Does an iPad fixation disparity test give equivalent results to the Mallett near fixation disparity test?

Associations between Binocular Vision Disorders and Contact Lens Dissatisfaction

“…259,261 These reported correlation between symptoms and associated phoria suggest that it may be unnecessary to plot fixation disparity curves to identify symptomatic individuals. 260 The results obtained with a Mallett Unit are influenced by changes to the test design 265 and practitioner instructions. 266 Both the standard versions of the Wesson and Saladin Cards can measure fixation disparity curves.…”

Reply to: Mallett unit or fully fusionable images for prisms against asthenopia?

“…For measuring fixation disparity or the aligning prism, clinicians may use the Mallett Unit with stationary presented dichoptic nonius lines. 1 Two recent Letters to the Editor 2 , 3 referred to the practical question whether dichoptic targets may perhaps distort the measurement. 4 In this debate, earlier research on sensory and motor aspects of fixation disparity may be helpful.…”

Reply to: Mallett unit or fully fusionable images for prisms against asthenopia?

“…We thank Professors Kommerell and Bach for their interest in our article. 1 Mallett advocated the use of a trial frame with his test as it allows a normal head posture and visual field. 2 Mallett advocated using small step sizes (1D horizontally); 2 “gradually increasing the strength until the slip disappears – never the reverse procedure”; 3 and “between changes of prisms or spheres the patient should read two or three lines of print surrounding the target”.…”

“… 11 12 As Kommerell and Bach note, there is a fairly large body of research that has used the Mallett unit following the designer's instructions. 6 Our concern is that, since the test results are sensitive to differences in instructions 13 and test design, 1 if clinicians use the test in an unintended way this could lead to unintended consequences, including the over-prescribing of prisms.…”