NCLEX Review Guide: Diagnostic Tests for the Eye

Snellen Chart Assessment

• The Snellen chart measures visual acuity at a distance of 20 feet, with normal vision recorded as 20/20. The first number represents the testing distance, while the second number indicates the distance at which a person with normal vision can read the same line.
• Visual acuity worse than 20/200 in the better eye with correction is considered legal blindness. Document results for each eye separately, testing the right eye first, then left eye, followed by both eyes together.

Tonometry Testing

• Tonometry measures intraocular pressure (IOP) to screen for glaucoma, with normal pressure ranging from 12-21 mmHg. The test uses either contact tonometry (requires topical anesthesia) or non-contact air-puff tonometry.
• Elevated IOP above 21 mmHg indicates potential glaucoma and requires immediate ophthalmologic referral. Instruct clients to avoid rubbing eyes after the procedure if topical anesthesia was used.

Ophthalmoscopy

• Direct ophthalmoscopy allows visualization of the retina, optic disc, and blood vessels through the pupil. The examiner uses an ophthalmoscope held close to the client's eye in a darkened room.
• Mydriatic drops may be instilled to dilate pupils for better visualization, causing temporary blurred vision and light sensitivity lasting 3-4 hours. Clients should not drive until effects wear off completely.

Fluorescein Angiography

• This procedure involves IV injection of fluorescein dye followed by rapid sequential photographs of the retina to assess blood flow and detect abnormalities. The dye causes temporary yellow discoloration of skin and bright yellow-green urine for 24-48 hours.
• Monitor for allergic reactions including nausea, vomiting, and rarely anaphylaxis during and immediately after dye injection. Ensure IV access is patent and emergency equipment is readily available.

1. Obtain informed consent and allergy history
2. Insert IV line for dye administration
3. Instill mydriatic drops for pupil dilation
4. Position client comfortably for photography
5. Inject fluorescein dye rapidly via IV
6. Take sequential retinal photographs
7. Monitor for adverse reactions throughout

Optical Coherence Tomography (OCT)

• OCT is a non-invasive imaging technique that provides cross-sectional images of retinal layers, similar to ultrasound but using light waves instead of sound. It's particularly useful for diagnosing macular degeneration and diabetic retinopathy.
• The procedure requires no special preparation and takes approximately 10-15 minutes per eye. Clients sit upright and focus on a target while the machine scans the retina with infrared light.

Common Pitfalls

• Never instill mydriatic drops in clients with narrow-angle glaucoma - this can precipitate an acute attack by blocking aqueous humor drainage.
• Remember that fluorescein dye discolors urine bright yellow-green for 1-2 days - this is normal and expected, not a sign of kidney problems.
• Visual acuity testing requires proper distance (20 feet) and adequate lighting - incorrect setup leads to inaccurate results.