Methods of contact lenses

Source: Figure is adapted by the study of (Fang, 2019)

Figure 1: chemical structures of common monomers and polymers used in Cs

        In the above given figures the monomers and polymers of the chemicals are described which are commonly used in the manufacturing of the contact lenses.  Few of the macro monomers also includes in the structures as of the contact lenses which are used as the agents of the cross liking.  All of these structures are explained with its abbreviations in the below given tables.  

Source: Adapted by the study of the (Fang, 2019)

Figure 2: Generalized properties of some common CL materials

            The above given table is explaining about the general properties of the materials of the all kinds of the contact lenses according to the particular values. All the values for the properties of the materials are (>100 barrers) and the modules of the elastic is ranging from the 0.5 to 1.5 MPa which is according to parameters arrange of the Contact lenses in above given tables.

Experiment for Silicone Hydrogels CLs

            The below given figure is explaining about the experiments of the self-assembled Silicone Hydrogels CLs. For the processes of the post-fabrication Silicone hydrogels have been commonly used. For improving the wettability of the lens the treatment of the plasma is commonly used by the manufacturers. This techniques is considered as the very effective but there can be the various issues for the Silicone hydrogels contact lenses.

Source: (Tian, et al., 2018)

Figure 3P: the adhesion of a self-assembled layer on the surface of silicone hydrogen

Results and Discussion

            The results of the all materials will be discusses in this chapter along with its experiments and this part of the research study also discusses about the various theories which are conducted on the contact lenses for their experimentation use and their draw backs in the on the human eyes. This chapter also discuss about the results of the all materials which are using for the manufacturing of the contact lenses in the markets. The proper percentage of the usage of the all of the material is also discusses in this chapter by drawing the attractive chart. Moreover the literature review summarizes in this chapter to discussing the results of the several studies of the various authors.

PMMA

            In the early 21st century the PMMA contact lenses occupying the 1% of the total market shares (Nichols, 2018). Therefore, it is considered as the useful place to perform experiment to appreciate the materials of the contact lenses. For the ocular the properties of polymers that are suitable for ocular wear. It has several other issues as; it has no permeability oxygen. It occurs because of the agility of polymer chains to prevents the flow of the oxygen as well as the internal water for immediate the flow of the oxygen. In PMMA it can occurs because of the forces of the intermolecular as physical entanglement and bonding of the dipole–dipole which is dominant among polymer chains.

Figure 4: gas-permeability and mechanisms of CL materials according to the polymer chains

Source: Adapted by the study of the (Fang, 2019)

            The above given figure is represents that how the oxygen can passes from the molecular structure of the materials of the contact lenses. The factors are not representing in the above diagram such as structure of the macro molecular and extensive cross linking.

HEMA-Derived Hydrogels

            The HEMA and linked hydrogels are known as the high water contents and commonly recognized as the oxygen-permeable polymeric material. The water content occurs in these hydrogel among the 20-80% of the co monomers along with hydrogels which are composed of the HEMA which is containing about the 38% of the water. It is defined by the high polar properties of the HEMA that these contact lenses have suitable wetting properties. Form an important part of the market the HEMA-derived hydrogels occupying about 22% (Nichols, 2018).   The water content of hydrogels can increase the NVP and MAA because of the strong hydrophilic character which is arising from hydroxyl groups, amine and carboxylic acid. The wettability of the surface can be influenced by these commoners (Seo, et al., 2017).   

Figure 5:  cross-linking effects on the modulus water-content percentage, oxygen permeability and hydro gel

Source: Adapted by the study of the (Fang, 2019)

            For improving the materials of the contact lenses it is important for the better understanding of the properties of the hydrogels. The various functions are representing by the hydrogels which is based upon the HEMA and it is commonly used by the patients (Tranoudis & Efron, 2004).

            The grafting of surfactants or incorporation included as the materials of other modifications. The surfactant contains on the components of the hydrophilic and hydrophobic. It is primarily used for promoting the reduction in the tensions of the surface among the two immiscible liquids.  It si results from the studies of the Bengani et al. (2015) implements the novel use to polymerizable surfactants whi9ch is attached to the HEMA hydrogels for enhancing the properties of the lubricates and wettability (Bengani, Scheiffele, & Chauhan, 2015). In water-contact angle round about 2.4 wt % surfactant they have achieved the reduction of the 10° that was covalently bonded with the polymerization of the UV.  The power of such techniques can be indicated by the low-surfactant loading destined by which the hydrogels of the HEMA remained below than 45%.  The components of the hydrophilic interact with tear film of the   aqueous as well as the part of the hydrophobic which remains in the hydrogel.

Source: (Bengani, Scheiffele, & Chauhan, 2015)

Figure 6: Interaction among the surfactant bonded with a hydrogel lens and aqueous tear film

            It is reported by the modern literature of the various studies that the content lenses are disconnecti8ng because of the dryness and discomfort.  The importance of the new techniques can be emphasized by this study as the techniques of the grafting and surfactant loading which is explained in the above figure. Drug delivery system for cyclosporine is includes as the other uses of surfactants by which the hydrogels of the HEMMA can be modified. The hydrogel leaked out by the surfactant along with the condensed drugs for the aggregates surfactant (Kapoor, Thomas, Tan, John, & Chauhan, 2009).

Source:  (Kapoor, Thomas, Tan, John, & Chauhan, 2009).

Figure 7: Drug-loaded hydrogel loaded with surfactants

References of contact lenses

Amirparviz, Babak, Harvey Ho and Ehsan Saeedi. "Active contact lens." (2012).

AWeissman, Barry and Bartly J. Mondino. "Risk factors for contact lens associated microbial keratitis." Contact Lens and Anterior Eye (2002): 3-9.

Bengani, L.C., G.W. Scheiffele and A. Chauhan. " Incorporation of polymerizable surfactants in hydroxyethyl methacrylate lenses for improving wettability and lubricity." Colloid Interface Sci. (2015): 60–68.

Boyd, Benjamin. Modern Ophthalmology: The Highlights. JP Medical Ltd, 2011.

Carnt, Nicole A., et al. "Contact lens–related adverse events and the silicone hydrogel lenses and daily wear care system used." Archives of ophthalmology (2009): 1616-1623.

Cope, Jennifer R., et al. "Contact lens wearer demographics and risk behaviors for contact lens-related eye infections—United States, 2014." MMWR. Morbidity and Mortality Weekly Report (2015): 865.

Douthwaite, W. A. Contact Lens Optics and Lens Design. Elsevier Health Sciences, 2006.

Efron, Nathan. Contact Lens Complications E-Book. Elsevier Health Sciences, 2018.

—. Contact Lens Practice E-Book. Elsevier Health Sciences, 2010.

Fang, Christopher Stephen Andrew Musgrave Fengzhou. "Contact Lens Materials: A Materials Science." MDPI (2019).

Gasson, Andrew and Judith A. Morris. The Contact Lens Manual E-Book: A Practical Guide to Fitting. Elsevier Health Sciences, 2010.

Hom, Milton M. and Adrian S. Bruce. Manual of Contact Lens Prescribing and Fitting. Elsevier Health Sciences, 2006.

Kapoor, Y., et al. "Surfactant-laden soft contact lenses for extendeddelivery of ophthalmic drugs." Biomaterials (2009): 867–878.

Kwok, L. Stephen, et al. "Prevention of the adverse photic effects of peripheral light-focusing using UV-blocking contact lenses." Investigative ophthalmology & visual science (2003): 1501-1507.

Lueder, Gregg T. Pediatric Practice Ophthalmology. McGraw Hill Professional, 2010.

Nichols, J. "Contact Lenses 2017. In Contact Lens Spectrum; PentaVision LLC: ." Ambler, PA, USA, (2018): pp 20–25.

Phil Lieberman, John A. Anderson. Allergic Diseases: Diagnosis and Treatment. Springer Science & Business Media, 2007.

Segre, Liz. "Contact lens basics: Types of contact lenses and more." 2017.

Seo, E., et al. " Modified hydrogelsbased on poly(2-hydroxyethyl methacrylate) (pHEMA) with higher surface wettability and mechanical properties. ." Macromol. Res. (2017): 704–711.

Sinha, Rajesh and Vijay Kumar Dada. Textbook of Contact Lenses. JP Medical Ltd, 2017.

Steinemann, Thomas L., et al. "Over-the-counter decorative contact lenses: cosmetic or medical devices? A case series." Eye & contact lens (2005): 194-200.

Tian, L., et al. "Improvement of the surface wettability of silicone hydrogel films by self- assembled hydroxypropyltrimethyl ammonium chloride chitosan mixed colloids. ." Colloids Surf. A (2018): 422–428.

Tranoudis, I. and N. Efron. "Tensile properties of soft contact lens materials. ." Contact Lens Anterior Eye (2004): 177-191.