Scleral reinforcement surgery
Encyclopedia
Scleral reinforcement is a surgical procedure used to reduce or stop further macular damage caused by high myopia
, which often can be degenerative.
is one of the leading causes of blindness in the world . It is caused by both genetic and environmental factors , such as mechanical stretching, excessive eye work and accommodation
, as well as an elevated intraocular pressure
. It affects both children and adults. In many cases, myopia will stabilize once the growth process has been completed, but in more severe chronic cases, loss of vision can occur.
Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by posterior sclera
elongation and thinning (at least 25.5 mm to 26.5 mm) and high refractive errors of at least -5 to -7.5 diopters with an increase per year . There may also be changes in the fundus
, including posterior staphyloma, caused by the eye growing posteriorly and losing its spherical shape . Since enlargement of the eye does not progress at a uniform rate, abnormal protrusions of uveal tissue may occur through weak points in the eye. Staphyloma
is marked by a thinning of sclera collagen bundles and decreased number of collagen striations. It correlates with a large posterior temporal bulge. Curtin described five varieties, based on size, shape, and change in appearance of the optic nerve
and retinal vessels, but the posterior pole type is the most common . As the posterior staphyloma enlarges, choroidal tissue becomes thin and Bruch's membrane
begins to break, creating lesions called lacquer cracks. Neovascularization
may occur, causing blood vessels to protrude through the cracks and leak in the space underneath the photoreceptor cell layer. This hemorrhaging can lead to scarring and macular degeneration
, causing vision to gradually deteriorate . If left untreated, high myopia can cause retinal detachment
, glaucoma
, and a higher risk of cataracts.
for sclera reinforcement . Curtin promoted the use of donor-sclera grafting for reinforcement . In 1976, Momose first introduced Lyodura
, a material derived from processed cadaver dura mater . At this point, many different surgeons made alterations to existing techniques. Snyder and Thompson modified reinforcement techniques and had positive outcomes , while others, like Curtin and Whitmore, expressed dissatisfaction with their negative conclusions .
and prevent further progression of the posterior staphyloma. The strain is reduced, although damage from the pathological process cannot be reversed. By stopping the progression of the disease, vision may be maintained or improved.
and could result in optic nerve atrophy. In single strip support, the material covers the posterior pole vertically between the optic nerve and insertion of the inferior oblique muscle. Often, this method is preferred, since it is the easiest method for placement, provides the widest area of support, and reduces the risk of optic nerve interference .
, Lyodura
(lyophilized human dura) , Gore-Tex
, Zenoderm (porcine skin dermis), animal tendons, and donor's or cadaver’s sclera . Human sclera is thought to offer the best support, as well as Lyodura, which is biologically compatible with the eyeball and has sufficient tensile strength. Artificial materials, such as nylon or silicone, are not suggested . Sclera from cadaver’s or animal tendons run the risk of being rejected.
and Tenon's capsule are incised about 6 mm from the corneal limbus
. The lateral
, superior
, and inferior
recti muscles are separated using a strabismus hook. The connecting tissue is then separated from the posterior pole, as well as the inferior oblique muscle. The strip of material is passed under the separated muscles, and pushed down deeply towards the posterior pole. Both ends of the material strip are crossed over the medial rectus muscle and sutured to the sclera on the medial side of the superior and inferior recti muscles. The conjunctiva and Tenon's capsule are then closed together.
, choroidal edema
or hemorrhage, damage to the vortex vein, and transient motility problems .
There is also controversy regarding in what developmental stage this procedure should be performed . Some feel efforts should be made as soon as possible to arrest progression in children. Others feel that the procedure should only be done in cases where high myopia is indicated with macular changes. Furthermore, different surgeons have particular criteria that must be met by patients in order to receive surgery.
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
, which often can be degenerative.
High Myopia
MyopiaMyopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
is one of the leading causes of blindness in the world . It is caused by both genetic and environmental factors , such as mechanical stretching, excessive eye work and accommodation
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
, as well as an elevated intraocular pressure
Intraocular pressure
Intraocular pressure is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma...
. It affects both children and adults. In many cases, myopia will stabilize once the growth process has been completed, but in more severe chronic cases, loss of vision can occur.
Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by posterior sclera
Sclera
The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...
elongation and thinning (at least 25.5 mm to 26.5 mm) and high refractive errors of at least -5 to -7.5 diopters with an increase per year . There may also be changes in the fundus
Fundus (eye)
The fundus of the eye is the interior surface of the eye, opposite the lens, and includes the retina, optic disc, macula and fovea, and posterior pole. The fundus can be viewed with an ophthalmoscope. The term may also be inclusive of Bruch's membrane and the choroid.The color of the fundus varies...
, including posterior staphyloma, caused by the eye growing posteriorly and losing its spherical shape . Since enlargement of the eye does not progress at a uniform rate, abnormal protrusions of uveal tissue may occur through weak points in the eye. Staphyloma
Staphyloma
A staphyloma is an abnormal protrusion of the uveal tissue through a weak point in the eyeball. The protrusion is generally black in colour, due to the inner layers of the eye...
is marked by a thinning of sclera collagen bundles and decreased number of collagen striations. It correlates with a large posterior temporal bulge. Curtin described five varieties, based on size, shape, and change in appearance of the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
and retinal vessels, but the posterior pole type is the most common . As the posterior staphyloma enlarges, choroidal tissue becomes thin and Bruch's membrane
Bruch's membrane
Bruch's membrane is the innermost layer of the choroid. It is also called the vitreous lamina, because of its glassy microscopic appearance.It is 2–4 μm thick.-Layers:Bruch's membrane consists of five layers :...
begins to break, creating lesions called lacquer cracks. Neovascularization
Neovascularization
Neovascularization is the formation of functional microvascular networks with red blood cell perfusion. Neovascularization differs from angiogenesis in that angiogenesis is mainly characterized by the protrusion and outgrowth of capillary buds and sprouts from pre-existing blood vessels.In...
may occur, causing blood vessels to protrude through the cracks and leak in the space underneath the photoreceptor cell layer. This hemorrhaging can lead to scarring and macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
, causing vision to gradually deteriorate . If left untreated, high myopia can cause retinal detachment
Retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
, glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
, and a higher risk of cataracts.
History
The condition of posterior staphyloma in high myopia was first described by Scarpa in the 1800s . Speculation about reinforcement of the eye began in the 19th century, when Rubin noted that sclera reinforcement “is probably the only one of all the surgical techniques [for myopia] which attempts to correct a cause, rather than an effect” . Procedures in early literature aimed at shortening the length of the eyeball by resecting a ring of sclera from the equator of the eye . Later procedures focused on modifying the axial length of the eye, by preventing elongation and staphyloma progression by placing grafts over the posterior part of the eye. In 1930, Shevelev proposed the idea of transplantation of fascia lataFascia lata
-Thickness:It is an investment for the whole of the thigh, but varies in thickness in different parts.Thus, it is thicker in the upper and lateral part of the thigh, where it receives a fibrous expansion from the Glutæus maximus, and where the Tensor fasciæ latæ is inserted between its layers; it...
for sclera reinforcement . Curtin promoted the use of donor-sclera grafting for reinforcement . In 1976, Momose first introduced Lyodura
Lyodura
Lyodura was a medical product used in neurosurgery that has been shown to transmit Creutzfeldt-Jakob disease, a degenerative neurological disorder that is presently incurable, from affected donor cadavers to surgical recipients. Lyodura was introduced in 1969 as a product of B...
, a material derived from processed cadaver dura mater . At this point, many different surgeons made alterations to existing techniques. Snyder and Thompson modified reinforcement techniques and had positive outcomes , while others, like Curtin and Whitmore, expressed dissatisfaction with their negative conclusions .
Purpose
The surgery aims to cover the thinning posterior pole with a supportive material to withstand intraocular pressureIntraocular pressure
Intraocular pressure is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma...
and prevent further progression of the posterior staphyloma. The strain is reduced, although damage from the pathological process cannot be reversed. By stopping the progression of the disease, vision may be maintained or improved.
Methods of Surgery
There are three basic techniques, referred to as X-shaped, Y-shaped, and single strip support . In X-shaped and Y-shaped, the arms run the risk of the being pulled medially, which would press on the optic nerveOptic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
and could result in optic nerve atrophy. In single strip support, the material covers the posterior pole vertically between the optic nerve and insertion of the inferior oblique muscle. Often, this method is preferred, since it is the easiest method for placement, provides the widest area of support, and reduces the risk of optic nerve interference .
Materials
Many different materials have been used in the past, including fascia lataFascia lata
-Thickness:It is an investment for the whole of the thigh, but varies in thickness in different parts.Thus, it is thicker in the upper and lateral part of the thigh, where it receives a fibrous expansion from the Glutæus maximus, and where the Tensor fasciæ latæ is inserted between its layers; it...
, Lyodura
Lyodura
Lyodura was a medical product used in neurosurgery that has been shown to transmit Creutzfeldt-Jakob disease, a degenerative neurological disorder that is presently incurable, from affected donor cadavers to surgical recipients. Lyodura was introduced in 1969 as a product of B...
(lyophilized human dura) , Gore-Tex
Gore-Tex
Gore-Tex is a waterproof/breathable fabric, and a registered trademark of W. L. Gore and Associates. It was co-invented by Wilbert L. Gore, Rowena Taylor, and Gore's son, Robert W. Gore. Robert Gore was granted on April 27, 1976, for a porous form of polytetrafluoroethylene with a...
, Zenoderm (porcine skin dermis), animal tendons, and donor's or cadaver’s sclera . Human sclera is thought to offer the best support, as well as Lyodura, which is biologically compatible with the eyeball and has sufficient tensile strength. Artificial materials, such as nylon or silicone, are not suggested . Sclera from cadaver’s or animal tendons run the risk of being rejected.
Procedure
While there have been many modifications, Thompson’s procedure has often been used as a basis . First, the conjunctivaConjunctiva
The conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...
and Tenon's capsule are incised about 6 mm from the corneal limbus
Corneal limbus
The corneal limbus is the border of the cornea and the sclera . The limbus is a common site for the occurrence of corneal epithelial neoplasm....
. The lateral
Lateral rectus muscle
The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye and the only muscle innervated by the abducens nerve, cranial nerve VI....
, superior
Superior rectus muscle
The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve...
, and inferior
Inferior rectus muscle
The inferior rectus muscle is a muscle in the orbit.-Actions:It depresses, adducts, and helps extort the eye.The inferior rectus muscle is the only muscle that is capable of depressing the pupil when it is in a fully abducted position....
recti muscles are separated using a strabismus hook. The connecting tissue is then separated from the posterior pole, as well as the inferior oblique muscle. The strip of material is passed under the separated muscles, and pushed down deeply towards the posterior pole. Both ends of the material strip are crossed over the medial rectus muscle and sutured to the sclera on the medial side of the superior and inferior recti muscles. The conjunctiva and Tenon's capsule are then closed together.
Complications
Long-term complication rates are usually low, but short-term complications may include chemosisChemosis
Chemosis is the swelling of the conjunctiva. In general, chemosis is a nonspecific sign of eye irritation. The outer surface covering appears to have fluid in it. Often, the eye area swells so much that the eyes become difficult or impossible to close fully. It is usually caused by allergies or...
, choroidal edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
or hemorrhage, damage to the vortex vein, and transient motility problems .
Controversy
Scleral reinforcement surgery is not presently popular in the United States, and there has been a scarcity of published clinical studies. Donor sclera material is also difficult to acquire and store, and artificial materials are still being tested. This procedure is much more popular in other countries, such as the former Soviet Union and Japan .There is also controversy regarding in what developmental stage this procedure should be performed . Some feel efforts should be made as soon as possible to arrest progression in children. Others feel that the procedure should only be done in cases where high myopia is indicated with macular changes. Furthermore, different surgeons have particular criteria that must be met by patients in order to receive surgery.