Scleral reinforcement is a surgical procedure used to reduce or stop further macular damage caused by high

myopia Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. ...

, which can be degenerative.

High myopia

Myopia Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. ...

is one of the leading causes of blindness in the world.Grossniklaus, H.E. and W.R. Green, Pathologic findings in pathologic myopia. Retina, 1992. 12(2): p. 127-33.Bores, L.D., Scleral Reinforcement, in Refractive Eye Surgery. 2001, Blackwell Science, Inc.: USA. p. 466-491. It is caused by both genetic Curtin, B.J., The nature of pathological myopia, in The Myopias. 1985, Harper & Row: Philadelphia. p. 237-239. and environmental factors,Saw, S., et al., Myopia: gene-environment interaction. Annals of the Academy of Medicine, Singapore, 2000. 29(3): p. 290. such as mechanical stretching, excessive eye work and accommodation, as well as an elevated

intraocular pressure Intraocular pressure (IOP) 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 of glaucoma. Most tonometers are calibrated t ...

. 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 The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. In the development of t ...

elongation and thinning (at least 25.5 mm to 26.5 mm) and high

refractive errors Refractive error is a problem with focus (optics), focusing light accurately on the retina due to the shape of the eye and/or cornea. The most common types of refractive error are myopia, near-sightedness, hyperopia, far-sightedness, astigmatis ...

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 In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

and retinal vessels, but the posterior pole type is the most common.Curtin, B.J., The posterior staphyloma of pathologic myopia. Trans Am Ophthalmol Soc, 1977. 75: p. 67-86. As the posterior staphyloma enlarges, choroidal tissue becomes thin and

Bruch's membrane Bruch's membrane or lamina vitrea is the innermost layer of the choroid of the eye. It is also called the ''vitreous lamina'' or ''Membrane vitriae'', because of its glassy microscopic appearance. It is 2–4 μm thick. Anatomy Structure B ...

begins to break, creating lesions called lacquer cracks.

Neovascularization Neovascularization is the natural formation of new blood vessels ('' neo-'' + ''vascular'' + '' -ization''), usually in the form of functional microvascular networks, capable of perfusion by red blood cells, that form to serve as collateral circu ...

may occur, causing blood vessels to protrude through the cracks and leak in the space underneath the

photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation ...

layer. This hemorrhaging can lead to scarring and

macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred vision, blurred or vision loss, no vision in the center of the visual field. Early on there are often no sym ...

, causing vision to gradually deteriorate. If left untreated, high myopia can cause

retinal detachment Retinal detachment is a condition where the retina pulls away from the tissue underneath it. It may start in a small area, but without quick treatment, it can spread across the entire retina, leading to serious vision loss and possibly blindness. ...

glaucoma Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...

, and a higher risk of

cataracts A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or double vision, halos around ligh ...

History

The condition of posterior staphyloma in high myopia was first described by Scarpa in the 1800s.Scarpa, A. A. (1818). A Treatise on the Principal Diseases of the Eye. London. 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 or myopiawhich attempts to correct a cause, rather than an effect”.Rubin, M.L., Surgical procedures available for influencing refractive error., in Refractive Anomalies of the Eye. 1966, US Government Printing Office: Washington. 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 lata The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by the medial intermuscular septum and the lateral intermuscular sept ...

for sclera reinforcement.Shevelev, M.M., Operation against high myopia and scleralectasia with aid of the transplantation of fascia lata on thinned sclera. Russian Oftalmol J, 1930. 11(1): p. 107-110. Curtin promoted the use of donor-sclera grafting for reinforcement.Curtin, B.J., Surgical support of the posterior sclera: Part II. Clinical results. Am J Ophthalmol, 1961. 52: p. 253. In 1976, Momose first introduced Lyodura, a material derived from processed cadaver dura mater.Momose, A., Surgical treatment of myopia.... with special references to posterior scleral support operation and radial keratotomy. Vol. 31. 1983. 759-767. At this point, many different surgeons made alterations to existing techniques. Snyder and Thompson modified reinforcement techniques and had positive outcomes,Snyder, A. and F. Thompson, A simplified technique for surgical treatment of degenerative myopia. American Journal of Ophthalmology, 1972. 74(2): p. 273. while others, like Curtin and Whitmore, expressed dissatisfaction with their negative conclusions.Curtin, B. and W. Whitmore, Long-term results of scleral reinforcement surgery. American Journal of Ophthalmology, 1987. 103(4): p. 544.

Purpose

The surgery aims to cover the thinning posterior pole with a supportive material to withstand

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

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

, Lyodura (lyophilized human dura),

Gore-Tex Gore-Tex is W. L. Gore & Associates's trade name for waterproof, breathable fabric membrane. It was invented in 1969. Gore-Tex blocks liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabri ...

, Zenoderm (porcine skin dermis),Gerinec, A., & Slezakova, G. (2001). Posterior scleroplasty in children with severe myopia. Bratisl Lek Listy, 102(2), 73-78. animal tendons, and donor's or cadaver’s sclera.Balashova, N., Ghaffariyeh, A., & Honarpisheh, N. (2010). Scleroplasty in progressive myopia. Eye.Ward, B., Tarutta, E., & Mayer, M. (2009). The efficacy and safety of posterior pole buckles in the control of progressive high myopia. Eye, 23(12), 2169-2174. 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.{{clarify, reason=Conflicts with Gore-Tex, date=February 2022 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.Thompson, F., Scleral Reinforcement. Chapter 10., in Myopia Surgery. 1990, Macmillan: New York. p. 267-297. First, the

conjunctiva In the anatomy of the eye, the conjunctiva (: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with gobl ...

and

Tenon's capsule Tenon's capsule (), also known as the Tenon capsule, fascial sheath of the eyeball () or the fascia bulbi, is a thin membrane which envelops the eyeball from the optic nerve to the corneal limbus, separating it from the orbital fat and forming a ...

are incised about 6 mm from the

corneal limbus The corneal limbus (''Latin'': corneal border) is a highly vascularized and pigmented zone between the cornea, conjunctiva, and the sclera (the white of the eye) that protects and heals the cornea. The cornea is composed of three primary cell ty ...

. The

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places * Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lak ...

, 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.

Complications

Long-term complication rates are usually low, but short-term complications may include

chemosis Chemosis is the swelling (or edema) of the conjunctiva. The term derives from the Greek words ''cheme'' and ''-osis'', ''cheme'' meaning cockleshell due to the swollen conjunctiva resembling it, and ''-osis'' meaning condition. The swelling is ...

, choroidal

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, ...

, 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.

References

Visual disturbances and blindness Disorders of choroid and retina Disorders of ocular muscles, binocular movement, accommodation and refraction