Myopia is a common ocular condition worldwide and the mechanism of myopia is still not clear. A number of animal models of myopia and refractive error development have been proposed. The fact that form deprivation myopia could be induced in tilapia fish, as shown previously in my research, suggests the possibility that tilapia could be a new animal model for myopia research. In the first part of this thesis the tilapia model was perfected and then, based on this model, the effect of systemic hormones (thyroid hormones) associated with eye and body development was investigated during refractive error development. Lastly, the physiological and morphological changes on the retina were further studied with optical coherence tomography (OCT).
In these experiments, significant amounts of myopia, and hyperopia were induced within two weeks using goggles with lens inserts as in other higher vertebrate animal models, e.g. chicks. The results from form deprivation treatment also show that the sensitivity of tilapia eyes may be an age related effect during the emmetropization process. The larger the fish, the less hyperopic the fish eye, though the small eye artefact may be a factor. The susceptibility of the refractive development of the eye to the visual environment may be also linked to plasma hormone levels. It was found that induced refractive errors could be shifted in the hyperopic direction with high levels of thyroid hormones. Also, after 2 weeks of treatment with negative or positive lens/goggles, the tilapia retina becomes thinner or thicker, respectively. When the goggles are removed, the thickness of the retina changes within hours and gradually returns to normal. However, the circadian retinomotor movement is a complicating factor since it affects the retinal thickness measurement with OCT at some time points.
In conclusion, tilapia represent a good lower vertebrate model for myopia research, suggesting a universal mechanism of myopia development, which may involve systemic hormones and immediate, short term retinal responses.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OWTU.10012/4178 |
| Date | January 2008 |
| Creators | Shen, Wei |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
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