Optometry & Visual Performance 255 Volume 13 | Issue 4 | December 2025 with the Brock string and eccentric card for three days per week (15-20 minutes each session) and advised a six-month follow-up. Case 2 A 35-year-old male driver presented with complaints of eyestrain and intermittent double vision at both distance and near, which usually occurred at the end of the day. He was forced to leave his job two years prior due to persistent double vision. He had been using prism glasses since the age of 25. Initially, the prism glasses resolved the double vision, but over time, the symptoms gradually reoccurred. He had no documentation of prior consultations and denied any history of trauma or psychological illness. His medical history was negative, and he was not taking any medication. Visual acuity was 6/6 (N6 at 40 cm) in each eye through his presenting glasses (Plano with 3∆ BO OD, OS). The dry refraction revealed no changes. Cycloplegic refraction was +0.25 OD, OS. The final subjective acceptance was plano in each eye. After one week, a binocular vision evaluation was conducted (Table 3). Without his prism glasses, the cover test revealed a comitant, high-frequency left intermittent esotropia of 10∆ at near and a constant left esotropia of 20∆ at distance. With the prism glasses on, he showed intermittent left esotropia with moderate control of 4∆ at near and intermittent left esotropia with poor control of 15∆ at distance. He was diagnosed with DI with normal correspondence. Since the patient did not want strabismus surgery and was already using glasses with prism that did not eliminate diplopia, vison therapy to enhance negative fusional vergence was the selected treatment option. With prism glasses (Plano with 3∆ BO OD, OS), office-based therapy was conducted six sessions per week (45 minutes per session), and home-based therapy for 15 minutes daily was prescribed (Table 4). The initial sessions of vision therapy were aimed at increasing the amplitude of negative fusional vergence at near. Once he was comfortable at near, the distance was gradually increased. We started with peripheral fusional targets, and as the amplitude increased, we progressed to macular and foveal fusional targets in the synoptophore to increase the difficulty of the task. After one month of vision therapy, he had no visual complaints. The cover test revealed orthophoria at near and intermittent left esotropia with good control at a distance while wearing prism glasses. Without the glasses, the frequency of intermittent esodeviation increased. He had to discontinue officebased vision therapy because he needed to return to his hometown, so we advised him to continue homebased therapy with his prism glasses using the Brock string, prism bar, and eccentric card, and to follow up after three months. Test Before Therapy After Therapy Without prism glasses With prism glasses Without prism glasses With prism glasses BCVA RE: 6/6 (N6 @ 40cm) LE: 6/6 (N6 @ 40cm) RE: 6/6 (N6 @ 40cm) LE: 6/6 (N6 @ 40cm) RE: 6/6 (N6 @ 40cm) LE: 6/6 (N6 @ 40cm) RE: 6/6 (N6 @ 40cm) LE: 6/6 (N6 @ 40cm) Cover test (with correction) Near: 10∆ left intermittent esotropia with poor control Distance: 20∆ constant left esotropia Near: 4∆ left intermittent esotropia with moderate control Distance: 15∆ left intermittent esotropia with poor control Near: 6∆ esophoria Distance: 16∆ left intermittent esotropia with moderate control Near: orthophoria Distance: 10∆ left intermittent esotropia with good control Gradient AC/A 2.5:1 3:1 NFV (break/recovery) Near: 2/x Distance: x/x Near: 4/2 Distance: 2/x Near: 10/6 Distance: 6/4 Near: 20/16 Distance: 16/10 Worth four-dot test Near: uncrossed diplopia Distance: uncrossed diplopia Near: uncrossed diplopia Distance: uncrossed diplopia Near: binocular single vision Distance: uncrossed diplopia Near: binocular single vision Distance: binocular single vision Stereopsis (Titmus fly) 400 sec of arc 200 sec of arc 80 sec of arc 60 sec of arc Correspondence (with synoptophore) Normal Normal Table 1. Orthoptic Findings Before and After VT: Case 2
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