent of SO fill had an effect in reducing the shear. These effects were small compared to the effect of indents at reducing shear rate during eye-like movements. When SO emulsions from patients were analyzed it was found that over 90% of the emulsified droplets were outside the observable range under slit-lamp biomicroscopy. When the emulsification resistance of SO was tested using the quantitative method the result confirmed that SO with high-molecular-weight component (HMWC) was more emulsification resistant than SO with the same shear viscosity. The addition of HMWC increases the elasticity and thus increasing its resistance against emulsification. A novel rinse was also proposed to remove the emulsified droplets using physical phenomenon of double emulsification. To conclude, this study improved the understanding of the formation of SO emulsification. The clinical observable emulsified droplets are probably in all cases that was just the tip of the iceberg. Three practical suggestions were made: Firstly, the use of SO and encircling scleral buckling procedure in combination might reduce the shear rate. Secondly, the use of HMWC can reduce emulsification. Lastly, there may be a role in rinsing out the emulsified droplets using the proposed novel solution. The novel solution is going to fully developed and commercialized in the near future. / published_or_final_version / Ophthalmology / Doctoral / Doctor of Philosophy

However, this is by no means the limit. More knowledge on macular hole is needed. Continuous research in Hong Kong and other scientific communities are indispensable. A multicentre, multi-surgeon study should be contemplated and carried out prior to the generalization or application of this technique to all patients. / Over the last few years, we have collected essential clinical and laboratory data on indocyanine green (ICG) assisted internal limiting membrane (ILM) peeling in macular hole surgery in Hong Kong. With the intraoperative use of a small volume and low concentration of ICG, we have shown the usefulness and safety of this technique in improving the surgical outcomes, both antomically and functionally, in patients with macular hole of idiopathic type or in severely myopic eyes. Our randomized controlled trial demonstrated higher anatomical closure rate and better visual outcome with ICG assisted ILM peeling compared with no ILM peeling in primary idiopathic macular hole surgery. Our case-control study also demonstrated that ICG assisted ILM removal in macular hole surgery of severely myopic eyes gives promising anatomical closure rate and visual outcome comparable to emmetropic ones. / Kwok Kwan-ho. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (M.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 201-214). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.