Myopia progression in children during home confinement in the COVID-19 pandemic: A systematic review and meta-analysis

Purpose Myopia is a growing pandemic, especially in children, who risk low vision later in life. Home confinement during the COVID-19 pandemic may have increased myopia progression through increased screentime, decreased time outdoors and increased near work activities. The aim of this study is to compare progression of myopia in children during home confinement period in the COVID-19 pandemic with pre-COVID-19 progression. Methods On January 2023 PubMed, EMBASE and Cochrane were searched for relevant studies. Studies meeting the following criteria were eligible for inclusion: children (under 18 years), home confinement due to COVID-19, spherical equivalent refractive (SER) and axial length (AL) measurements and a follow-up period to measure progression. Quality appraisal was performed by two reviewers independently using the Joanna Briggs Institute tool for cohort studies. Outcomes for myopia were assessed through meta-analysis, analyzing SER (random effects) and AL (fixed effects). Results Hundred and two articles were identified in the search, of which five studies were included in the analysis. Risk of bias is moderate with a few critical flaws in the studies. Myopia progressed more rapidly during the COVID-19 pandemic compared to the pre-COVID-19 period, both in terms of SER (-0.83D [95 %CI, −1.22, −0.43] and AL (0.36 mm [95 %CI, 0.13, 0.39]). Conclusion Progression of myopia during the COVID-19 pandemic accelerated more rapidly compared to the pre-COVID-19 period. Impact of home confinement on myopia may be considered when future lockdown measures are being contemplated. (AU)

Predicting factors for progression of the myopia in the MiSight assessment study Spain (MASS)

Purpose: To investigate which baseline factors are predictive for success in controlling myopia progression in a group of children wearing MiSight Contact Lens (CLs).Methods: Myopic patients (n=41) fitted with MiSight CLs and followed up two years were included in this study. Bivariate analysis, a logistic regression analysis (LG) and a decision tree (DT) approach were used to screen for the factors influencing the success of the treatment. To assess the response, axial length (AL) changes were considered as main variable. Patients were classified based on a specific range of change of axial length at the end of each year of treatment as “responders” (R) (AL change <0.11mm/per year) and “non-responders” (NR) (AL change ≥0.11mm/per year).Results: Of a total of forty-one Caucasian patients treated with MiSight CLs, 21 and 16 were considered responders in the first and the second year of follow-up, respectively. LG analysis showed that the only factor associated with smaller axial length growth was more time spent outdoors (p=0.0079) in the first year of treatment. The decision tree analysis showed that in the responding group spending more than 3 and 4h outdoors per week was associated with the best response in the first year and in the second year of treatment respectively.Conclusions: The LR and the DT approach of this pilot study identifies time spent outdoors as a main factor in controlling axial eye growth in children treated with MiSight CLs. (AU)

Axial length and its associations in the Ural Very Old Study.

To assess the distribution of axial length as surrogate for myopia and its determinants in an old population, we performed the Ural Very Old Study as a population-based cohort study. Out of 1882 eligible individuals aged 85 + years, the Ural Very Old Study performed in an urban and rural region in Bashkortostan/Russia included 1526 (81.1%) individuals undergoing ophthalmological and medical examinations with sonographic axial length measurement. Biometric data were available for 717 (47.0%) individuals with a mean age of 88.0 ± 2.6 years (range 85-98 years; 25%). Mean axial length was 23.1 ± 1.1 mm (range 19.37-28.89 mm). Prevalences of moderate myopia (axial length 24.5-< 26.5 mm) and high myopia (axial length ≥ 26.5 mm) were 47/717 (6.6%; 95% CI 4.7, 8.4) and 10/717 (1.4%; 95% CI 0.5, 2.3), respectively. In multivariable analysis, longer axial length was associated (coefficient of determination r2 0.25) with taller body height (standardized regression coefficient beta:0.16;non-standardized regression coefficient B: 0.02; 95% confidence interval (CI) 0.01, 0.03; P < 0.001), higher level of education (beta: 0.12; B: 0.07; 95% CI 0.02, 0.11; P = 0.002), and lower corneal refractive power (beta: - 0.35; B: - 0.23; 95% CI - 0.28, - 0.18; P < 0.001). Higher prevalence of moderate myopia, however not of high myopia, was associated with higher educational level (OR 1.39; 95% CI 1.09, 1.68; P = 0.007) and lower corneal refractive power (OR 0.77; 95% CI 0.63, 0.94; P = 0.01). In this old study population, prevalence of moderate axial myopia (6.6% versus 9.7%) was lower than, and prevalence of high axial myopia (1.4% versus 1.4%) was similar as, in a corresponding study on a younger population from the same Russian region. Both myopia prevalence rates were higher than in rural Central India (1.5% and 0.4%, respectively). As in other, younger, populations, axial length and moderate myopia prevalence increased with higher educational level, while high myopia prevalence was independent of the educational level.

Eyes grow towards mild hyperopia rather than emmetropia in Chinese preschool children.

PURPOSE: To document one-year changes in refraction and refractive components in preschool children. METHODS: Children, 3-5 years old, in the Jiading District, Shanghai, were followed for one year. At each visit, axial length (AL), refraction under cycloplegia (1% cyclopentolate), spherical dioptres (DS), cylinder dioptres (DC), spherical equivalent refraction (SER) and corneal curvature radius (CR) were measured. RESULTS: The study included 458 right eyes of 458 children. The mean changes in DS, DC and SER were 0.02 ± 0.35 D, -0.02 ± 0.33 D and 0.01 ± 0.37 D, while the mean changes in AL, CR and lens power (LP) were 0.27 ± 0.10 mm, 0.00 ± 0.04 mm and - 0.93 ± 0.49 D. The change in the SER was linearly correlated with the baseline SER (coefficient = -0.147, p < 0.001). When the baseline SER was at 1.05 D (95% CI = 0.21 to 2.16), the change in SER was 0 D. The baseline SER was also linearly associated with the change in LP (coefficient = 0.104, p = 0.013), but not with the change in AL (p = 0.957) or with the change in CR (p = 0.263). CONCLUSION: In eyes with a baseline SER less than +1.00 D, LP loss was higher compared to axial elongation, leading to hyperopic shifts in refraction, whereas for those with baseline SER over this range, loss of LP compared to axial elongation was reduced, leading to myopic shifts. This model indicated the homeostasis of human refraction and explained how refractive development leads to a preferred state of mild hyperopia.

Ocular growth and metabolomics are dependent upon the spectral content of ambient white light.

Myopia results from an excessive axial growth of the eye, causing abnormal projection of remote images in front of the retina. Without adequate interventions, myopia is forecasted to affect 50% of the world population by 2050. Exposure to outdoor light plays a critical role in preventing myopia in children, possibly through the brightness and blue-shifted spectral composition of sunlight, which lacks in artificial indoor lighting. Here, we evaluated the impact of moderate levels of ambient standard white (SW: 233.1 lux, 3900 K) and blue-enriched white (BEW: 223.8 lux, 9700 K) lights on ocular growth and metabolomics in a chicken-model of form-deprivation myopia. Compared to SW light, BEW light decreased aberrant ocular axial elongation and accelerated recovery from form-deprivation. Furthermore, the metabolomic profiles in the vitreous and retinas of recovering form-deprived eyes were distinct from control eyes and were dependent on the spectral content of ambient light. For instance, exposure to BEW light was associated with deep lipid remodeling and metabolic changes related to energy production, cell proliferation, collagen turnover and nitric oxide metabolism. This study provides new insight on light-dependent modulations in ocular growth and metabolomics. If replicable in humans, our findings open new potential avenues for spectrally-tailored light-therapy strategies for myopia.

Cataract surgery contributes to ocular axis growth of aphakic eyes in infants with complex microphthalmos.

To observe the ocular axis, visual acuity and intraocular pressure (IOP) of aphakic eye in infants with congenital cataract and complex microphthalmos after first-stage cataract surgery.This retrospective study included infants with congenital cataract and operated at the Qingdao Eye Hospital between January 2010 and December 2014. The infants were divided into 2 groups: preoperative axial length <18 mm (microphthalmos) or ≥18 mm (controls). Follow-up lasted 24 months; visual acuity, axial length, and IOP were evaluated.There were 28 infants (55 eyes) in the microphthalmos group and 35 (61 eyes) in the control group. The preoperative visual acuity was negative for optokinetic nystagmus, while the postoperative visual acuity was positive for optokinetic nystagmus in both groups. The growth rate was higher in the microphthalmos group (1.4 ±â€Š0.8 vs 0.8 ±â€Š0.4 mm/yr, P < .001 vs controls). The axial length was smaller in the microphthalmos group at all time points compared with the control group (all P < .001). There was no changes in IOP in the microphthalmos group from baseline to 24 months (P = .147), but the IOP was slightly decreased in the control group (P = .015).Cataract surgery may contribute to ocular axis growth in infants with complex microphthalmos.

Globe Axial Length Growth at Age 10.5 Years in the Infant Aphakia Treatment Study.

PURPOSE: To report the change in globe axial length (AL) from the time of unilateral cataract surgery at age 1-7 months to age 10.5 years for infants enrolled in the Infant Aphakia Treatment Study, and to compare AL growth of operated eyes with that of fellow unoperated eyes. DESIGN: Comparative case series. METHODS: AL growth was analyzed relative to treated vs fellow eye, contact lens (CL) vs intraocular lens (IOL), visual acuity (VA) outcome, and the need for surgery for visual axis opacification. Eyes with glaucoma or glaucoma suspect were excluded from the primary analysis but reported separately. RESULTS: Fifty-seven patients have reliable AL data available at both visits. AL was shorter in treated eyes preoperatively (P < .0001) and at 10.5 years of age (P = .021) but AL growth was not different (4.7 mm, P = .99). The growth (70.2% up to age 5 and 29.8% from age 5 to 10.5) was similar in the CL and the IOL group (P = .79). Eyes grew 4.4 mm when visual acuity (VA) was better than 20/200, and 5.2 mm when VA was 20/200 or worse (P = .076). Eyes receiving additional surgery grew more than eyes not receiving additional surgery (P = .052). Patients with glaucoma showed significantly more eye growth (7.3 mm) than those without glaucoma (4.7 mm) and glaucoma suspects (5.1 mm) (P < .05). CONCLUSIONS: Eyes with glaucoma or poor VA often grew longer than the fellow eye. Overall, treated eyes grew similarly in the IOL and CL groups and also kept pace with the growth of the fellow eyes.

Axial Growth and Lens Power Loss at Myopia Onset in Singaporean Children.

Purpose: We studied biometry changes before and after myopia onset in a cohort of Singaporean children. Methods: All data were taken from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). Participants underwent refraction and biometry measurements with a follow-up of 3 to 6 years. The longitudinal ocular biometry (spherical equivalent refraction, axial length, and lens power) changes were compared between children who suffered myopia during the study (N = 303), emmetropic children (N = 490), and children myopic at baseline (N = 509). Results: At myopia onset, the myopic shift increased to 0.50 diopters (D)/y or more in new myopes compared to the minor changes in emmetropes of the same age. New myopes had higher axial growth rates than emmetropes, even years before myopia onset (0.37 and 0.14 mm/y, respectively; ANOVA with Bonferroni post hoc test, P < 0.001). After onset, the change in both parameters slowed down gradually, but significantly (P < 0.05). In new myopes, lens power loss (-0.71 D/y) was significantly higher up to 1 year before myopia onset compared to emmetropes (-0.46 D/y), after which lens power loss slows down rapidly. At age 7 years, (future) new myopes had lens power values close to those of emmetropes (25.12 and 25.23 D, respectively), while later these values approached those of children who were myopic at baseline (23.06 and 22.79 D, respectively, compared to 23.71 D for emmetropes; P < 0.001). Conclusions: New myopes have higher axial growth rates and lens power loss before myopia onset than persistent emmetropes.

A Model to Predict Postoperative Axial Length in Children Undergoing Bilateral Cataract Surgery With Primary Intraocular Lens Implantation.

PURPOSE: To develop a model for predicting postoperative globe axial length (AL) in children undergoing bilateral cataract surgery with primary intraocular lens (IOL) implantation in children older than 2 years. DESIGN: Retrospective case series. METHODS: Children were included only if AL data were available for both eyes before surgery and at least 1 year after surgery. We analyzed variables that could influence globe axial growth and developed a multivariable generalized estimating equation regression model to predict postoperative AL. RESULTS: Sixty-four children were included. The median age at surgery and at follow-up was 5.1 and 12.5 years, respectively. AL measurements were obtained in both eyes during 242 visits. The median AL before and at last follow-up was 22.2 and 23.1 mm, respectively. Beta value for the final model to predict postoperative AL is as below: intercept (1.93), preoperative AL (0.91), age at cataract surgery (-0.07), age at follow-up (0.14), and interaction between age at surgery and age at follow-up (-0.005). Using this model, for a hypothetical patient operated at 2.5 years of age with a 20.5 mm AL would be estimated to have a 22.8 mm AL at 18 years of age. CONCLUSION: IOL power selection is a major challenge of pediatric cataract surgery attributable to unpredictable future eye growth. This model theoretically could be used to predict individual future adult size AL for each child undergoing cataract surgery, helping the surgeon to customize the selection of an IOL power at implantation and also to help the parents understand what to expect.

Growth curves of myopia-related parameters to clinically monitor the refractive development in Chinese schoolchildren.

PURPOSE: To produce a clinical model for the prediction of myopia development based on the creation of percentile curves of axial length in school-aged children from Wuhan in central China. METHODS: Data of 12,554 children (6054 girls and 6500 boys) were collected and analyzed for the generation of the axial length growth curves. A second data set with 226 children and three yearly successive measurements was used to verify the predictive power of the axial length growth percentile curves. Percentile curves were calculated for both gender groups and four age groups (6, 9, 12, and 15 years). The second data set was used to verify the efficacy of identifying the refractive error of the children using the axial length curves, based on their spherical refractive error from the third visit. RESULTS: From 6 to 15 years of age, all percentiles showed a growth trend in axial length, except for the percentiles below the first quartile, which appear to stabilize after the age of 12 (- 0.10; 95%CI, - 0.36-0.16; P = 0.23 for girls; - 0.16; 95%CI, - 0.70-0.39; P = 0.34 for boys); however, the growth continued for the remaining 75% of cases. The second data set showed that the likelihood of suffering high myopia (spherical refractive error ≤- 5.00D) during adolescent years increased when axial length values were above the first quartile, for both genders. CONCLUSIONS: The data from the current study provide a tool to observe the annual growth rates of axial length and can be considered as an approach to predict the refractive development at school ages.

Changes in axial length in accommodative esotropia patients with minimal hyperopic correction.

PURPOSE: To compare the changes of spherical equivalent refractive error (SER) and axial length (AL) for three years in hyperopic children with minimal undercorrection according to the presence of accommodative esotropia (AE). METHODS: A total of 67 hyperopic children were enrolled. The patients were divided into 3 groups and matched by initial age upon examination; esotropic eyes with AE (AE group), fellow eyes with AE (FE group), and right eyes without esotropia (HE group). Changes of SER and AL were serially measured every six months for three years and collected data were compared among the groups. RESULTS: All three groups underwent significant myopic shift and AL elongation during the follow-up period. However, the least amount of change was found in the AE group. The AE group (-0.96 ± 1.38D) exhibited significantly less change in SER compared to the HE group (-1.76 ± 1.11D) and the FE group (-1.57 ± 1.33D) (both p<0.001). Meanwhile, smaller changes of AL were noticeable in the AE group (0.62 ± 0.88mm) compared to the other two groups (HE 0.99 ± 0.29mm; p<0.001, FE 0.73 ± 0.65mm; p = 0.04). The SER and AL changes were not significantly different between the HE group and FE group. CONCLUSIONS: Esotropic eyes with AE patients with minimal undercorrection exhibited little negative shift of SER and AL elongation compared to not only hyperopic eyes without AE but also fellow eyes with AE.

Association of Axial Length Growth and Topographic Change in Orthokeratology.

OBJECTIVES: To investigate the topographic factors related to axial length (AL) growth rate in orthokeratology. METHODS: Clinical data of myopic children with orthokeratology lenses from 2010 to 2016 were investigated. Corneal topography (Orbscan II) and IOLMaster-measured AL at baseline and every posttreatment visit were analyzed. Optical map topographies from baseline- and posttreatment-stabilized corneas were analyzed to calculate the refractive power difference between the apex and the periphery (apex-periphery refractive power difference [ARPD]), which estimates the change of peripheral refraction. A generalized estimating equation (GEE) was used to assess the associations between AL growth and topographic changes in both eyes. RESULTS: The mean baseline spherical equivalent (SE) was -2.40±1.12 diopters (D) and the mean AL was 24.38±0.77 mm. Over a mean follow-up period of 41.9 months, the mean AL growth rate was 0.22±0.15 mm/year. In a univariable GEE analysis, age at initial lens wear, baseline AL, baseline SE, central corneal thickness (CCT), baseline apex power, and posttreatment ARPD on optical topography maps were all significantly correlated with AL growth rate (P<0.001, 0.009, 0.024, 0.011, 0.010, and 0.006, respectively). In a multivariable GEE, CCT and posttreatment ARPD were identified as significant factors (P=0.014 and 0.016, respectively). CONCLUSIONS: The AL growth rate was significantly associated with CCT and posttreatment relative peripheral refractive power, in addition to age at initial lens wear. These associations might possibly demonstrate an effect of treatment-induced peripheral refraction changes on retardation of myopic progression, whereas younger age might significantly influence both AL growth rate and corneal deformation.

[Stabilizing effect of orthokeratology lenses (ten-year follow-up results)]. / Stabiliziruyushchii effekt ortokeratologicheskoi korrektsii miopii (rezul'taty desyatiletnego dinamicheskogo nablyudeniya).

The global prevalence of myopia in adults varies between 20-50% in Europe and the US and 60-90% in Asian countries. According to WHO, myopia is one of the five leading causes of blindness and low vision in the world. Prevention or deceleration of myopia progression is an important public health problem. In recent years, orthokeratology (ortho-k) contact lenses worn at night have been found effective in slowing down the progression of myopia, however, the follow-up period in related studies is no longer than five years. AIM: to investigate the effects of long-term (10 years) overnight wear of ortho-k lenses on the dynamics of axial eye growth in children and adolescents. MATERIAL AND METHODS: This is a prospective cohort study of the effects of ortho-k lenses on the dynamics of anterior-posterior elongation of the eyeball in 84 patients (168 eyes) aged 7 to 16 years and diagnosed with progressive myopia of 1.0 to 7.0 diopters. Patients were examined every three months, including the slit lamp examination to detect possible side effects of lens wear. RESULTS: The study proves the decelerating effect of the method on disease progression: the average 10-year increase in the axial eye length was 0.7±0.02 mm that corresponds to myopia progression of 2.4 diopters. A comparative analysis of the annual axial eye growth depending on patient age and the degree of myopia at baseline was performed. The increase was found to be generally greater in young children with higher initial myopia. CONCLUSION: Long-term wear of orthokeratology lenses is able to slow down the axial eye growth, i.e. the progression of myopia.

[Peripheral refraction: cause or effect of refraction development?] / Perifericheskaya refraktsiya i refraktogenez: prichina ili sledstvie?

AIM: to study peripheral refraction and the shape of the eyeball in children with different clinical refraction. MATERIAL AND METHODS: Using an original method, peripheral refraction was measured at 10-12 degrees temporally and nasally from the fovea in 56 right eyes with different clinical, or axial, refraction of 20 boys and 36 girls aged 7 to 16 years (11.9±1.17 years on average). The shape of the eyeball was judged of by the ratio of its anterior-posterior axial length (AL) to horizontal diameter (HD). RESULTS: The incidence and value of peripheral myopic defocus in children appeared to decrease with clinical refraction increasing from high hyperopia to high myopia. This was the first time, mixed peripheral refraction was found in children, occurring more frequently in higher myopia. This mixed peripheral defocus, shown to be a transitional stage between relative peripheral myopia and relative hyperopia, indicates non-uniform stretching of posterior pole tissues in the course of refraction development and myopia progression. As ocular refraction increases from high hyperopia to high myopia, the growth of AL outpaces that of HD. CONCLUSION: Obviously, natural peripheral defocus results from changes in size and shape of the eyeball in the course of refraction development.

Globe Axial Length Growth at Age 5 Years in the Infant Aphakia Treatment Study.

PURPOSE: To report the longitudinal change in axial length (AL) from the time of unilateral cataract surgery at age 1 to 7 months to age 5 years, and to compare AL growth of operated eyes with that of fellow unoperated eyes. DESIGN: Comparative case series. PARTICIPANTS: Infants enrolled in the Infant Aphakia Treatment Study (IATS). METHODS: The AL at baseline and age 5 years and change in AL were analyzed relative to treated versus fellow eye, visual outcome, and treatment modality (contact lens [CL] vs. intraocular lens [IOL]). Eyes with glaucoma or glaucoma suspect were excluded from primary analysis but reported separately. MAIN OUTCOME MEASURES: The AL growth from preoperative to age 5 years. RESULTS: Seventy patients were eligible; however, AL data for both eyes were available for 64 patients at baseline and 69 patients at age 5 years. The AL was significantly different between treated and fellow eyes preoperatively (18.1 vs. 18.7 mm, P < 0.0001) and at the final follow-up (21.4 vs. 22.1 mm, P = 0.0004). The difference in AL growth between treated and fellow eyes was not significant (3.3 vs. 3.5 mm, P = 0.31). The change in AL in eyes was similar with both treatments (CL 3.2 mm and IOL 3.4 mm, P = 0.53) and did not correlate with visual outcomes (P = 0.85). Eyes receiving additional surgery to clear the visual axis opacification grew significantly more compared with eyes not receiving surgery to clear the visual axis (3.8 vs. 2.7 mm, P = 0.013). Patients with glaucoma showed significantly more eye growth (5.7 mm) than those without glaucoma (3.3 mm) and glaucoma suspects (4.3 mm). CONCLUSIONS: Eyes treated for monocular cataract in infancy have axial growth similar to that of fellow eyes, despite having a shorter AL at the time of surgery. The change in AL in eyes was similar with both treatments (CL and IOL), did not correlate with visual outcomes, and was higher in eyes receiving additional surgery to clear the visual axis or eyes diagnosed with glaucoma.

Axial eye growth and refractive error development can be modified by exposing the peripheral retina to relative myopic or hyperopic defocus.

PURPOSE: Bifocal contact lenses were used to impose hyperopic and myopic defocus on the peripheral retina of marmosets. Eye growth and refractive state were compared with untreated animals and those treated with single-vision or multizone contact lenses from earlier studies. METHODS: Thirty juvenile marmosets wore one of three experimental annular bifocal contact lens designs on their right eyes and a plano contact lens on the left eye as a control for 10 weeks from 70 days of age (10 marmosets/group). The experimental designs had plano center zones (1.5 or 3 mm) and +5 diopters [D] or -5 D in the periphery (referred to as +5 D/1.5 mm, +5 D/3 mm and -5 D/3 mm). We measured the central and peripheral mean spherical refractive error (MSE), vitreous chamber depth (VC), pupil diameter (PD), calculated eye growth, and myopia progression rates prior to and during treatment. The results were compared with age-matched untreated (N=25), single-vision positive (N=19), negative (N=16), and +5/-5 D multizone lens-reared marmosets (N=10). RESULTS: At the end of treatment, animals in the -5 D/3 mm group had larger (P<0.01) and more myopic eyes (P<0.05) than animals in the +5 D/1.5 mm group. There was a dose-dependent relationship between the peripheral treatment zone area and the treatment-induced changes in eye growth and refractive state. Pretreatment ocular growth rates and baseline peripheral refraction accounted for 40% of the induced refraction and axial growth rate changes. CONCLUSIONS: Eye growth and refractive state can be manipulated by altering peripheral retinal defocus. Imposing peripheral hyperopic defocus produces axial myopia, whereas peripheral myopic defocus produces axial hyperopia. The effects are smaller than using single-vision contact lenses that impose full-field defocus, but support the use of bifocal or multifocal contact lenses as an effective treatment for myopia control.

Juvenile eye growth, when completed? An evaluation based on IOL-Master axial length data, cross-sectional and longitudinal.

PURPOSE: To test Sorsby's classical statement of axial eye growth as completed at the age of 13 years, with a view also to differentiating between basic eye growth and juvenile elongation associated with eventual refractive change towards myopia. METHODS: (i) A total of 160 healthy eyes close to emmetropia were included in a cross-sectional set-up (age 4-20 years, 91 males, 69 females), and (ii) 78 longitudinal data sets (67 male and 11 female annual repeat exams over 2-7 years, n=30; age span 4-19 years) were available for evaluating individual axial elongation. The IOL-Master equipment was preferred for conventional ultrasound oculometry due to its extreme repeatability of measuring values, thus making it well fitted for evaluating very small differences. In particular, this had bearing for the decelerating end phase of growth in the longitudinal investigation. RESULTS: Sorby's statement about age 13 as general limit found support from the cross-sectional data, which suggested stable emmetropic eye size from about 11-12 years, with an average apparently outgrown male emmetropic value of 23.5 mm versus females' 22.9 mm. The longitudinal data, however, showed emmetropic growth also beyond this age, with individual data to establish continued axial elongation also at age 13-18 years. The final basic teenage growth is however minute and without practical implications. CONCLUSIONS: Individual ocular growth curves have indicated axial elongation to occur also after the age of 13 years. With regard to the - mainly academic - discrepancy between cross-sectional and longitudinal results, bigger samples are needed, and the juvenile myopic trend has to be acknowledged.

The effect of various levels of stroboscopic illumination on the growth of guinea pig eyes.

BACKGROUND: The aim was to investigate various levels of stroboscopic illumination effect on the growth of guinea pig eyes. METHODS: Thirty-six two-week-old guinea pigs were randomised to one of three treatment groups (n = 12 for each). Two stroboscopic-reared groups were raised with a duty diurnal cycle of 50 per cent at a flash rate of 0.5 Hz. Illumination intensity varied between zero-to-250 lux or zero-to-500 lux during each cycle in each group, respectively. The third control group was exposed to 250 lux illumination. Refraction and biometric measurements were taken for each animal prior to and after two, four, six and eight weeks of treatment. Finally, retinal microstructure was examined. RESULTS: There was significant correlation between refractive errors and axial elongation. After eight weeks of treatment, illumination with flickering light 0-250 lux caused a larger myopic shift with increased axial length than illumination of continuous 250 lux. Stroboscopic illumination with zero-to-500 lux caused a further myopic shift and longer axial length than stroboscopic illumination with zero-to-250 lux. In animals raised in flickering light of zero-to-250 lux or zero-to-500 lux for eight weeks, the outer segment disc membranes in photoreceptor layers were found deformed and detached. CONCLUSION: Chronic exposure to low-frequency temporally modulated illumination-induced histological damage in the retina and induced exaggerated axial length elongation.

Significance of axial length monitoring in children with congenital cataract and update of measurement methods.

Congenital cataract is the main cause of blindness in children, with significantly varying treatment effects. The development of axial length is an important factor that affects the prognosis of these children. However, when compared with the eyes of normal children, the mechanism of growth of the axial length is so complicated that the reported findings differ significantly in terms of the measuring apparatus, assessment methods, and statistical outcome, making the rule of axial length development still unclear. In this paper, we first review the process of axial length development in normal healthy children and compare different hypotheses about certain factors that could affect the development of axial length. The results of some current research about the characteristics of axial length development in congenital cataract children are then reviewed. Lastly, the advantages and disadvantages of current axial length measurements methods are compared and analyzed. The purpose of this review is to improve our understanding of the complexity and importance of axial length development and to suggest better use of axial length monitoring measurements in congenital cataract children for pediatric ophthalmologists, with the hope of offering assistance that will enhance long-term therapeutic effects for these children.

Impact of pupil diameter on axial growth in orthokeratology.

PURPOSE: To compare axial elongation between myopic orthokeratology (OK) contact lens and spectacle wearers, and to investigate the impact of pupil diameter on axial growth in myopic children after OK treatment. METHODS: Fifty-two Chinese children aged 9 to 14 years were enrolled in this study, 27 for the OK group and 25 for the single vision spectacle lenses (SVL) group. Subjects in each group were further divided into two subcategories according to their baseline scotopic pupil diameters. Axial length (AL) was measured at baseline and at every 6-month visit through to 24 months. Linear mixed-effect model was used to determine myopia progression (AL changes from baseline). In this model, repeated visits were taken as within-subject effect, and treatment group as well as pupil size were taken as between-subject effects. The interaction of treatment group*pupil size was analyzed. Relationships between axial growth at 24 months and baseline pupil area were analyzed in both lens groups. RESULTS: Twenty-five subjects in the OK group and 22 subjects in the SVL group completed the 24-month study. AL increased significantly throughout the observed 24-month period (F = 32.09, p < 0.001). Pupil size significantly affected axial growth (F = 15.95, p < 0.001) and different treatment modalities (OK vs. SVL) interacted with the effect of pupil size on axial growth (F = 24.66, p < 0.001). To be more specific, axial growth was significantly slower in subjects with above average pupil sizes than those with below average pupil sizes in the OK group (F = 25.04, p < 0.001). Contrarily, pupil size did not affect axial growth in the SVL group (F = 0.46, p = 0.50). Baseline scotopic pupil area was significantly correlated to axial growth in the OK group (r = 0.405, p < 0.001) but not in the SVL group (r = 0.171, p = 0.056). CONCLUSIONS: Large pupil diameters facilitate the effect of OK to slow axial growth in myopia. We speculate that this is because of enhancement of the myopic shift in the peripheral retina.