The Amsler Charts group shows a variety of charts designed to identify scotomas and distortion within the central visual field.

The Thomson Near Chart allows these areas to be indicated by “drawing” directly on the grid using a finger on the tablet/phone. This image may then be placed in the Windows clipboard by selecting Copy.  The annotated grid can then be pasted into a word document, patient management software etc.

The spacing of the Amsler grids is determined by the pixel size – each line must be separated by the same number of pixels. The spacing of the lines (in pixels) may be adjusted using the Spacing control.  The angular subtense of the grid is calculated for the current Near Viewing distance and displayed below. It is generally based to vary the spacing until  the grid is 0.5 degrees.

The Thomson Near Chart allows a wide variety of grids to be generated including Squares, Vertical lines (V lines), Horizontal lines (H lines) and Dots (Dots). These charts may be selected from the Format list.

The contrast/colour of the grid may be reversed, i.e. white on black, red on black etc. using the Colour list.

The size and shape of the central fixation target can be selected from the Fixation list.

Enabling drawing

The Thomson Near Chart allows the patients to indicate "blind spots" and areas of distortion on the grid by tapping directly on the tablet/phone.  To enable this functionality, select Enable drawing.

When the patient then taps on the screen, a red dot will be displayed as shown below:

NOTE:  There will be a delay between tapping and the dot appearing on the device,  This is because the position of the tap has to be sent via the server to the PC, the image has to be regenerated and then sent back to the device. The delay will depend on the speed of the PC and the internet connection.

Click on STOP drawing to turn off the touch screen functionality.  The points are cleared by selecting  Clear.

A copy of the grid and any associated areas identified, may be copied to the clipboard by selecting Copy.  The chart may then be pasted into a report or the patient's records as shown below.

 This image may then be placed in the Windows clipboard by selecting Copy.  The annotated grid can then be pasted into a word document, patient management software etc.