It has been ubiquitous that a carefully constructed nomogram could be designed to answer a focused question.Especially when appropriately interpreted and applied,it can be very valuable to clinicians and patients.Compared with traditional approach to selecting variables,the prominent advantage of Lasso regression lies in proceeding penalized regression on all the coefficients of variables.In addition,gradual process also Improve the stability of the predicting model.Due to the fact that risk or prognostic factors of postoperative NVG secondary to PDR still need further investigation,we developed and validated a prediction model of it.And this study was the first study that nomogram was applied in the PDR and postopoerative NVG.Moreover,internal validation by some related parameters has also testified the accuracy and effectiveness of the predicting model.
In our study,16.8% of PDR patients developed postoperative NVG.However,vitrectomy for proliferative diabetic retinopathy (PDR) has been reported to be associated with postoperative neovascular glaucoma (NVG) in 4–12% of cases[13–15]. A possible explanation of the higher incidence may ascribe to the different severity of underlying conditions in different patient groups.In the risk factor analysis,HbAlc,concomitant diabetic nephropathy(DN) and anti-VEGF therapy were associated with risk of postoperative NVG secondary to PDR.This nomogram suggested that low-level HbAlc(< 9%),alleviation of DN and anti-VEGF therapy may be the key individual factors that could reduce the incidence of NVG.However,our result contradicted to some previous researches[16–17] which reported that young men are the most involved patient group,because no difference was found in sex or age in our study.
Furthermore,we have found that high-level HbAlc may indicate the occurrence of postoperative NVG.Glycated haemoglobin is an important index of systemic factor,the blood level of which represents the average blood glucose concentration for recent 2–3 months.Microangiopathy caused by fluctuations in blood glucose levels has also been reported to contribute to the progression of ischemia[18].Previous publication highlighted that diabetic retinopathy is exacerbated when HbAlc is 6.5% or higher[19],the result of which correlates with our study.But a negative correlation between HbAlc and NVG onset was found by Masashi Sakamoto and his colleagues[20],where they ascribed the contradictory result to more administration of insulin in patients with NVG and the lack of investigation in the course of diabetic retinopathy.So further studies are still needed to observe the relationship between HbA1c level and NVG onset in PDR patients.
Selected by lasso regression model,diabetic nephropathy(DN) may be a significant risk factor of postoperative NVG onset.As previously reported,diabetic retionopathy has been associated with a faster decline in the estimated glomerular filtration rate(eGFR) among the general population and the elderly population with or without diabetes[21–22].Chi-Chih Hung[23] and his colleagues have also found that diabetic retinopathy was significantly associated with an increased risk for end-stage renal disease.In our study, DN could also be considered as an important risk factor for NVG onset to some extent.
It could not be overemphasized that VEGF is a pivotal angiogenic factor induced by retinal ischemia,and the vitreous level of VEGF at the time of vitrectomy is associated with a significant risk of both the postoperative progression of PDR and the occurrence of postoperative complications[24–25].Although anti-VEGF therapy has shown its advantages,its long-term effect could just last for a few weeks.So in the management of PDR, it is important to control ischemic stimuli primarily by anti-VEGF therapy combining with other methods,such as panretinal photocoagulation and vitrectomy.However,Wakabayashi et al[26] did not find significant relation between vitreous VEGF levels at the time of vitrectomy and postoperative late complications due to persistent overproduction of VEGF after surgery,which reminded us that it is essential to continuously detect and suppress the level of VEGF.We speculated that persistent secretion of VEGF might ascribe to underlying comorbidities that might exacerbate retinal ischemia.
Current study still have some limitations.Firstly,this nomogram requires external validation, and further research is needed to observe the risk and prognostic factors related to postoperative NVG onset.Secondly, the possibility of selection bias with respect to severity of the disease has to be considered in interpreting the results of this study.Thirdly,the retrospective nature.