Michael W. Belin

Retention Of The Boston Keratoprosthesis Type 1: Multicenter Study Results

OBJECTIVE To report the retention rate of the Boston keratoprosthesis type 1 and to identify risk factors for keratoprosthesis loss. DESIGN Cohort study. PARTICIPANTS A total of 300 eyes of 300 patients who underwent implantation of the Boston keratoprosthesis type I device between January 2003 and July 2008 by 19 surgeons at 18 medical centers. METHODS Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and subsequently analyzed at a central data collection site. MAIN OUTCOME MEASURES Keratoprosthesis retention. RESULTS A total cumulative number of 422 life-years of device implantation are included in this analysis. The average duration of follow-up was 17.1 ± 14.8 months, with a range of 1 week to >6.1 years. Ninety-three percent of the 300 Boston keratoprosthesis implants were retained at their last follow-up, corresponding to a retention time of 396 patient-years or 1.42 years/keratoprosthesis. The probability of retention after 1 year and 2 years was 94% and 89%, respectively. During the study period, 21 (7%) eyes failed to retain the device; the reasons for keratoprosthesis loss include sterile keratolysis (9), fungal infections (8), dense retroprosthetic membranes (3), and bacterial endophthalmitis (1). Multivariate analysis demonstrated 3 independent risk factors for keratoprosthesis loss: autoimmune cause (hazard ratio [HR], 11.94; 95% confidence interval [CI], 3.31-43.11), ocular surface exposure requiring a concomitant tarsorrhaphy (HR, 3.43; 95% CI, 1.05-11.22), and number of prior failed penetrating keratoplasties (HR, 1.64; 95% CI, 1.18-2.28). CONCLUSIONS The Boston keratoprosthesis type 1 seems to be a viable option for eyes that are not candidates for penetrating keratoplasty (PK). Ocular surface disease due to an autoimmune cause demonstrated the lowest retention rate. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Evaluation of corneal shape and biomechanics before LASIK.

The preoperative evaluation is of critical importance for success in laser in situ keratomileusis (LASIK). This examination should fulfill 3 main purposes: counseling and educating the candidates, surgery planning, and screening for cases at higher risk for complications. It is critical to interview each refractive patient to assess their individual needs and to provide realistic expectations. A thorough ophthalmologic examination is mandatory, including specific complementary examinations to characterize many aspects of the cornea and the optics of the eye. In fact, it is notable that refractive surgery has motivated tremendous development for advanced diagnostic methods, among many others advancements and innovations in Ophthalmology. One of the most important aspects of the preoperative examination of LASIK candidates is to screen cases at risk for progressive ectasia.

Long-term outcomes of Boston type 1 keratoprosthesis implantation: A retrospective multicenter cohort

PURPOSE To study the long-term outcomes of Boston type 1 keratoprosthesis (KPro) surgery. DESIGN Retrospective, multicenter case series. PARTICIPANTS A total of 158 eyes of 150 patients underwent KPro implantation at 5 participating tertiary centers in the United States between January 2003 and December 2006. Of those, 139 eyes of 133 patients were included in the analyses. METHODS The medical records of consecutive adult patients who received KPro surgery were reviewed. All patients with at least 1 postoperative visit were retained in the outcomes analyses. In eyes in which a repeat KPro procedure was performed, only the outcomes of the initial surgery were analyzed. MAIN OUTCOME MEASURES Visual acuity (VA) outcomes, postoperative complications, and device retention. RESULTS The mean follow-up was 46.7 ± 26 months with all but 4 eyes having at least 6 months of follow-up. Preoperatively, only 10.8% of the eyes had VA of ≥ 20/200. Postoperatively, the VA in 70% of eyes improved to ≥ 20/200. The probability of maintaining VA of ≥ 20/200 at 7 years was 50%. The device retention rate was estimated at 67% at 7 years. The 7-year cumulative incidence of complications was 49.7% for retroprosthetic membrane formation, 21.6% for glaucoma surgery, 18.6% for retinal detachment, and 15.5% for endophthalmitis. CONCLUSIONS Although the risk for complications with longer follow-up seemed to increase, this large multicenter cohort demonstrates favorable outcomes with KPro, with a large number of patients achieving and retaining useful vision over a 7-year period.

Dynamic ultra high speed Scheimpflug imaging for assessing corneal biomechanical properties

OBJECTIVE: To describe a novel technique for clinical characterization of corneal biomechanics using non-invasive dynamic imaging. METHODS: Corneal deformation response during non contact tonometry (NCT) is monitored by ultra-high-speed (UHS) photography. The Oculus Corvis ST (Scheimpflug Technology; Wetzlar, Germany) has a UHS Scheimpflug camera, taking over 4,300 frames per second and of a single 8mm horizontal slit, for monitoring corneal deformation response to NCT. The metered collimated air pulse or puff has a symmetrical configuration and fixed maximal internal pump pressure of 25 kPa. The bidirectional movement of the cornea in response to the air puff is monitored. RESULTS: Measurement time is 30ms, with 140 frames acquired. Advanced algorithms for edge detection of the front and back corneal contours are applied for every frame. IOP is calculated based on the first applanation moment. Deformation amplitude (DA) is determined as the highest displacement of the apex in the highest concavity (HC) moment. Applanation length (AL) and corneal velocity (CVel) are recorded during ingoing and outgoing phases. CONCLUSION: Corneal deformation can be monitored during non contact tonometry. The parameters generated provide clinical in vivo characterization of corneal biomechanical properties in two dimensions, which is relevant for different applications in Ophthalmology.

Background, Immunology, and Pharmacology

Systemic cyclosporin A (CsA) is currently being used for immunosuppression in solid organ transplantation. Its unique mechanism of action and low myelotoxicity have vastly improved the prognosis for patient survival. A reversible and irreversible nephrotoxicity has complicated its use. CsA works via the inhibition of both lymphokine release and subsequent activation of cytotoxic T cells. The corneal allograft model presents several unique features that make it amenable to local immunosuppressant therapy. Following topical application, CsA corneal levels have been obtained above the experimentally determined levels necessary for local immunosuppression. CsA represents one of a new class of specific, potent immunomodulators, which may improve the prognosis for patients at high risk for allograft rejection.

Risk factors for the development of retroprosthetic membranes with Boston Keratoprosthesis type 1: multicenter study results

OBJECTIVE The purpose of this study was to identify possible risk factors for retroprosthetic membrane (RPM) development in a large, multicenter cohort of patients receiving a Boston type 1 keratoprosthesis. DESIGN Cohort study. PARTICIPANTS The final analysis included 265 eyes of 265 patients who underwent implantation of a Boston keratoprosthesis type I device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers. METHODS Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and subsequently analyzed at a central data collection site. MAIN OUTCOME MEASURES The primary outcome was the presence or absence of an RPM during the follow-up period. RESULTS The average age of patients was 63.3±19.1 years, 48.5% of the patients were female, and 52.5% of procedures were performed on the right eye. The mean follow-up time was 17.8±14.9 months. The majority (85.4%; n = 222) had undergone an average of 2.2±1.2 (range, 1-8) penetrating keratoplasties before keratoprosthesis implantation, and 38 eyes (14.6%) received a primary keratoprosthesis. The overall RPM formation rate was 31.7% (n = 84). The most significant risk factor for RPM development was infectious keratitis (as a surgical indication for keratoprosthesis surgery itself), resulting in a rate of RPM formation of 70.6%. As an independent risk factor, the hazard ratio (HR) of RPM development in these eyes was 3.20 (95% confidence interval, 1.66-6.17). Aniridia was also an independent risk factor for RPM development (HR, 3.13; 95% confidence interval, 1.10-8.89). CONCLUSIONS Formation of RPM is a common complication of keratoprosthesis surgery, occurring in approximately one-third of cases. Eyes at the highest risk of RPM development are those receiving corneal replacement for infectious keratitis and aniridia.

Scheimpflug imaging for keratoconus and ectatic disease

Scheimpflug cross-sectioning anterior segment imaging offers significant advantages over traditional placido based curvature analysis and ultrasound pachymetry. The accurate measurement of both the anterior and posterior corneal surfaces and the anterior and posterior lens allows for the creation of a three-dimensional reconstruction of the anterior segment. Changes on both the posterior cornea and/or corneal thickness map are earlier indicators of ectatic change than would otherwise be identifiable with only anterior curvature and ultrasonic pachymetry. Scheimpflug imaging also covers significantly more of the cornea than was possible with placido based devices. This added coverage is critical in the proper diagnosis of peripheral diseases such as pellucid marginal degeneration (PMD).

Clinical profile and early surgical complications in the Cornea Donor Study.

Purpose: The Cornea Donor Study was designed to investigate the safety and efficacy of older donor corneal tissue compared with younger donor tissue in recipient eyes at moderate risk to the graft from progressive endothelial failure. Baseline patient data, including indications for transplant, intraoperative complication rates, and early postoperative complication rates are described herein. Methods: This study was a multicenter prospective, double-masked, controlled clinical trial. Results: Fuchs dystrophy was the most common indication for corneal transplantation (61%). Intraoperative complications occurred in 33 (3%) patients. A persistent epithelial defect was the most commonly reported postoperative complication, occurring in 92 patients (8%). Conclusion: Intraoperative and postoperative complication rates were low. There was no apparent association between donor or recipient age and either intraoperative or early postoperative complication rates.

Posterior Elevation in Keratoconus

Dear Editor: In the September 2008 issue, de Sanctis et al provide novel data on posterior corneal elevation, along with sensitivity and specificity for detecting keratoconus and subclinical keratoconus. The authors report that the posterior elevation measurements were taken as the maximum value above the best-fit sphere within the central 5 mm of the posterior cornea. Although this is a standardized method of measurement, we feel it reduces specificity for the disease process being evaluated. A fixed circular area of 5-mm diameter centered on the posterior cornea incorporates astigmatic elevation into the calculation of average normal elevation. This artificially inflates the normal elevation measurements and reduces their screening utility. When collecting elevation data in this manner (maximum elevation in a 5-mm zone), an attempt must be made to distinguish a normal astigmatic pattern of elevation from abnormal ectatic elevation (Figure 1, available online at http://aaojournal.org). This pattern classification should then be included in the disease determination process. By not doing this, the authors have overlapped normal astigmatic elevation with abnormal ectatic elevation, and limited screening ability. In recent work (Khachikian SS, Belin MW. Normal Values for Corneal Elevation Using the Pentacam Eye Scanner. Presented at: ESCRS Winter Congress, February 2008, Barcelona, Spain), we presented values for anterior and posterior elevation for normal eyes and those with keratoconus. The values were obtained at the corneal apex and thinnest point with a fixed 8-mm, best-fit-sphere calculation zone. These are 2 points that can be easily and consistently identified when looking at elevation maps from different patients. Moreover, the thinnest point measurement has a known association with keratoconus, the disease

What's in a Name: Keratoconus, Pellucid Marginal Degeneration, and Related Thinning Disorders

PURPOSE To discuss the implications of the current nomenclature and use of current diagnostic modalities on the classification and treatment of pellucid marginal degeneration and keratoconus. DESIGN Perspective analysis of the literature. METHODS Analysis of published reports on the various treatment methods for pellucid marginal degeneration and keratoconus, and the technologies used in these studies to support the diagnosis and classification of these ectatic disorders. RESULTS Many studies exploring the different treatment modalities for pellucid marginal degeneration and keratoconus rely mainly on anterior curvature maps to establish the diagnosis of these ectatic disorders, and either do not utilize or disregard information provided by pachymetric maps and posterior elevation maps. In addition, the interchangeability of the nomenclature used to describe these disorders in the literature makes it even more difficult for the clinician to determine the applicability of the results to their patient population. CONCLUSIONS We propose that future studies minimally include anterior and posterior elevation maps, anterior curvature topography, and full pachymetric maps. This will allow practitioners a better understanding of the study population, and allow them to ascertain when and in whom the treatment modality being explored may be applicable.