Visual System I- The Eye Flashcards
What are the three layers of the eye?
- Inner (Retina)
- Middle (Vascular)
- Outer (External Fibrous Skeleton)
What are the two parts of the Outer layer?
- Sclera
2. Cornea
What is the structure of the Sclera?
Tough white covering of the posterior 5/6 of the eye
What is the function of the Sclera?
Protection of internal structures and site for muscle insertion
What is the structure of the Cornea?
Transparent covering of the anterior 1/6 of the eye
What is the function of the Cornea?
Major refractive structure, bending light rays to form images on the retina.
What are the components of the Middle (Vascular) Layer?
- Choroid
- Ciliary Body
- Iris
What is the structure of the Choroid?
- Between Sclera and Retina
- Continuous anteriorly with ciliary body
What is the function of the Choroid?
Pigmented and dense vascular bed
What is the structure of the Ciliary Body?
Ring like thickening posterior to the corneoscleral junction
What are the two parts of the Ciliary Body and what is their function?
- Ciliary Muscle (Muscular portion)- controls the thickness, therefore controlling the focus of the lens
- Ciliary Process (Vascular portion)- secretes aqueous humor
What is the structure of the Iris?
Thin pigmented contractile dipahragm lying on the anterior surface of the lens.
-Central aperture= pupil
What structure decreases the diameter of the pupil?
Sphincter Pupillae
What structure increases the diameter of the pupil?
Dilator Pupillae
What are the components of the Inner (Retina) Layer?
- Optic Part
2. Non Optic Part
What are the components of the Optic Part of the Inner (Retina) Layer?
- Pigmented
- Neural
- Fundus
What is the structure of the Pigmented layer of the Retina?
Composed of epithelium
What is the function of the Pigmented layer of the Retina?
Provides nutrition, protection, and maintenance for the neural layer.
-It absorbs the light not captured by the neural layer
What is the structure of the Neural layer of the Retina?
Contains photoreceptors and associated neurons.
What is the function of the Neural layer of the Retina?
Specialized for sensing light and processing the resultant information.
What is the fundus and what are its components?
- The inner surface of the retina
1. Optic Disc
2. Macula
What is the structure and function of the Optic Disc?
S: Distinct white circular area
F: Region where vacular and neural elements are entering/leaving the eye- contains no photoreceptors.
What is the structure and function of the Macula?
S: Yellow oval area lateral to the optic disc. Has the Fovea.
F: Supports high visual acuity.
What is the structure and function of the Fovea?
S: Small depression in the center of the Macula. Area with the proximal vascular and neural elements are shifted to the side, and has the greatest density of photoreceptors.
F: Greatest ability to resolve detail. High visual aquity.
What is the structure and function of the Optic Part?
S: Anterior continuation of the pigmented layer
F: Picks up random light not absorbed by Retina
Describe the structure of the Lens?
Transparent, biconvex encapsulated structure.
Lying posterior to the iris and anterior to the vitreous body
What is the function of the Lens?
Refractive structure, bending light rays to form images on the retina
Why is it important that the capsule of the lens is anchored to the encircling ciliary body?
The ciliary muscle controls lens accommodation.
What are the two segments in the eye?
- Anterior and Posterior
What does the anterior segment contain and where is it?
-Aqueous humor and is located anterior to the lens
What does the posterior segment contain and where is it?
Vitreous body (gelatinous mass) and is located posterior to the lens
Explain the basic steps of Image Formation.
- Decision to examine an object
- The extraoccular muscles move the eye, placing the object at the center of the visual field.
- The eye is directed at a point on the visual target called the fixation point.
- Light from the fixation point is focused on the fovea, and the remainder of the target is focused on the Retina surrounding the fovea.
What are the properties of Light?
- Electromagnetic radiation that is visible to the eyes
- Characterized by wavelength, frequency, and amplitude.
- Travels in a straight line until it interacts with an object.
Describe absorption.
Transfer of light energy to a particle or a surface
Describe Refraction
Bending of light when it travels from one transparent medium to another, occurs because light speed differs in different media.