Introduction
Assessment of visual acuity is one of the most common procedures performed by an ophthalmologist. It helps to identify visual problems.
Definition
Visual acuity is a measure of the ability of the eye to distinguish shapes and the details of objects at a given distance, the smallest letters that can be read by the patient in a standardized chart kept at a distance of 6 m or 20 feet.
Purposes
- To identify refractive errors.
- To prescribe the spectacles for correction of vision.
- To monitor ocular health.
- To identify retinal disorders.
- To assess any change in vision.
- To measure the outcome of cataract or other eye surgeries.
Types of Charts Used to Assess Visual Acuity
- Snellen
- Random E
Indication
- To provide a baseline recording of visual acuity.
Articles
1) Preparation of the Equipment
| Articles | Purpose |
| Snellen chart | To check visual acuity. |
| Laser pointers | To point out letters. |
| Occluder card/patch | To estimate improvement in visual acuity. |
| Pinhole occluder | To evaluate visual acuity in cataract. |
| Near vision chart | To check near vision. |
2) Preparation of the Patient
- Check visual acuity, first without spectacles and then with correction spectacles.
- Always test the worst eye first to ensure that the letters are not memorized by the patient.
Procedure
| Nursing Action | Rationale | |
| 1. | Explain the procedure to the patient. | Allays anxiety and gains cooperation from the patient. |
| 2. | Obtain informed consent from the patient. | Serves as legal evidence.Prevents litigation of staff. |
| 3. | Testing visual acuity for distance | |
| Position the patient in a comfortable seat at a distance of 20 feet (6 m) from the chart. | General preparation before the procedure. | |
| Instruct the patient to cover one eye with the palm of the hand and then read the chart from top to bottom till the letter beyond which clarity is lost. | To test the function of cranial nerve II. | |
| If the patient cannot read even the topmost line which contains the largest letters, bring him or her closer by 1 m at a time until the top letters can be seen. | To identify the refractive error. | |
| Repeat the whole procedure for the second eye. | ||
| 4. | Testing visual acuity for near vision | |
| Ask the patient to sit with his or her back toward light. | To enhance comfort. | |
| Ask the patient to read a magazine or newspaper held at the distance of 14 inches (35 cm). | To identify near vision problems. | |
| Instruct the patient to use corrective lens or spectacles during the test and try reading the chart/reading card again. | To check specific distance vision. | |
| Note the near vision as per the letter read. | To identify any abnormalities. | |
| Repeat the test for the other eye. | To identify any abnormalities in the other eye. | |
| 5. | Color vision testing method | |
| Instill the eye drops as per the physician’s order. | To dilate pupils. | |
| Position the patient sitting on a chair. | To enhance comfort. | |
| Ask the patient to cover one eye. | To test each eye separately. | |
| Assess color vision in each eye separately, using Ishihara plates. | To identify any abnormalities. | |
| Ask the patient to read the numbers on the plates. | To assess contrast sensitivity. | |
| If the patient is able to read the first test plate, move through all the plates and ask him or her to identify the number on each plate; if the patient is unable to read, document the findings. | To identify any abnormalities. | |
| 6. | Document the procedure | |
| Record the date, time, and patient’s response. | Serves as legal evidence and prevents duplication of care. | |
Special Considerations
- Be patient and allow extra time for responses.
- Collaborate with speech therapists or caregivers when needed.
- Use symbol-based charts (e.g., Tumbling E or Landolt C) for patients who cannot read Roman letters.
- Confirm understanding of the task before starting the test.
- Ensure consistent lighting, minimal glare, and a quiet setting.
- Maintain the standard testing distance (usually 6 meters or 20 feet) unless using a modified chart.
- Always test with and without the patient’s glasses or contacts.
- Document whether the acuity was measured unaided, with correction, or pinhole.
- Test each eye separately before testing both eyes together.
- Cover the non-tested eye completely but comfortably.
- Consider how vision affects daily activities (e.g., reading, mobility, medication management).
- A patient may have 20/20 acuity but still struggle with contrast sensitivity or depth perception.
REFERENCES
- Annamma Jacob, Rekha, Jhadav Sonali Tarachand: Clinical Nursing Procedures: The Art of Nursing Practice, 5th Edition, March 2023, Jaypee Publishers, ISBN-13: 978-9356961845 ISBN-10: 9356961840
- Omayalachi CON, Manual of Nursing Procedures and Practice, Vol 1, 3 Edition 2023, Published by Wolters Kluwer’s, ISBN: 978-9393553294
- Sandra Nettina, Lippincott Manual of Nursing Practice, 11th Edition, January 2019, Published by Wolters Kluwers, ISBN-13:978-9388313285
- Adrianne Dill Linton, Medical-Surgical Nursing, 8th Edition, 2023, Elsevier Publications, ISBN: 978-0323826716
- Donna Ignatavicius, Medical-Surgical Nursing: Concepts for Clinical Judgment and Collaborative Care, 11th Edition ,2024, Elsevier Publications, ISBN: 978-0323878265
- Lewis’s Medical-Surgical Nursing, 12th Edition,2024, Elsevier Publications, ISBN: 978-0323789615
- AACN Essentials of Critical Care Nursing, 5th Ed. Sarah. Delgado, 2023, Published by American Association of Critical-Care Nurses ISBN: 978-1264269884
- Ernstmeyer K, Christman E, editors. Nursing Fundamentals [Internet]. 2nd edition. Eau Claire (WI): Chippewa Valley Technical College; 2024. PART IV, NURSING PROCESS. Available from: https://www.ncbi.nlm.nih.gov/books/NBK610818/
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