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 of PC-PRL implantation in the treatment of high myopia and its complications

Objective: To study the effect of implantable posterior chamber phakic refractive lens (PC-PRL) in the treatment of high myopia and its effect on naked eye vision and retinal complications. Methods: A total of 110 patients (220 eyes) with high myopia admitted to our hospital from June 2017 to February 2019 were selected as subjects. All patients were treated with PC-PRL implantation. The UCVA, BCVA, intraocular pressure, corneal endothelial cell count and intraocular lens position (anterior chamber depth and arch height) were compared before and after the treatment. Results: 6 months after treatment, 68.18% of patients had UCVA between 0.6 and 0.9, 31.81% of patients had UCVA of more than 1.0, and 100.00% of patients had BCVA of more than1.0. The BCVA and UCVA values of patients at 1 week, 1 month, 3 months and 6 months after operation were significantly greater than those before surgery (P<0.05). There were no significant differences in BCVA and UCVA among 1 week, 1 month, 3 months and 6 months after operation (P>0.05). The intraocular pressure was significantly greater than that of the preoperative one week after operation (P<0.05). There was no significant difference between the intraocular pressure at 1 month, 3 months and 6 months after operation (P>0.05). There was no significant difference in corneal endothelial cell count and arch height before and after treatment (P>0.05). The depth of anterior chamber at 3 months and 6 months after operation was significantly less than that before operation (P<0.05). There was no significant difference in the anterior chamber depth between 3 months and 6 months after operation (P<0.05). There were 7 cases of corneal edema, 4 cases of high pressure eyes, 2 cases of refractive regression within 6 months, and 1 case of near-difficulty within 1 month. The total complication rate was 12.73%. Conclusion: PC-PRL implantation is effective in the treatment of high myopia, which can improve the naked eye and correct vision. At the same time, the incidence of retinal complications is low, which can be promoted and applied clinically.

Improving capacity building by implementing comprehensive eye care project,experiences from Kuandian County,China

The global campaign “Vision 2020： The Right to Sight” was officially launched in Geneva byDr. Gro Harlem Brundtland, the Director General of World Health Organization （ WHO ） in February 1999. This represents the global initiative for the elimination of avoidable blindness by the year 2020.1 Seven months later, the International Agency for the Prevention of Blindness （IAPB） General Assembly was held in Beijing, China. During the IAPB General Assembly, the Chinese Ministry of Health, China Disabled Person＇ s Federation together with WHO launched the national campaign “Vision 2020： The Right to Sight” in China.