Levodopa inhibits the development of form-deprivation myopia in guinea pigs.
OBJECTIVE
It has been shown that visual deprivation leads to a myopic refractive error and also reduces the retinal concentration of dopamine. Exogenously 3,4-dihydroxy-L-phenylalanine (levodopa, L-DOPA) can be converted into dopamine in vivo, which safely and effectively treats Parkinson disease. Moreover, L-DOPA was also used in the treatment of amblyopia in clinical studies. However, the effect of L-DOPA on the development of myopia has not been studied. The aim of this study was to investigate whether intraperitoneal injection of L-DOPA could inhibit form-deprivation myopia in guinea pigs and to explore a new strategy for drug treatment of myopia.


METHODS
Sixty guinea pigs, at age of 4 weeks, were randomly divided into six groups: normal control, L-DOPA group, saline group, deprived group, deprived plus L-DOPA group, and deprived plus saline group. Form deprivation was induced with translucent eye shields on the right eye and lasted for 10 days. L-DOPA was injected intraperitoneally into the guinea pig once a day. The corneal radius of curvature, refraction, and axial length were measured in all animals. Subsequently, retinal dopamine content was evaluated by high-performance liquid chromatography with electrochemical detection.


RESULTS
Ten days of eye occlusion caused the form-deprived eyes to elongate and become myopic, and retinal dopamine content to decrease, but the corneal radius of curvature was not affected. Repeated intraperitoneal injection of L-DOPA could inhibit the myopic shift (from -3.62 +/- 0.98 D to -1.50 +/- 0.38 D; p < 0.001) due to goggles occluding and compensate retinal dopamine (from 0.65 +/- 0.10 ng to 1.33 +/- 0.23 ng; p < 0.001). Administration of L-DOPA to the unoccluded animals had no effect on its ocular refraction. There was no effect of intraperitoneal saline on the ocular refractive state and retinal dopamine.


CONCLUSIONS
Systemic L-DOPA was partly effective in this guinea pig model and, therefore, is worth testing for effectiveness in progressing human myopes.
Mao
Junfeng
J
Department of Ophthalmology, Xiang-Ya Hospital, Central South University, Changsha, Hunan, China. mao_junfeng@163.com
Liu
Shuangzhen
S
Qin
Wenjuan
W
Li
Fengyun
F
Wu
Xiaoying
X
Tan
Qian
Q
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004195:Disease Models, Animal; D015259:Dopamine Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005556:Form Perception / Q000502:physiology*; D006168:Guinea Pigs; D007274:Injections, Intraperitoneal; D007980:Levodopa / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D009216:Myopia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D012160:Retina / Q000187:drug effects / Q000378:metabolism; D012683:Sensory Deprivation / Q000502:physiology*; D016896:Treatment Outcome
D015259:Dopamine Agents; D007980:Levodopa