Inhibitory effect of blue light intervention on lens-induced myopia development in guinea pigs and the mechanism of cone density change

Objective

To observe the effects of blue light intervention on the development of optical defocus-induced myopia in guinea pigs and investigate its underlying mechanisms.

Methods

Forty-eight normal-grade two-week-old tricolor guinea pigs were randomly divided into a blue light group and a white light group, with 24 animals in each group.The right eye of guinea pigs was fitted with a -5.00 D lens to establish an optical defocus model as the experimental eye, while the left eye served as the control without any covering.Before the experiment and after 8-week intervention, the refractive power of guinea pigs was measured by streak retinoscopy.The anterior chamber depth, lens thickness, and axial length were measured by A-scan ultrasonography.Corneal curvature radius was determined using a keratometer.After 8-week intervention, the guinea pigs were euthanized through overanesthesia, and the right eyeballs were enucleated and the retinas were isolated.The density of S and M cone cells of the guinea pig retinal sections were observed via immunofluorescence staining.The expression of retinal retinoic acid was assessed by high-performance liquid chromatography.The expressions of retinoic acid receptor (RAR-β) in the retina and matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase-2 (TIMP-2), and type Ⅰ collagen in the sclera were detected by real-time fluorescence quantitative PCR.Changes in scleral thickness were observed through hematoxylin-eosin staining.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.The study protocol was approved by the Ethics Committee of Eye and ENT Hospital of Fudan University (No.2022ETKLD10032).

Results

After 8 weeks of intervention, guinea pigs in the blue light group showed (0.63±0.12)D of relative hyperopia and a deceleration of axial elongation by (0.08±0.00)mm compared with the white light group in the right eye.In the left eye, guinea pigs in the blue light group showed (0.42±0.09)D of relative hyperopia and a deceleration of axial elongation by (0.08±0.00)mm compared with the white light group.The guinea pigs in blue light group showed (1.52±0.09)D of myopia in the right eye compared with the left eye, with an increase in axial elongation of (0.06±0.00)mm.The guinea pigs in white light group showed (1.66±0.07)D of myopia in the right eye compared with the left eye, with an increase in axial elongation of (0.13±0.00)mm, and the differences were statistically significant (all at P<0.05). The density of M cone cells was lower and density of S cone cells was higher in the blue light group in the dorsal and ventral sides of the retinal sections compared with the white light group, showing statistically significant differences (t=32.33, 52.23, 42.09, 25.02; all at P<0.05). The deceleration of myopia progression in the blue light group was strongly positively correlated with the increase in S cone cell density on the ventral side (r=0.95, P<0.01). The expression levels of retinoic acid, RAR-β, and MMP-2 were decreased, and expression levels of TIMP-2 and type Ⅰ collagen were increased in blue light group compared with the white light group, showing statistically significant differences (t=18.73, 7.45, 3.72, 6.19, 9.03; all at P<0.05). The scleral thickness in the blue light group was (125.0±7.8)μm, which was significantly thicker than (102.0±6.3)μm in the white light group (t=26.93, P<0.05).

Conclusions

Blue light intervention can inhibit the progression of defocus-induced myopia in guinea pigs.Refractive power changes in guinea pigs may be influenced by alterations in retinal cone cell density, retinoic acid expression, and scleral collagen expression.

Myopia; Guinea pigs; Retinal cone photoreceptor cells; Retinoic acid; Blue light; Defocus-induced myopia