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Purpose: The proportion of axial length (AL) occupied by vitreous chamber depth (VCD), or VCD:AL, consistently correlates to ocular biometry in the general population. Relation of VCD:AL to ocular biometry in high myopia is not known. The purpose of this study is to evaluate the relation of VCD and VCD:AL to ocular biometry of highly myopic eyes. Methods: This was a cross?sectional retrospective study of records of 214 myopic eyes (<?1 D SE, aged 20–40 years) attending the refractive surgery services. High axial myopia was defined as AL >26.5 mm. Eyes with posterior staphyloma and myopic maculopathy were excluded. Records were assessed for measurements of AL, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), white to white diameter (WTW), and vitreous chamber depth (VCD). Groups were formed based on increasing AL, while the sum of CCT, ACD, and LT was recorded as anterior segment depth (AS). The main outcome measure was the correlation of VCD and VCD:AL to ocular biometry. A comparison was also performed based on of degree of axial myopia. Results: Mean age of the patients was 27.0 ± 5.2 years. VCD showed a very strong correlation with AL (R = 0.98, P < 0.001) but did not correlate to any anterior parameter. VCD:AL showed moderate negative relation with AS (R = ?0.43, P < 0.001) and ACD (R = ?0.3, P < 0.001), while it had a weakly negative relation with LT (R = ?0.18, P = 0.006). VCD:AL showed strong negative relation (R > ~0.7) with AS in all individual groups of AL. Among anterior parameters, WTW showed the most consistent relation with ocular biometry. Conclusion: VCD:AL is a better correlate of ocular biometry in high myopia as compared to VCD. However, the correlation is weaker than that noted by previous studies done on the general population. Longitudinal studies of VCD:AL in the younger age group is recommended
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Purpose: The mechanism of ocular growth eludes us and research on vitreous chamber depth (VCD) is lacking. The purpose of this study was to evaluate the role of VCD and its ratio to axial length (AL) in relation to ocular biometry. Methods: This retrospective study of patients planned for cataract surgery was performed at a tertiary center. Data regarding AL, anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) of 640 eyes was noted. Anterior segment (AS) was measured as sum of CCT, ACD, and LT, while VCD was calculated as the difference between AL and AS. Correlation of VCD and VCD: AL with ocular biometry was the primary outcome measure. Three groups were formed on the basis of AL and Pearson correlation coefficient (R) was applied. Results: Mean VCD was 15.38+/?1.14 mm. Mean VCD: AL was 0.66+/?0.02. VCD had a very strong relation with AL (R = 0.9, P < 0.001) only, whereas VCD: AL had a good--strong relation with AL (R = 0.5, P < 0.001), AS (R = 0.7, P < 0.001), ACD (R = 0.3, P < 0.001), and LT (R = 0.5, P < 0.001). The relation of VCD: AL with AS was very strong across all groups (R ? -0.8, P < 0.001 in all groups). 85% of eyes in group with AL <22 mm had VCD: AL <0.67, conversely 85% of eyes with AL >24.5 mm had VCD: AL >0.67. Conclusion: We found VCD to have the strongest relation with AL. VCD: AL was more consistent and showed a strong relation to ocular biometry across all ALs. This suggests the possible utility of the ratio VCD: AL while evaluating ocular growth, refractive status, and myopia-related complications.
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Background Light stimulation at different wavelength influences the development of eyes.It has been showed that blue light can inhibit the growth of eyeball.To study whether blue light exposure can delay the extension of myopia is an interested research project.Objective This study was to investigate the effect of blue light with short wavelength on ocular growth in form deprived myopia (FDM) in guinea pigs and provide a new option for the prevention and treatment of myopia.Methods Thirty-six 2-week-old guinea pigs were reared in the environment of white light.The right eyes of the animals were occluded to establish the FDM models.The models were randomized into the deocclusion + blue light exposure group,simple deocclusion group and continuous occlusion group according to the random number table.The right eyes of the models were deoccluded for 1 hour per day to give the blue light (430 nm) irradiation in the deocclusion + blue light exposure group,and the right eyes were deoccluded for 1 hour per day only in the simple deocclusion group.In the continuous occlusion group,the right eyes of the models were occluded until the end of this experiment.Anterior chamber depth (ACD),lens thickness (LT) and vitreous cavity depth (VCD) were measured by A-type sonography.The binocular diopter of the guinea pigs was detected using retinoscopy in the mydriatic condition.In the fourth week after experiment,the retinal sections were prepared for the regular histopathological examination,and the scleral tissues next to 1 mm from optical nerve were exacted to obtain the dry weight of scleral tissues.Results In the right eyes of the animals,no significant differences were found in the diopter,ACD,LT and VCD before experiment among the 3 groups (all at P＞0.05).At the end of experiment,the refraction of right eye in the deocclusion + blue light exposure group,simple deocclusion group and continuous occlusion group was (+1.11±0.17)D,(+0.90±0.15)D and (-2.73±0.19)D respectively,with a significant difference among them (F=1 445.470,P=0.000).The VCD in the three groups was (3.70±0.09) mm,(3.78±0.11) mm and (3.91 ± 0.08) mm,respectively,showing a significant difference (F =13.243,P＜0.01).In addition,the dry weight of sclera tissues was (0.61 ±0.09)mg in the deocclusion + blue light exposure group,(0.54± 0.08)mg in the simple deocclusion group and (0.43 ± 0.07)mg in the continuous occlusion group,with a significant difference among the 3 groups (F=10.458,P＜0.01).However,there were no significant differences in the ACD and LT among the 3 groups (F=0.203,0.084,both at P＞0.05).Moreover,in the left eyes,no significant differences were found in the diopter,ACD,LT and VCD before experiment among the 3 groups (all at P＞0.05);while at the end of the experiment,the diopter of the continuous occlusion group was significantly lower than that of the deocclusion + blue light exposure group and simple deocclusion group (all at P＜0.05).No significant differences were seen in the ACD,LT,VCD and dry weight of sclera among the 3 groups (all at P＞0.05).Retinal structure was normal in the left eyes of various groups.However,the retinas were thinner in the right eyes of the deocclusion + blue light exposure group with clear layers; while atrophy of the outer segment of photoreceptor and disorder of cell arrangement were seen in the right eyes of the continuous occlusion group.Conclusions During sensitive period of visual development,blue light stimulation can arrest the extension of posterior sclera and elongation of vitreous cavity,which restrains development of myopia.This blue light at the wavelength of 430 nm is safe to retina.