3.3 - Hypermetropia Flashcards
What is hypermetropia
- Second focal point Fe’ falls behind the retina for an unaccommodated eye
- Retinal image is blurred but not always!
Where is sharp image produced in hypermetropia
Behind retina
Ray diagram for hypermetropia
- Parallel converting rays of light coming into reduced eye and converge towards far point
- Sharp image behind retina
- Infinitely distant object forming image at 2nd focal point behind retina
- Virtual point is conjugate with real image - object point conjugate with retina
Where is far point in hypermetropia
Behind eye - virtual point
What happens to axial length in hypermetropia
Too short
What is effect of hypermetropi on vision
Can sometimes look the same, no change in vision with increasing levels of hypermetropia
How does sharp image form at retina in hypermetropia
- Converging light coming into eye converging towards the far point
- The light then converges and forms a sharp image at the retina
What is acommodation
- Ability of eye to increase its optical power with an effort to focus at near objects
- Good ability to focus on objects closer to eye
What happens as you get older
You lose ability to accommodate
Why does lens change in acommodation
Lens changes to increase its dioptric power allowing to focus on near objects
What happens in unacommodated eye
Eye has its weakest/least optical power
What is presbyopia
- As you get older, ability to accommodate decreases
- Its a condition where accomodation is insufficient for near work
At what age does accommodation become negligible
Accommodation declines with age – negligible after 60 years
True or false - myopes can focus on near objects without acommondation
True
What happens if you increase the dioptic power of the eye
It can place the optical image on the retina
It can compensate for the hypermetropia
