Optic disc tilt is caused by the posterior bulging of the wall of a highly myopic eye and the oblique entry of the optic nerve into the sphere, resulting in a posterior displacement of one side of the optic disc (mostly the temporal side), causing the optic disc to lose its normal slightly vertical oval shape and become a significant vertical (or lateral, oblique) oval shape, even like a skip, under the examining eye. Genetics has been identified as a major factor in optic disc tilt. The mode of inheritance is autosomal recessive, dominant and X-linked, with a high degree of genetic heterogeneity. In addition to genetic inheritance, acquired environment such as general health, living environment, personal habits, and prolonged near-eye work can contribute to the increase of myopia. Differential diagnosis of optic disc tilt: 1. tigroid fundus The entire fundus is slightly dark gray, plus the choroid has reduced or disappeared due to diffuse atrophy, capillary layer and middle vascular layer, and the large orange vascular layer is exposed, making the fundus leopard skin-like. 2. Optic disc tilt and myopic arc As the posterior part of the wall of the highly myopic eye bulges backward, the optic nerve enters the sphere obliquely. One side of the optic disc (mostly the temporal side) is displaced backward, so that the optic disc loses its normal slightly vertical oval shape and becomes a significant vertical (or lateral or oblique) oval shape under the examiner’s eye, even like a skip. There is a crescent-shaped spot connected with the posteriorly shifted side, called the myopic arc (conus, or extended myopic arc, extended conus). The contralateral optic disc rim of the myopic arc is slightly brown, with a blurred, crest-like elevation of the supertraction conus. The medial side of the extended myopic arc is white, due to scleral exposure, and the lateral side is light brown, due to loss of the pigment epithelium and exposure of the choroid. The lateral border of the myopic arc is clear, but is often contiguous with the posterior pole atrophy area. In most cases, the myopic arc is located temporal to the optic disc, but also superior or inferior temporal. More rarely, it is located nasally or inferiorly, the former being called the inverse myopic arc (inversive conus); the latter being called the Fuchs arc (Fuchsconus). When the temporal myopic arc extends outward, upward, and downward continuously, it can surround the entire optic disc, which is called peripapillary chorioretinal atrophy (circum papillary chorioretinal atrophy). 3.Macular hemorrhage and Fuchs’ spot Macular hemorrhage is the hemorrhage of the choroid (neovascularization or no neovascularization). It is dark red, usually round, variable in size and number. It is mostly seen in the macula or below its nearby retinal vessels. Repeated hemorrhages in the same location may cause pigmentation and lead to the formation of Fuchs spots. Typical Fuchs spots are round or oval in shape, with clear boundaries and slight elevation. The size is 0,3 to 1 PD, black, and sometimes hemorrhage is visible at the edge of the dark spot. Fuchs’ spots can be seen in one or both eyes, and occasionally two black spots are seen in the fundus of one eye. 4.Posterior pole atrophic spots and lacrimal-like damage Choroidal retinal atrophic spots are white or yellowish white. Round or map-shaped. They vary in size and number, and are isolated or fused into large patches. Large atrophic spots may be connected to the peripapillary atrophy and become a large atrophic area including the optic disc and macula. There is often pigment accumulation within the atrophic spots or at their edges, and sometimes residual large choroidal vessels can be seen. The macular atrophy and its vicinity can often be seen as branching or reticulated white or yellow-white lines, which are similar to angioid streaks in the fundus, with varying widths and uneven or jagged edges, resembling old lacquer cracks, hence the name lacquer crack lesion. Lacquer crack lesion occurs in the macula and between the optic disc and macula, which is caused by the atrophy of pigment epithelium at the Bruch’s membrane chancre, and the FFA is translucent fluorescence. 5.Macular cystic degeneration and macular fissure Under the examination lens, a well-defined circular red spot with a diameter of 1/3-1/2 PD can be seen in the macula, and the retina around the red spot is slightly grayish, if accompanied by limited detachment with a reflective circle around it. On slit lamp microscopy, there is a thin anterior capsule wall tangent on the photomicrographic surface in the case of cystic degeneration, and this line is interrupted in the case of lacunae. There is a misalignment between the tangent line of the outer wall of the fissure and the tangent line of the surrounding retinal surface. 6.Posterior scleral staphyloma The posterior sclera of the eye is over-extended and the posterior pole can be limitedly dilated, forming posterior staphyloma. The posterior staphyloma is like a petri dish or crater-like depression under the examination eye, and the edge can be slope shaped or sharply steep, and the retinal vessels are curved and crawling at the edge. The difference in refractive power between the base of the posterior staphyloma and its rim is significant, and this difference in refractive power is an important basis for the diagnosis of posterior staphyloma.