The invention relates to lipid compounds of formula (I) and their pharmaceutically acceptable salts for the prevention and/or treatment of ophthalmic disorders such as retinal degenerative disorders and ocular inflammatory diseases: (I) (wherein R1 is either a C9 to C22 alkyl group, or a C9 to C22 alkenyl group having from 1 to 6 double bonds； R2 is selected from the group consisting of a halogen atom, a hydroxy group, an alkyl group, an alkoxy group, an alkylthio group, a carboxy group, an acyl group, an amino group, and an alkylamino group； R3 is a hydrogen atom, or a group R2； R4 is a carboxylic acid or a derivative thereof； and X is methylene (—CH2—), or an oxygen or sulfur atom).
