Binocular vision recovery in bilateral keratoplasty

Corneal Transplantation in Disease Affecting Only One Eye: Does It Make a Difference to Habitual Binocular Viewing?

BACKGROUND

Clarity of the transplanted tissue and restoration of visual acuity are the two primary metrics for evaluating the success of corneal transplantation. Participation of the transplanted eye in habitual binocular viewing is seldom evaluated post-operatively. In unilateral corneal disease, the transplanted eye may remain functionally inactive during binocular viewing due to its suboptimal visual acuity and poor image quality, vis-à-vis the healthy fellow eye.

METHODS AND FINDINGS

This study prospectively quantified the contribution of the transplanted eye towards habitual binocular viewing in 25 cases with unilateral transplants [40 yrs (IQR: 32-42 yrs) and 25 age-matched controls [30 yrs (25-37 yrs)]. Binocular functions including visual field extent, high-contrast logMAR acuity, suppression threshold and stereoacuity were assessed using standard psychophysical paradigms. Optical quality of all eyes was determined from wavefront aberrometry measurements. Binocular visual field expanded by a median 21% (IQR: 18-29%) compared to the monocular field of cases and controls (p = 0.63). Binocular logMAR acuity [0.0 (0.0-0.0)] almost always followed the fellow eye's acuity [0.00 (0.00 --0.02)] (r = 0.82), independent of the transplanted eye's acuity [0.34 (0.2-0.5)] (r = 0.04). Suppression threshold and stereoacuity were poorer in cases [30.1% (13.5-44.3%); 620.8 arc sec (370.3-988.2 arc sec)] than in controls [79% (63.5-100%); 16.3 arc sec (10.6-25.5 arc sec)] (p<0.001). Higher-order wavefront aberrations of the transplanted eye [0.34 μ (0.21-0.51 μ)] were higher than the fellow eye [0.07 μ (0.05-0.11 μ)] (p<0.001) and their reduction with RGP contact lenses [0.09 μ (0.08-0.12 μ)] significantly improved the suppression threshold [65% (50-72%)] and stereoacuity [56.6 arc sec (47.7-181.6 arc sec)] (p<0.001).

CONCLUSIONS

In unilateral corneal disease, the transplanted eye does participate in gross binocular viewing but offers limited support to fine levels of binocularity. Improvement in the transplanted eye's optics enhances its participation in binocular viewing. Current metrics of this treatment success can expand to include measures of binocularity to assess the functional benefit of the transplantation process in unilateral corneal disease.

Quality of life in keratoconus patients after penetrating keratoplasty

PURPOSE

To determine vision-related quality of life (QoL) measured with the National Eye Institute Visual Function Questionnaire (NEI-VFQ) in keratoconus (KCN) patients who have undergone penetrating keratoplasty (PK) in 1 or both eyes and to compare the results of our study to those of historical controls.

DESIGN

Clinical-based, cross-sectional study.

METHODS

SETTING

Wills Eye Institute, Cornea Service, Thomas Jefferson University, Philadelphia, Pennsylvania.

STUDY POPULATION

This study included 149 consecutive patients who had undergone PK for KCN.

INTERVENTION

Between June 1, 2008 and December 31, 2008, the NEI-VFQ was administered to 149 patients. The relationship between demographic and clinical factors and NEI-VFQ subscale scores was evaluated.

MAIN OUTCOME MEASURE

Vision-related quality of life.

RESULTS

Eighty-three of 149 patients (55.7%) were male. Approximately half of the patients (76/149; 51.0%) had PK in both eyes. Visual acuity with current correction in the better eye was better than 20/40 in 80% of patients (119/149). Our sample had significantly lower (worse) NEI-VFQ scores compared to Collaborative Longitudinal Evaluation of Keratoconus (CLEK) historical control group for the subscales of role difficulties, dependency, driving, and peripheral vision. In general, scores of our sample were between scores of patients with age-related macular degeneration (AMD) category 3 and 4. Patients with visual acuity better than 20/40 (in the better eye) showed significantly higher scores in all subscales except color vision. There was a significant relationship between minimum time since the graft of 5 years or greater and NEI-VFQ overall score better than AMD category 3 (P = .004).

CONCLUSION

Despite satisfactory results on visual outcome measures obtained after PK, vision-related QoL in KCN patients remains impaired.

Reading the small print - labelling recommendations for orthopaedic implants

INTRODUCTION

There exist, currently, no clear guidelines regarding standards for surgical implant labelling. Dimensions of the laminar flow canopies in orthopaedic use fixes the distance at which implant labels can be read. Mistakes when reading the label on an implant box can pose health risks for patients, and financial consequences for medical institutions.

SUBJECTS AND METHODS

Using scientifically validated tools such as the Snellen Chart Formula, a theoretical minimum standard for text on implant labels was reached. This theoretical standard was then tested under real operating conditions. After discovering a minimum practical standard for implant labels, the authors then audited current labels in use on a wide range of orthopaedic implant packages. Furthermore, other non-text-related labelling problems were also noted.

RESULTS

There is a definite minimum standard which should be observed when implant labels are manufactured. Implants in current use bear labels on the packaging that are of an insufficient standard to ensure patient safety in theatre.

CONCLUSIONS

The authors have established text parameters that will increase the legibility of implant labels. In the interests of improving risk management in theatre, therefore, the authors propose a standard for orthopaedic implant labelling, and believe this will provide a useful foundation for further discussion between the orthopaedic community and implant manufacturers.

Current concepts and techniques in corneal transplantation

The corneal endothelium is the most important single layer in corneal transplantation. In his Castroviejo Lecture, William Bourne, MD, summarizes his work on the corneal endothelium and its importance to corneal transplantation. Almost half the corneal transplants performed in the United States are done so because of malfunctioning, diseased, or absent endothelial cells. If just this layer could be transplanted, the long wait for better vision after keratoplasty (up to two years in some countries) can be eliminated, as well as the problems of epithelial and subepithelial graft rejection. The significant astigmatism after keratoplasty could also be reduced. Transplantation of the endothelium in deep lamellar keratoplasty is being done in limited fashion throughout the world and the first patients have now been done in the United States. In many countries where corneal tissue is difficult to obtain, keratoplasty is only performed on one eye, even though both eyes may need it. One article this year discusses binocular vision recovery in bilateral keratoplasty and the objective and subjective improvements after bilateral keratoplasty. Patients who are bilaterally blind from diseases such as Stevens-Johnson syndrome, and ocular pemphigoid have little hope of visual recovery from conventional corneal transplants. The use of a keratoprosthesis to bypass the totally abnormal conjunctival surface has helped many people in the past. The preoperative prognostic categories of patients who may benefit from keratoprosthesis has been carefully reviewed in a large number of keratoprosthesis patients and this information will help ophthalmologists decide who will benefit the most benefit from keratoprosthesis. This year, articles on corneal transplantation after conjunctival flaps, suture-related complications in keratoplasty, the implantation of an intraocular lens after penetrating keratoplasty, and long-term results of penetrating keratoplasty with glaucoma drainage tube implants are subjects that warrant in depth discussion and evaluation. Finally, eye bank considerations will be discussed concerning the long-term question of transmission of cancer through corneal transplantation.