ABSTRACT.Purpose: To study ocular characteristics in 87 patients with verified Marfan syndrome (MFS) based on the Ghent criteria from 1996 (Ghent-1). Methods: The position of the lens was noted by observing the eye in different gaze directions in maximal mydriasis during slit lamp examination. Ectopia lentis (EL) was classified as subluxated (dislocation slightly backwards) or luxated (vertical or horizontal displacement). Corneal curvature, axial length (AL), corneal diameter, central corneal thickness, anterior chamber depth, lens thickness, condition of the iris, intraocular pressure, spherical equivalent and visual acuity were also investigated. Results: EL was found in 108 eyes (62.1%). Of the 68 phakic eyes with EL, 43 (63.2%) had subluxation. Mean AL was 24.80 AE 2.57 mm, and the AL was above 23.5 mm in 65.3%. Mean keratometry (K) in phakic eyes was 41.79 AE 1.70 diopters (D), and the K value was <41.5D in 46.8%. Iris hypoplasia was found in 3.4%. Myopia above 3D occurred in 38.4% of the phakic eyes. Mean binocular logMAR was 0.10 AE 0.32. Only five patients (5.7%) had a logMAR more than 0.5. These 5 patients had EL, and 4 of them were amblyopic. Conclusion: In this strictly defined MFS group fulfilling the Ghent-1 criteria, the prevalence of EL was 62.1%. In many cases, the dislocation of the lens was subtle. On average, the corneas were flattened and the globe length was increased. Only a few patients were visually impaired. Children with MFS should have a thorough follow up to avoid amblyopia.