Table 1.
Detailed Characteristics of the Four Refractive Error Measurement Techniques Evaluated in this Study
| Characteristics | Retinoscope | Tabletop Autorefractor | Photoscreener | E-see |
|---|---|---|---|---|
| Working principle | Foucault knife-edge | Image size assessment using rotary prisms | Eccentric IR photorefraction | Wavefront aberrometry |
| Operating range | No specific operating range | +22 D to -25 D for sphere and ±10.00 D for cylinder | ±7.50 D for sphere and ±3.50 D for cylinder | ±10.00 D for sphere and ±6.00 D for cylinder |
| Invasiveness of measurement | Noninvasive. Measurements performed from a distance. | Noninvasive. Participant stabilized on forehead rest. | Noninvasive. Measurements are performed from a distance. | Device touches the face for measurement |
| Portability | Portable | Non-portable | Portable | Portable |
| Measurement time | Consumes time for measurement | ∼5 measurements per second | <1 s per measurement | ∼10 measurements per second |
| Fixation distance | Distant target | Near target with simulated distance viewing | Distant target | Distant target |
| Pupil size dependence | Measurements become challenging with pupil miosis | Stable measurements for pupil diameter up to 2 mm | Measurement accuracy decreases with pupil miosis | Measurement accuracy may vary with pupil diameter |
| Binocular viewing / measurements | Viewing can be binocular, but the measurement is monocular | Only monocular viewing and measurements | Viewing and measurement can be binocular | Only monocular viewing and measurements |
| Participant cooperation | Needs limited cooperation. Useful in challenging cases. | Participant cooperation is essential for reliable measurements | Needs limited cooperation. Useful in challenging cases. | Participant cooperation is critical for reliable measurements |
| Examiner training | Examiner training is time-consuming | Examiner can be trained within a short time | Examiner can be trained within a short period of time | Examiner can be trained within a short period of time |
| Near-triad measurements | Only measurement of accommodation is possible | Only measurement of accommodation is possible | Near-triad can be measured in sync with each other | Only measurement of accommodation is possible |
Data on operating ranges and measurement time are obtained from the manufacturer prescribed user manual of each instrument.