Form deprivation myopia in adolescent monkeys.

BACKGROUND: Early in life, at ages corresponding to the rapid infantile phase of ocular growth in humans, visual feedback can modulate refractive development in monkeys and many other species. To determine if vision-dependent mechanisms can still influence refractive development in primates during the slow juvenile phase of ocular growth, the time period when myopia typically develops in human children, we examined the effects of form deprivation on adolescent monkeys. METHODS: Unilateral, form deprivation was produced in four rhesus monkeys by surgically fusing the eyelids of one eye. The onset of deprivation was between 3.7 and 5 years of age, which corresponds to onset ages between approximately 15 and 20 human years. The ocular effects of form deprivation were assessed by cycloplegic retinoscopy and A-scan ultrasonography. RESULTS: At the onset of form deprivation all four monkeys were isometropic and the axial dimensions in the two eyes were well matched. After 71 to 80 weeks of form deprivation, all of the deprived eyes had become relatively more myopic than their fellow non-treated eyes (mean anisometropia = -2.03 +/- 0.78 D) and they exhibited relative increases in vitreous chamber depth (mean = 0.55 +/- 0.31 mm) and axial length (mean = 0.49 +/- 0.35 mm). DISCUSSION: Our results demonstrate that vision-dependent mechanisms can influence ocular growth and refractive development in "teenage" monkeys. These results raise the possibility that visual experience may be involved in the genesis of school-age myopia in children.     

眼外伤致形觉剥夺与近视

：探讨人类是否存在形觉剥夺性近视现象。方法：回顾性分析眼外伤5例的屈光度及眼轴情况。结果：5例眼外伤所致形觉剥夺患者眼均存在高度近视，而健眼正常。结论：人类也存在形觉剥夺性近视。     

Form deprivation myopia: elastic properties of sclera

Thinning of the posterior sclera may imply that stretching and/or weakening of the sclera plays a role in axial elongation of myopic eyes. We investigated the elastic stress-strain properties of sclera from developing tree shrew eyes made myopic by monocular deprivation (MD) of form vision. Five days of MD induced a relative myopia (mean ± SEM) of −5.6 D ± 0.6 D (retinoscopy) and a vitreous chamber elongation (deprived minus control) of 106 ± 14 μm, n = 10 (ultrasonography). Posterior scleral test samples (2 mm wide) cut from myopic eyes were significantly thinner than their contralateral eye controls (149 ± 4 μm versus 164 ± 4 μm, n = 10, P < 0.01) when measured with a force-controlled micrometer. However, posterior sclera from control eyes was significantly thicker than that from age-matched normal eyes (164 ± 4 μm versus 149 ± 3μm, n = 10, P < 0.01). Under uniaxial tension, posterior scleral samples from myopic eyes failed at 18% lower load (162 g versus 198 g) and extended approximately 25% more than controls at a load corresponding to 20 mm Hg intraocular pressure. These differences were largely accounted for by the differences in scleral thickness. Finite element modelling of tree shrew eyes using the material properties summarised above, implies that simple elastic stretching of the sclera accounts for less than 20% of the observed difference in axial length between myopic and contralateral control eyes.     

C57BL/6小鼠形觉剥夺性近视动物模型的建立

目的 探讨C57BL/6小鼠形觉剥夺性近视与眼球生物学参数的变化,揭示小鼠实验性近视形成的敏感期,以及形觉剥夺对小鼠屈光发育的影响.方法 实验研究.23日龄C57BL/6小鼠74只,随机分为3组,单眼形觉剥夺组:剥夺2周(n=12)、3周(n=20)和4周(n=18),对侧眼作为自身对照;形觉剥夺恢复组(n=10):单眼形觉剥夺4周,分别恢复4 d和7 d;正常对照组(n=14).实验前后分别用红外偏心摄影验光仪测量小鼠眼球的屈光状态,修正过的人眼角膜曲率计测量角膜曲率半径,相干光断层扫描仪测量眼球生物学参数,包括眼前节、晶状体厚度、玻璃体腔深度和眼轴长度等.对组内实验眼和对侧眼的屈光力、角膜曲率半径、眼球参数的比较采用配对t检验,不同组间比较采用独立样本t检验进行统计学分析.结果 形觉剥夺2周,实验眼相比对侧眼向近视方向漂移(-0.85±1.65)D,眼球各生物学参数未见明显改变;形觉剥夺3周,实验眼相比对照眼向近视方向漂移(-4.27±1.60)D(t=-1.72,P=0.095);形觉剥夺4周组,实验眼相比对侧眼向近视方向漂移(-5.27±1.28)D(t=-2.64,P<0.05)并伴玻璃体腔深度延长(27±13)μm和眼轴长度增加(28±12)μm;上除眼罩7 d,实验性近视完全恢复.结论 小鼠单眼形觉剥夺4周可诱导出相对近视,但诱导时间较其他近视动物模型长;去除眼罩7 d,实验性近视完全恢复;利用相干光断层扫描仪测最小鼠眼球生物学参数可以较好反映屈光度的改变.     

Effect of monocular deprivation on NMDAR1 immunostaining in ocular dominance columns of the marmoset Callithrix jacchus

We previously showed that immunoreactivity to N-Methyl-D-aspartate (NMDA) receptors in primary visual cortex of Callithrix jacchus is regulated by visual activity during the second and third postnatal months (Fonta et al., 1997). The purpose of the present study was to show that the columnar pattern of high and low NMDAR1 immunoreactivity observed in monocularly deprived animals corresponds to ocular dominance columns linked to the nondeprived and deprived eye, respectively. We compared cortical distribution of NMDAR1 receptors and the projection zones of thalamic afferents, revealed by transneuronal transport of tritiated proline, in 2-month-old, either monocularly deprived or control, marmosets. The data show that ocular dominance columns exist in 2-month-old marmosets and that a 2-week monocular deprivation by means of eyelid suture leads to a modification of the thalamo-cortical afferents organization. Experiments of neuronal tracing and immunohistochemistry performed on the same animals demonstrated that cortical domains with decreased NMDAR1 level correspond to the deprived eye columns. These investigations, coupled to the previous results, strongly suggest that the NMDA receptors, regulated by visual activity, are involved in the refining of ocular dominance columns in the primary visual cortex of juvenile marmoset.     

Decreased proteoglycan synthesis associated with form deprivation myopia in mature primate eyes

PURPOSE: The rate of proteoglycan synthesis was measured in the scleras of adolescent marmosets that had undergone monocular form deprivation to characterize the scleral extracellular matrix changes associated with the development of myopia in a mature primate. METHODS: Form deprivation myopia was induced in adolescent marmosets by unilateral lid suture for an average of 108 days. After the lids were reopened, the axial lengths and refractions were measured at intervals for up to 39 weeks. At the end of the study period, sclera were isolated and immediately radiolabeled with 35SO4 in organ culture. Proteoglycan synthesis rates were determined by measurement of 35SO4 incorporation into cetylpyridinium chloride-precipitable glycosaminoglycans after digestion of the scleral samples with proteinase K. Collagen content was determined by measurement of total hydroxyproline in scleral digests. Newly synthesized proteoglycans were separated on a Sepharose CL-4B molecular sieve column and identified by their core proteins by Western blot analyses. RESULTS: Lid suture resulted in myopia due to a significant increase in vitreous chamber depth. After Sepharose CL-4B chromatography, newly synthesized scleral proteoglycans isolated from normal, form-deprived, and contralateral control eyes, resolved into one major peak that eluted in the position of decorin, a small chondroitin-dermatan sulfate proteoglycan. After digestion of the major peak with chondroitinase ABC, an approximately 45-kDa core protein was detected by Western blot analyses, confirming the presence of decorin. Form deprivation resulted in a significant reduction in the rate of proteoglycan synthesis in the posterior sclera (-43.55%, P < or = 0.001). Proteoglycan synthesis was also significantly reduced in the posterior sclera of form-deprived eyes relative to total collagen content (-36.19%, P < or = 0.01) and was negatively correlated with the rate of vitreous chamber elongation in the deprived eye (r2 = 0.779, P < or = 0.05). CONCLUSIONS: Significant extracellular matrix remodeling occurs in the posterior sclera of the adolescent primate eye during vitreous chamber elongation and myopia development. The negative correlation between vitreous chamber elongation rates and the synthesis rates of decorin in form-deprived eyes suggests that proteoglycan synthesis within the posterior sclera plays a role in the regulation of ocular size and refraction in the adolescent marmoset.     

Accommodation and induced myopia in marmosets

Accommodation may indirectly influence visually guided eye growth by affecting the retinal defocus signal used to guide growth. Specifically, increased lags of accommodation associated with low stimulus-response (S-R) function slopes will impose increased hyperopic blur on the retina and may induce axial elongation and myopia. The purpose of this study was (1) to measure accommodation in awake, free viewing marmosets and (2) compare accommodation behavior in marmosets before and after inducing different amounts of myopia with binocular spectacle lenses. In untreated marmosets, the average accommodation S-R slope approached one, but showed considerable inter-individual variability (mean+/-SD: 0.964+/-0.249 for monocular viewing; 0.895+/-0.235 for binocular viewing; monocular and binocular measures not significantly different). The monocular S-R slopes were significantly reduced following a period of lens rearing that produced axial myopia (change in slope=-0.30+/-0.30, p<.01) and the reduction in slope was proportional to the amount of myopia induced (p<.01). The S-R slopes measured either under monocular or binocular conditions before induction of myopia were not well correlated with the degree of myopia induced (monocular: r=-.240, p=.453; binocular: r=-.060, p=.824). These results support the hypothesis that the reduction in S-R slope in myopes is a consequence of the myopia induced. The alternative hypothesis-that low S-R slope increases susceptibility to the development of myopia--is not supported by the weak correlation between the pre-manipulation S-R slopes and the magnitude of the myopic shift.     

The relationship between cone pigments and behavioural sensitivity in a New World monkey (Callithrix jacchus jacchus).

Microspectrophotometric measurements of visual pigments and behavioural measurements of spectral sensitivity are reported for individual marmosets from 3 family groups. The sex differences and polymorphism that characterise the long-wave cone pigments in this species are well reflected by variations in the behavioural sensitivities. With one exception, the pattern of inheritance is compatible with a genetic model in which the long-wave pigment is specified by a single polymorphic locus on the X-chromosome. Measurements are also reported for the spectral absorbance of the marmoset lens, and these are used to reconstruct short-wave behavioural sensitivity from the microspectrophotometric measurements of the short-wave cones.     

Intraretinal axon diameters of a New World primate, the marmoset (Callithrix jacchus)

Purpose : Previously, measurements of retinal ganglion cell axon diameter have been used to make inferences about the physiology and clinical pathology of the visual pathway. However, few of these studies were able to unequivocally relate axon diameter to retinal ganglion cell type and other associated measurements. In this and our previous study we have examined intraretinal axon diameters to determine if differences in axon diameter may help to explain conduction velocity measurements found previously. Methods : Individual retinal ganglion cells of a New World primate, the common marmoset (Callithrix jacchus) were injected iontophoretically with 2% Lucifer yellow and 4% neurobiotin. Labelled cells were visualized by horseradish peroxidase immunohistochemistry and diaminobenzidine and then retinae were mounted vitreal side up on a glass slide. Cell measurements were made with the aid of a camera lucida attachment and computer‐aided morphometry. Axons were photographed under ×100 oil immersion and measured at a final magnification of ×4600. Results : A sample of 62 parasol cells, 22 midget cells, 16 hedge cells and 11 small bistratified cells were analysed. Dendritic field diameter of the different cell classes showed only moderate (non‐significant) increases with eccentricity. Only the parasol cells demonstrated a significant increase in mean axon diameter with eccentricity. When the parasol class was examined more closely, it was found that only parasol cells of the superior, inferior and temporal retina (SIT group) showed significant positive correlations between different cell parameters (mean axon diameter, soma diameter, dendritic field diameter, eccentricity). Soma and dendritic field diameters of the SIT group were significantly larger than those of the nasal parasol cells. However, mean axon diameters of the SIT cells were not significantly different from nasal parasol cells. Axon diameters of nasal parasol cells were very variable and overlapped those of the midget and hedge cell classes to a large extent. Conclusions : The present data show that for marmoset parasol cells there may not be a clearly defined distinction between nasal and superior, inferior and temporal parasol cells on the basis of axon size. Of particular interest in the present analysis is the clear separation of superior, inferior and temporal parasol cells and nasal parasol cells when comparing soma and dendritic field diameters which is not reflected in the distribution of axon diameters. We suggest that changes in diameter along the length of an axon, differences between retinal quadrants and the variability between cells may be related to minimization of spatiotemporal dispersion necessary for accurate perception of motion within the visual world.     

鸡眼形觉剥夺性近视模型的实验研究

目的 建立鸡眼形觉剥夺性近视（FDM）模型,观察复方珍珠水解液（MPHS）药物防治近视的疗效。方法 建立FDM模型,艾维茵仔鸡左眼鼻侧贴上半透明新月形1／2眼睑眼罩,造成1／2眼球形觉剥夺;采用A超,测定双眼眼内结构;KR7100型电脑自动验光仪测量各组双眼屈光度;采用非接触式阿贝比长仪测定各眼球外径;正位照片测量赤道8个半径。通过眼球形态学、屈光学比较FDM模型组与各组间的差异。结果 模型组比正常组眼球外径扩大。玻璃体腔扩张为113％;眼内轴长增大至108％;8个赤道半径扩大,差异呈显著性（P＜0．05－0．001）。屈光度增加－2．087D;而MPHS药品则显著抑制了眼球形态学的扩张;抑制负性屈光度的增长。结论 （1）FDM模型眼球的各种测量结果均证实模型建立成功,玻璃体腔明显扩张至130％,眼内轴长延长至108％,通过8个赤道半径测量全面扩大。（2）MPHS具有抑制眼球外径、内径及赤道半径扩张的作用。     

First order connections of the visual sector of the thalamic reticular nucleus in marmoset monkeys (Callithrix jacchus)

The thalamic reticular nucleus (TRN) supplies an important inhibitory input to the dorsal thalamus. Previous studies in non-primate mammals have suggested that the visual sector of the TRN has a lateral division, which has connections with first-order (primary) sensory thalamic and cortical areas, and a medial division, which has connections with higher-order (association) thalamic and cortical areas. However, the question whether the primate TRN is segregated in the same manner is controversial. Here, we investigated the connections of the TRN in a New World primate, the marmoset (Callithrix jacchus). The topography of labeled cells and terminals was analyzed following iontophoretic injections of tracers into the primary visual cortex (V1) or the dorsal lateral geniculate nucleus (LGNd). The results show that rostroventral TRN, adjacent to the LGNd, is primarily connected with primary visual areas, while the most caudal parts of the TRN are associated with higher order visual thalamic areas. A small region of the TRN near the caudal pole of the LGNd (foveal representation) contains connections where first (lateral TRN) and higher order visual areas (medial TRN) overlap. Reciprocal connections between LGNd and TRN are topographically organized, so that a series of rostrocaudal injections within the LGNd labeled cells and terminals in the TRN in a pattern shaped like rostrocaudal overlapping "fish scales." We propose that the dorsal areas of the TRN, adjacent to the top of the LGNd, represent the lower visual field (connected with medial LGNd), and the more ventral parts of the TRN contain a map representing the upper visual field (connected with lateral LGNd).     

Distribution of the alpha1 subunit of the GABA(A) receptor on midget and parasol ganglion cells in the retina of the common marmoset Callithrix jacchus

The inhibitory neurotransmitter gamma aminobutyric acid (GABA) has been shown to influence the responses of ganglion cells in the mammalian retina. Consistently, GABA(A) receptor subunits have been localized to different ganglion cell types. In this study, the distribution of the alpha1 subunit of the GABA(A) receptor on the dendrites of midget and parasol ganglion cells was investigated quantitatively in the retina of a New World monkey, the marmoset. Ganglion cells were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the alpha1 subunit of the GABA(A) receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells of both ganglion cell types. On average, parasol cells show a slight increase in the spatial density of immunoreactive puncta with distance from the soma, whereas the density of immunoreactive puncta on midget cells stays even. Parasol ganglion cells show a slightly higher average density of immunoreactive puncta (0.083 puncta/microm dendrite) than midget cells (0.054 puncta/microm dendrite).     

Ocular dominance columns in the adult New World Monkey Callithrix jacchus

In the marmoset Callithrix jacchus, ocular dominance columns (ODC) have been reported to be present in young animals, but absent in adults (Spatz, 1989). We have studied in juvenile and adult animals the postnatal organization of the retino-geniculo-cortical afferents by means of transneuronal labeling. We show in the present work that ODC are present in the primary visual cortex of Callithrix jacchus, both in the adult and in the juvenile animal. The present work confirms the presence of ODC in the visual cortex of juvenile marmoset before the end of the first postnatal month. In 2-month-old animals, ODC are well demarcated in IVcalpha and IVcbeta. In the adult marmosets, the present data clearly show that the primary visual cortex is also organized with ODC. In horizontal sections, they form a mosaic through the ventral and dorsal calcarine cortex and through the dorso-lateral occipital part of the striate cortex. In frontal sections, their presence is manifest in IVcbeta within the calcarine cortex and they only faintly appear in IVcalpha. These new findings are important since they underline the usefulness of the adult New World Monkeys as a model in visual research.     

Normal development of refractive state and ocular component dimensions in the marmoset (Callithrix jacchus).

Refractive state and ocular dimensions were studied longitudinally in nine normal marmosets. Animals were anaesthetised and examined (with some exceptions) at 4, 6, 7, 8, 10, 15, 24 and 39 weeks of age. Cycloplegic retinoscopy showed that hyperopia early in life rapidly diminished. Refraction corrected for the artefact of retinoscopy stabilised by 8 weeks of age, but at a slightly myopic value, rather than at emmetropia. The ocular components continued to change throughout the period studied. Corneal radius, measured by photokeratometry, increased slightly during development. Anterior segment depth and vitreous chamber depth (VCD), measured by A-scan ultrasonography, increased throughout development while lens thickness initially increased and then decreased. Data from the eyes of these normal animals were compared with that from the contralateral eyes of animals which received short periods of monocular deprivation early in life (Troilo, D., & Judge S.J. (1993). Ocular development and visual deprivation myopia in the common marmoset (Callithrix jacchus jacchus). Vision Research, 33, 1311-24); eyes which viewed through no lens or a plano lens (Graham, B. & Judge, S.J. (1999)). The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus). Vision Research, 39, 189-206), and eyes of normal animals in another colony. There were no significant differences between the first two groups and the normal animals in our colony while age-matched animals from the other colony were slightly but significantly less myopic than our animals.     

形觉剥夺在儿童近视中的表达

目的:通过调查处于生长发育期的儿童由于各种原因的形觉剥夺会否造成双眼在近视发生、发展中的不一致,从临床层面上证实形觉剥夺性近视,揭示近视发病的环境因素和机制,从而采取有效措施进行防治。方法:抽取门诊近视患儿114例,均常规行视力、眼位、主导眼、眼底、裂隙灯、规范的散瞳检影等检查,并通过问诊了解家族史及是否存在剥夺因素。比较双眼的视力、屈光度,并就形觉剥夺眼与屈光度的高低进行相关性统计分析。结果:双眼视力(P=0.000)及屈光度(P=0.006)均存在显著性差异,即形觉剥夺眼与双眼屈光度高者相关(P=0.005)。结论:处于生长发育期的儿童由于各种原因的单眼形觉剥夺可以造成双眼近视发生不一致,剥夺眼近视发生早,屈光度高。应引起重视并积极采取有效措施进行早期干预。     

Spatial coding and response redundancy in parallel visual pathways of the marmoset Callithrix jacchus

Many neurons in the primary visual cortex (area V1) show pronounced selectivity for the orientation and spatial frequency of visual stimuli, whereas most neurons in subcortical afferent streams show little selectivity for these stimulus attributes. It has been suggested that this transformation is a functional sign of increased coding efficiency, whereby the redundancy (or overlap in response properties) is reduced at consecutive levels of visual processing. Here we compared experimentally the response redundancy in area V1 with that in the three main dorsal thalamic afferent streams, the parvocellular (PC), koniocellular (KC), and magnocellular (MC) divisions of the dorsal lateral geniculate nucleus (LGN) in marmosets. The spatial frequency and orientation tuning of single cells in the LGN and area V1 were measured, using luminance contrast sine-wave gratings. A joint spatial frequency-orientation response selectivity profile was calculated for each cell. Response redundancy for each population was estimated by cross-multiplication of the joint selectivity profiles for pairs of cells. We show that when estimated in this way, redundancy in LGN neurons is approximately double that of neurons in cortical area V1. However, there are differences between LGN subdivisions, such that the KC pathway has a spatial representation that lies between the redundant code of the PC and MC pathways and the more efficient sparse spatial code of area V1.     

The response to visual form deprivation differs with age in marmosets

PURPOSE: To characterize the effects of visual form deprivation by diffuser in marmoset monkey eyes across a range of ages. METHODS: Twenty-four common marmosets were grouped by onset of deprivation (group 1: 0-39 days, n = 6; group 2: 40-99 days, n = 10; and group 3: 100-200 days, n = 8). Monocular form deprivation was induced with a white translucent diffuser worn for 28 to 88 days (mean durations: group 1, 32 days; group 2, 56 days; and group 3, 51 days). Refractive state, corneal curvature, and vitreous chamber depth were measured after cycloplegia. Both experimental and control eyes were measured multiple times before, during, and after the visual deprivation period. RESULTS: Marmosets in all age groups tested were susceptible to visual form deprivation myopia; however, the response to form deprivation was variable and included a majority with axial myopia (n = 15), several nonresponders (n = 4), a single late responder (axial myopia after the end of deprivation period), and several axial hyperopes (n = 4). For all animals that responded with axial myopia, the increase in vitreous chamber depth and myopia was inversely proportional to the age of onset of deprivation (ANOVA, P < 0.05). After the end of the period of deprivation, recovery from myopia by reduction of the axial growth rate was observed in three animals from group 1 and three animals from group 2. CONCLUSIONS: Form deprivation by diffusers disrupted emmetropization in marmosets over a range of ages. The responses varied among individuals and with age, suggesting that the maturity of the eye may influence the response to visual signals responsible for form deprivation myopia and perhaps emmetropization. Recovery from diffuser-induced form deprivation myopia was apparent in some animals, in contrast to that reported for visual deprivation by lid-suturing, and appears more prevalent in the younger animals.     

Long-range interactions in the lateral geniculate nucleus of the New-World monkey, Callithrix jacchus.

Visual stimulation of zones extending beyond the classical receptive field can modulate the contrast gain of neurons in the lateral geniculate nucleus (LGN) of cats, but little is known about the effect of extra-classical visual stimulation on the LGN of primates. Hence, we compare the effect of long-range interactions in parvocellular and magnocellular LGN layers of the marmoset monkey Callithrix jacchus using optimal, incremental spots flashed on the classical receptive field either alone or simultaneously with the shift of a grating (98% contrast; 0.1 cycles/deg) confined to a peripheral annulus (radii: 5-15 deg). The contrast required to drive the response halfway to saturation (c50) of most LGN neurons was raised by remote pattern shifts. The c50 ratio [(shift+spot)/spot] in OFF-center magnocellular neurons was significantly higher than in OFF-center parvocellular neurons. OFF-center magnocellular neurons closer to the fovea (<10 deg eccentricity) tended to have a higher c50 ratio than in more peripheral neurons. A significant drop in visual sensitivity to 25% contrast spots was observed during remote motion: d' fell from 1.8 to 1.4 in parvocellular neurons and from 2.2 to 1.7 in magnocellular neurons. Such long-range interactions produce a reduction in visual sensitivity by changing the gain of the geniculate relay and point to an inhibitory, motion-sensitive extra-classical receptive field in both parvocellular and magnocellular pathways, which may be involved in saccadic suppression and attentional mechanisms in early vision.     

形觉剥夺性近视中巩膜重塑机制的研究

近视是全球发病率最高的屈光不正,发病机制至今不明。形觉剥夺性近视（FDM）动物模型的建立为近视的病因学研究开辟了新局面。形觉剥夺主要通过“局部视网膜机制”来调控邻近巩膜的生长。外界刺激作用于视网膜,启动视网膜一视网膜色素上皮层一脉络膜信号转导系统,把局部视网膜信号转化为调控巩膜重塑的信号,诱导细胞外基质异常表达,巩膜胶原纤维改变等,引起巩膜重塑。就FDM中不同种属动物间巩膜重塑发生的形态学变化及相关因素等做一综述。     

The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus).

We made a comprehensive study, involving observations on 45 marmosets, of the effects on ocular growth and refraction of wearing spectacles from the ages of 4-8 weeks. This period was within the period early in life when the eye grows rapidly and refraction changes from hyperopia to its adult value of modest myopia. In one series of experiments we studied the effect of lenses of powers -8, -4, +4 and +8D fitted monocularly. In another series of experiments we studied the effect of lenses of equal and opposite powers fitted binocularly, with the two eyes alternately occluded, so as to give an incentive to use both eyes, and in particular to accommodate, for at least part of each day, through the negative lens. The vitreous chamber of eyes that wore negative lenses of -4D or -8D, combined with alternate occlusion, elongated more rapidly than that of the fellow eye (negative lens eye-positive lens eye, 0.21 +/- 0.03 mm (S.E.M.), P < 0.01 and 0.25 +/- 0.06 mm, P < 0.05, respectively) and became relatively more myopic (2.8 +/- 0.26D, P < 0.01 and 2.4 +/- 0.61D, P < 0.05 respectively). Eyes that wore -4D lenses monocularly elongated more rapidly and became myopic than fellow eyes. Eyes that wore +4D or +8D lenses were less strongly affected: animals that wore +8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia (0.99 +/- 0.21D, P < 0.01), with the more hyperopic eyes also slightly shorter (0.09 +/- 0.05 mm) than their fellow eyes, but eyes wearing +4D lenses were not significantly different from their fellow eyes. Animals that wore -8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia after three weeks of lens-wear (0.85 +/- 0.26D, P < 0.05). These were the only eyes that responded in a non-compensatory direction to the optical challenge of spectacle wear, and we interpret this effect as one due to visual deprivation. After the removal of lenses, the degree of anisometropia slowly diminished in those groups of animals in which it had been induced, but in the three groups in which the largest effects had been produced by lens-wear the overall mean anisometropia (0.68 +/- 0.24D, P < 0.01) and vitreous chamber depth (VCD) discrepancy (0.09 +/- 0.03 mm, P < 0.01) were still significant at the end of the experiments, when the animals were 273 days old. The reduction of anisometropia in these groups was associated with an increase in the rate of elongation of the vitreous chamber in the eyes that had previously grown normally i.e. the less myopic eyes grew more rapidly than their fellow eyes: in the seven weeks following lens-wear these eyes became more myopic and longer than normal eyes (refraction P < 0.001; VCD P < 0.001). Control experiments showed that occlusion of one eye for 50% of the day had no effect on eye growth and refraction, and therefore that alternate occlusion itself had no effect.