幼年期豚鼠形觉剥夺性近视的动态变化

目的评价幼年期豚鼠在形觉剥夺性近视进展过程中眼球各项参数的动态变化。方法将48只幼年期雄性花色豚鼠(出生后3周)随机分为2组:实验组(单眼眼罩遮盖,n=24)和对照组(n=24)。每组又分为 4个亚组(n=6),分别在形觉遮盖开始前及开始后2、4、6和8周进行实验眼和对侧眼的生物学测量(屈光力、角膜曲率、眼轴长度、后巩膜干重)。使用线形相关分析遮盖时间与各测量参数之间的相关性。结果 (1)单眼面罩遮盖动物眼2周组实验眼较对侧眼增加(-1．79±0．58)D的近视(mean±SE;P<0．05;配对t检验;表1),遮盖8周组可达(-4．71±0．74)D(实验眼与对侧眼比较,所有时间段P<0．05);玻璃体腔长度较对侧眼延长,自遮盖2周组的(0．14±0．01)mm到遮盖8周组的(0．29±0．02)mm(试验眼与对侧眼比较,所有时间段P<0．05)。后巩膜干重较对侧眼减轻,自遮盖2周后的(-0．17±0．02)mg至遮盖8周后的(-0．35±0．04)mg(实验眼与对侧眼比较, 所有时间段P<0．05);(2)4组实验眼角膜曲率、前房深度、晶状体厚度与对侧眼之间无显著性差异(P>0．05)。 (3)对比实验眼与对侧眼之间屈光力、玻璃体腔长度、后巩膜干重的差异,面罩组和对照组之间存在显著性差异(所有时间段P<0．05)。(4)面罩组实验眼与对侧眼之间屈光力、玻璃体腔长度、后巩膜干重的差异与遮盖时间呈正相关关系。结论随时间的延长,遮盖豚鼠眼可诱导更多的近视度数,而后巩膜进一步变薄,干重减轻。     

Dynamic changes of ocular biometric parameters:a modified form-deprivation myopia model of young guinea pigs

AIM:To evaluate the dynamic ocular biometric changes of a modified form-deprivation myopia model in young guinea pigs.METHODS:The animals were randomly assigned to two groups:the monocularly deprived facemask group(MDF,with all the right eyes covered,n =24) and the normal control group(free of facemask,n =24).Each group was then equally divided into four subgroups which were followed up for 2,4,6 and 8 weeks,respectively.Parameters measured from every eye included refraction,corneal curvature,axial length and the dry weight of sclera at the posterior pole.RESULTS:All the facemasks remained in place during the follow-up.The covered eyes developed myopia with the vitreous chamber lengthening and the dry weight of posterior sclera reduced at each time point compared with the contralateral uncovered(P <0.05 at all time points).The changes had a linear correlation with the deprivation time(P <0.05).There were no significant differences in all the parameters between the uncovered eyes of MDF group and the normal control group(P >0.05 at all time points).CONCLUSION:Monocular form deprivation with the facemask is highly effective and non-invasive in inducing axial myopia in guinea pigs.The axial myopia is mainly caused by the increased vitreous chamber length and the weakened posterior sclera rigidity.The form-deprivation eye didn’t interfere with the natural development of the contralateral eye.     

Recovery from axial myopia induced by a monocularly deprived facemask in adolescent (7-week-old) guinea pigs

PURPOSE: Guinea pigs have been increasingly used as an animal model for experimental myopia. Infant guinea pigs are susceptible to recovery from myopia within 2 weeks of form deprivation. This study investigated whether adolescent guinea pigs are susceptible to recovery from myopia after a longer period of form deprivation. METHOD: Twenty-two guinea pigs (age of 3 weeks) were randomly assigned to two groups: MDF (monocularly deprived facemask, n=11) and normal control (free of form deprivation, n=11). All animals underwent biometric measurement (refraction, corneal curvature and axial length) prior to the experiment. Animals in the MDF group wore a facemask that covered the right eye for 4 weeks. The MDF was then removed and biometric measurement was performed immediately and at 2, 6, 10 and 14 days. The same measurement was performed in the normal control group at time-points matching those of the MDF group. RESULTS: The MDF eyes were approximately 4D more myopic with a greater increase in vitreous length by 0.12 mm compared to either the fellow or the normal control eyes after form deprivation (p<0.01). This relative myopia shifted rapidly towards hyperopia within 2 days after removal of the MDF, followed by a more gradual recovery. A complete recovery occurred by 6 days after removal of the MDF compared to the fellow and normal control eyes (p>0.05). Vitreous length in the MDF eyes slightly reduced within 2 days after removal of the MDF and then remained steady. The MDF eyes were similar to both the fellow and normal control eyes in vitreous length (p>0.05) 6 days after removal of the MDF. There was no significant difference between the MDF, fellow and normal control eyes in the other axial components during the form deprivation and recovery period. CONCLUSION: Adolescent guinea pigs are susceptible to recovery from MDF-induced myopia. The refractive recovery is mainly correlated to the inhibited axial elongation of the vitreous chamber of the previously deprived eyes.     

Dynamic changes of ocular biometric parameters: a modified form-deprivation myopia model of young guinea pigs

AIM: To evaluate the dynamic ocular biometric changes of a modified form-deprivation myopia model in young guinea pigs. METHODS: The animals were randomly assigned to two groups: the monocularly deprived facemask group (MDF, with all the right eyes covered, n=24) and the normal control group(free of facemask, n=24). Each group was then equally divided into four subgroups which were followed up for 2, 4, 6 and 8 weeks, respectively. Parameters measured from every eye included refraction, corneal curvature, axial length and the dry weight of sclera at the posterior pole. RESULTS: All the facemasks remained in place during the follow-up. The covered eyes developed myopia with the vitreous chamber lengthening and the dry weight of posterior sclera reduced at each time point compared with the contralateral uncovered(P<0.05 at all time points). The changes had a linear correlation with the deprivation time (P<0.05). There were no significant differences in all the parameters between the uncovered eyes of MDF group and the normal control group (P>0.05 at all time points). CONCLUSION: Monocular form deprivation with the facemask is highly effective and non-invasive in inducing axial myopia in guinea pigs. The axial myopia is mainly caused by the increased vitreous chamber length and the weakened posterior sclera rigidity. The form-deprivation eye didn't interfere with the natural development of the contralateral eye.     

Axial myopia induced by hyperopic defocus in guinea pigs: A detailed assessment on susceptibility and recovery

This study investigated whether adolescent guinea pigs can develop myopia induced by negative lenses, and whether they can recover from the induced myopia. Forty-nine pigmented guinea pigs (age of 3 weeks) were randomly assigned to 4 groups: 2-week defocus (n = 16), 4-week defocus (n = 9), 2-week control (n = 15) and 4-week control (n = 9). A −4.00 D lens was worn in the defocus groups and a plano lens worn in the control groups monocularly. The lenses were worn from 3 weeks to 5 weeks of age in the 2-week treatment groups with the biometry measured at 2, 4, 6, 10 and 14 days of lens wear. The lenses were worn from 3 weeks to 7 weeks of age in the 4-week treatment groups with the biometry measured immediately and at 2, 4, 6, 10 and 14 days after lens removal. Refractions in the defocused eyes developed towards myopia rapidly within 2 days of lens wear, followed by a slower development. The defocused eyes were at least 3.00 D more myopic with a greater increase in vitreous length by 0.08 mm compared to the fellow eyes at 14 days (p < 0.05). The estimated choroidal thickness of the defocused eyes decreased rapidly within 2 days of lens wear, followed by a slower decrease over the next 4 days. Relative myopia induced by 4 weeks of negative-lens treatment declined rapidly following lens removal. A complete recovery occurred 14 days after lens removal when compared to the fellow controls. The refractive changes during the recovery corresponded to a slower vitreous lengthening and a rapid thickening of the choroid. The plano-lens wearing eyes showed a slight but significant myopic shift (<−0.80 D) with no associated biometrical changes. Guinea pigs aged 3 weeks can still develop negative lens induced myopia and this myopia is reversible after removal of the lens. The myopia and recovery are mainly due to changes in vitreous length and choroidal thickness.     

Binocular lens treatment in tree shrews: Effect of age and comparison of plus lens wear with recovery from minus lens-induced myopia

We examined normal emmetropization and the refractive responses to binocular plus or minus lenses in young (late infantile) and juvenile tree shrews. In addition, recovery from lens-induced myopia was compared with the response to a similar amount of myopia produced with plus lenses in age-matched juvenile animals. Normal emmetropization was examined with daily noncycloplegic autorefractor measures from 11 days after natural eye-opening (days of visual experience [VE]) when the eyes were in the infantile, rapid growth phase and their refractions were substantially hyperopic, to 35 days of VE when the eyes had entered the juvenile, slower growth phase and the refractions were near emmetropia. Starting at 11 days of VE, two groups of young tree shrews wore binocular +4 D lenses (n = 6) or −5 D lenses (n = 5). Starting at 24 days of VE, four groups of juvenile tree shrews (n = 5 each) wore binocular +3 D, +5 D, −3 D, or −5 D lenses. Non-cycloplegic measures of refractive state were made frequently while the animals wore the assigned lenses. The refractive response of the juvenile plus-lens wearing animals was compared with the refractive recovery of an age-matched group of animals (n = 5) that were myopic after wearing a −5 D lens from 11 to 24 days of VE. In normal tree shrews, refractions (corrected for the small eye artifact) declined rapidly from (mean ± SEM) 6.6 ± 0.6 D of hyperopia at 11 VE to 1.4 ± 0.2 D at 24 VE and 0.8 ± 0.4 D at 35 VE. Plus 4 D lens treatment applied at 11 days of VE initially corrected or over-corrected the young animals’ hyperopia and produced a compensatory response in most animals; the eyes became nearly emmetropic while wearing the +4 D lenses. In contrast, plus-lens treatment starting at 24 days of VE initially made the juvenile eyes myopic (over-correction) and, on average, was less effective. The response ranged from no change in refractive state (eye continued to experience myopia) to full compensation (emmetropic with the lens in place). Minus-lens wear in both the young and juvenile groups, which initially made eyes more hyperopic, consistently produced compensation to the minus lens so that eyes reached age-appropriate refractions while wearing the lenses. When the minus lenses were removed, the eyes recovered quickly to age-matched normal values. The consistent recovery response from myopia in juvenile eyes after minus-lens compensation, compared with the highly variable response to plus lens wear in age-matched juvenile animals suggests that eyes retain the ability to detect the myopic refractive state, but there is an age-related decrease in the ability of normal eyes to use myopia to slow their elongation rate below normal. If juvenile human eyes, compared with infants, have a similar difficulty in using myopia to slow axial elongation, this may contribute to myopia development, especially in eyes with a genetic pre-disposition to elongate.     

Refractive and structural measures of lid-suture myopia in tree shrew

In order to study more thoroughly the refractive and structural changes associated with lid-suture myopia, five tree shrews were raised for approximately 16 weeks with monocular visual experience produced by lid closure. Four animals raised with normal laboratory visual experience served as a control group. Compared to the paired open eye, lid-sutured eyes were myopic (-12.1 +/- 6.3 diopters by retinoscopy), corneas were flatter (0.26 +/- 0.18 mm radius increase by photokeratometry) and axial lengths were greater (0.32 +/- 0.17 mm longer by A-scan ultrasonography). The axial length increase was due to elongation of the vitreous chamber (0.38 +/- 0.19 mm longer by A-scan ultrasonography). The open eyes of experimental animals were not significantly different than the normal eyes of control animals. Two of these treatment effects, namely, refractive state changes and axial length increases, were demonstrated with independent techniques: streak retinoscopy was compared to coincidence optometry, and A-scan ultrasound was compared to axial measurements of photographs of frozen, sectioned eyes. The three main ocular effects of eyelid closure were stable over three measurement sessions completed within a 4 week period. Additional refractive and A-scan measurements taken 7.5 months later showed no significant changes. Optical modelling showed that the observed myopia of the lid-sutured eye is consistent with the observed elongation of the vitreous chamber coupled with the flattened cornea although other changes could not be ruled out. We conclude that an axial myopia is produced reliably in tree shrews by raising them with eyelid closure and that the measurement techniques used in this study have sufficient resolution to study the development of myopia in this species.     

Retinal thinning in tree shrews with induced high myopia: optical coherence tomography and histological assessment

This study determined retinal thinning in a mammalian model of high myopia using optical coherence tomography (OCT) and histological sections from the same retinal tissue. High myopia was induced in three tree shrews (Tupaia belangeri) by deprivation of form vision via lid suture of one eye, with the other eye a control. Ocular biometry data was obtained by Ascan ultrasonography, keratometry and retinoscopy. The Zeiss StratusOCT was used to obtain Bscans in vivo across the retina. Subsequently, eyes were enucleated and retinas fixed, dehydrated, embedded and sectioned. Treated eyes developed a high degree of axial myopia (−15.9 ± 2.3 D; n = 3). The OCT analysis showed that in myopic eyes the nasal retina thinned more than the temporal retina relative to the disc (p = 0.005). Histology showed that the retinas in the myopic eyes comprise all layers but were thinner than the retinas in normal and control eyes. Detailed thickness measurements in corresponding locations of myopic and control eyes in superior nasal retina using longitudinal reflectivity profiles from OCT and semithin vertical histological sections showed the percentage of retinal thinning in the myopic eyes was similar between methods (OCT 15.34 ± 5.69%; histology 17.61 ± 3.02%; p = 0.10). Analysis of retinal layers revealed that the inner plexiform, inner nuclear and outer plexiform layers thin the most. Cell density measurements showed all neuronal cell types are involved in retinal thinning. The results indicate that in vivo OCT measurements can accurately detect retinal thinning in high myopia.     

The effect of age on compensation for a negative lens and recovery from lens-induced myopia in tree shrews (Tupaia glis belangeri)

We examined in tree shrews the effect of age on the development of, and recovery from, myopia induced with a negative lens. Starting at 11, 16, 24, 35 or 48 days after natural eye-opening (days of visual experience [VE]), juvenile tree shrews (n = 5 per group) wore a monocular −5 D lens for 11 days. A long-term lens-wear group (n = 6) began treatment at 16 days of VE and wore the lens for 30 days. A young adult group (n = 5) began to wear a −5 D lens between 93 and 107 days of VE (mean ± SD, 100 ± 6 days of VE) and wore the lens for 29-54 days (mean ± SD, 41.8 ± 9.8 days). The recovery phase in all groups was started by discontinuing −5 D lens wear. Contralateral control eyes in the three youngest groups were compared with a group of age-matched normal eyes and showed a small (<1 D), transient myopic shift. The amount of myopia that developed during lens wear was measured as the difference between the treated and control eye refractions. After 11 days of lens wear, the induced myopia was similar for the four younger groups (near full compensation: 11 days, −5.1 ± 0.4 D; 16 days, −4.7 ± 0.3 D; 24 days, −4.9 ± 0.4 D; 35 days, −4.0 ± 0.02) and slightly less in the oldest juvenile group (48 days, −3.3 ± 0.5 D). The young adult animals developed −4.8 ± 0.3 D of myopia after a longer lens-wear period. The rate of compensation (D/day) was high in the 4 youngest groups and decreased in the 48-day and young adult groups. The refractions of the long-term lens-wear juvenile group remained stable after compensating for the −5 D lens. During recovery, all animals in the youngest group recovered fully (<1 D residual myopia) within 7 days. Examples of both rapid (<10 days) and slow recovery (>12 days) occurred in all age groups except the youngest. Every animal showed more rapid recovery (higher recovery slope) in the first 4 days than afterward. One animal showed extremely slow recovery. Based on the time-course of myopia development observed in the youngest age groups, the start of the susceptible period for negative-lens wear is around 11-15 days after eye opening; the rate of compensation remains high until approximately 35 days of VE and then gradually declines. Compensation is stable with continued lens wear. The emmetropization mechanism, both for lens compensation and recovery, remains active into young adulthood. The time-course of recovery is more variable than that of compensation and seems to vary with age, with the amount of myopia (weakly) and with the individual animal.     

豚鼠形觉剥夺早期生物学参数的动态变化研究

目的:研究幼年豚鼠形觉剥夺早期生物学参数变化,得出其形觉剥夺早期过程中屈光动态的变化规律。方法:将20只豚鼠(出生后大约3wk)随机分成2组:MDF组(单眼面罩形觉剥夺组,n=10)和正常对照组(n=10)。面罩组和正常对照组的动物在形觉剥夺开始前和开始后2,4,6,10和14d进行了双眼的生物学测量(屈光力、眼轴各部分长度及视网膜、脉络膜厚度)。结果:MDF组实验眼脉络膜厚度在第10,14d较对侧眼有显著性差异(P<0.05),但较正常对照眼均无显著性差异。结论:豚鼠形觉剥夺早期视网膜并不发生明显的厚度和病理改变,而脉络膜厚度有缩短的趋势。     

Individual set-point and gain of emmetropization in chickens

During the developmental process of emmetropization evidence shows that visual feedback guides the eye as it approaches a refractive state close to zero, or slightly hyperopic. How this “set-point” is internally defined, in the presence of continuous shifts of the focal plane with different viewing distances and accommodation, remains unclear. Minimizing defocus blur over time should produce similar end-point refractions in different individuals. However, we found that individual chickens display considerable variability in their set-point refractive states, despite that they all had the same visual experience. This variability is not random since the refractions in both eyes were highly correlated - even though it is known that they can emmetropize independently. Furthermore, if chicks underwent a period of experimentally induced ametropia, they returned to their individual set-point refractions during recovery (correlation of the refractions before treatment versus after recovery: n = 19 chicks, 38 eyes, left eyes: slope 1.01, R = 0.860; right eyes: slope 0.85, R = 0.610, p < 0.001, linear regression). Also, the induced deprivation myopia was correlated in both eyes (n = 18 chicks, 36 eyes, p < 0.01, orthogonal regression). If chicks were treated with spectacle lenses, the compensatory changes in refraction were, on average, appropriate but individual chicks displayed variable responses. Again, the refractions of both eyes remained correlated (negative lenses, n = 18 chicks, 36 eyes, slope 0.89, R = 0.504, p < 0.01, positive lenses: n = 21 chicks, 42 eyes, slope 1.14, R = 0.791, p < 0.001). The amount of deprivation myopia that developed in two successive treatment cycles, with an intermittent period of recovery, was not correlated; only vitreous chamber growth was almost significantly correlated in both cycles (n = 7 chicks, 14 eyes; p < 0.05). The amounts of ametropia and vitreous chamber changes induced in two successive cycles of treatment, first with lenses and then with diffusers, were also not correlated, suggesting that the “gains of lens compensation” are different from those in deprivation myopia. In summary, (1) there appears to be an endogenous, possibly genetic, definition of the set-point of emmetropization in each individual, which is similar in both eyes, (2) visual conditions that induce ametropia produce variable changes in refractions, with high correlations between both eyes, (3) overall, the “gain of emmetropization” appears only weakly controlled by endogenous factors.     

不同浓度阿托品滴眼液对豚鼠形觉剥夺性近视的影响

目的探讨不同浓度阿托品滴眼液对单眼形觉剥夺幼年豚鼠的屈光发育的影响,并分析阿托品抑制近视的可能作用位点和机制。方法实验研究。将80只3周龄体质量在100 g左右的豚鼠随机分至5组：单眼形觉剥夺4周组（8只）、形觉剥夺加点药同时进行4周组（每个浓度各8只）、形觉剥夺2周后再加点药2周组（每个浓度各8只）、单纯点药4周组（每个浓度各6只）、空白对照组（6只）。阿托品粉剂溶于单蒸水配制成3个浓度的阿托品滴眼液：0.2%、1.0%、3.0%。每天早上8∶30-9∶00间点药。在实验前、实验2 周、实验4 周时测量各组豚鼠屈光力、角膜曲率、眼轴长度等相关生物学参数。实验4周结束后取豚鼠眼视网膜做冰冻切片,免疫荧光法标记豚鼠视网膜上表达胰高血糖素的细胞。采用配对样本t检验和重复测量的双因素方差分析进行数据分析。结果单纯形觉剥夺组,实验2周后实验眼屈光度较自身对照眼往近视方向发展,同时伴有玻璃体腔加深、眼轴延长,差异有统计学意义（t=-11.09、7.89、3.73,P<0.05）;4周后,差异更显著。形觉剥夺加点药同时进行的3个浓度组,实验2周后实验眼与自身对照眼的各屈光参数差异均无统计学意义,而2眼差值与单纯剥夺组比较,屈光度、玻璃体腔深度、眼轴长度差异均有统计学意义（F=26.335、6.479、6.910,P<0.05）;4周后,3个浓度组实验眼屈光度与自身对照眼比较均开始往近视方向发展,差异有统计学意义（t=-4.67、-7.54、-2.78,P<0.05）,同时玻璃体腔加深,眼轴延长,而2眼差值与单纯剥夺组比较,各屈光参数的差异仍有统计学意义（F=16.962、5.193、6.882,P<0.05）;但3个浓度组的组间两两比较显示,各参数实验前后差异无统计学意义。形觉剥夺2周后再加点药2周组,实验4周后各浓度组2眼差值与单纯剥夺4周组比较,各屈光参数差异均无统计学意义。各组豚鼠视网膜上均未标记出胰高血糖素表达阳性的细胞。结论在3%的浓度范围内,阿托品滴眼液能通过抑制玻璃体腔加深、眼轴延长从而部分抑制豚鼠形觉剥夺性近视的发生,且作用效果没有明显的浓度依赖性。但在近视形成后运用阿托品,并不能抑制近视的进展。胰高血糖素能途径没有参与阿托品对豚鼠近视发生发展的作用过程。     

Effects of unilateral topical atropine on binocular pupil responses and eye growth in mice

Purpose

Studies on drugs selected to target myopia development often use the vehicle-treated fellow eye as a control. However, it is not clear how much of the drug reaches the fellow eye, rendering it a potentially invalid control. Therefore, in this study, pupil responses were used to probe the effects of atropine in both eyes in mice, after unilateral topical application. In a second experiment, interocular differences in refractive development and axial eye growth were studied while atropine was applied daily to one eye.

Methods

In 20 C57BL/6 (B6) wildtype mice, a single drop of 1% atropine solution was instilled into one eye. Mice were gently restrained by holding their necks while video image processing software detected the pupil and measured its diameter at a sampling rate of 30 Hz. A bright green LED, attached to the photoretinoscope of the video camera, was flashed. Pupil responses were quantified daily over a period of 2 weeks. In another group of 24 mice, one drop of 1% atropine was applied daily for 28 days. Axial length was measured pre- and post-treatment, using low coherence interferometry (the Zeiss AC-Master). Refractive development was measured by infrared photorefraction.

Results

Similar to previous findings with the same device, untreated eyes displayed a pupil constriction of 24.84 ± 1.73% upon stimulation with the green LED. A single drop of 1% atropine caused complete suppression with no significant recovery over the whole observation period of two weeks. The responses in the fellow eye were temporarily reduced to about 75% and then recovered towards baseline. After daily atropine application, there was significant reduction in axial length of the eyes, relative to the saline-treated fellow eyes (3.234 ± 0.186 versus 3.378 ± 0.176 mm, n = 24, p < 0.01, paired t-test) and the refractions became more hyperopic/less myopic (+13.46 ± 2.15 D versus +10.06 ± 2.02 D, n = 24, p < 0.01).

Conclusions

In line with previous findings, one drop of atropine solution caused a long lasting suppression of pupil responses in the mouse eye. New data show that the transfer to the fellow eye was limited, making interocular comparisons feasible. It is also new that topical atropine reduced axial eye growth even when mice had largely normal vision.     

Time course of rhesus lid-suture myopia

Axial-length and refraction measurements are presented for the lid-sutured rhesus monkey at 6-month intervals during the first 1.5 years of life. The experimental data are fitted to an exponential growth theory allowing the calculation of time constants, apparent time origins, and correlation coefficients for 10 eyes from five animals. On average, axial length develops with a time constant of 0.40 year for lid-suture myopia, compared with 0.42 year for the normal eye. A practical application of this work is that one must allow 1.6 years of lid suture to achieve 95% of the total refractive or axial-length change.     

Recovery from form-deprivation myopia in rhesus monkeys

PURPOSE: Although many aspects of vision-dependent eye growth are qualitatively similar in many species, the failure to observe recovery from form-deprivation myopia (FDM) in higher primates represents a significant potential departure. The purpose of this investigation was to re-examine the ability of rhesus monkeys (Macaca mulatta) to recover from FDM. METHODS: Monocular form deprivation was produced either with diffuser spectacle lenses (n = 30) or by surgical eyelid closure (n = 14). The diffuser-rearing strategies were initiated at 24 +/- 3 days of age and continued for an average of 115 +/- 20 days. Surgical eyelid closure was initiated between 33 and 761 days of age and maintained for14 to 689 days. After the period of form deprivation, the animals were allowed unrestricted vision. The ability of the animals to recover from treatment-induced refractive errors was assessed periodically by retinoscopy, keratometry, and A-scan ultrasonography. Control data were obtained from 35 normal monkeys. RESULTS: At the onset of unrestricted vision, the deprived eyes of 18 of the diffuser-reared monkeys and 12 of the lid-sutured monkeys were at least 1.0 D less hyperopic or more myopic than their fellow eyes. The mean (diffuser = -4.06 D, lid-suture = -4.50 D) and range (diffuser = -1.0 to -10.19 D, lid-suture = -1.0 to -10.25 D) of myopic anisometropia were comparable in both treatment groups. All 18 of these diffuser-reared monkeys demonstrated recovery, with 12 animals exhibiting complete recovery. The rate of recovery, which was mediated primarily by alterations in vitreous chamber growth rate, declined with age. None of the lid-sutured monkeys exhibited clear evidence of recovery. Instead, 8 of the 12 lid-sutured monkeys exhibited progression of myopia. CONCLUSIONS: Like many other species, young monkeys are capable of recovering from FDM. However, the potential for recovery appears to depend on when unrestricted vision is restored, the severity of the deprivation-induced axial elongation, and possibly the method used to produce FDM.     

Evaluación de las modificaciones biométricas del ojo durante la succión del LASIK

PurposeTo study the biometric modifications of the eyeball during suction in laser assisted in situ keratomileusis (LASIK).MethodsObservational and cross-sectional study. We studied 43 patients who underwent surgery for myopia and myopic astigmatism. Mean age was 38.3±11.5 years, and 19 were female (44.2%). Conventional LASIK surgery with a manual microkeratome was performed. Before and during the suction maneuvre the following parameters were measured using an 11 MHz biometric probe: aqueous depth (AQD), lens thickness (LT), vitreous cavity length (VCL) and axial length (AXL). Paired t-test was used to compare the biometric measurements before and during suction.ResultsThe mean spherical equivalent refractive error was −4.5±2.3 diopters. During suction, the AQD did not change significantly (p = 0.231). However, AXL and VCL increased by 0.12 mm and 0.22 mm respectively (p = 0.039 and <0.01) and LT decreased by 0.20 mm (p<0.01). AXL increased in 42% of the eyes and decreased in 16%, VCL increased in 70% of the eyes and decreased in 9%, and the LT was reduced in 67% of the eyes.ConclusionsSuction maneuvres during LASIK surgery produce changes of little magnitude in the eye globe, mainly a decrease in LT and an increase in VCL and AXL. Therefore, these modifications are expected to produce minimal anatomic alterations.     

Total ocular, anterior corneal and lenticular higher order aberrations in hyperopic, myopic and emmetropic eyes

Total ocular higher order aberrations and corneal topography of myopic, emmetropic and hyperopic eyes of 675 adolescents (16.9 ± 0.7 years) were measured after cycloplegia using COAS aberrometer and Medmont videokeratoscope. Corneal higher order aberrations were computed from the corneal topography maps and lenticular (internal) higher order aberrations derived by subtraction of corneal aberrations from total ocular aberrations. Aberrations were measured for a pupil diameter of 5 mm. Multivariate analysis of variance followed by multiple regression analysis found significant difference in the fourth order aberrations (SA RMS, primary spherical aberration coefficient) between the refractive error groups. Hyperopic eyes (+0.083 ± 0.05 μm) had more positive total ocular primary spherical aberration compared to emmetropic (+0.036 ± 0.04 μm) and myopic eyes (low myopia = +0.038 ± 0.05 μm, moderate myopia = +0.026 ± 0.06 μm) (p < 0.05). No difference was observed for the anterior corneal spherical aberration. Significantly less negative lenticular spherical aberration was observed for the hyperopic eyes (−0.038 ± 0.05 μm) than myopic (low myopia = −0.088 ± 0.04 μm, moderate myopia = −0.095 ± 0.05 μm) and emmetropic eyes (−0.081 ± 0.04 μm) (p < 0.05). These findings suggest the existence of differences in the characteristics of the crystalline lens (asphericity, curvature and gradient refractive index) of hyperopic eyes versus other eyes.     

Factors Affecting Long-term Myopic Regression after Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Moderate Myopia

PurposeHigh myopia is known to be a risk factor for long-term regression after laser refractive surgery. There have been few studies about the correction of moderate myopias that did not need retreatment after long-term follow-up. We evaluated 10 years of change in visual acuity and refractive power in eyes with moderate myopia after laser refractive surgery.MethodsWe included patients that had undergone laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASEK) to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity in terms of safety, efficacy, and refractive changes at examinations 6 months and 1, 2, 5, 7, and 10 years after surgery.ResultsThe study evaluated 62 eyes (36 eyes in LASIK patients and 26 eyes in LASEK patients). In both groups, the efficacy index tended to decrease, and it was consistently higher in the LASEK group compared to the LASIK group over the 10 years of follow-up. The safety index improved over 10 years and was always higher than 0.9 in both groups. The difference between the spherical equivalent at 6 months postoperatively and later periods was statistically significant after 5, 7, and 10 years in both groups (LASIK, p = 0.036, p = 0.003, and p < 0.001, respectively; LASEK, p = 0.006, p = 0.002, and p = 0.001, respectively). Ten years after surgery,26 eyes (66.7%) in the LASIK group and 19 eyes (73.1%) in the LASEK group had myopia greater than 1 diopter. In comparison with the thickness at 6 months postoperatively, central corneal thickness was significantly increased after 5, 7, and 10 years in both LASIK and LASEK groups (LASIK, p < 0.001, p < 0.001, and p < 0.001, respectively; LASEK, p = 0.01, p < 0.001, and p < 0.001, respectively).ConclusionsModerately myopic eyes showed progressive myopic shifting and corneal thickening after LASIK and LASEK during 10 years of follow-up. We also found that early refractive regression may indicate the long-term refractive outcome.     

Anterior chamber inflammation after transconjunctival cryosurgery

Background: Inflammation caused by transconjunctival cryotherapy for prophylactic retinal detachment surgery was measured in various conditions. Methods: Thirty-four eyes of 28 patients with peripheral retinal lesions predisposing to retinal detachment were studied by laser flare cell meter before and after treatment. Results: The mean flare value for 34 eyes was 4.06 ± 1.45 photon counts/ms before surgery and 5.72 ± 2.52 pc/ms after surgery (p < 0.05). Flare value was elevated at 1, 2, and 3 weeks after treatment, peaking at 2 weeks (p < 0.05), and normal again at 4 weeks. There were no significant differences in flare increase between eyes with and without retinal breaks, eyes with and without limited retinal detachment, eyes with myopia more and less than – 8.0 D, and eyes with a treatment area limited to one quadrant and extending over more than one quadrant. Conclusion: Transconjunctival cryosurgery caused mild inflammation in the anterior chamber of the eye for 3 weeks. The inflammation was not affected by the presence of retinal break or limited retinal detachment, the degree of myopia, or the extent of the treatment area.     

Neuroprotective effects of recombinant human granulocyte colony-stimulating factor (G-CSF) in neurodegeneration after optic nerve crush in rats

The purpose of the present study was to investigate the effects of granulocyte colony-stimulating factor (G-CSF) on neurodegeneration of optic nerve (ON) and retinal ganglion cells (RGCs) in a rat model of ON crush. The ONs of adult male Wistar rats (150-180 g) were crushed by a standardized method. The control eyes received a sham operation. G-CSF (100 μg/kg/day in 0.2 ml phosphate-buffered saline) or phosphate-buffered saline (PBS control) was immediately administered after ON crush for 5 days by subcutaneous injection. Rats were euthanized at 1 or 2 weeks after the crush injury. RGC density was counted by retrograde labeling with FluoroGold application to the superior colliculus, and visual function was assessed by flash visual evoked potentials (FVEP). TUNEL assay, Western blot analysis and immunohistochemistry of p-AKT in the retina and ED1 (marker of macrophage/microglia) in the ON were conducted. 2 weeks after the insult, the RGC densities in the central and mid-peripheral retinas in ON-crushed, G-CSF-treated rats were significantly higher than that of the corresponding ON-crushed, PBS-treated rats (survival rate was 60% vs. 19.6% in the central retina; 46.5% vs. 23.9% in mid-peripheral retina, respectively; p < 0.001). FVEP measurements showed a significantly better preserved latency of the p1 wave in the ON-crushed, G-CSF-treated rats than the ON-crushed, PBS-treated rats (78 ± 9 ms in the sham operation group, 98 ± 16 ms in the G-CSF-treated group, and 174 ± 16 ms in the PBS-treated group; p < 0.001). TUNEL assays showed fewer apoptotic cells in the retinal sections in the ON-crushed, G-CSF-treated rats. p-AKT immunoreactivity was up-regulated in the retinas of the ON-crushed, G-CSF-treated rats at 1 and 2 weeks. In addition, the number of ED1-positive cells was attenuated at the lesion site of the optic nerve in the ON-crushed, G-CSF-treated group. From these results, we gather that administration of G-CSF is neuroprotective in the rat model of optic nerve crush, as demonstrated both structurally by RGC density and functionally by FVEP. G-CSF may work by being anti-apoptotic involving the p-AKT signaling pathway as well as by attenuation of the inflammatory responses at the injury site, as evidenced by less ED1-positive cell infiltration in the optic nerve.