Health Information Management

ICD-10 anatomy refresher: The eyes have it

JustCoding News: Outpatient, June 27, 2012

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Editor’s note: With the increased specificity required for ICD-10-CM coding, coders need a solid foundation in anatomy and physiology. To help coders prepare for the upcoming transition, we will provide an occasional article about specific anatomical locations and body parts as part of a larger series for ICD-10-CM preparation. This month’s column addresses the anatomy of the eye.

The human eye may be small—only 1 inch in diameter on average—but it is a very complex sensory organ. Coders must understand the structures of the eye itself as well as accessory visual structures (the adnexa) to select appropriate codes in ICD-9-CM and ICD-10-CM/PCS.

Light enters through the clear covering of the eye, called the cornea. The pupil opens and closes to control the amount of light that enters the eye.

After light enters the eye, it strikes the retina, which is a series of light-sensitive cells lining the back of the eye. The retina captures the light like camera film, and then it converts the light waves into nerve impulses. The optic nerve then carries those impulses to the visual cortex in the brain.

Around the eyeball
Each eye sits inside an orbit, which is a depression in the anterior part of the skull. The walls of the orbit protect the eyeball and optic nerve. The orbit also provides an anchor for the muscles that move the eyeball.

The conjunctiva is a transparent mucus membrane that lines the inside of the eyelid and the front surface of the eyeball excluding the cornea.

The sclera is the fibrous outer layer of the eyeball. It protects the inner layers of the eye and gives the eye its shape.

Anterior segment of the eyeball
The anterior segment of the eye includes the internal structures and anatomy that encompass approximately one-third of the eye stretching from the cornea to the back of the lens.

The cornea is the clear outer covering of the eye that transmits and focuses light as it enters. The cornea is composed mainly of connective tissue with a thin layer of epithelium on the surface. It includes few cells and no blood vessels; however, it does contain a large number of nerve fibers.

The anterior chamber of the eye is located between the cornea and the iris. It includes the aqueous humor, which is a clear fluid that provides nutrients to the cornea and the lens. In patients with glaucoma, the fluid does not drain properly, and intraocular pressure increases. This can damage the optic nerve and result in blindness.

To report glaucoma in ICD-10-CM, the coder will need documentation of the type of glaucoma and whether it is bilateral or affects only one eye, and if so, which one. For example, coders could report ICD-10-CM code H40.123 (low-tension glaucoma, bilateral) or H40.822 (hypersecretion glaucoma, left eye) depending on the patient's condition and the physician documentation.

The posterior chamber lies behind the iris and in front of the lens. The iris, which is located in the posterior chamber, is the colored part of the eye that surrounds the pupil. It lies between the cornea and the lens, and it widens or narrows the pupil to control the amount of light entering the eye. The pupil itself is generally circular.

The lens is located behind the pupil and focuses light onto the retina.

Posterior compartment of the eye
The vitreous humor is a clear, jelly-like substance ¬between the lens and the retina. It makes up approximately 80% of the eye's volume. It keeps the eyeball from collapsing and permits light to penetrate to the retina.

As people age, the vitreous humor gradually shrinks, which can lead to a posterior vitreous detachment.
To report the procedure to repair the posterior vitreous in the right eye using a percutaneous approach, the coder would report the ICD-10-PCS code 08Q43ZZ.

Back of the eye
The retina lines the back of the eye and is composed of 10 layers, from the outside (nearest the blood vessel-enriched choroid) to the inside (nearest the gelatinous vitreous humor). Light passes through nine clear layers of the retina and is brought into focus in an upside-down image on the outermost retinal layer (i.e., the pigmented epithelium). The image is reflected back onto the adjacent second layer on which the rods and cones are located. Rods detect dim light and movement, while cones detect color and bright light.

To report the restoration of the retina in the right eye to its normal function using a percutaneous approach, the ICD-10-PCS code is 08QE3ZZ.

The macula is the small, yellowish central portion of the retina that allows people to see objects with great detail. The center of the macula is called the fovea ¬centralis, an area where all of the photoreceptors are cones.

The choroid is the center layer of the eyeball made up of dark pigments that prevent incoming light from scattering.

Nerves of the eye
The optic nerve acts like a cable connecting the eye with the brain. As the optic nerve leaves the back of the eye, it travels to the optic chiasm, located just below and in front of the pituitary gland. The optic nerve eventually connects to the visual cortex of the brain.

Other nerves supply impulses to the extraocular muscles and the lacrimal glands. Some of them also continue on to the face to supply sensation to the skin of the eyelids and forehead. Some of the other nerves are:

  • Supratrochlear: runs over the eyeball and out of the orbit to supply sensation to the middle of the forehead
  • Supraorbital: runs forward, out of the orbit, and turns upward on the frontal bone to the upper eyelid
  • Nasocilliary: part of the ophthalmic nerve, supplies sensation to the ethmoidal sinuses, nasal cavity, and eyeball
  • Ophthalmic: branch of the trigeminal nerve that supplies sensation to the eyeball, conjunctiva, part of the lining of the nose, the eyelids, and forehead
  • Abducent: supplies sensation to the lateral rectus muscle
  • Oculomotor: supplies all of the muscles of the eye ¬except the superior oblique and lateral rectus
  • Trochlear: supplies the superior oblique muscle

For paralytic strabismus, coders will need documentation of the specific nerve that is suffering with palsy and which eye is affected. For example, coders would report ICD-10-CM code H49.01 for third (oculomotor) nerve palsy of the right eye or H49.22 for sixth (abducent) nerve palsy of the left eye.

Extraocular muscles
Six extraocular muscles work together to turn or rotate the eye about its vertical, horizontal, and antero-posterior axes. The muscles attach to the sclera on one end and the skull on the other end. Each muscle is innervated by a different nerve.

The muscles are named for their location as follows:

  • Medial rectus: moves the eye inward, toward the nose (adduction)
  • Lateral rectus: moves the eye outward, away from the nose (abduction)
  • Superior rectus: primarily moves the eye upward ¬(elevation) and inward as well as rotates the top of the eye toward the nose (intorsion)
  • Inferior rectus: primarily moves the eye downward (depression) and also rotates the top of the eye away from the nose (extorsion) and inward
  • Superior oblique: primarily rotates the top of the eye toward the nose and also moves the eye downward and outward
  • Inferior oblique: primarily rotates the top of the eye away from the nose and also moves the eye upward and outward

The four rectus muscles control the eye's movements from left to right and up and down. The two oblique muscles move the eye inward and outward. Many ICD-10-CM codes pertain to disorders of the movement of the eye.

The eyelid
The eyelids protect the front of the eyeball from injury and help regulate how much light reaches the eye.
"Palpebral" (and "blepharo") means relating to the eyelids. The eyelid's key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep, and the blink reflex protects the eye from foreign bodies.

The eyelids consists of:

  • Skin and subcutaneous tissue
  • Orbicularis oculi muscle: muscle in the face that ¬closes the eyelids
  • Levator palpebrae superioris muscle: retracts the eyelid to open the eye either voluntarily or involuntarily
  • Tarsal plates: comparatively thick, elongated plates of dense connective tissue, found in each eyelid; they contribute to its form and support
  • Orbital septum: a membranous sheet that acts as the anterior boundary of the orbit; it extends from the orbital rims to the eyelids and forms the fibrous portion of the eyelids
  • Conjunctiva

The meibomian glands lie within the eyelid and secrete the lipid part of the tear film. The eyelashes help protect the eye from dust and foreign debris, as well as from perspiration.

Editor’s note: This article was originally published in Briefings on APCs. Email your questions to Senior Managing Editor Michelle A. Leppert, CPC-A, at

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