Complete Sonksen Logmar test Kit including Book “E”

The Sonksen logMAR Test (SLT) has been designed to measure distant and near acuity in strict
accord with specifications laid down for the logMAR scale, Bailey and Lovie (1976). The
logMAR scale is currently accepted as the international standard and recommended for the
measurement of visual acuity.
To ensure uniform crowding of all test optotypes, crowding bars as specified in the logMAR
standard surround every test display. As a consequence measures obtained with the SLT are both
meaningful and directly comparable with the international scale. The developmental
modifications incorporated in the SLT are those introduced by Sonksen into the Sonksen-Silver
Acuity System (SSAS) – a test drawn to Snellen specifications, Sonksen and Silver (1988).
Our team has demonstrated rapid changes in linear optotype acuity between two and a half and
five and a half years with slower though continuing improvement until at least 9 years, Salt et al
(1995), Wade et al (1995). Age norms are therefore essential for meaningful interpretation of
measures in this age group. We constructed age norms for 3/3 and 3/4.5 and demonstrated
excellent compliance with the developmental demands of the SSAS in the youngest age groups,
Salt et al (1995), Wade et al (1995). To date the SSAS remains the only crowded optotype test to
be published with norms and compliance data.
The advantages of the logMAR over the Snellen standard are a regular progression (base 10) of
both letter sizes and spacing from one level to the next and an equal number of letters at each
level; scoring takes account of each letter correctly identified by the testee, resulting in increased
sensitivity and repeatability of measurement, Taasch et al (1998). Another advantage is an
increased number of levels within a given acuity range which serves to accommodate the rapid
changes in acuity of the under fives.
The SLT was designed by Sonksen and developed by our research team. The displays in the
prototype distant (3 metre) test booklets for the research ranged from logMAR 0.775 to
-0.300. The cohort for collection of the scientific data comprised 2991 children aged 24 to 103
months. We present the SLT together with acuity age norms in the form of centile charts and
compliance data for age, for the distant test, Wade et al (2004), Sonksen et al (in preparation),
Salt et al (in preparation).
Scientific Background