Complex sentence: Despite continued anecdotal reports of successful results, Bates' techniques have not been objectively shown to improve eyesight, and his main physiological proposition--that the eyeball changes shape to maintain focus--has consistently been contradicted by observation.
Split into simpler sentences: Despite continued anecdotal reports of successful results, Bates' techniques have not been objectively shown to improve eyesight. His main physiological proposition--that the eyeball changes shape to maintain focus--has consistently been contradicted by observation.