What is the difference between objective and subjective refraction?

Objective refraction (retinoscopy and autorefraction) determines refractive error without requiring patient responses. Subjective refraction relies on the patient's verbal feedback to fine-tune the prescription using a phoropter and lens choices. Objective refraction provides the starting point that subjective refraction then refines.

Why do you subtract the working distance in retinoscopy?

The retinoscope is held at a finite distance from the patient (typically 67 cm or 50 cm), not at optical infinity. This working distance introduces extra plus power into the measurement. To find the actual refractive error, you must subtract the working distance equivalent (1.50 D for 67 cm, 2.00 D for 50 cm) from the neutralizing lens power.

Can autorefraction replace retinoscopy?

Autorefraction is a valuable screening tool but does not fully replace retinoscopy. Retinoscopy provides qualitative information about media clarity and is more reliable in patients who accommodate unpredictably (especially children), have media opacities, or have irregular corneas. Many clinicians use autorefraction as a quick starting estimate and rely on retinoscopy when more precision is needed.

Retinoscopy and Autorefraction: Objective Refraction Methods

What Is Objective Refraction?

Objective refraction determines a patient's refractive error without requiring verbal responses. This is particularly valuable for patients who cannot communicate reliably, such as infants, young children, non-verbal individuals, or patients who give inconsistent subjective answers. The two primary methods are retinoscopy and autorefraction, and both provide an essential starting point for the final subjective refraction.

Retinoscopy

Retinoscopy is a manual technique performed with a handheld retinoscope. The examiner projects a streak of light into the patient's eye and observes the behavior of the reflected light (the retinal reflex) as the streak is swept across the pupil.

The Retinal Reflex

The reflex moves in a specific pattern depending on the patient's refractive status:

"With" motion: The reflex moves in the same direction as the streak. This indicates the eye needs more plus power (or less minus).
"Against" motion: The reflex moves opposite to the streak direction. This means the eye needs more minus power (or less plus).
Neutralization: The reflex fills the entire pupil instantly with no discernible movement. This is the endpoint.

The examiner adds lenses from a phoropter or trial lens set until the reflex is neutralized. At neutralization, the lens power in place (minus the working distance compensation) equals the patient's refractive error.

Working Distance

Retinoscopy is performed at a specific working distance, typically 67 cm (which equals 1.50 D) or 50 cm (2.00 D). Because the examiner is working at a finite distance rather than optical infinity, the working distance must be subtracted from the neutralizing lens power. For example, if you neutralize at +4.00 D working at 67 cm, the actual refractive error is +4.00 - 1.50 = +2.50 D.

Always subtract your working distance from the neutralization finding. Forgetting this step is one of the most common retinoscopy errors and results in over-plusing the patient.

Autorefraction

An autorefractor is an automated instrument that measures refractive error quickly and objectively. The patient looks into the device at a target while the instrument projects infrared light into the eye, analyzes how it focuses on the retina, and calculates the sphere, cylinder, and axis.

Modern autorefractors produce results in seconds and are excellent screening tools. However, they have limitations:

Accommodation artifact: Particularly in young patients, looking into the device can trigger accommodation ("instrument myopia"), producing artificially myopic readings
Media opacities: Cataracts or corneal irregularities can produce unreliable measurements
Small pupils: Very miotic pupils may prevent accurate measurement
Fixation: Poor fixation or head movement degrades accuracy

Retinoscopy vs. Autorefraction

Feature	Retinoscopy	Autorefraction
Operator skill required	High (manual technique)	Low (automated)
Speed	Moderate	Fast
Works through media opacities	Better tolerance	May fail with dense cataracts
Accommodation control	Examiner can manage fogging	Fogging targets built in but less reliable
Use in children	Excellent (especially with cycloplegia)	Can be challenging in young children
Irregular corneas	Reflex quality gives qualitative info	May produce error messages

In pediatric patients, retinoscopy under cycloplegia remains the gold standard for objective refraction. Autorefractors tend to give less reliable results in young children who accommodate unpredictably.

When Are These Tests Performed?

Objective refraction typically happens after preliminary testing (acuity, pupils, motility) and before the doctor performs subjective refraction. In many practices, the ophthalmic assistant performs autorefraction as part of the pre-testing workup. Retinoscopy is usually performed by the doctor or a highly trained technician, though understanding its principles is important for every COA candidate.

Key Takeaways

Objective refraction measures refractive error without patient input, providing a starting point for subjective refraction
Retinoscopy uses a handheld retinoscope to observe and neutralize the retinal reflex with lenses
Always subtract the working distance from retinoscopy findings to get the actual refractive error
Autorefractors provide fast automated measurements but can be affected by accommodation, media opacities, and small pupils
Retinoscopy under cycloplegia is preferred for pediatric patients and cases where accommodation control is critical