This study gives a comprehensive description of eyelids movement in little owl and discusses the impact of some surrounding conditions in kinetic performance of these eyelids. The present study used the video's recording technique to record the kinetic activity of lids, beside the anatomical, and the histological studies of the eyelids structure. The present authors found that the fundemental eyelids movements can be uniquely and reliably characterized by their anatomical relationships that confirmed also via video record of kinetic performance of these eyelids. The results show that levator palpebrae muscle split into many directions as a main generate motor to increasing the movement of the upper lid. In other side, the contraction of Depressor palpebral inferioris muscle together with the active upward forces of levator palpebrae muscle resultin g in opening the eye. While, the closure of lids arise from the passive downward forces and relaxation of the levator palpebrae and Depressor palpebral inferioris muscle as well as, the cooperation action of retractor anguli oculi lateralis and medialis muscle. The results also recorded that NM movement is reversely proportion to the level of kinetic of other eyelids. . The mobility of Nm in little owl occurs under effect artificially external stress. These anatomical data and sequence video records have confirmed that the upper eyelid move more compare to other lids. The present authors also suggest that the mobility of lids may stimulate through external pressure force of some surrounding structure like periorbital sheet. Also, the histological study exhibited that the structure of two eyelids is very similar in the little owl and the variability are showing in the number of cell layers that forms their epithelium of skin and palpebral surfaces, the distribution of pigment granules within them, as well as, the degree of keratinization on their surface.

This study gives a comprehensive description of eyelids movement in little owl and discusses the impact of some surrounding conditions in their kinetic performance. The present study used the video's recording technique to record the kinetic activity of eyelids, besides the anatomical and histological studies of the eyelid's structure. The fundamental eyelid movements can be uniquely and reliably characterized by their anatomical relationship that was confirmed via video recording for their kinetic activity. The levator palpebrae muscle is considered a main generating motor for the upper eyelid; in the little owl, this muscle splits into multiple directions and is distinguished from the levator palpebrae superioris (Lps) and the levator anguli oculi (Lao) muscle. That anatomical pattern of insertion increases the movement of the upper lid. On the other side, the contraction of depressor palpebrae inferioris (Dpi) muscle and the active upward forces of levator palpebrae muscle help in increasing the opening of the eye's fissure. However, the closure process is produced from the passive downward forces and relaxation of the levator palpebrae superioris (Lps), levator anguli oculi (Lao), and depressor palpebrae inferioris muscle, as well as the contraction of retractor anguli oculi lateralis (Raol) and medialis (Raom) muscle. The present results also recorded that nictitating membrane's (Nm) movement is reversely proportionate to the level of kinetic of other eyelids. The mobility of Nm in little owl occurs under the effect of artificial external stress. These anatomical data and sequence video recordings have confirmed that the upper eyelid moves more compared to other eyelids. The authors also suggest that the mobility of eyelids may get stimulated through external pressure force of some surrounding structure like the periorbital sheet. Also, the histological study exhibited that the structure of two eyelids is very similar in the little owl and the variability is showing in the number of cell layers that forms their epithelium of skin and palpebral surfaces, the distribution of pigment granules, and degree of keratinization on their surface. That variability in the histological characters of eyelids may counteract the abrasive forces occurring during the opening and closing processes.