How is Vision Tested in children?
Optical coherence tomography (OCT) is a non-invasive imaging test that uses light waves to take cross-section pictures of your retina, the light-sensitive tissue lining the back of the eye.
There are many procedures used to test different visual functions. Some tests can be carried out by professionals such as nurses, special education teachers or general practitioners, while others may require more specialist knowledge or equipment such that an optometrist or ophthalmologist may possess.
Visual Acuity
Visual Acuity measures the ability to read the letters on an eye chart. It is the most common clinical measurement of visual function. The standard definition of normal vision is 6/6 (metric) or 20/20 (imperial). In young children vision is measured using symbols and pictures. Children who can’t understand these tests are shown different sized stripes and their behaviour is observed.
Visual Fields
A Visual Field test measures the field of vision (side vision). This is where you look straight ahead at a particular point in a bowl-shaped machine. Each time you spot dots of light you click a button. This is referred to as computerized visual field testing. Alternatively, it can be performed manually whereby a light is brought in from the side of the machine and slowly moved to the center of vision. You press a button as soon as you see the light. The results are then marked on a chart and compared with the results a person with normal vision would be expected to see. A normal visual field is described as being about 140 degrees in every direction. Assessment of visual fields becomes relevant around 8 years of age.
Colour Vision
Colour vision can be assessed by different methods, but the most commonly used test is the Ishihara Colour Vision Test. The Ishihara is a booklet that shows numbers composed of different coloured dots. The numbers are printed within different coloured dotty backgrounds.
Electroretinogram (ERG)
The ERG is used to measure the function of the retina and identify layers of the retina that are not working properly. In some cases it can detect very early signs of RP. It involves placing special electrodes either in the eye or close to the eye. Flashes of light are used to stimulate the retina and the electrodes measure the electrical response of the retinal cells to the flashing lights.
Optical Coherence Tomography (OCT)
The OCT takes cross- sectional images of the retina. It can measure the thickness of the retina and detect any retinal abnormalities such as macula odema which can occur in patients with RP.
Fundus photographs
Using special cameras, photographs are taken of the retina to document RP related eye changes.
Visual Acuity
Visual Acuity measures the ability to read the letters on an eye chart. It is the most common clinical measurement of visual function. The standard definition of normal vision is 6/6 (metric) or 20/20 (imperial). In young children vision is measured using symbols and pictures. Children who can’t understand these tests are shown different sized stripes and their behaviour is observed.
Visual Fields
A Visual Field test measures the field of vision (side vision). This is where you look straight ahead at a particular point in a bowl-shaped machine. Each time you spot dots of light you click a button. This is referred to as computerized visual field testing. Alternatively, it can be performed manually whereby a light is brought in from the side of the machine and slowly moved to the center of vision. You press a button as soon as you see the light. The results are then marked on a chart and compared with the results a person with normal vision would be expected to see. A normal visual field is described as being about 140 degrees in every direction. Assessment of visual fields becomes relevant around 8 years of age.
Colour Vision
Colour vision can be assessed by different methods, but the most commonly used test is the Ishihara Colour Vision Test. The Ishihara is a booklet that shows numbers composed of different coloured dots. The numbers are printed within different coloured dotty backgrounds.
Electroretinogram (ERG)
The ERG is used to measure the function of the retina and identify layers of the retina that are not working properly. In some cases it can detect very early signs of RP. It involves placing special electrodes either in the eye or close to the eye. Flashes of light are used to stimulate the retina and the electrodes measure the electrical response of the retinal cells to the flashing lights.
Optical Coherence Tomography (OCT)
The OCT takes cross- sectional images of the retina. It can measure the thickness of the retina and detect any retinal abnormalities such as macula odema which can occur in patients with RP.
Fundus photographs
Using special cameras, photographs are taken of the retina to document RP related eye changes.
The slit lamp microscope magnifies the retina during a routine Ophthalmology eye test.