Sjogren s severe dry eye keratitis cornel scar irregular surface break in tear film worsening , its a cycle. Have to deal primary reason, sjogren s control by immunotherapy and heal with supportive therapy like tear drops. Secondary reason for low vision is corneal scar and astigmatism due to scarring, PRK is one of the most preferred procedure for corneal scar(superficial) with astigmatism. PRK lightens scar and significantly evens the surface by reducing astigmatism which also reverts near smooth corneal surface which is very important for good tear film formation and break this cycle. Ideally before doing cataract surgery, corneal issue should be dealt first reason being there will not be vision improvement with cataract surgery without dealing cornea. PRK is well preferred procedure in your condition. Hope for the best Regards