Letter for the article Evaluation of Tear Film Osmolarity Among Diabet


Mr. editor

I read with interest the article by Abusharha et al.1 I would like to suggest adding two critical comments to their main conclusion. Since the authors observed that tear osmolarity is not significantly different in their small sample of enrolled diabetic participants, they suggest that “the result may be explained by a lack of relationship between tear film parameters and severity of diabetes; tear film parameters may be more correlated with duration of diabetes rather than severity ”. While their interpretations may be partly true, these discussions are subject to two major biases.

First, they did not provide a table to describe the characteristics of the participants, and the date the study was performed is not indicated in the document. However, calculated, the average age of diabetic patients in their study is significantly higher than that of their control group (P

Second, if one assumes that their study was conducted during the COVID-19 pandemic, then a game-changing bias was not factored into their study design. Mandatory wearing of a face mask during COVID-19 negatively affects – directly or indirectly – the ocular surface and dry eye, and results in the creation of a dry eye or worsening of pre-existing dry eye.2 Both basal tear production3 and tearing reflex4 are closely associated with tear osmolarity bilaterally. Since there are drastic differences between individuals in terms of wearing a face mask,5 the severity and / or degree of face mask-induced dry eye would be expected to be different in non-randomly enrolled participants.

With this in mind, it is possible that the lack of relationship between tear film parameters and the severity of diabetes, and a pronounced association with duration of diabetes is likely due to (i) the significantly higher mean age of patients. diabetics than controls, not necessarily the duration of diabetes per se, and (ii) unmeasured / unadjusted tear secretion in their study design. These imply that their conclusion could be either an artefact or a real observation; or, the association in some patients may be more pronounced, while in some patients the associations may be weakened.

These comments apply not only to the article by Abusharha et al,1 but more generally to “all” studies on dry eye in diabetic patients since the onset of COVID-19. A full citation of all publications is beyond the scope of this letter, due to space limitations, but may be made available by the author upon request.

  • I take this opportunity to introduce, for the first time, a hidden bias titled “Facemask / COVID-19-Induced Bias” in eye investigations dealing with dry eye and associated diseases / parameters (such as lipid thinning of the eyes ).
  • To control for such a confounding effect, I further suggest that there is an urgent need to develop and validate a specific questionnaire to quantify face mask-induced dry eye (by type / duration / by stability, etc.) to be used in the real world.

I hope this comment will spark enthusiasm for the development of new tools to quantitatively measure dry eye disease under real conditions during the COVID-19 pandemic.


The author does not point out any potential conflicts of interest in this communication.

The references

1. Abusharha A, Alsaqar A, Fagehi R, et al. Tear Film Osmolarity Assessment in Diabetic Patients Using a TearLab Osmometer. Clin Optom. 2021; 13: 257-261. doi: 10.2147 / OPTO.S325768

2. Krolo I, Blazeka M, Merdzo I, et al. Mask-associated dry eye during the COVID-19 pandemic – how face masks are contributing to dry eye symptoms. Medical Arch. 2021; 75 (2): 144-148. doi: 10.5455 / medarh.2021.75.144-148

3. Dogru M, Katakami C, Inoue M. Tear function and ocular surface changes in non-insulin-dependent diabetes mellitus. Ophthalmology. 2001; 108 (3): 586-592. doi: 10.1016 / S0161-6420 (00) 00599-6

4. Saito J, Enoki M, Hara M, et al. Correlation of corneal sensation, but not basal or reflex tear secretion, with the stage of diabetic retinopathy. Cornea. 2003; 22 (1): 15-18. doi: 10.1097 / 00003226-200301000-00004

5. Prichard CE, Christman SD. Authoritarianism, conspiracy beliefs, gender, and COVID-19: Links between individual differences and concerns about COVID-19, mask-wearing behaviors, and the tendency to blame China for the virus. Psychol before. 2020; 11: 3130. doi: 10.3389 / fpsg.2020.597671

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