Ophthalmic Medical Assisting - Chapter 2

Bowman Membrane

Acts as an anchor for the epithelium.

Describe the course of aqueous humor into and out of the eye, naming the principal ocular structures involved:

Aqueous humor enters the eye from behind the iris, flows across the back of the iris, through the pupil, and into the anterior chamber; it leaves the anterior chamber at the filtration angle and passes through the trabecular meshwork, the canal of Schlemm, aqueous veins and into the blood vessels.

The macula contains most of the ___ cells?

Cone.

Descemet Membrane

Contributes to rigidity.

Stroma

Contributes to rigidity.

Inferior Rectus muscle

Downward rotation

Inferior Oblique muscle

Excyclotorsion - up and outward

Describe how the pupil dilates and contracts, naming the muscles involved:

Fibers of the dilator muscle that extend from the pupil to the boundary of the iris contract to dilate the pupil; contraction of the sphincter muscle that encircles the pupil makes the pupil smaller.

Superior Oblique muscle

Incyclotorsion - down and inward

Medial Rectus muscle

Inward rotation

Name the 3 main structures that make up the uveal tract.

Iris, ciliary body & choroid.

Briefly describe how the eye converts light rays to a perceived image, naming the principal structures involved in the process:

Light rays reflected from an object are focused by the cornea and the lens to produce an upside-down image of the object on the light-sensitive retina. The retina converts the image to electrical impulses, which are carried by the optic nerve to the brain's visual cortex, where they produce the sensation of sight.

Endothelium

Maintains proper fluid balance.

Give 4 reasons why tears are important to the functioning of the eye:

Ocular comfort, clear vision, provide moisture, nourish the eye.

Name the 4 primary structures included in the Adnexa:

Orbit, extraocular muscles, eyelids & lacrimal apparatus.

Name the 3 layers of the eyelid:

Outer layer of skin, middle layer of fibrous tissue and muscle, and inner layer of tissue (conjunctiva)

Lateral Rectus muscle

Outward rotation

The retina includes a photoreceptor layer containing 2 types of cells; _________________ & ____________________.

Rods & Cones

How are the functions of these 2 types of retinal photoreceptor cells different? (Rods & Cones)

Rods are largely responsible for vision in dim light (night vision) and for peripheral vision; Cones provide sharp central vision and color perception.

Epithelium

Serves as a first line of defense against infection and injury.

What is the relationship between the lacrimal gland, lacrimal sac and nasolacrimal duct?

Tears are produced by the lacrimal gland; tears are collected in the lacrimal sac; tears drain into the nasal cavity by means of the nasolacrimal duct.

Describe the structure and function of the orbit:

The bony cavity in the skull that houses the globe, extraocular muscles, blood vessels, & nerves; protects the globe from major injury by a rim of bone.

What is the physiologic process and purpose of accomodation?

The curvature of the lens can change, becoming rounder, to focus images of objects that are closer to the eye.

What structure, besides the cornea, provides the eye's focusing power?

The lens.

Describe the route of nerve impulses through the retrobulbar visual pathway:

The optic nerves from each eye merge at the optic chiasm. Axon fibers from the nasal retina of each eye cross to the opposite side of the chiasm, while axons from the temporal retina of each eye continue on the same side. The realigned axons emerge from the chiasm as the left and right lateral geniculate bodies. There, the axons synapse (connect) to the optic radiations, which travel to the right and left halves of the visual cortex of the brain.

Name the 3 layers of tear film and their functions:

The outer, oily layer helps prevent evaporation of moisture from the middle, aqueous layer; the middle layer provides moisture, oxygen and nutrients to the cornea; the inner mucinous layer promotes even spread of the tear film.

Briefly describe how the retina works to produce sight:

The retinal rods and cones receive light rays and, in turn, generate electric (nerve) impulses. These impulses are transmitted to the brain, where the visual messages they carry are converted to the sensation of sight.

What is the main function of the vitreous?

To act as a shock absorber for the eye and help maintain the spherical shape of the globe.

What is the principal function of the cornea?

To focus light rays reflected to the eye, contributing about 2/3 of the focusing power of the eye.

Why is the balance between inflow and outflow of aqueous humor important?

To maintain intraocular pressure.

What are the 2 principal functions of the lacrimal apparatus?

To produce and drain tears.

What is the function of the Sclera?

To protect intraocular contents.

What are the 3 functions of the eyelids?

To protect the eye from injury, to exclude light, to aid in lubricating the ocular surface.

What is the function of the ciliary processes?

To secrete aqueous humor.

What is the main function of the choroid?

To supply blood (nourishment) to the outer layers of the retina.

Superior Rectus muscle

Upward rotation

The lens is attached to the ciliary body by transparent fibers called:

Zonules.