Overview
The eye focuses light through the cornea and lens onto the retina, where rods (dim light, peripheral vision) and cones (color, sharp central vision) convert it into signals carried by the optic nerve. The optic nerves meet at the optic chiasm, where fibers from the inner half of each retina cross.
The ear has three parts. The outer ear collects sound; the middle ear (eardrum and three ossicles) amplifies it; the inner ear holds the cochlea for hearing and the vestibular apparatus for balance. This 3D model shows the eye and its muscles in detail and the external ear; the middle and inner ear are explained in the text.
Main functions
- Vision: focusing light and detecting color and movement
- Hearing: converting sound waves into nerve impulses
- Balance: sensing head position and movement
- Taste and smell, which also protect against spoiled food and toxic fumes
- Tear production and drainage to protect the eye
Key structures
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Eye (eyeball)
The organ of vision: a fluid-filled sphere that focuses light onto the retina.
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Cornea and lens
The two transparent structures that focus light on the retina.
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Retina and optic nerve
The light-sensing layer of the eye and the nerve that carries vision to the brain.
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Extraocular muscles
Six small muscles that move each eye precisely together.
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Ear
The organ of hearing and balance, with outer, middle and inner parts.
From light to sight
Light passes through the cornea, aqueous humor, pupil, lens and vitreous body before reaching the retina. The cornea does most of the focusing; the lens fine-tunes it by changing shape (accommodation). Aqueous humor is produced constantly and drains through the angle between the iris and cornea, which keeps eye pressure stable.
Sound vibrates the eardrum, the ossicles (malleus, incus, stapes) pass the vibration to the oval window, and fluid waves in the cochlea bend hair cells that trigger the auditory nerve.
Nursing assessment
- Visual acuity with a Snellen chart at 20 feet, one eye at a time; 20/20 is normal.
- Pupils: equal, round, reactive to light and accommodation (PERRLA).
- Extraocular movements in the six cardinal fields of gaze (cranial nerves III, IV and VI).
- Otoscopic exam: pull the pinna up and back in adults, down and back in children under 3.
- Whisper test, Weber and Rinne tests to screen hearing loss.
Common conditions
| Condition | What happens | Key signs | Nursing priorities |
|---|---|---|---|
| Glaucoma | Raised intraocular pressure damages the optic nerve | Open-angle: painless gradual loss of peripheral vision. Angle-closure: sudden severe eye pain, halos, nausea (emergency) | Lifelong eye drops, avoid anticholinergic drugs with angle-closure risk, report sudden pain |
| Cataract | Clouding of the lens | Blurred vision, glare, faded colors | After surgery avoid bending, lifting and rubbing the eye; report sudden pain or vision loss |
| Macular degeneration | Damage to the macula | Loss of central vision; straight lines look wavy | Low-vision aids, safety, teach Amsler grid monitoring |
| Retinal detachment | The retina separates from the back of the eye | Floaters, flashes of light, a curtain over the vision | Emergency referral; restrict activity as prescribed |
| Otitis media | Middle ear infection, common in children | Ear pain, fever, bulging red eardrum, tugging at the ear | Pain control, antibiotics when indicated, teach about bottle-feeding upright and smoke exposure |
| Ménière's disease | Excess fluid in the inner ear | Episodes of vertigo, tinnitus, hearing loss and ear fullness | Fall precautions during attacks, low-sodium diet, move slowly |
Labs and normal values
| Test | Typical adult range | Why it matters |
|---|---|---|
| Intraocular pressure | 10–21 mmHg | Higher values are associated with glaucoma |
| Visual acuity | 20/20 | 20/200 or worse in the better eye with correction is legal blindness in the US |
| Hearing threshold | 0–25 dB | Higher thresholds indicate hearing loss |
Reference ranges differ between laboratories and textbooks. Use the values your program and facility use.
Exam tips
- Instill eye drops into the conjunctival sac, then apply gentle pressure on the inner corner (nasolacrimal duct) for 1–2 minutes to limit systemic absorption.
- Wait at least 5 minutes between different eye drops.
- Ear drops for adults: pull the pinna up and back; for children under 3: down and back.
Practice questions
8 NCLEX-style questions on the eye & ear system. Pick an answer to see the rationale.
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A client reports sudden severe eye pain, blurred vision with halos around lights and nausea. The nurse suspects:
Show the answer and rationale
Answer B: Acute angle-closure glaucoma. Angle-closure glaucoma is an emergency: intraocular pressure rises suddenly, causing pain, halos and nausea.
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How should the nurse straighten the ear canal to give ear drops to a 2-year-old?
Show the answer and rationale
Answer B: Pull the pinna down and back. In children under 3 the canal is directed upward, so the pinna is pulled down and back.
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Which cranial nerve controls the lateral rectus muscle?
Show the answer and rationale
Answer C: VI (abducens). LR6 SO4: lateral rectus is CN VI, superior oblique is CN IV, the others are CN III.
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After instilling eye drops, why does the nurse press on the inner corner of the eye?
Show the answer and rationale
Answer B: To reduce systemic absorption through the nasolacrimal duct. Punctal occlusion keeps the medication in the eye and limits absorption into the bloodstream.
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Which symptom suggests retinal detachment?
Show the answer and rationale
Answer B: Flashes of light, floaters and a curtain over the vision. Retinal detachment is an emergency marked by sudden flashes, floaters and a shadow or curtain.
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Which medication requires monitoring for ototoxicity?
Show the answer and rationale
Answer B: Gentamicin. Aminoglycosides can damage the inner ear; report tinnitus, vertigo or hearing loss.
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A chemical splashes into a client's eye. What is the first action?
Show the answer and rationale
Answer B: Irrigate the eye immediately with water or saline. Immediate, prolonged irrigation limits chemical damage to the cornea.
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A pituitary tumor pressing on the optic chiasm typically causes:
Show the answer and rationale
Answer B: Bitemporal hemianopia. Fibers from the nasal half of each retina, which see the temporal fields, cross at the chiasm and are compressed first.