Teller Acuity System Vs Lea Gratings® Products                                                View Shopping Cart

In adults, visual acuity is measured as 'recognition acuity' which uses standard line tests. This type of test cannot be used in examining infants and children with multiple handicaps. Visual acuity in this younger group can be measured with grating acuity tests.

In a grating acuity test, the infant or child detects the presence of parallel lines of decreasing width, a task simpler than recognizing optotypes. When a striped pattern is presented in front of the young patient simultaneously with a gray surface of the same size and luminance, the young patient is likely to look at the striped pattern because there is more to see than on the gray surface.

In addition to gratings, the Teller System uses a large blind behind which observations are made. This unit requires substantial table space and is very awkward for the examiner. Since the Lea Gratings® do not require a cumbersome blind between examiner and the young patient, the Lea solution is much more economical and useable than the traditional Teller Acuity System.

The Lea Gratings® Test test uses paddles to present gratings. The handle allows the tester to hold the test easily. The gratings are defined by the frequency, i.e., the number of pairs of black-and-white stripes or cycles, within one degree of visual angle. When the grating is printed on a surface, it can be defined also as the number of cycles per centimeter of surface.

When a grating is held at 57cm (~2 feet) distance from the young person's face, one centimeter equals one degree of visual angle. This is a convenient test distance because the number of cycles/cm corresponds to grating acuity as cycles per degree.

Infants and children at an early development level many not respond to stimuli placed at 57cm distance. Their visual sphere mat be limited to less than 30 cm (~one ft.). When the gratings are held at half the 57cm distance, the number of cycles per degree (cpd) is half of that at 57cm. If the infants response can be elicited only at 15cm (~6 inches) (or ¼ of the original distance), the frequency of the grating is ¼ of the value printed on the test. At one meter, the values are twice the values printed on the test.

Lea Gratings® Test

New Cardiff Acuity Test Set 

Teller Acuity Card Set