DESCRIPTION FIELD OF THE INVENTION The present invention is related to a pharmaceutical formulation in ophthalmic nano-solution form in aqueous base. BACKGROUND OF THE INVENTION Eye is one of the important organs of the body. Eye is also a complex organ with unique anatomy and also renders a physiology different from other organs. Various parts of eyes are deprived of blood vessels thus systematic drugs failed to impart their effect on those organs virtually providing ophthalmic route the only possibility. Thus, in various cases the only route of drug administration in eyes is topical delivery and thus is a well accepted route of administration. The topical drug delivery system in ocular use comprises the delivery of the drug in the precorneal region and the region beyond the cornea. The conditions such as glaucoma, allergic conjunctivitis, anterior uveitis and cataract can be managed through this non-invasive route of administration. Since eye is anrimportant organ and is also an exposed part of the body, thus it has various protective barriers which protect the eyes from external danger. Due to these external barriers, there is a poor bioavailability of ocular drugs. Due to the corneal layer, the bioavailability of the topically administered drug is very less in the anterior segment of the eye. Numerous anatomical and physiological constraints such as tear turnover, naso-fachrymal drainage, reflex blinking, and ocular static and dynamic barriers pose a challenge and impede deeper ocular drug permeation. Although ocular disorders are treated mainly with the help of eye drops but due to the fundamental challenge in the bioavailability and accommodation of very low volume of eye drop in the eye, the topical ophthalmic route seems to be an inefficient method for drug administration. Various attempts have been 5 made to improve the bioavailability of the formulation through ocular route such as increasing the viscosity, reducing the nasolacrimal drainage or improving corneal penetration. The pharmaceuticalnano-solution is defined as the formulation comprising the nano particles of difluprednate solubilized in a novel solvent system for 10 topical and/or ocular administration. The advantages of the nano particles is more absorption, enhanced bioavailability and increased therapeutic efficacy. The particle size of the difluprednate should be not more than 400 nanometers. According to a preferred embodiment, the particle size should be in between 200nm to 400nm. 15 Ophthalmic drug delivery system is one of the most challenging delivery system for formulation development due to the unique anatomy and physiology of the eye which makes it almost impervious to foreign substances. There is even more challenge in the formulation if the drug has less solubility in water i.e. hydrophobic drugs. Thus, there is a need of the 20 formulation comprising a hydrophobic drug in nano form which is solubilized in the solvent system and enhances the efficacy. The solvent system used mainly comprises water. Thus nanosolutions for ocular delivery can be a potent dosage form with enhanced penetration, increased bioavailability and better efficacy. > ' 25 Difluprednate (6a, 9a-difluoroprednisolone 17-butyrate 21-acetate) is an antiinflammatory steroid which is known to show superior anti-inflammatory action by percutaneous administration (U.S. Pat. Nos. 3,780,177, 3,784,692). 3 r c n n e t U T - n c - T > - O D I ? t T - ? c i t ^ E ^ PTiafl,. i ff.ij- run.. Jin- t ' F . -A- S—B—•>* - i r n T ~W7~t ^ *"? •tSw-s*—if rri.--!!i_. tun r. n. -rv ,-w.^—J «c_&« *im % ,r -a. ,r -Si-_£ L—a&—==£_ ,,. , , formulate an ocular formulation and moreover a novel approach towards formulation of an ocular delivers system. The primary challenge in developing an ocular formulation is the choice of suitable excipients which are to be used. Although there are various excipients available but due to extra 5 sensitivity of the ocular surface, non-irritating substances are to be used which is a primary requirement and unfortunately there are very less options available. Various formulations are available but the problems associated with it are irritation, stability challenges, high viscosity causing blurred vision and product content uniformity. These factors cause a barrier in proper 10 administration of drug through ocular route: The present invention is related to an ophthalmic drug delivery system comprising difluprednate in nanonized particle wherein the formulation is aqueous solution so as to negate the side effects of the conventional ophthalmic formulation. The nanoparticle does not cause irritation on the 15 ocular surface, improves bioavailability and enhances the efficacy of the drug. Furthermore, the formulation also optionally comprises penetration enhancers which also help in the penetration of the drug. The solubilizers used in the present formulation increases the stability of the formulation. One or more solubilizers used in the formulation may be 20 selected, but not limited to, povidone (polyvinylpyrrolidone), polyvinyl alcohol, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, carboxyvinyl polymer, and salts thereof and the like. The surfactants are the agents that reduce the surface tension between two 25 phases and allow better solubility of the ingredients. Surfactants also provide . . easier spreading of the formulation oh ocular surface. The surfactants used in the present invention may be selected from Polysorbate 80, Polysorbate 20, T o- f% ner u\ -T, O. r - 1 ? - ? B i 7 ' 1 7'~: I 5 -HJn^-ft" "*'»l- (li,.^.I.....-rt-.-H--r—^SEM eaJ£—«•»•• ,ft if.n ffim %^* rfir—£ .—r«fln_.fi out —£_ Cetylpyridinium chloride, Tyloxapol, propylene glycol, and polyvinyl alcohol; or the combinations thereof. Tha term "penetration enhancers" and "permeation enhancers" are synonymous and can be used interchangeably. Penetration enhancers are 5 used in the present invention to improve the penetration of drug through the cornea and for improving bioavailability. The penetration enhancer used in the formulation may be selected from surfactants, including detergents and nonionic surfactants. Examples include laurocapram, hexartiethylene lauramide, hexamethylene octanamide, and decylmethyl sulfoxide. 10 The other pharmaceutical excipients in the present invention may be selected, but not limited to, from osmotic gradient modifiers, buffer system, preservatives, antioxidants, viscosity modifiers, formulation stability enhancers, and chelating agent. The osmotic gradients modifiers are used to maintain the tonicity of the 15 formulation and thus no irritation by the formulation when administered in the eyes. The osmotic gradient modifiers used in the present invention can be selected, but not limited to, from sorbitol, mannitol, dextrose and sodium chloride. Buffer system is used to maintain the pH of the formulation close to the ^ 20 chosen value for better patient compliance. The butter system can be a. selected, but not limited to, from borate, citrate, phosphate or acetate. ' The preservative are used to inhibit the growth of microorganisms and make the formulation more stable and safe for use. The preservatives used in the present formulations can be selected, but not limited to, from benzalkonium 25 chloride (BAK), sorbic acid, chlorobutanol, disodium, ethylenediamine tetra- _2 E O LL CO ^- o TO t "? 1 T • wfer.-f — o CD Q in o 7. 8. 9. Tyloxapol Benzalkonium Chloride Water for injection - - - • Kg Kg Kg 1.000 0.020 q.s100Ltr. Procedure:- a) Non-Aqueous Phase:- Take 2.00 Kg of N-methyl 2-pyrrolidone and add 0.0525 kg of Difluprednate (Micronized and Sterile). Stir to get clear solution. b). Aqueous Phase:- Take 75.00 Ltr. of Water for Injection cooled up to 30°C in a SS jacketed tank and add 3.000 kg of Polysorbate 80 stir to get clear solution. •- c). Add 1.000 Kg of Cetalkonium Chloride stir with heating up to 40°C in step (b). d). Add 1.000 Kg of Tyloxapol to above step (b) stir to get clear solution. e). Add 0.050 Kg of disodium EDTA to step (b) stir to get dissolve. f). Add 0.050 kg of Ascorbic acid stir to get clear solution in step (b). g). Mixing of Aqueous and Non-Aqueous phase:- Add Non aqueous phase in to the aqueous phase slowly (drop wise) with continuous stirring at high speed and stir the emulsion for one hour. h). Now add Benzalkonium Chloride in the above solution with continuous stirring. i). Make up the final volume up to 100Ltr. with cooled Water for injection. j) , Check the final pH which should be in between 4.00 to 6.00. CLAIMS We claim: 1) An ophthalmic pharmaceutical formulation comprising an active .pharmaceutical ingredient in with nano-particle system along with pharmaceutical excipients. 2) Pharmaceutical formulation as claimed in claim 1 is a nano-emulsion with an aqueous base. 3) The pharmaceutical formulation, claimed in claim 1, have the particle size less than 400 nm, preferably 200-400 nm. 4) The active pharmaceutical ingredient claimed in claim 1 can be selected from difluprednate, nepafenac, loteprednol, and rebamipide 5) The. active pharmaceutical ingredient as claimed in claim 1 may preferably be difluprednate. 6) The pharmaceutical excipient as claimed in claim 1 can be selected from solvent, chelating agents, pH regulators, surfactants, preservatives, penetration enhancers, osmotic gradient modifiers and vehicle or the combinations thereof. 7) The excipients as claimed in claim 6 can be a combination of solvent, chelating agents, pH regulators, surfactants, preservatives, and vehicle.