Dr. Lew and his coinvestigators measured the levels of the protein alpha-synuclein in the tears of 55 people with PD and compared them with levels in the tears of 27 age- and sex-matched controls. They also measured oligomeric alpha-synuclein, an abnormal form of the protein whose aggregates are implicated in nerve damage in PD.
The test administered is based on a Schirmer’s test, which is used in ophthalmology to measure tear production. A strip of paper is placed in the lower eyelid pouch to collect tears, which the researchers then can analyze using commercially available assays.
Dr. Lew and his colleagues found levels of the oligomeric form of alpha-synuclein to be significantly greater in PD patients than they were in controls: an average of 1.45 ng/mg of tear protein, compared with 0.27 ng/mg in controls (P = .0007).
Total alpha-synuclein was decreased significantly in PD patients relative to healthy controls.