Simple tests to detect possible vision problems. Correct eye problems in time will avoid more complicated issues in the future.
Visual acuity test
The aim of this test is to assess the range of visual acuity (central vision) in distant vision and in near vision, by using optotypes.
Each optotype is designed according to the age or capacity of the patient. Some of the optotypes used include the optokinetic drum, the preferential gaze test, Pigassou drawings, the Snellen chart, numbers or letters.
Drawing by Madame Pigassou.
Other optotypes come in the form of an animated music video, which we call retinofilms. These are used in check-ups for younger children when measuring refractive errors (retinoscopy).
One of the steps in the visual acuity test is to compare vision in one eye with the other, by looking at the same object or text from a distance. If there is a different visual perception when comparing them, this could indicate a refractive error, pathological cause or strabismus.
The clock test can help detect astigmatism. If one of both of the hands of a clock are blurred when looking at it with only one eye, then this could indicate an astigmatic refractive error.
This test detects macular pathologies (in the central retina) by staring at a grid from a close distance (30 cm) with only one eye. The test should always be carried out with best-corrected visual acuity (glasses where necessary). While staring at the central dot on the grid, the patient should see each square as empty, and the lines should not be wavy or distorted.
Amsler grid test instructions
- Stand about 35 cm from the screen.
- If you require corrective lenses for far-sightedness, you should wear them.
- Carry out the test first on one eye, and then the other.
- Stare at the dot in the centre of the grid. The dot should not disappear.
You should be able to see the edges of the grid at all times. The horizontal and vertical lines should not disappear and should stay parallel. Any result that differs from the expected, or any change, could be a sign of macular alteration. If this is the case, you should consult your ophthalmologist.
The Hirschberg test is used to rule out strabismus. The test is quick to carry out and very useful for babies or patients who cannot actively participate. It is an objective test in which you need to see whether the reflection in both corneas is symmetrical, after shining a light into both eyes with a flashlight.
The test is easy to do by looking at your own photos, or photos from family or friends. Check to see the flash reflections in both eyes (the points of light). They should be symmetrical. Otherwise, this could be a case of strabismus.
Questionnaire to help detect vision problems in your child. If the answer to these questions is YES, we recommend booking a visit to the ophthalmologist:
- Your child sits very close to the television or brings the paper very close to read or write.
- They blink frequently or always wink one eye.
- They squint in order to see.
- They twist their head when they want to fix their gaze.
- They suffer from headaches.
- There is a notable difference in the vision of one eye compared with the other.
- Their eyes are frequently red.
- Their eyes regularly have styes or peeling skin near the eyelashes.
- They have crossed eyes (strabismus).
- You have a family history of eye problems.
- Your child’s pupils look white.
- Your child has trouble reading and writing.
Retinoscopy using animated films or "retinofilms"
This is a cover test used to make a child pay attention to a fixed faraway point during a retinoscopy. The aim is to monitor the patient’s ocular accommodation (focus) during the objective refraction test. Cartoon videos help hold the children’s attention during the test. They include numbers and letters in the centre of the image and they are accompanied by music.