(1) Development And Epidemiology Of Refractive Errors

Question 1

Two types of refractive STATUS

Answer 1

Emmetropia (perfect) and Ametropia

Question 2

Causes of myopia and correcting lens

Answer 2

• optical power greater than necessary
• eyeball elongated
• neg

Question 3

Myopia signs and symptoms

Answer 3

• Difficulty seeing distant objects
• squinting to see clearly
• headaches and eye strains

Question 4

Causes of hyperopia and correcting lens

Answer 4

• optical power lower than necessary
• eyeball length reduced
• pos

Question 5

Hyperopia signs and symptoms

Answer 5

• difficulty in concentrating on tasks at near
• poor reading ability
• headaches, tired eyes, eye strain

Question 6

Astigmatism causes

Answer 6

• light entering eye doesn’t focus on one spot of retina
• two principal meridians have different refractive powers hence producing 2 focal lines/images
• change in corneal curvature

Question 7

Astigmatism signs and symptoms

Answer 7

• blurry distance and near vision
• squinting
• irritation
• headache, tired eyes, eye strain

Question 8

Two types of astigmatism

Answer 8

1. Regular (2 PM perpendicular to each other)

2. Irregular (2 PM not perpendicular/ more than 2 PM or NO PM)

Question 9

Explain With the rule (regular astigmatism)

Answer 9

• power of vertical M > horizontal M

- axis of correcting cyl lens is 180 (+/- 30)

Question 10

Explain against the rule (reg astigmatism)

Answer 10

• power of the horizontal M > vertical M

- axis of correcting cyl lens is 90(+/-30)

Question 11

Explain oblique (reg astigmatism)

Answer 11

• power of the stronger M is neither horizontal nor vertical
• axis of correcting cyl lens is 45 (+/-15) or 135 (+/-15)

Question 12

Classifying astigmatism

Answer 12

• simple (one on ret, one not)
• compound (neither on ret but both on same side)
• mixed (one on either side)