Unit 2 - Communication and examination skills Flashcards
Should contrast sensitivity be measured monocularly or binocularly?
monocularly, allowing 20 secs per letter
What is the resolution limit of the eye?
30 secs - 1 minute or arc
What are the 4 common causes of acquired visual field defects?
- Diabetes
- MS
- Chemical exposure
- Drug toxicity
Which colour vision tests are better for acquired pathology?
Farnsworth- Munsell and d15.
What illumination should colour vision testing be undertaken under?
Standard illuminant C
Which test can be used to assess integrity of the optic nerve?
Red desaturation test
What are the 4 commonest med ret causes of RAPD?
- AION
- Retinal disease
- Retinal detachment
- CMV retinitis
What are the 3 reasons why we perform visual field testing?
To monitor progression
Evaluate treatment of disease eg PRP
To correlate functional and structural changes in the retina
What is microperimetry useful for?
Visual rehab, to identify area of best vision Stargadt’s disease where conventional testing may not find defect.
Why do we need to dilate?
To improve steroscopic resolution Increase field of view
How much retinal pathology is missed in undilated pupils?
40%
What 5 reasons are there not to dilate?
- History of CAG
- VH of grade 1 or less
- History of penetrating injury
- Iris clip lens
- If patient is driving but if pathology is critical dilate anyway
What should be conducted prior to dilation?
- A/C depth
- VH
- Normal history and symptoms especially haloes around light or brow ache in low light levels
What does phenylephrine do?
Stimulates dilator muscle
What does tropicamide do?
Restricts action of sphincter
When should you be careful using phenlephrine?
- Overactive thyroid
- Diabetes
- High BP
- Coronary artery disease
- Enlarged prostate
What pressure rise would cause you to refer a patient following dilation?
5mmHg
What sort of image does a Volk lens give you?
A virtual, inverted and reversed image.
What sort of image does a headset bio give you?
A laterally, inverted real image.
What FOV do you get with a 90D?
94
What magnification do you get with a 90D?
0.75X
How much more likely is a patient with learning difficulties to have a sight problem?
10x
How common is Charles Bonnet syndrome?
20-35% of patients
How can you relieve Charles Bonnet syndrome?
- Eye movements
- Blinking
- In extreme cases anti-epileptic meds may help
