Having such high glass number has risk of Retinal Detachment , so Detailed Retina checkup is necessary on regular basis Doing a surgery to remove glasses number will be helpful in this case which will visually rehabilitate

High myopia is  associated with increased risk of retinal tears leading to retinal detachment ( where light sensitive layer of eye gets pulled away from its normal position ) , primary open angle galucoma , myopic macular degeneration.A  detailed examination by retina specilaist is important and regular follow up as per the ophthalmologist is advised .Exercises involving risk of direct head or eye trauma like boxing to be avoided.sky diving , bungee jumping can also be avoided.

Such a high power is a risk factor for retinal detachment as the retina is stretched and thinned out in periphery due to large size of eyeball. He/she should get detailed retina examination. Sometimes small holes/breaks are present in peripheral part of retina which can be lasered (OPD procedure) to prevent any further complication.

Since his power of glasses is -11 D he has quite a few issues in his daily activities.Going for ant surgery to reduce the IOL power might make his life a little comfortable but will be associated with great risk due to thin cornea and retina.He should have  a regular visit to a retina specialist and try to manage his condition as conservatively as possible

High myopia is associated with some increased risk of retinal detachment,  though the incidence is still less... Routien check up with retina specialist is a good idea.if advised , barrage lase can be done to reduce that risk.