METHODS: The Bovine Corneal Opacity and Permeability test method (BCOP), OECD Test Guideline 437, was used as an initial step to study the inducing effect of palm-based MES on irreversible eye damage. The second assessment involved the use of reconstructed human corneal-like epithelium test method, OECD Test Guideline 492 using SkinEthic™ Human Corneal Epithelium to study the potential effect of palm-based MES on eye irritancy. The palm-based MES were prepared in 10% solution (w/v) in deionized water and tested as a liquid and surfactant test substances whereby both test conducted according to the liquid/surfactant treatment protocol.

RESULTS: The preliminary BCOP results showed that palm-based MES; C12, C14, C16, C16:18 were not classified as severe eye irritants test substances with in vitro irritancy score between 3 and the threshold level of 55. The second evaluation using SkinEthic™ HCE model showed that palm-based MES; C12, C14, C16, C16:18 and three commercial samples were potentially irritants to the eyes with mean tissue viability ≤ 60% and classified as Category 2 according to United Nations Globally Harmonized System of Classification and Labelling of Chemicals. However, there are some limitations of the proposed ocular irritation classification of palm-based MES due to insolubility of long chain MES in 10% solution (w/v) in deionized water.

MATERIALS AND METHODS: ARPE-19 cells were pre-treated with LUT, ZEA, or both for 24 h before 200 μM H2O2 challenge. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. DICER1 and Alu RNA were quantified by western blotting and real-time polymerase chain reaction, respectively.

RESULTS: H2O2 increased cell Alu RNA expression and decreased cell viability of ARPE-19, but had no significant impact on the DICER1 protein level. LUT, alone and in combination with ZEA pre-treatment, prior to H2O2 challenge significantly improved cell viability of ARPE-19 and reduced the level of Alu RNA compared to the negative control.

MATERIAL AND METHOD: 25 healthy electronic cigarette smokers and 25 age- and gender-matched healthy non-smokers were included in the study. RNFL, GCL, IPL and choroidal thickness were measured by SD-OCT using an automated programme. After normality tests, an independent sample t-test was used to analyse the differences in RNFL, GCL, IPL, and choroidal thickness values between the groups.

RESULTS: The mean age of electronic cigarette smokers and non-smokers was 33.68 and 33.64 years, respectively. The mean smoking history was 6.6 years (range 5-8 years). Most of the participants smoked 2-5 ml of e-liquid per day (52%), while 36% smoked more than 5 ml and 12% smoked less than 2 ml per day. The mean intraocular pressure in the electronic cigarette smoker group was 15.0 mmHg, while the non-smoker group was 15.32 mmHg. The mean axial length in the electronic cigarette smoker group and non-smoker group was 23.36 and 23.63 mm, respectively. No significant difference was observed regarding RNFL, GCL, IPL or choroidal thickness between both groups.