Which structure of the eye is helpful in changing the thickness of the lens?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2019

Applied Anatomy

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2019

Explanation

The Ciliary Body is a ring of muscle and tissue inside the eye that is connected to the lens.
It contains the ciliary muscles, which are responsible for changing the shape of the lens.
When the ciliary muscles contract, tension on the suspensory ligaments is released, allowing the elastic lens to become thicker (more convex).
This process, called accommodation, increases the refractive power of the lens to focus on near objects.
Parasympathetic nerve stimulation causes the ciliary muscle to contract.

Option A: The Sclera is the tough, white, fibrous outer layer of the eyeball. Its primary function is to provide structural support and protection to the inner parts of the eye, not to change the lens shape.
Option B: The Cornea is the transparent front part of the eye that covers the iris and pupil. While it is the primary refractive surface of the eye (providing about two-thirds of the eye's focusing power), its curvature is fixed and it does not change shape to adjust focus.
Option D: The Iris is the colored part of the eye. Its function is to control the diameter of the pupil, thereby regulating the amount of light that reaches the retina. It does not play a role in changing the thickness of the lens.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and physiology of the eye, specifically the mechanism of accommodation as background academic context rather than a clinical decision trigger.
Understanding accommodation is crucial for diagnosing and managing refractive errors. The age-related decline in this function, known as presbyopia, is a common reason for patients seeking eye care.
Certain medications, known as cycloplegics (e.g., atropine, cyclopentolate), work by paralyzing the ciliary muscle. This prevents accommodation and also dilates the pupil (mydriasis), which is useful during eye examinations to get a clear view of the retina.
A nurse may assess accommodation as part of a basic neurological assessment by asking a patient to focus on a distant object and then shift their focus to a near object (like a pen). The nurse observes for pupillary constriction and convergence of the eyes, which are part of the accommodation reflex.

How to Approach the Question

This is a factual recall question based on anatomy and physiology.
First, identify the key function described in the question stem: 'changing the thickness of the lens'.
Recall the primary function of each structure listed in the options.
Sclera: Protection and structure.
Cornea: Fixed refraction of light.
Ciliary Body: Contains muscles to change lens shape (accommodation).

Concept Tested & Keywords

Concept Tested: Anatomy and physiology of the eye, specifically the mechanism of accommodation.
Stem keywords: structure of the eye, helpful, changing the thickness, lens
Lead-in keywords: Which
Negative lead-in flag: false