Occasional blurry vision with worsening in bright sunshine is likely related to dry eyes. Your eyes do not necessarily have to feel dry; rather, the initial symptom is blurry vision as the tear film begins to evaporate quickly. It happens most frequently to people that spend their day performing tasks that require concentration. For example, computer work, reading or driving.
Your glasses or contact lens prescription can be perfect and still the dry eyes will cause episodes of blurry vision.
I recommend the following:
1. Drink 1 to 2 liters of water per day - this will provide the hydration necessary for proper tear production
2. Decrease caffeine intake (coffee, soda, tea, chocolate, etc)- these tend to dehydrate
3. Artificial tears 3 to 4 times per day - this will help replenish the tear film and stabilize the vision. Artificial tears can be purchased over the counter at any pharmacy.
-There are more advanced dry eye treatments, however, this is a good place to start. If this doesn't relieve the symptoms I encourage a visit to an ophthlamologist that can evaluate the dry eyes and provide more advanced treatment options.
I hope this is helpful...