The Optics of the Eye Flashcards
What is accommodation of the eye?
When your eye focuses the lens system in the eye.
What does accommodation of the eye involve?
the change in the shape of the lens.
Why does accommodation of the eye occur?
In order to see close objects.
What does it mean when lens become taut?
The lens flattens and its refractive power decreases.
What occurs when in accommodating for distant vision?
Ciliary muscles relax and the zonule of Zinn becomes taut.
What occurs when accommodating for near vision?
ciliary muscles contract and Zonule fibers relax.
What occurs when Zonule fibers relax?
it causes the lens curvature to increases > leading to refractive power increasing.
Parasympathetic activation stimulates the contraction of what causing what?
of the ciliary muscles causing the relaxation of the Zonule of Zinn.
When lens become more convex and increases its refractive power what just occurred?
The Zonule of Zinn is relaxed.
What is presbyopia?
The inability of the lens to change its shape during accommodation.
What reduces with age?
The capability or power of accommodation.
Why does the capability of accommodation reduce with age?
lens become thicker, larger, and less elastic due to denaturation of lens proteins.
In children the refractive power of the lens can do what?
increase voluntarily by 14 diopters.
By age 45-50 the accommodation capabilities do what and by how much?
Reduce from 14 to 2 diopters.
A middle aged person has a refractive lens power of what?
2 diopters.
By age 70 accommodation capabilities is what?
0
Eyes are permanently focused at a constant distance at what age and what do they need?
age 70 and they need bifocals.
What is the function of the iris?
The iris regulates the amount of light entering the eye.
What occurs in darkness what happens to the iris?
more light enters.
What occurs in a bright environment to the iris?
the less light enters the eye.
What are pigmented in the iris?
The stroma and epithelial cells.
What forms the boundary of the pupil?
The medial or inner aspect of the iris.
Define the pupillary zone?
The medial or inner aspect of the iris forms the boundary of the pupil.
The lateral or outer segment of the iris is attached to the what?
The ciliary body and sclera.
What does the pupillary region contain?
The sphincter muscles of the iris.
What does the ciliary region contain?
The radial muscles of the iris.
What is the sphincter muscle also known as?
pupillary sphincter, pupillary constrictor, or circular muscle of iris.
What is the radial muscle of the iris is also known as?
pupil dilator muscle or pupillary dilator.