Phenylketonuria does not cause cataracts.

In a study of 46 adults aged 28-71 years with untreated phenylketonuria (PKU) there were 3 (6.5%) with cataracts. This incidence was similar to that in the Australian population and in a control series of intellectually disabled adults. Only two of the PKU patients with cataracts could be examined by slit-lamp biomicroscopy and in both the findings suggested that the prolonged use of phenothiazines may have played a role. Slit-lamp examination of a further ten untreated PKU patients and 13 PKU adults who had been treated in childhood revealed only small lens opacities (in 40%) of a type found in 72.7% of a control group. The study provides no support for claims that PKU can cause cataracts.