Glossary of Terms
Photo: Photo means light and includes the whole electromagnetic spectrum. The Excimer laser is Ultraviolet and the Femtosesond laser Infrared
Refractive: As light meets a more dense medium it slows and bends. Curved surfaces bend the light to a point of focus, the shape of the surface or curvature determines the point of focus.
Keratectomy/Keratomileusis: Kera = cornea, ectomy = to remove, mileusis = to dissolve, ie corneal tissue is removed/dissolved precisely by the laser.
Myopia: Light is refracted to focus in front of the retina, distant objects are blurred, but near objects in focus hence near sightedness
Hyperopia: Light is focused behind the retina, younger persons can still focus distant objects clearly hence far sighted.
Astigmatism: The focusing surfaces have different curvatures in opposite meridians and hence different focal points (think of the side of a rugby ball)
Accommodation: The ciliary muscle in the eye acts on the lens to change its shape and focus from to and from distance to near.
Presbyopia: With age the lens hardens, it can no longer change shape and focus. Typically reading glasses are needed from late 40’s
Cataract: Clouding and milkiness of the lens with age causing loss of vision corrected by surgery
Intraocular Lens (IOL): when the cataract or lens is removed the focus is restored by inserting a new artificial lens in the eye.
Keratoconus: The cornea is weakened and stretches centrally going out of shape and focus (keratoconus is usually a contraindication to Laser Refractive surgery)
Cross-Linking: Treatment of the cornea with a combination of Vit A and UV light to strengthen the cornea, typically used in keratoconus in conjunction with Keratarings +/- PRK