On performing retinoscopy using a plane mirror in a patient who has a spherical refractive error of -3D with +2D cylindrical refractive error in 90 degree from a distance of 1 m, the reflex would move
## **Core Concept**
Retinoscopy, also known as skiascopy, is a technique used to objectively determine the refractive error of the eye. The examiner shines a light into the patient's eye and observes the reflection. The movement of the reflex (or shadow) within the pupil provides information about the refractive error. A plane mirror is used in retinoscopy to reflect light back into the eye.
## **Why the Correct Answer is Right**
In retinoscopy, when the light reflex moves in the opposite direction to the movement of the retinoscope, it indicates myopia (nearsightedness). The patient's spherical refractive error is -3D, indicating myopia. The cylindrical error of +2D at 90 degrees indicates hyperopia (farsightedness) in the vertical meridian. However, the overall reflex movement is primarily influenced by the spherical error. From a distance of 1 meter, for a myopic eye, the reflex would move "against" the retinoscope movement.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a "with" movement, which is typically seen in hyperopic (farsighted) eyes, not myopic eyes. The patient's spherical error is -3D, indicating myopia.
- **Option B:** This option might seem plausible due to the cylindrical error, but the dominant reflex movement in retinoscopy for a myopic eye (even with astigmatism) is against the retinoscope movement.
- **Option D:** This option does not accurately describe the typical reflex movement for a myopic eye with astigmatism during retinoscopy.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in retinoscopy, a "against" movement indicates myopia, and a "with" movement indicates hyperopia. The presence of astigmatism can cause variations in reflex movement depending on the meridian examined, but the spherical error typically dominates the overall reflex movement.
## **Correct Answer:** .