**9. Discussion**

Two types of IPL devices (E. Eye; E-SWIN, Paris, France, and Lumenis M22; Tel Aviv, Israel) were used in the studies. The E. Eye device produces a wavelength from 580 to 1200 nm, whereas the Lumenis M22 produces a 400 to 1200 nm wavelength. The broader wavelength of Lumenis M22 can theoretically achieve a better bactericidal effect. The light between 400 and 700 nm (415 most effectively absorbed) for *Propionibacterium acnes*, 500 nm, probably induces photo-thermolysis of vessels and prevents the leakage of inflammatory cytokines into the ocular surface. The yellow wavelength of IPL can target the oxyhemoglobin in superficial skin vessels, which have light absorption peaks of 578 nm. The sustained reduction in telangiectasia (decrease leakage of interleukins such as IL-17A and IL-6) was observed in patients with rosacea-related MGD after repeated IPL administration. On the contrary, the red-light spectrum (580–1200 nm) delivered by the E. Eye device has a more inadequate bactericidal effect. Still, it can potentially penetrate deeper into the skin and target the underlying sebaceous glands. And the use of the protective eye goggles is unclear or different between studies.

The different wavelength is another confounding factor, although 500 to 600 nm was used in most studies.

There are two intense pulsed light patterns: Optimal Pulse Technology (OPT) with three (3 weeks duration) consecutive treatments (10–14 J/cm2 ) is more effective in improving MG function in lower eyelids and partial tear film signs than Intense Regulated Pulsed Light (IRPL) with four treatments (9–13 J/cm2 ) on days (D)1, D15, D45, and D75 treatment. The method of light patterns used in each study causes a little disagreement.

Moreover, discrepancies between the ocular symptoms and signs of dry eye and the significant association of sleep disorders and ocular surface problems are common [54].

Besides, dry eye symptoms are more highly correlated with non-ocular conditions (sometimes somatization) than dry eye signs. The questionnaire does not any focus on a specific drug history for insomnia or antidepressants with anticholinergic effects.

It is also not irrational to conclude that identical findings would have been observed in a particular demographic with various skin type dispensation [23]. Another restriction was the lack of a gold standard for diagnosing and using TBUT as the essential result measure. Many reports of DED use tear breakup time; as a result, measure, but this outcome measure is troublesome for many reasons [23]. This procedure has a mild specificity/sensitivity. The findings are depending on the amount of coloring (fluorescein) ingrained in the eye, and the method is highly subjective to the observer's estimation. As a result, TBUT varies from one investigator to the next, even within the same investigator. While this averaging approach minimized TBUT measurement uncertainty, a more accurate and quantitative primary result indicator (e.g., NIBUT) may be a better option for investigation.

And finally, in the present pandemic, the eye route of infection must be considered so each sufferer should be treated as a potential coronavirus carrier. As a potentially beneficial method for treating and relieving the effects of DES and avoiding COVID-19, various compounds may be added into the food and then used as ready-made supplements. Polyunsaturated fatty acids had the most reported medicinal benefit, as they help alleviate the disease's infectious aspect. Vitamins, omega acids, and other nutritional nutrients can be discussed with each person individually.

## **10. Conclusion**

To summarize, IPL is an attractive alternative solution for sufferers with DED caused by MGD, and that the effect of IPL is real rather than a placebo effect.

#### **11. Take-home messages**

It is essential to address the following points:

1.As we know, the MGD is not yet an approved indication for IPL therapy by the United States Food and Drug Administration. Regarding the safety of IPL and reported adverse events (14% of patients: cheek swelling, conjunctival cyst, floaters, blistering, hair loss at brow and forehead, light sensitivity, and facial redness). The IPL treatment should adhere to lower eyelids for now and in the presence of ocular protection due to the report about uveitis and iris damage. Although adverse effects usually resolved without treatment within one week

and iris damage has been reported during cosmetic IPL therapy on the upper eyelids by no ophthalmologic health care workers.

	- Increased exercise and higher estrogen levels were also associated with improved tear quantity during the ovulation phase [56].
	- The majority of the available studies on nutritional supplementation [57] for DED did not evaluate the micronutrient dietary intake nor their plasma level, representing the major limitation of the existing literature. However, Epitropoulos et al., Malhotra et al., and Oleñik et al. showed significant improvement in OSDI, TBUT, lid margin inflammation, and meibum expressibility placebo, using Eicosapentaenoic Acid (EPA) + Docosahexaenoic Acid (DHA) [57].
	- On the other hand, sleep deprivation reduces androgen levels parasympathetic activity. It makes high levels of stress hormones (norepinephrine and cortisol) and reduce tear secretion lacrimal system function that reversed after 14 days of rest [58] (**Table 1**).


#### *Dry Eye Syndrome - Modern Diagnostic Techniques and Advanced Treatments*


**Table 1.** *Abbreviations and definitions.*
