introduction a logarithmic e chart to measure visual acuity at different test distances

purpose: e is a commonly use letter for illiterates or those who could not read english to measure visual acuity. the e chart is the mainly used charts in iran. however, they do not have the standards. they are in different format, fixed for 6 meter test, with or without lighting, with unequal number of letters in each line and different contrasts. as a result, there is an essential need for a standard e chart representing all the standard criteria’s. methods: the new design e chart has been developed with coreldraw® software. progression of the letter size is changed geometrically (0.1 log unit). visual acuity rating is given with logarithm of minimum angle of resolution (logmar). this chart consists of 13 rows and each row contains 5 letters. the space between two letters in each row is equal to the width of the letter at that row, and the distance between two rows is equal to the height of the letter in the row below. this chart is provided on paper based with nearly 100% contrast. results: this chart has the same facilities as other standard charts such as bailey-lovie, etdrs and mcmonnies. the cchart can be moved to any distances. to adjust chart scale at other distance there is a table at the bottom of the chart. the logmar notation also can be converted into traditional snellen with another table at the end of the chart. conclusion: this chart can be used in routine clinical exams, research projects, low vision patients as well as illiterate people.