COT - Certified Ophthalmic Technician Refraction and Retinoscopy Questions and Answers — Questions and Answers
Question 1: When performing retinoscopy with the sleeve down (Plano mirror effect), you observe "with" motion. What type of lens power should be added to the phoropter to neutralize this reflex?
- Plus sphere (Correct answer)
- Minus sphere
- Plus cylinder
- Minus cylinder
Correct answer: Plus sphere
With the retinoscope's sleeve in the down position, which creates a plano mirror effect, 'with' motion indicates the patient's far point is behind their retina (hyperopia) or behind the examiner. To neutralize this, plus (converging) lens power is added to move the far point forward to the examiner's plane.
Question 2: A patient is undergoing retinoscopy from a working distance of 67 cm. The gross retinoscopy finding in the phoropter is +3.50 D sphere. What is the patient's net (final) refractive error?
- +5.00 D
- -1.50 D
- +2.00 D (Correct answer)
- +3.50 D
Correct answer: +2.00 D
To find the net refractive error, the working distance must be subtracted from the gross retinoscopy finding. The dioptric equivalent of the working distance is calculated by taking the inverse of the distance in meters (1 / 0.67m ≈ 1.50 D). Therefore, +3.50 D (gross) - 1.50 D (working distance) = +2.00 D (net).
Question 3: During retinoscopy, you notice that the reflex in the 90-degree meridian is thin and moves quickly, while the reflex in the 180-degree meridian is wider and moves more slowly. Which of the following does this most likely indicate?
- Spherical refractive error
- High myopia
- Media opacity like a cataract
- Astigmatism (Correct answer)
Correct answer: Astigmatism
Astigmatism is characterized by different refractive powers in different meridians. This causes the retinoscopic reflex to vary in width, brightness, and speed as the streak is rotated. A spherical error would have a consistent reflex in all meridians. While high myopia would have a slow-moving reflex, it would be consistent across meridians unless astigmatism is also present.
Question 4: A technician is performing retinoscopy on a new patient and finds the reflex to be very dim and slow-moving. Which of the following is the most likely cause for these findings?
- A small refractive error
- A high refractive error (Correct answer)
- The patient is accommodating
- The retinoscope sleeve is in the wrong position
Correct answer: A high refractive error
A high refractive error causes the light rays to be far from neutralized, resulting in a retinoscopic reflex that is dim, wide, and slow-moving. As lenses are added and neutrality is approached, the reflex becomes brighter, narrower, and faster. Accommodation would cause the reflex to fluctuate, not necessarily be dim and slow.
Question 5: Which of the following is the primary purpose of retinoscopy in a clinical setting?
- To measure the intraocular pressure
- To assess the health of the retina
- To determine a subjective starting point for refraction
- To obtain an objective measurement of the patient's refractive error (Correct answer)
Correct answer: To obtain an objective measurement of the patient's refractive error
Retinoscopy is an objective method, meaning it does not require responses from the patient. It is used to determine the patient's refractive error by observing how light is reflected from the retina, providing a reliable starting point for the subjective refraction.
Question 6: A prescription written by an ophthalmologist is +1.00 +1.50 x 090. How would this prescription be written in minus cylinder form for the optical lab?
- -0.50 -1.50 x 180
- +1.00 -1.50 x 180
- +2.50 -1.50 x 180 (Correct answer)
- +1.50 +1.00 x 180
Correct answer: +2.50 -1.50 x 180
To transpose a prescription from plus to minus cylinder form: 1) Add the sphere and cylinder powers to get the new sphere (+1.00 + +1.50 = +2.50). 2) Change the sign of the cylinder (+1.50 becomes -1.50). 3) Change the axis by 90 degrees (90 becomes 180). The transposed prescription is +2.50 -1.50 x 180.
COT - Certified Ophthalmic Technician Refraction and Retinoscopy Questions and Answers
When performing retinoscopy with the sleeve down (Plano mirror effect), you observe "with" motion.
What type of lens power should be added to the phoropter to neutralize this reflex?