Marfan syndrome presents as a disorder with extensive disorders of mesodermal tissue throughout the body, including abnormalities of the eye, cardiovascular and skeletal systems, and is autosomal dominant. Ocular anomalies manifest as a dislocation of the lens to the superior or supra-nasal level. Ocular manifestations: more than 30% of patients have congenital cataracts and 80% have lens dislocation, mostly partial supra-nasal or total dislocation in the anterior chamber or vitreous. In a few patients, the lens is spherical. The anterior chamber angle is abnormally developed and may be combined with glaucoma. The iris dilation muscle is dysplastic and the pupil does not shift to dilate. There may also be myopia, congenital large corneas, small corneas, and no iris. Systemic manifestations: spider fingers (toes), elongated bones, chicken or barrel chest, aortic coarctation aneurysm and dysplasia. The cause of Marchesani syndrome is unclear, with autosomal dominant and invisible modes of inheritance. The main manifestations are short stature, short limbs, a small spherical lens, subluxation toward the nose or total subluxation. Ocular manifestations: some patients have cataracts, small spherical lens, subnasal dislocation or total dislocation, glaucoma, and a few patients have small corneas. Systemic manifestations: short stature, thick and short limbs and fingers (toes), more obese, and short and thick neck. Homocystinuria is an amino acid metabolic disease caused by defective cystathionine synthetase, resulting in increased homocystine in the blood, which is excreted in the urine and is autosomal recessive. The ocular manifestations are ectopic lens mostly to the lower part of the nose. Ocular manifestations: some patients have congenital cataract, but lens dislocation is more common, usually subnasal or inferior dislocation, easily dislocated into the anterior chamber and vitreous cavity, may be combined with retinal detachment and degeneration, no iris and other abnormalities. Systemic manifestations: mental retardation, epilepsy in 50% of patients, elongated limb bones, osteoporosis, spider toes (fingers), generalized vasodilatation and flushing, high platelet viscosity, susceptibility to thrombosis, hypertension, heart murmurs, and cardiomegaly are also common. Traumatic lens dislocation is caused by partial or complete rupture of the suspensory ligament under external force, resulting in abnormal lens position. Clinically, lens dislocation is more common in closed eye trauma than in open eye trauma. In partial dislocation, the lens axis is deviated from the visual axis and part of the equatorial portion of the lens is visible in the pupillary area, with partial iris tremor and diplopia may occur. In total dislocation, the lens may dislocate forward into the anterior chamber and sometimes become lodged in the pupil area, both of which are prone to secondary glaucoma and corneal endothelial damage. The lens can also prolapse backward into the vitreous cavity, where the anterior chamber becomes deeper, the iris trembles, and high hyperopia or near vision disappears. If the sclera or angle sclera is ruptured, the lens may also dislocate under the bulbar conjunctiva or even out of the eye. Treatment of lens dislocation: 1. For lens dislocation without other eye injuries and complications, the preferred treatment is to correct the refractive error in the crystalline or aphakic area with glasses or contact lenses to restore proper vision. 2. Indications for surgery: (1) Lens dislocation severely impairs vision, especially with cataract (2) Lens dislocation into the anterior chamber (3) Lens dissolution glaucoma (4) Lens allergic uveitis (5) Pupillary block glaucoma, conservative treatment cannot reduce intraocular pressure (6) Lens clouding prevents examination and surgery of retinal detachment (7) Dislocated lens is mature or overripe cataract (8) Monocular diplopia due to lens dislocation (9) Best corrected visual acuity less than 0.3 3. Surgical procedures: intraocular tension ring, crystal vitrectomy, lens ultrasonic crush, combined IOL implantation.