ABSTRACT
The lids comprise skin, connective tissue, the orbicularis oculi and the tarsal plate, with multiple meibomian glands opening posterior to the lashes and lined with conjunctiva, which is reflected onto the sclera. Tears are swept across the globe by the lids and evaporate or pass into the upper and lower lid puncta, and then into the canaliculi to join the common canaliculus, which passes into the lacrimal sac under the medial canthal tendon. The uvea comprises the iris, ciliary body and vascular choroid. Photoreceptor cells in the outer retina sense light and send impulses to retinal ganglion cells in the inner retina via bipolar cells. The retinal pigment epithelium underlies the photoreceptors and is responsible for reprocessing of photopigments. Dermoid cysts account for about half of childhood orbital neoplasms and consist of keratinised epithelium and adnexal structures such as sweat glands and hair follicles.
