THERAPEUTICS EX4 L1 (EYE ANATOMY) (BISWAL)

Four main causes of blindness?

Cataracts

Glaucoma

Age-related macular degeneration (AMD)

Diabetic retinopathy

Three routes by which anesthesia is administered via the eye?

Subconjunctival route

Retrobulbar route

Peribulbar route

The uvea is comprised of what three parts?

Iris

Ciliary body

Choroid

Anterior segment of the eye contains what structures?

Canal of Schlemm

Limbus

Iris

Pupil

Cornea

Episcleral veins

Ciliary body

Conjunctiva

Trabecular meshwork

Lens

Posterior chamber

Anterior chamber angle

Describe the cornea

Transparent and avascular tissue organized into five layers

Five layers of the cornea?

Epithelium

Bowman's membrane

Stroma

Descemet's membrane

Endothelium (hydrophobic barrier)

Describe the endothelium

Lying most posteriorly, the endothelium is a monolayer of cells adhering to each other by tight junctions

Role of the endothelium?

Hydrophobic barrier, maintain corneal dehydration by active transport processes

T/F: The cornea is an important barrier to foreign matter, including drugs.

True

Describe the limbus

A transitional zone (1-2 mm wide) lying at the periphery of the cornea and adjacent to the sclera

Limbal structures include limbal blood vessels, tears; provide important nutrients and immunological defense mechanisms for the cornea.

Anterior chamber angle is formed by what?

Cornea and iris root

What volume of aqueous humor is contained within the anterior chamber?

250 microliters

What volume of aqueous humor is contained within the posterior chamber?

50 microliters

Posterior chamber's boundaries are defined by what?

The boundaries of the ciliary body processes, posterior surface of the iris, and lens surface

T/F: The iris and pupil are found in the most anterior portion of the uveal tract, which also includes the ciliary body and choroid.

True

T/F: The posterior surface of the iris is a sparsely pigmented bilayer of epithelial cells.

False; densely pigmented.

Mydriasis = what?

A. Dilation

B. Constriction

A. Dilation

Miosis = what?

A. Dilation

B. Constriction

B. Constriction

Which muscle mediates mydriasis?

Dilator smooth muscle

Which muscle mediates miosis?

Sphincter smooth muscle

Dilator smooth muscle is innervated by what?

A. Sympathetic nervous system

B. Parasympathetic nervous system

A. Sympathetic nervous system

Sphincter smooth muscle is innervated by what?

A. Sympathetic nervous system

B. Parasympathetic nervous system

B. Parasympathetic nervous system

Which of the following structures of the eye is not a part of the anterior segment?

A. Iris

B. Pupil

C. Cornea

D. Retina

D. Retina

Which of the following is not associated with corneal structure?

A. Epithelium

B. Bowman's membrane

C. Lacrimal sac

D. Stroma

E. Endothelium

D. Stroma

Two specialized roles of the ciliary body?

Production and secretion of aqueous humor by the epithelial bilayer

Accommodation by the ciliary muscle

Describe "accommodation"

Coordinated contraction of the smooth muscle apparatus by the parasympathetic nervous system causes the zonular fibers suspending the lens to relax, allowing the lens to become more convex and to shift slightly forward thus permitting focusing on near objects

Aqueous humor pathway?

Ciliary body -> posterior chamber -> pupil (to provide oxygen, nutrition to avascular lens+cornea) -> anterior chamber -> trabecular meshwork -> Schlemm's canal -> episcleral venous system

What are the two outlets at which the aqueous humor drains?

Trabecular meshwork

Uveoscleral outflow

Lens is suspended by what?

The ciliary zonule

Diameter of the lens?

About 10 mm in diameter

enclosed in a capsule

T/F: The bulk of the lens is composed of fibers derived from proliferating lens epithelial cells located under the anterior portion of the lens capsule.

True

T/F: Lens fibers are produced at the beginning of life and are therefore finite in number.

False; produced continuously throughout life.

Lens opacification is termed what?

Cataract

Structures in the posterior segment of the eye?

Zonule

Choroid

Sclera

Retina

Optic disk

Optic nerve

Central retinal artery and vein

Retinal arterioles and veins

Vitreous

T/F: The outermost coat of the eye, the sclera, covers the posterior portion of the globe.

True

T/F: The external surface of the scleral shell is covered by an episcleral vascular coat, Tenon's capsule, and the conjunctiva. The tendons of the six extraocular muscles insert collagen fibers into the superficial scleral.

True yea but read that a little

Retinal layers?

Nerve fiber layer

Ganglion cell layer

Inner plexiform layer

Inner nuclear layer

Outer plexiform layer

Outer nuclear layer

Photoreceptor outer segment

Retinal pigment epithelium (RPE)

Bruch's membrane

Choroid

T/F: Rods are for color, cones are for light.

False; rods are sensitive to light of low intensity; cones are responsible for color vision.

What are the three kinds of cone cells?

Red green blue

T/F: Humans deficient in vitamin A lose their ability for dark adaptation.

True

What common test for color-blindness was listed on the slides?

Ishihara charts

Circle bubble number ones

How is color-blindness inherited?

Recessive X-linked characteristics

When lesions exist on the V8 area of the visual cortex resulting in colorblindness, we term this deficit what?

Achromatopsia

T/F: Approximately 80% of the eye's volume is the vitreous.

True

Describe the vitreous

A clear medium containing collagen type II, hyaluronic acid, proteoglycans, glucose, ascorbic acid, amino acids, and a number of inorganic salts

Role of the optic nerve?

Conduction of retinal output to the CNS

Which of the following structures in the eye is associated with accommodation and secretion of aqueous humor?

A. Pupil

B. Cornea

C. Lens

D. Ciliary body

D. Ciliary body

Which of the following structures of the eye is associated with conducting the retinal output to the brain?

A. Ciliary body

B. Trabecular meshwork

C. Optic nerve

D. Photoreceptors.

C. Optic nerve

Which of the following specialized retinal cells are responsible for photoreception?

A. Ganglion cells & rods

B. Rods and cones

C. Cones and corneal endothelium

D. None of the above

B. Rods and cones

Which of the following statements is not true?

1. Humans deficient in vitamin A lose their ability for dark adaptation

.2. The outermost coat of the eye, the sclera, covers the posterior portion of the globe.

3. The chromophore of both rods and cones is 11-cis-butanol

.4. Lens opacification is associated with cataract.

3. The chromophore of both rods and cones is 11-cis-butanol.

Describe visual acuity

The degree to which the details and contours of objects are perceived, and it is usually defined in terms of the shortest distance by which two lines can be separated and still be perceived as two lines.

Myopia is ____________

A. Nearsightedness

B. Farsightedness

A. Nearsightedness

Hyperopia is _________

A. Nearsightedness

B. Farsightedness

B. Farsightedness

What is strabismus?

A misalignment of the eyes and one of the most common problems in children

What is amblyopia?

Loss of visual acuity where one eye is blurred or distorted due to a refractive error

Loss of vision in cases of amblyopia is termed?

Amblyopia ex anopsia

The loss of visual acuity due to amblyopia is

A. Correctable

B. Uncorrectable

B. Uncorrectable

T/F: Typically, in persons with amblyopia, one eye will be weak and have poor vision, while one eye is strong with normal vision.

True

Amblyopia is also referred to as ___________

lazy eye

What is the cause of astigmatism?

Curvature of the cornea is not uniform

How can we correct astigmatism?

Cylindric lenses