Provided is a gel material for ophthalmic treatment useful as a synthetic vitreous body which is a novel intraocular tamponade material having a low swelling pressure, an appropriate elastic force, and no toxicity to ocular tissues, specifically, to retinas, and which is capable of stably maintaining a long-term stable tamponade effect.A gel material for ophthalmic treatment including a hydrogel in which a gel precursor cluster crosslinks to form a three-dimensional network. The gel precursor cluster has a structure with crosslinked monomer units or crosslinked polymer units present at concentrations less than a critical gelation concentration, and the gel precursor cluster has a relationship of G' <； G" where G' represents a storage elastic modulus and G" represents a loss elastic modulus. The hydrogel has a polymer content of 50 g/L or less, a storage elastic modulus G' of 1 to 10,000 Pa at a frequency of 1 Hz, and a fractal dimension of 1.5 to 2.5.
