Dynamic Retinoscopy

In Static Retinoscopy we have the patient fixate on a target at optical infinity to relax accommodation. In Dynamic Retinoscopy the patient fixates on a target at near, instead of at distance. The term dynamic is used because the patient's accommodation is active. In contrast to static retinoscopy, no woking distance power is added or subtracted from the finding.

If the patient's accommodation is equal to that required for the fixation distance, the dynamic and static retinoscopy results will be equal. An average patient will fail to accommodate fully for the testing distance, exhibiting a lag of accommodation of 0.50 to 1.00 diopters.

Book Retinoscopy

The patient, typically a child, views pictures in a book. Retinoscopy is performed while the child's attention is drawn to the pictures. The examiner watches the retinoscopy reflex and notes:
The brightness of the reflex should increase as the patient identifies the object, at the same time against motion is noted, indicating an increase in accommodation.

A study of book retinoscopy using optometry students as subjects had the following conclusions:

  1. When reading material is interesting or there is a search for meaning, the reader accommodates for a distance closer than the plane of regard. Accommodation increases when material becomes difficult, and decreases when material is easily comprehended.
  2. When the material is so difficult that it can not be comprehended, or when it is readily comprehended but not interesting to the reader, accommodation is maintained at or beyond the plane of regard.
  3. When reading material is at 16 inches, the reader cannot accommodate for a distance closer than 10 inches (4D) without blur.
  4. When reading material is at 16 inches, the reader can not accommodate for a distance farther than 20 inches (2D). This represents a maximum lag of 0.50D, yet clinically we measure lags of 0.50 to 1.00 D. The discrepancy is probably due to the difference between active reading (trying to secure meaning) and simply looking at letters.

Bell Retinoscopy

This technique was originally performed using a small bell suspended in front of the examiner's forehead. A one half inch steel ball attached to a thin metal rod has replaced the bell as a fixation target. The examiner performs retinoscopy at 50cm (20 inches). The patient is instructed to fixated on the target. The examiner slowly moves the ball toward the patient until neutral motion is observed. Typically neutrality will be observed when the ball is 15 to 16 inches from the patient. This yields a lag of 0.50 to 0.75D.

MEM Retinoscopy

A fixation target (letters on the retinoscope or card attached to the retinoscope) is placed at the patient's customary reading distance. The patient should be focused at the plane of the retinoscope. The examiner introduces lenses in front of the patient until neutrality is observed. The lenses are inserted and removed quickly, to avoid changing the patient's accommodative status.

Nott Retinoscopy

The patient fixates on the target at 40 cm. The examiner performs retinoscopy at a distance greater than the fixation distance and moves toward the patient until neutrality is observed. The dioptric equivalent of the linear distance between the target and neutrality is recorded and represents the lag of accommodation.

Interpreting Results

Normal Lag: +0.50 to +0.75D
High Lag: +1.00D or higher
Decreased Lag (Lead): +0.25D or less

High Lag

Lead or Low Lag