NBEO Ocular Anatomy & Physiology 2 — Questions and Answers
Question 1: What are rods and cones?
- Photoreceptor cells in the retina: rods detect dim light (scotopic vision) and cones detect color and detail (photopic vision) (Correct answer)
- Types of surgical instruments
- Parts of the lens
- Blood vessel types in the retina
Correct answer: Photoreceptor cells in the retina: rods detect dim light (scotopic vision) and cones detect color and detail (photopic vision)
Rods (120 million, peripheral retina) provide night vision and motion detection. Cones (6 million, concentrated in the macula) provide color vision and fine detail in bright light.
Question 2: What is the vitreous humor?
- A clear gel filling the posterior cavity of the eye that maintains the eye's shape and holds the retina in place (Correct answer)
- The fluid in the anterior chamber
- A type of tear film
- The liquid inside the lens
Correct answer: A clear gel filling the posterior cavity of the eye that maintains the eye's shape and holds the retina in place
The vitreous is a transparent gel (99% water with collagen and hyaluronic acid) that maintains the globe's shape, transmits light to the retina, and provides metabolic support. With age, it liquefies and can cause floaters.
Question 3: What is the tear film and what are its layers?
- A three-layer film (lipid, aqueous, mucin) covering the cornea that provides lubrication, nutrition, and protection (Correct answer)
- A single layer of water on the cornea
- A surgical membrane
- A contact lens coating
Correct answer: A three-layer film (lipid, aqueous, mucin) covering the cornea that provides lubrication, nutrition, and protection
The tear film has three functional components: the outer lipid layer (prevents evaporation), the middle aqueous layer (provides nutrition and defense), and the inner mucin layer (helps tears adhere to the corneal surface).
Question 4: What is the pupillary light reflex?
- The automatic constriction of the pupil in response to increased light intensity, mediated by the parasympathetic nervous system (Correct answer)
- Dilation of the pupil in bright light
- The production of tears in bright light
- Blinking in response to bright light
Correct answer: The automatic constriction of the pupil in response to increased light intensity, mediated by the parasympathetic nervous system
The pupillary light reflex constricts both pupils (direct and consensual response) when light stimulates retinal photoreceptors, controlled by the parasympathetic pathway through the oculomotor nerve (CN III).
Question 5: What is accommodation?
- The ability of the eye to change the shape of the crystalline lens to focus on objects at different distances (Correct answer)
- The adjustment of pupil size
- The movement of the eye to track moving objects
- The adaptation of the retina to different light levels
Correct answer: The ability of the eye to change the shape of the crystalline lens to focus on objects at different distances
Accommodation involves ciliary muscle contraction releasing zonular tension, allowing the elastic lens to become more convex for near focus. This ability decreases with age (presbyopia) as the lens loses flexibility.
Question 6: What are the extraocular muscles and how many are there?
- Six muscles that control eye movement: four rectus muscles (superior, inferior, medial, lateral) and two oblique muscles (superior, inferior) (Correct answer)
- Two muscles: up and down
- Three muscles controlling the iris
- Eight muscles surrounding the orbit
Correct answer: Six muscles that control eye movement: four rectus muscles (superior, inferior, medial, lateral) and two oblique muscles (superior, inferior)
Six extraocular muscles precisely control each eye's movement in all directions. Dysfunction of these muscles or their cranial nerve innervation (CN III, IV, VI) causes strabismus and diplopia.
NBEO Ocular Anatomy & Physiology 2
What are rods and cones?