1. Usage of a polysaccharide fraction of tamarind gum for increasing viscosity of agents for preparing viscous ophthalmic solutions for treating dry eye syndrome, or as a carrier for ophthalmic solutions for topical administering to an eye with sustained release. 2. The usage according to claim 1, wherein said ophthalmic solutions contain from about 0,1 to 5,0% by weight of said polysaccharide fraction of tamarind gum. 3. The usage according to claim 1, wherein said ophthalmic solutions are compounds to be used for treating dry eye syndrome, contain from about 0,7 to about 1,5% by weight of said polysaccharide fraction of tamarind gum. 4. The usage according to claim 3, wherein said ophthalmic solution contains about 1% by weight of said polysaccharide fraction of tamarind gum. 5. The usage according to claim 1, wherein said ophthalmic solution is a carrier for ophthalmic solutions for topical administering to an eye with sustained release containing from about 1 to 4% by weight of polysaccharide fraction of tamarind gum. 6. The method according to claim 5, wherein said carrier is in liquid form, and contains from about 1,5 to about 2,5% by weight of said polysaccharide fraction of tamarind gum. 7. The method according to claim 5, wherein said carrier is in gel form, and contains from about 3 to about 4% by weight of said polysaccharide fraction of tamarind gum. 8. Usage of a polysaccharide fraction of tamarind gum for increasing viscosity of agents for preparing viscous ophthalmic solutions for topical administering to an eye with sustained release comprising an effective amount of one or more pharmaceutically active ingredients and said polysaccharide fraction as a system of delivery. 9. The usage according to claim 8, wherein said composition contains from about 1 to about 4% by weight of said polysaccharide fraction of tamarind gum. 10. The usage according to claim 9, wherein said one or more active ingredients are chosen from the group consisting of pilocarpine, timolol, ofloxacin and gentamicin. 11. The usage according to any of preceding claims, wherein said polysaccharide fraction of tamarind gum is obtained by purification from commercial tamarind gum. 12. The ophthalmic formulation for treating dry eye syndrome, or as a carrier for ophthalmic solutions for topical administering containing for increasing the viscosity and mucoadhesive agent a polysaccharide fraction of tamarind gum which is obtained by purification from commercial tamarind gum. 13. The ophthalmic formulation according to claim 12, comprises from about 0,1% to about 5,0% by weight of said polysaccharide fraction of tamarind gum. 14. The ophthalmic formulation according to claim 12 for usage for treating dry eye syndrome, comprises from about 0,7% to about 1,5% by weight of said polysaccharide fraction of tamarind gum. 15. The ophthalmic formulation according to claim 12 for usage as a carrier for ophthalmic solutions for topical administering with sustained release, contains from about 1 to about 4% by weight of said polysaccharide fraction of tamarind gum. 16. An ophthalmic formulation, for topical administering with sustained release, comprising an effective amount of one or more pharmaceutically active ingredients, and for increasing the viscosity of agents, polysaccharide fraction of tamarind gum which is obtained by purification from commercial tamarind gum. 17. The ophthalmic formulation according to claim 16, comprising from about 1% to about 4% by weight of polysaccharide fraction of tamarind gum. 18. The ophthalmic formulation according to claim 17, wherein said one or more ingredients are chosen from the group consisting of pilocarpine, timolol, ofloxacin and gentamicin.