Choosing a bifocal firstly allows a wider reading area (and we know when Johnny is looking through it – set higher than it would be with an adult) and also lets us use the stronger add of +4 to reduce the accommodation and thus the stimulus to esophoria (which breaks down to an esotropia by the end of the day).
With many low vision patients, more can be seen for near tasks with a stronger add. Of course, they know they have to hold things closer, but the increased magnification can allow smaller print to be read. However, progressive lenses limit the field of view and so are of limited value. They also don’t come in strong enough adds to be as useful. It can be frustrating for low vision patients to have two pairs of glasses to make the reading a stronger add, because their lower vision can mean they are prone to losing those separate glasses.
A bifocal with a stronger add can make a real difference to the quality of life for someone with low vision. I have used bifocals with adds of +5-6 in these situations and the patient loves the way they wear them constantly rather than losing the glasses.