Spherical Refraction Research Articles

Refractive changes following yttrium aluminum garnet laser capsulotomy in pseudophakic patients

Purpose To study the effect of neodymium-doped yttrium aluminum garnet (Nd : YAG) laser posterior capsulotomy on refraction and best-corrected visual acuity in pseudophakic eyes. Patients and methods This retrospective nonrandomized analytic study included 110 eyes (n=100 patients) with posterior capsular opacification following a phacoemulsification with foldable hydrophobic intraocular lens implantation surgery. Thorough ophthalmological examinations were performed for all subjects before and after YAG capsulotomy. The best-corrected visual acuity, refractive sphere, and refractive cylinder calculations before and one month after the capsulotomy were recorded. Results Patients’ mean±SD age at the time of surgery was 61.35±14.46 years. The mean±SD refractive sphere changed toward a myopic shift from 0.04±1.78 before capsulotomy to −0.40±1.43 after capsulotomy. The mean±SD refractive cylinder was −1.67±1.45 before capsulotomy and changed to −1.42±1.16 after capsulotomy, making a mild hyperopic shift. Changes in the axis of the cylinder were not statistically significant. A significant improvement was seen in the best-corrected visual acuity from 0.49±0.33 before capsulotomy to 0.23±0.22 after capsulotomy (P<0.001). Conclusion Visual acuity (best-corrected visual acuity) was significantly enhanced following the Nd : YAG laser capsulotomy, and therefore, it is suggested that Nd : YAG laser capsulotomy is a safe and effective alternative treatment for posterior capsular opacification. There are significant changes in the refractive sphere toward a myopic shift following the YAG laser capsulotomy and a significant change in the refractive cylinder toward a hyperopic shift, whereas there were no significant changes in the cylinder axis.

Effects of corneoconjunctival transposition, posterior lamellar keratoplasty and modified deep lamellar endothelial keratoplasty on streak retinoscopy in equine cadaver eyes.

Evaluate the effects of corneoconjunctival transposition (CCT), posterior lamellar keratoplasty (PLK) and modified deep lamellar endothelial keratoplasty (DLEK) on streak retinoscopy in equine cadaver eyes. Intraocular pressure (IOP) was maintained at 25 ± 3 mmHg in 35 equine cadaver eyes. Streak retinoscopy was performed prior to (NO VISCO) and following (VISCO) intracameral injection of 1.0ml of viscoelastic. Following optical coherence tomography (OCT), an axial CCT [n=11] or PLK [n=12], or peripheral DLEK [n=12] was performed. Streak retinoscopy and OCT were repeated postoperatively. Postsurgical net meridional and spherical refraction for CCT [Horizontal (H): 3.4 (95% CI 2.4-4.4) diopters (D), p < .001, Vertical (V): 3.5 (95% CI 2.7-4.4) D, p < .001, Spherical: 3.5 (95% CI 2.6-4.3) D, p < .001] and PLK [H: 3.2 (95% CI 2.2-4.1) D, p < .001, V: 2.8 (95% CI 2.0-3.6) D, p < .001, Spherical: 3.0 (95% CI 2.2-3.8) D, p < .001] were significantly increased from presurgical (VISCO) values. No difference between presurgical (VISCO) and postsurgical values were identified for the DLEK. Postoperative OCT revealed space between anterior and posterior corneal grafts and corneal undulation associated with suture placement. Meridional and spherical refraction had a hyperopic shift following CCT and PLK, with a significantly higher value in the vertical meridian for the CCT. Pre- and postoperative refraction was not significantly different for the DLEK. This supports that the DLEK has a lesser effect on immediate postoperative refraction compared with CCT or PLK.

Comparative analysis of visual quality between unilateral implantation of a trifocal intraocular lens and a rotationally asymmetric refractive multifocal intraocular lens.

To compare visual quality after unilateral cataract surgery with implantation of trifocal intraocular lens (IOL) and asymmetric refractive multifocal IOL. The prospective nonrandom, comparative study consisted of 60 eyes of 60 patients suffering unilateral cataract surgery with implantation of two different IOLs: AT LISA tri 839MP (30 eyes; Carl Zeiss Meditec, Germany) and LS-313 MF30 (30 eyes; Oculentis GmbH, Germany). Visual acuity, refractive outcome, contrast sensitivity, defocus curves, quality of vision, and optical phenomena were evaluated at 3mo postoperatively. There were no statistical differences between groups in uncorrected distance visual acuity (P=0.13) and uncorrected near visual acuity (P=0.54). In contrast, uncorrected intermediate visual acuity was better in trifocal group compared to the refractive multifocal group (P=0.02). No significant statistical between-group difference was detected in cylinder (P=0.43). Compared to trifocal group, spherical refraction and spherical equivalent in refractive multi focal group were more myopic (P<0.01). Under photopic conditions, no significant statistical differences were found between groups in contrast sensitivity at 3 and 6 cycles per degree (cpd). The refractive multifocal group performed better at 12 and 18 cpd than the trifocal group (P=0.01, P=0.034, respectively). The questionnaires of quality of vision and optical phenomena showed no differences between groups. Trifocal IOL is superior to refractive multifocal IOL in intermediate visual acuity. Rotationally asymmetric refractive multifocal IOL is more myopic in automated refraction and significantly better for the photopic contrast sensitivity at high frequency.

Sustained and rebound effect of repeated low-level red-light therapy on myopia control: A 2-year post-trial follow-up study.

To evaluate the long-term efficacy and safety of continued repeated low-level red-light (RLRL) therapy on myopia control over 2 years, and the potential rebound effect after treatment cessation. The Chinese myopic children who originally completed the one-year randomised controlled trial were enrolled. Children continued RLRL-therapy were defined as RLRL-RLRL group, while those who stopped and switched to single-vision spectacle (SVS) in the second year were RLRL-SVS group. Likewise, those who continued to merely wear SVS or received additional RLRL-therapy were SVS-SVS and SVS-RLRL groups, respectively. RLRL-therapy was provided by an at-home desktop light device emitting red-light of 650 nm and was administered for 3min at a time, twice a day and 5 days per week. Changes in axial length (AL) and cycloplegic spherical equivalence refraction (SER) were measured. Among the 199 children who were eligible, 138 (69.3%) children attended the examination and 114 (57.3%) were analysed (SVS-SVS: n=41; SVS-RLRL: n=10; RLRL-SVS: n=52; RLRL-RLRL: n=11). The baseline characteristics were balanced among four groups. In the second year, the mean changes in AL were 0.28 ± 0.14 mm, 0.05 ± 0.24 mm, 0.42 ± 0.20 mm and 0.12 ± 0.16 mm in SVS-SVS, SVS-RLRL, RLRL-SVS and RLRL-RLRL group, respectively (p < 0.001). The respective mean SER changes were -0.54 ± 0.39D, -0.09 ± 0.55D, -0.91 ± 0.48D, and -0.20 ± 0.56D (p < 0.001). Over the 2-year period, axial elongation and SER progression were smallest in RLRL-RLRL group (AL: 0.16 ± 0.37 mm; SER: -0.31 ± 0.79D), followed by SVS-RLRL (AL: 0.44 ± 0.37 mm; SER: -0.96 ± 0.70D), RLRL-SVS (AL: 0.50 ± 0.28 mm; SER: -1.07 ± 0.69D) and SVS-SVS group (AL: 0.64 ± 0.29 mm; SER: -1.24 ± 0.63D). No self-reported adverse events, functional or structural damages were noted. Continued RLRL therapy sustained promising efficacy and safety in slowing myopia progression over 2 years. A modest rebound effect was noted after treatment cessation.

Corneal Epithelium Thickness and Refractive Changes After Myopic Laser Corneal Refractive Surgery

To evaluate the postoperative changes in corneal epithelium thickness and refractive power after femtosecond laser-assisted laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) for myopia correction using anterior segment optical coherence tomography (OCT) with an integrated Placido disc topographer. The VisuMax 500-kHz femtosecond laser (Carl Zeiss Meditec AG) and Amaris 750 excimer laser (SCHWIND eye-tech-solutions) were used. Central, paracentral, and 6-mm epithelial thickness values were obtained, and the change in the value of epithelial thickness was calculated. Changes in the refractive power of the epithelium were also evaluated. The repeatability of this new measurement was also analyzed using the intraclass correlation (ICC). The total follow-up period was 6 months. A total of 77 LASIK eyes were matched with 77 SMILE eyes. Mean spherical equivalent was -3.92 ± 1.67 diopters (D) for LASIK versus -4.02 ± 1.63 D for SMILE (P = .356). Epithelial thickness parameters significantly and equally thickened in both types of surgery. The change in the value of epithelial thickness was positively correlated with spherical aberration. Analysis of the refractive power of the corneal epithelial layer (ICC > 0.70) showed a tendency for the postoperative myopization of the refractive component of this layer (-0.11 D for SMILE and -0.53 D for LASIK at 3 mm) and an increase in its cylinder and aberrometry. Increasing postoperative spherical aberration and epithelial thickness increased myopization of the epithelial refractive sphere (P < .05). Corneal epithelium thickens similarly after LASIK and SMILE, being slightly higher after SMILE. This correlates with the induced spherical aberration. Corneal epithelium thickening induces myopization of its refractive power, which accounts for a slight regression of the net refractive power change on the treated cornea. [J Refract Surg. 2022;38(9):602-608.].

Mathematical Model for Enhancement of Visual Acuity through Electronic System Biofeedback

The majority of people across the world have issues with their vision caused by human ocular refractive errors. Myopia affects 51% of adults, hyperopia affects 38% of adults, and astigmatism affects 27% of adults in the United States. This frequency is much higher in the adult population. 42 percent of global causes of visual impairment are attributable to failure to take prophylactic action against these disorders. This percentage includes presbyopia in adulthood. Visual strain brought on by an excessive use of electronic devices has led to the creation of new techniques and the development of various solutions, including corrective lenses, contact lenses, laser and non-laser refractive surgical operations, and so on. Using a signal electromyography feedback, we describe a technique that may be used to increase a person’s visual acuity. An electronic controlled lens with a power range of -10 to +10 diopters was used in its implementation, along with a LabVIEW interface-connected electromyographic signal gathering equipment. Five separate persons were given the Snellen test to evaluate the proposed system, giving each of them twenty opportunities to complete the exam. Consequently, it is feasible to enhance visual acuity up to 20/20 with an accuracy of 90 percent utilising a biofeedback system, together with other spherical ocular refraction errors such presbyopia, farsightedness, and myopia.

Myopia Control Effect of Repeated Low-Level Red-Light Therapy in Chinese Children: A Randomized, Double-Blind, Controlled Clinical Trial

Repeated low-level red-light (RLRL) therapy is an emerging treatment for myopia control. Nevertheless, previous studies are limited by open-label design. Our study aimed to assess the efficacy and safety of RLRL therapy in controlling myopia progression compared to a sham device with only 10% of the original power. Randomized, double-blind, controlled clinical trial. A total of 112 Chinese children aged 7 to 12 years with myopia of at least -0.50 diopter (D), astigmatism of 1.50 D or less, and anisometropia of 1.50 D or less. Participants were assigned randomly in a 1:1 ratio to the RLRL group or the sham device control group, following a schedule of 3 minutes per session, twice daily, with an interval between sessions of at least 4 hours. The RLRL therapy was provided by a desktop red-light therapy device and administered at home. The sham device was the same device but with only 10% of the original device's power. Cycloplegic refraction and axial length (AL) were measured at baseline and 6 months. Changes in cycloplegic spherical equivalence refraction (SER) and AL between 2 groups were compared using a generalized estimating equation (GEE). A total of 111 children were included in the analysis (n= 56 in the RLRL group and n= 55 in the sham device control group). The mean SER change over 6 months was 0.06 ± 0.30 D in the RLRL group and -0.11 ± 0.33 D in the sham device control group (P= 0.003), with respective mean increases in AL of 0.02 ± 0.11 mm and 0.13 ± 0.10 mm (P < 0.001). In the multivariate GEE models, children in the RLRL group showed less myopia progression and axial elongation than those in the sham device control group (SER: coefficient, 0.167 D; 95% confidence interval [CI], 0.050-0.283 D; P= 0.005; AL: coefficient, -0.101 mm; 95% CI, -0.139 to -0.062 mm; P < 0.001). No treatment-related adverse events were reported. In myopic children, RLRL therapy with 100% power significantly reduced myopia progression over 6 months compared with those treated with a sham device of 10% original power. The RLRL treatment was well tolerated without treatment-related adverse effects.

Refractive Characteristics and Related Factors of Amblyopia after Lamellar Keratoscleroplasty in Children with Limbal Dermoids.

We examined the refractive characteristics and related factors of amblyopia in pediatric patients with limbal dermoids undergoing lamellar keratoscleroplasty. Forty-one children (mean age: 56.15 ± 22.47 months) were enrolled. Cycloplegic refraction, corneal topography, and anterior segment photography were performed. The corneal topographic and distribution characteristics of the refractive state were summarized, and the relationship between limbal dermoid invasion size and the refractive state was analyzed. The relationship between invasion size and amblyopia severity and the effect of clinical intervention at different times on amblyopia treatment were also analyzed. The spherical power distribution was −1.0–+10.75 D (average: +4.79 ± 3.09 D). The cylinder power was −1.25–−8.75 D (average: −4.19 ± 1.93 D). The axial range of astigmatism was 10–180° (average: 103.54 ± 58.16°). Equivalent spherical refraction was −3.88–+7.76 D (average: +2.70 ± 3.08 D). Twenty-five, fifteen, and one case had limboid dermoid invasion of the central circular zone (CCZ), paracentral annular zone (PCZ), and corneal limbus within 1 mm, respectively. Corneal topography of 39 patients showed flat, steep, and mean curvatures of 38.48 ± 2.12 D, 43.29 ± 1.97 D, and 40.70 ± 1.48 D, respectively. The mean astigmatism was 4.80 ± 2.93 D in the 3-mm optical region. Astigmatism was higher in CCZ than in PCZ invasion (p < 0.05). Postoperative visual acuity was positively correlated with patients’ age and amblyopia treatment duration (r = 0.392, p = 0.048; r = 0.488, p = 0.011), and was negatively correlated with astigmatism (r = −0.646, p < 0.001). High hyperopia and astigmatism are the dominant refractive errors in patients with limbal dermoids undergoing lamellar keratoscleroplasty.

A Natural Exposition and Concise Derivation of Geometric Optics Laws by Fermat Principle

With Fermat Principle, that is, the most fundamental principle in geometric optics, it is easy to obtain the three laws of geometric optics as well as the paraxial refraction and catoptric imaging laws. Making use of the principle and a simple mathematical relation, this paper expounds and derives the rectilinear propagation law of rays in the homogeneous medium, the optical reflection and refraction laws as well as the spherical reflection and refraction laws under the paraxial condition. Ulteriorly, with given character rules, the spherical dioptric and catoptric imaging formulas can be generalized into a unified formula separately. The elaboration and derivation in this paper reflect the simplicity of physics and reduce the error probability of complex trigonometric function operation, thus making it more easy for high school students or junior undergraduate and junior college students to accept and understand.

Comparison of triple-DMEK to pseudophakic-DMEK: A cohort study of 95 eyes.

Previous comparative studies show that triple Descemet membrane endothelial keratoplasty (DMEK) (i.e. phacoemulsification followed immediately by DMEK) has either equivalent or better visual outcomes than DMEK in pseudophakic patients. To resolve this discrepancy, a retrospective cohort study was conducted. All consecutive patients with Fuchs Endothelial Corneal Dystrophy who underwent triple or pseudophakic DMEK in 2015-2019 in a tertiary-care hospital (France) and were followed for >12 months were compared in terms of best spectacle-corrected visual acuity (BSCVA), final refractive outcomes, and endothelial-cell loss at 12 months as well as rebubbling rates. The triple-DMEK (40 eyes, 34 patients) and pseudophakic-DMEK (55 eyes, 43 patients) groups were similar in terms of age and other baseline variables. They also did not differ in final BSCVA (both 0.03 logMAR), final endothelial-cell loss (54% vs. 48%), or astigmatism (-1.25 vs. -1 D). At 12 months, triple-DMEK associated with significantly smaller residual hyperopia (0.75 vs. 1 D; p = 0.04) and spherical equivalence (0 vs. 0.5 D; p = 0.02). Triple-DMEK also tended to associate with more frequent rebubbling (40% vs. 24%, p = 0.09). In conclusion, while triple-DMEK and pseudophakic-DMEK achieved similar visual acuity improvement, triple-DMEK was superior in terms of final sphere and spherical refraction but also tended to have higher complication rates.

Study on a plane grating spectral imaging system with smile and keystone eliminated

Subject of study. For a grating-based imaging spectrometer, a method of using an off-axis lens to correct the smile and keystone is proposed and verified by simulation. Method. In the set coordinate system, the ratios of direction cosines of the refractive rays along the y-axis and z-axis are studied using the spatial ray tracing method. On this basis, the smile characteristics of a single refraction sphere and an off-axis lens have been analyzed. In order to verify the theory, a visible spectral imaging system without an off-axis lens and one with an off-axis lens have been optimized, respectively. Main results. The criterion of the smile sign has been given and discussed. For the spectral imaging system without an off-axis lens, good image quality and high spectral resolution have been achieved, which is less than 1 nm. The modulation transfer functions at the wavelengths of 400, 600, and 800 nm are greater than 0.5 at the Nyquist frequency. However, the maximums of the smile and keystone are greater than 0.07 and 0.06 mm, respectively, which are several times the unit size. For the spectral imaging system with an off-axis lens, the image quality is basically the same as the previous one. The obvious differences between the two systems are the smile and keystone. For the latter, the maximums of smile and keystone at all working wavelengths in all fields are close to 6.24 and 6.40 µm, which are less than half of the unit size. Practical significance. The smile and keystone caused by a plane grating can be corrected by an off-axis lens in a plane-grating-based imaging spectrometer, which provides a universal method for the design of a spectral imaging system.

Biometric factors and orthokeratology lens parameters can influence the treatment zone diameter on corneal topography in Corneal Refractive Therapy lens wearers

PurposeTo investigate the relationship between patients’ baseline biometric factors or lens parameters and the diameter of the treatment zone in young myopic children undergoing Corneal Refractive Therapy. MethodsThe data of patients undergoing Corneal Refractive Therapy lens treatment within two years were retrospectively reviewed. Baseline clinical data, including sex, age, refractive power, corneal topography readings, ocular optical biometric measurements, and Corneal Refractive Therapy lens parameters, were subjected to Pearson, Spearman, and partial correlation analyses to identify the potential factors that may influence treatment zone diameter on corneal topography. Logistic and linear regression analyses were used to predict the treatment zone size. ResultsThe Right eyes of 309 patients were included in this study. The spherical refraction, flat keratometric reading, Reverse Zone Depth 2, Landing Zone Angle 1, and lens diameter were independent factors of treatment zone diameter. In the multivariate analyses, Landing Zone Angle 1 was positively correlated, while Reverse Zone Depth 2 and lens diameter were negatively correlated with the size of the treatment area. The accuracy of logistic regression in predicting the treatment zone size was 71.5%. ConclusionAdjustments to Corneal Refractive Therapy lens parameters may influence the treatment zone diameter on corneal topography. A higher Reverse Zone Depth 2, smaller Landing Zone Angle 1, and larger lens diameter can lead to a smaller treatment zone for Corneal Refractive Therapy lens treatment.

Effect of Parental Myopia on Change in Refraction in Shanghai Preschoolers: A 1-Year Prospective Study.

BackgroundTo investigate the risk factors for change in refraction and refractive components in preschoolers.MethodsPreschool children aged 3–5 years old, from the junior and the middle grades of seven randomly selected kindergartens in Jia Ding District, Shanghai, were followed for 1 year. Cycloplegic autorefraction (1% cyclopentolate) and axial length (AL) were measured at baseline and at 1-year follow-up. Questionnaires about parental myopia and environmental risk factors, such as time of outdoors and near work, were collected.ResultsA total of 603 right eyes of 603 children were included. Parental myopia was not associated with a change in refraction, but two myopic parents were associated with a longer change in AL (coefficient = 0.153, p = 0.006), after adjusted for baseline spherical refraction, age, gender, change in height, change in weight, and environment risk factors. In the multivariate analyses, boys showed a more myopic refraction shift than girls in 1 year (coefficient = −0.150, p = 0.008) and a quicker AL elongation (coefficient = 0.120, p = 0.008). Time of near work, such as watching television, using computer, reading and writing, and time of outdoor activities, was not associated with a change in refraction or AL.ConclusionsIn preschool age, environmental risk factors were not strongly associated with the change in refraction or refractive components. Parental myopia influences the refractive development of children continuously from infancy to preschool age, which might be the biological basis of school myopia.

EVALUATION OF STEREOVISION FINDINGS USING THE TITMUS TEST IN CHILDREN AND ADOLESCENTS WITH REFRACTIVE ERRORS

The purpose of the study: to evaluate the indicators of stereovision using the Titmus test for an accurate assessment of stereovision and its correction in children and adolescents. Materials and methods. The study was carried out in 143 patients (286 eyes), including 73 girls (51.0%) and 70 boys (49.9 %). The participants were divided into two groups: the first group involved 6 children with myopia and 11 children with hypermetropia; the second group included 126 people with astigmatism. The second group with astigmatism (252 eyes) included 24 children with myopic astigmatism (19.04 %), 92 children with hypermetropic astigmatism (73.01 %) and 10 people (7.93 %) with mixed astigmatism. All patients of the two groups underwent advanced testing of visual functions that involved a series of the following procedures: visiometry with distance correction, autorefractometry (assessment of spherical refraction and astigmatism using an autorefractometer) before and after cycloplegia, assessment of binocular vision by four-point color test, Worthtest test, (assessment of the nature of vision), heterophoria measurements (cover test), ophthalmoscopy with a dilated pupil (diagnosis of the retina and optic nerve). Results. All 143 patients (286 eyes) were examined by using the Titmus test. The findings obtained showed that gross changes were observed in 14 (5.6 %) patients with astigmatism in the first group and pronounced changes were found in 81 (45.0 %) patients with hypermetropic astigmatism in the second subgroup. In this study, the Titmus test was carried out at medium distances that should be taken into account when assessing stereovision by graded tests. Conclusion. The use of the Titmus test can significantly improve the accuracy of measuring stereovision indicators; it makes screening procedures more comfortable and increases the effectiveness of timely diagnosis of binocular vision disorders. Screening examination of stereovision is promising, as it will significantly improve the quality of screening diagnostics of stereoscopic perception.&#x0D; Overall conclusions show that the Titmus test is reliable and valid, and can be used to improve the accuracy of measuring stereovision, make screening procedures more comfortable and enhance the effectiveness of timely diagnosis of binocular vision disorders. Screening examination of stereospecies is promising as it will significantly improve the quality of eye health monitoring.&#x0D; Prospects for further research imply the development of methods for correcting the most common functional disorders.

Next-Generation Sequencing Screening of 43 Families with Non-Syndromic Early-Onset High Myopia: A Clinical and Genetic Study.

Early-onset high myopia (EoHM) is a disease that causes a spherical refraction error of ≥−6 diopters before 10 years of age, with potential multiple ocular complications. In this article, we report a clinical and genetic study of 43 families with EoHM recruited in our center. A complete ophthalmological evaluation was performed, and a sample of peripheral blood was obtained from proband and family members. DNA was analyzed using a customized next-generation sequencing panel that included 419 genes related to ophthalmological disorders with a suspected genetic cause, and genes related to EoHM pathogenesis. We detected pathogenic and likely pathogenic variants in 23.9% of the families and detected variants of unknown significance in 76.1%. Of these, 5.7% were found in genes related to non-syndromic EoHM, 48.6% in genes associated with inherited retinal dystrophies that can include a syndromic phenotype, and 45.7% in genes that are not directly related to EoHM or retinal dystrophy. We found no candidate genes in 23% of the patients, which suggests that further studies are needed. We propose a systematic genetic analysis for patients with EoHM because it helps with follow-up, prognosis and genetic counseling.

The incidence of myopia and myopic progression from 2019 to 2020 in school-age children in Zhuozhou

Objective: To analyze the changes in refractive status and prevalence of myopia in 6-to 14-year-old children at 2 time points in Zhuozhou, Hebei Province. Methods: In the current cohort study, the visual acuity and refractive status of primary and secondary school students aged 6 to 14 years were examined from June to August 2019 and reexamined from June to August 2020. A total of 30 412 subjects with examination data were enrolled, including 15 861 males (52.2%) and 14 551 females (47.8%), with an average age of (10.0±2.7) years. The participants underwent autorefraction without cycloplegia and a naked eye visual acuity test with a standard logarithmic visual acuity chart. Myopia was screened by the standard of equivalent spherical refraction less than -0.75 diopter (D). The categorical data were analyzed by the Chi-square or Fisher's exact test. Clopper-Pearson was used to estimate the 95% confidence intervals for the incidence of myopia. Results: After the 1-year interval, the change of equivalent spherical refraction was(-0.67±1.11) D and(-0.76±1.11) D, respectively, in male and female participants, and their visual acuity decreased by 0.11±0.19 and 0.12±0.21, respectively. There were significant inter-group differences in the annual change of spherical power in different age groups (χ²=276.23, P<0.001). The naked eye visual acuity reduction was greatest in the 10-year-old students. The incidence of myopia was 42.2% (95% confidence intervals of 41.47% to 42.93%) during the 1-year follow-up period. The incidence of myopia was highest at the age of 14 (52.0% in males and 54.2% in females) and lowest at the age of 6 (31.0% in males and 33.1% in females). Conclusions: The 1-year follow-up revealed an obvious myopic shift in the refractive status of school students in Zhuozhou, with their naked eye visual acuity decreased. The incidence of myopia was higher in females than that in males.

Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus and Early Pellucid Marginal Degeneration.

To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD). It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1week, 2 and 6months. One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5mm zones increased at 1week (both P < 0.001) and then started to decrease up to 6months. However, the corneal irregularity of PMD group had significant reduction only at 1week in 5-mm zone (P = 0.02) and 2months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively. Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

Group-Based Trajectory Modeling to Identify Factors Influencing the Development of Myopia in Patients Receiving Orthokeratology.

PurposeTo analyze the factors influencing the progression of myopia in adolescents receiving orthokeratology.MethodsThis prospective cohort study collected the data of 378 myopia patients receiving orthokeratology. The follow-up time was 12 months ranging from December 2015 to December 2019. The group-based trajectory modeling (GBTM) was used to identify similar developmental trajectories in the levels of uncorrected visual acuity and changes of axial length elongation. Univariate and multivariate logistic regression analyses were conducted to explore the influencing factors of myopia development in patients wearing orthokeratology.ResultsThere was no factor having effect on visual acuity (left) and visual acuity (right) in different trajectories (all P>0.05). The corneal curvature K1 (left) (OR=0.382, 95% CI: 0.188–0.776), corneal curvature K2 (left) (OR=0.362, 95% CI: 0.187–0.699), degree of spherical refraction (left) (OR=0.139, 95% CI: 0.082–0.235) and spherical equivalent (left) (OR=7.276, 95% CI: 3.724–14.215) were factors associated with the changes of axial length elongation (left). The corneal curvature K1 (right) (OR=0.260, 95% CI: 0.116–0.585), corneal curvature K2 (left) (OR=0.272, 95% CI: 0.121–0.610) and degree of spherical refraction (right) (OR=0.129, 95% CI: 0.068–0.244) were correlated with the changes of axial length elongation (right). All P<0.05.ConclusionOrthokeratology is a promising method for controlling the progression of myopia. The corneal curvature, degree of spherical refraction and spherical equivalent were factors influencing the changes of axial length elongation in myopia patients wearing orthokeratology. The findings might give a reference for the application of orthokeratology in clinic.

Delayed Topographical and Refractive Changes Following Corneal Cross-Linking for Keratoconus.

Background: The aim of this study was to analyze the long-term topographic and refractive outcomes of corneal cross-linking (CXL) in keratoconus. Methods: We used a retrospective observational study of patients with keratoconus who underwent CXL with a minimum follow-up of 5 years. Patients’ refractive and topography data (corrected distance visual acuity, sphere, cylinder, average and maximum keratometry, and corneal aberrations) were collected. Results: A total of 112 patients/150 eyes (mean age: 33.2 ± 10.7 years; range: 13–61) were included. The mean follow-up was 5.87 ± 1.35 years (range: 5–10). At the last follow-up visit, an improvement in CDVA, spherical and cylindrical refraction, average and steepest keratometry, and corneal aberrations were observed (p < 0.05), with the exception of trefoil. At the last visit, 49 (34.8%) and 31 (22.0%) eyes had an improvement beyond 1D in their spherical and cylindrical power, respectively, and 43 (28.7%) eyes had a flattening of their steepest keratometry. Progressive improvement over time was observed for spherical refraction; max and mean-K; as well as corneal RMS, total, high, coma, and spherical aberrations (p < 0.05). More severe disease at the baseline correlated with an improvement in corneal aberrations over time. Conclusions: In addition to a progressive improvement in refractive and keratometric indices, corneal aberrations also demonstrate a steady decline with long-term follow-up after CXL, which was more pronounced in more severe patients.

Predictive factors for postoperative visual acuity improvement with ICL-V4c for ultrahigh myopia above - 10 D.

The purpose of this study is to evaluate the predictive factors for postoperative visual acuity improvement (PVAI) in subjects who underwent phakic intraocular lens implantation with a central hole (ICL-V4c) for ultrahigh myopia above - 10 D. This was a retrospective study. Eyes with ultrahigh myopia above - 10 D undergoing ICL-V4c implantation were studied. Univariable linear regression models were used to assess the association between PVAI and preoperative parameters. Myopic maculopathy was classified into 5 categories by fundus photography. After the 1-month follow-up, the PVAI was compared within different age and preoperative spherical degree groups. This study included 726 eyes from 419 patients (111 men and 308 women), and the mean age, spherical refraction, and axial length were 28.67 ± 7.93years, - 13.61 ± 3.44 D, and 28.59 ± 1.50mm, respectively. At baseline, myopic maculopathy was classified (grades C0-C4) as follows: C0 was observed in 200 eyes (27.5%), C1 in 297 eyes (40.9%), C2 in 147 eyes (20.2%), C3 in 22 eyes (3.0%), and C4 in 60 eyes (8.3%). The PVAI was significantly negatively associated with age and positively associated with SD-pre(-Sph), but no significant association between myopic maculopathy classification and axial length was found. After 1month, 417 eyes (57.4%) gained more than 1 line at BCVA, 250 eyes (34.4%) remained the same, and 59 eyes (8.13%) lost 1 line. The postoperative visual acuity of 52 eyes was improved by more than 3 lines, and 42.3% were grade C4. The ICL performed well for the correction of ultrahigh myopia above - 10 D. Younger patients and those with a higher preoperative spherical degree had greater postoperative satisfaction. Chinese Clinical Trial Registry (ChiCTR2000036335). Date of registration: 2020/8/22.