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Andrea Griffin, Han Cheng, John Robson; Measuring Contrast Sensitivity using CambBlobs2 Disposable Paper Charts in Normal Subjects. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4231.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the normative range and reproducibility of CamBlobs2, a newly designed inexpensive, near contrast sensitivity (CS) test, in normal subjects
Monocular and binocular CS were measured with CamBlobs2 chart at near and Pelli-Robson (PR) chart at 1 meter with the same luminance (85 cd/m2) in 30 habitually-corrected normal subjects (M:F = 8:22; mean age 37±14 years) two times (1-10 days apart). Mean high contrast logMAR acuity was 0.01±0.14 OD, 0.03±0.21 OS at distance, 0.06±0.12 OD, 0.07±0.14 OS at near. CamBlobs2 consists of 25 lines of 9 mm-diameter round blobs: 4 randomly located blobs (all with the same Weber contrast) per line, 0.05 increase in logCS from line-to-line (logCS range 0.80 to 2.05). Subjects were asked to mark the position of blobs on a CamBlobs2 chart held at their usual reading distance with guessing encouraged and maneuvering the angle of chart allowed. CamBlobs2 was scored based on the highest line on which the subject correctly marked two or fewer blobs. PR CS was scored with each correct letter counted as 0.05 logCS (range 0.00 to 2.40). At their first visit, the first 22 subjects also completed a test in which the contrast blobs were of various sizes (13, 9, 6 mm) to assess the effect of angular subtense of blobs on CS. Mean scores were compared with paired t test. Intervisit reproducibility was assessed with 95% limits of agreement (LoA) based on Bland-Altman plots.
Mean logCS (±SD) with CamBlobs2 at two visits were almost identical (1.87±0.11 OD, 1.84±0.09 OS, 2.00±0.08 OU at visit 1, 1.86±0.12, 1.84±0.10, 1.98±0.11 at visit 2; p>0.05 for all). Intervisit LoA for CamBlobs2 was -0.19 to 0.20 OD, -0.15 to 0.16 OS, -0.13 to 0.18 OU. Mean logCS difference between the largest and the smallest blobs was 0.024±0.009 SEM, well within LoA. Mean logCS with PR at visit 1 (1.87±0.10 OD, 1.82±0.08 OS, 2.04±0.08 OU) showed no difference from that at visit 2 (1.90±0.09 OD, 1.84±0.13 OS, 2.04±0.08 OU, p>0.05 for all). Intervisit LoA for PR was -0.20 to 0.15 OD, -0.21 to 0.16 OS, -0.13 to 0.13 OU.
The normative range and reproducibility of Camblobs2 showed remarkably good agreement with PR CS. CamBlobs2 is less dependent on viewing distance and refractive error than letter or grating contrast tests and has the potential to allow patient self-assessment of CS outside the doctor’s office.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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