Is it true that gas permeable contact lenses preferrable to soft lenses for dry eyes?

Not necessarily: Contacts float on a layer of tears and soft lenses allow more tears to pass through and evaporate. But soft lenses allow more oxygen to flow into the eye. So it is a compromise and quite individual - some do better with soft/some better with gas permeable hard lenses. Your ophthalmologist can help guide you and make the best recommendation.

Sometimes: Sometimes. Although gas permeable lenses may be optimal for patient with a decreased tear film (ie dry eye), most patients can safely wear soft contact lenses if their dry eye is treated appropriately.