| Background and PurposeMyopia is a leading cause of loss of vision throughout the world, and its prevalence is increasing. The World Health Organization (WHO) has already ranged it in the World Prevention of Blindness Plans. High myopia is also called as pathological myopia or degeneration myopia. Its incidence is estimated at 3~6% in the people of myopia. Its pathogenesis is holding unclear today, but form deprivation theory argues that the local retina controls the abnormal growth of the sclera leading to myopia. Many factors in the retina whose amount changes as a response of form deprivation play important roles in the development of FDM.Nerve growth factor is discovered before more than 50 years. It exertseffects by signaling through surface membrane receptors , trkA and P75 in the neurotissue and unneurotissue. NGF expresses and influences the shape and function of the three kinds of neuron in the retina. Nastri G (1998) had discovered that Anti-NGF serum eye drops were able to elicit a slight contraction on ocular overgrowth in chicks raised in continuous light. He suggested the NGF was possible to take part in the development of FDM.To determine the role of nerve growth factor (NGF) in the development of FDM in the chicks, we evaluated the expressions of NGF and its mRNA in the chicken retina by immunohistochemistry and in situ hybridization. Materials and Methods30 male hailen chicks were selected and were randomly divided into 3 groups. All right eyes underwent form deprivation with transplant goggles, and the left eyes were used as control. After the right eyes were randomly occluded for 3 , 7 , 14 days, the refractive state was respectively determined by means of streak retinascopy ( without cycloplegia ). Extracted the eyes and measured the axial length and equatorial diameter with vernier calliper, before routine fixation, dehydration, paraffin embedding, 4 and 6um paraffin sections were taken. Routine hematoxylin-eosin (HE), immunohistochemistry staining and in situ hybridization were respectively used to study the morphological changes in the retina and sclear under light microscope.Results(1 )Form deprivation could lead to development of myopia: the axial length had signigicant difference between the occluded eyes and the control eyes (P< 0.001). The longer the eyes were occluded, the more serious the myopia was, and there was significant difference among groups at different time. There was the linear correlation between the refractive state and the axial length in the occluded eyes (r=0.983) .(2) HE staining showed that the occluded retina especially the inner plexus layer, became thinner and the posterior cartilaginous sclera become thicker than the control retina. There were larger number of the binuclear cells in the posterior cartilaginous sclera where the density of cells became decrease.(3 ) Immunohistochemical staining showed that NGF positive expression was detected in the ganglion cell layer (GCL) , inner nuclear layer (INL) and sclera layer (SL), especially in the binuclear cells. The rate or amount of the positive cells in the occluded eyes was significantly higher than the control in the same group. The rate or amount of the positive cells among the occluded eyes and the control eyes significantly decreased along with the time. In the occluded eyes, there was multiple linear regression among the axial length (y), the positive rate of GCs (x3, Bi=-0.236) , the positive rate of the sclera (x2, Bi=-0.222) , and the positive amount in INL ( xh Bi=-0.583 ) . Its equation wasy=17.621-0.583xr0.236x2-0.222x3.(4) The positive cells labelled NGF mRNA were detected in the GCL, INL and chondrocyte in the sclera. The rate or amount of the positive cells in the occluded eyes was significantly higher than the control in the same group. The rate or amount of the positive cells among the occluded eyes and the control eyes significantly decreased along with the time.(5 ) The positive cells expressing NGF had positive correlation with these expressing NGF mRNA in the occluded e...
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