Design

Proposed Solution

To prevent the secondary surgery due to Lens loosening or lens rotation [1], micro-haptics hooks are created that change shape depending on pH concentration. First, the IOLs are packaged in a 3.0 pH solution causing the micro-haptics to be straight. Second when introduced into the 6.80-7.46 pH of the aqueous humor, the straight micro-haptics curve. The curving of the micro-haptics lock onto suspensory ligaments.

pH-Click Schematic

The Intraocular Lens is suspended in pH 3.0 packaging. Then implanted into the patient and correctly aligned. The 7.0 pH of the aqueous humor changes the pH-Click shape of the micro-haptic to lock the IOLs to the suspensory ligament.

Suspensory ligament also known as Ciliary zonule

http://medical-dictionary.thefreedictionary.com/ciliary+zonule

Lens Material

The intraocular lens is made up of hydrophilic acrylics [2]

http://www.european-coatings.com/Raw-materials-technologies/Raw-materials/Coatings-binders/Dissolving-bonds

Synthesis of micro-haptics Material

The intraocular lens micro-haptics are made of poly(methacrylic acid) [3]

Calculating cross-link density: Flory–Huggins equation [4]

Formula 1: Swollen Hydrogel

Formula 2: Swollen Hydrogel re-written for only one swelling direction.

ø2 = the volume fraction of polymer in the swollen mass
V 1 = the molar volume of the solvent
V(hat) = the specific volume of the polymer
n = the number of network chain segments bounded on both ends by cross-links,
χ 1 = the Flory solvent-polymer interaction term.
Mc = the average molecular weight between cross-linking
M = the molecular weight of the polymer before cross-linking

Cross-link density can be calculated using Flory-Huggins equation. Flory-Huggins variable from PMAA at in water is 0.598 found via experimentation.

ø2 = 0.06
V 1 = 18.1 cm3/mol
V(hat) = 0.985 cm3/g
n = the number of network chain segments bounded on both ends by cross-links,
χ 1 = 0.598
Mc = the average molecular weight between cross-linking
M = 116,250 Da

The formula returns the average molecular weight between cross-linking. Leaving Mc = 27 monomers between the cross-link

Results

With an overall increase of the number of micro-haptics the adherence force will lead to a tighter fit. This tighter fit, will prevent slippage when the ligaments weaken over time. The current flaw of rotation will be eliminated by the perpendicular attachment. Lastly, because of the tight fixation, when the eye focus's using ciliary muscles the material of the IOL will change shape leading to a more natural focal vision.

Reference

[1] Mamalis, Nick. "Intraocular Lens Dislocation." Journal of Cataract & Refractive Surgery 39.7 (2013): 973-74. Web.

[2] Werner, Liliana. "Biocompatibility of Intraocular Lens Materials." Current Opinion in Ophthalmology 19.1 (2008): 41-49. Web.

[3] Kozlovskaya, Veronika, Yun Wang, William Higgins, Jun Chen, Yi Chen, and Eugenia Kharlampieva. "PH-triggered Shape Response of Cubical Ultrathin Hydrogel Capsules." Soft Matter 8.38 (2012): 9828. Web.

[4] Flory, Paul; Rehner, John (1943). "Statistical mechanics of cross-linked polymer networks II. Swelling". J. Chem. Phys. 11: 521–526. Bibcode:1943JChPh..11..521F. doi:10.1063/1.1723792