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
What should be done with a patient experiencing a loss in visual fields?
- Semi-urgent referral to an opthalmologist
- If patient has pain, or acute loss of vision, they should be seen THAT DAY
- If unsure, discuss with on-call opthalmologist
How can you work out which eye you are looking at on funduscopy?
Look for the optic nerve
- The optic nerve head is in the nasal part of the fundus
- If on the right, is the right eye
- If on the left, is the left eye
How should we assess the optic disc?
Optic disc: 3 cs- - Cup - Colour - Contour
What are the signs of primary open angle glaucoma?
POAG signs:
- Raised intraocular pressire
- Optic nerve damage (cupping)
- Visual field defects
What should be done following a diagnosis of primary open angle glaucoma?
- Counsel the patient
- Advise the patient not to drive
- Advise the patient to continue taking their eye drops
- Suggest the patient inform the DVLA, and their family (genetic component)
What is the most common type of glaucoma?
Primary open angle glaucoma
What are the risk factors for glaucoma?
- Diabetes
- Short-sightedness
- Race (Afro-Caribbean)
- Family history
- Wearing a tight collar and tie
- Having a thin cornea
- Old age
What is the normal range for intra-ocular pressure?
Normal range is 10-20mmHg
How does aqueous fluid affect intra-ocular pressure?
- Aqueous fluid, if overproduced, can increase pressure
- Aqueous fluid drains from the canal of schelmm, if this becomes blocked the pressure can increase
What is a Goldmann aplannation tonometer used for?
Checking the intra-ocular pressure
Which medications can lower intra-ocular pressure?
- Beta blockers
- Carbonic annhydrase inhibitors
- Pilocarpine
- Prostaglandin analogues
What is ‘wet’ ARMD?
Wet ARMD:
- Develops secondary to dry ARMD
- Occurs when fluid/blood develops in the retina, often due to neovascularisation
- This causes sudden loss of central vision and distortion
- Requires an urgent referral
- Treatment are intra-vitral anti VEG-F injections (counters formation of new blood vessels)
