Mona Harissi-Dagher

Advances in Boston keratoprosthesis: enhancing retention and prevention of infection and inflammation.

Advances in standard corneal transplantation since the beginning of the 20th century has restored vision to many patients with corneal blindness. Among this group of patients, there is a subgroup, such as repeat graft failures and cicatrizing diseases in whom a standard corneal transplant carries a poor prognosis. Thus, according to a recent large study, grafts for all causes remained clear in 70% of the cases after 5 years. In a separate study, only 20% of the first regrafts similarly survived, whereas all repeat regrafts failed in the same 5-year period. The outcome studies have shown similar results. Hence, the need for keratoprosthesis (KPro) as an alternative to a standard corneal transplant. The concept of using artificial material in place of a human donor cornea is not new; Pellier de Quengsy in 1789 first suggested this concept at the time of the French Revolution. For subsequent history, see Albert and Jakobiec’s Principle and Practice of Ophthalmology, 3rd ed. Approximately, a dozen centers worldwide are presently involved in the development of KPro using different materials, innovative designs and surgical techniques. Widespread use of the KPro is limited due to difficult surgical techniques of some KPro varieties, time involvement on part of the surgeon and patient, and past reputation of high rate of complications (Table 1). Most importantly there is a lack of awareness among the corneal community of the availability, efficacy, and

Importance of nutrition to corneal grafts when used as a carrier of the Boston Keratoprosthesis.

Purpose: Necrosis, melt, and perforation have historically been frequent around a Keratoprosthesis (KPro), even resulting in extrusion or endophthalmitis. Autoimmune diseases such as Stevens-Johnson Syndrome (SJS) and Ocular Cicatricial Pemphigoid (OCP) have been notorious in this respect. The purpose of this study was to compare the frequency of tissue melt after implantation of two designs of the Boston KPro, one allowing much better access of nutrition from the aqueous humor to the carrier graft. Methods: We retrospectively reviewed charts of 157 eyes implanted since 1990 with a poly (methylmethacrylate) Boston KPro, including 79 eyes implanted with the model having 8 small (1.3-mm diameter) holes in the back plate, and 78 eyes implanted with the older solid back plate. We compared the frequency of tissue melts between the two KPro designs, for all implants as well as for subgroups based on preoperative diagnosis. Results: In total, 48/157 eyes (31%) developed some degree of tissue melt around the stem, including 8/79 eyes (10%) in the back plate with holes group and 40/78 eyes (51%) in the solid back plate group (P < 0.0001). Among the melts in the back plate with holes group, 4/8 (50%) suffered from an underlying autoimmune disease such as SJS or OCP. Conclusions: The Boston KPro design with a back plate containing holes protects the overlying corneal tissue from necrosis and melts. This improved situation is likely due to increased aqueous access and better nutrition to the corneal graft cells. In addition, this study confirms earlier work regarding the particular corneal fragility of patients with autoimmune diseases.

Diffuse lamellar keratitis: Incidence, associations, outcomes, and a new classification system

Purpose: To evaluate the incidence, associations, and visual outcomes in patients with diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK). Setting: University‐based refractive surgery center, Boston, Massachusetts, USA. Methods: This retrospective review comprised 2711 eyes that had LASIK between September 1996 and September 1999. All eyes that developed DLK after LASIK were included. They were divided into type I DLK (center sparing) or type II DLK (center involved) and then subdivided into A (sporadic—DLK not diagnosed in other patients treated on the same day) or B (cluster—other patients identified with DLK). Type IA corresponded to center sparing, sporadic; type IB, center sparing, cluster; type IIA, center involved, sporadic; and type IIB, center involved, cluster. The main outcome measures were incidence of DLK after LASIK, time to diagnosis, time to resolution, and changes in best spectacle‐corrected visual acuity (BSCVA). Unpaired t tests were used for statistical analyses. Results: Thirty‐six eyes (1.3%) developed DLK. Type I occurred in 58.3% of cases (type IA, n = 18; type IB, n = 3) and type II, in 41.7% (type IIA, n = 10; type IIB, n = 5). The mean time to diagnosis was not statistically significantly different between type I (1.8 days) and type II (1.1 days). Fourteen eyes (38.9%) developed DLK after an epithelial defect, representing an odds ratio of 13 times. The association with an epithelial defect was statistically significantly greater with type I (11/21 eyes, 52.4%) than with type II (3/15 eyes, 20.0%; P = .05). The mean time to resolution was 3.5 days in type I (type IA = 3.6 days; type IB = 2.7 days). This was significantly shorter than in type II, which had a mean time to resolution of 12.1 days (type IIA = 9.3 days; type IIB = 10.2 days) (P = .001). Loss of 2 or more lines of BSCVA occurred in 2 of 5 patients with type IIB and in no patients with types IA, IB, or IIA. Conclusions: Epithelial defects after LASIK increased the risk of DLK occurrence, especially type I. Type II DLK was associated with a prolonged time to resolution and carried a significantly higher risk of BSCVA loss than type I.

Introduction to the use of the Boston keratoprosthesis

The Boston keratoprosthesis (KPro) is one of several types of artificial cornea manufactured worldwide that are being implanted in increasing numbers in patients with severe corneal diseases and graft failures. The prognosis for long-term success varies greatly between diseases, with autoimmune conditions, such as ocular cicatricial pemphigoid and Stevens–Johnson syndrome, and severe chemical burns remaining difficult. In the potentially much larger cohort with little preoperative inflammation, retention is excellent, complications are manageable and outcome is usually very good. Early implantation in congenital corneal opacities to offset amblyopia shows promise. The Boston KPro uses a ‘collar button’ design of polymethyl methacrylate that is sturdy and easily machined and polished, giving excellent vision if the remainder of the eye is healthy. This is implanted into a carrier corneal graft or into the patient’s own cornea. Holes in the back plate allow nutrition from the aqueous humor to reach the graft and long-term use of around-the-clock soft contact lenses protects the ocular surface from excessive dehydration. In nonautoimmune diseases, these measures have virtually eliminated necrosis and melt of the corneal tissue holding the device. Postoperative prophylactic antibiotics can now fully protect eyes from infection.

Boston type 1 keratoprosthesis: the CHUM experience.

OBJECTIVE To describe the characteristics, indications, complications, and outcomes of the patients who underwent Boston type 1 keratoprosthesis (KPro) surgery at the Université de Montréal affiliated Notre-Dame Hospital. DESIGN Retrospective case series. PARTICIPANTS Forty-seven eyes of 43 patients who underwent KPro surgery. METHODS The charts of all patients who underwent KPro surgery at Notre-Dame Hospital between October 2008 and February 2010 were retrospectively reviewed. Preoperative, intraoperative, and postoperative parameters were collected and analyzed. RESULTS The indication for Boston type 1 KPro was corneal graft failure in 27 eyes; 20 eyes had KPro as a primary procedure. Preoperative diagnoses included aniridia (34%), mechanical trauma (11%), infections (9%), surgery-related bullous keratopathy (9%), chemical burns (9%), corneal dystrophies (9%), and Stevens-Johnson syndrome (2%). A known history of glaucoma was present in 36 eyes (77%). Median preoperative best-corrected visual acuity (BCVA) was hand motion (range, 20/100 to light perception). The assembly of the KPro and surgery were uneventful in all cases. Mean follow-up was 10±5 months. MedianBCVA at last follow-up was 20/150 (range, 20/30 to no light perception). The device retention rate was 100% at the end of the follow-up period. Postoperative complications included retroprosthetic membrane in 12 eyes (26%) and glaucoma progression in 11 eyes (23%). CONCLUSIONS Our study demonstrates an excellent retention rate of the Boston type 1 KPro and an improvement of BCVA in the majority of patients. Many patients undergoing KPro surgery have ocular comorbidities that require ongoing care to prevent further vision loss following KPro surgery.

The Role of Soft Contact Lenses as an Adjunct to the Boston Keratoprosthesis

After the implantation of the Boston keratoprosthesis (KPro), the corneal surface becomes vulnerable to evaporative forces. Epithelial defects, stromal thinning, dellen formation, and melt can occur, especially in eyes with an underlying inflammatory disease such as Stevens Johnson Syndrome and ocular cicatricial pemphigoid. In an effort to protect the ocular surface from drying and to promote a healthy and hydrated tissue, soft contact lenses (SCL) have been routinely used at the conclusion of KPro surgery at the Massachusetts Eye and Ear Infirmary (MEEI) since the year 2000 and worn indefinitely. The purpose of this study is to further evaluate the long-term use of SCL in the postoperative management of KPro patients in terms of prolonging retention time, enhancing cosmesis, and correcting refractive errors.

The Boston Keratoprosthesis in severe ocular trauma

BACKGROUND In eyes with corneal disease and opacity so severe that standard corneal transplantation carries a poor prognosis, a keratoprosthesis (KPro) may still be successful in providing functional visual acuity. The purpose of this study was to determine the outcome of Boston KPro implantation in the rehabilitation of severe ocular trauma. METHODS This is a retrospective study of 30 eyes (30 patients) with severe ocular trauma that underwent Boston KPro type I implantation at the Massachusetts Eye and Ear Infirmary. Of these 30 eyes, 6 had mechanical trauma, 21 had chemical burns, and 3 had thermal burns. The measures used in this review are 5-fold: (i) anatomic success; (ii) number of postoperative repair procedures performed; (iii) preoperative and postoperative visual acuity; (iv) number of eyes with concomitant preoperative retinal or optic nerve damage prior to KPro surgery; and (v) incidence of postoperative complications. RESULTS Preoperative visual acuity ranged from counting fingers to light perception (median: hand motion). Best-corrected postoperative visual acuity ranged from 20/20 to no light perception (median: 20/80). Anatomic success was achieved in 5 out of 5 mechanically traumatized eyes, 14 out of 17 eyes with chemical burns, and 3 out of 3 eyes with thermal burns. Repair procedures were done in 8 of the 17 chemically burned eyes. The number of eyes with concomitant preoperative ocular disease was 2 out of 6 in the mechanical trauma group, 10 out of 21 in the chemical burn group, and 1 out of 3 in the thermal burn group. The incidence of postoperative complications was greater in the chemical burn group than in either the mechanical trauma or the thermal burn group. INTERPRETATION The Boston KPro can provide considerable visual improvement and a long-term anatomic retention rate in severely traumatized eyes. The overwhelming danger in severe chemical burns is glaucoma progression despite a functioning tube implant and normal intraocular pressure.

Review of endophthalmitis following Boston keratoprosthesis type 1

Endophthalmitis remains one of the most damaging and challenging complications following Boston keratoprosthesis type 1 (KPro) surgery. The authors reviewed the literature from 2001 onward to identify cases of endophthalmitis following KPro surgery and present an additional case of endophthalmitis in a patient with Stevens Johnson syndrome. The prevalence of endophthalmitis between 2001 and 2011 was 5.4%. Gram-positive bacteria are the most common agents responsible for endophthalmitis in this patient population while gram-negative bacteria and fungi are emerging pathogens. Risk factors for endophthalmitis include preoperative diagnosis of cicatricial disease and postoperative infectious keratitis, glaucoma drainage device erosion and non-compliance with antibiotic prophylaxis. Additional studies on the prevention and treatment of endophthalmitis are required to improve the overall prognosis of these patients.

Prevalence, Progression, and Impact of Glaucoma on Vision After Boston Type 1 Keratoprosthesis Surgery

PURPOSE To report glaucoma outcomes after Boston type 1 keratoprosthesis (KPro) surgery, in particular, glaucoma prevalence, progression, and treatment. DESIGN Consecutive, retrospective, interventional case series. METHODS setting: Tertiary care institution. study population: Thirty-eight eyes in 38 patients. intervention: KPro surgery. main outcome measures: Visual acuity (VA), intraocular pressure, visual fields, optic nerve status, and glaucoma treatment. RESULTS Glaucoma diagnosis was known before surgery in 29 patients (76%; 14 had undergone previous surgery) and was diagnosed after surgery in 34 patients (89%) after a mean ± standard deviation of 16.5 ± 4.7 months of follow-up. The number of patients taking intraocular pressure-lowering medications increased from 19 (50%) before surgery to 28 (76%) after surgery (P = .017). Twenty-four patients (63%) were taking at least 1 additional glaucoma medication at their most recent postoperative visit. Eight patients (21%) had glaucoma progression (visual field progression, need for surgery, or both). Fifteen patients (40%) had a cup-to-disc ratio of 0.85 or more. Five patients required glaucoma surgery. VA was limited by glaucoma in 14 patients (37%), 11 of whom had a VA of 20/200 or worse. Five such patients (13%) had a dramatic improvement in VA, then progressed to end-stage glaucoma with fixation loss. Visual fields were limited by glaucoma in 25 patients (66%; mean Swedish Interactive Threshold Algorithm Fast mean defect, -20.3 ± 8.8 decibels; n = 18). CONCLUSIONS Most KPro candidates have glaucoma, which may deteriorate in a subset of patients after surgery. Dramatic VA improvement after KPro surgery does not preclude the need for rigorous monitoring for glaucoma progression. A low threshold should be used to treat suspicion of even slightly elevated intraocular pressure.

Femtosecond laser astigmatic keratotomy for postkeratoplasty astigmatism

CASE REPORT Two eyes of 2 patients with high astigmatism following penetrating keratoplasty were treated with femtosecond laser-assisted paired arcuate keratotomies in the donor cornea. Outcome measures included best-corrected visual acuity, refraction, keratometry, and topographic findings. The preoperative cylinder was 8.5 diopters (D) in the first case and 7.0 D in the second case. Respectively, the postoperative cylinder improved to 4.9 D after a follow-up of 8 months and to 4.3 D after a follow-up of 7 months. Best-corrected visual acuity improved from 20/100 to 20/30 in the first case and from 20/200 to 20/60 in the second case. No complications were encountered; no microperforations were observed, and neither graft rejection nor failure occurred. COMMENTS The results of astigmatic keratotomy performed with femtosecond laser were reliable and predictable. Femtosecond astigmatic keratotomy may prove to be a safe procedure with satisfactory results.