FMICHAEL A. SAIDEL AND ASHLEY ROHR
1 A diurnal curve of IOP taken in a patient revealed the following measurements: 13, 13, 15, 15, 15, 18, 23, 24 mmhg. What is the mean/mode/median IOP?
|
Mean |
Mode |
Median |
|
|
A) |
18.0 |
15.0 |
15.5 |
|
B) |
18.0 |
16.0 |
15.0 |
|
C) |
17.0 |
15.0 |
15.0 |
|
D) |
17.0 |
16.0 |
15.5 |
QUESTIONS 2 and 3 You are preforming a new screening test for glaucoma on 100 patients. In reality, 15 of the patients have glaucoma and 85 of the patients do not. The screening test identifies 50 people with positive results and 50 people with negative (normal) results. Forty of those patients who had positive results do not have glaucoma, and five patients who truly have glaucoma have negative results on the screening test.
2 What is the number of false positives for this test?
A) 50
B) 10
C) 45
D) 40
3 What are the sensitivity and specificity of this test?
A) 67%, 53%
B) 53%, 67%
C) 20%, 90%
D) 90%, 20%
4 The null hypothesis for a study that you are conducting on a new test for monitoring diabetic blood glucose control is that there is not a significant difference in results compared with the conventional method of hemoglobin A1c testing. If we incorrectly reject the null hypothesis and conclude that there is a difference between the results of the two tests, this is an example of:
A) type I error
B) type II error
C) sampling error
D) power
5 To properly analyze data to ensure that the conclusions are not a result of confounding variables, which test would be the most appropriate?
A) ANOVA test
B) Student’s t-test
C) χ2 test
D) Multivariate analysis
6 You decide to conduct a study looking at whether smoking is a risk factor for age-related macular degeneration (ARMD). You identify a similar demographic group of patients with ARMD and those without ARMD and then determine their smoking history. What type of study does this scenario best describe?
A) Cohort study
B) Single-masked study
C) Case-controlled study
D) Double-blind study
7 Your colleague also decides to look at ARMD. She monitors a group of medical students over time. She finds that the medical students who smoke are at a greater risk of developing ARMD. What type of study is this?
A) Case-controlled study
B) Retrospective study
C) Randomized controlled trial
D) Cohort study
8 The p value of a study is calculated to be p < 0.02. Which of the following statements is correct?
A) A lower p value would more likely be the result of chance.
B) The likelihood of results occurring as a matter of chance is 2%.
C) A higher p value would more likely be a result of a true difference.
D) 2% of the data was biased.
9 At a conference for new eye drop to treat dry eye, a speaker presents data from a study that reports resolution in symptoms with the new eye drop in five out of five patients. These results may be due to all of the following study weaknesses except:
A) selection bias
B) no control group
C) lack of significance
D) small sample size
10 Which of the following structures is not derived from neural crest cells?
A) Ciliary muscles
B) Corneal endothelium
C) Lens
D) Trabecular meshwork
11 Which of the following is the correct order of development?
A) Optic sulci→optic pit→optic vesicle→optic cup
B) Optic sulci→optic vesicle→optic pit→optic cup
C) Optic pit→optic sulci→optic vesicle→optic cup
D) Optic pit→optic vesicle→optic pit→optic cup
12 Which of the following disorders demonstrates a mitochondrial inheritance pattern?
A) Retinoblastoma
B) Leber hereditary optic neuropathy
C) Retinitis pigmentosa
D) Fabry disease
13 Which of the following mutations is associated with aniridia?
A) Rb
B) PAX6
C) ABCA4
D) Rhodopsin
14 All of the following options are ways to increase the amount of drug absorption from an eye drop except:
A) prior administration of a topical anesthetic
B) punctal occlusion
C) increased lipid solubility
D) increased hydrophilicity of the drug
15 All of the following effects are seen when a direct-acting cholinergic agonist is used except:
A) miosis
B) decrease in zonular tension
C) increase in outflow facility
D) decrease in accommodation
16 A patient’s medication list includes drug X. He is going to undergo a combined trabeculectomy and cataract extraction under general anesthesia. The anesthesiologist is hesitant to use succinylcholine in view of a potential drug interaction. What could drug X be?
A) Levobunolol
B) Carbachol
C) Echothiophate iodide (phospholine iodide)
D) Apraclonidine
17 Which is the correct order of increasing mydriatic duration?
A) Homatropine, scopolamine, cyclopentolate, tropicamide
B) Atropine, homatropine, tropicamide, cyclopentolate
C) Tropicamide, homatropine, scopolamine, atropine
D) Atropine, homatropine, scopolamine, tropicamide
18 All of the following statements except one are true of medications in the same class as diclofenac:
A) can be associated with corneal complications, including corneal melt and perforation
B) can be used for treatment of postoperative ocular inflammation
C) result in the increased production of thromboxane
D) result in decreased synthesis of prostaglandins
19 Which of the following is a side effect of apraclonidine?
A) Fever
B) Lid retraction
C) Conjunctival hyperemia
D) Papillary conjunctivitis
20 All of the following side effects may be seen with the use of a prostaglandin analogue except:
A) conjunctival hyperemia
B) cystoid macular edema
C) decrease in iris pigmentation
D) hypertrichosis
21 Which of the following IOP-lowering therapy would be least suitable for a patient who has mild bronchoconstrictive lung disease?
A) Timolol
B) Betaxolol
C) Latanoprost
D) Brimonidine
22 All of the following effects may be associated with the use of oral acetazolamide except:
A) metallic taste
B) paresthesias
C) weight gain
D) metabolic acidosis
23 List the following topical steroids in terms of ability to elevate IOP in susceptible patients from most to least likely.
A) Prednisolone, hydrocortisone, dexamethasone, fluorometholone
B) Prednisolone, dexamethasone, hydrocortisone, fluorometholone
C) Difluprednate, fluorometholone, prenisolone, hydrocortisone
D) Difluprednate, prednisolone, fluorometholone, hydrocortisone
24 What is the mechanism of action of ciprofloxacin?
A) Inhibits DNA gyrase
B) Inhibits protein synthesis by binding to 30S ribosomal subunit
C) Inhibits protein synthesis by binding to 50S ribosomal subunit
D) Inhibits synthesis of folic acid
25 What percentage of patients allergic to penicillin will have cross-reactivity to cephalosporins?
A) 5%
B) 10%
C) 20%
D) 50%
26 Allergy to which one of the following medications is a relative contraindication to the use of methazolamide?
A) Bactrim
B) Penicillin
C) Erythromycin
D) Tetracycline
27 Which topical eye drop and potential side effect are mismatched?
A) Mitomycin C—scleral perforation
B) Pilocarpine—brow ache
C) Epinephrine—black conjunctival deposits
D) Cyclosporine—decreased tear production
28 Amphotericin B alone may be effective in the treatment of all of the following infectious agents except:
A) aspergillus
B) candida
C) cryptococcus
D) mucor
29 Agents reported to be effective in the treatment of Acanthamoeba include all of the following except:
A) polyhexamethylene biguanide (PHMB)
B) propamidine
C) chlorhexidine
D) flucytosine
30 Which of the following characteristics is undesirable in the design of a viscoelastic?
A) Hyperosmotic
B) Nonantigenic
C) Inert
D) Clear
31 Which of the following anesthetic has the shortest duration of effect?
A) Lidocaine
B) Bupivacaine
C) Procaine
D) Mepivacaine
32 Which of the following extraocular muscles is least likely to be affected with a retrobulbar anesthetic block?
A) Superior rectus
B) Superior oblique
C) Lateral rectus
D) Medial rectus
33 Which drug and mechanism of action are paired correctly?
A) Ketotifen fumarate—NSAID
B) Olopatadine HCl—mast-cell stabilizer
C) Naphazoline HCl—NSAID
D) Diclofenac sodium—antihistamine
34 Which of the following layers of the cornea will stain most with PAS (periodic acid–Schiff)?
A) Endothelium
B) Bowman layer
C) Epithelial wing cells
D) Descemet membrane
35 Which tear layer contains immunoglobulin A?
A) Mucin layer
B) Lipid layer
C) Aqueous layer
D) Glycoprotein layer
36 Which one of the following contributes to the aqueous layer of the tear film?
A) Glands of Wolfring
B) Glands of Zeis
C) Goblet cells
D) Meibomian gland
37 What are the main contributors to the innervation of the cornea?
A) Short anterior ciliary nerves
B) Long anterior ciliary nerves
C) Short posterior ciliary nerves
D) Long posterior ciliary nerves
38 Which one of the following associations is true about corneal collagen components?
A) Corneal wound healing—type III collagen
B) Descemet membrane—type I collagen
C) Bowman layer—type IV collagen
D) Stroma—type II collagen
39 Which one of the following most closely approximates normal aqueous humor production?
A) 1 µl/min
B) 2 µl/min
C) 1 ml/min
D) 2 ml/min
40 Which of the following electrolytes is found in the aqueous humor at half the level of the plasma?
A) Sodium
B) Calcium
C) Zinc
D) Potassium
41 All of the following substances found in the anterior chamber are indicative of a disruption of the blood–aqueous barrier except:
A) pigment
B) fibrin
C) white blood cells
D) red blood cells
42 Which is the largest crystallin in the human lens?
A) β-Crystallin
B) α-Crystallin
C) γ-Crystallin
D) Taxon-specific crystallin
43 Which one of the following is a protective mechanism against oxidation in the lens?
A) Glutathione
B) Vitamin A
C) Aldose reductase
D) Vitamin B12
44 Which one of the following is not associated with a decrease in hyaluronate concentration in the vitreous humor?
A) Vitritis
B) Phakia
C) Diabetes
D) Myopia
45 How long does it take for a photoreceptor to renew its outer segment?
A) 10 seconds
B) 10 minutes
C) 10 hours
D) 10 days
46 Which one of the following characteristics of the retinal pigment epithelium (RPE) is not correct?
A) Retinal adhesion
B) Visual pigment regeneration
C) Transport of nutrients and removal of waste to photoreceptor cells
D) Phagocytosis of photoreceptor inner segments
47 What is the difference in light sensitivity of the rods, compared with the cones?
A) 10 times more sensitive
B) 1,000 times more sensitive
C) 10,000 times more sensitive
D) 1 million times more sensitive
48 Which bone is not part of the medial orbital wall?
A) Maxilla
B) Sphenoid
C) Zygomatic
D) Ethmoid
49 Which structure does not pass through the superior orbital fissure?
A) Ophthalmic artery
B) Frontal nerve
C) CN III
D) CN IV
50 Which of the following extraocular muscle is supplied by the superior division of the oculomotor nerve?
A) Superior oblique
B) Inferior rectus
C) Medial rectus
D) Superior rectus
|
1 |
C) |
17.0 |
15.0 |
15.0 |
To calculate the mean, or average, the sum of the data values is divided by the total number of values, i.e., 136/8 = 17. The mode is the value that occurs most frequently within the data, i.e., 15. If more than one number appears most frequently, the data can be termed bimodal, trimodal, and so on. The median is the middlemost number when the values are arranged from low to high. In this case, there are eight values; the median is the average of the fourth and fifth data points, i.e., (15 + 15)/2 = 15.
2 D) 40
The number of false positives is equal to the number of patients who had positive results on the screening test but did not actually have glaucoma. The chart below further illustrates the patients’ disease status of whether or not they have glaucoma versus their results on the new screening test.
|
Test Results |
Glaucoma |
No Glaucoma |
|
Positive |
10 (True positive) |
40 (False positive) |
|
Negative |
5 (False negative) |
45 (True negative) |
3 A) 67%, 53%
Sensitivity is the percentage of patients who have the disease but have normal results. Specificity is the percentage of patients who do not have the disease but have abnormal results.
Sensitivity = TP/(TP + FN) = 10/(10 + 5) = 67%
Specificity = TN/(TN + FP) = 45/(45 + 40) = 53%
Positive predictive value = TP/(TP + FP)
Negative predictive value = TN/(TN = FN)
4 A) Type I error
Errors may be made regarding the null hypothesis (H0), which states that no difference exists between the control group and the intervention group. If one rejects the null hypothesis when in fact the results occurred by chance, this is called a type I error or a error. If one accepts the null hypothesis when in fact there really was a difference, this is called a type II error or b error. Sampling error is bias of the data secondary to the use of a nonrepresentative population. The power of the study is β (i.e., the ability to detect a difference when a difference is present).
5 D) Multivariate analysis
When many factors can affect an outcome variable, all of them must be examined. Therefore, one may use many types of multivariate analyses, such as a multiple regression analysis, logistic regression, or Cox hazard function. An ANOVA determines whether the means of the normal distributions are identical. A student t test determines whether the means of two normal populations are far enough apart to conclude that the distributions are different. A χ2 test determines whether more than two sampled populations can be considered equal.
6 C) Case-controlled study
Two types of studies exist: retrospective (observational) and prospective (experimental). Within the retrospective, or case-control variety, either a case report or a case series may be employed. In a retrospective study, patients are taken at a single point in time and examined for a variable that occurred prior to the date of examination.
7 D) Cohort study
In a prospective, longitudinal, or cohort study, patients are enrolled and then followed up for the development of an outcome variable. Cohort studies are typically used to determine risk over time in a cohort of individuals with common traits. Prospective studies in which neither the investigator nor the patient knows whether the patient is receiving intervention or placebo are the best type of study to eliminate bias. This is referred to as a double-blind (randomized), placebo-controlled trial.
8 B) The likelihood of results occurring as a matter of chance is 2%.
The p value, also called the significance level, is a measure of the probability that the results occurred by chance alone. For example, p < 0.02 means that if an experiment were done 100 times, you would likely get the same result 98 times and you would likely get a different result 2 times because of chance. The lower the p value, the more likely that there is a true difference and the less likely that the results are due to chance.
9 C) Lack of significance
With small case series and studies, the results must be evaluated carefully, as errors can be introduced because of the small number of cases involved. Selection bias means setting criteria that eliminate cases that do not conform to the desired results. A control group helps determine whether results are due to random chance or selection bias. Researchers should be blinded as to which eye received the eye drop to avoid giving extra encouragement when testing the eye that received the drop. If all five patients improved, this could be viewed as a significant result. p values can be calculated, but they are not as meaningful when the number of cases is small.
10 C) Lens
The lens is derived from surface ectoderm. The ciliary muscle, corneal endothelium, and trabecular meshwork are all derived from neural crest cells.
11 A) Optic sulci→optic pit→optic vesicle→optic cup
The optic sulci are the first appreciable ocular structure. At approximately 22 days’ gestation, the optic sulci are visible as indentations in the neural folds. The optic pits are formed by a single layer of neuroectoderm that occurs during invagination of the sulci. The optic pits deepen to become the optic vesicles at approximately 25 days. In the fourth week of gestation, the temporal and lower walls invaginate to form the optic cup.
12 B) Leber hereditary optic neuropathy
Mitochondrial diseases demonstrate maternal transmission, where all offspring of affected children can inherit the trait but only the daughters have the ability to pass it on. An example of mitochondrial disorder is Leber hereditary optic neuropathy. Fabry’s demonstrates an X-linked inheritance pattern. Retinoblastoma can demonstrate autosomal-dominant inheritance or a sporadic new mutation. Retinitis pigmentosa can have an autosomal-dominant, autosomal-recessive, or X-linked inheritance pattern depending on the mutation.
13 B) PAX6
PAX6 mutations are associated with aniridia. Rb is associated with retinoblastoma. ABCA4 is associated with Stargardt disease. Rhodopsin mutations are associated with retinitis pigmentosa.
14 D) Increased hydrophilicity of the drug
Ways to increase absorption include decreasing the nasolacrimal pumping, decreasing the washout by another drop by increasing the interval between administrations of drops, and increasing the lipid solubility to facilitate corneal penetration. A topical anesthetic disrupts epithelial integrity, allowing greater drug absorption.
15 D) Decrease in accommodation
Direct-acting cholinergics (i.e., acetylcholine, carbachol, pilocarpine) have three postsynaptic effects: (1) They cause contraction of the iris sphincter, leading to miosis. (2) They cause contraction of the circular fibers of the ciliary muscle, resulting in relaxation of the zonular tension, which leads to an increase in accommodation. (3) They cause contraction of the longitudinal fibers of the ciliary muscles, which pulls on the scleral spur and opens the trabecular meshwork, promoting aqueous outflow. Of note, contraction of ciliary muscle can also place tension on the retina and may cause a retinal tear.
16 C) Echothiophate iodide (phospholine iodide)
Succinylcholine is a depolarizing agent (acetylcholine receptor agonist) used in anesthesia to induce short-term muscle paralysis. Echothiophate iodide is an irreversible cholinesterase inhibitor whose effects may persist for days after discontinuation of the drug. Its use could prevent succinylcholine from being metabolized, leading to prolonged respiratory paralysis. Levobunolol is a nonselective β-blocker. Carbachol is a direct-acting cholinergic. Apraclonidine is an α2 selective agonist.
17 C) Tropicamide, homatropine, scopolamine, atropine
Mydriatic duration in normal eyes is as follows: atropine (7–14 days), scopolamine (4–7 days), homatropine (3 days), cyclopentolate (1–2 days), and tropicamide (4–6 hours).
18 C) Result in the increased production of thromboxane
Diclofenac is a topical ocular NSAID. Other medications in this class include flurbiprofen, ketorolac, nepafenac, and bromfenac. Topical NSAIDs are indicated for the treatment of postoperative inflammation. These medications have been associated with corneal complications, including corneal melt and perforation. The mechanism of action of NSAIDs is by blocking the cyclooxygenase pathway, which eliminates the production of prostaglandins, prostacyclin, and thromboxane.
19 B) Lid retraction
Side effects of apraclonidine (an α2-adrenergic agonist) include conjunctival blanching, lid retraction, dry mouth, lethargy, and local response (follicular conjunctivitis). Cardiovascular or respiratory effects are extremely rare.
20 C) Decrease in iris pigmentation
Ocular side effects associated with the use of topical prostaglandin analogues include conjunctival hyperemia, hypertrichosis of eyelashes, cystoid macular edema, uveitis, and increase in iris pigmentation. Increased iris pigmentation is due to increased number of melanosomes and is greater in patients with light brown irides at baseline than in those with lighter-colored irides.
21 A) Timolol
Timolol and betaxolol are both β-adrenergic receptor antagonists. However, betaxolol is β1-selective, making it a better choice in patients with pulmonary disorders than timolol, which is nonselective. Nonselective agents can inhibit the β2 pulmonary receptors and lead to significant bronchospasm in susceptible patients. Latanoprost is a prostaglandin analog and brimonidine is an α2 agonist.
22 C) Weight gain
Systemic side effects of oral carbonic anhydrase inhibitors like acetazolamide (Diamox) include paresthesias, metabolic acidosis, a metallic taste with consumption of carbonated beverages, malaise, anorexia, weight loss, nausea, somnolence, and depression. Additionally, a local skin allergy may be noted. The incidence of side effects with topical therapy is less than that with systemic administration.
23 D) Difluprednate, prednisolone, fluorometholone, hydrocortisone
The IOP-elevating potential of a corticosteroid is related to its potency.
24 A) Inhibit DNA gyrase
Ciprofloxacin is a fluoroquinolone that has broad gram-positive and gram-negative bacterial activity by inhibiting DNA gyrase. Inhibition of protein synthesis by binding to 30S ribosomal subunit is the mechanism of action of tetracylines. Macrolide antibiotics (such as erythromycin) inhibit protein synthesis by binding to the 50S ribosomal subunit. Sulfonamides are competitive antagonists of p-aminobenzenesulfonamide, which disrupts the synthesis of folic acid.
25 B) 10%
Allergic reactions include local allergy, rash, itching, hives, bronchoconstrictive disease, and anaphylactic reactions that can be fatal. A strong history of serious allergy to penicillins is a contraindication to cephalosporin administration. Approximately 10% of patients with penicillin allergy will cross-react, making the use of cephalosporins dangerous in some cases.
26 A) Bactrim
Bactrim contains sulfamethoxazole together with trimethoprim. Methazolamide is a carbonic anhydrase inhibitor. Methazolamide is a sulfonamide derivative, and allergic cross-reactions may occur.
27 D) Cyclosporine—decreased tear production
All of the drugs and side effects are paired correctly except for topical cyclosporine (Restasis) and decreased tear production. Restasis is used to treat the inflammatory component of dry eye and has been shown to increase conjunctival goblet cells.
28 D) Mucor
Mucor typically requires antifungal therapy with amphotericin B in conjunction with aggressive surgical debridement.
29 D) Flucytosine
Acanthamoeba is a parasite that inhabits soil, water, and air. Risk factors for developing acanthamoeba keratitis include improper disinfection of contact lens and hot tube use. Agents that have been used include neomycin, natamycin, miconazole, propamidine, dibromopropamidine, PHMB, and chlorhexidine. Flucytosine is an antifungal agent that has been used in amebic encephalitis.
30 A) Hyperosmotic
Viscoelastics resist flow and deformation. They facilitate tissue manipulation and maintain intraocular space. For use within the eye, they must be inert, isosmotic, sterile, nonpyogenic, nonantigenic, and optically relatively clear. Many viscoelastics today are preparations of methylcellulose or sodium hyaluronate.
31 C) Procaine
Procaine has the shortest duration of action (30–60 minutes). Lidocaine lasts 1 to 2 hours, mepivacaine lasts 2 to 3 hours, and bupivacaine (Marcaine) lasts up to 8 to 12 hours.
32 B) Superior oblique
CN IV is located outside the muscle cone (annulus of Zinn) and is least likely to be affected by a retrobulbar block. It innervates the superior oblique muscle. CNs III and VI are located within the muscle cone and are therefore more likely to be anesthetized. CN III innervates superior rectus, medical rectus, inferior rectus, and inferior oblique. CN VI innervates the lateral rectus.
33 B) Olopatadine HCl—mast-cell stabilizer
The correct pair is olopatadine and mast-cell stabilizer and is also a H1 antagonist. Ketotifen is also a mast-cell inhibitor/H1 antagonist. Naphazoline is an antihistimine. Diclofenac is an NSAID.
34 D) Descemet membrane
PAS stain will highlight basement membranes. It is used to visualize the epithelial basement membrane and Descemet membrane. Descemet membrane is constantly laid down by the endothelial cells.
35 C) Aqueous layer
IgA is secreted into the lumen of the main and accessary lacrimal glands, which form the aqueous layer. It plays a role in host-defense mechanisms.
36 A) Glands of Wolfring
The aqueous component of the tear film is secreted by the main lacrimal gland, glands of Krause, and glands of Wolfring. The goblet cells secrete the mucin layer. The meibomian glands secrete the lipid layer with some contribution from the sebaceous glands of Zeis.
37 D) Long posterior ciliary nerves
Innervation to the cornea is via the first branch of the trigeminal nerve. Approximately 70 to 80 branches of the long posterior ciliary nerves enter the cornea peripherally after losing their myelin sheath 1 to 2 mm before the limbus.
38 A) Corneal wound healing—type III collagen
Type III collagen is associated with stromal wound healing. Type IV collagen is secreted by the endothelial cells in burst fashion, accounting for the thickening of Descemet membrane. The most prevalent collagen within the stroma is type I. Bowman layer consists of type I and V collagens.
39 B) 2 µl/min
Aqueous humor enters the posterior chamber through diffusion, ultrafiltration, and active secretion by the nonpigmented epithelium of the ciliary body. The rate of formation in people is 2 µl/min.
40 B) Calcium
Only calcium and phosphorus are in concentrations of about one-half that in plasma. Sodium, potassium, magnesium, iron, zinc, and copper all approximate levels found in plasma. Chloride and bicarbonate vary from 20% to 30% above or below plasma levels.
41 A) Pigment
The blood–aqueous barrier maintains the aqueous humor as a cell-free, protein-free ultrafiltrate. Red and white blood cells and fibrin are not normally present in the aqueous. Pigments can be released from the posterior iris in a condition such as pigment dispersion syndrome and does not necessarily indicate disruption of the blood–aqueous barrier.
42 B) α-Crystallin
α-Crystallin is the largest of the crystallins with a molecular mass in the range of 600 to 800 kDa. β- and γ-crystallins have a molecular mass from 23 to 32 kDa and 20 kDa, respectively.
43 A) Glutathione
Free radicals are highly reactive species that can lead to damage of lens fibers and subsequent opacification. Superoxide dismutase, glutathione, catalase, and vitamins C and E may be protective against oxidative damage. Vitamin A is essential in the retina and is involved in photoreceptor light transduction. Aldose reductase is involved in galactose metabolism and may be involved in the development of cataracts in diabetic patients.
44 B) Phakia
Various biochemical changes occur in the vitreous with age and disease. Among the causes of decreased concentration of hyaluronate are syneresis, myopia, aphakia, diabetes mellitus, and injury with hemorrhage, inflammation, or surgery.
45 D) 10 days
One of the most important functions of the RPE is phagocytosis of the outer segments of the photoreceptor. Each photoreceptor renews its outer segment every 10 days.
46 D) Phagocytosis of photoreceptor inner segments
The RPE serves many functions, including development of photoreceptors during embryogenesis; maintenance of the outer blood–retinal barrier; maintenance of the environment of the subretinal space; adhesion of the underlying sensory retina; selective transport of metabolites to and from the retina; uptake, transport, storage, metabolism, and isomerization of vitamin A; regeneration of the visual pigment rhodopsin; phagocytosis of photoreceptor outer segment tips; and stray light absorption by melanin granules.
47 B) 1,000 times more sensitive
The rods are 100 to 1,000 times more sensitive to light than the cones, allowing better vision in dim light. At this luminance level, the cones are not triggered; therefore, the world appears as shades of gray. Fine resolution of detail is hampered in this lighting condition because the rods are not concentrated in the fovea like the cones.
48 C) Zygomatic
The medial orbital wall is formed from the following four bones: frontal process of the maxilla, lacrimal bone, orbital plate of the ethmoid, and the lesser wing of the sphenoid.
49 A) Ophthalmic artery
The superior orbital fissure transmits the lacrimal nerve, frontal nerve, CN IV, and superior ophthalmic vein outside the annulus of Zinn. Within the annulus of Zinn, the superior orbital fissure transmits CN III, nasociliary nerve, sympathetic roots of ciliary ganglion, and CN VI. The ophthalmic artery travels with the optic nerve and the sympathetic fibers from the carotid plexus in the optic foramen.
50 D) Superior rectus
The superior division of CN III supplies the superior rectus and the levator. The inferior division of CN III supplies the medial rectus, inferior rectus, and inferior oblique. The superior oblique is supplied by CN IV.