The use of 95% ranges for TRV to establish the smallest measured visual acuity change that can be reliably detected ensures a high specificity but does not take account of sensitivity. Use of change criteria derived from published 95% ranges results in a sensitivity of approximately 50% (assuming identical levels of TRV). Sensitivity may be improved by using a change criterion that is smaller than the minimum change sought, providing the change criterion is still at least as large as the 95% range for TRV, so that specificity is maintained. Reducing TRV allows smaller changes in acuity to be reliably detected.

Background/aims-The advantages of logMAR acuity data over the Snellen fraction are well known, and yet existing logMAR charts have not been adopted into routine ophthalmic clinical use. As this may be due in part to the time required for a logMAR measurement, this study was performed to determine whether an abbreviated logMAR chart design could combine the advantages of existing charts with a clinically acceptable measurement time. Methods-Thetest-retest variability, agreement (with the gold standard), and time taken for "single letter" (interpolated) acuity measurements taken using three prototype "reduced logMAR" (RLM) charts and the Snellen chart were compared with those of the ETDRS chart which acted as the gold standard. The Snellen chart was also scored with the more familiar "line assignment" method. The subjects undergoing these measurements were drawn from a typical clinical outpatient population exhibiting a range of acuities. Results-The RLM A prototype chart achieved a test-retest variability of +/−0.24 logMAR compared with +/−0.18 for the ETDRS chart. Test-retest variability for the Snellen chart was +/−0.24 logMAR using clinically prohibitive "single letter" scoring increasing to +/−0.33 with the more usual "line assignment" method. All charts produced acuity data which agreed well with those of the ETDRS chart. "Single letter" acuity measurements using the prototype RLM charts were completed in approximately half the time of those taken using the ETDRS and Snellen charts. The duration of a Snellen "line assignment" measurement was not evaluated. Conclusion-The RLM A chart oVers an acceptable level of test-retest variability when compared with the gold standard ETDRS chart, while reducing the measurement time by half. Also, by allowing a faster, less variable acuity measurement than the Snellen chart, the RLM A chart can bring the benefits of logMAR acuity to routine clinical practice. (Br J Ophthalmol 2001;85:432-436)

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Displacement of the macula is common following RRD repair and heterogeneous in nature. Most affected patients are symptomatic in the early postoperative period.

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