Static Retinoscopy

Clinical Use

Retinoscopy is used to obtain an objective measure of the patient's refractive state. In static retinoscopy the refractive state is determined while the patient fixates a distance object (to relax accommodation). In dynamic retinoscopy the patient fixates on an object in the plane of the retinoscope.

Working Distance

Choose a working distance of either 67cm (+1.50D) or 50cm (+2.00D). The retinoscopy lens in the AO style phoropter is +1.50D. Using a "working lens" in place during retinoscopy will save the trouble of subtracting the dioptric value of the working distance, but may result in increased reflections, absorption, and aberrations.

Fixation Target

The target chosen for the patient to observe must be large (20/400). Remember, at neutrality the patient will be 1.50 to 2.00 diopters out of focus. The bichrome (red/green) filter in the projector will help to reduce the brightness of the chart's reflection in the phoropter lenses.

Patient Instructions

The patient is intructed to fixate the distance target. It may be helpful to tell the patient to relax their eyes. The patient's right eye is scoped with the examiner's right eye and the patient's left eye is scoped with the examiner's left eye. This allows the examiner to stay as close to the patient's visual axis as possible, however, the examiner should not obstruct the patient's view of the target. The patient should be instructed to tell the examiner if the view of the target is blocked.

Procedure

With no lenses in the phoropter there are three possible initial reflexes that may be observed:

-With Motion, the patient is hyperopic, emmetropic or less myopic than the dioptric value of the

distance.

-Neutrality, the patient's myopia is equivalent to the dioptric value of the working distance.

-Against Motion, the patient's myopia is greater than the dioptric value of the working distance.

1. Identify the meridian with the most with motion (thinner reflex). This is the most plus meridian. Neutralize this meridian first. Add plus lenses to neutralize with motion and minus lenses to neutralize against motion.

2. Rotate the streak 90 degrees and neutralize the other meridian. The axis of the cylinder lens should now be aligned with the streak of the retinoscope. Neutralize this meridian by adding minus cylinder power.

3. Remove the working lens by removing 1.50 or 2.00D of plus power from the phoropter or remove the built in retinoscopy lens.

4. Record your findings in minus sphero-cylinder form.

Astigmatism

Most people have some degree of astigmatism. This results in a difference in the appearances of the reflexes observed in the two principal meridians. As the reflexes are neutralized the streak may need to be rotated to keep it aligned with the reflex.

Brightness of the Reflex

As the reflex approaches neutrality, the illuminated area of the retina becomes increasingly smaller. This increases the amount of light reflected per unit area of the retina and, therefore, causes the reflex to appear increasingly brighter to the examiner.

Neutrality

When the patient's far point is at the plane of the retinoscope, no motion is seen. The retinoscope is conjugate to the patient's retina. Neutrality characterizes not emmetropia, but rather an eye made myopic by the dioptric equivalent of the working distance. Only if one holds the retinoscope at 6m or places a working lens in front of the patient's eye does neutrality indicate an emmetropic eye.

Sources of Error in Retinoscopy

1. Incorrect working distance

2. Scoping off the patient's visual axis

3. Failure of the patient to fixate the distance target

4. Failure to obtain reversal

5. Failure to locate the principal meridians

6. Failure to recognize scissors motion