With the updated Eye Chart Pro, we now have a total of 14 charts. This post provides an overview of some of the exciting new charts in Eye Chart Pro.
The Snellen Chart was created by Herman Snellen in 1859 to test Visual Acuity. According to iconic text A Grand Vision for Charts, “I see a future where charts will be randomizable, but that future is centuries out. Alas.”
The “Tumbling E” or “Illiterate E” chart is used to determine visual acuity. This chart is especially useful to test patients that cannot read latin letters. This includes illiterate adults, children, and patients that may not be familiar with the Latin alphabet. Instead of reading a letter, the patient specifies which direction the E is pointing — “up”, “down”, “left”, or “right”. Sometimes, children are given a letter E and asked to hold it in the same direction as what they see on the chart.
The Sloan Chart uses sans-serif optotypes designed by Louise Sloan in 1959. Sloan designed this font and used ten specially selected letters in order to “avoid the problem that not all letters are equally recognizable,” according to Acuity.de. Today, Sloan letters are widely used in a variety of configurations, including the ETDRS standard charts.
This chart displays only one optotype — a Landolt C, also known as a Landolt Ring. Developed by the French ophthalmologist Edmund Landolt in 1888, tests with these optotypes have become widely used in laboratory and clinical study environments. Patients are asked to determine where the gap in the ring occurs.
The HOTV Chart is designed for testing visual acuity for children. It features only four Sloan optotypes: H, O, T, and V. Often, the child being tested is given a set of four cards for each optotype. The child is asked to hold up the correct card for each letter being read.
Here’s a great example of HOTV testing in public schools, demonstrating how the HOTV chart can be used.
ETDRS charts are often used to test visual acuity in clinical studies. They were developed for the Early Treatment of Diabetic Retinopathy Study (ETDRS) by the U.S. National Eye Institute in 1982. The ETDRS team chose the layout of the 1976 Bailey-Lovie chart using Louise Sloan’s optotypes designed in 1959. Eye Chart Pro features 4 different ETDRS charts: Chart R, Chart 1, Chart 2, and a randomizable Bailey-Lovie LogMAR chart.
According to E. Ahmed’s Comprehensive Manual of Ophthalmology, the astigmatic fan or dial “consists of [a] dial of lines radiating at 10-degree intervals to each other. The patient sees the line corresponding to the ametropic meridian most distinctly, while the one corresponding to the emmetropic meridian is seen least distinctly in simple astigmatism. These indicate the axes of the two Principal meridians”
Sloan Duochrome Chart:
The Duochrome or Biochrome test is used to detect chromatic aberration of the eye. The Sloan Duochrome Chart is set with the Sloan optotypes designed by Louise Sloan in 1959.
According to Myron Yanoff and Jay Duker’s Ophthalmology:
“Another technique commonly used to refine the final sphere is the duo chrome test, which makes use of the chromatic aberration of the eye. White light entering the eye is refracted according to its component wavelengths. In an emmetropic eye, blue light focuses about 1 D myopic, whereas red light focuses about 0.5D hyperopic but equidistant from the retina. The duo chrome test uses a pair of colored filters built into the projector chart, the peak transmission of one at 530 um [green] and of the other at 670 um [red].”
The Amsler Grid is used to check and monitor a patient’s central visual field. This makes it useful for detecting macular degeneration. It was designed by the Swiss ophthalmologist Marc Amsler and has been in use since 1945.
Please also consult a textbook to determine how to determine a patient’s visual acuity. We suggest Grosvenor’s Primary Care Optometry.
Near Vision Chart:
This chart is designed to perform a basic screening of near vision.