A polymer produced by polymerizing a polymerizable composition including a hydrophilic monomer and a crosslinkable monomer. The A×B value that is the product of the molar fraction A of the hydrophilic monomer and the molar fraction B of the crosslinkable monomer is more than 2.1×10−3 and less than 3.6×10−3. The molar fraction B of the crosslinkable monomer is less than 2.4×10−2. The polymer has a refractive index n of 1.5 or more in a state of hydration.
