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