Characterising the Inflammatory Response of the Ocular Surface and Adnexa to Contact Lens Wear

UoM administered thesis: Phd

  • Authors:
  • Noor Haziq Bin Saliman

Abstract

There is growing evidence suggesting that soft contact lens wear stimulates a low-grade ocular inflammatory response but the underlying mechanisms involved are not well understood. This thesis investigated the impact of different types of soft contact lens materials, wearing modalities and care systems on the subclinical inflammatory response of the ocular surface. A pilot investigation (Chapter 3) was carried out on 20 subjects (10 soft lens wearers and 10 non-wearers) to investigate the utility of three clinical techniques (with associated image analysis and laboratory investigations) in the identification of a subclinical inflammatory response. The three techniques were in vivo confocal microscopy (IVCM) which examined presumed dendritic cells (DC) and hyperreflective white spots (WS), tear film analysis which investigated the presence of IL-6, IL-8, IL12p70 and TNF cytokines and impression cytology which investigated the presence of CD45+ cells. All three techniques were found to produce promising data for the use of these three assessments. The results of the pilot investigation suggested that the inflammatory response was greater in contact lens wearers compared to non-wearers. Additionally, the repeatability of IVCM examination was found to be ‘good’ or ‘excellent’ when carried out by the same investigator on two separate occasions. Clinical Investigation 1 (Chapter 4) used the same investigative techniques as in the Pilot Investigation with an additional nine cytokines for tear film analysis. This study compared the inflammatory response in two different lens materials [a conventional hydrogel (CH) versus a silicone hydrogel (SiH)] and two different wearing modalities in the same lens (reusable versus daily disposable of SiH lenses) and its association with comfort. All three lens/modality options were worn by all subjects (20 soft lens wearers) in random sequence for one week with a one week washout period between each lens type. The lenses were worn in one eye only (the fellow eye acted as control) on a daily wear basis, and hydrogen peroxide (H2O2) was used as a care system for both reusable lenses. Overall, reusable CH and SiH lenses showed higher inflammatory responses for all parameters measured compared to the SiH daily disposable lenses. No statistical difference was noted between the CH and SiH materials when used in a reusable modality; however, based on the 95% confidence interval range, several parameters were increased after one week of lens wear compared to baseline. No association was noted between any of the parameters measured and comfort score. Clinical Investigation 2 (Chapter 5) studied the impact of care systems [H2O2 and multipurpose solution (MPS)] when used with CH and SiH reusable lenses. Fifteen of the 20 subjects who had participated in Clinical Investigation 1 were recruited and wore the CH and SiH lenses bilaterally each for a one week period and additionally wore no lenses for one week (control), all in random sequence with a one week of washout between each lens/no lens wear period. Hydrogen peroxide and MPS were used with right and left lenses, respectively. All subjects underwent a similar protocol of IVCM and impression cytology as in Clinical Investigation 1 after one week of lens/no lens wear. Two additional markers were tested (CD3 and CD11c) for all impression cytology samples alongside the CD45 antibody marker. The SiH+MPS and CH+MPS combinations showed the highest and the lowest levels of inflammation for all parameters measured, respectively. No appreciable difference was noted between CH and SiH when conditioned with H2O2 solution, consistent with Clinical Investigation 1 findings. Furthermore, no association was observed between any of the parameters measured and comfort score. In conclusion, the relative subclinical inflammatory impact of various soft contact lens materials, modalities and solution types broadly reflects the relative incidence of CIE reported in the literature and the methods employed here may provide a useful short term predictor of infiltrative events seen with different lenses and solutions. To minimise ocular surface inflammation, this body of work suggests that daily disposables lenses should be the first choice lens. For reusable lenses, CH lenses should be used with MPS, and SiH lenses should be used with H2O2, at least for the products (lenses and care solutions) used in this thesis.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date1 Aug 2019