Photoscreening is a vision screening method that uses a camera to capture ocular images of children without pupil dilation, estimating refractive errors from the crescent-shaped red reflex after the flash. It determines the presence of amblyopia risk factors, and if positive, referral to a pediatric ophthalmologist for cycloplegic examination is recommended.
The prevalence of amblyopia is reported as 0.14–4.8% overseas, and 0.58% in a meta-analysis of 3-year-old health checkups in Japan. In the United States, it is reported as 1.5% in African Americans and 2.6% in Hispanics. The most common cause of amblyopia is anisometropic amblyopia, followed by refractive amblyopia, strabismic amblyopia, and form deprivation amblyopia.
The main target is children aged 3–5 years, but it can also be used in infants under 3 years of age before language acquisition. Some infrared video refractometers can be used from 6 months of age.
Photoscreening targets children with risk factors for amblyopia. Amblyopia generally has few subjective symptoms, and young children rarely complain of decreased vision. Therefore, early detection through screening is important.
Normal Findings
Bilateral symmetric red reflex: A bright, uniform yellow-orange reflex is observed in both eyes8).
Individual variation in reflex color: The color tone differs among races due to choroidal pigment, but it is symmetric in the same individual.
Abnormal Findings
Opacity/diminished reflex: Opacities of the ocular media cause the reflex to appear darker 8).
White/yellow reflex: Suggests the presence of fundus pathology such as retinoblastoma 8).
Asymmetry: Suggests anisometropia. In high refractive error, the reflex is dim.
Total cataract: No reflex. In partial cataract, a dark reflex is seen against a yellow-orange background.
The Brückner test is used to evaluate the red reflex. In a dark room, set the retinoscope lens power to “0” and illuminate both eyes simultaneously from a distance of 45–75 cm 8). It should be performed before pupillary dilation 8).
The direction of the crescent reflex can help estimate the type of refractive error.
| Refractive error | Direction of crescent reflex |
|---|---|
| Hyperopia | Opposite side of flash (downward deviation) |
| Myopia | Same side as flash (upward deviation) |
The amblyogenic risk factors detected by photoscreening are as follows:
The following risk factors for amblyopia have been reported:
Visual sensitivity is highest from 1 to 18 months of age and persists until around 8 years of age. Normal visual development milestones are 0.1 at 1 year, 0.5 at 2 years, and 1.0 at 3 years. Removing amblyogenic risk factors during this sensitive period is crucial for visual development.
Photoscreening is not a definitive diagnosis but a screening for amblyopia risk factors. If the result is positive, it is recommended to promptly see a pediatric ophthalmologist and undergo a cycloplegic refraction examination.
iScreen
Year introduced: 2006. Improved to iScreen 3000 (handheld type) in 20116).
Method: High-speed continuous shooting on two axes at 90 degrees. Off-axis flash method.
Features: Images are electronically sent to the company and analyzed by experts. Consistent image interpretation is obtained.
plusoptiX
Year introduced: Commercially available in 19957).
Method: Infrared three-axis. Calculates autorefraction values.
Features: Referral criteria can be changed. Referral recommended for strabismus of 10 degrees or more.
Spot Vision Screener
Method: Handheld infrared. Miniaturized version of plusoptiX.
Features: Equipped with eye tracking function. Measurement possible in a few seconds with light and sound.
GoCheck KIDS
Method: iPhone app-based.
Features: Low cost to implement. Compatible with electronic health record (EHR) integration.
The features of the main devices are compared below.
| Device name | Method | Notes |
|---|---|---|
| iScreen | Off-axis flash | Remote expert analysis |
| MTI | Off-axis flash (Polaroid) | Discontinued |
| plusoptiX | Infrared video | Auto-refraction value calculation |
| Spot Vision Screener | Infrared video | Measurement completed in seconds |
In addition, the MTI Photoscreener is a Polaroid film-based device introduced in 1995 that takes two consecutive photographs using a 90-degree rotating flash 4). Although production has now ceased, it is still used in some places.
blinq. is a device that uses a birefringence scanner to directly detect amblyopia itself. It is expected to reduce unnecessary referrals.
Visual screening in Japan’s 3-year-old health checkup is conducted in three stages.
Photoscreening is only a screening test, not a definitive diagnosis. If positive, a detailed examination using cycloplegic refraction is necessary.
Photoscreening itself is a diagnostic tool and not a treatment, but the following describes the response when amblyopia risk factors are detected through screening.
If amblyopia risk factors are detected, referral for cycloplegic refraction is recommended. The following cycloplegic agents are used:
Standard treatment for diagnosed amblyopia is as follows:
The basic principle of photoscreening is the evaluation of the red reflex. When light is shone into the pupil with a retinoscope, the reflected light from the fundus is observed through the pupil. A normal eye shows a bright, symmetrical, yellow-orange reflex.
In the presence of refractive error, a crescent-shaped light-dark pattern appears in the reflected light at the pupil plane.
In eccentric photorefraction, a flash offset from the optical axis intentionally creates a crescent reflex1). Currently used methods are broadly classified into the following three types.
They are distinguished by the direction of the crescent reflex. In myopia, a bright crescent appears on the same side as the flash (upward); in hyperopia, it appears on the opposite side (downward). For details, see the section on “Optical Principles of Photorefraction”.
GoCheck KIDS is a photorefraction system based on an iPhone app. Compared to traditional dedicated devices, it has lower implementation costs and can integrate with electronic medical records, potentially contributing to the widespread adoption of large-scale screening.
blinq. is a new approach that directly detects amblyopia itself using a birefringence scanner. Traditional photoscreening is an indirect method that detects “amblyopia risk factors” such as refractive errors, but blinq. directly determines the presence or absence of amblyopia, which is expected to reduce unnecessary referrals.
