The Effect of Zeaxanthin on the Visual Acuity of Zebrafish

Abstract

Oral supplementation of carotenoids such as zeaxanthin or lutein which naturally occur in human retina have been shown to improve vision and prevent progression of damage to advanced AMD in some studies. The zebrafish eye shares many physiological similarities with the human eye and is increasingly being used as model for vision research. We hypothesized that injection of zeaxanthin into the zebrafish eye would improve the visual acuity of the zebrafish over time. Visual acuity, calculated in cycles per degree, was measured in adult zebrafish to establish a consistent baseline using the optokinetic response. Zeaxanthin dissolved into phosphate buffered saline (PBS) or PBS only was injected into the anterior chamber of the right and left eyes of the Zebrafish. Visual acuities were measured at 1 week and 3, 8 and 12 weeks post-injection to compare to baseline values. Repeated measures ANOVA was used to compare visual acuities between fish injected with PBS and zeaxanthin. A significant improvement in visual acuity, 14% better than before the injection (baseline levels), was observed one week after injection with zeaxanthin (p = 0.04). This improvement peaked at more than 30% for some fish a few weeks after the injection and improvement in vision persisted at 3 weeks after injection (p = 0.006). The enhanced visual function was not significantly better than baseline at 8 weeks (p = 0.19) and returned to baseline levels 12 weeks after the initial injection (p = 0.50). Zeaxanthin can improve visual acuity in zebrafish eyes. Further studies are required to develop a better understanding of the role zeaxanthin and other carotenoids play during normal visual function.

Fig 1. Positioning zebrafish in the OKR device.

The fish is positioned upright with the eyes approximately 7.3cm from the edge of the drum (inset image). The fish is given time to recover from anesthesia while positioned within the cylindrical tank of water.

Fig 2. Schematic for calculating cpd.

The head in this figure is enlarged for demonstration purposes.

Fig 3. Injection of PBS with 0.001% Phenol Red into the Zebrafish Eye.

From left to right, just prior to the time of injection the eye is clear. Once both eyes have been injected (a period of about 3 minutes), the dye is visible in the anterior chamber. After 30 minutes the dye has been pumped to the vitreous via the normal aqueous flow dynamics of the zebrafish eye.

Fig 4. Normalized visual acuity measurements represented as a percent of baseline after injections.

The values presented are mean percentages normalized to baseline means for each group. Control fish (n = 17) did not receive an injection and their visual acuity did not significantly (N.S.) change. The PBS group (n = 13) received an equivalent volume of PBS injected into their eyes and did not show a significant change compared to baseline post injection (PI). The group injected with zeaxanthin (n = 13) had an increased visual acuity at 1 and 3 weeks PI and then saw a return to approximate baseline acuity levels by 12 weeks. Error bars represent normalized standard errors. The dotted line identifies the normalized starting visual acuity for each group.