The Genetic Determinants of Axial Length: From Microphthalmia to High Myopia in Childhood.

The axial length of the eye is critical for normal visual function by enabling light to precisely focus on the retina. The mean axial length of the adult human eye is 23.5 mm, but the molecular mechanisms regulating ocular axial length remain poorly understood. Underdevelopment can lead to microphthalmia (defined as a small eye with an axial length of less than 19 mm at 1 year of age or less than 21 mm in adulthood) within the first trimester of pregnancy. However, continued overgrowth can lead to axial high myopia (an enlarged eye with an axial length of 26.5 mm or more) at any age. Both conditions show high genetic and phenotypic heterogeneity associated with significant visual morbidity worldwide. More than 90 genes can contribute to microphthalmia, and several hundred genes are associated with myopia, yet diagnostic yields are low. Crucially, the genetic pathways underpinning the specification of eye size are only now being discovered, with evidence suggesting that shared molecular pathways regulate under- or overgrowth of the eye. Improving our mechanistic understanding of axial length determination will help better inform us of genotype-phenotype correlations in both microphthalmia and myopia, dissect gene-environment interactions in myopia, and develop postnatal therapies that may influence overall eye growth.

Comparative Proteomic Analysis of Aqueous Humor Reveals Biochemical Disparities in the Eyes of High Myopic Patients.

Myopia accounts for a significant proportion of visual lesions worldwide and has the potential to progress toward pathological myopia. This study aims to reveal the difference in protein content in aqueous humor between high myopic and nonhigh myopic patients, as well as better understand the dysregulation of proteins in myopic eyes. Aqueous humor was collected for liquid chromatograph mass spectrometer (LC/MS) analysis from 30 individual eyes that underwent phacoemulsification and intraocular lens (IOL) implantation. Results showed that a total of 190 differentially expressed proteins were identified, which revealed their involvement in cell metabolism, immune and inflammatory response, and system and anatomical structure. Further analysis focused on 15 intensively interacted hub proteins, encompassing functions related to complement cascades, lipoprotein metabolism, and fibrin biological function. Subsequent validations demonstrated elevated levels of APOE (apolipoprotein E), C3 (complement 3), and AHSG (α-2-HS-glycoprotein) in the high myopia group (31 eyes of cataracts and 45 eyes of high myopia with cataracts). AHSG had a significant positive correlation with axial length in high myopic patients, with good efficacy in distinguishing between myopic and nonmyopic groups. AHSG may be a potential indicator of the pathological severity and participator in the pathological progress of high myopia. This study depicted differential expression characteristics of aqueous humor in patients with high myopia and provided optional information for further experimental research on exploring the molecular mechanisms and potential therapeutic targets for high myopia. Data are available via ProteomeXchange with the identifier PXD047584.

Assessing Glaucoma Severity and Progression in Individuals with Asymmetric Axial Length: An Intrapatient Comparative Study.

PURPOSE: To investigate whether a difference exists in intereye glaucoma severity and progression in patients with asymmetric axial length. DESIGN: Long-term observational study. PARTICIPANTS: Patients older than 20 years with a diagnosis of glaucoma at Seoul National University Hospital, Seoul, Korea, between 2010 and 2020. METHODS: Patients with a diagnosis of glaucoma in both eyes with an axial length difference of more than 1.0 mm were included. Each individual's eyes were classified into longer eye and shorter eye, and the baseline and follow-up clinical data were analyzed using the paired T-test and McNemar test. MAIN OUTCOME MEASURES: Differences in clinical characteristics in patients with asymmetric axial length. RESULTS: A total of 190 eyes of 95 patients with glaucoma with asymmetric axial length were included in the study. The patients' mean age was 51.2 ± 12.3 years, and the mean follow-up period was 10.1 ± 3.9 years. No difference was found in baseline intraocular pressure (IOP) or central corneal thickness between longer eyes and shorter eyes. Among the baseline disc parameters, ovality index, ß-zone and γ-zone parapapillary atrophy (PPA) area were larger (P < 0.001) in the longer eyes. In the baseline OCT data, the retinal nerve fiber layer (RNFL) thickness (P = 0.009) and ganglion cell-inner plexiform layer (GCIPL) thickness (P < 0.001) were thinner in the longer eyes. According to a baseline visual field (VF) test, the mean deviation and VF index (VFI) values were significantly lower (P < 0.001, P = 0.034) in the longer eyes. Based on an analysis of glaucoma progression, the rate of change of superior GCIPL (longer eyes, -0.65 µm/year; shorter eyes, -0.40 µm/year), mean deviation (longer eyes, -0.40 dB/year; shorter eyes, -0.21 dB/year), and VFI (longer eyes, -0.92%/year; shorter eyes, -0.46%/year) were larger (P = 0.006, P = 0.005, P < 0.001) in the longer eyes. Additionally, the greater the difference in IOP fluctuation, the greater the difference in the rate of change between mean deviation and VFI. CONCLUSIONS: When an axial length difference of more than 1.0 mm was present, glaucoma tended to be more severe and to progress faster in the longer eyes. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Efficacy of Different Powers of Low-Level Red Light in Children for Myopia Control.

PURPOSE: To compare the efficacy and safety of low-level red light (LRL) in controlling myopia progression at 3 different powers: 0.37 mW, 0.60 mW, and 1.20 mW. DESIGN: Single-center, single-masked, randomized controlled trial. PARTICIPANTS: Two hundred children aged 6-15 with myopia of -0.50 diopter (D) or more and astigmatism of -2.50 D or less were enrolled from April to May 2022. Follow-up ended in December 2022. METHODS: Participants were assigned randomly to 3 intervention groups and 1 control group (1:1:1:1). All participants wore single-vision spectacles. Moreover, the intervention group randomly received LRL at 3 different powers twice daily for 3 minutes per session, with a minimum 4-hour interval. MAIN OUTCOME MEASURES: Changes in spherical equivalent (SE), axial length (AL), and subfoveal choroidal thickness (SFCT) were measured. RESULTS: After 6 months, SE progression was significantly lower in the 0.37-mW group (0.01 D; 95% confidence interval [CI], -0.12 to 0.15), 0.60-mW group (-0.05 D; 95% CI, -0.18 to 0.07), and 1.20-mW group (0.16 D; 95% CI, 0.03 to 0.30) compared to the control group (-0.22 D; 95% CI, -0.50 to 0.30; adjusted P < 0.001 for all). AL changes in the 0.37-mW group (0.04 mm; 95% CI, -0.01 to 0.08), 0.60-mW group (0.00 mm; 95% CI, -0.05 to 0.05), and 1.20-mW group (-0.04 mm; 95% CI, -0.08 to 0.01) were significantly smaller than the control group (0.27 mm; 95% CI, 0.22 to 0.33; adjusted P < 0.001 for all). Similarly, increases in SFCT were significantly greater in the 0.37-mW group (22.63 µm; 95% CI, 12.13 to 33.34 µm), 0.60-mW group (36.17 µm; 95% CI, 24.37 to 48.25 µm), and 1.20-mW group (42.59 µm; 95% CI, 23.43 to 66.24 µm) than the control group (-5.07 µm; 95% CI, -10.32 to -0.13 µm; adjusted P < 0.001 for all). No adverse events were observed. CONCLUSIONS: LRL effectively controlled myopia progression at 0.37 mW, 0.60 mW, and 1.20 mW. Further research is required. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Effect of isoflurane anaesthetic time on ocular a-scan ultrasonography measures and their relationship to age and OCT measures in the Guinea pig.

A-scan ultrasonography enables precise measurement of internal ocular structures. Historically, its use has underpinned fundamental studies of eye development and aberrant eye growth in animal models of myopia; however, the procedure typically requires anaesthesia. Since anaesthesia affects intra-ocular pressure (IOP), we investigated changes in internal ocular structures with isoflurane exposure and compared measurements with those taken in awake animals using optical coherence tomography (OCT). Continuous A-scan ultrasonography was undertaken in tri-coloured guinea pigs aged 21 (n = 5), 90 (n = 5) or 160 (n = 5) days while anaesthetised (up to 36 min) with isoflurane (5% in 1.5L/min O2). Peaks were selected from ultrasound traces corresponding to the boundaries of the cornea, crystalline lens, retina, choroid and sclera. OCT scans (Zeiss Cirrus Photo 800) of the posterior eye layers were taken in 28-day-old animals (n = 19) and compared with ultrasound traces, with choroid and scleral thickness adjusted for the duration of anaesthesia based on the changes modelled in 21-day-old animals. Ultrasound traces recorded sequentially in left and right eyes in 14-day-old animals (n = 30) were compared, with each adjusted for anaesthesia duration. The thickness of the cornea was measured in enucleated eyes (n = 5) using OCT following the application of ultrasound gel (up to 20 min). Retinal thickness was the only ultrasound internal measure unaffected by anaesthesia. All other internal distances rapidly changed and were well fitted by exponential functions (either rise-to-max or decay). After 10 and 20 min of anaesthesia, the thickness of the cornea, crystalline lens and sclera increased by 17.1% and 23.3%, 0.4% and 0.6%, and 5.2% and 6.5% respectively, whilst the anterior chamber, vitreous chamber and choroid decreased by 4.4% and 6.1%, 0.7% and 1.1%, and 10.7% and 11.8% respectively. In enucleated eyes, prolonged contact of the cornea with ultrasound gel resulted in an increase in thickness of 9.3% after 10 min, accounting for approximately half of the expansion observed in live animals. At the back of the eye, ultrasound measurements of the thickness of the retina, choroid and sclera were highly correlated with those from posterior segment OCT images (R2 = 0.92, p = 1.2 × 10-13, R2 = 0.55, p = 4.0 × 10-4, R2 = 0.72, p = 5.0 × 10-6 respectively). Furthermore, ultrasound measures for all ocular components were highly correlated in left and right eyes measured sequentially, when each was adjusted for anaesthetic depth. This study shows that the depth of ocular components can change dramatically with anaesthesia. Researchers should therefore be wary of these concomitant effects and should employ adjustments to better render 'true' values.

Low achromatic contrast sensitivity in birds: a common attribute shared by many phylogenetic orders.

Vision is an important sensory modality in birds, which can outperform other vertebrates in some visual abilities. However, sensitivity to achromatic contrasts - the ability to discern luminance difference between two objects or an object and its background - has been shown to be lower in birds compared with other vertebrates. We conducted a comparative study to evaluate the achromatic contrast sensitivity of 32 bird species from 12 orders using the optocollic reflex technique. We then performed an analysis to test for potential variability in contrast sensitivity depending on the corneal diameter to the axial length ratio, a proxy of the retinal image brightness. To account for potential influences of evolutionary relatedness, we included phylogeny in our analyses. We found a low achromatic contrast sensitivity for all avian species studied compared with other vertebrates (except small mammals), with high variability between species. This variability is partly related to phylogeny but appears to be independent of image brightness.

Comparison of myopic control between orthokeratology contact lenses and defocus incorporated multiple segments spectacle lenses.

Purpose: The purpose of this study was to compare the differences in myopic control effects between orthokeratology (OK) contact lenses and defocus incorporated multiple segments (DIMS) spectacle lenses. Methods: A retrospective cohort study was conducted that included patients who had received OK lens, DIMS spectacle lens or single-vision spectacle treatments. A total of 54 eyes from 27 individuals, 38 eyes from 19 individuals and 42 eyes from 21 individuals were enrolled into the OK lens, DIMS and control groups, respectively. The primary outcomes were the changes in the spherical equivalent refraction (SER) and axial length (AXL) among the groups. A repeated-measure ANCOVA was adopted to calculate the SER progression and AXL elongation of the OK lens group compared with the DIMS group. Results: The difference in the SER progression was clinically non-significant in the OK lens group compared with the DIMS and control groups (P = 0.001). The total AXL elongation results were similar between the OK lens and DIMS groups, but these were lower than in the control group (P = 0.005). The repeated-measure ANCOVA revealed that the SER progression difference during the study interval was clinically non-significant in the OK lens group when compared with the DIMS group (P = 0.028). The AXL elongation results between the OK lens and DIMS populations did not illustrate a significant difference (P = 0.607). In a subgroup analysis of moderate astigmatism, better AXL control was observed in the DIMS subgroup compared with the OK lens subgroup (P = 0.016). Conclusions: The OK lens demonstrated a clinically non-significant effect on the SER and AXL controls compared with the DIMS spectacle lens.

Cylinder power progression associated with axial length in young children: a two-year follow-up study.

PURPOSE: To describe the association of refraction development and axial length (AL) in young children and provide new insights into the progression of cylinder power. METHODS: Children (2-3 grades) were enrolled from primary schools in Shanghai and followed up for two years. Cycloplegic refraction, AL, and corneal curvature radius were measured. Refraction parameters were compared among groups with different AL, AL1 (AL < 23.5 mm), AL2 (23.5 mm ≤ AL < 24.5 mm), and AL3 (AL ≥ 24.5 mm). Multiple regression analysis was used to explore risk factors of diopter of cylinder (DC) progression. RESULTS: In total, out of 6891 enrolled children, 5961 participants (7-11 yrs) were included in the final analysis. Over the two-year period, the cylinder power significantly changed, and those with longer AL had more rapid DC progression over the two years (AL1, -0.09 ± 0.35 D; AL2, -0.15 ± 0.39 D; AL3, -0.29 ± 0.44 D) (P < 0.001). The change in DC was independently associated with AL at baseline (P < 0.001). The proportion of with-the-rule astigmatism increased from 91.3% to 92.1% in AL1 group, from 89.1% to 91.8% in AL2 group and from 87.1% to 92.0% in AL3 group. CONCLUSIONS: Young children with long AL experienced rapid progression of cylinder power. Both the control of myopia progression and attention to the correction of astigmatism are necessary in the health management of children with long AL. The significantly increased AL in participants might contribute to both the extent and direction of astigmatism.

Axial length and pharmacologic pupillary dilation in highly myopic patients.

PURPOSE: To determine how high myopia impacts pharmacological pupillary dilation, and to evaluate the relationship between the extent of pharmacologic pupillary dilation and axial length. METHODS: Patients were grouped into high myopes, defined as one or both eyes having a refractive error greater than - 6 diopters, and controls (between - 2 and + 2 diopters). Dilation was achieved with 1 drop each of tropicamide 1% and phenylephrine 2.5%. Pupil size was measured at full and dim light prior to dilation, then 15 and 30 min after dilation. Biometry was measured for each patient. Statistical analyses were performed using the Mann-Whitney-Wilcoxon tests, two-sample Welch's t-tests, and linear mixed effect models and generalized estimating equations models accounting for inter-eye correlation. RESULTS: Forty patients (20 high myopes and 20 controls, 80 eyes total) participated in the study. High myopes had larger pupils at baseline and achieved significantly greater pupillary size (7.08 mm, 95% CI: 6.97 to 7.19 mm) than controls (6.23 mm, 95% CI: 5.94 to 6.52 mm) after 30 min of dilation (P < .0005). Fully dilated pupil size at 30 min was significantly correlated with both refractive error (r = - 0.57, P < .0005) and axial length (r = 0.47, P < .0005). Generalized estimating equations and linear mixed effect models identified other predictive variables of pupil size after dilation including age and white-to-white diameter. CONCLUSIONS: Highly myopic patients dilate to a larger pupillary size compared to other patients. Predicting dilation based on extent of myopia could facilitate intraocular surgery planning and reduce clinic wait times for myopic patients.

Distribution and associations of anterior lens zonules lengths in patients with cataract.

PURPOSE: To investigate the characteristics and associations of anterior lens zonules lengths in cataract patients via ultrasound biomicroscope (UBM) measurement. METHODS: Patients with age-related cataracts and high myopic cataracts who planned to undergo cataract surgery were included in the study. After routine ophthalmic examinations, the UBM was performed on both eyes to get images of the anterior lens zonules, and Image J software was used to measure the lengths of the lens zonules. Axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WTW) diameter of both eyes were obtained by IOL Master 700. Univariate and multivariate regression analyses were used to assess associated factors of anterior lens zonules lengths. RESULTS: Forty-nine patients with age-related cataracts and 33 patients with high myopic cataracts were enrolled. High myopic cataract patients were younger and had longer anterior lens zonules. Multivariate regression analysis showed that anterior lens zonules lengths were associated with axial lengths (temporal location: ß = 0.036, P = 0.029; nasal location: ß = 0.034, P = 0.011; superior location: ß = 0.046, P = 0.002) and ACD (inferior location: ß = 0.305, P = 0.016) in right eyes. In left eyes, anterior lens zonules lengths were associated with axial lengths (temporal location: ß = 0.028, P = 0.017; inferior location: ß = 0.026, P = 0.016; nasal location: ß = 0.033, P < 0.001) and ACD (inferior location: ß = 0.215, P = 0.030; superior location: ß = 0.290, P = 0.011). CONCLUSIONS: High myopic cataract patients have longer anterior lens zonules. AL and ACD contributed to the lengths of anterior lens zonules. Thus, for patients with long AL and deeper ACD, lens zonules measurement was crucial. CLINICAL TRIAL REGISTRATION: www.chictr.org.cn identifier is ChiCTR2300071397.

Comparison of the axial growth with multifocal and monofocal intraocular lenses in unilateral pediatric cataract surgery.

PURPOSE: To compare axial growth in pediatric cataract patients who underwent multifocal intraocular lens (IOL) implantation without anterior vitrectomy (AV) with that in pediatric patients who underwent monofocal IOL implantation with or without AV. METHODS: Patients who had unilateral pediatric cataracts and underwent surgery at 3-6 years of age from June 6, 2019, to June 30, 2020, at our institution were prospectively analyzed. The patients were categorized into Group A: multifocal IOL implantation with optic capture in Berger's space without AV; Group B: monofocal IOL implantation with optic capture in Berger's space without AV; and Group C: bag-in-the-lens monofocal IOL implantation with AV. Groups A', B' and C' consisted of the fellow eyes from the respective groups. Axial growth and monthly growth rates were compared among the 3 treatment groups, as well as between the treated eyes and the fellow eyes. RESULTS: Thirty-one, 23, and 14 children fulfilling the inclusion criteria, respectively, were included in the final analysis. There were no significant differences in patient age at the time of surgery or preoperative axial length (P > 0.05). After a mean follow-up of 35.57 ± 3.78 months, significant differences in the axial growth and the monthly growth rate were observed (P < 0.05), and Group A had the least axial elongation. Comparing treated eyes with fellow eyes, the amount and rate of axial growth were lower in Group A than in Group A' (P < 0.05), no significant differences were found in Group B (P > 0.05), and Group C had greater growth than did Group C' (P < 0.05). CONCLUSIONS: The implanting multifocal intraocular lenses and maintenance of vitreous body integrity may be protective factors against excessive axial growth in pediatric cataract patients. Clinical trial registration (prospective study): chiCRT1900023155; 2019-05-14.

The effect of axial length on the short-term outcomes of cataract surgery combined with ab interno trabeculotomy.

PURPOSE: Minimally invasive glaucoma surgery is safer and effective surgical modality for patients with glaucoma. To compare the effect of axial length (AL) on the surgical outcomes of combined cataract surgery and ab interno trabeculotomy (phaco-LOT), a retrospective, non-randomized comparative study was performed. METHODS: In total, 458 eyes of 458 open-angle glaucoma patients who underwent phaco-LOT and were followed-up without any intervention for at least 6 months were enrolled. All were divided into a long-AL group (AL ≥ 26.0 mm, 123 eyes) and a not-long-AL group (AL < 26.0 mm, 335 eyes). The principal outcomes were the changes in intraocular pressure (IOP) and medication scores. We also sought a correlation between postoperative IOP spike and hyphema. RESULTS: Significant postoperative reductions in IOP and medication scores were apparent in all subjects. The IOP reductions were significant at all timepoints in the not-long-AL group, but not until 1 month postoperatively in the long-AL group, and the IOP change was significantly lower in the long-AL group from postoperative day 1 to 3 months. On subanalysis of subjects by age, the microhook used, the pre-operative IOP, and the medication score, a significantly higher incidence of IOP spike was observed in the long-AL group in weeks 1 and 2 (both p < 0.05), but this did not correlate with hyphema status, implying that a different mechanism was in play. CONCLUSION: Phaco-LOT was effective regardless of AL, but the postoperative IOP decrease was lower and the early postoperative incidence of IOP spike was higher in long-AL eyes.

Choroidal Control Technology: New Horizons in Maculopathy and Presbyopia.

OBJECTIVE: To evaluate changes in choroidal thickness in presbyopes, when reading with regular glasses versus choroidal control glasses, in patients with or without Age-Related Macular Degeneration (AMD). METHODS: This was a pilot study on short-term axial length (AL) in 33 eyes of 24 presbyopic patients aged 60 to 80 years, assigned to two age-matched groups, with or without AMD. About them, changes in choroidal thickness were evaluated with ocular biometry through indirect measurements of axial length at baseline, after 20' of reading with conventional lenses, and after another 20' of reading with peripheral hyperopic defocus glasses. The differences in axial length between the three different times were analyzed. RESULTS: In presbyopes without AMD there was a significant axial length shortening of -13.44 microns in the first conventional reading period, which was reversed by 90% with hyperopic defocus lenses, recovering + 12.11 microns by axial lengthening (choroidal thinning, p = 0.03). In patients with AMD, axial shortening was significantly greater than controls, -23.86 microns with conventional lenses (p < 0.001) and they, also increased their axial length with defocus, although this response was smaller in proportion (+ 15.52 microns). CONCLUSION: Reading with positive lenses produces myopic defocus and choroidal thickening in presbyopes with and without AMD but was significantly greater in the latter. Glasses with Choroidal Control Technology reduced thickening during reading. KEY MESSAGES: What is known • Presbyopia spectacles for near produce myopic defocus and choroidal thickening. What is new • There are differences in choroidal thickening during reading between normal subjects and those with age related macular degeneration. • Spectacles with Defocus Choroidal Control Technology reduce choroidal thickening during reading in presbyopes.

Cutoff values of axial length/corneal radius ratio for determining myopia vary with age among 3-18 years old children and adolescents.

PURPOSE: To investigate the effectiveness and cutoffs of axial length/corneal radius (AL/CR) ratio for myopia detection in children by age. METHODS: Totally, 21 kindergartens and schools were enrolled. Non-cycloplegic autorefraction (NCAR), axial length (AL), horizontal and vertical meridian of corneal radius (CR1, CR2), and cycloplegic autorefraction were measured. Receiver operating characteristic (ROC) curve was used to obtain the effectiveness and cutoff for myopia detection. RESULTS: Finally, 7803 participants aged 3-18 years with mean AL/CR ratio of 2.99 ± 0.16 were included. Area under the ROC curve (AUC) of AL/CR ratio for myopia detection (0.958 for AL/CR1, 0.956 for AL/CR2, 0.961 for AL/CR) was significantly larger than that of AL (0.919, all P < 0.001), while AUCs of the three were similar with different cutoffs (> 2.98, > 3.05, and > 3.02). When divided by age, the ROC curves of AL/CR ratio in 3- to 5-year-olds showed no significance or low accuracy (AUCs ≤ 0.823) in both genders. In ≥ 6-year-olds, the accuracies were promising (AUCs ≥ 0.883, all P < 0.001), the cutoffs basically increased with age (from > 2.93 in 6-year-olds to > 3.07 in 18-year-olds among girls, and from > 2.96 in 6-year-olds to > 3.07 in 18-year-olds among boys). In addition, boys presented slightly larger cutoffs than girls in all ages except for 16 and 18 years old. For children aged 3-5 years, AL/CR ratio or AL combined with NCAR increased AUC to > 0.900. CONCLUSION: AL/CR ratio provided the best prediction of myopia with age-dependent cutoff values for all but preschool children, and the cutoffs of boys were slightly larger than those of girls. For preschool children, AL/CR ratio or AL combined with NCAR is recommended to achieve satisfactory accuracy. AL/CR ratio calculated by two meridians showed similar predictive power but with different cutoffs.

Accuracy of 14 intraocular lens power calculation formulas in extremely long eyes.

PURPOSE: To compare the accuracy of 14 formulas in calculating intraocular lens (IOL) power in extremely long eyes with axial length (AL) over 30.0 mm. METHODS: In this retrospective study, 211 eyes (211 patients) with ALs > 30.0 mm were successfully treated with cataract surgery without complications. Ocular biometric parameters were obtained from IOLMaster 700. Fourteen formulas were evaluated using the optimized A constants: Barrett Universal II (BUII), Kane, Emmetropia Verifying Optical (EVO) 2.0, PEARL-DGS, T2, SRK/T, Holladay 1, Holladay 2, Haigis and Wang-Koch AL adjusted formulas (SRK/Tmodified-W/K, Holladay 1modified-W/K, Holladay 1NP-modified-W/K, Holladay 2modified-W/K, Holladay 2NP-modified-W/K). The mean prediction error (PE) and standard deviation (SD), mean absolute errors (MAE), median absolute errors (MedAE), and the percentage of prediction errors (PEs) within ± 0.25 D, ± 0.50 D, ± 1.00 D were analyzed. RESULTS: The Kane formula had the smallest MAE (0.43 D) and MedAE (0.34 D). The highest percentage of PE within ± 0.25 D was for EVO 2.0 (37.91%) and the Holladay 1NP-modified-W/K formulas (37.91%). The Kane formula had the highest percentage of PEs in the range of ± 0.50, ± 0.75, ± 1.00, and ± 2.00 D. There was no significant difference in PEs within ± 0.25, ± 0.50 ± 0.75 and ± 1.00 D between BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas (P > .05) by using Cochran's Q test. The Holladay 2modified-W/K formula has the lowest percentage of hyperopic outcomes (29.38%). CONCLUSIONS: The BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas have comparable accuracy for IOL power calculation in eyes with ALs > 30.0 mm.

Lens-induced myopization and body weight in young guinea pigs.

BACKGROUND: To investigate the relationship between body weight and Axial length in guinea pigs. METHODS: Forty pigmented guinea pigs were randomly divided into two groups, namely control group and negative lens-induced myopization (LIM) group. After measuring the baseline axial length and body weight (BW), guinea pigs of LIM group received bilateral negative lens-induced myopization using - 10.0 diopters lenses. One week later, the lenses were removed and biometric and ophthalmoscopic examinations were repeated. RESULTS: Two groups of guinea pigs showed no statistical difference in initial body weight and eye axis length. Compared to the control group, the lens-induced group had a lower weight (P = 0.02) and a longer axial length (P < 0.01) at the end of study Neither at baseline nor at week 1 did AL correlate with BW in both groups (Control Baseline: r = 0.306, P = 0.19; Control Week1: r = 0.333, P = 0.15; LIM Baseline: r=-0.142, P = 0.55; LIM Week 1: r = 0.189, P = 0.42). Lens-induction had a significant effect on axial elongation (P < 0.01) while body weight had no impact on such aspect (P > 0.05). CONCLUSION: In guinea pigs of the same age, axial length was not correlated with body weight. Also, baseline body weight had no impact on natural axial length growth or lens-induced myopia. Lens-induction caused a significant reduction in body weight gain.

Three optical intervention methods for low myopia control in children: a one-year follow-up study.

OBJECTIVE: This study aimed to compare the one-year efficacy of myopia prevention and control using three optical intervention methods - single vision lens (SVL), high aspherical lenticule (HAL), and orthokeratology (OK) lens - in children with low myopia. METHODS: A cohort of 150 children aged 7-13 years with low myopia was recruited and divided into three groups: SVL (n = 50), HAL (n = 50), and OK lens group (n = 50), based on their preference for glasses. Follow-up assessments were carried out over one year, focusing on data from the right eye for statistical analysis. Baseline characteristics such as gender, age, axial length (AL), spherical equivalent refractive error (SER), flat keratometry (K1), steep keratometry (K2), anterior chamber depth (ACD), white-to-white corneal diameter (WTW), and non-contact tonometry (NCT) measurements were gathered and compared among the three groups before any intervention. Changes in AL growth after 1 year of intervention were assessed across the three groups. Subsequently, the AL growth control rates between the HAL and OK lens groups were compared, with the SVL group serving as the reference standard. RESULTS: The study found no statistically significant variances in baseline characteristics (gender, age, SER, AL, K1, K2, WTW, and NCT) among the SVL, HAL, and OK lens groups (all p > 0.05). Following a one-year intervention, AL growth rates were as follows: HAL group (0.163 ± 0.113 mm) < OK lens group (0.280 ± 0.170 mm) < SVL group (0.516 ± 0.190 mm), with statistically significant disparities (p < 0.05). The HAL group demonstrated a higher 1-year AL growth control rate (68.41%) compared to the OK lens group (45.74%) for children aged 7-13 with low myopia, with a statistically significant differences (p < 0.001). And there was significant difference in the SER change between SVL group and HAL group (p < 0.001). CONCLUSION: Compared to SVL, HAL and OK lens are more effective in controlling axial growth in mild myopia. Specifically, HAL maybe shows superior outcomes in both preventive and corrective measures, also it needs to be supported by more studies from randomized controlled experiments.

The effect of cycloplegia in the accuracy of autorefraction, keratometry and axial length using the Myopia Master.

BACKGROUND: Assessing refractive errors under cycloplegia is recommended for paediatric patients; however, this may not always be feasible. In these situations, refraction has to rely on measurements made under active accommodation which may increase measurements variability and error. Therefore, evaluating the accuracy and precision of non-cycloplegic refraction and biometric measurements is clinically relevant. The Myopia Master, a novel instrument combining autorefraction and biometry, is designed for monitoring refractive error and ocular biometry in myopia management. This study assessed its repeatability and agreement for autorefraction and biometric measurements pre- and post-cycloplegia. METHODS: A prospective cross-sectional study evaluated a cohort of 96 paediatric patients that underwent ophthalmologic examination. An optometrist performed two repeated measurements of autorefraction and biometry pre- and post-cycloplegia. Test-retest repeatability (TRT) was assessed as differences between consecutive measurements and agreement as differences between post- and pre-cycloplegia measurements, for spherical equivalent (SE), refractive and keratometric J0/J45 astigmatic components, mean keratometry (Km) and axial length (AL). RESULTS: Cycloplegia significantly improved the SE repeatability (TRT, pre-cyclo: 0.65 D, post-cyclo: 0.31 D). SE measurements were more repeatable in myopes and emmetropes compared to hyperopes. Keratometry (Km) repeatability did not change with cycloplegia (TRT, pre-cyclo: 0.25 D, post-cyclo:0.27 D) and AL repeatability improved marginally (TRT, pre-cyclo: 0.14 mm, post-cyclo: 0.09 mm). Regarding pre- and post-cycloplegia agreement, SE became more positive by + 0.79 D, varying with refractive error. Myopic eyes showed a mean difference of + 0.31 D, while hyperopes differed by + 1.57 D. Mean keratometry, refractive and keratometric J0/J45 and AL showed no clinically significant differences. CONCLUSIONS: Refractive error measurements, using the Myopia Master were 2.5x less precise pre-cycloplegia than post-cycloplegia. Accuracy of pre-cycloplegic refractive error measurements was often larger than the clinically significant threshold (0.25 D) and was refractive error dependent. The higher precision compared to autorefraction measurements, pre- and post-cycloplegia agreement and refractive error independence of AL measurements emphasize the superiority of AL in refractive error monitoring.

Correlation analysis of angles κ and α with the refraction and anterior segment parameters in children.

AIM: To investigate the correlation of angles α and κ with the refractive and biological parameters in children. METHODS: This case-series study included 438 eyes of 219 children (males/females = 105/114, age: 3-15 years). Ocular biometric parameters, including axial length, corneal radius of curvature (CR), white-to-white distance (WTW), angle κ and angle α, were measured using IOL Master 700; auto-refraction were assessed under cycloplegia. The eyes were assigned to different groups based on CR, WTW, and gender to compare the angles α and κ, and analyze the correlations between the differences of biological parameters on angles α and κ. RESULTS: The means of axial length, CR, WTW, angle α, and angle κ were 23.24 ± 1.14 mm, 7.79 ± 0.27 mm, 11.68 ± 0.41 mm, 0.45 ± 0.25 mm, and 0.27 ± 0.22 mm, respectively. Angle α was correlated with CR and WTW (fixed effect coefficient [FEC] = 0.237, p = 0.015; FEC = -0.109, p = 0.003; respectively), and angle κ also correlated with CR and WTW (FEC = 0.271, p = 0.003; FEC = -0.147, p < 0.001, respectively). Comparing subgroups, the large CR and small WTW group had larger angles α (0.49 ± 0.27 vs. 0.41 ± 0.21, p < 0.001; 0.46 ± 0.27 vs. 0.44 ± 0.21, p < 0.05, respectively) and κ (0.29 ± 0.25 vs. 0.24 ± 0.15, p < 0.01; 0.29 ± 0.25 vs. 0.26 ± 0.19, p < 0.05, respectively). The differences in interocular angles α and κ showed correlation with interocular WTW (r = - 0.255, p < 0.001; r = - 0.385, p < 0.001). Eyes with smaller WTW tended to have larger angle κ (0.28 ± 0.27 vs. 0.25 ± 0.15, p < 0.05). CONCLUSION: The size of angle α/κ may be correlated to CR and WTW, and a larger WTW eye may suggest a smaller angle κ compared with the fellow eye.

A retrospective study of cumulative absolute reduction in axial length after photobiomodulation therapy.

BACKGROUND: To assess the age and timeline distribution of ocular axial length shortening among myopic children treated with photobiomodulation therapy in the real world situations. METHODS: Retrospective study of photobiomodulation therapy in Chinese children aged 4 to 13 years old where axial length measurements were recorded and assessed to determine effectiveness at two age groups (4 ∼ 8 years old group and 9 ∼ 13 years old group). Data was collected from myopic children who received photobiomodulation therapy for 6 ∼ 12 months. Effectiveness of myopia control was defined as any follow-up axial length ≤ baseline axial length, confirming a reduction in axial length. Independent t-test was used to compare the effectiveness of the younger group and the older group with SPSS 22.0. RESULTS: 342 myopic children were included with mean age 8.64 ± 2.20 years and baseline mean axial length of 24.41 ± 1.17 mm. There were 85.40%, 46.30%, 71.20% and 58.30% children with axial length shortening recorded at follow-up for 1 month, 3 months, 6 months and 12 months, respectively. With respect to the axial length shortened eyes, the mean axial length difference (standard deviation) was - 0.039 (0.11) mm, -0.032 (0.11) mm, -0.037 (0.12) mm, -0.028 (0.57) mm at 1, 3, 6, and 12-month follow-up, respectively. Greater AL shortening was observed among the older group who had longer baseline axial lengths than the younger group (P < 0.001). CONCLUSIONS: Overall myopia control effectiveness using photobiomodulation therapy was shown to be age and time related, with the maximum absolute reduction in axial elongation being cumulative.