SSS week 11

Myopia

short sightedness

• condition in which an image of a distant object becomes focused in front of retina, either bc eyeball axis is too long or because refractive power of object is too strong

• corrected by concave (minus) lenses

Hyperopia

• far sightedness

• refractive error in which image of a distant object becomes focused behidn retina, either bc eyeball axis is too short or bc refractive power is too weak

• corrected by convex (plus) lenses

Astigmatism

• eye condition that exists when surface of cornea or crystalline lens is irregularly shaped

• corrected by toric lenses (football shaped)

Presbyopia

age-related loss of near vision, typicaly starting around 40, caused by eye’s lens becoming less flexible and losing its ability to focus on close objects

• age related loss of accomodation

• corrected by convex (plus) lenses

Symptoms in an eye exam

1. abnormal vision

2. abnormal sensation eg. discomfort

3. altered appearance

types fo abnormal vision

1. reduced

• central

• peripheral

• impaired night or colour vision

onset

if sudden —> vascular

or gradual

.

2. floaters

• haemorrhage

• inflammation

• vitreous degeneration

• muscae volitantes

.

3. flashers

• irritative stimulation of retinal or visual pathway

can be unilateral —> retinal deatchment?

bilateral —> migraine/basilar artery insufficiency

.

4. haloes - rainbow coloured rings around lights due to corneal oedema or increased intraocular pressure

5. metamorphopsia / micropsia

• apparent distortion of straight lines/minification of objects due to retinal oedema or macular degeneration

6. diplola

binocular 

• resolves when either eye is covered, due to misalignment of visual axes

  

monocular

persists when unaffected eye is covered

• caused by optical/intraocular problems (not alignment)

typical causes

• cataracts, corneal irregularity/scar, refractive error, dry eye, intraocular foreign body

Abnormal sensation types

1. foreign body sensation

• subjective localisation unreliable

• causes include: trichiasis, entropion, conjunctivitis, dry eye

• local anaesthetic relieves

2. photophobia

• iritis

• keratitis

• cycloplegic drops relieves

3. severe deep pain

• acute angle closure glaucoma

• zoster/shingles

4. asthenopia (eye strain)

• occurs after intensive use of eyes

• due to

• inadequately corrected refractive error

• heterophoria

5. watery eyes/ discharge

• overproduction (due to ocular irritation or FB)

• faulty drainage

• instability (dry eyes often blepharitis)

Types of altered appearance

What are the 3 mechanisms of Cellulitis

• spread from local infection like sinusitis

• skin disruption

• haematogenous spread (common under age 2)

GAS/staph/s.pneumo

Periorbital vs orbital cellulitis

Red flags concerning for orbital cellulitis

• painful or restricted eye movements

• visual impairment: reduced acuity, relative afferent pupil defect, diplopia

• proptosis

• severe headache or other features of intracranial involvement

Cellulitis characteristics