3.3- Hypermetropia Flashcards
1
Q
What does hypermetropia mean?
A
- Means beyond (measure of) the eye
- Second focal point Fe’ falls behind the retina for an unaccounted eye
- Retinal image is blurred but not always.
2
Q
Where is the far point in hypermetropia?
A
Far point mR is behind the eye- virtual point- have converging light into eye and towards far point and then forms a sharp point onto retina
-virtual point that is conjugate with a real image on the retina
3
Q
What are the effects of different levels of hypermetropia on vision?
A
-Test chart can look the same if increase hypermetropia - no change in vision compared to myopia having loss of vision
4
Q
Why doesn’t vision change for increasing levels of hypermetropia?
A
- due to accommodation
- lens shape from being accommodated on one side and unaccomodated on the other side which increases the dioptric power of the eye
- Hence have good ability to focus on near objects
- Unaccomodated - eye has its weakest optical power
- Accomodated - the ability of eye to increase its optical power with an effort to focus at near objects
5
Q
What is presbyopia?
A
reduction in accommodation with age- negligible after 60 years
- Natural
- defintion: condition where accommodation is insufficient for near work
6
Q
How do hypermtropes accommodate?
A
- Increase in dioptric power of the eye place the optical image/focus image on the retina from behind retina.
- In young subjects, accommodation can compensate for hypermetropia but there are consequences e.g squint
- Accommodation can explain results when refracting a hypermetrope