In our study we made 4 major observations.1. The mental symptoms of patients whose eyes were patched bilaterally were found in a higher incidence than hitherto reported, particularly in patients with detachment of the retina.2. We identified a new symptom—non-compliance to instructions.3. Non-compliance occurred most frequently in our patients during sleep or on awakening, as did also pseudo-hallucinations.4. Surgical complications were greater in those patients undergoing cataract extraction, who developed mental symptoms during the period of bilateral patching of the eyes as compared to those without mental symptoms.The coincidence of sensory deprivation and hypnagogic or other periods of reduced awareness may contribute to an understanding of the sensory deprivation effects. More work needs to be done. It would seem imperative to ascertain to what extent periods of reduced awareness occur with the daytime symptoms of our sensory deprivation situation and that in other sensory deprivation experiments. The higher mental functions of inhibitory control, discriminative logic, and both vigilance and tenacity of attention are impaired during periods of reduced awareness. The delirioid symptoms which became manifest in our patients who had brain damage in addition to their eye disease are probably also precipitated more readily at times of reduced alertness.