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Background: Myopia is one of the most common eye diseases globally, and has become an increasingly serious health concern among adolescents. Understanding the factors contributing to the onset of myopia and the strategies to slow its progression is critical to reducing its prevalence. Main text: Animal models are key to understanding of the etiology of human diseases. Various experimental animal models have been developed to mimic human myopia, including chickens, rhesus monkeys, marmosets, mice, tree shrews, guinea pigs and zebrafish. Studies using these animal models have provided evidences and perspectives on the regulation of eye growth and refractive development. This review summarizes the characteristics of these models, the induction methods, common indicators of myopia in animal models, and recent findings on the pathogenic mechanism of myopia. Conclusions: Investigations using experimental animal models have provided valuable information and insights into the pathogenic mechanisms of human myopia and its treatment strategies.

The human visual cortex processes light and dark stimuli with ON and OFF pathways that are differently modulated by luminance contrast. We have previously demonstrated that ON cortical pathways have higher contrast sensitivity than OFF cortical pathways and the difference increases with luminance range (defined as the maximum minus minimum luminance in the scene). Here, we demonstrate that these ON-OFF cortical differences are already present in the human retina and that retinal responses measured with electroretinography are more affected by reductions in luminance range than cortical responses measured with electroencephalography. Moreover, we show that ON-OFF pathway differences measured with electroretinography become more pronounced in myopia, a visual disorder that elongates the eye and blurs vision at far distance. We find that, as the eye axial length increases across subjects, ON retinal pathways become less responsive, slower in response latency, less sensitive, and less effective and slower at driving pupil constriction. Based on these results, we conclude that myopia is associated with a deficit in ON pathway function that decreases the ability of the retina to process low contrast and regulate retinal illuminance in bright environments. [ABSTRACT FROM AUTHOR]

Introduction: To evaluate eye growth of children wearing spectacle lenses with highly aspherical lenslets (HAL), slightly aspherical lenslets (SAL) and single‐vision lenses (SVL) compared to eye growth patterns in non‐myopes in Wenzhou, China. Methods: The randomised trial had 170 myopic children (aged 8–13 years) randomly assigned to the HAL, SAL or SVL group. Normal eye growth was examined using 700 non‐myopic schoolchildren (aged 7–9 years) in the Wenzhou Medical University‐Essilor Progression and Onset of Myopia (WEPrOM) cohort study using logistic function models. Slow, normal and fast eye growth was defined as range of values <25th, 25th–75th and >75th percentiles, respectively. Results: The predicted upper limits of slow eye growth (25th percentile) among non‐myopes aged 7–10 years and 11–13 years were 0.20–0.13 and 0.08–0.01 mm (after 2‐year period; 0.37–0.33 and 0.29–0.14 mm), respectively, while the upper limits of normal eye growth (75th percentile) were 0.32–0.31 and 0.28–0.10 mm (after 2‐year period; 0.58–0.55 and 0.50–0.24 mm), respectively. The 2‐year trial had 157 children, 96 of whom wore their lenses full time (everyday ≥12 h/day). The mean 2‐year axial length change for HAL, SAL and SVL was 0.34, 0.51 and 0.69 mm (0.28, 0.46 and 0.69 mm in full‐time wear), respectively. Slow eye growth was found in 35%, 17% and 2% (44%, 29% and 3% in full‐time wear); normal eye growth in 35%, 26% and 12% (44%, 32% and 9% in full‐time wear) and fast eye growth in 30%, 57% and 86% (12%, 39% and 88% in full‐time wear), respectively (p < 0.001). Conclusions: The eye growth pattern in approximately 90% wearing HAL full time (compared with about 10% wearing SVL full time) was similar or slower than that of non‐myopic children both after 1‐ and 2‐year periods. [ABSTRACT FROM AUTHOR]

Purpose: To compare axial length (AL) growth curves in East Asian (EA) and non‐EA emmetropes. Methods: A meta‐regression of 28 studies with emmetrope‐specific AL data (measured with optical biometry) was performed. Emmetropia was defined as spherical equivalent refraction (SER) between −0.50 and +1.25 D, determined under cycloplegia if the mean age was ≤20 years. The AL growth curve (mean AL vs. mean age) was first fitted to the full dataset using a weighted nonlinear mixed‐effects model, before refitting the model with ethnicity as a two‐level grouping variable (EA vs. non‐EA). Ethnic differences in growth curve parameters were tested using the Wald test. Results: A total of 3331 EA and 1071 non‐EA emmetropes (mean age: 6.5–23.1 years) were included. There was no evidence of an ethnic difference in either final AL (difference: 0.15 mm, 95% CI: −0.04 to 0.35 mm, p = 0.15) or initial AL, as represented by the amount that the final AL needed to be offset to obtain the y‐intercept (difference: −2.77 mm, 95% CI: −10.97 to 5.44, p = 0.51). Likewise, AL growth rate (curve steepness) did not differ between ethnic groups (difference: 0.09, 95% CI: −0.13 to 0.31, p = 0.43). Collectively, AL growth rate decreased from 0.24 mm/year at 6 years of age to around 0.05 mm/year at 11 years of age, after which it dipped below the repeatability of optical biometry (±0.04 mm) and practically plateaued around 16 years of age (final AL: 23.60 mm). Conclusions: EA and non‐EA emmetropes have comparable AL growth curves. [ABSTRACT FROM AUTHOR]

Myopia is a refractive anomaly that occurs when there is a discrepancy between the axial length of the eyeball and the refractive power of the cornea and lens. Myopia is a global challenge, the incidence of which is constantly increasing. Nowadays, over 30% of the world's population is myopic - in Europe every young person (25- 29 years old), in East Asia over 80%. It is estimated that by 2050, the number of people with myopia will reach about 5 billion people. In recent years, a number of organizations have conducted studies related to myopia and its growth. Undercorrection has been shown to increase myopia. At this stage, both pharmacological (atropine) and optical methods are used to control myopia - bifocal and progressive glasses, multifocal contact lenses. The goal of modern optical methods is to create a "peripheral myopic defocus" that reduces the growth of the eyeball. Orthokeratology is another method that has demonstrated successful results in myopia control. During the period of May 2022 – May 2023 In an eye center in the city of Varna, a study was conducted to examine different methods of controlling myopia and to track its progression. The subjects of the study were 50 children between the ages of 10 and 16, diagnosed with myopia. A detailed medical history was taken from the patients and a detailed ophthalmological examination was performed, including autorefractometry, refraction, cycloplegia under the supervision of an ophthalmologist. After accurate determination of the refraction, 10 of the patients were fitted with monofocals (SV), 10 with PALS lenses, 10 with DIMS lenses, 10 with HALT lenses, and the remaining 10 with contact lenses, and after 6 months, all of them were called for a follow-up examination. After the control examinations, it was found that 55% (22 children) out of a total of 80% (40 children) with myopia control were affected by the placed means and slowed down the progression compared to those with monofocals. It has been proven that the growth of myopia can be influenced and controlled by various means according to the individual needs of the patient. The prevalence of myopia in children is increasing worldwide and is considered a major public health problem. This increase has sparked interest in research into the prevention and control of myopia in children. Research conducted over the last decade has shown and established the need and success of the methods used to control myopia. The use of dioptric lenses for spectacles with peripheral defocus, soft multifocal lenses with a distant design, orthokeratology and pharmacological agents (atropine drops) have proven to be practically applicable. Their successful impact on limiting myopia will continue to be investigated and innovative methods will be sought for their application in clinical practice. Future studies with a more detailed analysis of visual changes and in collaboration with industry will lead to the refinement of this type of vision correction device. [ABSTRACT FROM AUTHOR]

Purpose: Although there are many reports on ocular growth, these data are often fragmented into separate parameters or for limited age ranges. This work intends to create an overview of normal eye growth (i.e., in absence of myopisation) for the period before birth until 18 years of age. Methods: The data for this analysis were taken from a search of six literature databases using keywords such as "[Parameter] & [age group]", with [Parameter] the ocular parameter under study and [age group] an indication of age. This yielded 34,409 references that, after screening of title, abstract and text, left 294 references with usable data. Where possible, additional parameters were calculated, such as the Bennett crystalline lens power, whole eye power and axial power. Results: There were 3422 average values for 17 parameters, calculated over a combined total of 679,398 individually measured or calculated values. The age‐related change in refractive error was best fitted by a sum of four exponentials (r2 = 0.58), while all other biometric parameters could be fitted well by a sum of two exponentials and a linear term ('bi‐exponential function'; r2 range: 0.64–0.99). The first exponential of the bi‐exponential fits typically reached 95% of its end value before 18 months, suggesting that these reached genetically pre‐programmed passive growth. The second exponentials reached this point between 4 years of age for the anterior curvature and well past adulthood for most lenticular dimensions, suggesting that this part represents the active control underlying emmetropisation. The ocular components each have different growth rates, but growth rate changes occur simultaneously at first and then act independently after birth. Conclusions: Most biometric parameters grow according to a bi‐exponential pattern associated with passive and actively modulated eye growth. This may form an interesting reference to understand myopisation. [ABSTRACT FROM AUTHOR]

This study aims to explore the role of GABAB receptors in the development of deprivation myopia (DM), lens-induced myopia (LIM) and lens-induced hyperopia (LIH). Chicks were intravitreally injected with 25 µg baclofen (GABABR agonist) in one eye and saline into the fellow eye. Choroidal thickness (ChT) was measured via OCT before and 2, 4, 6, 8, 24 h after injection. ChT decreased strongly at 6 and 8 h after baclofen injection and returned back to baseline level after 24 h. Moreover, chicks were monocularly treated with translucent diffusers, −7D or +7D lenses and randomly assigned to baclofen or saline treatment. DM chicks were injected daily into both eyes, while LIM and LIH chicks were monocularly injected into the lens-wearing eyes, for 4 days. Refractive error, axial length and ChT were measured before and after treatment. Dopamine and its metabolites were analyzed via HPLC. Baclofen significantly reduced the myopic shift and eye growth in DM and LIM eyes. However, it did not change ChT compared to respective saline-injected eyes. On the other hand, baclofen inhibited the hyperopic shift and choroidal thickening in LIH eyes. All the baclofen-injected eyes showed significantly lower vitreal DOPAC content. Since GABA is an inhibitory ubiquitous neurotransmitter, interfering with its signaling affects spatial retinal processing and therefore refractive error development with both diffusers and lenses. [ABSTRACT FROM AUTHOR]

Purpose: It has previously been found that imposing positive defocus changes axial length and choroidal thickness after only 30 min. In the present study, we investigated whether these changes may result from an altered choroidal blood flow. Methods: Eighteen young adult subjects watched a movie from a large screen (65 in.) in a dark room at 2 m distance. A 15-min wash-out period was followed by 30 min of watching the movie with a monocular positive defocus (+ 2.5D). Changes in axial length and ocular blood flow were measured before and after the defocus, by using low-coherent interferometer (LS 900, Haag-Streit, Switzerland) and a laser speckle flowgraphy (LSFG) RetFlow unit (Nidek Co., LTD, Japan), respectively. Three regions were analyzed: (1) the macular area, where choroidal blood flow can be measured, (2) the optic nerve head (ONH), and (3) retinal vessel segments. Results: Changes in choroidal blood flow were significantly and negatively correlated with changes in axial length that followed positive defocus in exposed eyes (R = − 0.67, p < 0.01). The absolute values of changes in choroidal blood flow in the defocused eyes were significantly larger than in the fellow control eyes (2.35 ± 2.16 AU vs. 1.37 ± 1.44 AU, respectively, p < 0.05). ONH and retinal blood flow were not associated with the induced changes in axial length. Conclusions: Positive defocus selectively alters choroidal, but not retinal or ONH blood flow in young human subjects after short-term visual exposure. The results suggest that blood flow modulation is involved in the mechanism of choroidal responses to optical defocus. [ABSTRACT FROM AUTHOR]

Studies in animal models and humans have shown that refractive state is optimized during postnatal development by a closed-loop negative feedback system that uses retinal image defocus as an error signal, a mechanism called emmetropization. The sensor to detect defocus and its sign resides in the retina itself. The retina and/or the retinal pigment epithelium (RPE) presumably releases biochemical messengers to change choroidal thickness and modulate the growth rates of the underlying sclera. A central question arises: if emmetropization operates as a closed-loop system, why does it not stop myopia development? Recent experiments in young human subjects have shown that (1) the emmetropic retina can perfectly distinguish between real positive defocus and simulated defocus, and trigger transient axial eye shortening or elongation, respectively. (2) Strikingly, the myopic retina has reduced ability to inhibit eye growth when positive defocus is imposed. (3) The bi-directional response of the emmetropic retina is elicited with low spatial frequency information below 8 cyc/deg, which makes it unlikely that optical higher-order aberrations play a role. (4) The retinal mechanism for the detection of the sign of defocus involves a comparison of defocus blur in the blue (S-cone) and red end of the spectrum (L + M−cones) but, again, the myopic retina is not responsive, at least not in short-term experiments. This suggests that it cannot fully trigger the inhibitory arm of the emmetropization feedback loop. As a result, with an open feedback loop, myopia development becomes "open-loop". [ABSTRACT FROM AUTHOR]

This study aims to explore the role of GABAB receptors in the development of deprivation myopia (DM), lens-induced myopia (LIM) and lens-induced hyperopia (LIH). Chicks were intravitreally injected with 25 µg baclofen (GABABR agonist) in one eye and saline into the fellow eye. Choroidal thickness (ChT) was measured via OCT before and 2, 4, 6, 8, 24 h after injection. ChT decreased strongly at 6 and 8 h after baclofen injection and returned back to baseline level after 24 h. Moreover, chicks were monocularly treated with translucent diffusers, −7D or +7D lenses and randomly assigned to baclofen or saline treatment. DM chicks were injected daily into both eyes, while LIM and LIH chicks were monocularly injected into the lens-wearing eyes, for 4 days. Refractive error, axial length and ChT were measured before and after treatment. Dopamine and its metabolites were analyzed via HPLC. Baclofen significantly reduced the myopic shift and eye growth in DM and LIM eyes. However, it did not change ChT compared to respective saline-injected eyes. On the other hand, baclofen inhibited the hyperopic shift and choroidal thickening in LIH eyes. All the baclofen-injected eyes showed significantly lower vitreal DOPAC content. Since GABA is an inhibitory ubiquitous neurotransmitter, interfering with its signaling affects spatial retinal processing and therefore refractive error development with both diffusers and lenses.

In pediatric ophthalmology it is often necessary to obtain axial length in young children. For children older than 3 years, noncontact biometry can be used. For younger children this is usually not an option, and the clinician needs to rely on other imaging modalities. Depicted data curves in textbooks elaborate on few studies and limited number of subjects. The existing literature regarding normal axial length for preterm infants and term newborns is summarized and critically appraised for number of subjects, relevance, measurement method and error, gender and retinopathy of prematurity. We obtained axial length measurements for a total number of 6,575 eyes in 27 papers published from 1964 to 2018 (9 papers with 2,272 eyes for preterm children, 24 papers with 4,303 eyes for term children). Initially, axial length increases rapidly: from a mean 5.1–16.2 mm in week 12 to week 37 gestational age. From 38 weeks, growth rate decreases from 16.2 mm to a mean of 21.8 mm at 3 years old. Male infants have a larger average axial length than females at birth; the difference is 0.24 mm (95%CI: 0.15–0.33, P < 0.001). We present a useful growth curve and formula that may serve as a reference for diagnosing abnormal growth. [ABSTRACT FROM AUTHOR]

Background: Myopia is one of the most common eye diseases globally, and has become an increasingly serious health concern among adolescents. Understanding the factors contributing to the onset of myopia and the strategies to slow its progression is critical to reducing its prevalence., Main Text: Animal models are key to understanding of the etiology of human diseases. Various experimental animal models have been developed to mimic human myopia, including chickens, rhesus monkeys, marmosets, mice, tree shrews, guinea pigs and zebrafish. Studies using these animal models have provided evidences and perspectives on the regulation of eye growth and refractive development. This review summarizes the characteristics of these models, the induction methods, common indicators of myopia in animal models, and recent findings on the pathogenic mechanism of myopia., Conclusions: Investigations using experimental animal models have provided valuable information and insights into the pathogenic mechanisms of human myopia and its treatment strategies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

In the regulation of ocular growth, scleral events critically determine eye size and thus the refractive status of the eye. Increased scleral matrix remodeling can lead to exaggerated eye growth causing myopia and additionally increased risk of ocular pathological complications. Thus, therapies targeting these changes in sclera hold potential to limit such complications since sclera represents a relatively safe and accessible drug target. Understanding the scleral molecular mechanisms underlying ocular growth is essential to identifying plausible therapeutic targets in the sclera. This section provides a brief update on molecular studies that pertain to the sclera in the context of ocular growth regulation and myopia.

Evidence from animal and human studies suggests that ocular growth is influenced by visual experience. Reduced retinal image quality and imposed optical defocus result in predictable changes in axial eye growth. Higher order aberrations are optical imperfections of the eye that alter retinal image quality despite optimal correction of spherical defocus and astigmatism. Since higher order aberrations reduce retinal image quality and produce variations in optical vergence across the entrance pupil of the eye, they may provide optical signals that contribute to the regulation and modulation of eye growth and refractive error development. The magnitude and type of higher order aberrations vary with age, refractive error, and during near work and accommodation. Furthermore, distinctive changes in higher order aberrations occur with various myopia control treatments, including atropine, near addition spectacle lenses, orthokeratology and soft multifocal and dual-focus contact lenses. Several plausible mechanisms have been proposed by which higher order aberrations may influence axial eye growth, the development of refractive error, and the treatment effect of myopia control interventions. Future studies of higher order aberrations, particularly during childhood, accommodation, and treatment with myopia control interventions are required to further our understanding of their potential role in refractive error development and eye growth. [ABSTRACT FROM AUTHOR]

Myopia will affect half the global population by 2050 and is a leading cause of vision impairment. High-dose atropine slows myopia progression but with undesirable side-effects. Low-dose atropine is an alternative. We report the effects of 0.01% or 0.005% atropine eye drops on myopia progression in 13 Australian children aged between 2 and 18 years and observed for 2 years without and up to 5 years (mean 2.8 years) with treatment. Prior to treatment, myopia progression was either ‘slow’ (more positive than −0.5 D/year; mean −0.19 D/year) or ‘fast’ (more negative than −0.5 D/year; mean −1.01 D/year). Atropine reduced myopic progression rates (slow: −0.07 D/year, fast: −0.25 D/year, combined: before: −0.74, during: −0.18 D/year, p = 0.03). Rebound occurred in 3/4 eyes that ceased atropine. Atropine halved axial growth in the ‘Slow’ group relative to an age-matched model of untreated myopes (0.098 vs. 0.196 mm/year, p < 0.001) but was double that in emmetropes (0.051 mm/year, p < 0.01). Atropine did not slow axial growth in ‘fast’ progressors compared to the age-matched untreated myope model (0.265 vs. 0.245 mm/year, p = 0.754, Power = 0.8). Adverse effects (69% of patients) included dilated pupils (6/13) more common in children with blue eyes (5/7, p = 0.04). Low-dose atropine could not remove initial myopia offsets suggesting treatment should commence in at-risk children as young as possible.

Clinical studies and basic research have attempted to establish a relationship between myopia progression and single vision spectacle wear, albeit with unclear results. Single vision spectacle lenses are continuously used as the control group in myopia control trials. Hence, it is a matter of high relevance to investigate further whether they yield any shift on the refractive state, which could have been masked by being used as a control. In this review, eye development in relation to eyes fully corrected versus those under-corrected is discussed, and new guidelines are provided for the analysis of structural eye changes due to optical treatments. These guidelines are tested and optimised, while ethical implications are revisited. This newly described methodology can be translated to larger clinical trials, finally exerting the real effect of full correction via single vision spectacle lens wear on eye growth and myopia progression.

Emmetropization is controlled by the defocus in the retinal image. It is a classical problem how changes in focus, introduced by accommodation, are taken into account. We have quantified accommodation errors in chickens wearing negative lenses to find out whether they can predict subsequent eye growth. Two groups of chicks, aged 10 to 13 days, wore lenses (-7D) monocularly for 4-7 days. Fellow eyes remained untreated. Vitreous chamber depth (VCD) was measured in alert hand-held chickens with high resolution, using the Lenstar LS 900 (Haag-Streit, Koeniz, Switzerland). Non-cycloplegic refractive state was measured by automated infrared photoretinoscopy with and without the lenses in place. In group 1 (n = 6), measurements were done 5 times a day to obtain detailed VCD growth curves. In group 2 (n = 10), measurements were only taken twice, at 9 am and 4 pm, to reduce the risk of recovery from induced myopia due to the frequent removal of the lenses. As expected from the negative power of the lenses, refractions measured through the lenses were more hyperopic although not as much as predicted by the lens powers, indicating that chickens partially refocused their eyes by accommodation. Among different animals, accommodation errors varied from 1.1 ± 0.9 to 3.6 ± 1.1D (group 1, mean ± 1 standard deviation) and 0.22 ± 1.25 to 1.72 ± 1.23D (group 2). No correlations were found between the magnitude of the accommodation errors in individual animals and subsequent changes in VCD. With negative lenses, VCD grew both during day and night while fellow eyes grew only during the day but shrank during the night. In conclusion, accommodation errors did not predict future eye growth. This raises the question as to why brief periods of clear vision, when lenses are taken off, have a strong inhibitory effect on myopia development while periods of clear vision due to accommodation have apparently no effect. A possible explanation is that, in addition to retina-driven control of eye growth, there is a second neural pathway for the control of eye growth that carries the signal of accommodation - although it is striking that no neuronal and structural correlate has been identified to date. [ABSTRACT FROM AUTHOR]

Little is known about the development of vision in wild birds. It is unknown, for example, whether the ability to see can be predicted by the level of prenatal growth or whether the eyes are open at hatching in a particular species. In this study, we investigated the growth of eyes, the formation of retinal ganglion cell topography, and the appearance of simple, visually guided behaviours in chicks of a small procellariiform seabird, Leach's storm petrel (Oceanodroma leucorhoa). This semi-precocial species, which has a well-developed sense of smell, nests in underground burrows where adults provision chicks for 6-8 weeks in the dark before fledging. Retinal ganglion cell topographic maps revealed that fine-tuning of cell distribution does not happen early in development, but rather that the ganglion cell layer continues to mature throughout provisioning and probably even after fledging. While the olfactory bulbs reached adult size around 7 weeks after hatching, the eyes and telencephalon continued to grow. Optokinetic head response and artificial burrow finding experiments indicated that chicks in the 2nd week after hatching lack even the most basic visually guided behaviours and are probably blind. Thus, vision in Leach's storm petrel chicks starts to function sometime around the 3rd week after hatching, well after the eyes have opened and the olfactory system is functional. [ABSTRACT FROM AUTHOR]

We investigated the potential causal relationships between anisometropia, amblyopia and strabismus, specifically to determine whether either amblyopia or strabismus interfered with emmetropization. We analyzed data from non-human primates that were relevant to the co-existence of anisometropia, amblyopia and strabismus in children. We relied on interocular comparisons of spatial vision and refractive development in animals reared with 1) monocular form deprivation; 2) anisometropia optically imposed by either contact lenses or spectacle lenses; 3) organic amblyopia produced by laser ablation of the fovea; and 4) strabismus that was either optically imposed with prisms or produced by either surgical or pharmacological manipulation of the extraocular muscles. Hyperopic anisometropia imposed early in life produced amblyopia in a dose-dependent manner. However, when potential methodological confounds were taken into account, there was no support for the hypothesis that the presence of amblyopia interferes with emmetropization or promotes hyperopia or that the degree of image degradation determines the direction of eye growth. To the contrary, there was strong evidence that amblyopic eyes were able to detect the presence of a refractive error and alter ocular growth to eliminate the ametropia. On the other hand, early onset strabismus, both optically and surgically imposed, disrupted the emmetropization process producing anisometropia. In surgical strabismus, the deviating eyes were typically more hyperopic than their fellow fixating eyes. The results show that early hyperopic anisometropia is a significant risk factor for amblyopia. Early esotropia can trigger the onset of both anisometropia and amblyopia. However, amblyopia, in isolation, does not pose a significant risk for the development of hyperopia or anisometropia. [ABSTRACT FROM AUTHOR]

INTRODUCTION Ultrasound has an important role in the diagnostics of the posterior segment of the eye, when clinical examination is not possible. One of problems is congenital cataract. Using ultrasound biometry it is possible to measure the axial length of the eye in all ages and axial growth from the very beginning to its termination. OBJECTIVE To ratify growth of the infant’s eye with and without congenital cataract, and to determine the accuracy of ultrasound measuring with and without general anesthesia. METHOD In our study we analyzed 30 patients (48 eyes) who had congenital cataract in one or both eyes (observed group) and 20 patients (40 eyes) in whom no eye disease was diagnosed (control group). RESULTS The observed group of 30 patients (48 eyes) with congenital cataract was divided according to age into three subgroups: I) 4-12 months, 11 patients, 18 eyes; II) 13-24 months, 7 patients, 11 eyes; III) 25-36 months, 12 patients, 19 eyes. In control group we analyzed 20 patients (40 eyes) without congenital cataract. These patients were also divided, according to age, into three subgroups: I) 2-12 months, 5 patients, 10 eyes; II) 13-24 months, 6 patients, 12 eyes; III) 25-36 months, 9 patients, 18 eyes. CONCLUSION Comparing the average axial lengths of the eye in the first, second and third year of life between the observed and control groups, we did not find any statistical significance in the obtained values. When determining the accuracy of the ultrasound measuring of the axial length of the eye in the observed group, we found no statistical significance between the determined values weather the measurements were done with or without general anesthesia (p>0.05).

However complex a visual system is, the size (and growth rate) of all its components-lens, retina and nervous system-must be precisely tuned to each other for the system to be functional. As organisms grow, their eyes must be able to achieve and maintain emmetropia, a state in which photoreceptors receive sharp images of objects that are at infinity. While there has been ample research into how vertebrates coordinate eyes growth, this has never been addressed in arthropods with camera eyes, which tend to grow dramatically and typically in a step-wise manner with each molt (ecdysis). Here, we used histological and optical methods to measure how the larval eyes of Sunburst Diving Beetles ( Thermonectus marmoratus, Coleoptera, Dytiscidae) grow, and how well optical and morphological parameters match, during the dramatic growth that occurs between two consecutive larval stages. We find that the eye tubes of the principal eyes of T. marmoratus grow substantially around molt, with the vitreous-like crystalline cone contributing the most to the overall growth. Lenses also reform relatively quickly, undergoing a period of dysfunction and then regaining the ability to project sharp images onto the retina around 8 h post-molt. [ABSTRACT FROM AUTHOR]

Background: In all species studied, myopia develops if the eye is deprived of detailed vision during development (form deprivation myopia). However, different degrees of spatial image deprivation produce different effects and have not been described in the mammalian eye. Therefore, the effect of image degradation on guinea pig emmetropisation was investigated.Methods: Eighty-one guinea pigs wore a treatment on one eye from 6 to 13 days of age. There were four treatments: a translucent diffuser (no lines or edges were visible through the diffuser); one of five Bangerter foils (BF: 0.8, 0.6, 0.4, 0.2, light perception only), which differed in their cut-off spatial frequencies; a 'ring mount' control with no filter; or one of two neutral density filters that reduced luminance only (ND, optical density grades 0.1 and 0.6). Refractive error and ocular elongation were measured after seven days of treatment.Results: The extent of induced myopia and ocular growth were related to the amount of image degradation (mean difference between the treated and untreated eyes changed in a graded manner -7.0 D to -0.2 D and from 85 µm to seven µm respectively, for spatial frequency cut-offs between zero and 24 cycles per degree). Corresponding reductions in luminance from ND filters did not increase eye growth and caused significantly less myopia than the BFs that caused a similar luminance decrement. The greatest myopia occurred when no or limited spatial information was available to the eye, but moderate myopia still occurred with spatial frequency cut-offs of six and 12 cycles per degree, well beyond the visual acuity range of guinea pigs.Conclusion: Excessive ocular growth and myopia are most robust when induced by spatial frequency reductions within the visual acuity range but can also be induced beyond this. Either the mechanism of ocular growth can detect supra-threshold spatial frequencies, possibly due to aliasing, or it is sensitive to small amounts of contrast degradation. [ABSTRACT FROM AUTHOR]