CONTROLLED APPLICATION OF CROSS-LINKING AGENT

1 . A kit for transepithelial delivery of a cross-linking agent to a cornea, comprising:

a first vessel containing an initial formulation that includes a cross-linking agent and a first active ingredient configured to open corneal epithelial tight junctions when applied to a cornea; and

one or more second vessels each containing a respective secondary formulation that includes the cross-linking agent for application to the cornea after the initial formulation is applied to the cornea.

2 . The kit of claim 1 , wherein the first vessel and the one or more second vessels are syringes.

3 . The kit of claim 1 , further comprising another vessel containing a final formulation that includes the cross-linking agent and a second active ingredient configured to close the corneal epithelial tight junctions when applied to the cornea after the initial formulation and the one or more secondary formulations have been applied to the cornea.

4 . The kit of claim 3 , wherein the second active ingredient is sodium bicarbonate.

5 . The kit of claim 1 , wherein the one or more active formulations omit the first active ingredient.

6 . The kit of claim 1 , wherein the first secondary ingredient is benzalkonium chloride (BAC).

7 . The kit of claim 1 , further comprising another vessel containing a reverse osmotic substance.

8 . The kit of claim 7 , wherein the reverse osmotic substance is a gel, a hydrogel, or a semisolid substance.

9 . The kit of claim 7 , wherein the reverse osmotic substance is a liquid.

10 . The kit of claim 9 , wherein the reverse osmotic substance includes distilled water.

11 . The kit of claim 1 , further comprising another vessel containing a quenching substance.

12 . The kit of claim 11 , wherein the quenching substance includes ascorbic acid, phenolic compounds, or metal ions.

13 . The kit of claim 1 , wherein the cross-linking agent is Riboflavin.

14 . The kit of claim 1 , wherein the cross-linking agent includes a plurality of potential cross-linking agents, the secondary formulation contained in at least two of the one or more second vessels including a different one of the plurality of potential cross-linking agents.

15 . A method of treating an eye, comprising:

applying an initial formulation including a cross-linking agent and a first active ingredient to a cornea to simultaneously open corneal epithelial tight junctions of the cornea and diffuse the cross-linking agent into the cornea;

after applying the initial formulation, applying one or more secondary formulations including the cross-linking agent to the cornea to further diffuse the cross-linking agent into the cornea via the open corneal epithelial tight junctions, the application of the initial formulation and the one or more secondary formulations determining a concentration profile of the cross-linking agent in the cornea; and

activating the cross-linking agent to initiate cross-linking in the cornea according to the concentration profile.

16 . The method of claim 15 , wherein the first active ingredient is benzalkonium chloride (BAC).

17 . The method of claim 15 , further comprising, after the applying the one or more secondary formulations, applying a final formulation including the cross-linking agent and a second active ingredient to the cornea to close the corneal epithelial tight junctions of the cornea, the concentration profile being determined by the application of the initial formulation, the one or more intermediate formulations, and the final formulation.

18 . The method of claim 17 , wherein the second active ingredient is sodium bicarbonate.

19 . The method of claim 15 , wherein the one or more secondary formulations omit the first active ingredient.

20 . The method of claim 15 , further comprising applying a reverse osmotic substance to the cornea to draw the cross-linking agent from the cornea.

21 . The method of claim 20 , wherein the reverse osmotic substance is a gel, a hydrogel, or a semisolid substance.

22 . The method of claim 20 , wherein the reverse osmotic substance is a liquid.

23 . The method of claim 22 , wherein the reverse osmotic substance includes distilled water.

24 . The method of claim 15 , further comprising:

after applying the initial formulation, waiting a first amount of time to allow the initial formulation to diffuse into the cornea;

after waiting the first amount of time, rinsing the cornea;

after each application of the one or more secondary formulations, waiting a respective second amount of time to allow each of the one or more secondary formulations to diffuse into the cornea, the concentration profile being a predetermined concentration profile, the first amount of time and each second amount of time being selected to achieve the predetermined concentration profile; and

rinsing the cornea after waiting each second amount of time.

25 . The method of claim 15 , wherein the activating the cross-linking includes applying ultraviolet light to the cornea.

26 . The method of claim 15 , wherein the cross-linking agent includes a plurality of potential cross-linking agents, at least two of the one or more secondary formulations including a different one of the plurality of potential cross-linking agents.

27 . The method of claim 15 , wherein the cross-linking agent includes Riboflavin.

28 . The method of claim 15 , wherein the cross-linking agent is activated after all of the one or more secondary formulations are applied.

29 . The method of claim 28 , wherein the cross-linking agent is also activated before all of the one or more secondary formulations are applied.

30 . The method of claim 15 , further comprising applying a quenching substance to the cornea to minimize photoactivation and unwanted cross-linking.

31 . The method of claim 30 , wherein the quenching substances includes ascorbic acid, phenolic compounds, or metal ions.