Human eye ocular component analysis for refractive state and refractive surgery

AIM： To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length.METHODS： An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius（r1, r2, R1, R2） and thickness（t, T） of the cornea and lens, the anterior chamber depth（S1） and the vitreous length（S2）. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye（the rate function M）. A new criterion of myopia was presented via an effective axial length.RESULTS： For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj（j=1 to 6） were calculated for a 1% change of r1, r2, R1, R2, t, T（in diopters） M1=＋0.485, M2=-0.063, M3=＋0.053, M4=＋0.091, M5=＋0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=＋1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation.CONCLUSION： Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

Efficacy and mechanism of anti-vascular endothelial growth factor drugs for diabetic macular edema patients

BACKGROUND Diabetes is a serious public health concern in China,with 30%of patients developing retinopathy,and diabetic macular edema(DME)having the biggest impact on vision.High blood glucose level can cause retinal cell hypoxia,thus promoting vascular endothelial growth factor(VEGF)formation and increasing vascular permeability,which induces DME.Moreover,cell hypoxia can accelerate the rate of apoptosis,which leads to the aging of patients.In severe cases,optic cell apoptosis or retinal fibrosis and permanent blindness may occur.AIM To investigate and compare the efficacy,mechanism,and differences between two anti-VEGF drugs(Compaq and ranibizumab)in DME patients.METHODS Ninety-six patients with DME who attended our hospital from April 2018 to February 2020 were included and randomly divided into two groups(Compaq group and ranibizumab group).The groups received vitreal cavity injections of 0.5 mg Compaq and 0.5 mg ranibizumab,respectively,once a month.The best corrected visual acuity(BCVA),intraocular pressure(IOP),macular retinal thickness(CMT),macular choroidal thickness(SFCT),foveal no perfusion area(FAZ),superficial capillary density,deep capillary density,treatment effect,and adverse reactions were compared before and after treatment and between the two groups.RESULTS Before treatment and 1-mo post-treatment,there was no statistically significant difference in the estimated BCVA in both groups(P>0.05).BCVA decreased in the Compaq group 3 mo after treatment,and the difference was statistically significant(P<0.05).Before treatment,and 1 mo and 3 mo post-treatment,there was no statistically significant difference in the estimated IOP in either group(P>0.05).Before treatment and 1-mo post-treatment,there was no statistically significant difference in the estimated CMT,SFCT,or FAZ in either group(P>0.05).CMT and SFCT values decreased in the Compaq group 3 mo post-treatment,and the difference was statistically significant(P<0.05).Before treatment,and 1 mo and 3 mo post-treatment,there were no statistically significant differences in vascular density in the shallow or deep capillary plexi of the fovea,parafovea,or overall macular area between the two groups(P>0.05).Marked efficient,effective,and invalid rates were 70.83%and 52.08%,27.08%and 39.58%,and 2.08%and 8.33%in the Compaq and ranibizumab groups,respectively.The differences between the two groups were statistically significant(P<0.05).CONCLUSION Anti-VEGF drugs can effectively improve CMT and SFCT,without affecting microcirculation,thus providing an effective and safe treatment for patients with DME.