Abstract
Purpose: To compare patient preference for Swedish Interactive Threshold Algorithm (SITA) standard 24-2 protocol in Humphrey visual field analyzer (HVF) and full threshold N-30 protocol in frequency doubling perimetry (FDP) by primarily evaluating their perception about the test procedure and test targets along with surveying the factors that influence the patient concentration during perimetry and elements that determine the level of perimetry task difficulty.
 Methods: This study enrolled a subset of subjects from the Chennai Glaucoma Study. Each subject underwent a comprehensive ophthalmic examination after which they were randomly allocated to perform HVF and FDP with a 30-minute interval between the two procedures. SITA standard 24-2 protocol in HVF and full threshold N-30 protocol in FDP were used. This was followed by the administration of a questionnaire that mainly assessed the components such as (a) the patient preference for test procedure and test targets, (b) the factors influencing the patient concentration during perimetry performance, and (c) the impression about the level of perimetry task difficulty. The patient responses from the survey for each of the subcategories were obtained and analyzed using Chi-square test.
 Results: A total of 42 subjects with a mean age of 59.7 (SD 9.7) years were included, among which 18 (42.86%) were male and 24 (57.14%) were female. Thirty-two (76.19%) subjects felt both FDP and HVF were easy to perform, eight subjects (19.05%) felt that both perimetry techniques were difficult to perform, and two subjects (4.76%) found FDP procedure was easier than HVF, whereas the distribution was not statistically significant (Chi-square, p = 0.7). Pressing the button as a response to peripheral stimulus perception and inability to maintain steady central fixation for prolonged duration were the most commonly reported factors that influenced the level of difficulty of the perimetry tasks. A dark room ambience set for performing HVF was preferred by 32 (76.20%) subjects.
 Conclusion: There was no significant difference in the patient preference for test procedure and peripheral test targets. A black central fixation as in FDP and dark room ambience set for HVF were preferred.
Highlights
Standard automated perimetry (SAP) and frequency doubling perimetry (FDP) are two alternate technologies available to quantify the extent and degree of visual field loss due to glaucoma.[1]
There was no significant difference in the patient preference for test procedure and peripheral test targets
A black central fixation as in FDP and dark room ambience set for Humphrey visual field analyzer (HVF) were preferred
Summary
Standard automated perimetry (SAP) and frequency doubling perimetry (FDP) are two alternate technologies available to quantify the extent and degree of visual field loss due to glaucoma.[1] The Humphrey visual field analyzer (HVF) with SAP (750 I series; Carl Zeiss Meditec, Dublin, CA, USA) estimates differential light sensitivity using white targets and is considered as the gold standard in evaluating the visual field.[1,2] The frequency doubling perimetry (FDP) (Welch Allyn, Skaneateles Falls, NY, USA, and Carl Zeiss Meditec, Dublin, CA, USA) utilizes low-spatial-frequency sinusoidal grating target. Assessment of patient preference with respect to testing method, target characteristics, physical and mental aspects affecting the test performance, the levels of difficulty of the perimetry tasks, and so on, can help investigators to develop future prototypes of perimeters
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