The present study described the characteristics and outcomes of 160 patients who were hospitalized with ocular chemical injuries at the Jinshan District in Shanghai over a 5 year period. A large number of patients presented to our hospital due to chemical injuries, where a large number of chemical enterprises were located nearby. The reported incidence ranges from 1.5 per 100,000 to 13.3 per 100,000[4, 6, 9].In addition, 1480 cases suffering from chemical injuries were reported to the Victorian Poisons Information Centre in Australia, supporting a telephone-based advice service, but the incidence did not be calculated[10].However, only a few patients, ranging from 10 to 99, hospitalized for ocular chemical injuries[11-13].This difference in the hospitalized number of ocular chemical injuries between previous studies and our study might be due to the influence of factors such as number and density of chemical factories and workers, levels of patient education and public health interventions, and severity of chemical injuries. Moreover, the incidence of ocular chemical injuries might be underestimated due to the loss of patients who might have sought medical care in other hospitals and patients with minor injuries who received only outpatient treatment or declined admission.
Most victims were young men engaged in industrial or construction work, which was in agreement with previous studies. Men aged 18–64 years[4, 10]and children aged 1–2 years[7, 14]might be at the highest risk for ocular chemical injury in the workplace or residential locations due to occupational exposure and topical personal products and cleaning agents. Although the delay in the presentation of 133 (83.1%) patients for medical treatment was less than 24 hours after injury, only 64 (40.0%) patients were at the consultation room in less than 3 hours. This suggested that the awareness of prompt treatment should be enhanced. In addition, grades Ⅱ and Ⅰ were the most classification of the severity of ocular chemical injury in this study, indicating that the bulk of chemical injuries were mild to moderate.
The most common causative chemical varied by studies. The present study found that the most common causative chemical was unknown and mixed substances, followed by plural acid and alkali agents. Alkali agents were reported to be the most frequent causes of ocular chemical injuries[6, 15].However, Haring et al[4]found that the majority (88.2%%) of ocular chemical injuries were caused by chemical agents of unknown acidity or even from unknown chemicals, and only a few cases were classified as alkaline or acidic injuries. Furthermore, an injury of the eye might be due to any chemical, solid, liquid, or aerosol[16].To the best of our knowledge, this is the first study to report on the phase of the offending causative agent: the most common condition was liquid, followed by a mixture of liquid and solid, then gas, and the least was solid.
Ocular chemical injuries could result in significant damage to the ocular surface epithelium, cornea, anterior segment, and even retina and optic nerve[17].In this study, elevated IOP was the most frequent problem. An estimated incidence of secondary glaucoma was reported to be more than 20% after a severe chemical injury[18].Lin et al[19]found that a higher Roper-Hall grade was associated significantly with glaucoma treatment. Furthermore, long-term glaucoma medication was used in most eyes with elevated IOP in the first week after injury. The development of glaucoma might be due to synechiae and angle closure by secondary chronic inflammation, ciliary body necrosis in deeply penetrating alkali injuries, damage to the trabecular meshwork, severe uveitis, long-term steroid use, phacomorphic or phacolytic mechanisms, and contraction of the sclera[8].Moreover, progressive optic nerve damage of glaucoma was observed in some patients with normal IOP, probably due to the subtle damage in ganglion cell layer by the alkali and the abnormal sensitivity to normal pressure[20].Cabalag et al[7]reported that lagophthalmos was the most common early complication, and corneal scarring was the most common late complication. Central corneal opacity or perforation was the most common complication in severe chemical injuries, and cataract and retinal attachment were also observed[6].
In the current study, the risk factors for poor visual outcomes in patients with ocular chemical burns were identified as older age, poor initial BCDVA, and irrigation 24 hours after injury. Better initial BCDVA represented milder ocular chemical injuries, which was in agreement with the previous report that visual prognosis was better in eyes with mild chemical injuries[21].This study confirmed the fact that immediate and extensive irrigation should be commenced immediately because it could improve prognosis. Irrigation after a chemical injury was to restore the physiological pH of the eye as rapidly as possible. The normal pH of the ocular surface after irrigation could return the aqueous pH in the eye to normal within 30 min[22].The association between visual outcome and AMT was statistically marginal in the present study. AMT, as a temporary patch or a permanent graft, was effective in treating chemical injuries[23, 24].Furthermore, topical application of amniotic membrane extract was also effective in reducing inflammation and promoting reepithelization in the treatment of chemical injuries, especially for mild-to-moderate acute cases[25].
This study had several limitations. First, the retrospective nature of this study might result in incomplete patient selection and collection of data. Second, selection bias was possible because selecting the patient population according to ICD-10-CM might exclude some eligible patients. Third, the 1-month follow-up period might be short, and the visual outcome and the situation of ocular surface in these patients might still fluctuate. In addition, socioeconomic parameters, such as level of education, were not evaluated.