Keratoconus Support Group
Keratoconus is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal even curve. Keratoconus can cause substantial distortion of the vision, with multiple images, streaking and sensitivity to light all often reported by the patient.
I would recommend Scleral lens over RGP lens, as RGP lens can cause some scarring of the cornea (they did to me). Scleral lens vault over the eye so should not cause scarring. They are also more comfortable and most importantly Scleral lens are extremely stable and bulletproof. With RGP lens, I could have a piece of dust irritate my eye to the extent that I could hardly keep it open. This could happen anytime - sometimes while driving, so I was left with only one functioning eye. Scleral lens are bullet-proof.
So if you can get by with soft contacts, then those are the most convenient, but I would still recommend a hard lens to help slow down the progression. For a pilot (or any profession where vision is vital) I would recommend scleral lens. I use SynergEyes brand with success, while the poster above me uses BostonSight brand. If one type doesn't work, try the other type. I have steep corneas but was able to be fitted with a single visit.