Boston Keratoprosthesis Type 1 Surgery: Use of Frozen Versus Fresh Corneal Donor Carriers
Purpose: This study aims to determine whether frozen corneas can be successfully used as carriers of the Boston keratoprosthesis (KPro). Methods: Prospective study of 37 patients undergoing KPro surgery with fresh or frozen corneas as carriers. Patients were randomized to receive either a fresh corneal graft or a frozen corneal graft during implantation of the Boston KPro. The randomization depended on availability of fresh versus frozen corneas offered by the local eye bank. All surgeries were performed by the same experienced surgeon. Outcome measures included retention of the device, level of preoperative and postoperative visual acuities (VAs), and complications. Results: The indication for Boston KPro was corneal graft failure in 24 eyes; 13 patients had KPro as a primary procedure. The assembly of the Boston KPro and surgery were uneventful in all cases. Mean follow-up was 9.65 months. Median preoperative VA was counting fingers (range, 20/100 to light perception) in the fresh cornea group (19 eyes) and hand motions (range, 20/150 to light perception) in the frozen cornea group (18 eyes). Median postoperative VA were 20/150 (range, 20/30 to hand motions) and 20/150 (range, 20/40 to counting fingers) in the fresh and frozen cornea groups, respectively. Inflammation and retroprosthetic membrane formation were the most common complications with similar rates between the 2 groups. The device retention rate was 100% at the end of the follow-up period. Conclusions: Frozen and fresh corneal donors seem equally efficient and safe as carriers of the Boston KPro with similar recuperation of VA and no untoward complications, such as melt, leaks, or endophthalmitis.
A Stepwise Approach to Donor Preparation and Insertion Increases Safety and Outcome of Descemet Membrane Endothelial Keratoplasty
Purpose: Lamellar techniques for selective replacement of diseased corneal structures have recently been improved. Descemet membrane endothelial keratoplasty (DMEK) allows the sole replacement of the endothelium-Descemet membrane layer (EDM). However, widespread use of DMEK is currently limited because of problems with donor preparation namely the tearing of the Descemet membrane and the difficulty to unfold the EDM graft in the anterior chamber (AC). Methods: A standardized DMEK procedure that allows safe preparation of EDM, atraumatic introduction of EDM into the AC, reliable orientation of EDM during surgery, and stepwise unfolding within the AC is described in 80 patients. Visual acuity and corneal endothelial cell density were assessed. Results: A stepwise approach using a novel bimanual underwater technique to harvest EDM from donor corneal buttons allows reproducible generation of grafts without tearing the Descemet membrane. Injection of the EDM roll into the AC is achieved by use of a standard injector cartridge, whereas the depth of AC is maintained by an irrigation handpiece. Marks at the margin of EDM allow orientation. Finally, unfolding EDM in the AC is achieved by sequential use of water jets and air bubbles. In the early phase of the learning curve, 4 patients were regrafted because of graft failure. Endothelial cell density decreased from 2600 ± 252 to 1526 ± 341 cells per square millimeter 1 month after DMEK. Conclusions: A novel technique for graft preparation and EDM injection results in improved safety with a high rate of successful DMEKs.
Prevalence of Sleep Apnea in Patients With Keratoconus
Purpose: To determine the prevalence of obstructive sleep apnea (OSA) in patients with keratoconus and evaluate the risk of developing OSA in this patient population. Methods: Three hundred sixty-two patients diagnosed with keratoconus by a single physician at the Duke Eye Center over a 14-year period were identified. A power calculation was done a priori, and based on this, the first 101 patients were enrolled. All patients were administered a standardized questionnaire regarding medical and ocular health. Those without the history of OSA were administered the Berlin questionnaire to determine their risk for developing OSA. Statistical analysis was performed to determine the prevalence of OSA and to compare it with previously reported prevalence data in the general population. Results: The prevalence of previously diagnosed OSA was 18% (18 of 101); all reported having a formal sleep study in the past. Of the remaining patients (n = 83), 47% (39 of 83) were determined to be at high risk for the development of OSA determined by the Berlin questionnaire score. Comorbid health conditions included hypertension (37%), acid reflux (30%), diabetes mellitus (20%), and seasonal allergies (66%). A history of penetrating keratoplasty was found in 48%. The average body mass index of the study population was 31.2 (median, 28.4). Conclusions: Keratoconus patients have a higher prevalence of OSA compared with that accepted for the general population. A striking number of our patients without previous diagnosis of OSA seem to be at high risk for developing OSA, supporting our recommendation for a greater awareness among clinicians who might otherwise overlook this systemic condition and its consequences.
What Causes Keratoconus?
Purpose: The etiology of keratoconus has been the subject of numerous studies. Here, we review the body of literature that attempts to determine what causes keratoconus. Methods: A review of the published literature was performed to evaluate the possible causes of keratoconus and how the different etiologies may play a role in the development of this disease. Results: Peer-reviewed published papers and recent abstracts concerning the different etiologies of keratoconus were reviewed and discussed. Biochemical, genetic, and environmental factors are reviewed. The role of eye rubbing and atopic disease are explored. Conclusions: We agree with the hypothesis that there is a genetic predisposition that requires a ?second hit? or environmental event to elicit progressive disease in keratoconus. Eye rubbing may serve as the ?second hit? in some predisposed individuals. Inflammatory mediator studies question if keratoconus is really a noninflammatory thinning disorder of the cornea.