Eye
- Introduction
• The eye is the organ of vision located in the orbital cavity.
• It detects light and converts it into electrical signals sent to the brain for image formation.
• Protected by bones of the orbit and cushioned by fat. - Structure of the Eye
A. Outer Layer (Fibrous Tunic)
• Sclera: white, tough outer layer providing shape and protection.
• Cornea: transparent front part allowing light to enter and refract (bend) the light.
B. Middle Layer (Vascular Tunic or Uvea)
• Choroid: pigmented layer rich in blood vessels, nourishes retina.
• Ciliary body: contains muscles that control lens shape for focusing, and suspensory ligaments that hold the lens.
• Iris: colored part of the eye, controls pupil size to regulate light entry.
• Pupil: central opening in the iris where light passes into the eye.
C. Inner Layer (Nervous Tunic)
• Retina: light-sensitive layer containing photoreceptor cells:
• Rods: detect light intensity, important in dim light.
• Cones: detect color and detail in bright light.
• Converts light into electrical impulses. - Internal Components
• Lens: transparent, flexible structure that focuses light onto the retina.
• Aqueous humor: clear fluid between cornea and lens; nourishes and maintains intraocular pressure.
• Vitreous humor: jelly-like substance filling the eyeball behind the lens; maintains shape.
• Optic nerve: transmits visual information from retina to brain. - Eye Muscles and Movement
• Six extrinsic muscles control eye movement: superior, inferior, lateral, and medial rectus; superior and inferior oblique.
• Controlled by cranial nerves III, IV, and VI.
• Allow precise movements and coordination for binocular vision. - Functions of the Eye
• Light refraction: cornea and lens focus incoming light.
• Image formation: light focused on retina, photoreceptors convert to impulses.
• Vision processing: impulses sent by optic nerve to brain to create images.
• Pupil regulation: iris controls light intensity entering the eye.
• Accommodation: ciliary muscles adjust lens for near and far vision. - Common Disorders
• Cataract: opacity of the lens causing blurry vision.
• Glaucoma: increased intraocular pressure damaging optic nerve.
• Conjunctivitis: inflammation of the conjunctiva (pink eye).
• Myopia and hyperopia: refractive errors causing blurred vision.
• Age-related macular degeneration (ARMD): deterioration of central retina leading to vision loss. - Nursing Considerations
• Assess visual acuity and eye health regularly.
• Educate on eye protection and hygiene.
• Assist with medication administration like eye drops.
• Prepare patients for eye exams and surgeries.
• Monitor for signs of infection or increased intraocular pressure.
• Support patients with visual impairment adapting to daily life. - Summary for Quick Review
The eye is a complex organ with three layers: fibrous (sclera and cornea), vascular (choroid, ciliary body, iris), and nervous (retina). Light is focused by the cornea and lens onto the retina, where photoreceptors convert it into nerve impulses sent to the brain. The iris controls light entry by adjusting pupil size. Eye movement is controlled by six muscles. Nursing care includes assessment, education, assisting treatments, and supporting patients with eye conditions.