Boston Foundation for Sight : Scleral Lens, Dry Eyes, Keratoconus, Corneal Transplant, Lasik, Optometrists, Ophthalmologist, Liquid Corneal Bandage, Severe dry Eye, Ocular Surface Disease

Approved by the FDA in 1994, the Boston Scleral Lens (BSL) is a fluid-ventilated gas-permeable contact lens that rests entirely on the sclera creating a fluid-filled space over the diseased cornea. Unlike air-ventilated scleral lenses, the mechanism for avoiding lens suction utilizes radial channels under its bearing surface (haptic) that facilitate the aspiration of tears into the pre-corneal tear compartment to abort the development of negative hydrostatic pressure-while avoiding the transit of air bubbles. Using the unequalled flexibility and precision offered by spline functions, BSLPD is fabricated from Itafluorfocon B (Dk 127X10-11 units) by a state-of-the-art Optoform-80 lathe, both a gift of Bausch & Lomb.

The Boston Scleral Lens can benefit patients by: 1)masking abnormal corneal astigmatism when traditional RGP corneal contact lenses fail or are contraindicated and 2)managing severe ocular surface disease. As withtraditional hard corneal contact lenses, the Boston Scleral Lens device creates a smooth liquid overlay on the irregular corneal surface that optically neutralizes corneal surface irregularities. This fluid reservoir also functions as a unique liquid bandage that protects the corneal surface from the desiccating effects of exposure to air and the friction of blinking and significantly reduces the intensity of ocular pain and photophobia associated with ocular surface disease and facilitates the healing of persistent epithelial defects.

The Boston Scleral Lens device will not improve vision over that achieved with hard corneal contact lenses. However, because it is supported entirely by the sclera and vaults the cornea and limbus, its centration and positional stability is not constrained by distorted corneal topography. Moreover, by avoiding any contact with the corneal surface, it is useful for eyes with fragile corneal epithelium intolerant of the friction generated by corneal contact lenses. The following is a partial list of indications for which the Boston Scleral Lens should be considered if spectacle correction is inadequate and eyes are intolerant of corneal contact lenses:

§ Corneal ectasia such as keratoconus, pellucid marginal degeneration, keratoglobus.

§ Post keratoplasty astigmatism (generally provides excellent visual acuity and should be considered in lieu of wedge resections, relaxing incisions, laser ablations and repeat corneal transplant surgery).

§ Corneal surface irregularities due to ocular surface disease, anterior corneal dystrophies, scars, etc.

§ Corneal stem cell deficiencies resulting from Stevens-Johnson syndrome and TEN, chemical and thermal injuries, ocular pemphigoid, aniridia, etc.

§ Severe dry eye due to disorders of the lacrimal glands such as Sjogren?s syndrome, graft vs. host disease, irradiation, surgery etc and meibomian gland deficiency.

§ Neurotrophic corneas resulting from herpes simplex/zoster keratitis, congenital corneal anesthesia (dysautonomia), diabetes, acoustic neuroma surgery, trigeminal ganglionectomy, trigeminal rhyzotomy, etc.

§ Persistent non infectious corneal ulcers and epithelial defects associated with stem cell deficient and neurotrophic corneas and severe dry eye..

In general, the Boston Scleral Lens is indicated in corneal disorders for which tarsorrhaphy would be considered.

Although the Boston Scleral Lens (BSL) device is fabricated from Equalens II® (itafluorofocon B, Dk 127X10 ^-11units method of Fatt) and the center thickness averages 0.25mm in minus powers, corneal edema can be provoked in the presence of corneal endothelial dysfunction such as that associated with Fuch?s dystrophy, previous surgery and aging grafts. The presence of corneal edema is a contraindication to wearing this device. In the absence of visible edema, the functionality of the corneal endothelium is tested by evaluating the response to wearing a diagnostic gas-permeable scleral lens a minimum of four hours. If corneal edema is found, the fitting process is aborted unless the potential benefits (such as healing persistent epithelial defects or attenuating chronic, disabling pain and photophobia) outweigh the risks.

Corneal neovascularization, especially pannus, is not necessarily a contraindication if corneal endothelial function is adequate.

The treatment of corneal epithelial defects with extended wear of this device risks bacterial keratitis, especially when combined with the use of topical antibiotics and steroids. However this risk is being reassessed with the availability of preservative-free fourth generation fluoroquinolones that can be added to the fluid reservoir of the device.

The potential for the BSL device to improve vision should be assessed by refracting over a large hard corneal contact lens that is adequately centered for this purpose. If the improvement in vision does not meet the patient?s expectations, this device should not be considered unless other benefits are being considered.

Patients disabled by symptoms of dryness/pain and photophobia associated with SPK, larger corneal erosions, filamentary keratitis, fluorescein staining of the cornea and lissamine green staining of the bulbar conjunctive typically experience a dramatic subjective response to wearing this device. However, the BSL can significantly mitigate severely disabling symptoms in the absence of corneal findings and abnormal Schirmer measurements. This can usually be determined within 1-2 hours of initial insertion of a trial lens during the consultation visit.

Corneal stem cell deficiencies (Stevens-Johnson syndrome/TEN, chemical/thermal injuries, ocular pemphigoid, aniridia, etc.

There are three indications for fitting the Boston Scleral Lens to eyes with stem cell deficient corneas: mitigate pain and photophobia, improve vision by masking irregular astigmatism and the treatment or prevention of recurrences of persistent corneal epithelial erosions and defects. Unlike patients with primary severe dry eye, it may require several days of wearing the device in order to assess the symptomatic response. Symblepharon and foreshortened fornices are not contraindications. However, the fonices must have sufficient capacity to accomodate a lens diameter of at least.15mm.

We do not accept new patients without a written referral and clinical information sufficient to enable us to evaluate the potential of our devices to offer them a significant benefit.

The Fitting Process

Consultation: This involves a comprehensive review of the patients records, history and examination. The process may include digital imaging capture and analysis and corneal topography.

Prognosis assessment: The goal of this procedure is to explore the patient's epectations, reconcile them with ours (if there is a disparity), define realistic goals, determine their feasibility and assess the ocular tolerances to the device. During this period, diagnostic scleral lenses will be inserted, their fitting characteristics will be evaluated and the ocular responses to wearing the device for three to four hours will be assessed and documented. The process may have to be repeated several times over a period of 1-3 days.

The fitting process: Adapting the design of the haptic bearing surface of the device to the eye-specific scleral topography is the cornerstone of the fitting procedure. Precision is required to maintain the patency of the radial venting channels while avoiding the transit of air bubbles. This is an empiric process. The initial fitting characteristics of a lens selected from our library of hundreds of devices is evaluatedin a serial manner until one is found that meets our criteria. This lens is worn for up to 4 hours and its on-eye performance is assessed. The process is repeated until sufficient information is accessed to design the first eye-specific device. The digitized design is linked to our onsite CNC lathe. The clinical fitting characteristics of the lens is studied after several hours of wearing and adjustments in its design are made if needed or its design is modified and a new lens is fabricated when indicated. On average, 3.5 devices are made/eye during the fitting process that can extend up to two weeks or longer. Eyes that have been distorted by cicatricial diseases such as Stevens-Johnson syndrome usually require more extensive design customization and longer fitting periods. Patients are examined three or four times on most days in addition to insertion and removal practice sessions (see below).

Insertion/removal instruction: Air bubble-free insertion and atraumatic removal as well as the care regimen are central to the successful use of this device. Patient instruction and supervised practice is an integral part of the process Mastery of these skills are required and can be challenging for patients with narrow palpebral fissures, recessed globes, pain and photophobia, severly limited vision and poor manual dexterity.

THE BOSTON MiniScleral LENS DEVICE

This companion device, 15.0 to 15.5 mm in diameter, is designed to rest on the more normal (and less sensitive) corneal periphery. Like the Boston Scleral Lens, its design utilizes spline functions to control the vault and peripheral configuration. In this way it can be designed to vault most keratoconic corneas independently of the base curve. Because this device is not supported by the central cornea, it maintains its centration and stability regardless of the corneal topography. Adhesion is prevented by incorporating radial venting channels that maintain an adequate level of tear exchange.

The MiniScleral Lens is useful in managing irregular astigmatism for eyes in which the peripheral corneal surface can be utilized as a bearing platform. This includes keratoconus, post keratoplasty and after unsuccessful radial keratotomies and LASIK procedures. It is not useful for stem cell deficient corneas, other severe ocular surface diseases, very advanced keratoconus, pellucid and Terrien’s marginal degeneration and keratoglobus.

			FOR DOCTORS Approved by the FDA in 1994, the Boston Scleral Lens (BSL) is a fluid-ventilated gas-permeable contact lens that rests entirely on the sclera creating a fluid-filled space over the diseased cornea. Unlike air-ventilated scleral lenses, the mechanism for avoiding lens suction utilizes radial channels under its bearing surface (haptic) that facilitate the aspiration of tears into the pre-corneal tear compartment to abort the development of negative hydrostatic pressure-while avoiding the transit of air bubbles. Using the unequalled flexibility and precision offered by spline functions, BSLPD is fabricated from Itafluorfocon B (Dk 127X10-11 units) by a state-of-the-art Optoform-80 lathe, both a gift of Bausch & Lomb. Indications for the Boston Scleral Lens Prosthetic Device The Boston Scleral Lens can benefit patients by: 1)masking abnormal corneal astigmatism when traditional RGP corneal contact lenses fail or are contraindicated and 2)managing severe ocular surface disease. As withtraditional hard corneal contact lenses, the Boston Scleral Lens device creates a smooth liquid overlay on the irregular corneal surface that optically neutralizes corneal surface irregularities. This fluid reservoir also functions as a unique liquid bandage that protects the corneal surface from the desiccating effects of exposure to air and the friction of blinking and significantly reduces the intensity of ocular pain and photophobia associated with ocular surface disease and facilitates the healing of persistent epithelial defects. Irregular astigmatism and high refractive errors The Boston Scleral Lens device will not improve vision over that achieved with hard corneal contact lenses. However, because it is supported entirely by the sclera and vaults the cornea and limbus, its centration and positional stability is not constrained by distorted corneal topography. Moreover, by avoiding any contact with the corneal surface, it is useful for eyes with fragile corneal epithelium intolerant of the friction generated by corneal contact lenses. The following is a partial list of indications for which the Boston Scleral Lens should be considered if spectacle correction is inadequate and eyes are intolerant of corneal contact lenses: § Corneal ectasia such as keratoconus, pellucid marginal degeneration, keratoglobus. § Post keratoplasty astigmatism (generally provides excellent visual acuity and should be considered in lieu of wedge resections, relaxing incisions, laser ablations and repeat corneal transplant surgery). § Terriens marginal degeneration § Corneal surface irregularities due to ocular surface disease, anterior corneal dystrophies, scars, etc. § Aphakia, high myopia/astigmatism Severe ocular surface disease. § Corneal stem cell deficiencies resulting from Stevens-Johnson syndrome and TEN, chemical and thermal injuries, ocular pemphigoid, aniridia, etc. § Severe dry eye due to disorders of the lacrimal glands such as Sjogren?s syndrome, graft vs. host disease, irradiation, surgery etc and meibomian gland deficiency. § Neurotrophic corneas resulting from herpes simplex/zoster keratitis, congenital corneal anesthesia (dysautonomia), diabetes, acoustic neuroma surgery, trigeminal ganglionectomy, trigeminal rhyzotomy, etc. § Persistent non infectious corneal ulcers and epithelial defects associated with stem cell deficient and neurotrophic corneas and severe dry eye.. In general, the Boston Scleral Lens is indicated in corneal disorders for which tarsorrhaphy would be considered. Contraindications and Complications Although the Boston Scleral Lens (BSL) device is fabricated from Equalens II® (itafluorofocon B, Dk 127X10 ^-11units method of Fatt) and the center thickness averages 0.25mm in minus powers, corneal edema can be provoked in the presence of corneal endothelial dysfunction such as that associated with Fuch?s dystrophy, previous surgery and aging grafts. The presence of corneal edema is a contraindication to wearing this device. In the absence of visible edema, the functionality of the corneal endothelium is tested by evaluating the response to wearing a diagnostic gas-permeable scleral lens a minimum of four hours. If corneal edema is found, the fitting process is aborted unless the potential benefits (such as healing persistent epithelial defects or attenuating chronic, disabling pain and photophobia) outweigh the risks. Corneal neovascularization, especially pannus, is not necessarily a contraindication if corneal endothelial function is adequate. The treatment of corneal epithelial defects with extended wear of this device risks bacterial keratitis, especially when combined with the use of topical antibiotics and steroids. However this risk is being reassessed with the availability of preservative-free fourth generation fluoroquinolones that can be added to the fluid reservoir of the device. Is your patient a candidate? Vision rehabilitation The potential for the BSL device to improve vision should be assessed by refracting over a large hard corneal contact lens that is adequately centered for this purpose. If the improvement in vision does not meet the patient?s expectations, this device should not be considered unless other benefits are being considered. Severe Dry Eye Patients disabled by symptoms of dryness/pain and photophobia associated with SPK, larger corneal erosions, filamentary keratitis, fluorescein staining of the cornea and lissamine green staining of the bulbar conjunctive typically experience a dramatic subjective response to wearing this device. However, the BSL can significantly mitigate severely disabling symptoms in the absence of corneal findings and abnormal Schirmer measurements. This can usually be determined within 1-2 hours of initial insertion of a trial lens during the consultation visit. Corneal stem cell deficiencies (Stevens-Johnson syndrome/TEN, chemical/thermal injuries, ocular pemphigoid, aniridia, etc. There are three indications for fitting the Boston Scleral Lens to eyes with stem cell deficient corneas: mitigate pain and photophobia, improve vision by masking irregular astigmatism and the treatment or prevention of recurrences of persistent corneal epithelial erosions and defects. Unlike patients with primary severe dry eye, it may require several days of wearing the device in order to assess the symptomatic response. Symblepharon and foreshortened fornices are not contraindications. However, the fonices must have sufficient capacity to accomodate a lens diameter of at least.15mm. Referrals are mandatory. We do not accept new patients without a written referral and clinical information sufficient to enable us to evaluate the potential of our devices to offer them a significant benefit. The Fitting Process Consultation: This involves a comprehensive review of the patients records, history and examination. The process may include digital imaging capture and analysis and corneal topography. Prognosis assessment: The goal of this procedure is to explore the patient's epectations, reconcile them with ours (if there is a disparity), define realistic goals, determine their feasibility and assess the ocular tolerances to the device. During this period, diagnostic scleral lenses will be inserted, their fitting characteristics will be evaluated and the ocular responses to wearing the device for three to four hours will be assessed and documented. The process may have to be repeated several times over a period of 1-3 days. The fitting process: Adapting the design of the haptic bearing surface of the device to the eye-specific scleral topography is the cornerstone of the fitting procedure. Precision is required to maintain the patency of the radial venting channels while avoiding the transit of air bubbles. This is an empiric process. The initial fitting characteristics of a lens selected from our library of hundreds of devices is evaluatedin a serial manner until one is found that meets our criteria. This lens is worn for up to 4 hours and its on-eye performance is assessed. The process is repeated until sufficient information is accessed to design the first eye-specific device. The digitized design is linked to our onsite CNC lathe. The clinical fitting characteristics of the lens is studied after several hours of wearing and adjustments in its design are made if needed or its design is modified and a new lens is fabricated when indicated. On average, 3.5 devices are made/eye during the fitting process that can extend up to two weeks or longer. Eyes that have been distorted by cicatricial diseases such as Stevens-Johnson syndrome usually require more extensive design customization and longer fitting periods. Patients are examined three or four times on most days in addition to insertion and removal practice sessions (see below). Insertion/removal instruction: Air bubble-free insertion and atraumatic removal as well as the care regimen are central to the successful use of this device. Patient instruction and supervised practice is an integral part of the process Mastery of these skills are required and can be challenging for patients with narrow palpebral fissures, recessed globes, pain and photophobia, severly limited vision and poor manual dexterity. THE BOSTON MiniScleral LENS DEVICE This companion device, 15.0 to 15.5 mm in diameter, is designed to rest on the more normal (and less sensitive) corneal periphery. Like the Boston Scleral Lens, its design utilizes spline functions to control the vault and peripheral configuration. In this way it can be designed to vault most keratoconic corneas independently of the base curve. Because this device is not supported by the central cornea, it maintains its centration and stability regardless of the corneal topography. Adhesion is prevented by incorporating radial venting channels that maintain an adequate level of tear exchange. Indications The MiniScleral Lens is useful in managing irregular astigmatism for eyes in which the peripheral corneal surface can be utilized as a bearing platform. This includes keratoconus, post keratoplasty and after unsuccessful radial keratotomies and LASIK procedures. It is not useful for stem cell deficient corneas, other severe ocular surface diseases, very advanced keratoconus, pellucid and Terrien’s marginal degeneration and keratoglobus.
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