other visual defects Flashcards
what is emmetropia
where there is no refractive error - light is focused onto the retina
what is ametropia
light is focused before or after the retina
what is anisometropia
where there is a significant difference between the refractive error of the left and right eye
another name for myopia
short sightedness
what causes myopia
abnormally increased axial length of the eye or increased refraction
pathophysiology of myopia
light focuses before the retina
management of myopia
glasses with concave (negative) lenses
complications of myopia (2)
retinal detachment
open-angle glaucoma
another name for hypermetropia
far sightedness
pathophysiology of hypermetropia
abnormally decreased axial length of the eye means light focuses behind the retina
management of hypermetropia
glasses with convex (positive) lenses
complication of hypermetropia
closed-angle glaucoma
what is an astigmatism
irregular corneal curvature
pathophysiology of astigmatism
eye has unequal refractive powers at different meridians of curvature
management of astigmatism
cylindrical lenses
what is presbyopia
age-related generation of structures responsible for accommodation of the lens
management of presbyopia
reading glasses
what is another name for strabismus
squint
what is strabismus
where the eyes don’t align with each other when focusing on an object
when does strabismus usually start
childhood
name 3 risk factors for strabismus
premature birth
cerebral palsy
family history
what can cause strabismus (5)
muscle dysfunction
farsightedness
problems in the brain
trauma
infection
clinical sign of strabismus
corneal reflections are asymmetrical
investigation for strabismus
cover test
outward movement of the eye in cover test
esotropia
inward movement of eye in cover test
exotropia
downward movement of eye in cover test
hypertropia
upward movement of eye in cover test
hypotropia
complication of uncorrected squint during childhood
lazy eye
what is cataracts
opacifications within the lens
name some risk factors for cataracts
cumulative UVB damage
hypertension
smoking
steroids
diabetes
genetic predisposition
post operative / trauma
clinical presentation of cataracts
gradual visual loss - hazy/blurred
glare
clinical sign of cataracts
loss of fundal reflex
management of cataracts
surgical removal with intra-ocular lens implant
most common ages for males to present with ocular trauma
25-34
mechanism of injury of ocular trauma in males
assault or machinery injuries
most common age for females to present with ocular trauma
> 60
mechanism of injury of ocular trauma in females
falls at home
what is a blowout fracture
when there is a fracture of one of the walls of the orbit but the orbital rim remains intact
what usually causes a blowout fracture
direct blow to the central orbit from a fist or a ball
what is the most common type of blowout fracture
inferior blowout
mechanism of clinical presentation of an inferior blowout fracture
orbital fat prolapses into the maxillary sinus and may be joined by prolapse of the inferior rectus muscle, resulting in diplopia
what is subconjunctival haemorrhage
when one of the small blood vessels within the conjunctiva ruptures and release blood into the space between the sclera and the conjunctiva
when does subconjunctival haemorrhage usually appear
strenuous activity such as heavy coughing, weight lifting or straining when constipated
how long does it take for subconjunctival haemorrhage to resolve
around 2 weeks
what is a globe rupture
rupture of the sclera usually due to a direct penetrating injury
what is hypahemia
blood in the anterior chamber
state 4 site-threatening complications of trauma
- tearing of intra-ocular structures
- dislocated lens
- retinal detachment
- commotio retinae
what is another name for commotio retinae
bruised retina
mechanism of injury of a corneal abrasion
poking, foreign bodies, brushing against the eye
investigations for corneal abrasions
visual acuity
fluorescein staining
what must always be done with potential intraocular foreign bodies
x-ray
state 4 signs of a penetrating foreign body
- irregular pupil
- shallow anterior chamber
- localised cataract
- gross inflammation
pathophysiology of sympathetic ophthalmia (2)
- Penetrating injury to one eye results in exposure of intra-ocular antigens → auto-immune reaction in both eyes
- Inflammation in both eyes may lead to bilateral blindness (from a unilateral injury)
what kind of chemical burn is worse
alkaline
management of a chemical burn to the eye
irrigate - minimum 2L saline, or until pH normal
name 3 complications of chemical burns to the eye
limbal ischaemia
corneal scarring
corneal vascularisation
what characterises glaucoma
progressive optic neuropathy resulting in characteristic field defects
name the only modifiable risk factor for glaucoma
raised intraocular pressure
when does glaucoma occur
when there is a blockage in the drainage of aqueous humour through the trabecular meshwork
what is the most common type of glaucoma
chronic open-angle
name some risk factors for chronic open-angle glaucoma
hypertension, DM, corticosteroids
myopia
Afro-Caribbean ethnicity
increasing age
what happens in chronic open-angle glaucoma
impaired aqueous humor drainage through the trabecular meshwork, causing elevated intraocular pressure
this damages the optic nerve and causes peripheral visual field loss
clinical presentation of chronic open-angle glaucoma
usually asymptomatic - diagnosed through screening tests
fundoscopy of a patient with glaucoma
optic disc cupping
pale optic disc
first line management of chronic open-angle glaucoma
prostaglandin analogues
name 2 second line drugs used in management of chronic open-angle glaucoma
β blockers, carbonic anhydrase inhibitors
what happens in closed angle glaucoma
blockage or narrowing of the drainage angle formed by the cornea and the iris, resulting in a sudden increase in intraocular pressure
risk factors for closed angle glaucoma
hyperopia
Asian or Inuit
pupillary dilatation
symptoms of angle-closure glaucoma (4)
pain
blurred vision
haloes
N+V
clinical signs of closed-angle glaucoma
red eye
hazy cornea
mid-dilated pupil
definitive management of closed-angle glaucoma
laser peripheral iridotomy
pharmacological management of acute presentation of closed-angle glaucoma
pilocarpine 4% drops
