Refraction and Vision Assessment
Measuring acuity properly
Record unaided and aided acuity at the correct distance, with adequate illumination, one eye at a time and then binocularly. Use logMAR with letter-by-letter scoring where available and record the pinhole result separately. Improvement with a pinhole suggests uncorrected refractive error; failure to improve points to media, macular or neural causes and demands further assessment.
Retinoscopy
Set the working distance (commonly 50 cm equals 2.00 D; 67 cm equals 1.50 D) and neutralise both meridians, using spheres until the reflex is neutral in one meridian and then a cross-cylinder or sphere-cylinder combination for the other. Subtract the working distance at the end. Refine subjectively: sphere to the most plus that gives best acuity (or least minus), Jackson cross-cylinder for cylinder axis then power, duochrome to balance, and binocular balance before finalising.
Prescribing decisions
Convert between plus-cylinder and minus-cylinder notation where necessary, adjust for vertex distance above about plus or minus 4.00 D, and check that a reading addition matches the working distance the patient actually uses. Cycloplegic refraction is mandatory in young children, in accommodative esotropia, and whenever hyperopia is suspected but the patient accommodates well.
Traps
Over-minusing a young hyperope; accepting an axis without verifying it with the cross-cylinder; ignoring anisometropia; not recording which method produced the result; and forgetting that a pinhole will not help media opacity. Question writers like the scenario where acuity improves with a pinhole but still does not reach normal - the answer is not simply stronger spectacles.
Rule of thumb
With the retinoscope, "with" motion means add plus until neutral, "against" motion means add minus; then always subtract your working distance.