Vision Lab Overview

Definition: Visual acuity is the ability to see objects clearly.
Prevalence: More than half of the population experiences visual acuity problems.
Eye Components: - Pupil: Regulates the amount of light that enters the eye.
- Lens: Focuses light and changes shape to adjust focusing power, producing a sharp image on the retina.
- Accommodation: The process of the lens becoming rounder to focus on near objects.
Age Factor: As we age, the ability of the lens to accommodate decreases due to decreased elasticity.

Requirements: If wearing glasses or contact lenses, remove them prior to testing.
Test Method: Use the Snellen chart. Visual acuity is expressed as (20/x), where (x) is the number of the last line correctly read. - Normal Vision: 20/20
- Less than Normal Vision: Less than a ratio of 1 (e.g., 20/40)
- Better than Normal Vision: 20/15, indicating the ability to see at 20 feet what a normal eye sees at 15 feet.

Definition: Astigmatism is a common vision condition characterized by blurred vision due to an uneven curvature of the cornea or lens.
Impact: Nearly half of those wearing corrective lenses are affected, leading to headaches, squinting, or eye pain.

Definition: Color blindness results from one or more types of cones being non-functional, often affecting red-green perception due to genetic factors linked to the X chromosome, making it more common in males.
Types: Complete colorblindness allows vision only in black, white, and shades of gray; it affects about 1 in a million males.

Definition: The optic disc lacks photoreceptors, creating a blind spot where no image is focused. The brain compensates for this by filling in details based on adjacent photoreceptor light.

To find the blind spot size on the retina (s), use ( $s = (d*D)/distance$ ), where 'd' is the distance between marked spots on paper, and 'D' is the distance from the eye.

Definition: The near point indicates how close an object can be while still in focus. A near point of 25 cm or greater suggests accommodation issues.

Definition: The pupillary light reflex involves pupil constriction in response to light, primarily through the iris sphincter muscle contraction.
Responses: The direct response occurs in the eye receiving light; the consensual response is in the opposite eye due to optic nerve fiber crossing.

Purpose: Measures peripheral and reading vision ranges using a field vision disk.

Definition: Eye dominance refers to the tendency of individuals to prefer visual input from one eye over the other.

Close one eye:
- If the object remains in view, you are right eye dominant.
- If the object moves, you are left eye dominant.
Record the dominant eye.

Definition: The activity measures response time to visual stimuli, involving several neural processes from environmental stimulus transduction to muscle contractions.

Purpose: The ophthalmoscope allows a non-invasive examination of the retina, significant for assessing eye health and spotting disorders such as diabetes, hypertension, and atherosclerosis.