Confocal Microscopy of Posterior Polymorphous Endothelial Dystrophy

In vivo confocal microscopic observations of eyes diagnosed with posterior corneal vesicles

PURPOSE

To determine the morphological characteristics of the cornea in eyes with posterior corneal vesicles (PCV) determined by in vivo confocal microscopy (IVCM). In addition, to compare the morphological characteristics of the corneas of eyes with PCV to those of eyes with posterior polymorphous corneal dystrophy (PPCD).

METHODS

Three males and three females aged 17-75 years who were diagnosed with PCV by slit-lamp biomicroscopic findings were studied. The slit-lamp findings, specular microscopic images, corneal endothelial cell densities (CDs), central corneal thickness, and IVCM images were evaluated. Three cases that had been diagnosed with PPCD were also evaluated, and the findings were compared to those in eyes with PCV.

RESULTS

All six cases of PCV had unilateral lesions of Descemet's membrane and the corneal endothelium. Slit-lamp biomicroscopy showed broad, band-shaped lesions in five cases and multiple vesicle lesions in one case of PCV. The IVCM images of the six cases had a common appearance of the corneal endothelial cells in the affected areas showing iso-reflective nuclei and low reflective cell membranes as seen in normal corneal endothelial cells. The CDs in the affected eyes were about one-half of those of the not affected eyes. The IVCM images of the corneas of patients with PPCD showed polymorphic cells with hyperreflective nuclei, which are characteristics of epithelial cells.

CONCLUSIONS

The IVCM images demonstrated that the corneal endothelial cells of patients with PCV have normal morphology. These findings indicate that PCV is a distinct clinical entity different from PPCD.

In vivo confocal microscopic findings in posterior polymorphous corneal dystrophy

PURPOSE

To describe the corneal findings in posterior polymorphous corneal dystrophy (PPCD) as imaged with laser scanning in vivo confocal microscopy (IVCM).

METHODS

IVCM images of 7 subjects with PPCD who had typical slit-lamp biomicroscopic findings of endothelial vesicular, band, and/or placoid lesions were evaluated.

RESULTS

Five women and 2 men aged 7 to 64 years were included in this study. Laser scanning IVCM (Heidelberg Retina Tomograph II, Rostock Cornea Module) revealed hyporeflective, round, vesicular lesions with diameters ranging between 20 and 200 µm in 3 subjects, combined vesicular and curvilinear hyperreflective band-like lesions in 3 subjects, and combined vesicular and placoid hyperreflective lesions in 1 subject at the level of Descemet membrane (DM), endothelial cell layer, and posterior stroma adjacent to DM. One subject had coassociated epithelial basement membrane dystrophy. Additional findings included posterior stromal keratocytes with elongated spindle-like nucleus, giant and nucleated endothelial cells, endothelial deposits, and guttae-like dark spots. The mean endothelial cell density was 1485.7 ± 486.3 cells per square millimeter (range, 990-2365 cells/mm). The mean central corneal thickness was 585.3 ± 37.17 μm (range, 534-643 μm).

CONCLUSIONS

Laser scanning IVCM is able to highlight the characteristic microstructural alterations at the level of endothelium and DM in the setting of PPCD and may have diagnostic utility in equivocal cases with borderline biomicroscopic findings. The possible association of PPCD with epithelial basement membrane dystrophy warrants further investigation.

Molecular bases of corneal endothelial dystrophies

The phrase "corneal endothelial dystrophies" embraces a group of bilateral corneal conditions that are characterized by a non-inflammatory and progressive degradation of corneal endothelium. Corneal endothelial cells exhibit a high pump site density and, along with barrier function, are responsible for maintaining the cornea in its natural state of relative dehydration. Gradual loss of endothelial cells leads to an insufficient water outflow, resulting in corneal edema and loss of vision. Since the pathologic mechanisms remain largely unknown, the only current treatment option is surgical transplantation when vision is severely impaired. In the past decade, important steps have been taken to understand how endothelial degeneration progresses on the molecular level. Studies of affected multigenerational families and sporadic cases identified genes and chromosomal loci, and revealed either Mendelian or complex disorder inheritance patterns. Mutations have been detected in genes that carry important structural, metabolic, cytoprotective, and regulatory functions in corneal endothelium. In addition to genetic predisposition, environmental factors like oxidative stress were found to be involved in the pathogenesis of endotheliopathies. This review summarizes and crosslinks the recent progress on deciphering the molecular bases of corneal endothelial dystrophies.

Photorefractive keratectomy in posterior polymorphous dystrophy with vesicular and band subtypes

PURPOSE

To evaluate the safety and efficacy of photorefractive keratectomy (PRK) in patients with posterior polymorphous dystrophy (PPMD) with vesicular and band subtypes.

SETTING

Walter Reed Center for Refractive Surgery, Washington, DC, USA.

DESIGN

Case series.

METHODS

The records of patients with PPMD who had PRK between January 2002 and May 2009 were reviewed. Data for analysis included sex, age, ablation depth, residual stromal bed thickness, manifest spherical equivalent, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, central corneal thickness (CCT), endothelial cell density (ECD), intraocular pressure (IOP), and complications. Preoperative and postoperative results were compared using the Wilcoxon signed-rank test, with P < .05 considered significant.

RESULTS

Fourteen eyes of 7 men (mean age 29.1 years ± 9.1 [SD]; range 21 to 42 years) with at least a 6-month follow-up were reviewed. At the final follow-up (mean 19.5 months; range 6.3 to 58.3 months), all eyes had a UDVA of 20/15 and all eyes were within ± 0.50 diopter of emmetropia. The CDVA was unchanged from preoperatively in 71.4% of eyes and improved by 1 line in 28.6%. There were no significant complications. The IOP did not change significantly over the follow-up (P = .272). At the final visit, the mean ECD (2795.3 ± 366.0 cells/mm(2)) was unchanged from baseline (2809.1 ± 338.3 cells/mm(2)) (P = .114).

CONCLUSIONS

Photorefractive keratectomy in PPMD patients with vesicular and band subtypes resulted in excellent visual outcomes and a low incidence of adverse effects. Endothelial cell densities did not change significantly in the early postoperative period.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Observation of posterior corneal vesicles with in vivo confocal microscopy and anterior segment OCT

The histopathology of posterior corneal vesicles (PCV) has not yet been revealed. A 15-year-old girl, who was diagnosed by slit-lamp microscopy as PCV, was examined using specular microscopy, in vivo confocal microscopy, and anterior segment OCT (optical coherence tomography). Anterior segment OCT showed that the thickness of both corneas was within normal limits. At the same time, in vivo confocal microscopy revealed endothelial cells in the rounded dark areas, acellular hyporeflective layers on the Descemet’s membrane, and hyperreflective linear lesions. These findings were not reported previously by slit-lamp and specular microscopy. The abnormal findings only existed at the Descemet’s membrane and corneal endothelial layer. Previous reports dealing with posterior polymorphous dystrophy (PPMD) examined using in vivo confocal microscopy reported almost the same findings, suggesting that PCV and PPMD may be the same at the microstructural level.

Comparative in vivo confocal microscopical study of the cornea anatomy of different laboratory animals

PURPOSE

The aim of the present study was to analyze and compare in vivo morphology of healthy cornea of six different laboratory animals.

MATERIALS AND METHODS

One Pomeranian Coarsewool sheep, 5 Beagle dogs, 1 Norwegian and 2 Domestic Short-haired cats, 20 New Zealand White rabbits, 6 Wistar rats, and 10 Balb/c mice were included. The examination was performed bilaterally, using Heidelberg Retina Tomograph equipped with Rostock Cornea Module. The morphology of living corneal layers was visualized and compared between species. The central corneal thickness, density of keratocytes, and endothelial cells were quantified.

RESULTS

The epithelial multilayer showed a similarity in morphology between animal types, displaying three clearly distinguishable layers: superficial, intermediate, and basal. Subbasal nerve fibers were displayed as hyperreflective structures underneath basal cells. The subbasal fibers were confirmed in all species, however, the density varied between species. A pronounced Bowman's membrane was visualized in sheep. In all other species, however, a thin acellular layer with overlying nerve fibers could be seen between basal epithelial cells and anterior stroma. The keratocytes nuclei could be demonstrated in all species except for mice, where no nuclei but only reflective structures resembling keratocytes cell bodies were detected. Overall, the density of keratocytes nuclei was significantly higher in the anterior than in the posterior stroma. Besides endothelial cells density, the endothelial cells morphology was very similar among all species, except for sheep. The endothelial cells were displayed as polygonal structures with bright cytoplasm and dark borders. In sheep, the appearance of the endothelium was very poor because of a thick hyperreflective Descemet's membrane.

CONCLUSIONS

The present study will help researchers consider appropriate models for animal experiments, depending on focus of investigation. In vivo CLSM can be used for the characterization of the living cornea over time, thus, reducing the number of animal experiments.

The clinical spectrum between posterior polymorphous dystrophy and iridocorneal endothelial syndromes

BACKGROUND

There are many conditions affecting the corneal endothelium with similar clinical appearances, though with different prognoses, management approaches, and pathophysiologic development.

CASE

A 39-year-old black woman with a previous diagnosis of asymmetric corneal posterior polymorphous dystrophy (PPMD) presented complaining of irritation in the left eye, worsening over the last week. On examination, her left eye had profuse edema and bullous keratopathy overlying a large placoid gray lesion at the level of the endothelium. Gonioscopy of the left eye found evidence of a membranous development extending from the endothelium to the trabecular meshwork. Examination of her right eye found a perfectly clear cornea and a normal angle. The patient subsequently had Chandler's syndrome diagnosed in the left eye, an iridocorneal endothelial (ICE) syndrome, rather than PPMD.

DISCUSSION

PPMD and ICE syndromes present with many similarities; these clinical entities are in fact thought to be variants of the same disease. Unlike PPMD, Chandler's syndrome is unilateral, acquired, and typically symptomatic and progressive. It also characteristically affects middle-age women.

CONCLUSION

Understanding the clinical features of PPMD and ICE syndromes is important in proper diagnosis and management.

Novel corneal phenotype in a patient with alport syndrome

PURPOSE

To report the clinical and histopathologic findings of an unusual keratopathy, which may represent a new corneal dystrophy in a patient with Alport syndrome (ATS).

METHODS

A 59-year-old woman with longstanding diagnosis of autosomal recessive ATS was evaluated for progressively decreasing vision in the left eye. She had anterior lenticonus and cataract and central corneal stromal opacification with significant thinning and flattening bilaterally. She underwent penetrating keratoplasty and cataract extraction with posterior chamber intraocular lens implantation. We describe the light microscopic and ultrastructural findings from the cornea.

RESULTS

Histopathology of the corneal button revealed marked stromal thinning with decreased keratocytes. The endothelial cells were attenuated and focally lost. Immunohistochemical stains for cytokeratin were positive, findings consistent with posterior polymorphous dystrophy (PPMD). Transmission electron microscopy showed necrosis and a marked loss of keratocytes. Multilayering of the endothelium was consistent with PPMD, but mature desmosomes and microvilli were absent. In vivo confocal microscopy on the fellow eye showed linear hyporeflective bands at the level of Descemet's membrane consistent with PPMD. In addition, there were fine linear changes in the deep stroma and diffuse hyperreflectivity of the mid and superficial stroma with lack of identifiable keratocytes throughout.

CONCLUSIONS

We believe this to be the first reported case to demonstrate some histopathologic features of PPMD in ATS. However, the clinical, histopathologic, and ultrastructural characteristics are not typical of PPMD. This may represent a new phenotypic expression of PPMD or may be a distinct clinicopathologic dystrophy associated with ATS.

Optical coherence tomography and in vivo confocal microscopy features of obstetric injury of the cornea

We present a case of a 54-year-old man who reported to our department complaining of worsening vision and halos in the left eye. Slit-lamp biomicroscopy showed 2 distinctive oblique vertical lines situated on the posterior surface of the cornea. Anterior segment optical coherence tomography (AS-OCT) demonstrated bandlike structures protruding from the cornea into the anterior chamber for approximately 430 and 100 microm. In vivo confocal microscopy (IVCM) revealed stromal edema, low endothelial density, and prominent hyperreflective linear structures at the endothelium depth and behind the endothelium. The patient had a history of complicated, in-hospital, forceps-assisted delivery. The perinatal ophthalmic history was noncontributory. The fellow eye was healthy. We conclude that AS-OCT and IVCM are useful in confirming the clinical diagnosis of suspected perinatal corneal trauma because of the specific appearance of the Descemet membrane hypertrophic ridge in those examinations. There is a good correlation between the results of AS-OCT and IVCM.

In vivo confocal microscopy in different types of posterior polymorphous dystrophy

Posterior polymorphous dystrophy is a rare corneal dystrophy, usually detected by chance. This case series describes the morphologic features in the three different types of posterior polymorphous dystrophy using confocal microscopy.

Contemporary in vivo confocal microscopy of the living human cornea using white light and laser scanning techniques: a major review

In vivo confocal imaging of the cornea has evolved exponentially over the last few decades and it has increasingly emerged from the laboratory to be used in the clinical setting in relation to inherited corneal diseases, corneal infections, contact lens wear and the effects of corneal surgery. This evolution has led to significant enhancement of our knowledge of the living cornea in both its physiological and pathological states. A number of in vivo confocal microscope devices using white, and more recently coherent, light sources have been developed to provide non-invasive assessment of the corneal microstructure at a lateral resolution of 1-2 microm. The fundamental principles of in vivo confocal microscopy and the key differences between these devices are highlighted in this review. By providing a systematic review of the extensive literature on the human cornea, this perspective paper aims to provide an overview of how in vivo confocal microscopy has contributed to our greater understanding of the human cornea in health, in disease, and following surgery, with a particular emphasis on quantitative data. The utility and limitations of available data are highlighted as are possibilities for the future development of this innovative technology.

Clinical corneal confocal microscopy

Confocal microscopy allows non-invasive in vivo imaging of the ocular surface. Its unique physical properties enable microscopic examination of all layers of the cornea and have been used to investigate numerous corneal diseases: epithelial changes, numerous stromal degenerative or dystrophic diseases, endothelial pathologies, corneal deposits, infections, and traumatic lesions. It offers a new approach to study the physiological reactions of the cornea to different stimuli and the pathophysiologic events leading to corneal dysfunction in certain diseases. Confocal microscopy proves to be a powerful diagnostic tool and is especially of value in certain corneal diseases by allowing straightforward and non-invasive recognition of the pathologic conditions.