In 1994, Hope-Ross MW  has researched 30 patients with refractory recurrent corneal epithelial erosion with poor therapeutic effect, and he has found that all the patients had MGD, most of which have meibomian gland atrophy and deletion; he suggested that there was a significant correlation between MGD and RCES. In 2014, scholars studied 100 RCES patients (117 eyes), which revealing that 60 percent of the RCES eyes were with moderate or severe MGD simultaneously that need to be treated. The most susceptible corneal erosion area is the most susceptible corneal epithelium area that the meibomian gland and dry eye are affected. It was believed that the levels of matrix metalloproteinase (MMP) caused by meibomian gland dysfunction were involved in the occurrence of RCES. In our research, it was also found that all patients of RCES had different degrees of meibomian gland dysfunction, the blepharolipin quality was lower than that of the control group, and the blepharolipin score was significantly higher than that of the control group; it was presented that meibomian gland dysfunction may be involved in the pathogenesis of RCES. This is consistent with the previous reports.
MGD was caused by various factors such as infection, inflammation, neurosecretory disorders, congenital abnormalities, and stellwag, while blepharitis would lead to severe MGD. It has been reported within China and overseas that there is a close relationship between the Demodex and anterior blepharitis; the Demodex was positively correlated with the symptom and evaluated scores; control the Demodex can significantly improve the symptoms of blepharitis [9.10]. Studies have suggested that the main cause of meibomian gland obstruction is hyperkeratosis of the terminal duct [11, 12]and opening. Meanwhile, the Demodex can be the bacteria carrier, bringing the bacteria to the palpebral edge during the process of secreting towards the palpebral edge. Plus, the decomposed esterase produced by bacteria may decompose the meibum into free fatty acids and other toxic medium, which will induce subclinical inflammation and release the pro-inflammatory factors, leading to increases the meibum viscosity or promotes epithelial keratinization of the glands, and cause the meibomian gland obstruction. Therefore, Demodex also plays a vital role in the pathogenesis of MGD. We also found that almost all the RCES patients have angiotelectasis of the palpebral edge and hyperkeratosis of the meibomian gland opening; multiple forms of secretions can be found attached in the root of most patients’ eyelash. All of the above are the characteristics of Demodex-infected blepharitis , the detection rate of palpebral edge Demodex in these patients was much higher than that of normal patients. In our study, the detection rate of Demodex in the normal control group was only 38.1%, which was similar in previous literature , while the detection rate of Demodex in RCES patients was 85%; this indicated that Demodex infection was very common in RCES patients. Chen Di  found in their study that the positive rate of Demodex in MGD patients was 86.4%. This also implied that a Demodex infection of the palpebral edge is involved in the pathogenesis of MGD and may be directly or indirectly involved in RCES patients' pathogenesis.
The current treatment of RCES mainly includes medication, wear corneal contact lens, mechanical and laser puncture of the anterior corneal stroma, and phototherapeutic keratectomy (PTK), etc. The main goal of the treatment is to relieve symptoms and reduce recurrence. Nevertheless, no treatment can prevent recurrence by now, and data shows that all treatments' recurrence rate was still above 20 percent[16–18].
Treatment for MGD aims to ameliorate the HBCI of meibomian glands, improve the tear film stability, and relieve the patients’ discomfort symptoms. The current treatment includes physiotherapy such as clean palpebral edge, hot compress, meibomian glands massage, etc.; medication like artificial tears eye drops, anti-inflammatory medicine, and antibiotic eye drops; along with diet therapy. IPL refers to a mature technology of dermatology for the treatment of skin telangiectasia, erythema, pigmentation, skin aging, and other diseases, and widely used for its good therapeutic effect. Toyos et al. found that IPL improved patients' ocular surface with facial acne, and they proposed IPL as a potential treatment for MGD. Previous studies have indicated that IPL can be absorbed selectively by melanin and heme in deep skin tissues, causing the destruction and decomposition of pigment groups, the coagulation of blood vessels, and the elimination of abnormal telangiectasia, reducing vascularization of the palpebral edge of MGD patients . In our study, after 3 times of IPL combined with a meibomian gland massage treatment, we found that the congestion of the palpebral edge was reduced, the secretion of meibum was significantly improved, and the deletion of the meibomian gland was also improved, which was similar to the results of other authors . We confirmed that IPL could kill bacteria and Demodex . Although Demodex still exist after three times of IPL treatment, the number of Demodex has decreased than before. Conversely, it is still unknown whether the palpebral edge's recovery is related to decreasing the Demodex number.
In our study, the ultimate goal of the treatment of MGD was to cure RCES. Surprisingly, we discovered that after 3 times treatments of IPL with meibomian gland massage therapy, the meibomian gland function and the amount of Demodex were significantly decreased, and corneal erosion of the patients has been effectively controlled. Plus, throughout the follow-up period, there was just 1 case that relapsed again. However, the recurrence rate was significantly less than before; the patients have only the corneal epithelium's punctate turbidity, compared to the recurrence before when the patients performed a large corneal epithelial defect, the improvement was remarkable. Our treatment was more effective than drug-only treatment. Our results showed that the treatment of MGD and Demodex is capable of effectively controlling RCES, which may offer a new approach to non-invasive treatment for the clinical treatment of RCES.
It is generally acknowledged that after 3 times of IPL treatment, the therapeutic effect can last 6 months to 1 year. Our study's follow-up period was 1 year; during this period, the disease was effectively controlled. Yet, our next study will be focused on whether there will be relapse as the follow-up period extends. Meanwhile, on the therapeutic mechanism of RCES, whether treatment of IPL is only to improve the meibomian gland function and reduce the amount of Demodex is the direction of our future research.