Question:hard
A female patient complains of blurring of vision and was prescribed \(-0.5D\) spherical lenses. Retinoscopy done at \(1\ m\) with a plane mirror will cause the image to move in which manner?
A female patient complains of blurring of vision and was prescribed \(-0.5D\) spherical lenses. Retinoscopy done at \(1\ m\) with a plane mirror will cause the image to move in which manner?
Show Hint
Compare the patient's far point distance to the examiner's 1 m working distance to find the movement direction.
Updated On: Jul 8, 2026
- Image moves in the direction of the mirror
- Image moves in the opposite direction
- No movement of the image
- Scissors reflex is seen
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Set the target neutrality point.
Retinoscopy at a $1\ m$ working distance is neutral for an eye with exactly $-1.00D$ of myopia, since $1/1 = 1.00D$. Anything less myopic than this shows movement in the same direction as the mirror (a "with" reflex); anything more myopic shows movement in the opposite direction (an "against" reflex).
Step 2: Place this patient on that scale.
Her correction is $-0.5D$, so she is less myopic than the $-1.00D$ neutral point for this test distance.
Step 3: Think in terms of the far point instead.
Her far point sits at $1/0.5 = 2\ m$ away, well beyond the examiner sitting at $1\ m$. The examiner is therefore looking from inside her far point, which by definition always produces a "with" movement.
Step 4: Match "with" movement to an answer choice.
A "with" movement means the red reflex in the pupil travels in the same direction the examiner sweeps the mirror, that is, in the direction of the mirror.
Step 5: Discard the wrong choices.
No movement only happens exactly at $-1.00D$. Opposite (against) movement only happens beyond $-1.00D$ of myopia. A scissors pattern needs an irregular cornea, which is not mentioned here.
Step 6: Conclude.
\[ \boxed{\text{Image moves in the direction of the mirror}} \]
Retinoscopy at a $1\ m$ working distance is neutral for an eye with exactly $-1.00D$ of myopia, since $1/1 = 1.00D$. Anything less myopic than this shows movement in the same direction as the mirror (a "with" reflex); anything more myopic shows movement in the opposite direction (an "against" reflex).
Step 2: Place this patient on that scale.
Her correction is $-0.5D$, so she is less myopic than the $-1.00D$ neutral point for this test distance.
Step 3: Think in terms of the far point instead.
Her far point sits at $1/0.5 = 2\ m$ away, well beyond the examiner sitting at $1\ m$. The examiner is therefore looking from inside her far point, which by definition always produces a "with" movement.
Step 4: Match "with" movement to an answer choice.
A "with" movement means the red reflex in the pupil travels in the same direction the examiner sweeps the mirror, that is, in the direction of the mirror.
Step 5: Discard the wrong choices.
No movement only happens exactly at $-1.00D$. Opposite (against) movement only happens beyond $-1.00D$ of myopia. A scissors pattern needs an irregular cornea, which is not mentioned here.
Step 6: Conclude.
\[ \boxed{\text{Image moves in the direction of the mirror}} \]
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