Purpose.  DL-alpha-aminoadipic acid (DL-α-AAA), a six-carbon chemical analog of L-glutamic acid, has selectively gliotoxic effects on retinal müller cells. The main objective of this study was to investigate the effect of intravitreal injection of DL-α-AAA on refractive state in guinea pig myopic eyes in order to determine whether retinal müller cells were involved in the deprivation-induced eye growth.
Methods.  Seventy-two guinea pigs, at age of four weeks, were randomly assigned to six groups: normal control, DL-α-AAA group, saline group, deprived group, deprived plus DL-α-AAA group and deprived plus saline group. Form deprivation was induced in thirty-six guinea pigs with self-made translucent eye shields on the right eye, and lasted for fourteen days. 8μg DL-α-AAA was injected into the vitreous chamber in the DL-α-AAA group and the deprived plus DL-α-AAA group. All animals underwent biometric measurement (corneal radius of curvature, refraction and axial length). Subsequently, Retinal vimentin protein was evaluated by the immunohistochemical staining and western blotting. Retinal apoptotic cells were analyzed by the terminal dexynucleotidyl transferase-mediated biotindeoxyuridine triphosphate nick-end labeling (TUNEL) staining.
Results.  The pigmented guinea pig eyes were mild hyperopia at six weeks of age. Treatment with DL-α-AAA significantly suppressed ocular emmetropization process as demonstrated by more hyperopia and lesser axial length than in the fellow and normal control eyes (P<0.05). After 14 days of eye occlusion, the deprived eyes became myopic (mean, -3.46±0.95D). DL-α-AAA treatment on deprived eyes caused a marked decrease in myopic diopters and axial length, compared with the deprived group (P<0.05). However, there was statistically significant difference in refractive and axial eye length between the normal control and DL-α-AAA-treatment deprived eyes (P<0.05). Vimentin protein was positively expressed in retinal Müller cells. There was the decrease of retinal vimentin protein in the DL-α-AAA-treatment eyes (P<0.05). No apoptotic retinal nuclei were found in all groups.
Conclusions.  DL-α-AAA is an effective antagonist to the excessive axial elongation in form-deprivation myopia in guinea pigs, which is potentially interesting to search new pharmacological alternatives for the control of myopia. It is possible that retinal müller cells play an regulatory role in the development of myopia in guinea pig.