Many different optical magnifying devices can be used to help people with low vision: spectacle magnifiers, microscopic or telescopic systems. Their guiding principle is to let visually impaired people see an enlarged image of what they’re looking at.
These are the most classic visual aids. Opticians should have a good working knowledge of them to help people with low vision make the right choice, and also to familiarize patients in how to use them. These visual aids are portable, affordable and easy to use and are of great benefit to people who are visually impaired. However, they may only facilitate a specific use or be limited to a particular task.
Instead of using magnifiers to increase the appearance of near objects, people with low vision can also benefit from magnifying systems directly mounted onto glasses: ‘magnifying spectacles’. These systems are also commonly referred to as ‘microscopic’ systems as their optical principle is similar to that of a microscope (even if their appearance is very different) but also in comparison with telescopic systems used for viewing distant objects.
Microscopic systems are relatively simple and frequently used with low vision. Their disadvantage is that they require the patient to adopt a very close viewing distance, which limits their use.
When someone who’s visually impaired needs significant magnification or the possibility of viewing at very far distances, s/he can use optical systems called ‘telescopic’ as their optical principle is like that of a telescope and thus primarily intended for far vision use.
These systems come in 2 types: Galileo or Kepler systems:
– Galileo systems
These are the oldest existing visual aids and are mainly used for distance and near vision. They can also be adapted for intermediate vision, eg for playing board games or watching television at a medium distance. For near vision, compared to identical microscopic magnification, they bring people who are visually impaired a significantly larger and more comfortable viewing distance.
– Kepler systems
Commonly known as ‘monocular’, Kepler systems are comparable in design to binoculars and facilitate focusing at different distances. They provide a specialized solution for viewing intermediate to very far distances, mainly for fast and distant observations when on the move: for example to read the name of a street or public information board.
Other magnifying systems, such as electronic systems, can provide effective additional options for people with low vision.