L17 Flashcards
(14 cards)
What is visual acuity (VA) used to assess in clinical practice?
It’s a key indicator of ocular health, used to assess the impact of refractive error, and serves as an occupational standard.
Why is it important to measure VA immediately after history and symptoms?
To assess habitual VA and identify visual changes before other clinical procedures.
What is the purpose of distance vision testing?
To evaluate the ability to resolve fine detail, typically using charts designed to subtend specific angular sizes at specific distances.
Why is testing distance (6m in UK) important?
It’s far enough not to stimulate accommodation and provides standardised results.
What is the minimum angle of resolution (MAR)?
The angular size of the smallest detail that can be resolved in an optotype, typically 1 minute of arc for a 6/6 letter.
What is the Snellen chart and one of its main problems?
A widely used chart where letters subtend 5 mins of arc; problems include non-linear scaling and inconsistent letter legibility.
What are crowding effects in visual acuity testing?
Visual interference caused by neighbouring letters that make identification harder, especially in patients with poor vision.
What is the LogMAR chart and its advantage?
A visual acuity chart using a logarithmic scale, providing uniform letter spacing and size progression for better reliability.
Why is visual acuity assessed to threshold?
To ensure the smallest detail the patient can see is recorded, which may reveal more subtle deficits.
What alternative distance VA tests exist for non-verbal or illiterate patients?
Landolt C, Tumbling E, Sheridan-Gardiner, Kay Picture Test, and Cardiff Acuity Cards.
What is preferential looking and when is it used?
A method to assess vision in infants or non-verbal patients by noting preference for patterned vs. plain stimuli, e.g., Teller Acuity Cards.
What are examples of near visual acuity charts?
Faculty of Ophthalmologists’ booklet, Bailey-Lovie near card, Jaeger booklet, MacClure reading book.
Why are near vision tests important for patients over 40?
To detect symptoms of presbyopia and assess functional reading ability.
What are considerations when using near charts?
Preferred reading distance must be measured; high-contrast text may not reflect real-world reading challenges.
