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.
Fusion
The power of coordination by which the images received by the two eyes become a single image.
Glaucoma
An ocular disease causing a sustained increase in intraocular pressure that the eye cannot withstand causing damage to its structure or impairment of vision.
Hyperopia
Also known as farsightedness. A refractiver error in which, because the eyeball is short or the refractive power of a lens is weak, the point of focus for rays of light from distant objects falls behind the retina;
Iris
The colored circular membrane suspended behind the cornea and immediately in front of the lens. The Iris regulates the amount of light entering the eye by changing the size of the pupil.
Irregular Astigmatism
A refractive condition caused by a cornea which is damaged and irregular so that the rays of light come to many focal points on the retina; is not correctable by cylinders.
Iseikonic Lenses
Spectacle lenses specially designed to manipulate image size when dissimilar sizes makes it difficult or impossible for fusion to occur; such as in Aniseikonia.
Macula
The small area of the retina that surrounds the Fovea and that with the Fovea, comprises the area of the retina that gives distinct vision.
Mixed Astigmatism
The refractive condition in which light comes to two points of focus where one point is in front of the retina, and the other is behind the retina.
Myopia
Also known as nearsightedness. A refractive error in which the eyeball is too long in relation to its focusing power; thus the point of focus for rays of light from distant objects is in front of the retina.
Oculus Dexter
O.D. The right eye
Oculus Sinister
O.S. The left eye
Oculus Uterque
O.U. Each eye
Optic Nerve
The special nerve of the sense of sight that carries impluses from the retina to the brain.
Phoria
A constant TENDENCY for the eyes to turn from the normal position for binocular vision. A latent root word used with a prefix (for example, hyperphoria, esophoria, exophoria.).
Presbyopia
A gradual lessening of the power of accommodation due to a physiologic change that become noticeable about the age of 40.
Ptosis Crutch
A small spring wire attached nasally to a spectacle frame to lift a drooping lid.
Pupil
The central opening of the Iris through which light is permitted to enter the eye.
Regular Astigmatism
A refractive condition in which rays of light come to two focal points and is correctable by cylinders.
Retina
Innermost coat of the eye, formed of sensitive nerve elements and connected with the optic nerve. Like the “film” of a camera.
About how many rods are in the Retina?
About 120 million.
About how many cones are in the Retina?
About 6 million.
What do Cones allow us to see?
Day vision, Detail, and Color.
What do Rods allow us to see?
Night Vision, Peripheral Vision, and Black and White.
Where is the highest concentration of Cones and Rods?
The highest concentration of cones is near the Fovea, as you go father out the cones decrease and the rods increase.
Sclera
The white part of the eye-a tough covering which, with the cornea, forms the external protective coat of the eye.
Scotoma
A blind area of reduced vision in the visual feild.
Simple Hyperopic Astigmatism
The refractive condition where one point of focus falls on the Retina and the other point of focus falls behind the retina.
Simple Myopic Astigmatism
The refractive condition where one point of focus falls on the retina and the other point of focus falls in front of the retina.
Strabismus
Failure of the two eyes to simultaneously direct their gaze at the same object because of muscle imbalance. Also known as squint.
Suspensory Ligaments
The suspensory apparatus of the lens. Numerous fine tissue strands that stretch from the ciliary processes to the lens equator and support the lens in place.
Tropia
A DEFINITE and obvious and obvious turning of the eyes from the normal position for binocular vision. A latent root word used with a prefix to denote the type of strabismus (for example, heterotrophia, esotropia, exotropia.).
Vitreous Humor
The transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens.
What is the Index of Refraction of the Vitreous Humor?
1.33
What is the Optic Chiasm?
It is an X-like structure were the optic nerves cross after leaving the eye.
What is the Geniculate Body?
It is where the optic nerves end after leaving the eye and forming the Optic Chiasm.
What is the Visual Cortex?
It is where the information from the optic nerve gets transmitted to. It is a part of the Occipital lobe (portion of the brain) where the conscious recognition of visual impulses takes place.
Name the three different Tunics.
Fibrous Tunic, Vascular Tunic, and the Neural Tunic.
What is the Fibrous Tunic and what does it consist of?
It is the outer protective coat of the eye. It consists of the Sclera and the Cornea.
What is the Vascular Tunic and what does it consist of?
It is the middle coat of the eye. It consists of the iris, the ciliary body, and the choriod.
What is the Neural Tunic and what does is consist of?
It is the inner most coat of the eye. It consist of the Retina.
Name the Extra-Ocular Muscles.
Temporal Rectus (External Rectus), Nasal Rectus (Internal Rectus), Superior Rectus, Inferior Rectus, Superior Oblique, and the Inferior Oblique.
What does Exo mean?
Out
What does Eso mean?
In
What does Hyper mean?
Up
What does Hypo mean?
Down
What is constantly manufacturing the Aqueous Humor?
The Ciliary Body.
