Studies across several species have demonstrated that the developing visual system is influenced by environmental conditions. This study examined the effects of abnormal lighting environments on zebrafish visual behavior. Zebrafish were raised under different lighting conditions from fertilization to 6 days postfertilization (dpf). These conditions included a normal light/dark cycle, constant dark, constant light, as well as exposure to various lighting cycles with intense light. Visual acuity was tested using the optomotor response to black and white vertical stripes of various widths. The results showed that visual acuity of the normal fish improved with age. In addition, fish raised in constant light had significantly lower visual acuity than fish raised under normal lighting conditions. Subjects raised in constant dark showed somewhat lower visual acuity than normal subjects when tested at 12-14 dpf, but the deficits were not as severe as those found in fish raised in constant light. Intense light rearing did not have any substantial effects on visual development, unless it was constant. In conclusion, under normal conditions, zebrafish visual acuity improves with age, supporting previous work on zebrafish development. In addition, zebrafish visual behavior is altered by abnormal lighting conditions; the most severe decrements occur when raised under constant light.