Aphakic refractive penetrating keratoplasty using newborn donor corneas. A preliminary report on an alternative approach to refractive correction

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Clinical outcomes after Descemet's stripping endothelial keratoplasty using donor corneas from children younger than 3 years

Importance

There is limited literature on paediatric donors in endothelial keratoplasty.

Background

This study investigated the efficacy of and appropriate paediatric donor age for Descemet’s stripping endothelial keratoplasty (DSEK).

Design

Retrospective and observational case series.

Participants

Thirty‐eight consecutive patients underwent DSEK with paediatric donor corneas.

Methods

The age of the donors ranged from 32 weeks gestation (premature neonate) to 3 years old. All donor consents were obtained from the parents. The causes of donor death included traffic accident, congenital heart disease and neonatal respiratory distress syndrome.

Main Outcome Measures

The outcome measures included best‐corrected visual acuity, endothelial cell loss and complications.

Results

Best‐corrected visual acuity at last follow‐up was >20/40 in 28 of 38 eyes (73.7%). The mean preoperative endothelial cell density of donor corneas was 4682 ± 520 cells/mm². The mean endothelial cell density of grafts was 3977 ± 556 cells/mm² at 18 months postoperatively. Three lenticules from premature neonate donors exhibited severe contraction postoperatively. The edge of six lenticules from donors <1‐year‐old exhibited contraction in the early postoperative period and gradually flattened spontaneously. Graft detachment occurred in one patient.

Conclusions and Relevance

DSEK with paediatric donor corneas can achieve good clinical outcomes. The corneal lenticules from 1‐ to 3‐year‐ old donors are suitable for DSEK while those from donors <1‐year‐old are less suitable due to the possibility of severe postoperative graft contraction.

Introduction to metabolomics and its applications in ophthalmology

Metabolomics is the study of endogenous and exogenous metabolites in biological systems, which aims to provide comparative semi-quantitative information about all metabolites in the system. Metabolomics is an emerging and potentially powerful tool in ophthalmology research. It is therefore important for health professionals and researchers involved in the speciality to understand the basic principles of metabolomics experiments. This article provides an overview of the experimental workflow and examples of its use in ophthalmology research from the study of disease metabolism and pathogenesis to identification of biomarkers.

The influence of donor age and cause of death on corneal endothelial cell density

PURPOSE

To evaluate the joint effects of donor age and cause of death on the endothelial cell density of fresh human corneas.

METHODS

The corneal endothelial cell density of 946 eyes from 946 donors was analysed. The donors were divided into three age groups: group 1 comprised those aged 50 years and less; group 2 those aged 51-75 years, and group 3 those aged over 75 years. They were also grouped according to the cause of death: group A included those who had died of cancer; group B those who had died of acute myocardial infarction, pulmonary embolism or intracerebral haemorrhage, and group C those who had died as a result of other diseases.

RESULTS

There was a statistically significant negative correlation between donor age and mean corneal endothelial cell density, which was 2868 +/- 309 cells/mm(2) in group 1, 2716 +/- 335 cells/mm(2) in group 2, and 2670 +/- 368 cells/mm(2) in group 3. Among the various causes of death, the mean endothelial cell density was 2677 +/- 343 cells/mm(2) in group A, 2741 +/- 367 cells/mm(2) in group B, and 2713 +/- 337 cells/mm(2) in group C. The endothelial cell density was significantly lower in group A than in group B (p = 0.02). When the donors in the oldest age group (group 3) were analysed according to the various causes of death, the difference between group A (2603 +/- 342 cells/mm(2)) and group B (2729 +/- 338 cells/mm(2)) was even more significant (p = 0.0067).

CONCLUSION

Longlasting, severe diseases like cancer, leading to cachexia and catabolism, reduce the number of endothelial cells to a greater degree than diseases that cause a more rapid death. This negative effect of cancer on endothelial cell density is aggravated by the general decline in endothelial cell density with advancing age.

The effects of donor age on the outcome of penetrating keratoplasty in adults

OBJECTIVE

The purpose of the study is to determine whether there is a higher incidence of complications in adult patients receiving corneas from pediatric donors compared to those receiving corneas from adult donors.

DESIGN

The design is a follow-up of two matched cohorts.

PARTICIPANTS

The outcome of penetrating keratoplasty in 29 adult patients (age 20 years of age and older) receiving pediatric donor corneas (range, 0-5 years) was compared to that of 29 control patients matched for recipient age and diagnosis who received adult donor corneas (range, 40-70 years).

INTERVENTION

Chart review was performed.

MAIN OUTCOME MEASURES

Graft rejection, postoperative keratometry, postoperative refractive cylinder, postoperative intraocular pressure, and graft failure due to rejection were measured.

RESULTS

One or more allograft reactions occurred in 11 (37.9%) of 29 patients who received pediatric donor corneas compared to 2 (6.9%) of 29 patients who received adult donor corneas (P = 0.005, chi-square). There were a total of 20 rejection episodes in patients receiving pediatric donor corneas compared to a total of 5 rejection episodes in patients receiving adult donor corneas. The average postoperative keratometry was 46.1 diopters for the pediatric donor group and 44.0 diopters for the adult donor group (P = 0.03). There was no statistically significant difference in average refractive cylinder (P = 1.0), intraocular pressure (P = 0.26), or the incidence of graft failure due to rejection (P = 1.0) between the two groups. The average follow-up time for clear grafts was 58.3 months in the pediatric donor group and 59.9 months in the adult donor group.

CONCLUSIONS

The incidence of allograft reactions and the postoperative corneal curvature is greater in adult eyes undergoing penetrating keratoplasty with young donor corneas compared to those undergoing penetrating keratoplasty with older donor corneas. There was no difference in the incidence of graft failure due to rejection between the two groups.

Factors associated with high postoperative myopia after penetrating keratoplasties in infants

Sixteen penetrating keratoplasties performed in patients younger than 2 years of age were reviewed to determine which factors were associated with high postoperative refractive errors. When tissue from donors younger than 2 years was used, the mean postoperative spherical equivalent was -13.7 diopters, compared with +2.0 diopters when tissue from donors older than 2 years was used (P = 0.001). Analysis of variance suggests that the use of a 0.5-mm oversized transplant, as opposed to a 0- to 0.3-mm oversized transplant, contributed to the production of high myopia when tissue from donors younger than 2 years was used (P = 0.009). The high myopia appears to have resulted from steep transplant curvatures. Based on these results, we recommend against the combined use of corneal transplant tissue from very young donors and 0.5-mm oversized transplants for infant penetrating keratoplasties.

Central and peripheral corneal thickness in newborns

Central and peripheral corneal thickness was measured in 74 newborn children. The mean central corneal thickness was 0.573 +/- 0.052 mm. The mean peripheral thickness was 0.650 +/- 0.062 mm. There was no significant difference between right and left eyes, sex, gestational age or type of delivery. The central and peripheral corneal thickness in the first 24 h of life was significantly higher than after 48 to 72 h. The full-term babies with 2.500 to 3.000 g of birth weight had peripheral corneal thickness higher than the group with 3.501 to 4.000 g.

Mastering the infant donor eye: a new device for obtaining corneoscleral buttons for storage and corneal discs for keratoplasty

The design and use of a new device for obtaining corneoscleral buttons for storage and corneal discs for keratoplasty from neonatal and adult donor eyes is described. The device is simple to use and eliminates most of the difficulties in handling infant donor eyes. It thus minimises the risk of damage to the corneal endothelium and the formation of stretch striae, which reduce the quality of the donor material for transplantation.

Manipulative damage to the endothelium of infant and adult donor corneas

Six human donor corneas were studied with the scanning electron microscope to quantify the hazards to the endothelium during the excision of corneoscleral buttons. Although the number studied was small, it was found that: (1) striae were more numerous in the flaccid, very young, donor corneas (under 1 year old) than in the more rigid adult corneas: (2) iridocorneal endothelial touch can result in loss of the posterior membrane and death of the touched endothelial cells. This corroborates the findings of other investigators. Both findings are important, because these conditions reduce the quality of the donor cornea for transplantation.

Effect of recipient-donor trephine size disparity on refractive error in keratoconus

A retrospective study was performed to evaluate the effect of recipient-donor trephine disparity on refractive error and corneal curvature post-suture removal in keratoconus. A double running suture technique was used and donor corneas were trephined from the endothelial side. When keratoconus patients with 0.25-mm larger donor than recipient trephines were compared with keratoconus patients with the same size recipient and donor trephines, a statistically significant increase in the mean keratometer value (45.4 and 43.8 diopters [D], respectively; P = 0.03) and increase in myopic spherical equivalent (-3.5 and -1.8 D, respectively; P = 0.03) was found. When keratoconus patients were compared with phakic Fuchs' dystrophy patients (both groups had 0.25-mm oversize donor trephines), the keratoconus group had a statistically significantly higher myopic spherical equivalent (-3.5 and -1.4 D, respectively; P = 0.03) despite only a 0.7-D difference in mean keratometer value which was not statistically significant (45.4 and 44.7 D, respectively). This study supports the hypothesis that the degree of post-penetrating keratoplasty myopia in patients with keratoconus can be decreased by reducing recipient-donor trephine disparity.

Corneal preservation

Significant advances in corneal preservation have been made over the past decade. The introduction of chondroitin sulfate-containing media for use at 4 degrees C allows storage of corneas for up to ten days prior to transplantation. Organ culture techniques have also been improved with the addition of chondroitin sulfate. There has been an increase in our understanding of preservation using McCarey-Kaufman medium. Studies have been published that compare these methods and help the clinician decide which method to use based on objective data. Also, our understanding of existing methods of evaluating endothelial viability has increased and new methods have been developed. Finally, the acquired immunodeficiency syndrome is having an increasing effect on eye-banking and the supply of donor corneas.

An in vitro model of leukocyte mediated injury to the corneal epithelium

To enhance efforts directed at unraveling the role and mechanisms of leukocytes in mediating injury to corneal epithelium, an isolated bovine corneal cup was developed and evaluated. Bovine peripheral leukocytes and lysates were added to the corneal epithelial surface of isolated cornea for various periods after which the degree of morphologic changes and cell damage were assessed using light and electron microscopy. Results of these studies indicate that leukocyte/epithelial cell interactions are characterized by five successive stages: (1) leukocyte adhesion to superficial layer of the epithelium, (2) leukocyte penetration beneath the superficial epithelium, (3) epithelial cell injury, (4) leukocyte phagocytosis of killed epithelial cells and (5) ulceration and total destruction of the full thickness of the epithelial layer. The above sequence appears to be both time and dose dependent; that is epithelial cells exposed to leukocytes for short periods (5-60 minutes) or to low dose levels (10(5) - 10(7) cells/ml) shows leukocyte adhesion and penetration beneath the superficial layer of the epithelium, (stage 1 and 2), while longer exposures (2-3 hours) or higher numbers of leukocytes (10(7) - 10(8) cells/ml), leads to deeper penetration of epithelium by leukocytes and epithelial injury (Stages 3,4,and 5). We also observed that direct contact of intact leukocytes with epithelial cells is apparently necessary to induce this type of injury. These findings demonstrate the ability of leukocytes to destroy corneal epithelial cells and the value of this new ocular model for studies of the basic immunology of ocular inflammation.