Eyes Flashcards
Sclera
: Tough, protective white covering continuous with the cornea, which bends light rays to focus on the retina.
Corne
a: Transparent, sensitive to touch; contact triggers the corneal reflex:
o Afferent nerve: Trigeminal (CN V).
o Efferent nerve: Facial (CN VII).
Conjunctiva
: Transparent protective covering with two parts:
o Palpebral: Lines the eyelids.
o Bulbar: Covers the eyeball, merging with the cornea at the limbus.
Iris
Acts as a diaphragm, controlling pupil size for light adjustment.
Pupil
:
o Round, regular.
o Parasympathetic stimulation (CN III): Constriction.
o Sympathetic stimulation: Dilation.
Lens
Transparent disc behind the pupil; adjusts thickness for near (bulging) or far (flattening) focus.
Retin
a: Visual receptor layer, converts light into nerve impulses.
o Structures visible via ophthalmoscope: Optic disc, retinal vessels, background, macula
Direct reflex
: Constriction of exposed pupil.
o Consensual reflex: Constriction of opposite pupil due to synapse at the brain’s optic chiasm.
o Afferent nerve: Optic (CN II).
o Efferent nerve: Oculomotor (CN III).
Fixation
: Rapid eye movements focus on an object of attention. Impaired by fatigue, medications, or alcohol.
Accommodation
: Pupillary constriction and lens curvature adjustment for near vision.
Extraocular Muscles
- Cranial Nerves Controlling Eye Movement:
o CN VI (Abducens): Lateral rectus (abducts eye).
o CN IV (Trochlear): Superior oblique (downward and inward movement).
o CN III (Oculomotor): All other muscles (superior, inferior, medial rectus; inferior oblique).
Common Eye Disorders
- Age-Related Macular Degeneration (AMD):
o Breakdown of macular cells; loss of central vision.
o Leading cause of blindness in Canada; higher risk for women. - Cataracts:
o Lens opacity from protein clumping.
o Common in older adults (>70 years); risk factors include diabetes and steroid use. - Glaucoma:
o Increased intraocular pressure, optic nerve damage, peripheral vision loss.
o Chronic open-angle glaucoma is the most common form. - Diabetic Retinopathy:
o Leading cause of vision loss in younger populations.
o Regular screening is essential for diabetic patients.
Eye Examination Steps
- Visual Acuity:
o Snellen chart for distance vision.
o Near vision test for patients >40 years. - Visual Fields:
o Confrontation test to assess peripheral vision. - Extraocular Muscle Function:
o Corneal light reflex (Hirschberg’s test).
o Cover-uncover test.
o Diagnostic positions test to evaluate muscle strength. - External Structures:
o Inspect general appearance, eyebrows, eyelids, lashes, and eyeball alignment. - Anterior Structures:
o Check cornea, lens, iris, and pupils for size, shape, reflexes, and accommodation.
Social Determinants of Health and Vision
- Many Canadians lack access to affordable vision care.
- Limited provincial healthcare coverage for routine eye exams and corrective lenses.
- High-risk populations: People with diabetes, Indigenous communities, or African descent (higher glaucoma rates).
- Nurses should refer low-income individuals to free or reduced-cost services.
. Test Visual Acuity
- Snellen Eye Chart:
o Measures distance vision.
o Normal result: 20/20.
o Numerator = distance from chart; denominator = distance normal eye sees that line.
o If vision is poorer than 20/30, refer to an ophthalmologist. - Near Vision Test (for patients >40 or with difficulty reading):
o Use Jaeger card, held 14 inches from eyes.
o Normal result: 14/14.
o Moving the card farther away indicates presbyopia (aging-related reduced accommodation).
Test Visual Fields
- Confrontation Test:
o Compares patient’s peripheral vision to examiner’s.
o Normal angles: 50° upward, 90° temporal, 70° downward, 60° nasal.
o Loss of field may indicate glaucoma or retinal disorders.
Inspect Extraocular Muscle Function
- Corneal Light Reflex (Hirschberg’s Test):
o Shine light; reflection should be symmetrical on both corneas.
o Asymmetry indicates muscle weakness or strabismus. - Cover-Uncover Test:
o Detects misalignment.
o Normal: Uncovered eye remains fixed; no movement of covered eye when uncovered.
o Misalignment suggests phoria (mild weakness) or tropia (severe misalignment). - Diagnostic Positions Test:
o Move target through six cardinal positions of gaze.
o Normal: Smooth, parallel movement.
o Abnormal: Nystagmus (oscillating movements) or muscle weakness.
Inspect External Eye Structures
- General:
o Observe facial expression, mobility, and ability to avoid obstacles. - Eyebrows:
o Symmetrical movement; no scaling or lesions.
o Uneven movement may indicate nerve damage. - Eyelids and Lashes:
o Lid closure should be complete; lashes evenly distributed.
o Abnormalities: Ptosis (drooping), ectropion (outward rolling), or entropion (inward rolling). - Eyeball Alignment:
o Aligned in socket; no protrusion (exophthalmos) or sunken appearance (enophthalmos). - Conjunctiva and Sclera:
o Conjunctiva should be clear; sclera white or slightly grey-blue in darker-skinned individuals.
o Abnormal: Redness (conjunctivitis), jaundice (yellow sclera). - Lacrimal Apparatus:
o No swelling or redness; tear drainage system intact.
o Blockage indicated by excessive tearing or fluid regurgitation.
. Inspect Anterior Eyeball Structures
- Cornea and Lens:
o Smooth, clear surface with no cloudiness.
o Abnormalities: Corneal abrasion or cataracts (lens opacity). - Iris and Pupil:
o Iris: Flat, round, evenly colored.
o Pupils: Equal, round, reactive to light and accommodation (PERRLA).
o Normal size: 3–5 mm.
o Abnormalities: Unequal pupils (anisocoria), dilated pupils (mydriasis), or constricted pupils (miosis). - Pupillary Light Reflex:
o Direct: Constriction of illuminated pupil.
o Consensual: Constriction of opposite pupil.
o Absent reflex suggests CNS injury. - Accommodation:
o Normal: Pupillary constriction and inward movement of eyes for near focus.
