An alkyl ether derivative represented by the following general formula [1] or its salt: wherein R 1 and R 2 represent each a substituent such as hydrogen, halogen or alkyl； R 3 represents alkylamino, amino or hydroxyl； the ring A represents a 5- or 6-membered aromatic heterocycle or a benzene ring； m and n are each an integer of from 1 to 6； and p is an integer of from 1 to 3； shows an effect of protecting retinal nerve cells and, therefore, is useful as a preventive and/or a remedy for retinal nerve diseases such as glaucoma, diabetic retinopathy, retinal artery obstruction, retinal venous obstruction, macular degeneration and retinopathy of prematurity.
