My Facebook page recently featured an excellent article about generic reading glasses and I thought I would add a few details based on my clinical experience. Several assumptions are made : your eyes prescriptions are equal? you don’t have astigmatism and most commonly wrong- where your eyes position in your head. I regularly measure the ‘optical centers’ of over the counter reading glasses and they are always set in a wider than usual position. If, you are female(eyes generally set closer together) and/or you have a narrow face with narrow set eyes, these generic reading glasses are virtually guaranteed to be misaligned. The misalignment(mm) multiplied by the power in the lens creates a ‘prism’ effect. The higher the power, +2.50 and up, are most likely to force excessive convergence of your eyes when using the eyeglasses. Headaches, eyestrain, drowsiness and a “weird pulling sensation” are common complaints. My recommendation, scatter some of these inexpensive glasses around the house, in the glove compartment, toolbox, etc. When read or use the computer for any length of time , have a quality pair made just for you!