B3.2 The Eye

• Iris.

  
• What happens to the radial and circular muscles when the pupil dilates?

  The radial muscles contract and the circular muscles relaxes.

  
• What is the fovea?

  The fovea is the point where light focuses on the retina.

  The region contains the highest concentration of cone cells and gives the sharpest image.
• Why is the iris reflex important?

  If too much light reaches the retina, it could get damaged.

  If too little light reaches the retina, we won't be able to see clearly.
• The circular muscle.

  
• The fovea.

  
• What are the two types of retinal cells in each eye? What is the role of each?

  1. Cone cells- allow us to see very precisely and detect colour.
  2. Rod cells- more sensitive, allowing us to see in the dark.
• Retina.

  
• What happens to the radial and circular muscles when the pupil constricts?

  The radial muscles relaxes and the circular muscles contracts.

  
• What is the iris reflex ?

  An automatic reflex that constricts or dilates the pupil in response to light.

  It allows the eye to control the amount of light that reaches the retina.
• The lens.

  
• A is constricted.

  B is dilated.

  
• The optic nerve.

  
• What is the role of the cornea and the lens?

  To refract (bend) light, so that it focuses on the fovea.
• Which two muscles are found in the iris?

  Radial and circular muscles.
• What is the process of accommodation in the eye?

  It changes the lens's refractive power
• Why do glasses help with accommodation issues?

  They provide additional refracting power
• Which parts of the eye are important for accommodation?

  Cornea and lens
• What role do the ciliary muscles and suspensory ligaments play?

  They control the shape of the lens
• How does the cornea contribute to vision?

  It refracts light consistently
• What happens to light rays from distant objects?

  They are almost parallel when hitting the eye
• Where must light be focused in the eye?

  On the fovea of the retina
• What shape does the lens take for nearby objects?

  Short and fat
• What occurs when the ciliary muscle contracts?

  It moves inwards towards the lens
• What happens to the suspensory ligaments when the ciliary muscle contracts?

  They slacken and become loose
• How does the lens change for distant objects?

  It stretches out to reduce curvature
• What is the medical term for long-sightedness?

  Hyperopia
• What is the medical term for short-sightedness?

  Myopia
• What type of lenses do glasses for long-sightedness use?

  Convex lenses
• What type of lenses do glasses for short-sightedness use?

  Concave lenses
• What happens when the lens refracts too much light?

  Light focuses before the retina
• What is the result of the lens not refracting enough light?

  Image appears behind the retina
• How do the functions of convex and concave lenses differ?

  Convex lenses add power; concave reduce power
• What is the effect of the ciliary muscle relaxing?

  It stretches the lens for distant vision
• What is the role of the suspensory ligaments?

  They hold the lens in place
• How does the lens change shape for nearby objects?

  It becomes fatter to refract more
• What is the primary function of the lens in the eye?

  To fine-tune light refraction
• What happens to the lens when focusing on a distant object?

  It flattens to reduce curvature
• What is the effect of light rays from nearby objects?

  They hit the eye at a wide angle
• What is the role of the cornea in focusing light?

  It refracts light before it hits the lens