8.5.2: investigate technologies that are used to assist with the effects of visual disorders (spectacles and laser surgery)
Spectacles
Laser eye surgery
frames that hold corrective lenses
clear hard plastic
shape determined by visual disorder
Mysopia corrected by concave lenses
thicker on outside and thinner towards the centre
bend light outwards
causing them to diverge before they reach
causing the image to reach the retina rather then fall in front
hyperopia corrected by convex lenses
thicker towards the centre and thinner at the edges
bends light inwards
causing converging before the light reaches the eye
reaching the retina rather than falling behind it shortening focal point
lasers used to change curvature of cornea
enabling light to enter eye correctly refracting it
forming focused image on the retina
LASIK surgery most common type
Laser-assisted in situ keratomileusis
people under 20 are not suitable for this technology as eyes are not developed completely
not used for extreme cases
involves the use of microkertaone
lifts cornea tissue
so that a laser can be used to modify and correct the refractive index or power.
laser can remove tissue
reducing curvature of cornea lowering refractive power