Anatomy of the Eye
- The choroid, which carries blood vessels, is the inner coat between the sclera and the retina.
- The conjunctiva is a clear membrane covering the white of the eye (sclera).
- The cornea is a clear, transparent portion of the outer coat of the eyeball through which light passes to the lens.
- The iris gives our eyes color and it functions like the aperture on a camera, enlarging in dim light and contracting in bright light. The aperture itself is known as the pupil.
- The lens helps to focus light on the retina.
- The macula is a small area in the retina that provides our most central, acute vision.
- The optic nerve conducts visual impulses to the brain from the retina.
- The pupil is the opening, or aperture, of the iris.
- The retina is the innermost coat of the back of the eye, formed of light-sensitive nerve endings that carry the visual impulse to the optic nerve. The retina may be compared to the film of a camera.
- The sclera is the white of the eye.
- The vitreous is a transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens.
Three Types of Eye Removal
EVISCERATION – removal of the inner eye contents, iris and cornea; leaving the sclera behind with the extraocular muscles still attached. Typically, an orbital implant is placed inside the sclera to replace lost eye volume. A scleral shell is fit following this eye surgery.
ENUCLEATION – removal of the eyeball, leaving the remaining orbital contents intact; extraocular muscles are detached and typically reattached to an orbital implant or fat graft. Indications: tumors, infections, blind painful eye, severe trauma. A prosthetic eye is fit following this eye surgery.
EXENTERATION – removal of the contents of the eye socket (orbit) including the eyeball, fat, muscles and other adjacent structures of the eye. The eyelids may also be removed in cases of cutaneous cancers and unrelenting infection. A maxillofacial prosthesis is typically recommended following this surgery.
Should eye removal be necessary, the surgeon will likely place an orbital implant to recover some of the volume lost in the evisceration or enucleation. The orbital implant is attached to the 4 rectus muscles, providing movement of the implant with the fellow eye. Typically, the better the movement of the implant, the better the motility of the prosthetic eye or scleral shell. Implant choices may be dictated by the conditions indicating eye removal, the surgeon’s preference and your post-removal objectives. Most implants are spherical in shape, but other shapes are possible. Implants can also be coated or wrapped in donor sclera or alloderm materials. Below is a list of typical orbital implants:
- Silicone or PMMA Sphere
- Medpore or Porex (porous polyethylene)
- Bio-Eye HA (hydroxyapatite, coral)
- Fat Graft
While implant type is an important decision to one facing enucleation or evisceration, the most important factor is surgical technique. If you are facing the option of eye removal, we recommend that you contact your local ocularist for a recommendation of oculoplastic or ophthalmic surgeons in your area.
Ocular Prosthesis Types
The following types of ocular prosthesis or prosthetic eyes are all available at Northwest Eye Design. Each type has a specific purpose outlined below.
CONFORMER – Conformers help to form the fornices (cul-de-sac) of the anopthalmic or microphthalmic socket. For enucleation or evisceration surgery, conformers are fit approximately 2 weeks post-op to aid in the shaping of the socket for a prosthetic eye or scleral shell. Conformers can help reduce surgical swelling and provide comfort and support for eyelid function. Another purpose of conformers is as a therapeutic prosthesis to expand tissue in cases of microphthalmia, anophtalmia or contracted tissue. Sequential sized conformers can be used to grow the soft tissue and promote bony tissue growth in the orbit. Eye lid function and lengthening of the horizontal fissure opening are major considerations for the use of this type of prosthesis.
PROSTHETIC EYE – A custom prosthetic eye is fit following an enucleation or in cases of anophthalmia. This prosthesis is made of durable medical grade poly-methyl methacrylate (PMMA).
SCLERAL SHELL – A custom scleral shell is fit over an eviscerated globe, nonsighted eye, phthisical globe or microphthalmic globe. A scleral shell functions similar to a prosthetic eye, but is often shaped more like a thin contact.
ORBITAL PROSTHESIS – A orbital prosthesis is fit in cases of exenteration, enophthalmous or contracted tissue when eyelids would not support a typical prosthetic eye. The prosthesis is made of medical grade silicone and attached with adhesive or magnetic attachments.
Possible Conditions Leading to a Prosthetic Eye
The following conditions may lead to the necessity of a custom ocular prosthesis or prosthetic eye. A prosthetic eye is fit over an orbital implant that is attached to the existing eye muscles. A custom eye prosthesis made with an impression-fitting technique should move nearly as well as the tissue in the socket moves, depending on the shape and edges of the prosthesis.
ENUCLEATION – Removal of entire eye globe. An implant is placed in the tenons capsule to replace volume lost due to eye removal. The four extra-ocular rectus muscles are attached to the implant for motility.
BLIND, PAINFUL EYE – Condition in which eye has no light perception (NLP) and is causing pain. Enucleation is indicated to alleviate pain and avoid risk of sympathetic ophthalmia.
OCULAR MELANOMA – A type of cancer arising from the cells of melanocytes found in the eye. Melanoma is the most common type of ocular cancer.
DIABETIC RETINOPATHY – A leading cause of blindness in American adults, this disease is caused by changes in the blood vessels of the retina. The vessels either leak fluid or abnormal vessels grow on the surface of the retina. Often there are no symptoms or pain in the early stages.
TUMORS – Many types of cancers can affect the different structures of the eye. If treatment is unsuccessful in removing the tumor, enucleation is typically indicated.
TRAUMA – The most common cause of eye loss, trauma can take many forms; ruptured globe, penetrating or perforating eye injury, blunt force trauma. When risk of infection or pain is high, enucleation is typically indicated.
RUPTURED GLOBE – Full thickness wound of the eyewall caused by a blunt object or blunt force.
PENETRATING EYE INJURY – Injury to the eye that causes an entrance wound and/or an intraocular foreign body.
PEFORATING EYE INJURY – Injury to the eye that causes an entrance and exit wound, for example a BB pellet that enters in one location and exits another.
CATARACT – A condition in which the lens of the eye becomes cloudy, diminishing vision. Cataracts are commonly associated with aging but also may be precipitated by trauma
INFECTION – Many types of infections can result in the loss of vision or the necessity to remove the eye to protect the rest of the body from infection. Shingles, uveitis, endophthalmitis, corneal ulcer, etc.
VITREOUS HEMORRHAGE – Bleeding in the vitreous cavity in front of the retina. May be caused by either disease or injury.
ENDOPHTHALMITIS – A serious intraocular bacterial infection, often the result of a penetrating eye injury.
Possible Conditions Leading to a Scleral Shell
The following conditions can lead to the necessity of a scleral cover shell. A scleral shell fits over the existing scleral surface of the eye. A scleral shell is often worn full-time. The motility of a scleral shell is typically very good but depends on the shape of the socket and the globe or implant.
EVISCERATION – Removal of the interior portion of the eye. The eye muscles remain attached to the sclera, so implant motility is typically better than with enucleation. An orbital implant is placed inside the sclera to replenish volume.
PHTHSIS, PHTHSIS BULBI, PHTHSICAL EYE – A condition of the eyeball that may result from severe injury when the eye loses function and shrinks in size.
ACCIDENT OR INJURY – Trauma will often lead to a shrunken or disfigured globe, yet not necessarily require removal of the eye. In these cases, a scleral shell can be a great solution, providing comfort and a natural result.
RETINAL DETACHMENT – Separation of the thin vascular retina from its underlying tissue, the retinal pigment epithelium. Can occur with or without trauma.
GLAUCOMA – Increased pressure inside of the eye which damages the optic nerve. It is a leading cause of blindness. In some cases, patients can be born with glaucoma.
CORNEAL DYSTROPHY – A type of eye disease in which to cornea is altered on a cellular level, resulting in loss of its normal function. The cornea can become cloudy and inflamed, affecting vision and the health of the eye.
Leading Causes of Eye Loss in Children
ANOPHTHALMIA – Congenital disorder, the absence of any eyes or ocular structures.
MICROPHTHALMIA – Congenital disorder (occurs at birth), abnormally small eyeball. Anophthalmia and Microphthalmia are both treated with progressive sized ocular conformers, which help stimulate the muscle and bone of the orbit, promoting orbital and soft tissue growth. Clear ocular conformers are custom made to fill as much of the socket as possible. These conformers are not painted to look like a normal eye because they are changed too frequently. Every few weeks a child will progress to a larger size conformer until symmetry is achieved, or about 1-2 years of age. Once a child is wearing a custom prosthetic eye, the eye will be enlarged regularly to keep symmetry with the natural eye. Children will be fit with a new prosthesis every 3-4 years. The causes of these conditions may include genetic mutations, abnormal chromosomes or possible environmental factors, but often the cause is unknown.
RETINOBLASTOMA – Retinoblastoma is a type of cancer that forms in the retina. The disease usually occurs in children younger than 5 years and may be in one eye or in both eyes. In some cases, the disease is inherited from a parent. It is typically discovered by a white or yellow “glow” of light in the pupil, when light shines off the tumor. In some cases, enucleation is indicated, and a prosthetic eye will be fit about 6-8 weeks after surgery.
RETINOPATHY OF PREMATURITY (ROP) – Congenital condition that affects children born prematurely. The retina is affected by vessels that grow abnormally, resulting in a retinal detachment. ROP is a leading cause of visual impairment or blindness in children.
COLOBOMA – Congenital anomaly in which some of the structures of the eye are absent due to incomplete formation in utero.
PERSISTENT HYPERPLASTIC PRIMARY VITREOUS (PHPV) – Condition in which a vascularized membrane is present behind the lens, often resulting in microphthalmia, congenital cataracts and sometimes glaucoma. Often discovered by observation of a leukocoria (“white pupil”).
TRAUMA – In children, trauma to the eye can take the form of sharp toys, BB guns, paint guns, rocks, darts, bungie cords, pencils, sport injuries or chemical burns. The use of safety glasses during any activity involving potential risk to the eyes is highly recommended.
COAT’S DISEASE – A progressive condition of the retinal capillaries, often resulting in retinal detachments. Affects kids under 10, typically males.
Eye Care Specialists
WHAT IS AN OPTHALMOLOGIST?
An ophthalmologist is either a medical doctor (MD) or an osteopathic physician (DO) who specializes in comprehensive eye care and provides examinations, diagnosis, and treatment for a variety of eye disorders. Ophthalmologists are skilled in all facets of eye care, from prescribing eyeglasses or contact lenses to performing intricate eye surgery. Many also choose to specialize in one particular disease or portion of the eye (i.e., glaucoma specialist or cornea specialist).
WHAT IS AN OPTOMETRIST?
An optometrist is an eye doctor who has earned the degree of Doctor of Optometry (OD). Optometrists examine eyes for both vision and health problems, and correct refractive errors by prescribing eyeglasses and contact lenses. Some optometrists also provide low vision care and vision therapy.
WHAT IS AN OPTICIAN?
An optician is a technician trained to design, verify and fit eyeglass lenses and frames, contact lenses, and other devices to correct eyesight. They use prescriptions supplied by ophthalmologists or optometrists, but do not test vision or write prescriptions for visual correction
WHAT IS AN OCULARIST?
An ocularist is a healthcare provider who specializes in the fabrication and fitting of ocular prosthetics for people who have lost an eye or eyes due to trauma or illness. Ocularists provide long-term care for their patients with prosthetic care instruction, tissue examinations, ongoing maintenance and replacement of prosthetic eyes and scleral shells.
WHAT IS A BCO?
A Board Certified Ocularist (BCO) is an ocularist who has passed the competency examination by the National Examining Board of Ocularists (NEBO), maintains continuing education requirements and is recertified every six years.
WHAT IS A BADO?
A Board Approved Diplomate Ocularist (BADO) is an ocularist who has graduated from the education program of the American Society of Ocularists (ASO), certified by the National Examining Board of Ocularists and approved by the ASO Board of Directors.
WHAT IS A LICENSED OCULARIST?
A Licensed Ocularist in the state of Washington has completed five years (10,000 hours) of apprenticeship training under the direct supervision of a Licensed Ocularist and completes an examination by the Washington State Department of Health.
WHAT IS AN ANAPLASTOLOGIST?
An anaplastologist makes and fits orbital, facial and somatic prosthetics.