expression, godan verb (-su)
apply eyedrops; put in eyedrops
Standard expression for administering eyedrops. The verb 差す (or 点す) is used specifically for applying liquid drops to the eyes.
目が乾いたので、目薬を差した。
My eyes were dry, so I put in some eyedrops.
コンタクトを外してから目薬を差してください。
Please apply eyedrops after removing your contact lenses.