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Frequency of seeing characteristics of the short wavelength sensitive visual pathway in clinically normal subjects and diabetic patients with focal sensitivity loss

¹ School of Optometry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
² Department of Ophthalmology and Vision Science, Toronto Western Hospital, University of Toronto, M5T 2S8, Canada
³ University of Ulster, Coleraine, Co Londonderry, Northern Ireland, UK

Correspondence to:
Correspondence to:
Chris Hudson
PhD, School of Optometry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada; chudson{at}scimail.uwaterloo.ca

Aims: To define the frequency of seeing (FOS) characteristics of the short wavelength (SW) sensitive visual pathway in clinically normal subjects and in diabetic patients with focal SW sensitivity loss.

Methods: For clinically normal subjects, FOS was assessed at two retinal locations (4.24° and 9.90° eccentricity) for both white on white (WW) and SW stimulus parameters. Interexamination variability was quantified for the clinically normal subjects only. For patients with diabetes, FOS was assessed inside an area of focal SW sensitivity loss, and at the same eccentricity in the quadrant diametrically opposite, using SW stimulus parameters only.

Results: For clinically normal subjects, the group mean SW FOS slope was significantly flatter (p<0.0001) than that of WW at both locations. The coefficient of repeatability for SW FOS slope was ±41.55 dB^–1 (relative to a group mean sensitivity of 23.98 dB^–1) and ±19.98 dB^–1 (group mean sensitivity 16.15 dB^–1) for 4.24° and 9.90°, respectively. For the patients with diabetes, the group mean SW FOS slope was significantly flatter (p = 0.020), and group mean SW threshold significantly higher (p = 0.007) in the area of focal SW sensitivity loss than in that of the non-focal sensitivity loss.

Conclusions: The results of this study suggest that the clinical utility of SW automated perimetry will be limited by a greater magnitude of measurement variability, as indicated by a flatter FOS slope, compared to conventional automated perimetry.

Abbreviations: COR, coefficient of repeatability; FOS, frequency of seeing; SF, short term fluctuation; SW, short wavelength; SWAP, short wavelength automated perimetry; VA, visual acuity; WW, white on white

Keywords: short wavelength perimetry; frequency of seeing; short term fluctuation; psychometric function; diabetes; children

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