CPO Ophthalmic Optics and Dispensing 1 — Questions and Answers
Question 1: Which type of lens is used to correct myopia?
- Plano lens
- Concave lens (Correct answer)
- Convex lens
- Cylindrical lens
Correct answer: Concave lens
A concave lens is used to correct myopia, also known as nearsightedness. Myopia occurs when light focuses in front of the retina, and a concave lens diverges the light rays before they enter the eye, effectively pushing the focal point back onto the retina for clear vision.
Question 2: What does a prescription with "+2.00" in the sphere indicate?
- The patient has astigmatism.
- The patient has hyperopia. (Correct answer)
- The patient has myopia.
- The patient requires a prism correction.
Correct answer: The patient has hyperopia.
A prescription with "+2.00" in the sphere indicates that the patient has hyperopia, or farsightedness. A plus (+) power lens is convex, meaning it converges light rays, which is necessary to bring the focal point forward onto the retina when light naturally focuses behind it.
Question 3: What is the primary purpose of the pupillary distance (PD) measurement?
- To determine the patient's refractive error
- To align lenses properly in glasses (Correct answer)
- To measure intraocular pressure
- To detect visual field defects
Correct answer: To align lenses properly in glasses
The primary purpose of the pupillary distance (PD) measurement is to ensure that the optical centers of the lenses in a pair of glasses are precisely aligned with the patient's pupils. Correct PD alignment is crucial for comfortable vision, preventing prismatic effects that can cause eye strain, headaches, or distorted vision.
Question 4: What is a progressive addition lens (PAL)?
- A lens with no prescription power
- A multifocal lens with a visible line
- A lens with a gradient power for distance, intermediate, and near vision (Correct answer)
- A single-vision lens
Correct answer: A lens with a gradient power for distance, intermediate, and near vision
A progressive addition lens (PAL) is a multifocal lens that provides a seamless, gradient power transition for distance, intermediate, and near vision without visible lines. This design allows individuals with presbyopia to see clearly at all distances through a single pair of glasses.
Question 5: Which lens material is most impact-resistant and often recommended for children?
- Glass
- CR-39
- Polycarbonate (Correct answer)
- High-index
Correct answer: Polycarbonate
Polycarbonate is the lens material most impact-resistant and is frequently recommended for children, sports eyewear, and safety glasses. Its superior durability and shatter resistance provide excellent protection against impacts, making it a safer choice for active individuals.
CPO Ophthalmic Optics and Dispensing 1
Which type of lens is used to correct myopia?