The present invention provides novel methods for treating diseases associated with apoptotic degeneration in ocular tissue cells by effective administration of pigment epithelium derived factor (PEDF). The present inventors studied PEDF as a means to prevent ganglion cell death, the final pathology of glaucoma. The present invention is particularly focused on SIV vectors for effective methods for delivering PEDF, and constructed an SIV-PEDF vector. When the SIV-PEDF vector was administered subretinally to an ischemia reperfusion model and NMDA-induced model, a significant suppression effect on ganglion cell death was observed. The present inventors therefore discovered that the SIV-PEDF vector is an effective pharmaceutical agent for treating diseases associated with apoptotic degeneration in ocular tissue cells, such as glaucoma.