Orthotics Flashcards
Binocular vision
Brains ability to perceive an image with each eye as a single image
Fusion
2 images of an object make one
Steropsis
Fused images seen in depth
Manifest squint
Obvious deviation of eye, visual axis not normally aligned
How to detect manifest squint
Cover/uncover test
Suffix manifest squint
-tropia
Latent squint
Tendency for eyes to deviate
But normally aligned
Suffix latent squint
-phoria
How to detect latent squints
Alternate cover test
Concomitant squint
Non-paralytic
Squint remains same size and direction in all positions of gaze
Incomitant squint
Paralytic squint
Changes is different positions of gaze
Due to underreaction of at least 1 extraoccular mm
When are incomitant’s squints most obvious
When gaze directed towards affected mm
Who gets diplopia + squint
If squint has developed after visual development (>7)
Who gets diplopia + suppression
<7
Amblyopia
Lazy eye
Causes amblyopia (3)
Stimulus deprivation - cataract
Strabismus
Anisometropic
What is strabismus
The eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate.
Anisometropia
when your eyes have varying refractive powers, which can cause your eyes to focus unevenly
Mx ambylopia
Occlusion good eye w/ patch 6hrs day
Correction of squint
What % babies at birth have concomitant squints
73%
What conditions are concomitant squints associated with (4)
Idiopathic
Anisometropia
Severe hypermetropia/myopia
Retinoblastoma
PS concomitant squint
NO diplopia
Extraocc mm normal
Both eyes have full movement when tested separately
2 types of concomitant squint
Convergent/esotropia
Divergent exotropia
Assessment Concomitant squint
Cover test (manifest) Alt cover test (latent) Corneal reflections VA (rule out amblyopia) Fundoscopy (rule out retinoblastoma)
What type of lenses do you need to correct a convergent squint?
convex
What type of lenses do you need to correct a divergent squint
Concave
Mx concomitant squint
Correct refractive error w/ lens
Eeye patching
Eye exercising
Surgery if severe
What are incomitant squints usually due to?
CN palsies
Features CN III palsies
Eyes - down and out
Complete ptosis
Efferent pupillary defect
Features CN IV palsies
Eyes - upward at rest + adduction
Pt complains of tilt image
Diplopia on looking down
Features CN VI palises
Can’t abduct affected eye
May drift medially
Which nn palsies is Herpes zoster ohthalmicum related to
IV
III
Which nn palsy is demyelination related to?
VI
If a palsy is CN III and pupil sparing, what is it likely to be related to
Microvascular causes - DM/HTN
Mx diplopia is incomitant squint
Prisms
Occlusions #
Surgery if diplopia stable
Numbers - emmetorpia
Cornea - 40D
Lens - 20D
Axial length - 22.22mm
WHat is axial length
Distance between the anterior surface of the cornea and the fovea
Myopia
Short sighted
What happens to light in myopia
Focused in front of retina
Axial length and refractive power in myopia
AL -> 22.22
RP >60D
What conditions is myopia associated with? (4)
Cataracts
POAG
PVD and retinal detachment
Keratoconus
Mx myopia
Concave lens
Hypermetropia
Long sighted
What happens to light in hypermetropia
Focused behind the retina
Axial length and refractive power - hypermetropia
AL < 22.22
RP <60
What conditions is hypermetropia associated with? (3)
AACG
Squint
Amblyopia
Mx hypermetropia
Convex lens
+ves soft contact lenses (4)
Flexible/comfortable
Larger d - secure fit
Safer for spots
Can be used for extended wear
-ves soft contact lenses (4)
Split easily
Depositions from tear
> expensive
dehydrates
+ves rigid gas permeable lenses
Duration = good for all day wear
Smaller d = reduce risk hypoxia
Smoother ocular surface
Easier to clean
-ves rigid gas permeable lens
Poor initial comfort
Prone to fall out of eye
