There are many types of sunglasses available, but no single type is ideal for every pilot. Needs change based on age, light sensitivity, ambient lighting conditions and type of flying. Some sunglasses are not right for any pilot at any time. Valid reasons for wearing sunglasses in the aviation environment include improved night vision adaptation, enhanced contrast in the visual field, reduced glare, decreased UV exposure and avoidance of eye fatigue. Though style and appearance may be a consideration, the safety conscious pilot should focus on the proper selection of lens features rather than frame styles with cheap lenses.
Visual acuity varies with the light available and the sensitivity of an individual to various degrees of brightness. The pupil controls the amount of light reaching the retina. Older individual's eyes do not transmit as much light through the eye as younger people do. Therefore, many older individuals need more light for optimum acuity. They may want to use sunglasses that transmit more light. On high glare days, such as over snow or sand, the pupils contract to protect the eye from the glare. Sunglasses will reduce glare and allow the pupil to let more light on to the retina, thus enhancing vision.
So, you need to make sure in which aviation condition the sunglasses used for. Then you can choose a right pair for flying.