Ocular size and shape in lens-induced Myopization in young Guinea pigs

Abstract

Background Lens-induced myopization in guinea pigs has been used as model for the process of myopization in humans. It has not been explored yet whether the change in globe shape in eyes undergoing myopization is similar in experimental myopia in guinea pigs and in clinical myopia in patients. Methods The study included 70 guinea pigs (age:2–3 weeks) equally divided into a study group with lens-induced myopization for 5 weeks, and a control group wearing goggles with no refractive power. The globe diameters were measured using a microcaliper after enucleation. Results The horizontal globe diameter (9.19 ± 0.15 mm versus 9.15 ± 0.18 mm; P = 0.25) and vertical globe diameter (9.02 ± 0.11 mm versus 8.99 ± 0.14 mm; P = 0.29) did not differ significantly between the study group and control group. The sagittal diameter was significantly longer in the study group (8.96 ± 0.15 mm versus 8.84 ± 0.14 mm; P = 0.001). While the vertical and horizontal globe diameters were correlated with each other in a ratio of approximately 1:1 (non-standardized regression coefficient B:0.94;95% confidence interval (CI):0.73,1.15), the steepness of the regression lines of the associations of both diameters with the sagittal diameter were flatter (horizontal to sagittal diameter: B: 0.64; 95% CI: 0.44,0.83; vertical to sagittal diameter:B:0.55;95% CI:0.41,0.69). Correspondingly, the ratios of horizontal-to-sagittal globe diameter and of vertical-to-sagittal globe diameter decreased ( P < 0.001) with longer sagittal diameter. Conclusions For each mm axial elongation in young guinea pigs the horizontal globe diameter increased by 0.64 mm (95%CI:0.44,0.83) and the vertical diameter by 0.55 mm (95% CI:0.41,0.69), indicating that the globe enlargement occurred predominantly in the sagittal direction. Axial elongation in guinea pigs led to a similar relative change in ocular shape as in humans.

Altered Expression of GJD2 Messenger RNA and the Coded Protein Connexin 36 in Negative Lens–induced Myopia of Guinea Pigs

“…It should be noted that the initial age of guinea pigs in the current study was 4 weeks, which is older than that of the animals in previous related studies, whereas the treatment duration was 3 weeks, which is shorter than that of other studies. 37 , 43 – 51 These differences may account, at least in part, for the failure of the guinea pigs in the experimental group to fully compensate to the imposed hyperopic defocus at the end of the study, which was also an intended outcome. There has been one other study reporting on changes in relative GJD2 messenger RNA expression and Cx36 protein in the retina of guinea pigs, in this case involving form deprivation myopia.…”

In vivo Imaging of Retina and Choroid in Guinea Pigs

“…We measured the axial length of both eyes in each animal by ocular sonographic biometry (A/B-mode scan; oscillator frequency: 11 MHz; Quantel Co., Les Ulis, France) under topical anesthesia (oxybuprocaine hydrochloride eye drops; Santen Co., Osaka, Japan). The sound conducting velocity was set to be 1,557, 1,723 and 1,540 m/s for the measurement of the anterior chamber, lens and vitreous chamber, respectively ( 4 ). Ten measurements were taken for each eye, and the mean values were used for further statistical analysis.…”

“…Axial myopia is characterized by the elongation of the ocular axial length. Previous studies have evaluated the morphometric changes of the sclera and choroid in axially elongated, myopic eyes of humans and animals (4)(5)(6). These investigations revealed that the thickness of the sclera and choroid progressively decreased with axial elongation, while the thickness of the retina in the macular region was independent of axial length (7)(8)(9).…”

Digital measuring the ocular morphological parameters of guinea pig eye in vivo with Python

“…After measurement, the eccentricity of the cornea in the coronal view in vivo was 0.36±0.16. Obviously, the routine method used in human, namely, measuring corneal astigmatism in horizontal and vertical view, was not suitable to guinea pigs [22,25,27] . Until now, there is still not a convenient and effective instrument to measure the refraction of guinea pig eyes.…”