Optical coherence tomography (OCT) is an imaging modality that allows for non-invasive imaging of the morphology of biological tissue with micrometer scale resolution at imaging depths of 1-2mm below the tissue surface. During these few years, OCT has become a useful clinical and research tool for imaging of the ocular surface. In addition to the mostly used application for observing the optic disc and retinal choroidial structure, the usage in the anterior segment, especially cornea, was also widely developed. An anterior segment OCT (Visante; Carl Zeiss Meditec, Dublin, CA), a time-domain OCT, is a commercial available OCT designed for especially for anterior segment. This OCT instrument has been used widely in LASIK, different lamellar keratoplasties, keratoconus screening and evaluation of corneal diseases in different layers. However, its limited resolution does not allow for the observation of the epithelial layer on the ocular surface. Spectral domain OCT with a corneal module can provide much better resolution than time domain OCT for the observation of epithelial layer on ocular surface. It has been used recently to evaluate the corneal epithelial layer with reliable results. In this study, we use a fourier-domain optical coherence tomography OCT (RTvue, Optovue Inc., Fremont, CA), with a corneal-anterior module long lens adapter with low magnification, to observe the limbal structure (POV). The purpose of the study is to assess the role of aging and regions on the limbus.