Pars plana

The pars plana (also known as orbicularis ciliaris ^[1]) (Latin: flat portion) is part of the ciliary body in the uvea (or vascular tunic), the middle layer of the three layers that comprise the eye.

It is about 4 mm long, located near the junction of the iris and sclera, and is scalloped in appearance.

The pars plana may not have a function in the post-fetal period, making this a good site of entry for ophthalmic surgery of the posterior segment of eyeball; this surgery is known as pars plana vitrectomy.

References

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Anatomy of the globe of the human eye

Fibrous tunic
(outer)

Sclera	Episcleral layer Schlemm's canal Trabecular meshwork
Cornea	Limbus layers Epithelium Bowman's Stroma Dua's layer Descemet's Endothelium

Uvea / vascular
tunic (middle)

Choroid	Capillary lamina of choroid Bruch's membrane Sattler's layer
Ciliary body	Ciliary processes Ciliary muscle Pars plicata Pars plana
Iris	Stroma Pupil Iris dilator muscle Iris sphincter muscle

Retina (inner)

Layers	Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium
Cells	Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Retina ganglion cell (Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell) → Diencephalon: P cell, M cell, K cell, Muller glia
Other	Macula Perifoveal area Parafoveal area Fovea Foveal avascular zone Foveola Optic disc Optic cup Ora serrata

Anatomical regions
of the eye

Anterior segment	Adnexa (Eyebrow, Eyelid, Conjunctiva, Lacrimal system, Orbit) Fibrous tunic Anterior chamber Aqueous humour Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn
Posterior segment	Vitreous chamber Vitreous body Retina Choroid

Other

• Keratocytes
• Ocular immune system
• Optical coherence tomography
• Eye care professional
• Eye disease
• Refractive error
• Accommodation
• Physiological Optics
• Visual perception

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