Grating acuity with varying field size in patients and normal infants

Abstract

PURPOSE To investigate the effect of field size on grating acuity assessment in normal children and pediatric ophthalmological patients. METHOD A prototype set of acuity cards was produced with three acuity steps per octave and a card size of 26 × 70cm, bearing a grating field of 26 × 35cm. Field size reduction was achieved by masking. Large fields of the prototype versus TAC-sized fields were tested in normal infants and ophthalmological patients. RESULTS Teller acuity cards (TAC) and masked prototype cards of equal field size gave identical results in normal controls and pediatric ophthalmological patients.A better response to large fields was found in all normal infants up to 7 months of age and in none older than 15 months. In patients, an effect of field size was found in decreasing numbers up to 5 years of age. The interocular acuity difference was larger when small fields were presented. CONCLUSION The effect of field size in patients is considered to be a developmental delay due to the individual history of disease. It may possibly have prognostic value for treatment.