Many patients with heterophoria, who appear to have fair to good amplitude of fusion with prisms when fixating on a 3 mm. white-headed pin or light at 25 cm., are unable to maintain fusion when accommodating on small print (300 mm. type for example). These patients, usually young children, are frequently found to be slow readers and manifest an overconvergence on ophthalmographic studies, particularly when shifting their fixation to the next line of print. Patients with this difficulty often improve their ability to sustain fusion for near work with a simple home exercise.
The patient is given a horizontal prism rack1 and an accommodation card2 (Fig. 1) with letters, numbers, and single E's graduated in size. Holding the accommodation card in one hand and the prism rack in the other (Fig. 2), the patient is instructed to fixate the smallest word, number, or E which he can fuse while
BERENS C, BRACKETT V, TAYLOR BE. Diverging Exercises While AccommodatingA Simple Technique Using an Accommodation Card, a Prism Rack, and Plus and Minus Spheres. AMA Arch Ophthalmol. 1958;59(1):24-28. doi:10.1001/archopht.1958.00940020048004