Impact of Different Visual Field Instruction Strategies on Reliability Indices

Purpose: To investigate and compare the visual field performance following three different types of visual field instruction strategies. Method: Ninety consecutive visual field-naive glaucoma patients who can perform the test and understand instructions were imparted three forms of instructions prior to the visual field test. Patients with visual acuity <20/200, central corneal opacities, or anterior segment pathology and patients unable to understand general instructions/uncooperative were excluded. All forms of instructions were given by a trained optometrist in the patients' own language as an instruction leaflet read out in 5 min for a verbal group (groupl) and by a 5 min video created in house (group 2). Group 3 patients were shown the video first, followed by verbal instructions. We evaluated the reliability parameters in each group after visual field testing by an independent optometrist blinded to the form of instruction given. Results: Among the three groups, group 3 patients had the least number of repeat tests. Eyes with MD<-12Db had better reliability than that of the other groups. Mixed-model linear regression analysis shows that the duration of the test was significantly influenced by the severity of glaucoma in group 1, which is further predisposed by false negatives (FN; beta = 0.06, p < 0.0001, R-2 61.7%). Conclusion: The video with verbal instruction can minimize the number of repeated tests compared with only verbal or only video instruction medium. The video as well as the combined video/verbal instructions have a practical influence of obtaining more reliable fields compared with only verbal instruction.