Introduction

The eye is an essential sensory organ in the human body. About 90% of the information people obtain from the outside world through the sensory organs is done through the eyes.1 2 The fine structure of the eye, even a slight injury, may cause structural changes, resulting in decreased visual function or even complete loss, which will lead to immeasurable losses to individuals, families and society.2 3 Data from the World Report on Vision indicate that at least 2.2 billion people worldwide have visual impairment or blindness.4 Fricke et al found that 1.8 billion people worldwide have presbyopia, with 826 million of them suffering from near vision impairment due to unaddressed presbyopia.5 Flaxman et al Lancet Global Health have conducted an estimate of the number of people with distance vision impairment or causes of blindness was estimated globally.6 At least 237.1 million people worldwide were expected to have moderate or severe distance visual impairment in 2020, the number that includes unaddressed refractive error (127.7 million), cataract (57.1 million), age-related macular degeneration (8.8 million), glaucoma (4.5 million) and diabetic retinopathy (3.2 million).6 In 2020, 38.5 million people worldwide were expected to be blind, mainly due to cataract (13.4 million), unaddressed refractive error (8.0 million) and glaucoma (3.2 million).6 In addition, the ageing of the population, coupled with lifestyle changes, is still leading to an increase in the number of eye diseases and visual impairment.4 At the same time, the treatment of many diseases in ophthalmology suffers from undefined pathogenesis, ineffective western medical treatment or local invasive drug injections as the main treatment, which can lead to treatment non-response or resistance, expensive treatment, limited maintenance of drug efficacy, injection-related complications and drug-related complications, which impose a heavy physical and psychological burden on patients. Therefore, health systems in various countries face considerable challenges4 and need to seek alternative drugs to treat eye diseases.

Traditional Chinese Medicine (TCM) ophthalmology has been an integral discipline of TCM for >2000 years. The unique theories and applications were developed on the basis of TCM and have gradually evolved.7 The earliest existing medical text in China, the Yellow Emperor’s Inner Classic (Huang Di Nei Jing, 黄帝内经), first proposed the anatomy and physiology of the eyes.7 8 Acupuncture treatments for >30 eye conditions and many systemic diseases were described in this book.7 8 In 1644, at the end of the Ming dynasty, Fu Ren-yu (傅仁宇) wrote A Close Examination of the Precious Classic on Ophthalmology (Shen Shi Yao Han, 审视瑶函) based on the former works on TCM ophthalmology.8 The book recorded 108 eye diseases and included >300 prescriptions.8 Among them, the listed Shi Hu Ye Guang Wan (Dendrobium and Night Light Pill, 石斛夜光丸) and Zi Yin Di Huang Wan (Yin-enriching Rehmannia Pill, 滋阴地黄丸) are famous ophthalmic medicines which are still in clinical use. Currently, ophthalmology education and research departments have been established in universities, and ophthalmology clinics and wards have been opened in hospitals in China.2 9 10 In addition, universities in some provinces have opened master’s and doctoral programmes in TCM ophthalmology.8 Moreover, TCM Ophthalmology Association and the Integrated Ophthalmology Association have been established in various regions and cities to provide a platform for the development of TCM ophthalmology.7

With numerous eye prescriptions and treatments, we have formed a unique and complete treatment system, including TCM decoction, acupuncture, massage, topical applications and Chinese Patent Medicines (CPMs).11 CPMs are the preparation that can be directly used to prevent and treat diseases under the guidance of TCM theory, using Chinese herbal slices as raw materials and made into a dosage form with certain specifications according to the prescribed prescriptions and standards.12 The Beneficial Formulas from the Taiping Imperial Pharmacy (Tai Ping Hui Min He Ji Ju Fang, 太平惠民和剂局方), which was issued in 1151, was compiled by the Northern Song Dynasty Tai Medical Bureau and was the first official standard for CPMs in the world.13 The book was divided into 10 volumes and 14 categories, with 788 prescriptions. It has a clear structure detailing the actions, indications, compositions, concoction requirements, production process, dosage, administration methods and contraindications of each prescription, which facilitates clinical use and passes it down to this day without fail. Many CPMs in the book, such as Huo Xiang Zheng Qi San (Agastache Qi-Correcting Powder, 藿香正气散), Shen Ling Bai Zhu San (Ginseng, Poria and Atractylodes macrocephala Powder, 参苓白术散) and Li Zhong Wan (Center-Regulating Pill, 理中丸) are still in clinical use.14 Compared with TCM decoction, CPMs can be taken directly without being decocted, which is very convenient for patients with acute and critical illnesses and those who need long-term treatment. In addition, CPMs are widely used in China because of their small size and unique packaging, which makes them easy to store and carry.15 16 However, clinicians, patients and policymakers in China and other countries remain sceptical about the intervention due to the lack of comprehensive evidence on oral CPMs in ophthalmology. Therefore, in an era of evidence-based healthcare, it has become increasingly important to use appropriate methods to organise and summarise the evidence.

Peters et al pointed out that when the articles have not been thoroughly reviewed or have a considerable heterogeneity, it is impossible to conduct a more detailed systematic review of the evidence; the scoping review can be used.17 Contrary to other review methods, an attractive feature of the scoping review method is that it does not limit the parameters of the review to randomised controlled trials, nor does it require the articles included in the study to be methodologically consistent.18 By systematically searching, selecting and integrating existing knowledge, scoping review can be used to explore exploratory research questions, map types of evidence and gaps in research related to specific fields and guide future research priorities.19 Therefore, the scoping review will provide a systematic overview of the clinical use of oral CPMs in ophthalmology, mapping the distribution of relevant evidence. It will provide a basis for decision-making for ophthalmology clinicians and relevant researchers. Moreover, it can also promote the research and rational use of oral CPMs and provide a new option for global eye disease control.