Is my eye okay with OK lens?: comparative in vitro study depicting the effects of Orthokeratology (OK) lens treatment on the physiology of human corneal epithelial cells

Orthokeratology (OK) has gained ground as a therapeutic modality for the correction of refractive error. OK mediates its effect by reshaping the cornea curvature with the use of a specially designed rigid contact lens, in order to correct the focusing of the image onto the retina, thereby implying direct contact with the epithelial layer of the cornea itself. Studies have suggested that this may affect the physiology of the corneal epithelial cells. The majority of orthokeratology research has reported data obtained from clinical studies and animal model studies. The research in this thesis describes the development of an in vitro model to investigate two of the most significant physiochemical changes imposed by OK treatment – elevated pressure and hypoxia, on the physiological responses of cultured human corneal epithelial cells (HCEC). HCECs were adapted and grown in keratinocyte serum-free media to 70 - 80% confluency and then were exposed to hypoxia alone (8% O2), elevated pressure alone (74 cmH2O) or both hypoxia and elevated pressure conditions in an 8-hour incubation period, mimicking average sleep time, in pairwise experiments with controls (normoxia and atmospheric pressure). Spent media was separated from cells, processed and analyzed via nuclear magnetic resonance and YSI glucose/lactate analyzer techniques to estimate consumption and production of various metabolites. Cells were counted then lysed and lysate processed and the proteome analyzed using two-dimensional gel electrophoresis. In all treatments cell growth slowed or was arrested. Proteomic analysis fully identified 5 proteins – annexin A3, pyridoxal kinase, peroxiredoxin-2, stathmin isoform A and heat shock protein 90-α, whose specific levels changed during treatment relative to the control, whilst 34 unidentified proteins were found to be up-regulated in specific expression and 27 unidentified proteins were found to be down-regulated in all treatments. Total up-regulated proteins specific to each treatment are 72,36 and 125 in the hypoxia, pressure and hypoxia-pressure experiments respectively, and the total down-regulated proteins specific to each treatment are 85, 30 and 127 in the hypoxia, pressure and hypoxia-pressure experiments respectively. Metabolite analysis revealed significant changes in glucose and lactate in most experiments, confirmed by both YSI and NMR measurements. In some experiments, significant changes in amino acid metabolism were observed. Data from this newly developed in vitro model suggests that pressure and hypoxia do influence cell physiology and metabolism, though further work is required to completely characterize the model and link with data from clinical and animal studies investigating the effects of OK treatment.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2011

Author dc:creator

• Kumar, Rakish

• Orthokeratology (OK)
• lens treatment
• human corneal epithelial cells
• refractive error
• physiology
• comparative
• in vitro

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/15326

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/51725