In-Depth Notes on Eye Anatomy, Vision Assessment, and Management

Discoloration of the Eye

  • The white part of the eye (sclera) can become discolored.
    • Yellowing (jaundice) may indicate liver impairment.

Eye Structures and Muscles

  • The eye contains extraocular muscles that facilitate movement.
    • These muscles allow for eye movement and eyelid control.
    • Nerve damage can impair movement and affect gaze.
  • The eye can be divided into outer and inner structures:
    • Outer Structures:
    • Sclera: Tough protective layer.
    • Cornea: Clear, protective layer that helps focus light.
    • Inner Structures:
    • Neural components receiving visual information and sending it to the brain, including the retina and optic nerve.

Blood Supply and Nerve Involvement

  • The eye has vascular structures (middle layer) including arteries and veins.
    • Problems with blood supply can lead to vision issues.
  • The optic nerve is crucial for transmitting information from the retina to the brain.

Vision Assessment Techniques

  • Ocular History: Understanding vision problems, pain, discharge, and self-treatment history.
  • Visual Acuity Testing:
    • Snellen Chart: Tests distance vision. 20/20 is considered normal.
    • A person can see what a normal person sees at 20 feet.
    • Rosenbaum Pocket Screener: Tests near vision.
    • Finger Count/Hand Motion Test: Used when the Snellen chart is not visible to the patient.
  • If a patient cannot see clearly at 20 feet, the results may be noted as finger count (CF) or hand motion (HM).

External Structures Assessment

  • Inspect eyelids and conjunctiva for irritation, inflammation, and abnormalities.
  • Scleral discoloration may suggest systemic issues like jaundice.

Pupillary Response Assessment

  • Eyes should react to light, indicating proper nerve function.
  • Direct vs. indirect examination:
    • Direct: Examiner is at eye level.
    • Indirect: Using handheld lenses from a distance.

Specialized Testing Procedures

  • Slit Lamp Examination: Provides a detailed view of the anterior eye structures.
  • Amsler Grid: Used to detect distortions indicating macular degeneration.
  • Perimetry Testing: Assesses peripheral vision capacity.

Refractive Errors

  • Conditions that affect eyesight and can be corrected by lenses:
    • Emmetropia: Normal vision.
    • Myopia: Nearsightedness. Eye is elongated, causing trouble seeing far away.
    • Hyperopia: Farsightedness. Eye is shortened, causing trouble seeing up close.
    • Astigmatism: Irregular curvature of the cornea causing distortion.

Low Vision and Blindness

  • Legal blindness qualifies as having visual acuity of 20/200 or worse.
  • Important to assess functional impact:
    • Difficulty with activities of daily living (ADLs).
    • Challenges with reading, driving, and medication management.

Adaptation for Patients with Low Vision

  • Modify environment to minimize hazards and enhance safety:
    • Remove trip hazards.
    • Ensure necessary items (glasses, call light) are within reach.
    • Use the clock method for describing food placement.
  • Communication should be clear and respectful, considering the patient's ability and dignity.

Administering Ophthalmic Medications

  • Eye drops must be treated like medications, requiring attention to cleanliness and personal usage.
    • Do not share eye medications between patients.
  • Absorption struggles:
    • The eye's protective structures limit drug absorption.
  • Topical medications:
    • Ointments may retain better than drops due to their consistency.

Special Medications in Ophthalmology

  • Mydriatics: Used to dilate pupils for examination.
  • Cycloplegics: Paralyze pupil reactions, aiding clearer visualization during examinations.
    • Contraindications include narrow angles to avoid complications like glaucoma.
  • Anti-infectives: Target infections, can have side effects similar to oral antibiotics.
  • Anti-inflammatories: Such as corticosteroids may have long-term risks including increased intraocular pressure if used excessively.