Vision and Ophthalmology Optics and Refraction 1 — Questions and Answers
Question 1: A patient who is myopic has a far point located:
- At infinity
- Behind the retina
- In front of the eye at a finite distance (Correct answer)
- At the cornea
Correct answer: In front of the eye at a finite distance
A myopic eye is too long or too powerful, focusing parallel rays in front of the retina; the far point is at a finite distance in front of the eye.
Question 2: Which type of lens is used to correct myopia?
- Convex (plus) lens
- Concave (minus) lens (Correct answer)
- Plano lens
- Bifocal lens only
Correct answer: Concave (minus) lens
Concave (diverging, minus) lenses diverge light rays before they enter the eye, effectively moving the focal point back onto the retina in myopic patients.
Question 3: Presbyopia results from decreased ability of the lens to:
- Absorb UV light
- Accommodate (change shape) for near vision (Correct answer)
- Maintain transparency
- Rotate in the eye
Correct answer: Accommodate (change shape) for near vision
Presbyopia occurs due to age-related loss of lens elasticity and ciliary muscle effectiveness, reducing the amplitude of accommodation needed for near focus.
Question 4: In a spherocylindrical lens, the power is equal in all meridians in which component?
- Cylinder only
- Sphere only (Correct answer)
- Both sphere and cylinder
- Neither
Correct answer: Sphere only
The spherical component of a lens has equal power in all meridians, while the cylindrical component adds power in only one meridian to correct astigmatism.
Question 5: What does the term 'axis' refer to in a cylindrical lens prescription?
- Direction of maximum power
- Direction of no power (plano meridian) (Correct answer)
- Optical center of the lens
- Diameter of the lens
Correct answer: Direction of no power (plano meridian)
The axis in a cylinder prescription specifies the meridian of no cylindrical power (the plano meridian), perpendicular to which the full cylinder power acts.
Question 6: Anisometropia refers to a significant difference in refractive error between:
- Near and distance vision in the same eye
- The two eyes (Correct answer)
- Morning and evening measurements
- Horizontal and vertical meridians
Correct answer: The two eyes
Anisometropia is a condition where the two eyes have significantly different refractive errors, which can lead to amblyopia if uncorrected in childhood.
Vision and Ophthalmology Optics and Refraction 1
A patient who is myopic has a far point located: