CD 17 Ocular

Question 1

Intraocular melanin is involved with drug and environmental chemical toxicity to the retina by what mechanism?
A. melanin has low binding affinity for most environmental chemicals
B. melanin is not located intraocularly
C. binding PAHs, chloroquine, and heavy metals.
D. melanin is depleted in the uveal tract between sclera and retina

Answer 1

C. binding PAHs, chloroquine, and heavy metals.

Explanation and Reference:
Intraocular melanin exists in multiple regions of the eye, has a high affinity for chloroquine, heavy metals, including lead, and other drugs where they can accumulate, and then are released slowly. C&D, 8th, pp. 52, 780-785

Question 2

How, in the Functional Observational Battery, would one evaluate the potential effects of a toxicant on vision?
A. evaluation of ocular irritancy
B. observing the pupillary response to light
C. scoring the degree of lens opacity
D. evaluation of rod and cone density

Answer 2

B. observing the pupillary response to light

Explanation and Reference:
Only two visual responses are tested in the FOB; pupil contraction based on light and approach to the eye. C&D 9th, p. 888.

Question 3

Alternative non-animal methods for testing the potential for chemicals to cause topical injury to the eye have been developed by an international consortium and adapted by several regulatory agencies. What animal test do these alternative methods replace?
A. the Draize test in rabbits
B. the Hay’s test in mice
C. the maze test in rats
D. the gaze test in primates

Answer 3

A. the Draize test in rabbits

Explanation and Reference:
The correct answer is the Draize test in rabbits. This had been the standard since the 1940s but has been criticized in the 21st Century for high inter-laboratory variability, subjective scoring, poor predictive value, and for causing undue pain and distress to the test animals. The gaze test is used to evaluate the ability to generate and hold a steady gaze without drift or gaze-evoked nystagmus.
This is a test used in humans and other primates. The maze test is used to test memory, cognition, and behavior, commonly in rats. Hay’s test is a method for detecting bile salts in urine in any species. C&D 9th pp. 885-886.

Question 4

What ocular structure is the target of chronic, high-dose tamoxifen therapy?
A. cornea
B. lens
C. retina
D. conjunctiva

Answer 4

C. retina

Explanation and Reference:
Tamoxifen, a nonsteroidal antiestrogenic drug that competes with estrogen for its receptor sites and used for treatment of metastatic breast carcinoma, causes retinopathy following chronic high-dose therapy. C&D, 9th ed. p. 892

Question 5

Which ocular structure is most often affected following systemic long-term or high dose use of corticosteroids in humans?
A. cornea
B. lens
C. retina
D. iris

Answer 5

B. lens

Explanation and Reference:
Long-term systemic use of corticosteriouds is implicated in cataracts. C&D 9th edition, page 880
Exposure of rats to a naphthalene-derived pesticide resulted in a loss of circulating erythrocytes that was accompanied by reticulocytosis and hemoglobinuria. No pathological changes were observed in the bone marrow; however, spleens were found to be enla
anemia due to iron deficiency
mechanical (march) hemoglobinuria
aplastic anemia
non-immune hemolytic anemia

Question 6

What region of the eye is more susceptible to systemic toxicants?
A. cornea and ciliary body
B. retinal pigment epithelium (RPE) and photoreceptors
C. iris and lens
D. cornea and iris

Answer 6

B. retinal pigment epithelium (RPE) and photoreceptors

Explanation and Reference:
More vascularized regions of the eye are more susceptible to systemic toxicants. C&D C&D 9th, p. 884, Figure 17-3; p. 890

Question 7

What mechanism explains chloroquine accumulation in the eye resulting in retinopathy?
A. reversible intracellular binding to melanin
B. increased permeability of the blood-aqueous barrier
C. decreased aqueous humor outflow
D. porosity of the retinal pigment epithelium

Answer 7

A. reversible intracellular binding to melanin

Explanation and Reference:
Chloroquine and its metabolites have a high affinity to melanin, which results in very high concentrations accumulating in the choroid and retinal pigment epithelium, ciliary body, and iris, and can cause the characteristic “bull’s eye retina”. C&D9th p 891

Question 8

Which ocular tissue is highly vulnerable to systemic, toxicant induced structural and/or functional damage?
A. cornea
B. retina
C. lens
D. iris

Answer 8

B. retina

Explanation and Reference:
Alterations in retinal and visual function are among the most common early signs of chemical exposure damaging the ocular system which has been interpreted as their being particularly vulnerable to toxic insults. C&D 8th, p.780-781.

Question 9

What is the metabolite of methanol that is associated with disruption of oxidative energy metabolism resulting in retinal and optic nerve toxicity in humans?
A. metholic acid
B. methyl alcohol
C. formic acid
D. methane

Answer 9

C. formic acid

Explanation and Reference:
Humans and primates are highly sensitive to the permanent structural alterations in the optic nerve and retina induced by methanol due to their limited ability to oxidize formic acid to less toxic metabolites.C&D 8th, p. 785