Accomodation Flashcards
What is accomodation
A dynamic change in the power of the eye. It provides the ability to change the point of focus of the eye from distant to near objects
T/F The optical power of the lens decreases with accomodation.
False. It increases, the focal length decreases
How is accomodation measured
in diopters (1/m)
How is increased optical power achieved
Due to increased surface curvature and increased thickness of the lens
How do myopes use accomodation
Myopes can focus clearly on objects closer than optical infinity without accomodation
How do hyperopes accomodate
They focus on objects through an accomodative increase or with + powered lenses. They accomodate for near and far
The optical power of the cornea is attributable to what combination?
The positive radius curvature and higher refractive index than the surrounding air
T/F The posterior lens surface does not move with accomodation
False! The posterior lens surface increases in curvature and moves backward with accomodation
What is depth of field
The range at which the target can be moved forward or backward and still maintain clarity
What is depth of focus
The focusing error that can be tolerated inside the eye without an appreciable decrease in acuity or change in blur or focus of the image on the retina.
What is depth of focus dependent on
Pupil size! Larger depth of focus = small pupil
Smaller depth of focus = large pupil
does pupil size increase or decease with age
Decrease. This helps with reading and decreased need for add in presbyopic correction
What happens with accomodation at rest
The eye is focused for distance, and the zonules apply an outward tension on the lens. This hold the lens in a flattened and unaccomadated state
What refers to tonic (residual) accommodation
At rest, the eyes have some residual or resting level of accomodation amounting to approximately 1.5 diopters
What does the Accomodative Triad refer to
- Pupil constricts
- The eyes converge
- The eyes accommodate
Accomodation is a binocular process
TRUE
What does a minus lens do to your eye (blur-driven accomodation)
Decreasing the power of the eye, the eyes accomodate to overome the defocus. Keep adding minus lenses until you can no longer see the object. Object gets minified
T/F Accomodation is blur driven
True
What happens when you place a base out prism in front of the eyes
The pupils constrict and the eyes converge; accomodation occurs
how can accomodation be induced
Through pharmacologic stimulation. Topical application of muscarinic cholingergic agonist (pilocarpine) to the eye results in stimulation of the ciliary muscle
T/F pupil constriction occurs with pharmacologic stimulation, but convergence does not
TRUE
What is accomodative esotropia
Often occurs in uncorrected hyperopes as a consequence of needing to accommodate to even see distant objects in focus.
How can accomodation be pharmacologically blocked?
Atropine, cycloentolate, tropicamide. Competitively bind to the same muscarinic receptors as the agonists and prevent agonist binding and block accomodation
What refers to blockage of accomodation
cylcoplegia
