Accommodation Convergence Reflex Flashcards

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.