Gradual loss of vision Flashcards
What questions should be asked as part of an opthalmic history?
Important aspects of history:
- Pain or redness
- Both eyes affected?
- Changes in visual fields, or just central sight?
- Do they wear glasses, and are their glasses up to date with their prescription?
- Previous eye problems/surgery (cataract etc)
- Family history of visual pathology/poor sight
Consider medical history:
- Diabetes
- Hypertension
- Glaucoma
- Medication and allergies
What is included in the examination of the eye?
- Visual acuity - distance (Snellen) and near
- Colour vision
- Visual fields
- Eye movements
- Fundoscopy
How do you determine visual acuity?
Using a Snellen chart for distance; 6ft away.
The smallest row of letters they can see (fewer than 2 errors) is the second number, where visual acuity is described as (6/x)
Which ADLs are affected if central visual acuity is reduced?
Central visual acuity:
- Struggle reading
- Struggle watching TV
- Struggle with other small hand-to-hand tasks
- Driving
What is used to dilate eyes?
Before fundoscopy:
- Use 1% tropicamide eye drops to dilate the eyes
Do not use dilating drops if a patient has suspected or confirmed narrow angle glaucoma
(Painful sore red eye)
What are the different eye dilating drops available?
- Tropicamide 1%
- Cyclopentolate 1%
- Phenylephrine 1%
What is the mechanism of action of tropicamide?
Tropicamide:
- Binds to and blocks receptors (muscarinic M4) in the muscles of the eye
- Blocks responses of iris sphincter muscle
- Blocks ciliary muscles (less cholinergic stimulation)
- This results in dilation of the pupil and paralysis of the ciliary muscle
What is the mechanism of action of cyclopentolate?
Cyclopentolate:
- Anticholinergic drug, blocs receptors in the muscles of eye iris and ciliary muscle
- This prevents stimulation via acetylcholine
- This results in dilation of the pupil and paralysis of the ciliary muscle
What is the mechanism of action of phenylephrine on the eye?
Phenylephrine:
- Acts directly on alpha-receptors on the eye
- This causes contraction of the dilator muscle
- This also causes constriction of the arterioles in the conjunctiva
- This results in dilation of the pupil
What is seen on fundoscopy in age-related macular degeneration?
Age-related macular degeneration:
- Drusen seen in the macula
- Theses are yellow deposits under the retina, made up of lipids
- Drusen do not cause ARMD but the presence of them increases the risk of developing ARMD
- Drusen are a defining feature of ARMD.
What is age-related macular degeneration?
ARMD:
- Common cause of vision loss in the older population
- 85% of cases see ‘dry’ macular changes
Dry ARMD:
- Gradual loss of central vision (due to effects in macular region)
- Affected individuals describe difficulty reading and seeing fine details, such as the faces of people
- Peripheral vision is spared
Risk factors:
- Female gender
- Smoking
- Hypertension
- Previous cataract surgery
Which analgesics can affect pupil size?
- Morphine (opioid - constricts pupils)
- Hyoscine (anticholinergic - dilates pupils)
If a patient has vague visual symptoms, which examination should be considered?
Visual fields assessment
What is a common cause of homonymous hemianopia?
Stroke in the occipital lobe
How do you interpret visual fields?
- Black dots (filled in)= Patient cannot see these areas
- Black circles = patient can see these spots
- Triangles = Normal, physiological blind spots
