Birefringence images of screw dislocations in Gadolinium Gallium Garnet (GGG) and Yttrium Aluminum Garnet YAG) crystals are studied in detail. Birefringence images of screw dislocations viewed end-on were observed for the first tiane. The one-to-one correspondence between birefringence images of screw dislocations viewed end-on and that viewed from the side was demonstrated. The contour of equal intensity of birefringence image of screw dislocation viewed end-on in GGG and YAG crystals was derived by considering the photo-elastieal anisotropy of garnet, and the result yields good agreement Avith experimental observations.