Dark adaptometry

Question 1

What is dark adaptation?

Answer 1

the adjustment of the eye to low light intensities, involving reflex dilation of the pupil and activation of rod cells

Question 2

What are the main components of a dark adaptation curve?

Answer 2

cones reach max sensitivity at 5mins
rod adaptation at 30 mins
rod/cone break changes depending on multiple factors

Question 3

What is threshold?

Answer 3

if you go from photopic light to darkness the brightness that a stimulus needs to be before you can see it is the threshold

Question 4

What are the factors affecting dark adaptation?

Answer 4

1. the intensity of the pre-adapting light
2. the length of the pre-adapting light - the longer the exposure the longer time to threshold
3. retinal eccentricity - no break at fovea, break occurs earlier
4. the wavelength of the stimulus - for long wavelength there is no rod cone break

Question 5

What types of illumination saturates rods?

Answer 5

1. greater illumination
2. longer illumination

Question 6

What diseases are affected by dark adaptation?

Answer 6

1. retinitis pigmentosa
2. diabetes
3. AMD
4. congenital stationary night blindness

Question 7

How can the electrical activity of the eye be measured?

Answer 7

by measuring the dipole. Place electrode at cornea and another at the sclera/fornix. One measure signal and noise, the other only noise. subtract one from the other and you reduce the noise and end up with a clean signal

Question 8

Types of ERGs?

Answer 8

Flash and flicker ERGs
Pattern ERGs
Multifocal ERGs