Wherein the geranylgeranyl acetone contains 0.00001 to 95% by weight of geranylgeranyl acetone, wherein the geranylgeranyl acetone comprises (a) only one particular geranylgeranylacetone geometric isomer or (b) one specific geranylgeranyl acetone geometric isomer in an amount of 80% % Or more of geranylgeranyl acetone geometric isomer mixture, the preventive, ameliorative or therapeutic agent for retinal diseases exhibits sufficient prevention, improvement or therapeutic effect of retinal diseases which is sufficiently practical in practice.ゲラニルゲラニルアセトンを0.00001~95重量%含有し、該ゲラニルゲラニルアセトンが、(a)特定の1種のゲラニルゲラニルアセトン幾何異性体のみ、又は(b)特定の1種のゲラニルゲラニルアセトン幾何異性体を80重量%以上含むゲラニルゲラニルアセトン幾何異性体混合物である、網膜疾患の予防、改善、又は治療剤は、実用上十分に有効な、網膜疾患の予防、改善、又は治療効果を奏する。
