Marfan syndrome (MFS) is a genetic disorder with clinical manifestations associated with cardiovascular, ocular and skeletal organ systems. Typical signs are descending aortic root aneurysms, ectopia lentis, tall stature and scoliosis. This observational study looked at the ocular characteristics, visual acuity and biometric values of 102 eyes in 51 patients with MFS. The mean patient age was 39 years (range, 12.7–71.6). Seventy-seven eyes were phakic, five aphakic and 20 pseudophakic. Thirty-one eyes had ectopia lentis, 12 cataract, nine strabismus, five glaucoma and four had undergone surgery for retinal detachment. Ninety-two per cent eyes had a best spectacle-corrected vision of 0.3 logMAR or better. In the 77 phakic eyes, myopia exceeding −3 D was seen in 39% eyes with ectopia lentis, and in 26% eyes without ectopia lentis. The mean axial length (AL) was 24.73mm and abnormally increased AL (≥24.5mm) in 51% eyes. No significant difference was found in refraction, axial length or corneal curvature between eyes with and without ectopia lentis. The authors conclude that in addition to ectopia lentis, increased axial length and a flattened cornea are typical characteristics in MFS. High myopia was not as common in MFS as expected because of a flat cornea.