Refsum&;s disease is due to deficiency of which of the following enzyme?

It is a metabolic error due to lack of alpha-hydroxylase (phytanic acid oxidase) so that alpha-oxidation does not occur and phytanic acid accumulates in the tissues. The patient presents with severe neurological symptoms, polyneuropathy, retinitis pigmentosa, nerve deafness and cerebellar ataxia. Regressions of symptoms are observed with restricted dietary intake of phytanic acid. Milk is a good source of phytanic acid, which may be avoided.Ref: DM Vasudevan, Page no: 135