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2/22/96 Chapter 6 Vision Assessment page 6-1
6.1 Measurement of Visual Acuity
Chapter 6
Vision Assessment
High and low contrast visual acuity are measured by a member of the CLEK
Participating Clinic personnel Study-certified for visual acuity. The procedure for
measuring visual acuity was originally developed for the Early Treatment of Diabetic
Retinopathy Study (ETDRS) using Bailey-Lovie high contrast visual acuity charts.
The Clinician and/or Technician is/are certified by the Chairman’s Office
according to procedures outlined in Chapter 12 of this Operations Manual.
6.1.1 Introduction
Bailey-Lovie distance visual acuities are utilized during the course of the CLEK
Study. All Bailey-Lovie visual acuity charts are supplied by the Chairman’s Office from
the School of Optometry, University of California, Berkeley, CA. The chart is located at
4 meters, and the white background of the chart has a luminance as specified in Section
6.1.2 below.
At each Study Visit, visual acuity is measured in three ways in the following
order: (1) High and low contrast Bailey-Lovie visual acuity with habitual correction, for
each eye separately and both eyes together; (2) High and low contrast Bailey-Lovie
visual acuity with best correction (for rigid contact lens wearers (including Softperm
and piggyback wearers): contact lenses with optimal over-refraction, for non-rigid
contact lens wearers: a CLEK Study Trial Lens Set contact lens with base curve equal to
steep “K” plus optimal over-refraction), for each eye separately; and (3) High contrast
Bailey-Lovie visual acuity with manifest refraction, for each eye separately.
Table 6-1 shows the sequence of visual acuity measurements and the chart to be
used for each.