Scleral lens
Encyclopedia
A scleral lens is a large lens that rests on the Sclera
and creates a Tear
-filled vault over the Cornea
. Scleral lenses are designed to treat a variety of eye conditions, many of which do not respond to other forms of treatment.
. They are unique in their design in that they fit onto and are supported by the sclera, the white portion of the eye. The cause of this unique positioning is usually relevant to a specific patient, whose cornea may be too sensitive to support the lens directly. In comparison to corneal contact lenses, scleral lenses bulge outward considerably more. The space between the cornea and the lens is filled with artificial tears. The liquid, which is contained in a thin elastic reservoir, conforms to the irregularities of the deformed cornea, allowing vision to be restored comfortably. This helps to give the patient BCVA, or Best Corrected Visual Acuity.
, keratoconus
, corneal ectasia, Stevens–Johnson syndrome, Sjögren's syndrome
, aniridia
, neurotrophic keratitis (aneasthetic corneas), complications post-LASIK, complications post-corneal transplant and pellucid degeneration. Injuries to the eye such as surgical complications, distorted corneal implants, as well as chemical and burn injuries also may be treated by the use of scleral lenses.
scleral lenses have also been used to produce eerie eye effects in films, such as the whited-out eyes of the monsters in Evil Dead, or blacked-out eyes in Underworld
and Underworld: Evolution
. These lenses tend to be uncomfortable and sometimes impede the actors' vision, but the visual effects produced can be striking. The lenses cost around $300, are custom-made to fit the wearer's eyes and can also be custom-painted, although most companies only sell lenses with a pre-designed look. There are many different designs available, from standard black lenses to flame-effect eyes, as well as a lens that makes the whole eye white. However, the wearer is unable to see anything while the latter variety of lens is worn. If looked after, the lenses can be kept for approximately one year. It is recommended that they be worn for a maximum of 5–6 hours at a time, and only occasionally.
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...
and creates a Tear
Tears
Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation is the production or shedding of tears....
-filled vault over the Cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
. Scleral lenses are designed to treat a variety of eye conditions, many of which do not respond to other forms of treatment.
Design
Modern scleral lenses are made of a highly oxygen permeable polymerPolymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
. They are unique in their design in that they fit onto and are supported by the sclera, the white portion of the eye. The cause of this unique positioning is usually relevant to a specific patient, whose cornea may be too sensitive to support the lens directly. In comparison to corneal contact lenses, scleral lenses bulge outward considerably more. The space between the cornea and the lens is filled with artificial tears. The liquid, which is contained in a thin elastic reservoir, conforms to the irregularities of the deformed cornea, allowing vision to be restored comfortably. This helps to give the patient BCVA, or Best Corrected Visual Acuity.
Indications for use
Scleral lenses may be used to improve vision and reduce pain and light sensitivity for people suffering from growing number of disorders or injuries to the eye, such as MicrophthalmiaMicrophthalmia
Microphthalmia also referred to as microphthalmos, nanophthalmia or nanophthalmos, is a developmental disorder of the eye that literally means small eye...
, keratoconus
Keratoconus
Keratoconus , is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve....
, corneal ectasia, Stevens–Johnson syndrome, Sjögren's syndrome
Sjögren's syndrome
Sjögren's syndrome , also known as "Mikulicz disease" and "Sicca syndrome", is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva....
, aniridia
Aniridia
Aniridia is the absence of the iris. Aniridia usually involves both eyes. It can be congenital or caused by a penetrant injury. Isolated aniridia is a congenital disorder which is not limited to a defect in iris development, but is a panocular condition with macular and optic nerve hypoplasia,...
, neurotrophic keratitis (aneasthetic corneas), complications post-LASIK, complications post-corneal transplant and pellucid degeneration. Injuries to the eye such as surgical complications, distorted corneal implants, as well as chemical and burn injuries also may be treated by the use of scleral lenses.
Use in special effects
Special effectSpecial effect
The illusions used in the film, television, theatre, or entertainment industries to simulate the imagined events in a story are traditionally called special effects ....
scleral lenses have also been used to produce eerie eye effects in films, such as the whited-out eyes of the monsters in Evil Dead, or blacked-out eyes in Underworld
Underworld (2003 film)
Underworld is a 2003 action-horror film about the secret history of Vampires and Lycans . It is the first installment in the Underworld series. The main plot revolves around Selene , a vampire who is a Death Dealer hunting Lycans...
and Underworld: Evolution
Underworld: Evolution
Underworld: Evolution is the second installment in the Underworld series, following Underworld in 2003...
. These lenses tend to be uncomfortable and sometimes impede the actors' vision, but the visual effects produced can be striking. The lenses cost around $300, are custom-made to fit the wearer's eyes and can also be custom-painted, although most companies only sell lenses with a pre-designed look. There are many different designs available, from standard black lenses to flame-effect eyes, as well as a lens that makes the whole eye white. However, the wearer is unable to see anything while the latter variety of lens is worn. If looked after, the lenses can be kept for approximately one year. It is recommended that they be worn for a maximum of 5–6 hours at a time, and only occasionally.