in a preferred embodiment , the compositions of the present invention are administered topically . the dosage range is 0 . 001 to 5 . 0 mg / per eye . dosage for one eye is understood to be about one drop of solution . one drop of solution may be between 10 μl to 200 μl , between 20 μl and 120 μl , or between about 50 μl to about 80 μl of solution or any values in between . for example , dispensers such as pipettors can dispense fluid drops from at least 1 μl to 300 μl and any value in between . in a preferred embodiment , the solution may be administered as an eye drop using any of the many types of eye drop dispensers on the market . although not required , the container for the compositions of the invention may be clear , translucent , and opaque and may contain other properties or combination of properties such as being glass lined , tamper proof , packaged in single or few dose aliquots , and a combination thereof . suitable topical anesthetics for the compositions and methods of the invention include , at least , proparacaine , lidocaine , tetracaine or a derivative or combination thereof . the compositions of the present invention can be administered as solutions , suspensions , emulsions ( dispersions ), gels , creams , or ointments in a suitable ophthalmic vehicle . in any of the compositions of this disclosure for topical administration , such as topical administration to the eye , the mixtures are preferably formulated as 0 . 01 to 2 . 0 percent by weight solutions in water at a ph of 4 . 0 to 7 . 0 . as an optional ingredient , a suitable antimicrobial preservative may be added to prevent multi - dose package contamination . such agents may include benzalkonium chloride , thimerosal , chlorobutanol , methyl paraben , propyl paraben , phenylethyl alcohol , edta , sorbic acid , onamer m , other agents known to those skilled in the art , or a combination thereof . typically such preservatives are employed at a level of from 0 . 001 % to 1 . 0 % by weight . the compositions of the invention may contain one or more optional surfactants ( or co - solvents ). the solubility of the components of the present compositions may be enhanced by a surfactant or other appropriate co - solvent in the composition . examples of such co - solvents / surfactants include polysorbate 20 , 60 , and 80 , polyoxyethylene / polyoxypropylene surfactants ( e . g . pluronic f - 68 , f - 84 and p - 103 ), cyclodextrin , tyloxapol , other agents known to those skilled in the art , or a combination thereof . typically such co - solvents / surfactants are employed at a level of from 0 . 01 % to 2 % by weight . the compositions of the invention may contain an optional viscosity - enhancing agent — that is , an agent that can increase viscosity . viscosity increased above that of simple aqueous solutions may be desirable to increase ocular absorption of the active compound , to decrease variability in dispensing the formulation , to decrease physical separation of components of a suspension or emulsion of the formulation and / or to otherwise improve the ophthalmic formulation . examples of such viscosity - enhancing agents include polyvinyl alcohol , polyvinyl pyrrolidone , methyl cellulose , hydroxy propyl methylcellulose , hydroxyethyl cellulose , carboxymethyl cellulose , hydroxy propyl cellulose , other agents known to those skilled in the art , or combinations thereof . such agents are typically employed at a level of from 0 . 01 % to 2 % by weight . the following two reactions must be considered for the chemistry of pvp - i in aqueous solutions : the invention has been described herein by reference to certain preferred embodiments . however , as obvious variations thereon will become apparent to those skilled in the art , the invention is not to be considered as limited thereto . all patents , patent applications , and references cited herein are incorporated by reference in their entireties . step 1 : povidone iodine and sodium alginate were fully dissolved in water with adjustment of ph to 4 . 0 ˜ 5 . 0 to make solution a . microspheres encapsulating povidone iodine were formed when spraying solution a into a calcium chloride solution . the microspheres were then filtered and dried . the calcium chloride solution concentration was preferred to be 1 %˜ 5 %. step 2 : povidone iodine , a metal ion chelating agent , a ph adjusting agent , microspheres stabilizer , and a suspending agent were poured into proper amount of water and mixed , adjusting ph to 4 . 0 ˜ 5 . 0 , to make solution b , which was filled into the eye drop bottle . step 3 : microspheres encapsulating povidone iodine and alginate was poured into solution b to make a povidone iodine slow - releasing ophthalmic composition . preparation of 7 formulations of microspheres ( listed above in table 1 ) was conducted according to the method described in example 1 . in formulation 7 , the concentration of sodium alginate was too high to dissolve , which resulted in no microspheres being formed . artificial tear configuration : 0 . 24 g anhydrous calcium chloride and 27 . 4 g sodium chloride were added into 4000 ml pure water , and the ph of the resultant solution was adjusted using naoh to 6 . 8 ˜ 7 . 2 , for back - up . dissolution method : 0 . 5 g microsphere was added into 100 ml artificial tears and time was recorded . write down the situation and period of time about the change in color of the microsphere — from brown to white . table 2 below shows the result of the microsphere dissolution study : table 2 shows that microspheres of formulations 1 - 5 can release for a long time , formulation 6 was not suitable for slow - release microsphere . so , the ratio of povidone iodine and sodium alginate is preferred to be 1 : 1 ˜ 1 : 5 . at day 0 , 5 and 10 , 2 bottles of pvp - i eye drops were taken out and filtered through microfiltration membrane to filter microspheres . a 3 % cacl 2 solution was used to rinse the microspheres twice , which were then allowed to dry . the microspheres &# 39 ; corrosion was studied . table 4 shows accelerated testing results : miscrospheres made in example 1 were used for this study . specifically , 0 . 5 g microspheres were added to 200 ml solutions of different concentrations of hcl and naoh , and the ph of the resultant mixture was adjusted to 2 . 0 , 5 . 0 , 7 . 0 , and 9 . 0 , respectively . the test shows that in the solution of ph 2 . 0 ˜ 5 . 0 , the microspheres maintained their round and smooth shape ( indicating no or little corrosion ); in the solution of ph 7 . 0 ˜ 9 . 0 , the microspheres corrosion happed quickly to completion . therefore , the preferred ph for a microsphere solution is 2 . 0 ˜ 5 . 0 . considering the acid sensitivity of the eye , the preferred ph is 4 . 0 ˜ 5 . 0 . microspheres were prepared by the following process : first , 1 . 5 g of sodium alginate was completely dissolved in 80 grams of water , and to the resultant solution was then added 0 . 5 g povidone - iodine . the mixture was stirred until pvp - i completely dissolved . the ph of the solution was then adjusted to 4 ˜ 5 and to the solution was filled up to 100 grams by addition of the remaining water . the final solution was allowed to stand by for the next use . preparation of 3 % solution of calcium chloride : 6 g anhydrous calcium chloride was dissolved in 200 g purified water , stirred sufficiently , for backup . filling the sodium alginate / pvp - i solution prepared above in a spray device , and uniformly sprayed to the just - prepared cacl 2 solution . pvp - i microspheres were formed on the surface of cacl 2 solution . the microspheres were allowed to sit in the cacl 2 solution for an hour , making it completely calcified , forming microspheres of a size of about 200 nm ˜ 10 μm by membrane filtration . the microspheres was rinsed with a 3 % calcium chloride solution and then allowed to dry . hydroxyethylcellulose ( 0 . 5 g ) was added to 50 g water and was homogenized . to the solution was poured 2 g of glycerol and 0 . 01 g of edta - na , and the resultant mixture was mixed until homogeneous . 1 g of povidone iodine , 0 . 1 g of cacl 2 , and 0 . 9 g of nacl were added into 40 g water , stirred vigorously until completely dissolved . this solution was then poured into the just - made above hydroxyethylcellulose solution and the resultant mixture was homogenized . the ph of the solution was adjusted to 4 ˜ 5 . povidone iodine microspheres were added to this solution and then water was added to reach the total water weight of 100 g . the final solution was packed separately into 10 g per bottle . microspheres were prepared according to the method in example 1 with the following materials : 1 g of sodium alginate , 0 . 5 g of povidone iodine , and 100 g of water ( total weight ). an ophthalmic solution was prepared according to example 6 with the following materials : 5 g of povidone iodine microspheres , 0 . 9 g of nacl , 0 . 2 g of cacl 2 , 0 . 1 g of povidone iodine , 2 g of glycerol , 0 . 01 g of edta - na , 1 . 2 g of hydroxyethylcellulose ; and total water weight of 100 g . microspheres were prepared according to the method in example 1 with the following materials : 0 . 5 g of sodium alginate , 0 . 5 g of povidone iodine , and 100 g of water ( total weight ). an ophthalmic solution was prepared according to example 6 with the following materials : 15 g of povidone iodine microspheres , 0 . 9 g of nacl , 0 . 4 g of cacl 2 , 0 . 8 g of povidone iodine , 2 g of glycerol , 0 . 01 g of edta - na , 1 . 0 g of hydroxyethylcellulose ; and total water weight of 100 g . microspheres were prepared according to the method in example 1 with the following materials : 2 . 0 g of sodium alginate , 0 . 5 g of povidone iodine , and 100 g of water ( total weight ). an ophthalmic solution was prepared according to example 6 with the following materials : 20 g of povidone iodine microspheres , 0 . 9 g of nacl , 0 . 5 g of cacl 2 , 1 . 0 g of povidone iodine , 2 g of glycerol , 0 . 01 g of edta - na , 2 . 0 g of hydroxyethylcellulose ; and total water weight of 100 g . microspheres were prepared according to the method in example 1 with the following materials : 0 . 5 g of sodium alginate , 0 . 5 g of povidone iodine , and 100 g of water ( total weight ). an ophthalmic solution was prepared according to example 6 with the following materials : 25 g of povidone iodine microspheres , 0 . 9 g of nacl , 0 . 5 g of cacl 2 , 0 . 8 g of povidone iodine , 2 g of glycerol , 0 . 01 g of edta - na , 1 . 0 g of hydroxyethylcellulose ; and total water weight of 100 g . the compositions of this invention show unexpected stability compared to the pvp - i solutions in which pvp - i does not exist in microspheres . specifically , the composition can retain at least 90 % of its polyvinylpyrrolidinone - iodine after a period of 1 month even in an environment with light . this indicates that the eye drop solutions ( or compositions ) of this invention can have long shelf - lives ( e . g ., at least 3 months , 6 months , 9 months , or a year ), even in the light environment , before their application for the treatment or prophyaxis of an eye disorder .
the present invention provides novel slow - releasing ophthalmic compositions containing povidone iodine and uses thereof in the treatment of acute infections of at least one eye tissue from bacterial , mycobacterial , viral , fungal , or amoebic causes and for preventing such infections in appropriate clinical settings . each of the ophthalmic compositions contains povidone iodine , osmotic pressure regulator , suspending agent and edta - na , wherein povidone iodine exists as microsphere particles formed by pvp - i and sodium alginate .