Often seen by your grandfather wearing these, Bifocals are used for presbyopic cases that require separate power for near and distance, or to correct a wider range of severe vision issues. Easily differentiated from multifocals as the lens have a distance and near portion segmented with a visible line all within one lens making them great for those that require a large and clear vision for each portion. Thus versatile for long hour usage. However this also means there will be a drastic change in vision correction as you move your eyes within the lens