Increased photokeratitis during the coronavirus disease 2019 pandemic: Clinical and epidemiological features and preventive measures.

ABSTRACT: An increased incidence of photokeratitis has occurred during the coronavirus disease 2019 (COVID-19) pandemic due to improper and unprotected use of ultraviolet lamps. Here, we summarize the clinical and epidemiological features of this increased incidence of photokeratitis and share advice in using health education to prevent it.We collected data from patients diagnosed with photokeratitis from October 7, 2019 to December 1, 2019, and from February 17, 2020 to April 12, 2020, and compared the frequency of onset, site of ultraviolet radiation (UVR) exposure, reason for exposure, exposure time, and recovery time. We also implemented and evaluated multiple measures of public health education to prevent increased disease.After the COVID-19 outbreak, the frequency of onset of photokeratitis increased significantly, especially among young women. The main reason for UVR exposure changed from welding to disinfection. The incidence sites varied, and the exposure time was longer. As a result, patients needed a longer time to recover. Positive health education was an useful and convenient measure to prevent the disease.While the COVID-19 pandemic is ongoing, more attention should be paid to public health and implement positive measures to prevent photokeratitis.

Introduction

Photokeratitis, first reported in 1859 by Charcot, is a common ophthalmic emergency or occupational injury caused by ultraviolet radiation (UVR). In a plateau, ocean, or snowy mountain, where sunlight is strong, the same damage may also occur; therefore, it is also referred to as solar ophthalmia or snow blindness.[ The clinical syndrome presents with ocular pain, tearing, conjunctival chemosis, blepharospasm, and deterioration of vision, typically several hours after exposure.[

Photokeratitis results from acute high-dose or suprathreshold UVR.[ The cornea, particularly the corneal epithelium, absorbs UVR predominantly in the range of 100 to 280 nm, acting as a major protective shield against UVR. The biological damage is mainly due to the generation of reactive oxygen species as a result of an imbalance between reactive oxygen species generation and antioxidant defense.[

Normally, welding workers, mountaineers, skiers, and beach recreationists are susceptible to photokeratitis.[ In Suzhou, Jiangsu Province, China, located at a latitude of 31.3°, which is far from both the ocean and mountains, photokeratitis mainly affects welding workers, and most cases are sporadic.[ However, the situation has changed since the introduction of the coronavirus disease 2019 (COVID-19).

The COVID-19 pandemic caused by SARS-CoV-2 has resulted in significant morbidity and mortality around the world and has resulted in great panic among people.[ A tremendous need for disinfection has arisen not only in hospitals but also in homes, dormitories, workshops, storefronts, and other places due to fear of infection. To meet the need for disinfection, ordinary people have widely purchased and used ultraviolet lamps because of their effectiveness and simplicity.[ However, improper and unprotected use of ultraviolet lamps leads to significantly increased photokeratitis.

When we noticed an increased incidence of photokeratitis, we took preventive measures, including health education and circulating informative articles online and via WeChat. After these public education measures, the frequency of onset gradually decreased. In this article, we summarize the clinical and epidemiological features of an episode of increased photokeratitis during the COVID-19 outbreak and share our experience in preventing it.

Methods

Patients

We collected data from patients diagnosed with photokeratitis at the First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China, between February 17, 2020 and April 12, 2020 (8 weeks), and reviewed cases of patients with photokeratitis treated at the same hospital between October 7, 2019 and December 1, 2019 (8 weeks) as the control group by checking their medical records and contacting them by telephone. The data collected included sex, age, occupation, and the time and course of exposure to UVR. The author who collected and analyzed the data was unaware of the grouping. Ethical approval was obtained from the ethics committee of the First Affiliated Hospital of Soochow University (No. 20200043). Informed consent was obtained from all patients.

Diagnosis, treatment, and health education

A diagnosis was made according to each patient's history, including exposure to UVR 24 hours before onset; symptoms that included unilateral eye pain, photophobia, and tearing; conjunctival hyperemia and corneal epithelium shedding seen on examination with a slit lamp; and positive punctate fluorescent staining.

To promote corneal epithelial healing and prevent infection, patients were treated with recombinant bovine basic fibroblast growth factor eye drops (21,000 IU/5 mL, YiSheng Co., Zhuhai, China) 4 times per day, ofloxacin ointment (3 mg/L g, Santan Co., Osaka, Japan) 2 times per day, cold compresses, and sufficient rest.[ Daily follow-up was required to observe the corneal condition until complete epithelial healing occurred, which took no >3 days.

Immediately following the upward trend of photokeratitis in the first 2 weeks of the 2020 time period, we carried out health education, informing people that they should leave the room to avoid UVR when the ultraviolet disinfection equipment was working, that the recommended disinfection time was about 30 minutes, and that the room should be adequately ventilated after disinfection. Education also included the pathology and treatment of photokeratitis and other issues. We explained these facts to patients at their hospital visits and asked them to tell their family and friends. We published related articles on our hospital website and the social networking platform WeChat, and disseminated these articles via doctors’ WeChat friend circles. We also distributed educational material in large factories and communities (Fig. 1).

Figure 1

Scanned copy of distributed leaflets and screenshot of WeChat article (above), the translated version (below).

Statistical analysis

Results are presented as means ± SD and were analyzed statistically using SPSS 20.0 (IBM, Armonk, NY). A chi-squared test was used to compare the frequency of onset, percentage of symptom relief, and epithelial healing. Analysis of variance was performed to compare exposure time, time from exposure to symptoms, and visual acuity. Differences were considered significant when P < .05.

Results

Demographic information

According to the hospital information system, 31 patients were diagnosed with photokeratitis between October 7, 2019 and December 1, 2019, compared with 109 patients between February 17, 2020 and April 12, 2020. Of 31 patients diagnosed before the COVID-19 outbreak, 22 patients received a complete and effective telephone review. Before the COVID-19 outbreak, the patients consisted of 23 men and 8 women, aged 22 to 58 years old, with an average age of 37.1 years. After the COVID-19 outbreak, the patients consisted of 55 men and 54 women, aged 21 to 54 years old, with an average age of 32.1 years (Table 1). Overall, more young women were diagnosed in the later period. Most patients complained of eye pain, while others complained of epiphora, blurry vision, and other symptoms.

Table 1

Patient characteristics.

				Chief complaint
	Total number	Sex (M/F)	Average age (age range)	Pain	Epiphora	Blurry vision
Before the COVID-19 outbreak	31	23/8	37.1 (22–58)	24	3	2
After the COVID-19 outbreak	109	55/54	32.1 (21∼54)	73	17	12

Frequency of onset

We defined observation periods as lasting 2 weeks, in accordance with the 14-day SARS-CoV-2 latency period. Before the COVID-19 outbreak, there were 7, 9, 7, and 8 patients in the first, second, third, and fourth 2-week periods, respectively, showing little difference. After the COVID-19 outbreak, the frequency of onset increased significantly, with 25 patients diagnosed in the first 2 weeks and a peak of 38 patients in the second 2-week period. After the implementation of health education, the number of patients decreased gradually, with 27 patients presenting in the third 2-week period and 19 patients in the fourth period, which was still higher than before the COVID-19 outbreak (Fig. 2).

Figure 2

The frequency of onset before and after the COVID-19 outbreak. ∗ P < .05, ∗∗ P < .01, the statistical difference of frequency in each period.

Comparison of incidence

There was a strong difference in the course of exposure to UVR before and after the COVID-19 outbreak, which was the main reason for the increased incidence. Before the COVID-19 outbreak, only 9% of cases were clustered, and this percentage increased to 30% after the COVID-19 outbreak (Fig. 3A). Before the COVID-19 outbreak, welding was the main reason for UVR exposure (approximately 68%), while disinfection was the main reason following the COVID-19 outbreak (approximately 57%) (Fig. 3B). Before the COVID-19 outbreak, UVR exposure occurred mainly at construction sites (approximately 64%), but it occurred at construction sites, workshops, storefronts, and homes after the COVID-19 outbreak (Fig. 3C).

Figure 3

Structure of incidence. A: Percentages of sporadic and clustering diseases. B: Percentages of reasons for UVR exposure. C: Percentages of sites of UVR exposure. UVR = ultraviolet radiation.

Exposure duration

The duration of exposure to UVR is a key factor in corneal epithelial damage. Before the COVID-19 outbreak, there was little difference during the different observation periods; therefore, we averaged the exposure duration over 8 weeks (8.7 minutes). After the COVID-19 outbreak, the average exposure duration increased to 16.7 minutes (P < .05). Although the frequency of onset decreased in the third and fourth 2-week periods in the 2020 period, the exposure duration varied little among all periods (P = .376) (Fig. 4).

Figure 4

UVR exposure duration before and after the COVID-19 outbreak. ∗ P < .05, statistical difference of UVR exposure duration in each period compared with that before the COVID-19 outbreak, there was no statistical difference of UVR exposure duration among the 4 periods after the COVID-19 outbreak. COVID-19 = the coronavirus disease 2019, UVR = ultraviolet radiation.

Clinical features

The time from exposure to symptoms ranged from 6 to 12 hours, with an average of 9.5 hours before the COVID-19 outbreak and 9.2 hours after the COVID-19 outbreak, showing no statistical difference (P = .549, Fig. 5A). Patients complained of severe pain or burning sensation in unilateral eyes, difficulty in opening the eye, photophobia, tearing, and other symptoms. Typical photokeratitis presented as conjunctival hyperemia, corneal epithelium shedding, and positive punctate fluorescent staining (Fig. 5B and C). No large corneal epithelial defect, corneal stromal edema, corneal infection, or other serious keratopathy was observed in any patient.

Figure 5

Clinical manifestation of photokeratitis. A: Average time from exposure to symptoms. There was no significant difference between before and after the COVID-19 outbreak. B: Typical slit-lamp image. C: Epithelial punctate fluorescent staining. COVID-19 = the coronavirus disease 2019.

Recovery

The average best-corrected visual acuity after photokeratitis was 0.23 ± 0.07 logMAR and 0.25 ± 0.08 logMAR before and after the COVID-19 outbreak, respectively, with no statistical difference (P = .448). By 72 hours after treatment, the average best-corrected visual acuity improved significantly to 0.04 ± 0.02 logMAR and 0.05 ± 0.02 logMAR (both P < .01 vs before treatment) before and after the COVID-19 outbreak, respectively. In addition, the improved visual acuity after treatment showed no statistical difference before and after the COVID-19 outbreak (P = .753, Fig. 6A).

Figure 6

Recovery from photokeratitis. A: Best-corrected visual acuity before and after treatment. B: Percentage of symptom relief at different times. C: Percentage of epithelial healing at different times. ∗ P < .05, ∗∗ P < .01, statistical difference of each data.

After treatment, all patients were cured in a short time, and no complications were observed. Before the COVID-19 outbreak, 36% of patients experienced symptom relief within 6 hours, 77% within 12 hours, and 100% within 24 hours. This changed to 21% (P < .05) within 6 hours, 69% (P = .388) within 12 hours, and 96% (P = .736) within 24 hours after the COVID-19 outbreak (Fig. 6B), which was lower than before. Before the COVID-19 outbreak, the corneal epithelium healed in 41% of patients within 24 hours, 82% within 48 hours, and 100% within 72 hours. However, this changed to 33% (P < .05) within 24 hours, 74% (P = .451) within 48 hours, and 100% (P = .924) within 72 hours (Fig. 6C), which was also slower than before.

Discussion

Photokeratitis is not a complex disease and has a definite pathogeny and good prognosis. As economic development and protection for workers and travelers have progressed, the incidence has tended to decrease.[ However, the sudden increase in this disease during the COVID-19 outbreak in Suzhou was unexpected, highlighting the importance of “simple” disease management and public health education.

Although COVID-19 had been reported as early as the end of December 2019, it did not draw public attention until January 20, 2020, which was also the Spring Festival holiday in China. The vacation was extended by the government, and people returned to work gradually in mid-February. Therefore, we chose February 17, 2020 as the beginning of the observation period. As the incubation period of COVID-19 is normally considered to be 14 days and many policies also depend on this time,[ we chose 2 weeks as the observation period. On April 12, we stopped observation when we found that the frequency of onset substantially decreased. For the control group, we chose October 7, 2019 to December 1, 2019.

According to the results, there was an increase in young women suffering from photokeratitis, which was in accordance with the change in the susceptible population. Before the COVID-19 outbreak, patients with photokeratitis were mainly welding workers, who were mostly middle-aged men. After the COVID-19 outbreak, more assembly line workers and shop assistants, most of whom were young women, were affected by the disinfection of workshops and storefronts. The leading reason for UVR exposure also changed from welding to sterilization after the COVID-19 outbreak. The percentage of cases of UVR exposure at home, workshops, and storefronts was almost equal in the second period, indicating that improper and unprotected use of ultraviolet lamps was a common phenomenon, and publicity and education on this issue was necessary and urgent.

There is no large-scale epidemiological study on the incidence of photokeratitis because it is affected greatly by social development, employment structure, latitude, topography, and other factors. According to our hospital information system, the change in the number of photokeratitis cases in 1 month was not obvious, and most cases were sporadic before the COVID-19 outbreak. Photokeratitis caused by improper and unprotected use of ultraviolet lamps has also occurred in Hong Kong and the United States.[ A total of 7 patients were reported in a study from the United States, and the reasons, exposure times, and sites were similar to our results, indicating that more attention should be paid to this issue.

UVR can be divided into 3 bands: UVA at 320 to 400 nm, UVB at 290 to 320 nm, and UVC at 200 to 290 nm. Shorter UVR wavelengths have more energy and a greater potential for ocular damage.[ For disinfection, most ultraviolet lamps on the market produce UVR at 200 to 280 nm, which is more dangerous to the eye. First, the corneal epithelium absorbs most UVR wavelengths because of its high protein and nucleic acid content. Then, oxidative photodegradation and production of reactive oxygen species are responsible for most damage in the course of photokeratitis.[ Despite the potential danger, there has been no regulation or restriction for the production and sale of ultraviolet lamps, which also contributes to an increased incidence of photokeratitis.

UVR exposure time was recorded mainly based on descriptions from patients, and most patients remembered the exposure course. Although it was a subjective variable, we considered it meaningful because it reflected this fact. Most welding workers are aware of UVR dangers, and exposure in this population is mainly due to a lack of caution or inadequate protection, so the exposure duration is short. However, patients with eye damage due to ultraviolet lamps are not aware of UVR damage, and they may be in a UVR environment for a long time. To make matters worse, photokeratitis is typically characterized by a delay between exposure and the beginning of symptoms,[ which further prevents people from leaving the UVR environment. Correspondingly, patients seen during the COVID-19 outbreak had a tendency toward delayed symptom relief and epithelial healing, which may be due to the longer UVR exposure and consequent damage.

Physicians should not only focus on diseases and patients but also on public health. At the very beginning of the period of increased incidence, when a few patients came to the hospital due to improper ultraviolet lamp use, we realized that more people may suffer the same problem. Therefore, we took measures to warn the public and explain how to safely use ultraviolet lamps. We asked every patient to talk about this issue to their family and colleagues, especially workshop supervisors and shopkeepers, to avoid the same problem. Our website articles and WeChat postings have been read cumulatively over one hundred thousand times. With our efforts, the frequency of onset began to decrease during the third 2-week period. Other doctors in Shanghai, Beijing, and other parts of China also performed the same measures during this period.

Some limitations of our study should be noted. First, some objective clinical information, such as intraocular pressure and corneal fluorescence staining score, were not evaluated. Second, this was a retrospective study with a small sample restricted to our hospital in Suzhou. A large sample over multiple locales is needed to verify the results of our study.

Conclusion

The unexpected increase in photokeratitis during the COVID-19 outbreak suggests the importance of paying close attention to public health. Health education and positive publicity proved to be effective and convenient measures to prevent such a situation.

Author contributions

Data curation: Jing Lou.

Formal analysis: Ye Ji.

Writing – original draft: YingMing Wang.

Writing – review & editing: ZhenYu Wang.