Cornea, Retina, and Central Visual System Flashcards
In which of the following locations would one NOT find melanin?
a. iris.
b. ciliary body.
c. retinal pigment epithelium (RPE).
d. uveal tract.
e. sclera.
e. sclera (Correct Answer)
Explanation:
Melanin is present in pigmented ocular structures like the iris, ciliary body, RPE, and uveal tract. The sclera, being a tough, fibrous, white outer layer of the eyeball, lacks melanin. Therefore, e is correct.
Systemic exposure to drugs and chemicals is most likely to target which of the following
retinal sites?
a. RPE and ganglion cell layer.
b. optic nerve and inner plexiform layer.
c. RPE and photoreceptors.
d. photoreceptors and ganglion cell layer.
e. inner plexiform layer and RPE.
c. RPE and photoreceptors (Correct Answer)
Explanation:
The outer retina, including the retinal pigment epithelium (RPE) and photoreceptors, is especially vulnerable to systemic drugs due to high metabolic demand and blood supply via the choroid. This makes c the most accurate answer.
Which of the following structures is NOT part of the ocular fundus?
a. retina.
b. lens.
c. choriod.
d. sclera.
e. optic nerve.
b. lens (Correct Answer)
Explanation:
The fundus refers to the interior surface of the eye opposite the lens, including the retina, optic disc, macula, fovea, and posterior pole. The lens is anterior and not visible during a fundoscopic exam, making b correct.
Drugs and chemicals in systemic blood have better access to which of the following sites
because of the presence of loose endothelial junctions at that location?
a. retinal choroid.
b. inner retina.
c. optic nerve.
d. iris.
e. ciliary body.
a. retinal choroid (Correct Answer)
Explanation:
The choroidal vasculature lacks tight junctions (unlike the inner retina which has the blood-retinal barrier), allowing more drug penetration. Therefore, a is correct.
All of the following statements regarding ocular irritancy and toxicity are true EXCEPT:
a. The Draize test involves instillation of a potentially toxic liquid or solid into the eye.
b. The effect of the irritant in the Draize test is scored on a weighted scale for the cornea,
iris, and conjunctiva.
c. The Draize test usually uses one eye for testing and the other as a control.
d. The Draize test has strong predictive value in humans.
e. The cornea is evaluated for opacity and area of involvement in the Draize test.
book said d not e
Which of the following statements regarding color vision deficits is FALSE?
a. Inheritance of a blue–yellow color deficit is common.
b. Bilateral deficits in the visual cortex can lead to color blindness.
c. Disorders of the outer retina produce blue–yellow deficits.
d. Drug and chemical exposure most commonly results in blue–yellow color deficits.
e. Disorders of the optic nerve produce red–green deficits
book said a not c
A substance with which of the following pH values would be most damaging to the cornea?
a. 1.0.
b. 3.0.
c. 7.0.
d. 10.0.
e. 12.0
book said e not b
Which of the following statements concerning the lens is FALSE?
a. UV radiation exposure is a common environmental risk factor for developing cataracts.
b. Cataracts are opacities of the lens that can occur at any age.
c. The lens continues to grow throughout one’s life.
d. Naphthalene and organic solvents both can cause cataracts.
e. Topical treatment with corticosteroids can cause cataracts.
book said d not e
Which of the following is NOT a reason why the retina is highly vulnerable to toxicant
induced damage?
a. presence of numerous neurotransmitter systems.
b. presence of melanin in the RPE.
c. high choroidal blood flow rate.
d. high rate of oxidative mitochondrial metabolism.
e. lack of gap junctions
e. lack of gap junctions (Correct Answer)
Explanation:
The retina does contain gap junctions which aid in cell-to-cell communication. Their absence is not a contributing factor to toxicity vulnerability, making e correct.
A deficiency in which of the following vitamins can result in degeneration of optic nerve
fibers?
a. vitamin A.
b. vitamin B3.
c. vitamin C.
d. vitamin B12.
e. vitamin E.
d. vitamin B12 (Correct Answer)
Explanation:
Vitamin B12 deficiency can cause optic neuropathy due to impaired myelination and axonal integrity. This leads to degeneration of optic nerve fibers, hence d is the correct answer.
