Layers in Ophthalmology


epithelium, Bowman's layer, stroma proper, Descemet's membrane, and endothelium


episclera, scleral stroma proper, and lamina fusca


1. Retinal pigment epithelium
2. Photoreceptor cell layer
3. External limiting membrane
4. Outer nuclear layer
5. Outer plexiform layer
6. Inner nuclear layer
7. Inner plexiform layer
8. Ganglion cell layer
9. Nerve fiber layer
10. Internal limiting membrane

Tear Film

mucinous, aqueous, and lipid layers

The tear film is an exceedingly complex mixture of secretions from multiple tissues and epithelia (Fig. 15.1) and consists of four layers (Fig. 15.2). The innermost layer is a glycocalyx that extends from the superficial layer of the ocular surface epithelia. The second is a mucous layer that covers the glycocalyx and may mix with the third aqueous layer. The outermost layer contains lipids. Similarly to mucous and aqueous layers, aqueous and lipid layers may mix. Production and function of tear film layers are distinct and will be presented separately.

Extra-ocular Muscles

an outer orbital layer composed of myofibers of extremely small cross-sectional area and an inner global layer with myofibers larger than in the orbital layer but still extremely small compared to non-cranial skeletal muscle

Bruch's membrane

1) interrupted basement membrane of the choriocapillaris, (2) outer collagenous zone, (3) elastic layer, (4) inner collagenous zone, and (5) basement membrane of the RPE


suprachoroid lamina (lamina fusca)
choroidal stroma
bruch’s membrane (basal lamina)

(The choroid is composed of the choriocapillaris layer, the medium vessels layer (Sattler's layer) and the outer layer of large vessels (Haller's layer).)

Trabecular meshwork

uveal, corneoscleral, and juxtacanalicular.


the dura mater, arachnoid layer, and pia mater.

Facial mimetic muscles (4)

A superficial layer consists of the orbicularis oculi, zygomatic minor, and depressor anguli oris. The second layer contains the platysma, depressor labii inferioris, the levator labii superioris alaeque nasi, and zygomatic major muscles. The third layer consists of the levator labii superioris and orbicularis oris. Finally, the deepest layer consists of the mentalis, the levator anguli oris, and the buccinator. Branches of the facial nerve supply the first three layers of muscles from the underside, while the deepest layer is innervated from the outer surface.


Iris layers are described in many ways as per different references: I am quoting all here -

The Iris can be divided into four layers: (1) the anterior border layer, (2) stroma and sphincter muscle, (3) ante-rior epithelium and dilator muscle, and (4) posterior epithelium.

The iris is composed of five layers: the anterior border layer, the iris stroma, the muscular layer, the anterior pigment epithelium, and the posterior pigment epithelium. The clump cells of Koganei are part of the iris stroma. The dilator and sphincter muscles make up the muscular layer of the iris, which is anterior to the iris pigment epithelium. The color of the iris is determined by the number and size of melanin pigment granules of the stromal melanocytes.

The iris can be divided into two main layers: the posterior leaf and the anterior leaf. The posterior iris leaf contains the dilator muscle, the sphincter muscle, and the posterior pigmented epithelium. From a front view of the iris, the dilator muscle is located circumferentially, in the midperiphery of the iris.

Lateral geniculate nucleus

The primate lateral geniculate nucleus has six layers: layers 1 and 2 consist of large (magnocellular) cells, and layers 3, 4, 5, and 6 consist of small (parvocellular) cells.

- compiled & published by Dr Dhaval Patel MD AIIMS