Paul C. Kang

Trends in the indications for penetrating keratoplasty, 1980-2001.

Purpose: To study the leading indications and changing trends for penetrating keratoplasty (PK) over the past 3 decades. Methods: This is a retrospective review of 696 cases of PK. The indications for PKs performed at the Duke University Eye Center during the years 1980-1981, 1990- 1991, and 2000-2001 were tabulated to determine trends over the past 3 decades. The main outcome measures were indications for PK. Results: During this study, 696 PKs were performed. The leading indications for PK and their respective frequencies during 1980-1981, 1990-1991, and 2000-2001 were failed grafts (10.8%, 19.0%, 27.0%, respectively), pseudophakic bullous keratopathy (PBK)/aphakic bullous keratopathy (ABK) (19.4%, 20.6%, 16.7%, respectively), Fuchs dystrophy (15.6%, 13.0%, 23.8%, respectively), keratoconus (13.4%, 8.2%, 11.8%, respectively), and corneal scar (7.0%, 8.9%, 10.7%, respectively). The number of PKs for failed grafts and Fuchs dystrophy increased over time. Conclusions: In this study, failed graft has gradually become the leading indication for PK, whereas most other studies have reported PBK as the leading indication. Unlike many other studies, Fuchs dystrophy was a common indication for PK.

Novel tissue adhesives to secure laser in situ keratomileusis flaps

Purpose: To evaluate 2 novel biodendrimer tissue adhesives in sealing and securing laser in situ keratomileusis (LASIK) flaps. Setting: Duke University Eye Center, Durham, North Carolina, USA. Methods: Laser in situ keratomileusis flaps were created in 10 human eye‐bank eyes using the Hansatome microkeratome system (Bausch & Lomb). These eyes were divided into 2 groups. Flaps in the first group (n = 4) were secured with a laser‐activated biodendrimer adhesive along the flap edge. In the second group (n = 6), the flaps were secured with a self‐gelling dendritic adhesive. Dry Merocel sponges (Medtronic Solan) were used to test the strength of flap adherence in both groups. Further testing was performed in the second group. The hinges of these flaps were cut with a scalpel blade and fluorescein dye was injected under the flap to observe potential dye leakage along the flap edge. Results: Laser in situ keratomileusis flaps sealed with both adhesives were secure with no flap dislocation. There was no leakage of fluorescein dye observed in the second group. Both adhesives were easy to apply, clear when dry, and had a soft rubbery consistency. Conclusions: Two novel biodendrimer adhesives successfully sealed and secured LASIK flaps. These adhesives may prove to be an effective alternative for treating LASIK flap complications such as epithelial ingrowth or flap dislocation.

Preparation of donor lamellar tissue for deep lamellar endothelial keratoplasty using a microkeratome and artificial anterior chamber system: endothelial cell loss and predictability of lamellar thickness.

BACKGROUND AND OBJECTIVE To measure endothelial cell loss and predictability of lamellar thickness after preparing donor tissue for deep keratoplasty with an artificial anterior chamber and microkeratome. MATERIALS AND METHODS A microkeratome set at a depth of 350 microm and a diameter of 9 mm was used to obtain ten lamellar lenticules from corneoscleral rims mounted in an artificial chamber. A punch trephine then was used to cut the donor tissue 7 mm in diameter. Specular microscopy was performed to evaluate endothelial cell density before the procedure, after cutting with the microkeratome, and after trephination. Pachymetry was performed to determine the predictability of lenticule thickness, before the procedure and after microkeratome incision. RESULTS Mean post-microkeratome endothelial cell loss was 79 +/- 88 cells/mm2 and post-punch trephination was 85 +/- 94 cells/mm2. This represented a mean percentage loss of 3.2% and 3.5% for the respective steps of this procedure. Nine of the ten lenticules were cut within +/- 75 microm of the intended 350-microm thickness. CONCLUSIONS Preparing donor lenticules for deep lamellar endothelial keratoplasty with a microkeratome with artificial chamber system caused a relatively small loss of endothelial cells (6.7% of the total) and a reproducible thickness. This may have advantages over manual preparation techniques.

Recurrent Corneal Erosion Syndrome: A Study of 364 Episodes.

The purpose of the study was to investigate the management of recurrent corneal erosion syndrome (RES). A retrospective case series design was employed in which all RES cases presenting to the Duke University Eye Center from 1995 to 2002 were included. In total, 364 episodes of RES occurred in 261 patients during the study period. Of this 61% of patients were female (P < .001), average age was 46.0 years, and etiologies included trauma (51.3%), anterior basement membrane dystrophy (29.1%), other etiologies (10.3%) and unknown (9.2%). Treatments included conservative therapy (83.2%), anterior stromal puncture (ASP)(12.6%) and phototherapeutic keratectomy (PTK)(4.1%). Recurrence by treatment was 31.0% for conservative therapy, 23.9% for ASP and 26.7% for PTK. Subjects treated with ASP and PTK had failed prior treatment efforts. Conclusions include that RES was commonly associated with trauma and the female gender, and that one-third of conservatively treated episodes and one-quarter of surgically treated episodes (ASP or PTK) recurred.

Implantation of verisyse phakic intraocular lens to correct myopic refractive error after penetrating keratoplasty in pseudophakic eyes.

Purpose: We report 2 cases in which a Verisyse phakic intraocular lens (PIOL) was used to successfully treat high myopia after penetrating keratoplasty (PK) in pseudophakic patients. Methods: Case 1 involved a 69-year-old pseudophakic man with a manifest refraction (MR) of -6.50 + 1.75 × 048 and a best spectacle corrected visual acuity (BSCVA) of 20/40 approximately 16 months after PK in the right eye. Case 2 was a 78-year-old pseudophakic man who had an MR of -9.00 + 5.75 × 132 with a BSCVA of 20/100 approximately 24 months after PK in the left eye. Results: In case 1, 10 months after Verisyse PIOL implantation, the MR was pl +2.00 × 135 with a BSCVA of 20/30. Endothelial cell density (ECD) in this patient decreased from 1926.1 to 815.3 cells/mm2 over 17 months. In case 2, 24 months after Verisyse PIOL implantation, the MR was -3.25 + 3.50 × 105 with a BSCVA of 20/60. ECD in this patient decreased from 2108.4 to 753.8 cells/mm2 in 30 months. Conclusion: The Verisyse PIOL may provide an alternative method to correct high myopia for anisometropia in pseudophakic patients after PK. In this report, PIOL implantation was associated with a decrease in ECD. Further studies are required to determine the long-term effects and ultimate safety of PIOL placement on the integrity of the cornea endothelium after corneal transplant in pseudophakic patients.

Comparison and analysis of FDA reported visual outcomes of the three latest platforms for LASIK: wavefront guided Visx iDesign, topography guided WaveLight Allegro Contoura, and topography guided Nidek EC-5000 CATz

Purpose To compare and analyze the differences in visual outcomes between Visx iDesign Advanced WaveScan Studio™ System, Alcon Wavelight Allegro Topolyzer and Nidek EC-5000 using Final Fit™ Custom Ablation Treatment Software from the submitted summary of safety and effectiveness of the US Food and Drug Administration (FDA) data. Methods In this retrospective comparative study, 334 eyes from Visx iDesign, 212 eyes from Alcon Contour, and 135 eyes from Nidek CATz platforms were analyzed for primary and secondary visual outcomes. These outcomes were compared via side-by-side graphical and tabular representation of the FDA data. Statistical significance was calculated when appropriate to assess differences. A P-value <0.05 was considered statistically significant. Results The mean postoperative uncorrected distance visual acuity (UDVA) at 12 months was 20/19.25±8.76, 20/16.59±5.94, and 20/19.17±4.46 for Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. In at least 90% of treated eyes at 3 months and 12 months, all three lasers showed either no change or a gain of corrected distance visual acuity (CDVA). Mesopic contrast sensitivity at 6 months showed a clinically significant increase of 41.3%, 25.1%, and 10.6% for eyes using Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. Photopic contrast sensitivity at 6 months showed a clinically significant increase of 19.2%, 31.9%, and 10.6% for eyes using Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. Conclusion FDA data for the three platforms shows all three were excellent with respect to efficacy, safety, accuracy, and stability. However, there are some differences between the platforms with certain outcome measurements. Overall, patients using all three lasers showed significant improvements in primary and secondary visual outcomes after LASIK surgery.

A comparison of three methods for trephining donor corneal buttons: endothelial cell loss and microscopic ultrastructural evaluation.

Purpose: To evaluate the ultrastructure of the cut edge and associated endothelial cell loss following donor cornea trephination with a standard punch, vacuum punch, and vacuum trephine and artificial anterior chamber system. Materials and Methods: This laboratory investigation compared trephinations (8.0 mm) performed on human corneas using either a standard posterior punch (n = 12), vacuum posterior punch (n = 12), or vacuum trephine and artificial anterior chamber system (n = 12). Specular microscopy was performed before and after trephination to determine central endothelial cell density. Light and scanning electron microscopy were performed to evaluate the structure of the trephined edge. Endothelial cell-free distances from the trephinated edges were measured on light microscopy sections. Results: Central endothelial cell loss (cells/mm2) after trephination was –14.0 ± 49.9 (SD) for the standard posterior punch, –85.6 ± 87.0 for the vacuum posterior punch, –116.0 ± 223.1 for the vacuum trephine and artificial anterior chamber system. Endothelial cell-free distances from the trephined margin were 63 ± 22 μm, 85 ± 13 μm, and 123 ± 48 μm for the three respective methods. The edges of grafts cut with anterior trephination were inward sloping from the epithelial to endothelial surfaces, while both posterior punches created outward sloping edges. Increased fibrillar disruption at edges was seen following anterior trephination. Conclusion: Different trephination methods produce distinct cut morphologies with the anterior trephination approach, resulting in more irregular margins. The anterior approach was associated with increased variability and greater endothelial cell loss than the studied posterior approaches. The use of corneal scissors may contribute to the morphologic features of the corneal button seen following anterior trephination.