According to the results of the National Bureau of Statistics, the total population of China in 2017 was 1.4 billion. In terms of age composition, China has 240.9 million people aged 60 and above, accounting for 17.3% of the total population, of which 158.31 million are aged 65 and above, accounting for 11.4% of the total population. The number of elderly people in China accounts for about 20% of the world's total elderly population, according to international standards. The proportion of people over 60 years old in a country or region is more than 10%, and the proportion of people over 65 years old is more than 7%, which marks the entry of an aging society. AMD is the most common cause of blindness in people aged 55 and above, of which 55%-88% of AMD patients develop "legal blindness" (best-corrected visual acuity < 20amp 200) after the age of 70. With the progress of the aging population, more and more AMD patients need to be treated in our country. If AMD can not be treated in time and eventually become blind, it will have an indelible impact on the quality of life and mental health of elderly patients, and bring a heavy burden to the family and society.
The advent of anti-VEGF has brought great good news for AMD patients. From the initial control of the disease to the later development of ranibizumab, it can improve the vision of AMD patients. Anti-VEGF drugs are more and more widely used in clinical ophthalmology, but the clinical efficacy of anti-VEGF drugs varies greatly. With the emergence of vitrectomy, This surgical method is recognized by more and more ophthalmologists because of its minimally invasive and efficient advantages, and its clinical application is becoming more and more common. More and more patients after vitrectomy are faced within our work, and most of them are elderly patients. This group is more likely to receive anti-VEGF therapy after surgery. Previous studies have shown that the effect of anti-VEGF treatment after vitrectomy is worse than that of non-vitrectomy, but few studies can explain why vitreous injection of anti-VEGF drugs is less effective after vitrectomy. This is a practical problem to be solved in the future. Finding the root cause of the problem will help to improve the effect of anti-VEGF therapy after vitrectomy.
Concerning the effect of anti-VEGF drug treatment, the first thing we should think of is the temporal and spatial distribution of anti-VEGF drugs in the eyes. The higher concentration of the drug reaches the focus and the longer it takes to act on the focus, the more reason we have to believe that the treatment is more effective, and the only study we found shows that intravitreal injection of ranibizumab is given to rabbit eyes after vitrectomy and non-vitrectomy eyes. There was no significant difference in retinal drug concentration at different time points . This study showed that there was no difference in the temporal and spatial distribution of intravitreal injection of ranibizumab between vitrectomy and non-vitrectomy eyes. However, there are the following problems in this study: 1. The sample size of the study is small, and the results are poorly representative, which needs to be verified by further large sample studies. 2. In this study, only one anti-VEGF drug, ranibizumab, can not be used to explain the distribution of all anti-VEGF drugs in the retina, because different anti-VEGF drugs have different molecular weight, physical and chemical properties, metabolic effects, and so on. 3. A variety of anti-VEGF drugs should be selected for further study. The study was carried out in the rabbit eye in vivo, and finally, the rabbit was killed and the retinal tissue was taken to determine the concentration of ranibizumab. Although the anatomical structure of the rabbit eye is similar to that of the human eye, it is not a human eye. Whether the conclusion drawn in the animal eye experiment applies to the human eye remains to be studied, but limited to the limitations of the existing anti-VEGF drug concentration detection methods, there is no method to detect the retinal concentration of anti-VEGF drugs in vivo. It is contrary to medical ethics, so it is not suitable for human eye research. At present, the detection method of intraocular concentration of anti-VEGF drugs should be further studied to realize the detection of retinal drug concentration in vivo.
Pharmacokinetics plays an important role in drug tissue distribution and onset time. Studies have shown that the drug clearance rates of bevacizumab, ranibizumab, triamcinolone acetonide, ciprofloxacin, amikacin, ceftazidime, vancomycin, and amphotericin B in eyes after vitrectomy are higher than those in non-vitrectomy eyes[13-19]. A faster drug clearance rate can theoretically explain that the shorter retention time of anti-VEGF drugs in the vitreous cavity after intraocular injection of anti-VEGF drugs after vitrectomy, the lower concentration of anti-VEGF drugs in the vitreous cavity at the same time point, which can explain the reason for the poor efficacy of anti-VEGF treatment in the eyes after vitrectomy. Therefore, we have reason to believe that there is a difference in retinal drug concentration after vitrectomy and non-vitrectomy eyes after intravitreous injection of anti-VEGF drugs. Previous research results may have some deficiencies, which need to be verified by further research.
To sum up, at present, anti-VEGF drugs also play an important role in the eyes after vitrectomy, but the research on the distribution of drugs in the retina after vitrectomy and non-vitrectomy eyes is blank. Revealing the difference of retinal drug concentration between the two eyes is helpful to guide the treatment of anti-VEGF after vitrectomy. It has important guiding significance to obtain better therapeutic effects for more and more patients who need anti-VEGF therapy after vitrectomy.