Measurement of the intra-ocular pressure

Intra-ocular pressure (IOP) measurements were performed on male and female WT, Mut-XDH ^Tg/glaucoma⁺ and Mut-XDH ^Tg/glaucoma⁻ mice 3 to 7 months of age. Pilot experiments performed in the same conditions demonstrated no significant difference between the IOP of male and female WT mice. For this reason, our analyses do not take into account sex and aggregated results are presented (Fig. 3B). A validated commercial rebound tonometer (TonoLab, Vantaa, Finland) with tip positioned at 2–3 mm from the eye³⁹ was used for all the measurements. For each animal, the IOP of both eyes was measured. A mean of 3 measurements for each eye was performed and each measurement was repeated 10 times to obtain the overall mean. Measurements were accepted only if the complied to the standards described in the manufacturer’s manual. All measurements on weighed and non-anesthesized animals and were performed between 9.00 and 12.00 p.m. a time of the day characterized by stable IOP according to our experience. Total no. of animals used: male WT = 4; female WT = 5; male Mut-XDH ^{Tg/ Glau} = 6; female Mut-XDH ^Tg/Glau = 1; male Mut-XDH ^Tg/Glau = 4; female Mut-XDH ^Tg/glaucoma⁺ = 5.