Abstract: This invention relates to the prophylaxis of choroidal neovascularisation in macular degeneration by the introduction of a suitable anti-inflammatory agent into the vitreous. In particular, it relates to the prophylaxis of neovascularisation with an anti-inflammatory steroid, such as an 11-substituted 16 alpha, 17 alpha-substituted methylenedioxy steroid of formula (I) wherein (a) is (b), (c), (d), (e), (f), (g), (h), (i), (j), (k) or (l); R1 and R2 are hydrogen or alkyl; -Ca-Cb- is —CH2—CH2—, —CH?CH—, (m) or (n); R3 is methyl, hydroxymethyl or alkylcarbonyloxymethyl, methylaminoalkylenecarbonyloxymethyl, or phenylaminoalkylenecarbonyloxymethyl; R4 is alkanoyl; and X is halogen in eyes which have been identified as having a high risk of developing choroidal neovascularisation. More particularly, it relates to prophylaxis with triamcinolone acetonide, (compound II).