Therapeutic Contact Lens

Manoj AryalB . Optometry

Institute Of Medicine, Maharajgunj Medical

campus

Presentation layout

IntroductionClassification of TCL typesEssentials of fitting a TCLThe aims of therapeutic contact lens wear

Complications associated with therapeutic contact lenses wear

Aftercare Conclusions

Therapeutic contact lens (TLC)

Introduction Definition:

The term “therapeutic” is derived from the Greek word “therapeuein” meaning to take care of, or to heal.

Mainly fitted with the aim of attempting to maintain or restore the integrity of ocular tissues.

The five main aims of therapeutic contact lenses are:

1. Relief of ocular pain;2. Promotion of corneal healing;3. Mechanical protection and

support;4. Maintenance of corneal

epithelial hydration;5. Drug delivery

Classification: TCL

Silicone rubber and silicone hydrogels (38%);Hard (PMMA) and gas permeable scleral lenses;

Hard scleral rings;Hydrogel soft lenses

Low water content ( 38%-45%); Mid-water content (45%-55%); High water content (67%-80%);

Collagen shields

Silicon Hydrogel

They offer theoretical advantage of oxygen transmissibility and is more suitable for overnight wear

The disadvantage includes the increased rigidity, poor surface wettability, and limited parameters

For painful eyes with irregular corneas, the more soft or flexible the lens the more likely an acceptable and comfortable fit will be achieved

Lens deposition may be a problem especially mucin balls

The increased rigidity may also be expected to increase the risk of CL related papillary reaction, conjunctivitis and SEAL

Applications:

Main application is for wound healing (persistent epithelial defect, corneal ulceration etc.).

They are used for the apposition of wound edges and pain relief.

Corneal ulcerationPersistent epithelial defect

However, the applications may be constrained by the limited range of total diameters and limited choice of BOZR

Some lenses are not available in Plano power, some patients with good visual acuity may not tolerate the change in induced ametropia, such as RCE patients with a VA of 6/5

Silicon rubber

Silicone rubber lenses are difficult to fit.

The total diameter must closely correspond to the corneal diameter

Some movement and tear exchange is essential and uniform edge clearance and central corneal alignment is desirable but rarely achieved.

The lenses often steepen unpredictably and can bind to the cornea.

Thus the fit should be checked immediately following insertion, then again after a few minutes, and after one to two hours and also the following day.

Lens removal can be difficult, especially on a dry eye

Properties and application:

Has a high oxygen transmissibility (Dk 200-400), and absorbs no water so lens parameters are independent of hydration, tear quality or exposure.

The lenses are also robust and flexible but they must be coated to improve surface wetting.

Until recently they were the first choice for the maintenance of corneal hydration, e.g. Sjögrens syndrome, exposure and neurotropic keratitis.

They also offered protection of the ocular surface from eyelashes, keratin, exposure, and glue.

In the presence of a severe dry eye silicone rubber lenses improved the ocular environment to assist wound healing of a corneal perforation and to promote re-epithelialization of a persistent epithelial defect.

The lens was also used to provide pain relief for ocular surface disease

Scleral lenses

With a typical diameter of 23mm,RGP scleral lenses offer protection of both the cornea and the bulbar conjunctiva.

If the lens is fitted to give corneal and limbal clearance the lens will maintain a tear reservoir while protecting the cornea from the shearing forces of the eyelids.

Thus Sjögrens, cicatrizing conjunctivitis and corneal exposure are typical indications.

Therapeutic Use

Irregular or abnormal corneal topography

High astigmatism Keratoconus or other primary corneal ectasia

Corneal transplant Traumatized eye Post-refractive surgery

Contd…High refractive errors

Centration difficulties with high-power corneal lenses.

Intolerance to corneal or hydrogel lens wear in myopia or hypermetropia

Iris encapsulation

Intractable diplopia. Cosmetic shells. Unsightly blind eyes. Aniridia. Microphthalmos.

Therapeutic or protective applications

Corneal hydration in serious dry eye conditions such as Stevens Johnson syndrome and cicatricising conjunctivitis, ocular pemphigoid

Prevention of tear film evaporation with poor lid closure or lid absence

Corneal protection against trichiasis or lid margin keratinisation

Preventing mucus filaments adhering to the cornea Ptosis

Other indications include:

Maintenance of fornices

Ptosis prop

Promotion of epithelial healing in the presence of a severe dry eye, and

Rarely pain relief, neurotropic keratitis and persistent epithelial defects

Therapeutic use of Scleral Lens

Excessive Protrusion in keratoconus & Scleral Lens Wear

Therapeutic use of Scleral Lens

Entropion Ptosis Correction

Limbal diameter RGP lenses Applications and properties:

RGP lens that covers the cornea has the advantage of:

Offering complete corneal protection

Maintaining a corneal tear reservoir and

Can be used with topical medication.

Also lenses with a high oxygen transmissibility are available

Which flex less than silicone rubber, so are less likely to bind.

The lenses can be used in severe dry eye, corneal exposure, trichiasis, and; in these cases they assist with wound healing and may even offer pain relief

Collagen shields

May be used to promote re-epithelialization.

They mould to the shape of the cornea and dissolve over time so they have been advocated for managing epithelial defects.

However, they are uncomfortable, give poor vision, the cornea cannot be examined through the shield, the dissolution rate is variable and unpredictable, and finally they are difficult to remove.

Lens type Primary indications

1)Hydrogels Pain relief

a) Thin mid water content with high bound water

First choice incl.- irregular corneas, mild to moderate dry eyes

b)Steep hydrogel lenses For step corneas

c) Large hydrogel lenses For limbal and scleral defects and buphthalmos

2) Silicon hydrogels For wound healing, apposition of wound edges, short term mechanical protection

3) Rigid gas permeable Corneal protection, maintenance of corneal hydration, promotion of epithelial healing

4) Scleral Mechanical protection of ocular surface, maintain corneal hydration

Essentials of Fitting a TCL Slit lamp

The presence of an anterior segment disorder commonly renders the patient photophobic so the ability to diffuse light and/or reduce the intensity of the slit lamp beam is of particular value in minimizing patient discomfort

Keratometry

Generally not necessary for adequate fitting of soft bandage lenses.

However, it may have a value in monitoring the progression of some conditions, for example, keratoconus and progressive corneal dystrophies

In the presence of gross corneal distortion and the absence of any corneal graft, measuring K-readings of the fellow non-diseased eye can provide a useful guide.

Lens selection

A thicker lens may be more desirable when the function is to act as a splint (as in descemetocele) or to cover an irregular corneal surface

Thicker lenses may also be desirable in some cases of tear film instability to support a more stable tear structure.

A thinner lens is more appropriate in cases of epithelial disruption (for example, recurrent erosion)

Lens Fitting

Ideally, a well fitting bandage lens should provide full corneal coverage, be centered, with adequate movement (>0.25mm with each blink) to allow clearance of debris.

It is important for the lens fit to be stable, avoiding excessive movement, as this can cause discomfort or further epithelial disruption.

Stability can be enhanced by increasing the lens total diameter

Parameter range

The majority of ‘bandage lenses’ used are Plano or near Plano prescription.

In most circumstances, soft lenses of standard total diameters 14.0mm to 14.5mm will suffice.

Larger diameter lenses (15mm to 20mm) may be required where the specific function is to protect the limbus or prevent wound leakage at suture or incision sites

Larger diameter lenses require flatter back optic zone radii to achieve the desired fit.

Lens stability

Both a stable fit and minimal dehydration are desirable.

In cases of irregular corneas, such as advanced cases of keratoconus or post surgery, a stable fit may not be achievable with a single lens material.

Piggyback or hybrid lenses can offer success in cases when acceptable centration cannot be achieved with a an RGP alone.

Piggy-back systemsHelpful when RGP lens is intolerable due to staining and patient reluctant to surgery where a rigid corneal lens is worn over a soft lens

Soft lens Extra limbal negative or Plano soft lens (mod. To high Dk)

RGP lens (TD – 9.0 & 10.0 mm)Disadvantages

RGP rides low with little or no movement Localized hypoxia & neovascularization Difficult to handle/maintain two types of lenses

Avoid the use of topical anesthetics as this may mask the pain associated with a poor fitting lens.

The lens fit should be assessed after approximately 20 minutes and ideally again after approximately 60 minutes (owing to lens dehydration effects).

Peripheral lens fit is also very important as e.g. flared lens edges may gives rise to discomfort etc.

A well fitting TCL should have good corneal coverage with appropriate mobility

Suggestions for improving corneal coverage, centration and stability

First Last

Poor corneal coverage

Increase total diameter

Steepen BOZR

Excess lens movement

Reduce thickness

Steepen radius

Increasediameter

Lens too tight

Reduce thickness

Flatten radius

Decreasediameter

Irregular ocularsurface

Low modulus ofelasticity

Thin lens

Dry eye/exposure

High bound water

Reduce watercontent

Non-ionic Increasethickness

RestrictedFornices

Reduced diameter, typically 13.00mm

Aims of therapeutic contact lens wear

The cause of ocular pain includes:

Exposed or compressed nerve endings in recurrent corneal erosion, Thygeson's disease, and bullous keratopathy

Tension from the eyelid on mucous-epithelial tags in filamentary keratitis and superior limbic keratitis.

Mechanism: lens protects the cornea from the shearing force of the eyelid during blink.

Aim 1: Relief of pain

A . Bullous Keratopathy

This condition of chronic edema of the cornea can be extremely painful.

Main aim of the therapeutic lens: alleviate the symptoms of pain, epiphora, photophobia and blepharospasm and also attempt to reduce the chronic edema

Endothelial cell malfunction is frequently a common factor

Malfunction of endothelium may occur as the result of a dystrophic process such as Fuch’s dystrophy

Fuch’s dystrophy usually begins with guttation of the corneal endothelium

It is bilateral but usually asymmetrical

The guttation are initially seen in the central cornea and spread peripherally.

Slight stromal edema occurs and is eventually followed by epithelial edema and bullous keratopathy

Scenarios where TCL use could be considered in Bullous keratopathy

1. In a patient with a painful eye with no visual potential:

& 2. In a patient who is not fit for graft surgery.

Action

This is best fitted with a TCL as soon as possible.

Lens movement should be minimized and

Is best achieved by the employment of a large, hydrogel lens with high water content to maintain the maximum oxygen permeability for continuous wear.

3.As a temporary measure where a patient is going to have a penetrating keratoplasty at some future date.

Action:

A thin high water content TCL is indicated due to the reduced risk of producing corneal vascularization.

B . Filamentary keratitis

Action:

In severe cases a high water content TCL could be considered where the main function is to act as a pressure bandage thus relieving pain and foreign body sensation.Severe filamentary keratitis in a mucus

sheet in a patient with severe dry eye due to Sjögren's syndrome

C. THYGESON’S SUPERFICIAL PUNCTATE KERATITIS

It consists of recurrent episodes of fine superficial greywhite punctate corneal opacities of presumed viral etiology.

The corneal opacities distort the epithelial surface and may even reduce visual acuity.

Action:

In severe cases a high water content TCL could be considered where the main function is to act as a pressure bandage thus relieving pain and foreign body sensation.

D. Superior limbic keratoconjunctivitisAction:

TCLs are very effective in alleviating both signs and symptoms of the disease.

Consider a relatively large TD soft TCL

Aim 2: Promotion of epithelial healing

A. RECURRENT CORNEAL EROSION: Anterior membrane dystrophies

Action:

TCL used on an extended wear basis for 2, 3 or even 6 months.

Ultra-thin TCLs are contraindicated due to possible buckling or wrinkling of the lens with lid movement, thus producing an ineffective corneal splint action.

A thick, high water content extended wear lens is preferred.

“Disposable” lenses are recommended.

B. Traumatic corneal abrasions:

Abrasions over 4mm may benefit from the use of TCLs

Action:

The use of disposable lenses is indicated, particularly in the treatment of corneal erosions with good success

C . Persistent corneal epithelial defect

Cornea is more vulnerable to infection and therefore PED is associated with a

High rate of ulceration and perforation

Action:

TCLs (e.g. “disposables”) can provide mechanical protection from the lids.

Collagen shields hydrated in acidic fibroblast growth factor have been shown to promote epithelial wound healing in such cases.

D. Chemical injuries

Chemical injuries may suffer severe stromal ulceration due to the collagenolytic activity unleashed.

The presence of a TCL may inhibit the passage of certain proteolytic enzymes present in the tear fluid to the stroma, thus preventing the progressive ulcerative process following chemical injuries

Action: A chemical burn to the eye is often associated with chemosis as well as the epithelial damage.

Therefore: -

A small total diameter TCL is the lens of first choice (TD~12.5mm).

If the lids are involved, a scleral lens may be better

E . Postoperative epithelial disorders:

Many ophthalmic surgical procedures can result in temporary corneal epithelial defects.

These include: Vitrectomy Post penetrating keratoplasty in the early

post operative period Epikeratoplasty Kerato-refractive procedures e.g. PRK, LASIK Cataract extraction

Action:

Soft and collagen TCLs may be utilized in order to minimize post surgical epithelial trauma, provide a stable healing environment and promote rapid healing

F. Penetrating keratoplasty

A silicon rubber TCL may be used to reform the anterior chamber

Aim 3 :Mechanical protection and support A. CORNEAL LACERATION

Action:

With small perforations (less than 2mm) without tissue loss, structural support may be achieved and the integrity of the eye maintained, by the utilization of a TCL

Perforations close to the limbus and those in vascularized areas respond most favorably to the application of TCLs.

Partial thickness corneal lacerations involving stroma, with the wound edges well a positioned can be treated with a TCL.

A small perforation near the visual axis may heal with less resultant astigmatism if a TCL rather than a suture is used.

A thin low water content soft lens would be the lens of first choice

B. TRABECULECTOMY

Large (total diameter 20.5mm), high water content TCLs can be fitted to press over the leaking bleb

C. CORNEAL THINNING

Fit a hydrophilic TCL to act as a corneal splint, which can retard or even stop the rate of thinning and hence prevent perforation.

As this often occurs in dry eyes, silicone rubber lenses may be better

D. PROTECTION OF CORNEA

TCLs and particularly scleral lenses are very useful in providing protection and comfort in Trigeminal (5th) nerve palsy, Facial (7th) nerve palsy.

Consider a pre-formed scleral lens.

Other situations include: - Lid deformities with eye exposure Entropion, Trichiasis Scarred lids.

Aim 4: Maintenance of corneal hydration

A. CICATRIZING CONJUNCTIVAL DISEASEStevens-Johnson SyndromeOcular pemphigoidChemical burnTrachomaPseudo-membranous and membranous conjunctivitis

Atopic keratoconjunctivitisDry eyes

I) Steven’s Johnson syndrome:

B/L conjunctivitis is a featureWhich usually lead to scarring of the conjunctivas

Severe irreversible changes such as scarring, keratoconjunctivitis sicca, symblepharon, entropion and trichiasis may occurs

Treatment with scleral lens or ring is usually helpful

A scleral lens does also retain a tear layer in front of the cornea and this helps in reducing corneal keratinization and provides better vision by negating the optical effects of corneal irregularities

It is desirable to use a very large(15-20mm), low or medium water content lens to prevent adhesion forming or re-forming

Thin lens : tend to distort and wrinkle

Better to use thicker more rigid lens and

Low water content lenses: tend to become coated too quickly to deposits

Use of medium water content lenses(55%) relatively thick lens seem optimal

Large sophisticated multi-curved flexible silicon lenses: lens of choice

II) THE DRY EYE:

In marginal to severely dry eyes hydrophilic TCLs are not recommended.

Silicone rubber lenses may be considered

III) Ocular pemphigoid

Therapeutic contact lens indicated:

To protect the cornea against the action of ingrowing lashes and malposition of lids

Thin lenses are to be avoided and thicker lenses are preferred

Lens must be large enough

IV) Trachoma

In earliest stage

Presence of soft immature follicles in the upper tarsal conjunctiva

A punctate keratitisEarly superior corneal pannus

In late stage

Cicatrization of lidsSymblepharonTrichiasisAnd distortion of lids

Therapeutic contact lenses can be used to separate inflamed tissue to prevent symblepharon and to avoid the effects of ingrowing lashes

Aim 5: Drug delivery Hydrogel TCLs alter the pharmacokinetics and effectiveness of topically applied drugs.

Hydrogel lenses soaked in medication and then placed on the eye generally give very high ocular levels of medication that diminish with time which are superior to frequent topical application of drops alone.

Medication impregnated lenses are appropriate for short-term use when corneal protection and therapeutic levels of specific medications are desired.

Other conditions requiring therapeutic contact lenses

Reducing the effect of aqueous leaks Improvement of visionProtection of cornea during tonometryMaintenance of conjunctival formices Ortoptic uses Control of refractive errors

Reducing the effect of aqueous leaks

Perforation in the anterior segment which lead to loss of aqueous fluid can often be controlled by a tightly fitting soft contact lens which partially seals the perforation, whether it be created by trauma or surgery.

Improvement of vision

RGP and scleral lenses can provide a regular anterior refracting surface and improve the visual acuity considerably.

In cases of extreme corneal sensitivity or irregularity, where contact of the cornea with a hard surface is inadvisable, a rigid lens can be fitted on top of a soft lens to provide the required, regular refractive surface.

Maintenance of conjunctival formices

May occur in several scarring disease of mucosa, for e.g. erythema multiforme, ocular pemphigoid and chemical burns.

Although a scleral lens is commonly used to separate the tissue surfaces, a very large and reasonably soft contact lens can be used for same purpose.

Ptosis props

If the eyelid occludes the visual axis, a ptosis prop may be required.

A modified scleral lens may be successful depending on the force closing the eyelid.

Indications include:Ocular myopathy, Myasthenia gravis, eyelid trauma and Neurological problems (e.g. Third nerve palsy).

Neuroparalytic and neurotropic conditions

Signs: Loss of corneal sensitivity Epithelium becomes dry and areas of

necrosis eventually occur

Daily wear of large medium water content soft lens is better

If extended wear is preferred, then 2 or more lenses should be alternated daily in order to keep the lenses clean

Orthoptic uses

A contact lens may be used as a cosmetic occlude in cases of intractable binocular diplopia

Any type of contact lens may be used

Usually, complete occlusion can only be achieved by having an opaque iris pattern and opaque pupil

In squint treatment, contact lens occlude have been used before the better eye to assist in eliminating diplopia

Partial occlusion with contact lenses has also been used in the treatment of suppression

The fitting of anisometropic amblyopes with contact lenses has brought about some dramatic improvements in the visual acuity and assisted in the orthotic treatment of squints in such cases

Orthokeratology Non surgical clinical technique that uses specially designed and fitted Rigid CLs(flat fit)

To reshape the corneal contour For temporal modification and elimination or reduce refractive errors

Orthokeratology

Principles: Corneal Shape Change Compression/redistribution of fluids/cells from the center to periphery

Thinner central corneal epithelium

– Positive pressure from a flat central lens curve

Thicker mid-peripheral corneal epithelium

– Negative pressure from tear pool under steep 2nd (reverse) curve

Control of refractive errors

Advantages

To be free of both CLs and spectacle all day

Ideal for sportsman, swimmers or those who work in dusty or dirty environment

Ideal for contact lens intolerant patients

Disadvantages

Patient needs meticulous follow ups

Retainer lens wear is essential throughout the life

The degree of success is high but cannot always be guaranteed

Patient Selection

Good Candidates

Moderate to low level myopes (-1.00D to -5.00D)

<1.50D astigmatism

Corneal diameters greater than 11.00mm

Soft lens / spectacle wearers

Poor Candidates

High level myopia/astigmatism

Against the rule astigmatism > 0.75D

Current GP / past PMMA lens wearers

As an aid to defective color vision

A red contact lens, of peak transmission 595nm worn in one eye only has been recommended by La Bissorniere (1974).

Known as the X-Chrome lens, during binocular viewing it gives rise to a different perception of hues, altering their saturation or brightness, and the wearer learns to relate that appearance to a particular color name.

Therapeutic contact lens selection: examplesCHOICE FIRST LAST

Pain relief

Hydrogel

Silicon hydrogel

Scleral Limbal RGP

Epithelial healing

Silicon hydrogel

Hydrogel

Scleral Limbal RGP

Perforation

Silicon hydrogel

Hydrogel

Scleral Limbal RGP

Sensitive type

Hydrogel

Silicon hydrogel

Scleral Limbal RGP

Ease of fit

Hydrogel

Silicon hydrogel

Limbal RGP

scleral

SEVERITY

MILD SEVERE

Exposure

Hydrogel

Silicon hydrogel

Limbal RGP

Scleral

Dry eyes

Hydrogel

Silicon hydrogel

Limbal RGP

Scleral

Corneal protection

Hydrogel

Silicon hydrogel

Limbal RGP

Scleral

Irregular ocular surfaces

Hydrogel

Silicon hydrogel

Limbal RGP

Scleral

Indications for therapeutic lens wear

Complications Factors associated with complications in therapeutic lens wear

Patient related Severity of ocular

pathology Concurrent dry eye Concurrent topical

corticosteroids Poor compliance

– ocular hygiene

– general hygiene Poor generalhealth

Lack of motivation Absence of corer

Lens related

Hypoxia

– low water content

– thick lensDepositionMechanicalinsult

– poor fit

Management of complications The patient should be informed of the benefits and risks of therapeutic lens wear

In view of potential increased risk of microbial keratitis, prescribe antibiotics for prophylactic purposes, especially in the presence of an epithelial defect

Patients often benefit from the use of non-preserved wetting drops to insert upon waking.

The use of medication in ointment form is not usually appropriate because of the effect on lens wettability and vision

Lens-related effects can be minimized by the practitioner choosing the best lens type for an individual patient.

Maximizing oxygen transmissibility will limit hypoxic effects

Frequent lens replacement is an effective way of management of deposits

Lid hygiene procedures should be explained and demonstrated, and

For those patients wearing therapeutic lenses on a daily wear basis the importance of hand washing, prior to touching the eye or lenses should be reviewed at each aftercare visit

Topical medication and contact lens

Hydrogel Silicon hydrogel

Silicon rubber

Rigid: corneal

Rigid: scleral

Fluorescein

Ointments

?

V.A. V.A. V.A. V.A.

Preserved Rx

Short term

Short term

Un- preserves Rx

Aftercare

Practitioners should be aware the lens fit may change as the therapy progresses.

Visual acuity should be measured and recorded at each visit

Patient is well instructed on both the need for good hygiene and what action to take if a problem arises

It is usual for a bandage lens to be worn overnight, hence the lens fit and ocular status should be reviewed again after the first night of wear.

In contrast, in cases such as bullous keratopathy where the lens provides pain relief, regular lens removal and replacement is desired.

In such cases the use of disposable lenses is beneficial.

The silicone hydrogel lens has proved very successful in the management of this group of patients

Conclusions

Contact lens fitting for therapeutic purposes is not a part of mainstream practice, practitioners should be familiar with its practice and the techniques involved to enable them to provide advice and appropriate levels of aftercare.

The objective is rarely to achieve an optimal visual result, rather to protect or assist in the healing process of the compromised cornea

The same high level of care must be taken in all aspects of the contact lens fitting and aftercare process.

Close collaboration with the medical management of the condition is required.

Therapeutic contact lens practice can be challenging, but often rewarding as it can lead to dramatic improvements for the patient in reducing discomfort and aiding the healing process

References Anthony J Phillips and Janet Stone CONTACT LENSEs

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