By Edwin Howell, Bsc. Optom., Ph.D.
These cards are a direct reading phoria measurement technique utilizing vertical prism dissociation. Two cards are available; the small card is calibrated for measurements at 33 cm and the large card is calibrated for measurements at 3m. The concept is simple and can be used for children as young as 4. Moment-by-moment changes in the phoria can be monitored and the cards can be used with a trial frame or phoropter. The cards are specially designed for accurate accommodation stimulation and monitoring. There is also an X-Cyl target and a variety of letter and word targets useful for near acuity, accommodation amplitude and facility, near retinoscopy and vergence challenge testing. Set of two cards includes 1 distance and 1 nearpoint card.