Head to Toe: eyes

Learning Outcomes

  • 13.1: Describe the anatomy and physiology of the eyes.

  • 13.2: Identify the anatomic, physiologic, developmental, psychosocial, and cultural variations that guide assessment of the eyes.

  • 13.3: Determine which questions about the eyes to use for the focused interview.

  • 13.4: Outline the techniques for assessment of the eyes.

  • 13.5: Generate the appropriate documentation to describe the assessment of the eyes.

  • 13.6: Identify abnormal findings in the physical assessment of the eyes.

Structures of the External Eye

  • Palpebra (eyelid): Site where conjunctiva merges with cornea.

  • Caruncle: A small, fleshy growth within the inner corner of the eye.

  • Eyebrow: Provides protection and reduces sweat entering eyes.

  • Pupil: The opening that allows light to enter the eye.

  • Sclera: The white outer covering of the eyeball, covered with conjunctiva.

  • Medial canthus: The inner corner where the upper and lower lids meet.

  • Iris: The colored part of the eye; regulates the amount of light entering through the pupil.

  • Outer canthus: The outer corner where the upper and lower lids meet.

  • Palpebral fissure: The space between the eyelids.

  • Eyelashes: Protect the eyes from foreign particles.

The Outermost Layer of the Eye

  • Sclera:

    • Description: Tough, protective, white covering of the eyeball.

  • Cornea:

    • Description: Transparent part of the eye that refracts (bends) light rays to focus them on the retina.

The Middle Layer of the Eye

  • Choroid: Vascular layer providing nourishment to the outer retina.

  • Iris: Controls the size of the pupil and consequently the amount of light that enters the eye.

  • Pupil: The adjustable opening in the center of the iris.

  • Optic Disc: The region at the back of the eye where the optic nerve connects, leading to a lack of photoreceptors (blind spot).

  • Lens: Flexible structure that changes shape to help focus light on the retina.

  • Blood Vessels: Provide nutrients and oxygen to eye tissues.

The Inner Layer of the Eye

  • Retina:

    • Description: The inner layer of the eye where light waves convert into nerve impulses.

  • Optic Disc:

    • Description: Located nasally; point of exit for the optic nerve.

  • Retinal Vessels: Supply the retina with blood.

  • Macula:

    • Description: Located on the temporal side; responsible for detailed vision. Features the fovea centralis, which is a pit-like center and appears as a hyperpigmented spot on the retina.

Refraction of the Eye

  • Emmetropia:

    • Definition: A normal refractive condition where the light rays focus directly on the retina.

  • Myopia (Nearsightedness):

    • Definition: Condition where light rays focus in front of the retina.

  • Hyperopia (Farsightedness):

    • Definition: Condition where light rays focus behind the retina.

  • Astigmatism:

    • Definition: Condition where light rays are spread over a wide area rather than focusing on a single point.

Visual Reflexes

  • Pupillary Light Reflex:

    • Definition: The normal constriction of pupils when a bright light shines on the retina.

  • Accommodation:

    • Definition: The adaptation of the eye for near vision, involving changes in lens shape.

Visual Pathways

  • Process: An external object is perceived by the eye, creating an image, which is then transported to the brain for interpretation as vision.

  • Light refraction structures: Cornea, aqueous humor, anterior and posterior chambers, lens, and vitreous humor bend light waves onto the retina.

  • Optic Nerve (Cranial Nerve II): Conducts the retinal image to the brain. At the optic chiasm, fibers cross over and join temporal fibers from the opposite eye.

Accessory Structures of the Eye

  • Eyebrow: Protects the eyes.

  • Eyelids: Protect and maintain moisture.

  • Palpebral Fissure: The slit between lids.

  • Medial Canthus & Outer Canthus: The corners of the eye.

  • Meibomian Glans: Produce oils for the tear film.

  • Eyelashes: Act as barriers to debris.

  • Conjunctiva: Membrane covering the sclera.

  • Lacrimal Apparatus: Responsible for tear production and drainage.

Extraocular Muscles

  • Function: Six muscles controlling the eyeball's movement:

    • Lateral Rectus (Cranial nerve VI): Moves eye laterally.

    • Medial Rectus (Cranial nerve III): Moves eye medially.

    • Superior Rectus (Cranial nerve III): Elevates eye.

    • Inferior Rectus (Cranial nerve III): Depresses eye.

    • Inferior Oblique (Cranial nerve III): Elevates and turns eye outward.

    • Superior Oblique (Cranial nerve IV): Depresses and turns eye outward.

Special Considerations: Aging Adults

  • Pupil Size: Decreases with age.

  • Common Visual Conditions:

    • Presbyopia: Age-related difficulty in focusing on near objects.

    • Cataracts: Clouding of the lens affecting vision.

    • Visual Acuity: Often decreases with age.

  • Major Causes of Decreased Visual Function:

    • Cataract Formation: Leads to opacification of the lens.

    • Glaucoma: A condition of increased intraocular pressure damaging the optic nerve.

    • Age-related Macular Degeneration (AMD): A progressive disease causing loss of central vision.

    • Diabetic Retinopathy: Damage to retinal blood vessels due to diabetes leading to impairment in vision.

Culture and Genetics

  • Variability: Culturally based differences exist in iris color and retinal pigmentation.

  • Cataracts: Leading cause of blindness globally.

  • Increased Risk with Age: Incidence of glaucoma and age-related macular degeneration rises with age.

  • Visual Impairment: Can differ significantly across ethnic groups due to genetic predispositions and environmental factors.

Subjective Cues

  • Personal History: Include previous eye conditions and any surgeries.

  • vision aids: Information on glasses, contact lenses, and protective eyewear usage.

  • Eye Examination Timeline: Last office visit for an eye exam.

  • Medications: Review relevant medications that may impact eye health.

  • Vision Difficulties: Questions regarding decreasing acuity, blurring, blind spots, strabismus (crossed eyes), and diplopia (double vision).

Vision Difficulty Questions

  • Inquire about any difficulty seeing, blurring, blind spots (whether sudden or gradual), and presence in one or both eyes.

    • Copy of specific questions includes:

    • Any halos, rainbows, rings around objects?

    • Movement of spots observed?

    • Presence of night blindness?

Pain Questions

  • Questions regarding eye pain should explore:

    • Sudden onset?

    • Description of pain: burning, itching, sharp, stabbing, or associated with bright light?

    • Sensations of foreign bodies or deep aching?

Objective Cues Preparation

  • Positioning: For vision screening, position a person initially standing, then sitting with head at eye level.

  • Required Equipment:

    • Snellen eye chart to measure visual acuity.

    • Handheld visual screener (Jager card or similar).

    • Opaque card or occluder to test one eye at a time.

    • Penlight for light reflex testing.

    • Applicator stick and ophthalmoscope for deeper inspection.

General Inspection

  • Inspect for overall appearance including eyebrows, eyelids and lashes, and eyeballs.

Abnormal Findings: Lesions on the Eyelids

  • Blepharitis: Inflammation of eyelid margins.

  • Basal Cell Carcinoma: A common type of skin cancer affecting the eyelid.

  • Hordeolum: Also known as a stye, an infection of an oil gland in the eyelid.

Abnormal Findings: Eyelid Abnormalities

  • Periorbital Edema: Swelling around the eyes.

  • Exophthalmos: Protrusion of the eyes affecting comfort and vision.

  • Ptosis: Drooping of the upper eyelid.

  • Ectropion: Outward turning of the lower eyelid.

  • Entropion: Inward turning of the lower eyelid.

Conjunctiva and Sclera Examination

  • During examination, observe color changes, swelling, or lesions while looking for ethnic variations.

Abnormal Findings: Sclera, Cornea, and Lens

  • Conjunctivitis: Inflammation of conjunctiva leading to redness and discharge.

  • Hemorrhages: Presence of blood in conjunctival or scleral areas.

  • Cataracts: Clouding of the lens affecting visual clarity.

  • Ulcers: Corneal perforations resulting from various injuries or infections.

Lacrimal Apparatus

  • Examination includes asking the person to look down while inspecting lids for redness or swelling.

  • Puncta normally drain tears into the lacrimal sac; this is tested manually.

Testing Distance Vision

  • Snellen alphabet chart: Commonly used measure of visual acuity.

    • Recording Format: Results are recorded as a fraction, numerator being the distance of the client from the chart and denominator the distance from which an individual with normal vision would read it.

    • Normal vision is represented as 20/20.

Abnormalities during Vision Testing

  • In case of difficulty seeing even the largest letters, reduce the distance to the chart until it can be seen and record that new distance, e.g., 10/20 (indicating myopia if unable to see 20/20).

  • Legally Blind is defined as 20/200.

Test Near Vision

  • Determine near vision using a handheld vision screener with variable print sizes (e.g., a Jaeger card), held 12-14 inches from the patient.

  • Record the smallest line the patient can read, normal being 14/14; if unable to read a line, note the previous line (e.g., 10/14).

Confrontation Test

  • Measure gross peripheral vision by covering one eye and comparing it with your own peripheral vision at eye level.

  • Conduct this by directing the person to stare straight ahead while you introduce a target from various peripheral directions, prompting them to signal once they see it.

  • Abnormal Finding: Loss of peripheral vision.

Cardinal Fields of Gaze Testing

  • Conduct a test of extraocular movements (EOM) by moving a penlight in six cardinal positions to assess for muscle weakness, nystagmus, or lid lag.

Abnormal Findings: Cardinal Fields of Gaze

  • Esophoria: Inward turning of the eye.

  • Exophoria: Outward turning of the eye.

  • Nystagmus: Involuntary eye twitching movement.

Abnormal Findings: Visual Fields (Age-Related Changes)

  • Glaucoma: Damage to the optic nerve due to increased intraocular pressure.

  • Macular Degeneration: Narrowing and degeneration of blood vessels, leading to decreased macular effectiveness and central vision loss.

Cover/Uncover Test

  • Procedure: Cover one eye, observe the uncovered eye, and then remove the cover while observing the eye movement to confirm focus straight ahead; repeat for the other eye.

Accommodation Testing

  • Testing Method: Hold an object 4 inches from the patient's nose and move it closer while observing for pupil constriction and convergence.

  • Abnormality: Lack of constriction or convergence signifies potential neurological issues.

Cornea and Lens Examination

  • Shine a light from the side across the cornea to check for smoothness and clarity; assess the corneal surface for irregularities.

  • Note any opacities in the cornea, anterior chamber, or lens behind the pupil.

Corneal Light Reflex

  • Also called the Hirschberg Test: Assess eye axes alignment by shining light toward the eyes and examining the reflection's symmetry on both corneas.

Corneal Reflex

  • Test by touching the sclera with a cotton ball or applicator; the normal response is tearing or blinking of the eye.

Iris and Pupil Examination

  • Observe the iris for a flat, regular shape and even coloration.

  • Conduct the pupillary light reflex test in a dim room and observe for constriction during direct and consensual light exposure.

Abnormal Findings: Pupillary Response

  • Impaired Pupillary Response: Indicates potential neurological damage; might include conditions such as anisocoria (unequal pupil size, potentially benign or indicative of CNS issues), mydriasis (fixed and dilated pupils), and miosis (fixed and constricted pupils).

Inspection of Ocular Fundus

  • Utilize an ophthalmoscope to magnify and inspect the anterior chamber, lens, vitreous humor, and the internal retina.

  • Diopter Measurement: Lenses control focus with positive numbers for nearer objects and negative numbers for farther objects.

Ocular Fundus Examination Method

  1. Darken the examination room; select a large round aperture with white light.

  2. Start from 25 cm away at a 15-degree angle to the line of vision.

  3. Observe for red reflex; proceed closer to the eye while maintaining the focus.

Inspection of Optic Disc

  • Characteristics to evaluate include:

    • Color of the Disc: Normal is creamy yellow-orange, with distinct margins.

    • Shape: Contours should be smooth.

    • Margins: Should be well-defined.

    • Cup-Disc Ratio: Evaluates the health of the optic nerve

Retinal Vessels Examination

  • Follow paired arteries and veins out to the periphery in four quadrants, noting any abnormalities along the course of these vessels.

Diabetic Retinopathy

  • Refers to changes in the retina and its vasculature including:

    • Microaneurysms: Small bulges in the blood vessels of the retina.

    • Hemorrhages: Leakage of blood into the retina indicating bleeding.

    • Macular Edema: Swelling in the macula area affecting vision.

    • Retinal Exudates: Deposits in the retina that reflect retinal damage.

Hypertensive Retinopathy

  • Indicates changes in the retina due to high blood pressure, including:

    • Flame Hemorrhages: Linear blood spots.

    • Nicking of Vessels: Seen at crossing points where arteries and veins intersect.

    • Cotton Wool Spots: Soft, white patches on the retina indicative of nerve fiber infarction.

Abnormal Findings: Fundus Examination

  • Age-related Macular Degeneration (ARMD): A degenerative condition of the macula leading to gradual loss of central vision while peripheral vision is preserved. Risk factors include hypertension and smoking; protective factors include a diet rich in fruits and vegetables.