Esotropias (crossed eyes)THE PROBLEM
We all love those accommodative esotropias! Or more commonly, the partially accommodative esotropias. Johnny is in Prep at school and his left eye is starting to turn in, especially after school.
Johnny’s Ret is +2.00 R and L and cyclo is +2.75 R and L. Even with this script - which is all he tolerates in the distance (although his VA is 6/7.5) - he is 3esophoria distance and 7esophoria near. MEM is +3.50 and with this add, his near phoria improves to 1eso. With a +4 add he swings to 1exo near. Johnny’s distance Rx alone doesn't reduce the near phoria enough to allow him to last a day at school comfortably so we needed to consider a near add.
High add flat top 35 bifocalTHE SOLUTION
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.
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