Recurrent Meesmann's corneal epithelial dystrophy after penetrating keratoplasty

PURPOSE

To characterize the histopathology of recurrent Meesmann's corneal epithelial dystrophy after penetrating keratoplasty.

METHODS

Postmortem examination by light and electron microscopy of the eyes of an 84-year-old patient with Meesmann's dystrophy who underwent a penetrating keratoplasty in the right eye at age 74 years and a lamellar keratoplasty in the left eye at age 51 years.

RESULTS

In the right eye, the characteristic features of Meesmann's dystrophy were demonstrated in both the donor and recipient corneas. The pathologic findings were limited to the corneal epithelium and included increased thickness, architectural disorganization, loss of cell polarity, increased amounts of intracellular glycogen, presence of intraepithelial microcysts containing degenerated cells, and in some cells, the presence of an electron-dense fibrillogranular material associated with disrupted cytoplasmic filaments. In the left eye, the corneal findings were consistent with but not specific for Meesmann's dystrophy. These included architectural disorganization, loss of cell polarity, presence of intraepithelial microcysts, and irregular thickening of the basement membrane in the donor cornea.

CONCLUSION

Meesmann's corneal epithelial dystrophy is demonstrated to recur after penetrating keratoplasty. This finding suggests that the abnormalities that lead to the disease are localized to the corneal epithelial cells and not in the stroma, as previously proposed.

Spontaneous corneal perforation in pellucid marginal degeneration

PURPOSE

We present a report of a spontaneous corneal perforation in a patient with pellucid marginal corneal degeneration.

METHODS

We describe the presentation and management of a 74 year old male with spontaneous corneal perforation related to pellucid marginal corneal degeneration.

RESULTS

The corneal perforation was repaired with a 3 mm penetrating patch graft. The cornea has remained stable for 7 years with no further progression of corneal ectasia in either eye.

CONCLUSIONS

Although rare, spontaneous corneal perforations in patients with pellucid marginal corneal degeneration can occur, and patients should be cautioned about this possibility.

Histopathology of recurrent gelatinous drop-like corneal dystrophy

PURPOSE

To elucidate more fully the histopathology of gelatinous drop-like corneal dystrophy in a case that recurred and was operated on 7 years after the original surgery.

METHODS

Transmission electron microscopy, including the use of cuprolinic blue to image sulfated proteoglycans, and horseradish peroxidase as a marker for in vitro epithelial permeability.

RESULTS

Our patient's epithelium was often abnormally thick, and many intercellular spaces were present at all levels, although cell-cell contact via desmosomes was also evident. Horseradish peroxidase, when used as an in vitro tracer, was able to penetrate the most superficial tight junctions of the corneal epithelium. Basal epithelial cells were not columnar, and numerous spike-like projections protruded into the underlying amyloid/collagenous tissue from the basal epithelium. Beneath this, duplication of a discontinuous epithelial basement membrane was noted. In this region, collagen often coexisted with amyloid, the deposition of which was extensive. As in some other corneal pathologies, long-spacing collagen was detected. The association of small proteoglycans with collagen was unremarkable, although some abnormally large, sulfated proteoglycan filaments were interspersed with the amyloid and underlying stroma.

CONCLUSION

Recurrent gelatinous drop-like corneal dystrophy shares several histopathologic features with its primary counterpart, although some features, such as the presence of abnormally large, sulfated proteoglycans and long-spacing collagen, the permeability of the epithelial tight junctions, and the duplication of the epithelial basement membrane, have not been reported previously.

Alport syndrome. A review of the ocular manifestations

Alport syndrome has a prevalence of 1/5000, and 85% of patients have the X-linked form, where affected males develop renal failure and usually have a high-tone sensorineural deafness by the age of 20. The typical ocular associations are a dot-and-fleck retinopathy which occurs in about 85% of affected adult males, anterior lenticonus which occurs in about 25%, and the rare posterior polymorphous corneal dystrophy. The retinopathy and anterior lenticonus are not usually demonstrated in childhood but worsen with time so that the retinal lesion is often present at the onset of renal failure, and the anterior lenticonus, later. The demonstration of a dot-and-fleck retinopathy in any individual with a family history of Alport syndrome or with end-stage renal disease is diagnostic of Alport syndrome. The presence of anterior lenticonus or posterior polymorphous corneal dystrophy in any individual is highly suggestive of the diagnosis of Alport syndrome. Additional ocular features described in X-linked Alport syndrome include other corneal dystrophies, microcornea, arcus, iris atrophy, cataracts, spontaneous lens rupture, spherophakia, posterior lenticonus, a poor macular reflex, fluorescein angiogram hyperfluorescence, electrooculogram and electroretinogram abnormalities, and retinal pigmentation. All mutations demonstrated to date in X-linked Alport syndrome have affected the COL4A5 gene which encodes the alpha 5 chain of type IV collagen. This protein is probably common to the basement membranes of the glomerulus, cochlea, retina, lens capsule, and cornea. However, the alpha 3(IV) and 4(IV) as well as the alpha 5(IV) collagen chains are usually absent from the affected basement membranes, because the abnormal alpha 5(IV) molecule interferes with the stability of all three. The loss of these collagen molecules from the affected basement membranes results in an abnormal ultrastructural appearance. The ocular and other clinical features of autosomal recessive Alport syndrome are identical to those seen in X-linked disease, while retinopathy and cataracts are the only ocular abnormalities described in the rare autosomal dominant form of Alport syndrome. There are no ocular associations of thin basement membrane disease which is a common disease that probably represents the heterozygous expression of X-linked or autosomal recessive Alport syndrome.

Corneal dystrophies and keratoconus

This year's reports have given us a better understanding of several dystrophies as well as improvements in diagnosis and treatment. Eight corneal dystrophies have now been mapped to specific chromosomes and of these lattice, granular, Avellino, and Reis Bückler's dystrophies map to the same region of chromosome 5q, raising the question whether they are the result of mutations in separate genes or of mutations within alleles of a single gene. Phototherapeutic keratoplasty appears to offer an advantage in the initial treatment of several dystrophies whose symptoms arise from superficial corneal change. Some success has been reported in reducing the degree of hyperopic shift that accompanies deeper ablations. Further support for the genetic basis of keratoconus comes from a study in monozygotic twins and from improvements in quantitative videokeratographic indices, which have also improved our ability to distinguish keratoconus from other topographic abnormalities of the cornea. A new hypothesis for the mechanism of keratoconus proposes that an increased expression of interleukin-1 receptors, acting through a paracrine pathway, may disturb keratocyte activity and turnover, leading to a loss of stromal mass.

Characteristic distribution of deposits in recurrent granular corneal dystrophy

Granular corneal dystrophy can recur after penetrating keratoplasty. In those cases as in the early primary manifestation of the disease, deposits are found predominantly in the superficial corneal layers. At a later stage, stromal deposits can also be seen. We describe an additional particular location of deposits and correlate clinical with histological findings in three corneas from two patients. Deposits were found mainly superficially within the graft and around the edge of the transplant along the scar between host and donor cornea. We suggest that the deposits are of epithelial origin, though their production by stromal cells cannot be excluded. Chemical interactions are discussed as an explanation for the characteristic distribution of the deposits.

The Castroviejo square graft

The histopathologic features of three keratoplasty specimens from three cases involving square graft procedures performed by Dr. Castroviejo are reported. Light and electron microscopy were performed. In two of the cases, repeat keratoplasties were performed because of recurrent corneal dystrophies. In the third case, a repeat keratoplasty was performed because of graft failure.

Corneal dystrophies and keratoconus

Knowledge about keratoconus (KC) and the corneal dystrophies continues to advance at a steady pace in view of the wide interest in these topics to basic scientists and clinical ophthalmologists. As in the past the articles on KC outnumber those on all of the other corneal dystrophies combined. Major advances have been made mainly regarding several specific corneal dystrophies, but KC remains a perplexing disorder with many unanswered questions. As we learn more and more about the corneal dystrophies from genetic linkage analyses and molecular biological techniques it will eventually be possible to understand the fundamental defect that causes these conditions.

Immunohistochemical analysis of the pathogenesis of posterior polymorphous dystrophy

The pathogenesis of posterior polymorphous dystrophy was analyzed by immunohistologic methods. Sections of corneal buttons from two patients undergoing transplantation owing to posterior polymorphous dystrophy were stained with 2B4.14.1, a monoclonal antibody that reacts with human corneal endothelium, and with a cocktail of antihuman cytokeratin monoclonal antibodies that do not react with normal corneal endothelium. Single-stained sections revealed a variegated, intermittent staining pattern of antibody reactive and nonreactive cells. Double-stained sections revealed some cells that stained with only one of the antibodies and many cells that stained with both antibodies. The presence of cells staining positively for both 2B4.14.1 antigen and cytokeratins supports the hypothesis that the cytokeratin-expressing epithelial-like cells found in corneas with posterior polymorphous dystrophy arise via a metaplastic process in which the phenotype of endothelial cells becomes progressively abnormal.

Multirecurrence of corneal posterior polymorphous dystrophy. An ultrastructural study

Posterior polymorphous corneal dystrophy (PPD) is a rare bilateral, autosomal-dominant disease. The presence of the epitheliumlike endothelium and the thickening of Descemet's membrane by the posterior collagenous layer (PCL) has been reported in the majority of published cases. Reepithelialization of the posterior cornea in donor tissue has been reported only once. Therefore, to examine this process we examined, by light and electron microscopy, three corneal buttons (an original and two subsequent keratoplasties after 3 and 4 years, respectively) from the left eye of a patient with bilateral disease. Our study showed a repopulation of the posterior surface of the donor corneas by the host epitheliumlike endothelium, which was of identical morphology in each case. In contrast to the previously published work, a posterior collagenous layer in the failed grafts was absent from the axial cornea, where the epitheliumlike endothelium was in direct contact with donor Descemet's membrane. A PCL at the periphery in the failed transplants was of the fibrocellular type and differed from the fibrillar PCL in the first keratoplasty specimen. The fibroblastlike cells within the fibrocellular PCL were distinct from the underlying epithelial-like cells and contained numerous tertiary phagolysosomes. We suggest that the major contributor to the fibrocellular PCL in the repeat keratoplasties was a fibrous ingrowth from the host/graft junction and not the epitheliumlike endothelium. It appears that the synthetic capacity of the epitheliumlike endothelium was similar to that of the normal epithelium and was much lower than that of normal native endothelium.

Bilateral progressive essential iris atrophy and keratoconus with coincident features of posterior polymorphous dystrophy: a case report and proposed pathogenesis

We report the first case known to us of an apparent bilateral association of essential iris atrophy (EIA) and keratoconus (KC), with coincident features of posterior polymorphous dystrophy (PPD). Based on this case and the published natural history and findings of both the irido corneal endothelial (ICE) syndrome and PPD, we propose a new hypothesis for the pathogenesis of the ICE syndrome with associated KC and/or PPD. We suggest that, similar to the genetics of retinoblastoma, the predisposition for either the ICE syndrome or for PPD is inherited as an inactive allele, the so-called "first hit." Inactivation of the second allele, or "second hit," which could occur at any time, might be the product of the background mutation rate or of an environmental trigger. Dedifferentiation or an abnormality in normal development could occur after the first or second hit, resulting in varying clinical patterns. We also concur with other investigators that PPD could be part of the spectrum of the ICE syndrome, owing to similarities in their clinical presentations, histopathology, specular and electron microscopy, and natural history.

[Corneal dystrophies]

Corneal dystrophies are rare and have multiple clinical expressions. Some of them are isolated, without any systemic background, and often familial; they evolve slowly with opacification or deformation of the corneal stroma or with recurrent erosions; treatment consists of corneal grafting which generally has a favourable outcome. Other corneal dystrophies are manifestations of a systemic metabolic disorder; they are often associated with other ocular lesions and their prognosis is rather poor.

Differentiation of corneal complications observed in contact lens wearers

Corneal epithelial cystic formations and epithelial infiltrates are relatively common in contact lens patients. Accurate diagnosis of these conditions is needed for proper management of the patient, but the observation and differential diagnosis is hampered by the minute size and similar biomicroscopic appearance of these conditions. This paper presents a description of these subtle formations and the slit lamp techniques for differentiating epithelial microcysts, vacuoles, bullae, and infiltrates. The clinical significance of these conditions is also discussed.

Contact lens-induced pseudo-dystrophy of the cornea?

Whitish dots in the stroma of the cornea resembling the cloudy dystrophy were observed in 4 patients wearing HEMA contact lenses; a lattice-like corneal pattern was seen in another patient wearing HEMA contact lenses. There were no complaints. Visual acuity was normal. Corneal sensitivity was normal or reduced. The pseudo-dystrophies vanished after replacement of the HEMA lenses by Boston IV material.

New contact lens challenges: the epithelial basement membrane dystrophy

This paper examines a "new frontier" in contact lens fitting. It integrates histopathological and slit lamp findings of the epithelial basement membrane dystrophies and relates them to various options in therapeutic and cosmetic contact lens treatment. It reviews new concepts regarding the incidence and etiology of the dystrophy. The risk benefit assessment of extended wear hydrogels and rigid gas permeable lens fitting is discussed. Case histories illustrate clinical successes.

The association between pinguecula, sunlight and cataract

The pathology and epidemiology of pinguecula suggest that it is due to exposure to sunlight. There is some epidemiological and laboratory evidence that sunlight is an etiological factor in cataract so that it would be expected that the two conditions--pinguecula and cataract--would occur together more frequently than by chance. In a series of patients requiring cataract extraction pinguecula did not occur more frequently than in sex- and and aged-matched controls. Although there was a correlation between an outdoor working environment and the incidence of pinguecula there was no such correlation with cataract. It is concluded that direct exposure of the eye to sunlight did not seem to be a factor in the development of age-related cataract in this population.

Polymorphic corneal abnormalities

Alterations of the deep corneal layers, which are manifest primarily as Hassall-Henle bodies in older patients, are a relatively frequent finding in the normal population. Changes which occur in Descemet's membrane and the endothelium earlier in life can be ascribed to various causes, including dystrophy, herpetic infections, and birth trauma. Six cases in which clear vesicles and scalloped lesions were found exclusively at the level of Descemet's membrane and the endothelium are reported. Although the polymorphic changes were in some cases extensive, visual acuity and, apparently, corneal physiology remained normal. The etiology for all cases was uncertain, but the evidence suggested a dystrophic origin or the occurrence of posterior corneal vesicles of a nonfamilial variety.