Low level technology tool (LLTT) in screening for blindness: test qualities in the outpatients department of a tertiary eye unit using the Snellen chart.

OBJECTIVE

To validate the use of finger counting (low level technology tool) in screening for blindness in the outpatients department of a tertiary eye unit with the view of employing the test for screening illiterate people in hard to reach parts of the country where the conventional visual acuity charts are not available.

DESIGN

Aperformance evaluation of counting fingers (LLTT) in screening for blindness against the standard test (Snellen chart).

SETTING

Sekuru Kaguvi Eye Unit, Parirenyatwa Hospital, Zimbabwe.

SUBJECTS: Patients presenting to the Eye Outpatient Department at Sekuru Kaguvi Eye Unit with various eye problems.

MAIN OUTCOME MEASURE: Sensitivity of low level technology tool (LLTT) in identifying blind people.

RESULTS

Sensitivity and specificity of LLTT in detecting blindness in all age groups combined was 100% and 88.5% respectively. Although sensitivity was not affected by patient age, specificity decreased with increasing age. The overall positive predictive value for the test was 53.3% and the prevalence of blindness among outpatient attendees was 11.6%.

CONCLUSION

Finger counting is an effective tool that can be employed in screening for blindness in communities which are hard to reach, have low literacy rate and when conventional methods of testing visual acuity are not available.