Definition: Visual acuity is the sharpness or clarity of vision.
Snellen's chart consists of lines of decreasing size with the same number of letters in each line.
The patient is asked to read the line that they can see clearly from a distance of 6 meters.
The visual acuity is expressed as a fraction, with the numerator being the distance at which the patient can read the line clearly and the denominator being 6 meters.
Example: 6/6 indicates that the patient can read the line at 6 meters clearly, while 6/60 indicates that the patient can read the line at 60 meters.
Limitations: Snellen's chart is not suitable for patients with low vision or those who are unable to read.
Pinhole Test
Definition: The pinhole test is a simple and non-invasive technique used to assess visual acuity.
Procedure:
1 → The patient is asked to read the Snellen's chart with the pinhole device in front of their eyes.
2 → The pinhole device reduces the area of the pupil, which helps to improve the sharpness of vision.
3 → The patient's visual acuity is measured with the pinhole device in place.
Interpretation:
If the visual acuity improves with the pinhole device, it indicates that the patient has a refractive error (e.g., myopia, hyperopia).
If the visual acuity does not improve, it may indicate a non-refractive error (e.g., cataract, glaucoma).
Near Vision using Times New Roman Chart
Definition: Times New Roman chart is used to assess near vision.
Procedure:
1 → The patient is asked to read the Times New Roman chart at a distance of 40 cm.
2 → The patient's near visual acuity is measured and expressed as a fraction (e.g., N20, N10).
Limitations: Times New Roman chart is not suitable for patients with low vision or those who are unable to read.
Colour Vision using Ishihara Plates
Definition: Ishihara plates are used to assess colour vision.
Procedure:
1 → The patient is shown the Ishihara plate and asked to identify the number or shape.
2 → The patient's colour vision is assessed and expressed as a numerical value (e.g., 0, 1, 2, etc.).
Limitations: Ishihara plates are not suitable for patients with severe colour vision deficiency.
Additional Points
Pathology: Visual acuity can be affected by various pathological conditions, such as cataracts, glaucoma, and age-related macular degeneration.
Types: Visual acuity can be classified into different types, such as monocular (one eye) and binocular (both eyes).
Clinical Features: Visual acuity can be affected by various clinical features, such as refractive errors, astigmatism, and amblyopia.
Investigations: Visual acuity can be assessed using various investigations, such as Snellen's chart, pinhole test, and Ishihara plates.
Complications: Poor visual acuity can lead to various complications, such as decreased quality of life, increased risk of accidents, and decreased productivity.
Management: Visual acuity can be improved through various management strategies, such as refractive surgery, cataract surgery, and vision therapy.
Treatment: Visual acuity can be treated with various treatments, such as glasses, contact lenses, and medications.
Homoeopathic Therapeutic Medicines
Aconitum: Used to treat eye strain and blurred vision.
Belladonna: Used to treat eye inflammation and conjunctivitis.
Calcarea Carbonica: Used to treat eye fatigue and dryness.
Graphites: Used to treat eye irritation and itching.
Hydrocotyle: Used to treat eye inflammation and conjunctivitis.