Keratoprothesis Surgery and Patient Care
Surgery Information for Physicians
- Standard preoperative medical assessment
- General anesthesia or monitored intravenous analgesia
- Antibiotics IV recommended at the time of surgery, e.g., cefazolin 1.0 g., if no allergy.
- The surgery time is usually about an hour and a half.
- Boston Keratoprosthesis surgery is readily performed by ophthalmologists with experience in corneal surgery.
The patient should be seen the following day, after e.g. one week, one month, every two months for the first year, then every three months. If problems, modify schedule.
NOTE: Keratoprosthesis requires a more detailed postoperative follow up regimen than standard keratoplasty. Successful outcome requires patient compliance, more frequent follow up visits and more demands on physician time.
- Prednisolone acetate 1% drops, initially 4 times daily, tapered over 6 months according to degree of inflammation.
- Peribulbar injection of triamcinolone, e.g. 20-40 mg may be used if needed for inflammation after KPro implantation. (Recommended after YAG laser membranotomy.)
- Cephazolin 1.0 g or a fluoroquinolone IV (if no allergy) during surgery.
- Moxifloxacin or gatifloxacin four times daily postoperatively, tapering to once daily after two weeks, to be continued for life
- Vancomycin drops (14 mg/ml+0.005% BAK) once daily, postoperatively for life. Must be made up by hospital or compounding pharmacy. Stable for 2 months at room temperature.
- Alternatives for long-term topical prophylaxis (after two weeks postoperative), instead of a fluoroquinolone and vancomycin, are polymyxin B/trimethoprim (Polytrim) solution, used once daily, used for life.
- Amphotericin B drops 0.15% twice daily for a week every 3 months as a prophylactic antifungal “burst” may be desirable in regions of high risk for fungal infections.
- Topical glaucoma medications are effective after KPro implantation, but prostaglandin analogues should be avoided in the early postoperative period
- Oral carbonic anhydrase inhibitors are equally effective in KPro eyes as in other postoperative indications.
Note: It is difficult to assess IOP in KPro eyes, and finger palpation is the only available method. The optic nerve head (cup to disk ratio) should be observed and recorded at every visit (3 month intervals) and formal visual field testing be performed every 6 month.
Close collaboration with a glaucoma specialist is advised.
Soft Contact Lenses:
- Patients with a keratoprosthesis should wear an appropriate extended wear soft contact lens, which should be cleaned or replaced per the contact lens manufacturer’s instructions.
- If lens deposits occur (in poorly blinking eyes), a hybrid contact lens (soft periphery, rigid center) can provide a clear visual axis.
Close collaboration with your Contact Lens Service is advised.
Potential Complications and Adverse Events
- Persistent epithelial defect: Patients at greatest risk of persistent epithelial defect after Boston KPro are those with preoperative corneal limbal stem cell deficiency. The risk of persistent epithelial defect is reduced by continuous contact lens wear and avoidance of topical antibiotics more than twice a day.
- Sterile keratolysis: Sterile keratolysis is recognized by slit lamp biomicroscopy, but may be found earlier by high resolution optical coherence tomography, which is recommended every 6 months after surgery. Sterile keratolysis has been associated with the presence of retroprosthetic membrane and chronic uveitis. Surgical and postoperative approaches that ensure good corneal would apposition and reduce postoperative inflammation, respectively, will reduce retroprosthetic membrane formation and subsequent keratolysis. Contact lens wear is essential to reduce the risk of keratolysis after KPro. Consider a microbial cause in every case but if culture negative, sterile keratolysis may be treated with patch graft or replacement of the KPro.
- Microbial keratitis: Infection of the donor corneal graft surrounding the keratoprosthesis most commonly occurs around and beneath the KPro front plate. Diagnosis and treatment are standard, but serial examination is essential to recognize the small subset of patients who subsequently develop intraocular infection. The risk of microbial keratitis after KPro is reduced by continuous contact lens wear (to reduce epithelial defect), and daily use of two antibiotics with different mechanisms of action, and combined broad antimicrobial spectrum.
- Retroprosthetic membrane: Patients with poor corneal wound closure and those with intraocular inflammation after KPro are at greatest risk for membrane formation. Attention to both surgical technique and control of postoperative inflammation are important to prevent and limit retroprosthetic membrane formation. When present and visually significant, a retroprosthetic membrane can be opened with YAG laser as long as no blood vessels have entered the membrane. Energy settings below 2.0 mJ are recommended to avoid damage to the KPro.
After Yag laser treatment, peribulbar injection of 20-40 mg triamcinolone is recommended. Vascularized retroprosthetic membrane requires pars plana surgical approach or KPro replacement with intraoperative excision of the membrane.
- Glaucoma: Preexisting glaucoma is very common in patients needing KPro, worsens in a majority of patients postoperatively, and also occurs de novo in many patients postoperatively even when glaucoma was not evident preoperatively. Frequent optic nerve exams (every 3 months) and formal visual field testing (every 6 months) is recommended, along with aggressive treatment of increased intraocular pressure and/or optic nerve cupping and visual field evidence for glaucoma. Topical and systemic anti- glaucoma medications are usually effective at reducing intraocular pressure, but a glaucoma drainage device may often be necessary (e.g., Ahmed valve). Collaboration with a glaucoma expert is strongly recommended.
- Sterile vitritis: Vitreous inflammation in the absence of any other signs of infection can occur at any time after KPro implantation, but microbial endophthalmitis should always be considered. In an eye with vitreous cells and no other signs of microbial endophthalmitis, vitritis may be treated by increased frequency of topical corticosteroids and/or peribulbar injection of 20-40 mg of triamcinolone.
- Microbial endophthalmitis: Intraocular infection after KPro is usually consecutive to microbial keratitis. Significant vitreous inflammation in the setting of microbial keratitis should always be considered microbial and treated in standard fashion by a vitreoretinal surgeon with vitreous biopsy and intraocular antibiotics +/- an antifungal agent, depending on clinical suspicion. However, microbial endophthalmitis after KPro may also occur without signs of corneal infection, and when suspected, should be referred immediately to a vitreoretinal specialist for vitreous tap and intraocular antibiotics.
- Retinal detachment: Reported rates of retinal detachment after Boston keratoprosthesis vary widely, with the highest incidences in patients with autoimmune disorders and after chemical injuries. When a vitrectomy is indicated at the time of keratoprosthesis implantation, collaboration with an experienced vitreoretinal surgeon is recommended. Peripheral retinal examination after Boston keratoprosthesis is difficult, but wide-field retinal imaging cameras can visualize retinal periphery well beyond what can be seen with indirect ophthalmoscopy, and should be utilized at least annually after keratoprosthesis implantation. Although retinal detachment repair can in many cases be successful anatomically, with the vitreoretinal surgeon working directly through the Boston keratoprosthesis, the functional results after retinal detachment in patients with a Boston keratoprosthesis are typically poor. Therefore, the best approach to retinal detachments after Boston keratoprosthesis appears to be prevention: a pars plana vitrectomy at the time of keratoprosthesis implantation when indicated by pre-existing vitreoretinal pathology, annual imaging with wide-field fundus photography after keratoprosthesis implantation, and aggressive repair of significant vitreoretinal pathology once identified after keratoprosthesis surgery.
Results of the Boston Keratoprothesis
The Boston Keratoprosthesis has excellent long-term stability and safety. It is also known for having excellent optics. Autoimmune diseases, e.g., mucous membrane pemphigoid, Stevens Johnson syndrome, and severe connective tissue diseases, present significantly higher risks than other indications. Keratoprosthesis implantation carries a greater burden of postoperative care than standard penetrating keratoplasty. Successful outcomes requires patient compliance, regular follow-up, and ongoing demands on physician time. However, in cases where further keratoplasty appears futile, keratoprosthesis may be rewarding.
Instructions for Use
To make an appointment please call 617-573-3240
Click here to view Boston Keratoprosthesis bibliography
Page last updated 7/11/2019