Accommodation Convergence Reflex Flashcards

Questions and Answers

What is accommodation physiology?

When focusing on a nearby object, ciliary muscles contract and zonule fibres relax, releasing tension from the lens, allowing internal elasticity to form a clearer image on the retina.

What does convergence physiology refer to?

Inward movement of both eyes caused by bilateral contraction of medial recti, which helps maintain a focused image on each fovea for binocular vision.

What is miosis physiology?

Decreased diameter of the pupil via constriction of iris sphincter muscles innervated by the parasympathetic nervous system.

Describe the afferent visual pathway.

Optic nerve -> optic chiasm -> optic tract -> lateral geniculate nucleus in the thalamus -> optic radiation -> visual cortex. Signup and view all the answers

What is the efferent pathway in visual reflexes?

It involves afferent fibres from the lateral geniculate nucleus projecting to the Edinger-Westphal nucleus to synapse with the oculomotor nerve and parasympathetic nerves. Signup and view all the answers

What is the swinging flashlight test?

A test involving shining a light into one eye and quickly moving it to the other to compare direct light reflex and consensual reflex between both eyes. Signup and view all the answers

What does RAPD stand for?

Relative Afferent Pupillary Defect. Signup and view all the answers

What does the presence of RAPD imply?

Disease of the optic nerve between the retina and chiasm. Signup and view all the answers

What are some causes of RAPD?

Optic nerve diseases such as optic neuritis, nerve compression from tumors, direct optic damage, or retinal diseases like large retinal detachment and severe macular degeneration. Signup and view all the answers

What is the clinical significance of retinal eye disease in relation to RAPD?

Although severe retinal disease can cause RAPD, this is unusual since the pupillary light reflex is sensitive to even small amounts of light detected by the retina. Signup and view all the answers

Study Notes

Accommodation Physiology

Ciliary muscles contract when focusing on near objects.
Zonule fibers relax, reducing tension on the lens, preventing it from flattening.
Internal elasticity of the lens increases curvature, aiding in clearer retinal images.

Convergence Physiology

Inward eye movement occurs through bilateral medial recti contraction.
Oculomotor nerve innervates these muscles.
This process preserves focused images on each fovea and enhances binocular vision.

Miosis Physiology

Miosis refers to the constriction of the pupil, reducing its diameter.
Constriction is achieved via iris sphincter muscles, which are innervated by the parasympathetic nervous system.

Afferent Visual Pathway

Sequence: optic nerve → optic chiasm → optic tract → lateral geniculate nucleus (thalamus) → optic radiation → visual cortex.
This pathway is crucial for sensory input related to vision.

Efferent Pathway in Visual Reflexes

Small proportion of afferent fibers from the lateral geniculate nucleus project to the Edinger-Westphal nucleus.
Synapses occur with the oculomotor nerve for convergence and parasympathetic nerves for accommodation and miosis.
Functions include eye convergence/divergence through rectus muscles, pupillary constriction via sphincter pupillae, and lens accommodation via ciliary muscles.

Swinging Flashlight Test

Involves alternating light between eyes to assess pupillary reflexes.
Direct light reflex in one eye is compared to consensual reflex in the other to evaluate afferent pathways.
Detection of RAPD indicates a weaker afferent pathway in one eye.

RAPD (Relative Afferent Pupillary Defect)

Defined as a comparative analysis of the pupillary response of both eyes.
Indicates sensory pathway dysfunction.
Normal response shows equal pupil constriction when light is shone; RAPD results in less constriction in the affected eye.

Presence of RAPD Implication

Suggestive of optic nerve disease occurring between the retina and optic chiasm.

Causes of RAPD

Optic nerve diseases include:
- Optic neuritis.
- Nerve compression from tumors.
- Direct damage from trauma or radiation.
Retinal diseases can also lead to RAPD:
- Large retinal detachment.
- Severe macular degeneration.

Clinical Significance of Retinal Eye Disease

Although RAPD can result from severe retinal disease, it is rare as the pupillary light reflex is sensitive to even minimal light detected by the retina.

Description

These flashcards cover the physiology of the accommodation and convergence reflexes, detailing the mechanisms involved in focusing on nearby objects. Learn about the role of ciliary muscles, zonule fibers, and the processes that enhance visual clarity on the retina.