What is the best treatment for dry, sandy feeling eyes? My eyes seem worse in the summer.

Dry eye treatment. Your description sounds like dry eye. Initial treatment is frequent artificial tears during the day, ointment at night, warm compresses a few times a day, and omega-3 fatty acid supplements. If no improvement, you should see an eye doctor for further evaluation.
Dry . Dry eye is a common medical condition that results from an inadequate tear film. The normal tear film constantly coats the surface of the eye with moisture. This moisture is needed for good vision and eye health. In dry eye, the tear film evaporates easily and allows dry areas to develop on the eye surface. This will cause red and sandy feeling eyes. Other common symptoms of dry eye are blurred vision, and watering eyes from the irritation. Fortunately, dry eye has many treatment options. Over-the-counter lubricating drops, also called artificial tears, will often help. For best effect, artificial tears should be used at least three times daily. There are many different brands of artificial tears, and it is best to try a few different brands to see which gives the most relief. Some patients also benefit from oral omega 3 fatty acid supplements, e.g., fish oil or flaxseed oil. To ensure proper diagnosis, see your ophthalmologist who can also offer more advanced dry eye treatment, if needed.