The cornea, conjunctiva, and intervening transition area known as the limbus comprise the tissue at the ocular surface. The cornea functions as a protective membrane and a “window” through which light rays pass to the retina. In the ideal refractive state, emmetropia, an image is focused directly on the retina, resulting in the perception of a sharp image in a healthy visual system. In myopia (nearsightedness), the image appears focused anterior to the retina, producing a sharp image at near and a blurred image at distance. The inverse is true in hypermetropia (farsightedness), where the image is projected posterior to the retina, producing a blurred image at near and a sharper image at distance. Astigmatism (cylindrical error) is the result of two different refractive powers between two perpendicular meridians. As an object is brought nearer to the eye, focus is maintained by an increase in the power of lens of the eye; this is accommodation. The ability to accommodate decreases with age (presbyopia).

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Financial support for the publication of this thesis was provided by the following: Prof.dr. Henkes Stichting Alcon Nederland B.V. Allergan BV Bausch en Lomb Christelijke Stichting tot Praktisch Hulpbetoon Erasmus Universiteit Rotterdam J.E. Jurriaanse stichting Laméris Ootech BV Landelijke Stichting Blindenbelangen Low Vision/ERGRA MSD BV Oculenti Contactlenspraktijken Pfizer BV Rockmed Simovision Stichting tot Verbetering van het Lot der Blinden in Nederland Thea Pharma
G. van Rij (Gabriel)
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam

Saelens, I. (2011, November 2). Corneal transplantations and intracorneal implants. Retrieved from