The eye is a specialised organ which collects and transmits visual information from the environment to the brain. A ~2.5 cm diameter sphere, it comprises of an anterior (cornea to lens) and a posterior segment (lens to optic nerve). Entering light is refracted by the cornea and lens onto the retina where it is detected by photoreceptors. Protected by the bony orbit, eyelids and lacrimal … Continue reading Eye

The upper and lower eyelids are movable folds which protect the eye from foreign material. Superficial to deep, layers of the eyelids generally include skin, loose connective tissue, fibres of the orbicularis oculi, the tarsal plates (Meibomian glands within) and conjunctiva. The corners formed by the upper and lower lids are the medial and lateral canthi while the opening in between is the palpebral fissure. … Continue reading External eye: eyelids, conjunctiva

The lacrimal apparatus is the system for tear production and drainage. Tears contribute to the tear film covering the eye and is critical for providing nourishment to the cornea, providing a medium for oxygen to diffuse through, washing out foreign material and as a source of antibacterial enzymes. Tears are produced in the lacrimal gland, found in the the lacrimal fossa, a depression at the superolateral … Continue reading Lacrimal apparatus

The ophthalmic artery, the first major branch of the internal carotid artery, enters the orbit via the superior orbital fissure, whereupon it gives off the central artery of the retina and branches to the extraocular muscles. It also ascends on the lateral surface of the optic nerve and gives the lacrimal artery. The lacrimal artery has a recurrent meningeal branch that anastomoses with the anterior branch … Continue reading Eye blood vessels

There are three groups of the muscles of the eye: Intraocular: ciliary muscle (changes lens shape) and pupillary dilators/constrictors Extraocular muscles of eye movement: 4 recti and 2 oblique muscles Extraocular elevator of the upper eyelid: levator palpebrae superioris The superior division of the oculomotor nerve (CN III) innervates levator palpebrae superioris and the superior and medial recti while the inferior division innervates the inferior … Continue reading Eye muscles