Disturbance of electrolyte balance in vitreous of chicks with form-deprivation myopia

Purpose: To investigate the changes in the electrolyte and protein concentr ations in the vitreous of 3-week-old chicks with form-deprivation myopia (F DM). Methods: FDM was induced in 2-day-old male white leghorn chicks by covering the left eye with a translucent plastic goggle and leaving the right eye u ncovered to serve as control. After 19 days the animals were euthanized, an d the axial dimensions of the eyes were measured with a caliper in an unfix ed condition. The liquid vitreous and aqueous humor were removed by paracen tesis, and blood was collected from the jugular vein. Sodium, potassium, an d chloride concentrations were determined using ion-selective electrodes. C alcium and phosphate concentrations were determined by colorimetric assays using orthocresol phthalein complexone and bacterial xanthine oxidase, resp ectively. Results: The concentrations of potassium and phosphate were decreased, wher eas chloride concentration was increased in the vitreous of the FDM eyes (P < .01). Sodium and calcium concentrations were similar to those in the con trol eyes. No significant changes in the concentration of electrolytes were observed in the aqueous humor. No significant differences were found in th e protein concentrations in the liquid vitreous, gel vitreous, and aqueous humor. Conclusions: Form-deprivation induced a significant increase of the volume of the Liquid vitreous in the eye of the FDM chick. The increased liquid vi treous of the myopic eye was accompanied by an alteration of the electrolyt e balance, by a mechanism that has not yet been clarified. (C) 2000 Japanes e Ophthalmological Society.