CPOA Basic Science 2 — Questions and Answers
Question 1: Which layer of the cornea serves as the primary barrier against infection and is responsible for most corneal sensation?
- Bowman's layer
- Stroma
- Epithelium (Correct answer)
- Descemet's membrane
Correct answer: Epithelium
The corneal epithelium is the outermost layer and acts as the first line of defense against pathogens while containing most of the cornea's sensory nerve endings.
Question 2: The aqueous humor is produced by which ocular structure?
- Choroid
- Ciliary body (Correct answer)
- Iris
- Trabecular meshwork
Correct answer: Ciliary body
The ciliary body's non-pigmented epithelium actively secretes aqueous humor into the posterior chamber.
Question 3: What is the approximate pH of normal tears?
- 6.5
- 7.0
- 7.4 (Correct answer)
- 8.0
Correct answer: 7.4
Normal tears have a pH of approximately 7.4, which is slightly alkaline and similar to blood plasma.
Question 4: The fovea centralis is located within which larger retinal landmark?
- Optic disc
- Macula lutea (Correct answer)
- Ora serrata
- Peripapillary region
Correct answer: Macula lutea
The fovea centralis is the central pit within the macula lutea and is responsible for the sharpest central vision.
Question 5: Which cranial nerve controls the superior oblique extraocular muscle?
- CN III (Oculomotor)
- CN IV (Trochlear) (Correct answer)
- CN V (Trigeminal)
- CN VI (Abducens)
Correct answer: CN IV (Trochlear)
Cranial nerve IV (trochlear) is the sole innervator of the superior oblique muscle, which intorts and depresses the eye.
Question 6: The process by which the eye adjusts focus from a distant object to a near object is called:
- Convergence
- Accommodation (Correct answer)
- Vergence
- Refraction
Correct answer: Accommodation
Accommodation is the process by which the ciliary muscle contracts and the lens increases its curvature to focus on near objects.
Question 7: Which type of photoreceptor cell is responsible for color vision and functions best in bright light?
- Rods
- Cones (Correct answer)
- Ganglion cells
- Bipolar cells
Correct answer: Cones
Cones are concentrated in the macula and fovea, are responsible for color discrimination, and function under photopic (bright light) conditions.
CPOA Basic Science 2
Which layer of the cornea serves as the primary barrier against infection and is responsible for most corneal sensation?