Anatomy & Physiology Chp. 1 Flashcards
Accommodation
Focusing of the eye on a near object through relaxation of the ciliary muscle and thickening of the crystalline lens.
Amblyopia
The loss of vision without any apparent disease of the eye. Also known as lazy eye.
Ametropia
A refractive error in which the eye, in a state of rest, does not focus the image of an object upon the retina; includes hyperopia, myopia, and astigmatism.
Aniseikonia
A condition in which the ocular image of an object as seen by one eye differs so much in size or shape from that seen by the other eye that the two images cannot be fused into a single impression.
Anisometropia
A condition in which the refractive error of one eye significantly differs from that of the other; each eye must have the same sign, i.e. both eyes are myopic or hyperopic.
Antimetropia
The refractive condition whereby the signs in each eye are opposite; one eye is hyperopic while the other is myopic.
Aphakia
An absence of the crystalline lens. Usually due to surgical removal, perforating wound or ulcer, or congenital anomaly.
Aqueous Humor
The clear watery fluid that fills the anterior and posterior chambers within the front part of the eye.
What is the Aqueous Humor responsible for?
The Aqueous Humor is responsible for keeping the Cornea moist as well as maintaining the inter ocular pressure in the eye.
What is the Index of refraction of the Aqueous Humor?
1.33
Astigmatism
A refractive error that prevents the light rays from coming to a single point of focus on the retina because of different degrees of refraction in the various meridians of the eye.
Cataract
A condition in which the Crystalline lens of the eye, or its capsule, or both, become opaque/cloudy, with consequent loss of visual acuity.
Choroid
The vascular intermediate coat that furnishes nourishment to other parts of the eyeball.
Ciliary Body
That portion of the vascular coat between the Iris and the choroid. It consists of the ciliary processes and the ciliary muscle.
Compound Hyperopic Astigmatism
The refractive error which results in two points of focus falling behind the retina.
Compound Myopic Astigmatism
The refractive error which results in two points of focus falling in front of the retina.
Cornea
The clear transparent portion of the outer coat of the eyeball forming the covering of the Aqueous Chamber. Also known as “the window” of the eye.
What are the 5 layers of the Cornea
Epithelium, Bowman’s Membrane, Stroma, Descemet’s Membrane, and the Endothelium.
What is the Index of Refraction of the Cornea?
1.37
What is so special about the Epithelium?
It is the most regenerative part of the body. Mild scratches/abrasions heal within about 24 hours.
What percentage of the Cornea does the Stroma take up?
About 90%
How thick is the Cornea?
About 0.5mm thick.
When is the physiology of the Cornea most important?
When fitting contacts.
What is the refractive power of the Cornea?
About 43 Diaopters
Crystalline Lens
A transparent colorless bosy suspended in the front part of the eyeball, between the Aqueous and Vitreous Humor, the function of which is to bring the rays of light to focus on the Retina.
What is the refractive power of the Crystalline Lens?
About 17-20 Diaopters.
What is the Index of Refraction of the Crystalline Lens?
1.42
Diplopia
The seeing of one object as two.
Emmetropia
The refractive condition of the normal eye, when the eye is at rest, the image of distant objects is brought to a focus on the retina.
Fovea
A small depression in the retina at the back of the eye; the part of the Macula adapted for most acute vision.