Retinoscopy

Key Points at a Glance

Key points of this test

• Retinoscopy is a test that objectively measures refractive error by observing the movement of the reflected light within the pupil using a retinoscope.
• Since it does not require subjective responses from the patient, it is essential for refractive evaluation in infants, individuals with developmental delays, and patients with communication difficulties.
• Compared to autorefractors, it is less affected by instrument myopia and is highly useful in difficult-to-measure cases.
• The refractive state is determined from the movement of the reflected light (with-motion, against-motion, neutralization), and the neutral point is found by adding lenses.
• In children, due to strong accommodation, retinoscopy using cycloplegic agents (cyclopentolate, atropine) is the standard.
• Static retinoscopy measures refractive error, while dynamic retinoscopy can evaluate accommodative function.

1. What is Retinoscopy?

Retinoscopy (skiascopy) is an objective refraction test that measures the eye’s refractive error by observing the movement of reflected light in the patient’s pupil through a retinoscope.

History

In 1859, Sir William Bowman first reported irregular fundus reflexes in astigmatic eyes. In 1873, French ophthalmologist Cuignet performed the first objective diagnosis of refractive error using a plane ophthalmoscope, naming it “keratoscopie.” In 1880, Parent published a quantification technique using lenses, establishing the foundation of objective refraction.

The modern streak retinoscope is based on the rotating slit technology developed by Jack Copeland in the 1920s. The Copeland streak retinoscope, patented in 1927, forms the basis of today’s retinoscopy.

Features and Utility

The greatest advantage of retinoscopy is that it does not require subjective responses from the patient. It is particularly useful for the following populations:

• Infants and young children: Children too young to cooperate with subjective refraction
• Adults with developmental delays: When communication is difficult
• Psychogenic visual disturbance (somatic symptom disorder): Cases where subjective refraction is unreliable
• Autism spectrum disorder: Cases where cooperation with examination is difficult
• Bedridden patients: When use of an autorefractor is difficult

Compared to autorefractors, it is less affected by instrument myopia and the device is simple. It is considered an essential examination for the diagnosis and treatment of refractive errors in children.

Q What is the difference between retinoscopy and autorefractors?

A

Autorefractors automatically measure refraction using a computer, but are susceptible to instrument myopia (accommodation caused by looking into the device). Retinoscopy is less affected by instrument myopia and is useful in difficult cases such as children, poor fixation, and media opacities. However, retinoscopy requires several years of training to master.

2. Findings and Indications of Retinoscopy

Movement of the Reflex and Refractive State

When the light of the retinoscope is projected onto the pupil and scanned, the reflex from the fundus moves. The refractive state is determined by the direction of this reflex.

With Motion

Definition: The reflex moves in the same direction as the retinoscope streak.

Refractive state: Hyperopia, emmetropia, or myopia less than -2D (for a working distance of 50 cm).

Action: Add plus lenses to find the neutral point.

Against Motion

Definition: The reflex moves in the opposite direction to the retinoscope streak.

Refractive state: Myopia exceeding −2D (for a working distance of 50 cm).

Action: Add minus lenses to find the neutralization point.

Neutralization

Definition: No movement of the reflex is observed; the entire pupil is uniformly illuminated.

Refractive state: The far point coincides with the retinoscope position. At a working distance of 50 cm, this corresponds to a refractive error of −2D.

Action: No lens addition is required.

In addition to direction, the following characteristics of the reflex are also helpful for assessment:

• Width of the reflex: As neutralization approaches, the reflex becomes wider.
• Speed of the reflex: As neutralization approaches, the reflex moves faster and becomes brighter.
• Brightness of the reflex: Larger refractive errors produce a darker and duller reflex.

Main Indications

• Refraction testing in children and infants (for children under 3 years, handheld devices or retinoscopy are the primary methods).
• Cases where autorefractometer measurements are difficult.
• Verification of the appropriateness of spectacle or contact lens prescriptions (over-retinoscopy).
• Evaluation of accommodative function (dynamic retinoscopy).
• Evaluation of media opacities

4. Examination Procedure and Technique

Static Retinoscopy

Static retinoscopy is a method to measure refractive error at distance while accommodation is relaxed.

Setup

• Environment: A dimly lit room is preferable. The pupil dilates, improving the contrast of the reflex.
• Working distance: 50 cm is standard. Maintain a constant distance (a string can be helpful).
• Fixation target: Placed at distance. For infants, use a toy or voice to attract attention.
• Position: Patient sits upright. Perform with both eyes open.
• Retinoscope setting: Set to plane mirror mode (divergent light beam).

Procedure

1. Hold the streak vertically and shine light into the patient’s right eye; observe the red reflex.
2. Scan the streak horizontally to determine the direction of reflex motion (with or against).
3. Rotate the streak 90 degrees and scan vertically.
4. If the reflex is the same in all meridians, it is spherical; if different, it is astigmatic.
5. If with motion, add plus lenses; if against motion, add minus lenses in front of the eye to find the neutralizing lens power.
6. If astigmatism is present, determine the neutralizing lens for each principal meridian.

A mnemonic is “SPAM”: Same (with motion) is Plus, Against (motion) is Minus.

Recording Results

Subtract the working distance correction from the lens power required for neutralization.

The formula for refractive power and an example are shown below.

Working Distance	Correction Value	Formula
50 cm	−2.00 D	Neutralizing lens − 2 D
67 cm	−1.50 D	Neutralizing lens − 1.5 D
100 cm	−1.00 D	Neutralizing lens − 1 D

For example, if neutralization is achieved with a −1.00 D lens at a working distance of 50 cm, the ocular refraction is −1.00 D − 2.00 D = −3.00 D.

Q Why is it necessary to subtract the working distance?

A

In retinoscopy, the examiner observes from a finite distance, so the refractive power corresponding to that distance is included in the measurement. A working distance of 50 cm corresponds to 2.00 D, and subtracting this yields the true refractive error. The longer the distance, the smaller the correction value.

Dynamic Retinoscopy

Dynamic retinoscopy is a test that evaluates accommodative function by having the patient actively accommodate. Unlike static retinoscopy, accommodation is not suspended and no lenses are used.

Procedure

1. Have the patient wear appropriate distance correction glasses and hold a near target at reading distance.
2. Confirm a with-motion reflex in both eyes during distance fixation.
3. Have the patient fixate on the near target and confirm that the reflex changes to a slight against-motion.
4. Repeat the steps to confirm maintenance of accommodation.

Interpretation of Results

• Normal response: A slight with-motion at distance changes to a slight against-motion at near. Record as “rapid, complete, and stable.”
• Abnormal reactions: large against motion, dull reflex, persistence of with motion even at near, asymmetry of reflex between axes, etc. Suggestive of accommodative dysfunction.

Precautions for Retinoscopy

Under mydriasis, aberrations of the cornea and lens may affect the reflex, and the reflected light may differ between the central and peripheral parts of the pupil. Caution is needed when assessment is difficult. Also, in high myopia, the reflex light is attenuated and becomes dark, so it is advisable to increase the illumination of the retinoscope.

5. Practical Retinoscopy in Children

Children have much stronger accommodative power than adults, making it difficult to achieve a non-accommodative state. Therefore, for refractive examination in children, retinoscopy using cycloplegic agents is the standard ¹⁾.

Types and Selection of Cycloplegic Agents

The characteristics of the main cycloplegic agents are shown below.

Agent	Indication/Usage	Duration of Effect
Cyclopentolate 1%	Age 1 year and older, 2 instillations 5 minutes apart	24–48 hours
Atropine 1%	Esotropia/amblyopia, twice daily for 7 days	Approximately 3 weeks
Tropicamide	Short examination in adults	Several hours

• Cyclopentolate hydrochloride 1%: The most commonly used drug for cycloplegic retinoscopy in children, providing cycloplegic effect close to atropine with shorter duration of action ¹⁾. Instill twice at 5-minute intervals, then examine after 60 minutes.
• Infants under 6 months: A combination of cyclopentolate 0.2% and phenylephrine 1% is used ¹⁾.
• Atropine sulfate 1%: Has the strongest cycloplegic effect. For esotropia or amblyopia, examination under atropine should be performed at least once. Instill twice daily for 5–7 days at home before examination. Only 1% is commercially available; some facilities dilute to 0.25–0.5% for young children.
• In dark irides, additional cycloplegic drops or combination with phenylephrine 2.5% and tropicamide 1% may be effective ¹⁾.

Side effects and management

The main side effects of cycloplegic agents are as follows ¹⁾.

• Atropine: Facial flushing, fever, increased blood pressure, palpitations, dry mouth, hallucinations, agitation, seizures.
• Cyclopentolate: Transient hallucinations, ataxia, emotional confusion, drowsiness (caution required even after examination).
• Common: Hypersensitivity reactions, nausea, vomiting, flushing (rare but possible).

To reduce side effects, compress the lacrimal sac for several minutes after instillation to suppress systemic absorption via the nasal mucosa ¹⁾. If severe reactions occur, provide emergency care and consider physostigmine administration ¹⁾. Since instillation is performed at home, written explanation and warnings are recommended.

Precautions when using cycloplegic agents

Atropine-induced mydriasis begins within minutes of instillation and persists for 7–10 days, during which patients complain of photophobia. Cycloplegia lasts 3–5 days, reducing near visual acuity. Cyclopentolate also has effects lasting until the next day, so choose a day that does not interfere with schoolwork. Instruct parents to administer only one drop of any agent and not to add extra drops.

Role of Retinoscopy in Amblyopia and Strabismus

Accurate assessment of refractive error is essential in diagnosing amblyopia and strabismus, and retinoscopy under cycloplegia is recommended as the standard examination¹⁾. Retinoscopy before cycloplegia is useful for rapid evaluation of accommodation and is also used to assess asthenopia and accommodative insufficiency in children with high hyperopia¹⁾.

For spectacle prescription, full correction is the basic principle in children with amblyopia or accommodative esotropia. Even if corrected visual acuity and ocular alignment are normal, spectacle correction should be considered if hyperopia exceeds +2 D or astigmatism exceeds 1.5 D.

Q Why are cycloplegic agents necessary for retinoscopy in children?

A

Children have much stronger accommodative ability than adults and unconsciously accommodate during retinoscopy. This shifts the refractive value toward myopia, preventing accurate measurement. Blocking accommodation with cycloplegic agents allows evaluation of the true refractive state.

Q How are atropine and cyclopentolate used differently?

A

Generally, cyclopentolate is used for children aged 4 years and older, while atropine is used for those aged 3 years and younger in many facilities. For esotropia or amblyopia, it is desirable to perform examination with atropine at the first spectacle prescription. Atropine has a strong effect but long duration (3 weeks), while cyclopentolate recovers relatively quickly (24–48 hours).

6. Optical Principles and Detailed Mechanisms

Far Point and Refractive State

Retinoscopy determines refractive error by identifying which corrective lens places the eye’s far point at infinity. The far point is the point in space conjugate to the retina of the unaccommodated eye.

• Emmetropia: The far point is at infinity, and parallel rays focus on the retina. Neutrality is observed in retinoscopy.
• Myopia: Rays focus in front of the retina and emerge as convergent rays. The far point lies between the eye and infinity, and against motion is observed.
• Hyperopia: Rays focus virtually behind the retina and emerge as divergent rays. The far point is a virtual point behind the eye, and with motion is observed.
• Astigmatism: Refractive power differs by meridian, producing two focal lines. With or against motion may differ by meridian.

Structure of the streak retinoscope

Modern streak retinoscopes are based on Copeland’s rotating slit technique and consist of three main parts.

• Optical head: Projects a slit-shaped beam of light from one side and has an observation window on the other. A condenser lens focuses the light onto a mirror for proper projection.
• Sleeve: Sliding it up and down changes the vergence (convergence/divergence) of the light beam, and rotating it changes the meridian of the streak. It can switch between plane mirror effect (parallel rays) and concave mirror effect (converging rays).
• Handle: Contains the battery.

Phenomena in astigmatism determination

The following phenomena are used when determining the axis and power of astigmatism.

• Width phenomenon: The reflex appears thinnest when sweeping along the correct axis meridian. It becomes thicker as you move away from the axis.
• Brightness phenomenon: The reflex is brightest along the correct axis meridian and becomes duller as you move away.
• Break and skew phenomenon: In high astigmatism, even when the streak is off the axis, the reflex tends to align with the cylinder axis.
• Axis crossing method: When the correct axis is neutralized, the most distinct with-motion reflex is seen at a meridian 90 degrees away.

The interval between the anterior and posterior focal lines caused by astigmatism is called the Sturm interval. Stronger astigmatism results in a longer Sturm interval and a larger circle of least confusion.

8. References

1. American Academy of Ophthalmology Pediatric Ophthalmology/Strabismus Preferred Practice Pattern Panel. Amblyopia Preferred Practice Pattern. San Francisco, CA: American Academy of Ophthalmology; 2024.
2. Prowse AB. Retinoscopy. Bristol Med Chir J (1883). 1883 Dec;1(2):200-211. PMID: 28896028.
3. Mackool RJ. Intraoperative retinoscopy. J Cataract Refract Surg. 2006;32(4):548-9. PMID: 16698458.