Boston Type 2 Keratoprosthesis

The Boston Type 2 Keratoprosthesis (KPro) is an artificial corneal implant specifically designed for eyes with severe end‑stage ocular surface disease in which traditional corneal transplantation is doomed to fail. Unlike the more common Type 1 device—which is implanted within a healthy eyelid and tear film—the Type 2 KPro has a 2 mm anterior “nub” that penetrates through a permanent tarsorrhaphy (partial eyelid closure), allowing the optical stem to sit beneath fused lids. Constructed of medical‑grade polymethylmethacrylate (PMMA) and a titanium back plate that locks the donor carrier graft in place, it provides a permanent, transparent optical channel through an opacified cornea, restoring vision in patients with cicatrizing conjunctival diseases, severe dry eye, or obliteration of the fornices EyeWikiFDA Access Data.

In practice, assembly involves sandwiching a central donor corneal graft between the PMMA front plate and the titanium back plate, secured with a locking ring and then sutured into the host cornea. A full tarsorrhaphy is performed to seal the eyelids around the anterior nub, preventing desiccation and exposure. This single‑stage procedure eliminates the need for multi‑stage ocular osteo‑odontokeratoprosthesis (OOKP) approaches, streamlining surgery and follow‑up PMCFDA Access Data.

---

Types of Boston Keratoprosthesis

• Type 1 KPro is the standard design, implanted through an intact eyelid and tear film. It requires a well‑functioning blink mechanism and tear layer to maintain ocular surface health.

• Type 2 KPro is reserved for severe cicatrizing or desiccating conditions—for example, ocular cicatricial pemphigoid or Stevens–Johnson syndrome—where the eyelids, fornices, or tear film are compromised. Its protruding nub and full tarsorrhaphy protect against evaporation and surface breakdown member.myhealthtoolkitks.comEnto Key.

---

Types of Device

While both Type 1 and Type 2 share the same core components (PMMA optic, central stem, donor graft carrier, titanium back plate), the Type 2’s anterior nub and requirement for permanent tarsorrhaphy distinguish it. In Type 2 surgery, after standard KPro assembly, the eyelid margins are fused around the nub to form a sealed pocket, preserving moisture and minimizing inflammation. This adaptation makes Type 2 uniquely suitable for eyes lacking functional lids or tear film.

---

Causes Leading to Boston Type 2 Keratoprosthesis

The Type 2 device is indicated when ocular surface disease is so advanced that conventional grafts fail. Common underlying causes include:

1. Stevens–Johnson Syndrome (SJS): A severe mucocutaneous reaction often triggered by drugs or infection, leading to conjunctival scarring, symblepharon, and keratinization that obliterate the ocular surface and fornices PMC.

2. Ocular Cicatricial Pemphigoid (OCP): A chronic autoimmune blistering disorder causing progressive conjunctival fibrosis, fornix foreshortening, and lid margin keratinization. Over time, vision is lost as the cornea becomes opaque and dry.

3. Severe Chemical Injuries: Alkali or acid burns to the eye can destroy limbal stem cells, conjunctiva, and goblet cells, resulting in symblepharon, keratinization, and chronic inflammation that defy standard transplant FDA Access Data.

4. Thermal/Ocular Burns: High‑temperature exposures (e.g., fire, metal sparks) cause coagulative necrosis of surface tissues and cicatricial changes that preclude graft survival.

5. Trachoma‑Related Scarring: Chronic Chlamydia trachomatis infection can cicatrize the conjunctiva and distort lids, leading to corneal opacity and dry eye in advanced stages.

6. Toxic Epidermal Necrolysis (TEN): A fulminant variant of SJS with widespread epithelial loss, often involving the conjunctiva severely, resulting in end‑stage ocular surface failure.

7. Stevens–Johnson‑Type Reactions in HIV: Immunosuppressed patients may have more severe mucosal involvement, accelerating surface failure and scarring.

8. Gelatinous Drop‑Like Corneal Dystrophy: A rare deposition disease causing progressive opacification, often with poor tear film due to surface irregularity.

9. Aniridia‑Associated Keratopathy: Congenital absence of the iris leads to limbal stem cell deficiency and keratinization of the ocular surface over time.

10. Limbal Stem Cell Deficiency (LSCD): Whether chemical, immunologic, or idiopathic, LSCD prevents corneal epithelial regeneration, resulting in chronic ulceration, vascularization, and opacification.

11. Neurotrophic Keratitis: Loss of corneal sensation (e.g., from herpes zoster) leads to persistent epithelial defects and scarring.

12. Sclerocornea: Congenital or acquired corneal opacification with scleralization often coexists with surface dryness and scarring.

13. Ocular Surface Squamous Neoplasia (OSSN): Extensive surgical or immunologic damage during management can leave the surface untenable for grafting.

14. Severe Autoimmune Dry Eye (e.g., Sjögren’s): Chronic inflammation and tear absence can scar the conjunctiva and cornea.

15. Chronic Graft‑Versus‑Host Disease (GVHD): After bone marrow transplant, immune‑mediated damage to the ocular surface leads to cicatrizing changes.

---

Symptoms of Advanced Ocular Surface Disease

Patients with end‑stage surface disease exhibit:

1. Profound Vision Loss: Often worse than 20/200, due to corneal opacity and surface irregularity.

2. Severe Ocular Pain or Discomfort: From constant epithelial breakdown and inflammation.

3. Photophobia: Light sensitivity caused by exposed nerve endings and corneal irregularities.

4. Constant Tearing (Epiphora): Paradoxical tearing from reflex lacrimation despite overall dryness.

5. Dry‑Eye Sensation: A gritty, burning feeling from lack of tear film.

6. Recurrent Corneal Ulcers: Chronic breakdown leading to microbial invasion and scarring.

7. Eyelid Adhesions (Symblepharon): Conjunctival scarring that tethers the eyelid to the globe.

8. Keratinization of Conjunctiva: Skin‑like transformation that stiffens and opacifies the surface.

9. Eyelid Malposition: Entropion or ectropion from scarring, worsening exposure and irritation.

10. Mucous Plaque Formation: Thick strands of mucin and debris on the cornea.

---

Diagnostic Tests

A comprehensive workup combines clinical examination, manual assessments, laboratory/pathological studies, electrophysiology, and imaging.

Physical Exam

• Best‑Corrected Visual Acuity (BCVA): Standard chart to quantify vision loss.

• Intraocular Pressure (IOP): Tonometry to assess secondary glaucoma risk.

• External Ocular Inspection: Evaluates lid position, symblepharon, and keratinization.

• Blink Mechanism Assessment: Ensures eyelid mobility and completeness of closure.

Manual Tests

• Schirmer’s Test: Measures tear production via filter paper strips.

• Tear Break‑Up Time (TBUT): Fluorescein dye used to time tear‑film stability.

• Fluorescein Staining: Highlights epithelial defects on the cornea.

• Lissamine Green Staining: Reveals devitalized conjunctival cells.

Lab & Pathological

• Impression Cytology: Harvests superficial conjunctival cells to assess goblet cell loss.

• Conjunctival Biopsy: Confirms autoimmune scarring in pemphigoid or SJS.

• Tear Osmolarity: Elevated in dry‑eye syndromes, guiding therapy.

• MMP‑9 Assay: Matrix metalloproteinase marker of surface inflammation.

Electrodiagnostic

• Electroretinography (ERG): Assesses retinal function to rule out inner‑eye pathology.

• Visual Evoked Potential (VEP): Tests optic nerve–cortex conduction, ensuring visual pathway integrity.

• Multifocal ERG: Localizes functional deficits across the retina.

• Electrooculography (EOG): Evaluates retinal pigment epithelium health and ocular motility.

Imaging Tests

• Anterior‑Segment Optical Coherence Tomography (AS‑OCT): High‑resolution cross‑sectional images of the cornea and graft interface.

• Ultrasound Biomicroscopy (UBM): Ultrasound at 50 MHz to image anterior chamber angle and device position.

• Corneal Topography: Maps surface curvature to assess irregularities post‑implant.

• In Vivo Confocal Microscopy: Cellular‑level imaging of corneal epithelium and stroma.

Non‑Pharmacological Treatments

Non‑drug approaches help optimize outcomes after Boston KPro Type 2 implantation by supporting ocular surface health, enhancing comfort, and empowering patients through education.

Exercise Therapies

1. Blink‑Strengthening Exercises
   Gently squeezing the eyelids closed for 5 seconds, then relaxing, repeated 10 times per session. Purpose: improve eyelid closure and tear film distribution. Mechanism: strengthens orbicularis oculi muscles, enhancing the pumping of tears across the prosthesis.

2. Lacrimal Pump Rehabilitation
   Alternating forced eyelid closure and gentle blinking every minute for 5 minutes. Purpose: optimize tear drainage and reduce pooling. Mechanism: retrains the lacrimal pump by conditioning the canaliculi to draw tears efficiently.

3. Moisture Chamber Usage
   Wearing a clear plastic moisture chamber for 30 minutes at a time, three times daily. Purpose: maintain a humid environment around the eye. Mechanism: prevents rapid tear evaporation by creating a microclimate of elevated humidity.

4. Eyelid Stretching
   Using a damp gauze pad to gently stretch the eyelids laterally and medially. Purpose: reduce scarring and cicatricial contracture. Mechanism: mechanical stretching inhibits fibroblast contraction and maintains lid mobility.

5. Facial Massage
   Light circular massage around the brow and periocular region for 5 minutes. Purpose: improve blood flow and lymphatic drainage. Mechanism: mechanical stimulation increases circulation to the eyelids, reducing edema.

6. Scleral Lens Training
   Practicing insertion and removal of a therapeutic scleral lens under supervision. Purpose: enhance safety and patient confidence. Mechanism: repeated practice builds dexterity and reduces microtrauma to the ocular surface.

7. Visual Rehabilitation Exercises
   Tracking a slowly moving target on a screen for 10 minutes daily. Purpose: maximize visual adaptation to the prosthesis. Mechanism: promotes neuroplasticity by stimulating retinal and cortical pathways.

8. Head‑Positioning Drills
   Tilting the head in cardinal directions while fixating on a target. Purpose: optimize alignment of the optical cylinder with the visual axis. Mechanism: trains patients to find the clearest line of sight through the device.

Mind‑Body Interventions

9. Guided Imagery
   Listening to a 15‑minute recorded session visualizing clear vision and comfort. Purpose: reduce anxiety surrounding device care. Mechanism: activates parasympathetic pathways, lowering stress‐related tearing.

10. Progressive Muscle Relaxation
    Systematically tensing and relaxing facial and neck muscles before eye care. Purpose: ease discomfort and improve compliance with cleaning routines. Mechanism: decreases sympathetic tone, reducing reflex blinking and spasms.

11. Mindful Breathing
    Inhaling for 4 seconds and exhaling for 6 seconds during drop instillation. Purpose: enhance precision and reduce flinching. Mechanism: stabilizes hand movements by engaging the diaphragm.

12. Stress Management Workshops
    Participating in a monthly support group with guided relaxation techniques. Purpose: foster peer support and coping strategies. Mechanism: shared learning of relaxation methods decreases perceived burden.

13. Biofeedback Training
    Using an electrode‐based device to monitor blinking rates and tension. Purpose: improve blink pattern control. Mechanism: real‑time feedback enables conscious adjustments to blinking.

14. Cognitive Behavioral Techniques
    Working with a therapist to reframe negative thoughts about vision loss. Purpose: improve adherence to postoperative regimen. Mechanism: restructuring maladaptive beliefs reduces avoidance behaviors.

Educational Self‑Management

15. Device‑Care Workshops
    Hands‑on training sessions on cleaning and lubrication protocols. Purpose: ensure correct hygiene practices. Mechanism: demonstration and repetition solidify motor skills.

16. Self‑Monitoring Diaries
    Daily logs of vision clarity, comfort level, and drop usage. Purpose: track trends and detect early complications. Mechanism: structured record‑keeping spotlights deviations from baseline.

17. Telemedicine Check‑Ins
    Scheduled video calls with the care team every 2 weeks. Purpose: maintain ongoing supervision. Mechanism: remote symptom review enables timely intervention.

18. Educational Videos
    Short animations detailing device anatomy and care steps. Purpose: reinforce written instructions. Mechanism: visual learning augments retention of key steps.

19. Peer Mentorship
    Pairing with an experienced Boston KPro Type 2 recipient. Purpose: practical tips and emotional support. Mechanism: modeling of successful self‑care behaviors.

20. Printed Pocket Guides
    Laminated quick‑reference cards for emergency signs. Purpose: fast access to warning symptoms. Mechanism: prompts early help‑seeking and appropriate measures.

---

Key Pharmacological Agents

These medications prevent infection, control inflammation, and manage pressure.

1. Topical Moxifloxacin 0.5%
   • Class: Fluoroquinolone antibiotic
   • Dosage: One drop every 6 hours indefinitely
   • Purpose: Prophylaxis against bacterial colonization on the device
   • Side Effects: Mild stinging, rare tendinopathy

2. Topical Vancomycin 25 mg/mL
   • Class: Glycopeptide antibiotic
   • Dosage: One drop every 12 hours for high‐risk patients
   • Purpose: Coverage against Gram‑positive organisms, including MRSA
   • Side Effects: Corneal toxicity with prolonged use

3. Topical Prednisolone Acetate 1%
   • Class: Corticosteroid
   • Dosage: One drop twice daily, taper based on inflammation
   • Purpose: Control postoperative inflammation and scarring
   • Side Effects: Increased intraocular pressure, cataract risk

4. Topical Cyclosporine A 0.05%
   • Class: Calcineurin inhibitor
   • Dosage: One drop twice daily
   • Purpose: Reduce chronic ocular surface inflammation
   • Side Effects: Ocular burning sensation

5. Topical Timolol 0.5%
   • Class: Beta‑blocker
   • Dosage: One drop twice daily
   • Purpose: Lower intraocular pressure to protect the optic nerve
   • Side Effects: Bradycardia, bronchospasm

6. Topical Dorzolamide 2%
   • Class: Carbonic anhydrase inhibitor
   • Dosage: One drop thrice daily
   • Purpose: Adjunct pressure reduction
   • Side Effects: Transient burning, dysgeusia

7. Oral Methotrexate 15 mg Weekly
   • Class: Disease‑modifying antirheumatic drug
   • Purpose: Suppress autoimmune surface disease in pemphigoid
   • Side Effects: Liver toxicity, cytopenias

8. Oral Mycophenolate Mofetil 1 g Twice Daily
   • Class: Antimetabolite immunosuppressant
   • Purpose: Maintain surface health by reducing immune attack
   • Side Effects: Gastrointestinal upset, infection risk

9. Oral Azathioprine 2 mg/kg Daily
   • Class: Purine synthesis inhibitor
   • Purpose: Long‑term immunosuppression in cicatricial disease
   • Side Effects: Bone marrow suppression

10. Oral Acetazolamide 250 mg Twice Daily
    • Class: Systemic carbonic anhydrase inhibitor
    • Purpose: Lower intraocular pressure when topical agents insufficient
    • Side Effects: Paresthesias, metabolic acidosis

---

Dietary Molecular Supplements

Nutrients that support healing and ocular surface stability.

1. Omega‑3 Fatty Acids (1 g Daily)
   • Function: Anti‑inflammatory mediator production
   • Mechanism: Converts to resolvins that reduce conjunctival inflammation

2. Vitamin A (10,000 IU Daily)
   • Function: Epithelial cell differentiation
   • Mechanism: Maintains mucin‑producing goblet cells on the ocular surface

3. Vitamin C (500 mg Twice Daily)
   • Function: Collagen synthesis
   • Mechanism: Cofactor for prolyl hydroxylase in stromal repair

4. Vitamin E (400 IU Daily)
   • Function: Antioxidant protection
   • Mechanism: Scavenges free radicals in tear film and tissues

5. Lutein (10 mg Daily)
   • Function: Blue‑light filtering
   • Mechanism: Accumulates in retina to protect photoreceptors

6. Zeaxanthin (2 mg Daily)
   • Function: Complement to lutein in macular defense
   • Mechanism: Quenches reactive oxygen species

7. Zinc (40 mg Daily)
   • Function: Enzyme cofactor
   • Mechanism: Supports matrix metalloproteinases in healing

8. Selenium (200 µg Daily)
   • Function: Glutathione peroxidase component
   • Mechanism: Protects cells from oxidative stress

9. Curcumin (500 mg Twice Daily)
   • Function: Anti‑fibrotic and anti‑inflammatory
   • Mechanism: Inhibits NF‑κB signaling in fibroblasts

10. N‑Acetylcysteine (600 mg Twice Daily)
    • Function: Mucolytic antioxidant
    • Mechanism: Replenishes glutathione and reduces tear viscosity

---

Regenerative & Stem‑Cell‑Based Agents

Emerging biologics that promote surface restoration.

1. Autologous Serum Eye Drops (20% Dilution, QID)
   • Functional: Growth factor delivery
   • Mechanism: Contains EGF and vitamin A to support epithelial healing

2. Platelet‑Rich Plasma Drops (PRP, QID)
   • Functional: High concentration of platelet‑derived growth factors
   • Mechanism: Stimulates stromal and epithelial regeneration

3. Amniotic Membrane Extract Eye Drops (AMED, QID)
   • Functional: Anti‑inflammatory and anti‑scarring
   • Mechanism: Provides heavy chain hyaluronic acid to modulate healing

4. RGTA® (Cacicol, Once Daily)
   • Functional: Glycosaminoglycan mimetic
   • Mechanism: Binds matrix proteins to support extracellular matrix reconstruction

5. Thymosin Beta‑4 (Tβ4, QID)
   • Functional: Wound healing peptide
   • Mechanism: Promotes cell migration and reduces inflammation

6. Recombinant Nerve Growth Factor (Cenegermin, QID)
   • Functional: Neurotrophic support
   • Mechanism: Encourages corneal nerve regeneration and epithelial health

---

Adjunctive Surgeries

Procedures to manage complications and optimize outcomes.

1. Temporary Tarsorrhaphy
   • Procedure: Partial sewing of the eyelids to narrow the palpebral fissure
   • Benefits: Reduces exposure and preserves moisture around the prosthesis

2. Glaucoma Drainage Device Implantation
   • Procedure: Insertion of a tube shunt to lower intraocular pressure
   • Benefits: Protects optic nerve function in eyes prone to post‑KPro glaucoma

3. Pars Plana Vitrectomy
   • Procedure: Removal of vitreous gel via the pars plana
   • Benefits: Clears media opacities and allows vitreal tamponade in endophthalmitis

4. Retroprosthetic Membrane Removal
   • Procedure: Laser or open‐sky excision of opacifying membrane behind the implant
   • Benefits: Restores optical clarity without removing the entire device

5. Amniotic Membrane Grafting
   • Procedure: Suturing a biologic patch over the ocular surface
   • Benefits: Provides a scaffold for epithelial migration and reduces inflammation

---

Prevention Strategies

Proactive measures to avoid complications:

1. Strict hygiene when handling the prosthesis

2. Consistent use of prophylactic topical antibiotics

3. Daily lubrication with preservative‑free drops

4. Regular monitoring of intraocular pressure

5. Use of moisture chambers in low‑humidity environments

6. Avoidance of eye rubbing or manual pressure

7. UV‑protective eyewear outdoors

8. Smoking cessation to improve healing

9. Prompt treatment of lid margin disease

10. Nutritional optimization with antioxidant supplements

---

When to See Your Doctor

Contact your surgeon immediately if you experience sudden vision loss, severe eye pain, redness disproportionate to baseline, discharge, or an inability to instill your drops. Early recognition of infection or device complications can preserve vision.

---

“Do’s” and “Don’ts”

Do:

1. Do carry spare preservative‑free drops when traveling.

2. Do clean the stem daily with sterile swabs.

3. Do wear protective eyewear in dusty or windy conditions.

4. Do keep scheduled follow‑up visits without delay.

5. Do maintain a written log of your symptoms.

Don’t:
6. Don’t swim in pools or lakes without a watertight eye shield.
7. Don’t use over‑the‑counter drops without consulting your surgeon.
8. Don’t skip your antibiotic or steroid regimens.
9. Don’t rub or press on the prosthesis.
10. Don’t ignore signs of elevated eye pressure (headaches, halos).

---

Frequently Asked Questions

1. What is the difference between Boston Type 1 and Type 2?
   Type 1 rests behind open eyelids; Type 2 penetrates through closed lids, offering greater protection for severely scarred surfaces.

2. How long does the implant last?
   With proper care, many patients maintain a functional Type 2 device for 5–10 years or longer.

3. Is anesthesia required for cleaning?
   No, standard cleaning uses preservative‑free drops and sterile swabs—no anesthesia unless complications arise.

4. Can I blink normally?
   Blinking is altered; you learn to close your lids partially around the stem, retaining moisture without completely covering the optical cylinder.

5. Will I need glasses?
   You may require additional refractive correction, often via specialized contact lenses over the device.

6. What are the main risks?
   Infection, glaucoma progression, and retroprosthetic membrane formation are the most common complications.

7. How often are follow‑ups?
   Initially weekly for the first month, then monthly for the first year, and at least every 3–6 months thereafter.

8. Can children receive this implant?
   It is rarely used in pediatric cases due to growth‑related changes but may be considered in select severe cases.

9. Does it feel uncomfortable?
   Most patients acclimate within weeks; regular lubrication minimizes any residual discomfort.

10. Can I drive?
    If vision is sufficient and you meet local licensing requirements, driving may be resumed with your surgeon’s approval.

11. Is pain intense after surgery?
    Moderate discomfort is common initially but usually resolves within days with analgesics.

12. Will I lose eyelash function?
    Eyelashes remain but do not contact the prosthesis; they help protect from debris.

13. Can I undergo MRI scans?
    The device is MRI‑compatible, but always notify the imaging center and your surgeon.

14. What if the device fails?
    Revision surgery or a different prosthesis type may be considered depending on the cause.

15. Is this procedure covered by insurance?
    Many insurers cover Boston KPro Type 2 when criteria are met; verify coverage and prior authorization before surgery.

Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical  history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.

The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members

Last Updated: July 15, 2025.