Hendrickson A, Drucker D
Department of Ophthalmology, University of Washington, Seattle 98195.
Behav Brain Res. 1992 Jul 31;49(1):21-31. doi: 10.1016/s0166-4328(05)80191-3.
The morphological development of parafoveal retina (1-1.5 mm from the foveal center) and the mid-peripheral (4 mm from the foveal center) human retina has been studied from fetal (F) 26 weeks to adulthood. At both retinal points, all layers and neuronal types are present at F26 weeks. In parafovea at F26 weeks photoreceptors have only a rudimentary inner segment and no outer segments. Short outer segments are present on both rods and cones at F36 weeks. By postnatal (P) 5-8 days the inner retina is relatively mature. Photoreceptors have elongated basal axons which cause the photoreceptor layer to become much thicker than in prenatal retina. At birth cone inner segments are untapered, but rod inner segments have already reached their adult width of 2 microns. Both rod and cone inner and outer segments are 30-50% of adult length. By 13 months both inner and outer retina are mature appearing, with the photoreceptors accounting for half the retinal thickness due to the elongation of the fibers of Henle. Cone outer segments elongate up to P5 years and rod outer segments to P13 years. At mid-peripheral or rod-ring retina outer segments are present on rods at F26 weeks and on cones at F36 weeks. At birth the inner retina is adultlike. The outer plexiform layer becomes thicker up to P45 months due to the elongation of fibers of Henle. At birth both rod and cone mid-peripheral inner segments are slightly longer and outer segments are 50% longer than in parafoveal retina. By P5 years mid-peripheral rod outer segments are slightly longer than in parafoveal retina, and this changes little thereafter. This anatomical study has found that the photoreceptors in peripheral rod-ring retina develop earlier than those in more central retina, and in turn parafoveal photoreceptors develop well in advance of foveal cones. This suggests that human neonates may utilize more peripheral retinal regions for some aspects of visual function before foveal cone vision becomes dominant.
对距中心凹中心1 - 1.5毫米的旁中心凹视网膜以及距中心凹中心4毫米的中周部人类视网膜的形态发育进行了研究，研究对象从胎儿（F）26周直至成年。在这两个视网膜部位，所有层次和神经元类型在F26周时均已存在。在F26周时，旁中心凹的光感受器仅有一个雏形内节，没有外节。在F36周时，视杆和视锥上均出现了短外节。到出生后（P）5 - 8天，视网膜内层相对成熟。光感受器有伸长的基部轴突，这使得光感受器层比产前视网膜厚得多。出生时，视锥内节没有逐渐变细，但视杆内节已达到其2微米的成人宽度。视杆和视锥的内节和外节长度均为成人长度的30 - 50%。到13个月时，视网膜内层和外层均呈现成熟状态，由于Henle纤维的伸长，光感受器占视网膜厚度的一半。视锥外节一直伸长到P5岁，视杆外节伸长到P13岁。在中周部或视杆环视网膜，视杆的外节在F26周时出现，视锥的外节在F36周时出现。出生时，视网膜内层已类似成人。由于Henle纤维的伸长，外网状层一直增厚到P45个月。出生时，中周部视杆和视锥的内节均略长，外节比旁中心凹视网膜长50%。到P5岁时，中周部视杆外节比旁中心凹视网膜略长，此后变化不大。这项解剖学研究发现，周边视杆环视网膜的光感受器比更中心部位视网膜的光感受器发育更早，反过来，旁中心凹光感受器比中央凹视锥发育要早得多。这表明，在中央凹视锥视觉占主导之前，人类新生儿可能在视觉功能的某些方面利用更多周边视网膜区域。
