Module 4: Refraction and Ocular Health Flashcards
-case history
-analysis of visual needs/work
-Visual acuity
-depth percenption
-colour vision
-slit lamp/ophthalmoscope/ DFE
-neurological assessment
-glaucoma screening
-refraction
Exams inculde
-light rays bent/focused
-each eye has different refractive ability
-light bending relies on curve or cornea+ lens
-relies on clarity and density of cornea + lens
-ability of retina to recieve and transmit info
- length of eyeball (axial) changes refraction power
Refraction
-length from cornea to posterior pole
- average length 23-25mm (size of quater)
-light should focus at the fovea
Axial length
-cornea
-aqueous humor
-crystalline lens
-vitreous humour
Refracting system
-normal eye
-image lands right on the fovea
-no correction required
Emmetropia
-abnormal eye
- 3 types (myopia/hyperopia/astig)
Ametropia
-out of focus on the retina
-images land behind the retina
-farsightedness (blurry up close)
-cornea too flat/axial too short
-all babies start off this way
-corrected with convex lens (plus power)
-kids can accommodate/focus through
Hyperopia/Hypermetropia
-magnify objects
-objects seem bigger and closer
-px eyes look bigger
-can make “pincushion” effect(lines caved in)
-can alter depth perception
convex lenses
- light focused infront of retina
-near-sightedness (blurry distance)
-physiologic (steep corneas/long axial)
-requires concave lenses (minus power)
-uncommon at birth
Myopia
-minifying
-objects appear smaller/further away
-px eyes look smaller
-can cause “barrel” distortion (lines look round)
Concave lenses
-parallel light rays equally not focused
-cornea unevenly shaped/unsymmetrical
-football shape
-weeakest curve & strongest curve
Astigmatism
-reduction in ability to accommodate upclose
-ciliary muscles cannot buldge the lens enough
-additional plus power
-contact lenses MF/monovision
Presbyopia
-focussing ability
-muscle tight/contracts = bulges= near
-muscle rest/pulls = flat= distance
Accommodation
at least one diopter diference between OS/OD
Anisometropia
unequal size/image on the retina between OS/OD
Aniseikonia
-breakage of blood vessel
-blood pools/covers white sclera
-resolves in a few weeks
Subconjunctival Haemorrhage
-commonly referred “pink eye”
-bactieral
-viral
-allergy
-tocicity
Conjunctivitis
-progressive disease
-thinning cornea
-conical shape
-induces irregular astigmatism
-treated with rigid CL
-possibly hereditary
Keratoconus
-styes
-infection of glands/eyelids
-whitehead-like
Hordeolum
-clear lens becomes cloudy
-capsule holds transparent lens like enevelope
-lens is size of aspirin
-cloudy = light distorted/blocked out
-vision reduced
-lens continually grows/becomes hard
Cataracts
-natural part of aging
Senile Catartacts
-injury/lens is disturbed
- medications/steroids
-chemicals
-UV
-radiation
-smoking
- eye diseases
-diabetes
Traumatic Cataracts
Congenital cataracts
-babies born with them
-colour vision loss
-hazzing
-dark spots in vision
-needing brighter lighting
-glare at night
-near-sighted
-double vision
-better without glasses
-yellow/white pupil
Signs of cataracts