ABO NOCE Basic Opticianry Ocular Anatomy and Physiology Questions and Answers 5 — Questions and Answers
Question 1: The precorneal tear film's outermost lipid layer is secreted by:
- Goblet cells
- Lacrimal gland
- Meibomian glands (Correct answer)
- Crypts of Henle
Correct answer: Meibomian glands
The meibomian (tarsal) glands secrete the lipid layer of the tear film, which retards evaporation of the underlying aqueous layer.
Question 2: When viewing a near object, the visual axes of both eyes converge. This convergence is controlled primarily by which muscles?
- Lateral recti
- Medial recti (Correct answer)
- Superior recti
- Inferior obliques
Correct answer: Medial recti
Both medial rectus muscles adduct the eyes simultaneously to produce convergence during near fixation.
Question 3: Which photopigment is found in rod photoreceptors?
- Erythrolabe
- Chlorolabe
- Rhodopsin (Correct answer)
- Cyanolabe
Correct answer: Rhodopsin
Rods contain rhodopsin (visual purple), a photopigment maximally sensitive to wavelengths around 498 nm and critical for scotopic (dim-light) vision.
Question 4: The anterior chamber depth is the distance between the:
- Cornea and the iris/lens plane (Correct answer)
- Iris and the anterior vitreous face
- Lens posterior pole and the retina
- Sclera and the choroid
Correct answer: Cornea and the iris/lens plane
Anterior chamber depth (ACD) is measured from the posterior corneal surface (endothelium) to the anterior iris or lens surface.
Question 5: The pars plana is a clinically important structure because it is the preferred site for:
- Measuring intraocular pressure
- Intravitreal injections and vitrectomy incisions (Correct answer)
- Laser trabeculoplasty
- Gonioscopy examination
Correct answer: Intravitreal injections and vitrectomy incisions
The pars plana is avascular and has no neurosensory retina, making it the safest entry point for intravitreal injections and vitrectomy trocars.
Question 6: Zonular fibers (zonules of Zinn) extend from the ciliary body to which structure?
- Posterior surface of the iris
- Capsule of the crystalline lens (Correct answer)
- Anterior vitreous face
- Corneal limbus
Correct answer: Capsule of the crystalline lens
Zonular fibers attach from the ciliary processes to the lens capsule (equatorial region), suspending the lens and transmitting ciliary muscle forces during accommodation.
Question 7: Which of the following correctly describes the pathway of aqueous humor through the eye?
- Posterior chamber → pupil → anterior chamber → trabecular meshwork → Schlemm's canal (Correct answer)
- Anterior chamber → pupil → posterior chamber → ciliary body
- Vitreous → posterior chamber → pupil → anterior chamber
- Choroid → ciliary body → anterior chamber → pupil
Correct answer: Posterior chamber → pupil → anterior chamber → trabecular meshwork → Schlemm's canal
Aqueous is secreted into the posterior chamber by the ciliary body, flows through the pupil into the anterior chamber, and drains via the trabecular meshwork into Schlemm's canal.
ABO NOCE Basic Opticianry Ocular Anatomy and Physiology Questions and Answers 5
The precorneal tear film's outermost lipid layer is secreted by: