Free ABO NOCE MCQ Question and Answers — Questions and Answers
Question 1: How is the strength of a lens measured?
- Add power
- Diopters (Correct answer)
- Prisms
- Microns
Correct answer: Diopters
The strength or optical power of a lens is measured in diopters (D). One diopter is defined as the reciprocal of the focal length in meters (D = 1/f). A higher diopter value indicates a stronger lens that converges or diverges light more significantly, providing the necessary correction for refractive errors.
Question 2: What is the 400 mm focal length lens' dioptric strength?
- -2.50
- +2.50 (Correct answer)
- +0.25
- +4.00
Correct answer: +2.50
To calculate the dioptric strength, first convert the focal length from millimeters to meters: 400 mm = 0.4 meters. Then, use the formula Diopters = 1 / focal length (in meters). So, D = 1 / 0.4 = +2.50 D. The positive sign indicates a converging (plus) lens, which is typical for a lens with a real focal point.
Question 3: What component of the prescription for eyeglasses serves as a gauge for the patient's myopia or hyperopia?
- Axis
- Add power
- Cylinder
- Sphere (Correct answer)
Correct answer: Sphere
The 'sphere' component of an eyeglass prescription indicates the spherical power needed to correct myopia (nearsightedness, represented by a minus sign) or hyperopia (farsightedness, represented by a plus sign). This power is uniform across all meridians of the lens and addresses the overall focusing error of the eye, bringing images into clear focus on the retina.
Question 4: What always happens to light beams that pass through a "plus" lens?
- Disperse
- Diverge
- Converge (Correct answer)
- Cohere
Correct answer: Converge
A 'plus' lens, also known as a convex lens, is thicker in the center and thinner at the edges. Its primary function is to converge parallel light rays to a single focal point. This converging action is used to correct hyperopia (farsightedness) by bringing the focal point forward onto the retina, allowing for clear vision.
Question 5: What is the term for the distance between the inside surface of a corrective lens and the surface of the eye?
- Sagittal depth
- Seg drop
- Vertex distance (Correct answer)
- Fitting cross
Correct answer: Vertex distance
Vertex distance is the measurement from the back surface of the spectacle lens to the apex of the cornea. This measurement is crucial, especially for higher prescriptions, because changes in vertex distance can affect the effective power of the lens at the eye. Accurate measurement ensures the prescribed power functions as intended, providing optimal vision correction.
Question 6: A form of lens having an extremely steep curve in a tiny core section and a flat carrier edge was one of the earliest treatments for severe hyperopia. What kind of lens was this referred to as?
- Lenticular (Correct answer)
- Corrected-curve
- Myodisc
- Meniscus
Correct answer: Lenticular
A lenticular lens is a type of lens designed to reduce thickness and weight for very high prescriptions, particularly for severe hyperopia (aphakia). It features a central optical zone with the full corrective power, surrounded by a flatter, non-optical carrier portion. This design minimizes the overall lens volume while maintaining the necessary optical correction, making the lenses more manageable.
Question 7: Which UV light range causes sunburns the most frequently?
- 100 nanometers to 290 nanometer
- 10 nanometers to 100 nanometers
- 290 nanometers to 320 nanometers (Correct answer)
- 320 nanometers to 400 nanometers
Correct answer: 290 nanometers to 320 nanometers
The UV light range from 290 nm to 320 nm corresponds to Ultraviolet B (UVB) radiation. UVB rays are primarily responsible for sunburns, skin reddening, and are a major contributor to skin cancer and cataracts. While UVA (320-400 nm) also contributes to skin damage, UVB is significantly more potent in causing acute skin damage like sunburn.
