Bruce D. Allan

Corneal transplant rejection rate and severity after endothelial keratoplasty.

Purpose: To examine the corneal transplant rejection rate and the rate of graft failure subsequent to rejection in the first 2 years after endothelial keratoplasty (EK) and to compare this to background data for similar cases of penetrating keratoplasty (PK). Methods: Anonymized data from consecutive cases of EK [deep lamellar (DLEK) or Descemet stripping (DSEK)] for Fuchs corneal endothelial dystrophy or pseudophakic bullous keratopathy operated on before August 2004 were collected in 4 participating centers. The number and timing of rejection episodes and cases of subsequent graft failure were recorded, together with the time to cessation of topical steroid medication. Two-year postoperative findings were compared with background data for similar patients undergoing PK recorded in the Swedish Corneal Transplant Registry. Results: Rejection episodes were less frequent after EK than PK (P = 0.035). Fifteen (7.5%) of 199 EK cases had a rejection episode in the first 2 years after surgery versus 92 (13%) of 708 PK cases. Graft failure after rejection in EK may have been less frequent than in PK (P = 0.063), with only 1 (6.7%) case of rejection after EK versus 26 (28.3%) cases of rejection after PK proceeding to graft failure. A strong trend toward continued use of low-dose topical steroid medication was observed in the EK group. Eighty percent of EK patients were still taking topical steroid medication 2 years after surgery, whereas topical steroid medication had been ceased within a year of surgery in almost all PK patients in the comparator group. Conclusions: Corneal transplant rejection is less frequent and may be less severe after EK than after PK. It is not yet clear whether these apparent differences are simply a product of relatively prolonged postoperative topical steroid cover in EK patients.

Fixed dilated pupil (Urrets-Zavalia syndrome) after air/gas injection after deep lamellar keratoplasty for keratoconus.

PURPOSE To describe three cases of fixed dilated pupil and presumed iris ischemia (Urrets-Zavalia syndrome) after anterior chamber air/gas injection after deep lamellar keratoplasty for keratoconus. METHODS Interventional case series. Three eyes of three patients with keratoconus underwent deep lamellar keratoplasty and intraoperative or postoperative injection of air/gas in the anterior chamber to appose the host-donor lamellar graft interface. RESULTS Urrets-Zavalia syndrome was diagnosed on clinical grounds in three cases and was associated with the Descemet membrane microperforation intraoperatively and introduction of air/gas into the anterior chamber intraoperatively or postoperatively. CONCLUSION A fixed dilated pupil is an uncommon complication of penetrating keratoplasty for keratoconus that can also develop after deep lamellar keratoplasty. Leaving an air or gas bubble in the anterior chamber of a phakic eye after deep lamellar keratoplasty is a risk factor and should therefore be avoided.

Combined small incision phacoemulsification and trabeculectomy

ABSTRACT A method of combined cataract extraction and trabeculectomy is described in which phacoemulsification is performed through a 3.5 mm incision with insertion of a foldable hydrogel lens. This procedure is suitable for most cases in which glaucoma and cataract are coincident. In an initial series of ten patients followed for nine months, all those without additional pathology achieved a corrected visual acuity of 20/40 or better. The maximum induced astigmatism was 0.5 diopters (D), with no change or a reduction in astigmatism in seven patients (70%). Astigmatic shift between week 1 and three months was minimal (average = 0.075 D), with little change thereafter. Intraocular pressures were controlled (≤21 mm Hg) without adjunctive medication in all but one of the patients at nine months. This combined procedure preserves the principal advantages of small incision phacoemulsification: low induced astigmatism, early refractive stabilization, and rapid visual rehabilitation. In addition, reducing the extent of tissue dissection may reduce the stimulus to wound healing and early filtration failure.

Hydroxyapatite promotes superior keratocyte adhesion and proliferation in comparison with current keratoprosthesis skirt materials

Aim: Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors’ aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses. Methods: Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy. Results: Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). ß1 integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent. Conclusions: Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates.

Legeais BioKpro III keratoprosthesis implantation: long term results in seven patients

Aims: The long term results of the Legeais BioKpro III keratoprosthesis are presented for seven patients with severe corneal scarring. Methods: The study took place at Moorfields Eye Hospital, London. Patients had either end stage ocular surface disease or corneal opacification after multiple failed graft surgery, with the potential for significant visual improvement. After insertion the device was covered with a conjunctival flap or buccal mucous membrane graft, which was later opened to expose the optic. The outcome measures were vision, complications, and retention of the device. Results: The BioKpro III was inserted into seven patients with severe corneal scarring: ocular cicatricial pemphigoid, measles keratitis, thermal injury, Stevens-Johnson syndrome, aniridia, chemical injury, and congenital rubella. The follow up was 18–48 months. The keratoprosthesis failed in six, because of extrusion occurring 2–28 months postoperatively. Retroprosthetic membranes occurred in three patients, and endophthalmitis in one. Vision improved from hand movements to 6/12 in the only patient who retained the KPro; however he was troubled by mucus accumulation on the optic. Conclusions: The one success has been in a patient with thermal burns. The remaining results have been poor, with the KPro extruding in six of the seven patients.

Descemet Stripping Automated Endothelial Keratoplasty After Failed Penetrating Keratoplasty: Survival, Rejection Risk, and Visual Outcome

IMPORTANCE Descemet stripping automated endothelial keratoplasty (DSAEK) for isolated endothelial dysfunction has become the preferred surgical option for many corneal surgeons. However, there are limited large-scale reports on DSAEK survival and clinical variables affecting the risk of rejection and failure after failed penetrating keratoplasty (PK). OBJECTIVE To report the survival, risk factors for graft rejection and failure, and visual outcome of DSAEK after failed PK. DESIGN, SETTING, AND PARTICIPANTS A multicenter retrospective interventional case series included patients recruited from 6 tertiary referral surgical centers: 3 in the United States, 2 in Europe, and 1 in Asia. A total of 246 consecutive eyes (246 patients) that underwent DSAEK after failed PK, with a minimum follow-up period of 1 month, was included. Data comprising demographic details, preoperative and postoperative risk factors, time to rejection, time to failure, and corrected distance visual acuity were collected. MAIN OUTCOMES AND MEASURES Cumulative probability of graft survival, hazard ratio estimates for survival, and corrected distance visual acuity were determined. RESULTS The mean (SD) recipient age was 63.2 (16.6) years and the median follow-up period was 17 months (interquartile range, 6-30 months). One-third of the grafts (n = 82) had follow-up data for more than 2 years; 18.3% had more than 1 failed PK before DSAEK. In total, 19.1% (47 of 246) of DSAEK grafts failed. The cumulative probability of DSAEK survival after a failed PK was 0.89 (95% CI, 0.84-0.92), 0.74 (95% CI, 0.64-0.81), and 0.47 (95% CI, 0.29-0.61) at 1 year, 3 years, and 5 years, respectively. Based on multivariate analysis, significant preoperative risk factors for failure were young recipient age (hazard ratio [HR], 5.18 [95% CI, 1.57-17.18]), previous tube filtration surgery (HR, 5.23 [95% CI, 1.47-7.33]), and rejection episodes before PK failure (HR, 3.28 [95% CI, 1.47-7.33]); single-surgeon centers had a protective effect. Any rejection episode prior to PK failure was a significant predictor of post-DSAEK rejection, which in turn was a significant predictor of DSAEK failure. After a median follow-up of 17 months, 33.3% of the grafts achieved 0.3 or greater logMAR (20/40) corrected distance visual acuity. CONCLUSIONS AND RELEVANCE Descemet stripping automated endothelial keratoplasty after failed PK combines greater wound stability and reduced suture-related complications, with visual outcomes and graft survival rates comparable to those of a second PK.

Closer to nature: new biomaterials and tissue engineering in ophthalmology

Ophthalmology has a long history of successful conventional biomaterial applications including viscoelastics, drug delivery vehicles, contact lenses, and a variety of implants. A myriad of further possibilities exists as the margins between conventional material concepts and natural tissues continue to blur, and biomaterials move closer to nature. Genetically engineered materials (for example, hyaluronic acid and fibrin tissue glues) harnessing the power and accuracy of biological systems in molecular synthesis are becoming commonplace. New synthetic surfaces capable of upregulating or downregulating biological responses at the tissue/material interface are starting to reach clinical application; and an emerging understanding of matrix/cell interactions may soon allow engineered replacement for a range of tissues in the eye. A basic classification divides materials according to their primary bonding structure into ceramics (ionic bonding), metals (metallic bonding), and polymers (covalent bonding). Modern ophthalmic implants are almost all fabricated from synthetic polymers. Polymeric materials are composed of long chain molecules (polymers) synthesised from repeat units (monomers) whose chemical character and reactivity determine many bulk properties. Most polymer chains have a covalently bonded backbone of carbon atoms joined to a variety of pendant groups. For siloxanes (“silicone”), an important group of synthetic biomaterials, this backbone consists of alternating atoms of silicone and oxygen. Molecular chains vary in length and are irregularly intertwined, although areas of regular arrangement (crystallinity) may exist. Cross linkage density and the density of secondary bonding further determine bulk properties for a given polymeric material.1 Secondary bonding mechanisms (for example, hydrogen bonds, van der Waals forces) are particularly relevant to biological systems, and are thought to have an important role in modulating protein conditioning—the process by which relatively inert polymeric material surfaces are rendered biologically active by contact with the tissues or body fluids.2 Protein conditioning is partly determined by surface reactivity, which varies …

Quality of Life in High Myopia before and after Implantable Collamer Lens Implantation

PURPOSE To examine changes in vision-related quality of life after implantable Collamer lens (ICL) implantation for the correction of myopia. DESIGN Prospective, interventional, consecutive case series. PARTICIPANTS We included 34 consecutive patients (68% female; mean age, 37 years [range, 23-49]) with preoperative myopia (mean ± standard deviation [SD] refraction spherical equivalent, -11.0 ± 3.12). INTERVENTION Bilateral ICL implantation. MAIN OUTCOME MEASURES Quality of life Impact of Refractive Correction (QIRC) score. RESULTS The median postoperative interval before questionnaire administration was 4 months (range, 3-7). The QIRC scores were significantly higher postoperatively (preoperative QIRC score [mean ± SD], 40.45 ± 4.83; postoperative QIRC score 53.79 ± 5.60; P < 0.001), with significant improvements (P<0.01) for 14 of 19 items. Nineteen (58%) patients reported a worsening in night vision symptoms (mostly nonspecific glare and halo or arc effects) after surgery, but overall levels of satisfaction were high; 88% were either satisfied or very satisfied with the results of surgery. No patients reported overall dissatisfaction. In free text responses, 11 patients (32%) described ICL implantation as life changing or wished that they had opted for the surgery sooner. CONCLUSIONS Implantation of an ICL for myopia is associated with significant improvements in quality of life. Any dissatisfaction with the procedure largely relates to night vision symptoms, which are common in the early postoperative period.

Quality of vision after bilateral multifocal intraocular lens implantation: a randomized trial--AT LISA 809M versus AcrySof ReSTOR SN6AD1.

PURPOSE To compare postoperative visual symptoms and spectacle freedom after bilateral implantation of the AT LISA 809M (Carl Zeiss Meditec, Jena, Germany) versus the AcrySof ReSTOR SN6AD1 (Alcon Laboratories, Irvine, CA) multifocal intraocular lens (IOL). DESIGN Double-masked, prospective, randomized, controlled clinical trial. PARTICIPANTS A total of 188 patients undergoing bilateral sequential cataract surgery or bilateral refractive lens exchange. METHODS Patients were preoperatively randomized (allocation ratio 1:1) to bilateral implantation with the AT LISA 809M IOL or ReSTOR SN6AD1 IOL. Postoperative outcomes were assessed 4 to 8 months after second eye surgery. MAIN OUTCOME MEASURES The primary outcome was visual symptoms evaluated with the Quality of Vision (QoV) questionnaire. Secondary outcomes included other questionnaire data (CatQuest-9SF, spectacle independence, vision satisfaction, and dysphotopsia) and visual function measures (near, intermediate, and distance visual acuity, binocular reading speed [International Reading Speed Texts], contrast sensitivity, and forward light scatter). Adverse events, including intraoperative and postoperative complications, also were evaluated. RESULTS There was no significant difference between IOL groups in Rasch-adjusted QoV scores for frequency (P = 0.95), severity (P = 0.56), and bothersomeness (P = 0.34) of visual symptoms; median (interquartile) scores for these QoV subscales were 29 (15-37), 22 (13-27), and 14 (0-29) for the AT LISA 809M IOL group, respectively, and 32 (15-37), 22 (13-30), and 14 (0-29) for the ReSTOR SN6AD1 IOL group, respectively. Halo was the most prominent dysphotopsia symptom, with 6% in both IOL groups reporting halo symptoms as very bothersome. Complete spectacle independence was achieved in 69 of 84 (82.1%) AT LISA 809M recipients and 66 of 85 (77.6%) ReSTOR SN6AD1 recipients (P = 0.57). Preferred reading distance was slightly nearer for the AT LISA 809M IOL. There were no statistically significant differences in any of the other secondary outcome measures. CONCLUSIONS Visual symptoms were similar after bilateral implantation of the AT LISA 809M and ReSTOR SN6AD1 IOLs. Both these diffractive bifocal IOLs produce high levels of spectacle independence and patient satisfaction. However, a small but clinically significant minority of patients remained symptomatic and dissatisfied with visual results 4 to 8 months after surgery.

Mechanism of iris prolapse: A qualitative analysis and implications for surgical technique

Abstract A theoretical explanation of the mechanism of iris prolapse is presented using simple flow mechanics and the Bernouille principle, which states that fluid pressure varies inversely to fluid velocity. Rapid aqueous escape into an anterior chamber perforation thus creates a relative vacuum anterior to the iris. Further analysis shows that the tendency of the iris to prolapse into an anterior chamber wound increases as an inverse function of the fourth power of the radial distance between the iris and the perforation. Anterior wound placement, clear of the iris plane, should help to prevent iris prolapse. Minimizing the irrigation velocity (and hence the fluid outflow velocity) should also help to prevent intraoperative prolapse.