POLYETHYLENE GLYCOL (PEG) is prized in biomedical applications for its low immunogenicity, contributing to its biocompatibility, hydrophilicity (which can aid in solubility of molecules in formulation), and resistance to protein deposition (D’Souza and Shegokar, 2016). In the ophthalmic industry, PEG has been incorporated into rewetting or lubricating drops, coatings on contact and intraocular lenses, and ocular prostheses (Benelli, 2011; Jee and Kim, 2015; Xu et al, 2016; Ko et al, 2017).

In these applications, PEG is used primarily to help with wetting the ocular surface or preventing biofouling (Benelli, 2011; Xu et al, 2016). For example, incorporation of PEG into rewetting solutions is reportedly able to improve corneal staining, tear breakup time, and patient symptoms of dry eye (Benelli, 2011).

The ability of bound PEG to improve surface hydrophilicity and decrease the deposition of proteins on a contact lens surface has been explored in the literature. In one example, researchers investigated the impact of both linear PEG and a novel tribranched PEG on the wettability of soft contact lens surfaces and the ability to resist deposition of tear proteins such as lysozyme and albumin (Jee and Kim, 2015).

The addition of any type of PEG improved measures of wettability and decreased protein deposition compared to uncoated lenses in this laboratory-based study. Tribranched PEG was able to outperform linear PEG for both of these measurements (Jee and Kim, 2015). The researchers argued that by coating lenses with this novel, 3-branch type of PEG, more of the contact lens surface is covered by the coating, presenting fewer protein-binding sites, which would result in lower deposition.

Clinically, PEG coatings are considered for improving initial and long-term patient comfort with lenses, whether by enhancing wettability of the surface or increasing deposit resistance. In one study, researchers coated large-diameter scleral lenses with PEG and observed the impact on patients who already have dry eye symptoms (Mickles et al, 2021). Comparing patients who wore uncoated lenses and those who wore coated lenses for 30 days, the latter group reported significantly improved measures of comfort and dry eye symptoms, tear breakup time, and comfortable wearing time. Additionally, eyes wearing the coated lenses had less corneal fluorescein staining, conjunctival lissamine green staining, and papillae, suggesting a promising role for these large lenses with PEG coating for wearers who have dry eye (Mickles et al, 2021).

In contrast, another study investigated the impact of PEG coatings on the initial rigid lens adaptation time of novice wearers (Debraun and Wolffsohn, 2021). This study found no difference in the reported comfort of coated and uncoated lenses during the initial 20 minutes of wear time. This suggests that the coating may not be sufficient to overcome the initial discomfort in patients who are inexperienced with wearing rigid lenses (Debraun and Wolffsohn, 2021).

The potential for the addition of PEG coating to numerous different rigid contact lens materials, presents an opportunity for practitioners to further customize and modify contact lenses. The impact of these coatings on lens wear will continue to be explored in the literature.

References

1. D’Souza AA, Shegokar R. Polyethylene glycol (PEG): a versatile polymer for pharmaceutical applications. Expert Opin Drug Deliv. 2016;13(9):1257-1275. doi: 10.1080/17425247.2016.1182485

2. Benelli U. Systane lubricant eye drops in the management of ocular dryness. Clin Ophthalmol. 2011;5:783-790. doi: 10.2147/OPTH.S13773

3. Jee JP, Kim HK. Development of hydrogel lenses with surface-immobilized peg layers to reduce protein adsorption. Bull Korean Chem Soc. 2015;36(11):2682-2687. doi.org/10.1002/bkcs.10545

4. Xu X, Tang JM, Han YM, Wang W, Chen H, Lin QK. Surface PEGylation of intraocular lens for PCO prevention: an in vivo evaluation. J Biomater Appl. 2016;31(1):68-76. doi: 10.1177/0885328216638547

5. Ko J, Cho K, Han SW, et al. Hydrophilic surface modification of poly(methyl methacrylate)-based ocular prostheses using poly(ethylene glycol) grafting. Colloids Surf B Biointerfaces. 2017;158:287-294. doi: 10.1016/j.colsurfb.2017.07.017

6. Mickles CV, Harthan JS, Barnett M. Assessment of a novel lens surface treatment for scleral lens wearers with dry eye. Eye Contact Lens. 2021;47(5):308-313. doi: 10.1097/ICL.0000000000000754

7. Debarun D, Wolffsohn JS. Effect of large diameter and plasma coating on the initial adaptation of gas permeable contact lens fitting for neophytes. Cont Lens Anterior Eye. 2021;44(1):76-80. doi: 10.1016/j.clae.2020.08.009