Following enucleation, retinae were dissected, flash frozen on dry ice and stored at −80 °C prior to use. Tissue was homogenised in TRIzol Reagent (Life Technologies) and total RNA isolated using RNeasy spin columns (Qiagen) with on column DNase treatment (Qiagen). 1 μg of total RNA was reverse transcribed using SuperScript III with oligo(dT)20 primers (Life Technologies) and quantitative PCR performed using Quantifast Sybr Green PCR mastermix (Qiagen) on a StepOne thermal cycler (Applied Biosystems) as described previously95. Quantification of transcript levels was performed using a comparative CT approach with levels of target gene expression normalised to the geometric mean expression of three house-keeping genes96. K2P channel primers were designed using PrimerBlast (NCBI). Primer sequences are shown in Table 2.