BACKGROUND:Myopia is becoming a huge burden on the world's public health systems. The purpose of this study was to explore the effect of brimonidine in the treatment of form-deprivation myopia (FDM) and the relationship between intraocular pressure (IOP) and myopia development.METHODS:Monocular form deprivation myopia (FDM) was induced in three-week-old pigmented male guinea pigs. They were treated with 3 different methods of brimonidine administration (eye drops, and subconjunctival or intravitreal injections). Four different concentrations of brimonidine were tested for each method (2µg/µL, 4µg/µL, 20µg/µL, and 40µg/µL). All treatments continued for a period of 21 days. Tonometry, retinoscopy, and A-scan ultrasonography were used to monitor intraocular pressure, refractive error and axial length (AL), respectively.RESULTS:Treatment with subconjunctival brimonidine at 40µg/µL, and intravitreal brimonidine at 2µg/µL and 4µg/µL, inhibited the development of FDM. The myopic refraction, excessive axial length, and elevation of IOP were significantly decreased. Brimonidine in eye drops was ineffective.CONCLUSION:Brimonidine at appropriate doses significantly reduced the development of FD myopia in guinea pigs. The IOP may change with FD myopia.

Abstract Background This study aimed to compare the visual outcomes of the first operated eyes with those of the second operated eyes following small-incision lenticule extraction (SMILE). Methods A total of 202 patients (404 eyes) underwent SMILE using the tear film mark centration method for myopia and myopic astigmatism correction. Baseline characteristics, objective optical quality, decentered displacement, induced corneal aberrations, and modulation transfer function (MTF) values were assessed. Linear regression analyzed the relationship between decentration and visual quality parameters, including corneal aberrations and MTF values. Results No significant difference was observed in objective visual quality, efficacy, and safety indexes between the two groups (all P > 0.05). The average decentered displacement for the first and second surgical eyes was 0.278 ± 0.17 mm and 0.315 ± 0.15 mm, respectively (P = 0.002). The horizontal coma in the first surgical eyes were notably lower than in the second (P = 0.000). MTF values at spatial frequencies of 5, 10, 15, and 20 cycles/degree (c/d) were higher in the first surgical eyes compared to the second (all P < 0.05). Linear regression indicated that high-order aberrations (HOAs), root mean square (RMS) coma, spherical aberration, horizontal coma, vertical coma, and eccentric displacement were all linearly correlated. Furthermore, MTF values exhibited a linear relationship with eccentric displacement across these spatial frequencies. Conclusions There was no discernible difference in visual acuity, efficacy, or safety between the two operated eyes. Nonetheless, the first operated eyes exhibited reduced decentered displacement and demonstrated superior outcomes in terms of horizontal coma and MTF values compared to the second operated eyes following SMILE. The variations in visual quality parameters were linearly correlated with decentered displacement.

角膜具有包裹、保护眼睛及折光作用,是重要的屈光介质. 角膜的位置结构使其容易受到外界侵害,如异物入眼、植物性划伤等,进而接触到外界病菌,使真菌乘机而入,引起角膜损伤或病变,对患者视力造成严重影响[1] .

Background: To determine the prevalence of refractive error and ocular biometric data (corneal curvature, axial length, and central corneal thickness) in 6 to 15 years old children of Li and Han ethnicities of China. Methods: This study was a cross-sectional study. A cluster sampling method was used to select 2 nine-year consistent schools in the Ledong and Wanning areas of Hainan Province, with a total of 4,197 students, 3,969 valid data. Eyesight test, slit lamp, autorefraction after cycloplegia, and ocular biometric assessment were performed. The chi-square test and logistic regression analysis was taken as the comparative method. Results: Myopia, hyperopia, and astigmatism are defined as: myopia: SE <=-0.50 D; hyperopia: 0.50 D = 0.75 D, and the uncorrected visual acuity is lower than the lower limit of the normal age for astigmatism. The prevalence of myopia in the 6-9, 10-12, and 13-15 years old were 3.4%, 16.6%, and 36.4% for the Li, while 11.1%, 32.6 %, and 42.6% for the Han. The prevalence of myopia was significantly different between the three age groups (chi(2)=26.809, 48.045, 4.907, P<0.001, P<0.001, P<0.05). The prevalences of myopia in Li boys and girls were 12.3% and 24.2%, and in the Han boys and girls were 26.1% and 36.6%. The prevalence of myopia was different between boys and girls (chi(2)=60.645, 31.137, P<0.001, P<0.001). In the Wanning and Ledong areas, the prevalences of myopia for the Li were 30.5% and 16.8%, and for the Han were 30.8% and 31.1%. In regard to the prevalence of myopia, no statistical difference was seen in the two nationalities in the Wanning area (chi(2)=0.012, 0.914), but not in the Ledong area (chi(2)=27.305, P<0.001). Conclusion: The overall prevalence of myopia in children and adolescents in Han is higher than that in Li The prevalence of myopia in Han and Li was significantly different in different age groups from 6 to 15 years old. The prevalence of myopia in girls was higher than that in boys, in the Wanning area than that in the Ledong area.

Purpose. The purpose of this study was to evaluate the long-term prognosis of small-incision femtosecond laser-assisted intracorneal concave lenticule implantation (SFII) in correction of human keratoconus. Methods. This was a prospective study for 11 patients who received SFII after being diagnosed as progressive keratoconus based on the Amsler–Krumeich classification system. Clinical assessment was performed for all the patients prior to and postsurgically at different time points for 5 years. These included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), biomechanically corrected intraocular pressure (bIOP), corneal topography, anterior segment optical coherence tomography (AS-OCT), confocal microscopy, and biomechanical assessment with Corvis ST. Results. Comparison of preoperative and 60-month postoperative UDVA and CDVA (P60months=0.081 and 0.001, respectively), all eyes showed an improvement in CDVA. Corneal topography showed no significant changes in corneal anterior K1, K2, posterior K1, K2, posterior elevation, or corneal densitometry compared with preoperative levels (P>0.05). Corvis ST showed that central corneal thickness (CCT) and stiffness at applanation 1 (SP-A1) were significantly greater 1 week postsurgically when compared to the baseline (P<0.05) and remained stable thereafter. The lenticule under the AS-OCT remained transparent throughout the entire postsurgical period. Under confocal microscopy, corneal edema and an increase in cell activation and reflectivity were observed at the lenticule-stromal interface within 1 week postoperatively. These reactions gradually subsided with time within 6 months. Conclusion. SFII is an effective procedure to prevent the progression of keratoconus due to its minimal invasiveness and capability of maintaining a steady biometry of the cornea.

Abstract Background To compare the corneal deformation response between patients with keratoconus and healthy subjects and to identify potential characteristics associated with corneal response parameters. Methods This case-control study included a total of 40 keratoconus patients (40 eyes) and 40 age- and sex-matched healthy subjects (40 eyes) whose central corneal thickness (CCT) was less than 500 µm. Pentacam HR and Corvis ST were used to measure the corneal topographies and the corneal deformation response parameters. Results No significant difference was found in the age, sex, laterality distribution, IOP, and CCT between the keratoconus group and healthy controls. The keratoconus eyes had smaller TCT than the healthy controls (p < 0.001), as well as a greater anterior Kmax, posterior Kmax, anterior corneal astigmatism, posterior corneal astigmatism, and posterior maximum elevation (all p < 0.001). The A2l, A2V, and PD were similar between the two groups. The CCR were lower in the keratoconus group, whereas A1L, A1V, and DA were greater in the keratoconus group than in the healthy controls (all P < 0.05). In keratoconus patients, CCR was significantly associated with TCT. A1V was significantly correlated with anterior and posterior corneal astigmatism. Moreover, A2V, CCR, and DA were significantly correlated with posterior maximum elevation. No associations were detected between corneal response parameters and any potential factors in healthy controls. Conclusions Keratoconus eyes showed significant changes in the mechanical properties of the cornea. We hypothesize that local or uneven weakness of the cornea in keratoconus would significantly change all corneal biomechanical properties.