Optisol vs Dexsol as storage media for preservation of human corneal epithelium

PURPOSE

To compare the efficacy of two storage media, Optisol GS and Dexsol, in preservation of donor corneal epithelium.

METHODS

A total of 12 pairs of corneas not suitable for transplantation, all with intact epithelium, were used in this study, with one cornea of the pair stored in Optisol GS and its other counterpart in Dexsol. At each of three durations of storage--1, 2, and 4 days--four of these paired corneas were prepared for light microscopy and scanning and transmission electron microscopy. Another four pairs of control cornea were prepared in the same way and placed in universal fixative.

MAIN OUTCOME MEASURES

Evaluation of the corneas was made by two observers masked as to the identity of the storage medium and length of storage. Loss of epithelial cells was evaluated by light microscopy. The attachment of the epithelium to the basement membrane,cellular integrity, intercellular junctions, and intracellular organelles were evaluated and compared by electron microscopy.

RESULTS

The magnitude of epithelial loss correlated with the length of storage time. Control corneas maintained normal epithelium with preservation of all epithelial cell layers. Corneas stored for 1 day had minimal damage of the epithelium. Corneas stored for 2 days had a slight increase in epithelial damage, and corneas stored for up to 4 days showed a marked increase in epithelial damage. There were no significant differences between the two storage media. The basal cell layer was maintained in both the media at all time points, usually in good condition with mild-to-moderate damage in some cases.

CONCLUSIONS

Loss of donor epithelium is related mainly to the length of storage and is similar in both Optisol GS and Dexsol. The storage time should be less than 4 days,especially when performing penetrating keratoplasty on patients with ocular surface disorders.

A molecular perspective on corneal dystrophies

Corneal dystrophies refer to a group of corneal diseases and that are genetically determined. These have been traditionally classified with respect to the layer of cornea involved. We now know that this does not reflect the underlying pathobiology. Most of the corneal dystrophies are of Mendelian inheritance with some phenotype diversity and a variable degree of penetrance. The dystrophies involving enzymatic processes tend to be of autosomal recessive inheritance. In some cases, such as keratoconus, the inheritance pattern is not always clear and is considered complex. The age of onset of the disease, as in most inherited eye disorders, is variable and does not reflect the underlying pathogenic defect. Few cases are congenital. Our understanding of corneal dystrophies is undergoing somewhat of a revolution as over 12 chromosomes have been associated with corneal dystrophies with mutations identified in at least 14 genes if one includes anterior segment dysgenesis in this group of conditions. Several dystrophies remain without a gene or a genetic location (locus) and more familial studies are required. The new molecular information is challenging the traditional thinking about these conditions that was usually guided by the histopathological findings. As this new knowledge becomes more refined, the classification of this group of disorders will eventually be revisited to have a molecular basis. The elucidation of the underlying biochemical pathways may allow us to envisage the possibility of modulating these phenotypes in the future.

Tyrosinemia type II: nine cases of ocular signs and symptoms

PURPOSE

To report nine cases of tyrosinemia type II, with ocular signs and symptoms.

METHODS

Participants included nine patients (18 eyes) who were followed for a mean follow-up period of 6.5 years (range, 2 to 8 years). Intervention included dietary restriction of tyrosine and phenylalanine, which led to resolution of ocular and cutaneous lesions, improved behavior in one patient, and may have prevented developmental delay in others. The main outcome measures were visual acuity and serum tyrosine levels to determine the response to dietary therapy. Intelligence testing and developmental screening were performed when appropriate.

RESULTS

All patients presented with ocular signs and symptoms as the primary manifestation of disease and serve to illustrate the typical ocular findings of this syndrome. Three patients presented with cutaneous manifestations, and one patient had mild mental impairment at the time of diagnosis.

CONCLUSIONS

Recalcitrant pseudodendritic keratitis may be the presenting sign in tyrosinemia type II. Awareness of the presenting signs and symptoms may accelerate the diagnosis and dietary intervention. Initiation of a tyrosine-restricted and phenylalanine-restricted diet in infancy is most effective in preventing cognitive impairment.

A semi-solid drug delivery system for epidermal growth factor in corneal epithelial wound healing

PURPOSE

To examine the effects of EGF, delivered from a semi-solid drug delivery system, on corneal epithelial wound healing following anterior keratectomy wound creation in the eyes of New Zealand white rabbits.

METHODS

A semi-solid drug delivery system based on a Carbopol gel was developed. Following creation of a 7.5 mm circular anterior keratectomy wound, 50 microL of either a placebo gel or an EGF-containing gel, was instilled in the inferior fornix. The gel remained in the eye for 8 hours, at which time it was removed. Anaesthesia was maintained for the entire 8-hour period. Wound healing was evaluated by quantitative morphometry. We evaluated 0.04, 0.1, 0.2, 0.4, and 1% EGF concentrations in the gel. Tear EGF concentrations and histology of the healing corneas were also examined.

RESULTS

The enhancement factor (ratio of the healing rate with the EGF gel and control gel) was 1.13 +/- 0.12, 1.40 +/- 0.14, 1.29 +/- 0.12, 1.80 +/- 0.22, and 1.09 +/- 0.12 for the gels containing 0.04, 0.1, 0.2, 0.4, and 1% EGF by mass, respectively. The increases in the rate of wound healing were significant with the 0.1, 0.2 and 0.4% gel formulations. Histologically, the 0.4% gels resulted in cellular hyperplasia after 5 days of healing. Differences between the placebo gel-treated and EGF-containing gel-treated eyes were evaluated at both 2 and 5 days. The concentration of EGF in the tears during the treatment period was approximately constant for both the 1% and 0.04% gels. The average tear concentration during the instillation period was 2.87 +/- 0.36 micrograms/mL and 200.61 ng/mL +/- 116.10 for the 1% and 0.04% gels respectively.

CONCLUSIONS

Treatment with EGF in a Carbopol gel carrier for a period of 8 hours results in significant wound healing enhancement (p < 0.05). The optimum EGF loading in the gel was determined to be 0.4%. A slow release gel may be an effective way to deliver EGF to the corneal surface.

Expression of p53 in conjunctival melanocytic nevi. An immunohistochemical study

The objective of this study was to evaluate conjunctival nevi for p53 gene mutations. We studied 11 conjunctival nevi by immunohistochemistry with the DO7 monoclonal p53 antibody as well as the cell proliferation marker, MIB1. Of the 11 cases, 2 were negative, 2 had less than 1%, and 7 had more than 2% p53 immunopositive nuclei with no direct correlation with MIB1 positivity. Our results suggest altered expression of p53 in conjunctival nevi.

A subconjunctival degradable implant for cyclosporine delivery in corneal transplant therapy

The effect of local cyclosporine therapy upon corneal transplant survival was investigated. A high risk rabbit model with vascularized corneas was used to assess the efficacy of subconjunctivally implanted degradable devices for cyclosporine therapy. Animals were divided into four groups, receiving either no therapy, a placebo PLGA device, or drug containing devices implanted either at the time of transplantation or two weeks previous. The mean survival times of animals in the control and placebo groups were statistically equivalent (21 +/- 4 days vs 18 +/- 4 days). Devices containing CsA improved the survival time of grafts. Predosing the animals with CsA improved the survival time to 28 +/- 7 days, and CsA devices implanted at the time of transplantation increased the survival time to 35 +/- 7 days. The improvement in survival times was consistent with the in vitro drug release profiles. No systemic CsA was detected, suggesting that the effect may have been local. Histological assessment indicated that devices were well tolerated.

Multi-organ donor transmission of hepatitis C virus to five solid organ transplant recipients and lack of transmission to corneal transplant recipients

BACKGROUND

A multi-organ donor seronegative for hepatitis C virus (HCV) by 1st generation enzyme immunoassay (EIA) supplied 5 solid organs and 2 corneas to 7 recipients. This donor was retrospectively shown to be 2nd generation HCV EIA-positive and polymerase chain reaction (PCR)-positive. All 5 solid organ recipients but none of the corneal recipients developed HCV infection.

OBJECTIVES

To demonstrate the discordance between serological and PCR-based HCV detection in solid organ transplant recipients and the lack of transmission of HCV to the two corneal transplant recipients.

STUDY DESIGN

All 5 solid organ recipients were retrospectively shown to be HCV PCR-negative and -seronegative pre-transplant and HCV PCR-positive post-transplant. Serial serum samples on 3 recipients were evaluated by 2nd generation EIA, a prototypic structural and non-structural dual bead assay (EIA-SA, Abbott), the Chiron Recombinant Immunoblot Assay, 2nd generation (RIBA-2), and the Chiron RIBA HCV Test System Strip Immunoblot Assay 3.0 (RIBA-3, Chiron).

RESULTS

The dual bead EIA-SA and RIBA-3 were able to detect HCV seroconversion approximately 6 months earlier than the 2nd generation EIA in 2 recipients, and in 1 recipient only PCR detected infection within the first 10 months. There was no evidence of HCV transmission to the corneal recipients.

CONCLUSIONS

Although third generation assays such as the RIBA-3 and EIA-SA narrowed the window of HCV seronegativity in transplant recipients compared with the 2nd generation EIA, PCR was the most sensitive method of detecting acute HCV infection. Despite transmission of HCV to all of the solid organ recipients HCV was not transmitted to the corneal transplant recipients.

Fifty:fifty poly (DL glycolic acid-lactic acid) copolymer as a drug delivery system for 5-fluorouracil: a histopathological evaluation

Fifty:fifty poly (DL glycolic acid-lactic acid) copolymer (PGLA) is a potentially useful depot drug delivery system for 5-fluorouracil (5-FU). The purpose of this study was to evaluate the fibroinflammatory reaction induced by this polymer. Polymer discs without 5-FU were inserted subconjunctivally in one eye of each of two guinea pigs and four pigmented rabbits (control group), and discs containing 20% 5-FU were inserted subconjunctivally in both eyes of nine pigmented rabbits (study group). The tissue reaction to the copolymer did not differ between rabbits and guinea pigs, with a mild mixed inflammatory reaction 1 week after implantation. At 2 weeks a thin fibrous capsule surrounded the discs, with no change in the amount of inflammation. At 4 weeks the disc had disintegrated, but residual polymer was seen within multinucleated giant cells in the episcleral tissue. Granulation tissue and inflammatory responses were mild. Less inflammation and fibrosis occurred in the study eyes, although the pattern of response was similar in the two groups. The inflammatory response to PGLA was markedly less than that to implanted collagen shields, and our findings suggest that PGLA implant is a promising ocular drug delivery system for 5-FU after filtration surgery.

Changing risk for early transplant failure: data from the Ontario Corneal Recipient Registry

To examine the joint effects of donor, recipient and surgical characteristics on the risk of early corneal transplant failure, 73 cases of early failure (no period of clarity or clarity lasting no more than 28 days) reported to the Ontario Corneal Recipient Registry were compared with 1591 control transplants remaining clear for 6 months or more. In logistic regression models donor age was significantly associated with graft failure, with the odds of failure increasing by 24% per decade. In recipients with a history of cataract or glaucoma or with an intraocular lens in place the relative odds of failure ranged from 2.16 to 3.08. Among surgical factors, larger grafts increased risk by 45% per 0.25 mm. Grafts received before 1987 had a consistently higher risk of early failure than those received in 1987 or later. Concurrent changes in storage media, handling of donor tissue and management of recipients may have been responsible. We conclude that donor, recipient and surgical factors all contribute to the risk of early transplant failure.

Determination of haptic position of transsclerally fixated posterior chamber intraocular lenses by ultrasound biomicroscopy

Transscleral fixation of posterior chamber intraocular lenses has become an increasingly popular procedure in eyes lacking adequate posterior capsular support. The assumption is generally made that these lenses are fixated in the ciliary sulcus. To test this assumption, 17 cases with transsclerally fixated posterior chamber intraocular lenses were examined with ultrasound biomicroscopy, a new method of producing subsurface images in living eyes at microscopic resolution. All lens haptics were easily visualized with this technique. Of 34 haptics in 17 patients, 13 were adequately located in the sulcus region, eight were located posterior to the ciliary processes, and 13 were located anterior to the sulcus region, accompanied by some degree of angle closure. Haptics with a more posterior scleral exit of the suture tended to be located more posteriorly. The cases in which the haptics were located anteriorly had scleral exit points from 1 mm to 2 mm from the limbus. The surgical placement of transsclerally fixated lenses is a blind procedure in most cases. Our series demonstrates the difficulty in reliably placing the haptics in the ciliary sulcus.