Long-term contact lens wear induces a corneal degeneration with microdot deposits in the corneal stroma

Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy

PURPOSE

During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM.

METHODS

31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.

RESULTS

The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia.

CONCLUSIONS

Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

In vivo confocal microscopy evaluation of infiltrated immune cells in corneal stroma treated with cell therapy in advanced keratoconus

PURPOSE

This study investigates immune cell (ICs) infiltration in advanced keratoconus patients undergoing autologous adipose-derived adult stem cell (ADASC) therapy with recellularized human donor corneal laminas (CL).

METHODS

A prospective clinical trial included fourteen patients divided into three groups: G-1, ADASCs; G-2, decellularized CL (dCL); and G-3, dCL recellularized with ADASCs (ADASCs-rCL). Infiltrated ICs were assessed using in vivo confocal microscopy (IVCM) at 1,3,6, and12 months post-transplant.

RESULTS

Infiltrated ICs, encompassing granulocytes and agranulocytes, were observed across all groups, categorized by luminosity, structure, and area. Stromal ICs infiltration ranged from 1.19% to 6.62%, with a consistent increase in group-related cell density (F = 10.68, P < .0001), independent of post-op time (F = 0.77, P = 0.511); the most substantial variations were observed in G-3 at 6 and 12 months (2.0 and 1.87-fold, respectively). Similarly, significant size increases were more group-dependent (F = 5.76, P < .005) rather than time-dependent (F = 2.84, P < .05); G-3 exhibited significant increases at 6 and 12 months (3.70-fold and 2.52-fold, respectively). A lamina-induced shift in IC size occurred (F = 110.23, P < .0001), primarily with 50-100 μm2 sizes and up to larger cells > 300μm2, presumably macrophages, notably in G-3, indicating a potential role in tissue repair and remodeling, explaining reductions in cells remnants < 50μm2.

CONCLUSIONS

ADASCs-rCL therapy may lead to increased IC infiltration compared to ADASCs alone, impacting cell distribution and size due to the presence of the lamina. The findings reveal intricate immune patterns shaped by the corneal microenvironment and highlight the importance of understanding immune responses for the development of future therapeutic strategies.

Advanced Anterior Eye Segment Imaging for Ichthyosis

The purpose of this study was to describe ocular surface and anterior eye segment findings in various types of ichthyoses.

METHODS

This was a single-center prospective observational study. The study group consisted of five patients (P1-P5) aged 13-66 years. Multimodal imaging was performed, including slit-lamp examinations, swept-source optical coherence tomography (SS-OCT), and in vivo confocal microscopy (IVCM).

RESULTS

All patients were diagnosed with moderate-to-severe dry eye disease (DED). The corneas showed a significant pattern of irregularity, with a significant difference between the corneal thickness at the apex (CAT) and the corneal thinnest thickness (CTT), exceeding 375 µm. Three patients were diagnosed with ectasia patterns based on SS-OCT. All patients showed abnormalities in at least one Fourier index parameter for at least one eye at 3 or 6 mm in the keratometric, anterior, or posterior analyses. IVCM examinations revealed changes in all corneal layers.

CONCLUSIONS

By combining the results of multimodal imaging, we were able to detect preclinical abnormalities, distinguish characteristic changes common to ichthyosis, and reveal the depth and characteristics of corneal abnormalities. Therefore, patients with ichthyosis should be examined for DED and ectatic disorders early in clinical practice.

Effect of the Presence of Silicone Oil in the Anterior Chamber After Complicated Retinal Detachment Surgery on Corneal Morphology by In Vivo Confocal Microscopy

PURPOSE

This study evaluated the corneal endothelium, stromal keratocytes, subbasal nerve number and density in patients with silicone oil transferred to the anterior camera after pseudophakic complicated retinal detachment surgery by in vivo laser scanning confocal microscopy (IVLSCM).

METHODS

Sequential measurements were made by IVLSCM between 3-6 months after surgery in two groups of patients: a) with silicon oil migration (Group 1) and without silicone oil migration (Group 2).

RESULTS

A total of 63 cases (Group 1: 32 and Group 2: 31) were examined. The mean ages of patients were 65 ± 12 and 61 ± 11 and M/F ratio was 18/14 and 17/14, respectively. Mean intraocular pressures were 16.60 ± 4.60 and 15.75 ± 5.70 mm Hg, respectively. Changes were detected by IVLSCM mostly on the superior part of the cornea. A significant decrease in endothelial cell density and the number was detected in group 1 (2072 ± 116.2 cells/mm2 vs 2752 ± 512.3 cells/mm2; p < 0.001). Significant increases in posterior keratocyte density and stromal hyperreflective deposits were observed in group 1 (887 ± 45.8 cells/mm2 vs 725 ± 65.8 cells/mm2; p < 0.001). A significant negative correlation was observed between the size of stromal deposits and endothelial cell density (r=-0.758; p < 0.001). The number and density of corneal subbasal nerves were significantly lower in group 1 (1.8 ± 0.8 and 4.8 ± 1.2 vs 420 ± 101 and 701 ± 112 µm/square; p < 0.001).

CONCLUSION

IVLSCM is a useful tool for the early detection of corneal abnormalities caused by silicone oil injection. This study verified silicone oil's detrimental effect on the corneal endothelium and revealed stromal changes in the anterior chamber, which we believe can be also been associated with the presence of silicone oil.

Long-term effect of contact lens wear: A citation network study

BACKGROUND

Contact lenses can cause complications in 2/3 of the total population, but in most cases, they are mild and easy to manage. However, most of the studies are short-term. The aim of the study was to analyze the publications on the long-term effects of contact lens wear to understand the current research landscape through the analysis of dating networks as well as determining the different research areas and the most cited publications.

METHODS

The Web of Science database was used to perform the publication search, looking for the terms "Long-term" AND "contact lens wear" within the period between 1977 and January 2021. The CitNetExplorer and CiteSpace software were then used to conduct the publication analysis. To obtain the graphics, the VOSviewer software was used.

RESULTS

A total of 721 publications were found with 2999 citations generated within the network. The year 2010 was singled out as a "key year", considering the number of publications that emerged in that year and increase in adaptations of contact lens worldwide. The most widely cited publication was "Effects of long-term extended contact lens wear on the human cornea", an article by Holden et al., which was published in 1985. By using the clustering function, we were able to establish three clusters that encompassed the different research areas within this field: morphological changes, the loss of corneal sensitivity, tear film characteristics and longitudinal changes in ocular physiology.

CONCLUSIONS

The main research topic in this field focuses on the morphological changes that take place in the corneal endothelial cell layer.

Structural Changes in Thin Keratoconic Corneas Following Crosslinking with Hypotonic Riboflavin: Findings on In Vivo Confocal Microscopy

Purpose

To report structural changes observable in in vivo confocal microscopy (IVCM) in keratoconic corneas < 400 μm treated with hypotonic riboflavin and collagen crosslinking (CXL).

Methods

Ten eyes of ten patients with progressive keratoconus and corneal thickness between 350 and 399 μm underwent CXL with hypotonic riboflavin. IVCM was performed preoperatively and at one month, three months, and six months after the procedure.

Results

IVCM analysis one month postoperatively showed complete absence of the subepithelial nerve plexus with gradual regeneration over six months in 8 of the 10 eyes, and poor regeneration in the remaining 2 eyes. The anterior stroma showed extracellular lacunae and hyper-reflective cytoplasm in a honeycomb appearance signifying edema at one month which gradually decreased over six months post CXL. Stromal keratocyte apoptosis was evident in the anterior stroma in all cases and extended to the posterior stroma in four eyes with gradual regeneration evident at three and six months. The specular endothelial count decreased by 8% (P = 0.005) post-CXL, but no corneas developed clinical signs of endothelial trauma.

Conclusion

IVCM analysis of thin corneas after hypotonic CXL showed posterior corneal structural changes. Posterior stromal changes were accompanied by a decrease in the endothelial cell count. This case series was a preliminary feasibility study that might necessitate conducting a well-designed controlled study.

Microdot Accumulation in the Anterior Cornea with Aging - Quantitative Analysis with in Vivo Confocal Microscopy

PURPOSE

Degenerative 'microdot' deposits in healthy and hypoxic corneas are believed to represent lipofuscin-like material aggregation in the stroma. To accurately assess microdot deposits in a clinical setting, we sought to quantify these deposits for the first time using the non-invasive clinical imaging technique of in vivo confocal microscopy (IVCM).

METHODS

The corneas of 102 healthy subjects aged 15-88 years were examined by IVCM and microdot density was quantified using a 6-point grading scale by two masked, trained examiners. Microdot density was analyzed with respect to age, sex and stromal depth, and inter-eye and inter-observer differences were evaluated.

RESULTS

In healthy subjects, microdot density decreased from the anterior to posterior stroma, with the greatest accumulation observed in the most anterior stroma (subepithelial region). In this region, microdot density correlated strongly with age (P < .0001), with increased microdot deposition in older subjects (>60 years) relative to younger ones (<45 years) (P < .001). Microdot density between eyes of the same subject was highly correlated (r = 0.92, P < .0001), while no association with sex was noted (P ≥ 0.05). The mean inter-observer difference in microdot assessment was 0.62 ± 0.09 grades, with a high correlation of grading between observers (r = 0.77, P < .0001).

CONCLUSIONS

IVCM can be used to non-invasively quantify microdot deposits in the subepithelial corneal stroma with good inter-observer reproducibility. Microdot assessment may provide a novel means of quantifying age-related or pathologic degeneration of the corneal stroma in a clinical setting.

Cornea and anterior eye assessment with slit lamp biomicroscopy, specular microscopy, confocal microscopy, and ultrasound biomicroscopy

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple, and several devices and technologies show signs that help in identification of different diseases thereby, helping in diagnosis, management, and follow-up of patients. The purpose of this review is to present and update readers on the evaluation of cornea and ocular surface. This first part reviews a description of slit lamp biomicroscopy (SLB), endothelial specular microscopy, confocal microscopy, and ultrasound biomicroscopy examination techniques and the second part describes the corneal topography and tomography, providing up-to-date information on the clinical recommendations of these techniques in eye care practice. Although the SLB is a traditional technique, it is of paramount importance in clinical diagnosis and compulsory when an eye test is conducted in primary or specialist eye care practice. Different techniques allow the early diagnosis of many diseases, especially when clinical signs have not yet become apparent and visible with SLB. These techniques also allow for patient follow-up in several clinical conditions or diseases, facilitating clinical decisions and improving knowledge regarding the corneal anatomy.

In vivo confocal microscopy of toxic keratopathy

Purpose

To explore the morphological characteristics of toxic keratopathy (TK), which clinically presented as superficial punctate keratopathy (SPK), with the application of in vivo laser-scanning confocal microscopy (LSCM), and evaluate its potential in the early diagnosis of TK.

Patients and methods

This was a cross-sectional study involving 16 patients with TK and 16 patients with dry eye (DE), demonstrating SPK under slit-lamp observation, and 10 normal eyes were enrolled in the study. All participants underwent history interviews, fluorescein staining, tear film break-up time (BUT) tests, Schirmer tests, and in vivo LSCM.

Results

The area grading of corneal fluorescein punctate staining was higher in the TK group than the DE group. Measured by in vivo LSCM, superficial epithelial cell density was lower in the TK group than that of DE group. The sub-basal nerve presented lower density and tortuosity in the TK group than the DE group. Most notably, deposits with a snow-like appearance were observed in the epithelium in 12/16 (75.0%) of the TK cases, but none in the DE group (P<0.05).

Conclusion

The SPK in TK patients was characterized by more widespread punctate staining, a lower density of superficial epithelial cells and sub-basal nerves, and a typical snow-like pattern of deposits in the epithelium by LSCM. These features might facilitate early diagnosis of TK from other disorders manifested as SPK.

In vivo confocal microscopy of the ocular surface: from bench to bedside

In vivo confocal microscopy (IVCM) is an emerging technology that provides minimally invasive, high resolution, steady-state assessment of the ocular surface at the cellular level. Several challenges still remain but, at present, IVCM may be considered a promising technique for clinical diagnosis and management. This mini-review summarizes some key findings in IVCM of the ocular surface, focusing on recent and promising attempts to move "from bench to bedside". IVCM allows prompt diagnosis, disease course follow-up, and management of potentially blinding atypical forms of infectious processes, such as acanthamoeba and fungal keratitis. This technology has improved our knowledge of corneal alterations and some of the processes that affect the visual outcome after lamellar keratoplasty and excimer keratorefractive surgery. In dry eye disease, IVCM has provided new information on the whole-ocular surface morphofunctional unit. It has also improved understanding of pathophysiologic mechanisms and helped in the assessment of prognosis and treatment. IVCM is particularly useful in the study of corneal nerves, enabling description of the morphology, density, and disease- or surgically induced alterations of nerves, particularly the subbasal nerve plexus. In glaucoma, IVCM constitutes an important aid to evaluate filtering blebs, to better understand the conjunctival wound healing process, and to assess corneal changes induced by topical antiglaucoma medications and their preservatives. IVCM has significantly enhanced our understanding of the ocular response to contact lens wear. It has provided new perspectives at a cellular level on a wide range of contact lens complications, revealing findings that were not previously possible to image in the living human eye. The final section of this mini-review provides a focus on advances in confocal microscopy imaging. These include 2D wide-field mapping, 3D reconstruction of the cornea and automated image analysis.

A Case of Bilateral Descemet's Membrane and Subepithelial Opacity: In vivo Laser Confocal Microscopic Study

Purpose

To report the in vivo laser confocal microscopy findings from a patient with Descemet's membrane and subepithelial opacity OU.

Case Report

A healthy 41-year-old male with Descemet's membrane and subepithelial opacity OU was studied. Routine ophthalmic examination, standard slit-lamp biomicroscopy, and in vivo laser confocal microscopic analysis of the entire corneal layer were performed. Slit-lamp biomicroscopy revealed subepithelial opacity in the mid-peripheral to peripheral cornea and numerous opacities located at the level of Descemet's membrane. It was difficult to distinguish the precise histological location of the opacity. In vivo laser confocal microscopy showed numerous hyperreflective particles in the subepithelium to superficial stroma and hyperreflectivity of Descemet's membrane. No abnormalities could be detected in the epithelial cell layer, midstromal layer, deep stromal layer, or endothelial cell layer.

Conclusion

Although the origin of the corneal opacities was unclear, in vivo laser confocal microscopy was useful for observing microstructural abnormalities in a case of Descemet's membrane and subepithelial opacity.

In vivo confocal microscopic evaluation of corneal wound healing after femtosecond laser-assisted keratoplasty

BACKGROUND AND OBJECTIVE

To evaluate corneal wound healing after femtosecond laser-assisted keratoplasty (FLAK) using in vivo confocal microscopy (IVCM).

PATIENTS AND METHODS

Prospective, interventional, consecutive case series of 17 eyes after mushroom-shaped FLAK. IVCM was performed preoperatively and at 1, 3, 6, and 12 months postoperatively to assess wound healing.

RESULTS

Mean keratocyte activation grade increased from preoperative levels to 1 month postoperatively in both the central (0.41 ± 0.62 to 1.73 ± 1.03) and peripheral (0.47 ± 0.52 to 1.57 ± 1.09) cornea, then gradually decreased through 12 months. Dendritic cells increased from preoperatively to 1 month postoperatively in both the central (0.71 ± 0.83 to 1.33 ± 0.98) and peripheral (0.79 ± 0.70 to 1.42 ± 0.90) cornea, then gradually decreased until 6 months postoperatively. Stromal reinnervation was 1 month postoperatively in 8 patients (50%). By 12 months, sub-epithelial nerves were observed centrally in 5 patients (45.5%).

CONCLUSION

IVCM after FLAK shows an initial increase in keratocyte activation and dendritic cells that decrease over time. Corneal reinnervation is seen as early as 1 month postoperatively.

In vivo confocal microscopy: corneal changes of hydrogel contact lens wearers

To evaluate the corneal findings in hydrogel contact lens wearers by in vivo confocal scanning microscopy. One hundred and forty-two eyes of 71 myopic contact lens wearers (group 1) and 142 eyes of 71 non-contact lens wearers (group 2), whose age, gender and refractive error matched, were enrolled in order to detect the corneal changes by in vivo confocal microscopy through the central cornea. The average age was 25.5 ± 5.7 (16-52) and 25.6 ± 5.6 (17-49) in groups 1 and 2, respectively. The mean duration of contact lens wear was 43.9 ± 15.3 (6-240) months. Anterior keratocyte density was 667.5 ± 128.3 cells/mm(2) in group 1 and 821.4 ± 136.7 cells/mm(2) in group 2 (P = 0.001). Posterior keratocyte densities of groups 1 and 2 were 540.2 ± 87.6 cells/mm(2) and 628.2 ± 72.4 cells/mm(2), respectively (P < 0.001). Endothelial cellular density was 2611.2 ± 298.4 cells/mm(2) in group 1 and 2643 ± 218.2 cells/mm(2) in group 2 (P = 0.52). Ratio of polymegethism was 44.6 ± 8.8% in group 1 and 31.3 ± 4.7% in group 2 (P < 0.001). Epithelial cellular enlargement was observed in eyes wearing contact lenses with a mean Dk/t ratio of 26.5 × 10(-9) ± 5.9 (8.9-32 × 10(-9)). Stromal microdots occurred with contact lenses with a mean Dk/t ratio of 13.2 × 10(-9) ± 17.5 × 10(-9) (8.9-20 × 10(-9)). In vivo examination of the cornea with confocal microscopy revealed a number of changes. These changes can be attributed both to the mechanical and the hypoxic effects of soft contact lenses. In soft contact lenses with a high Dk/t ratio, these changes would be less frequent.

Corneal innervation in mesocephalic and brachycephalic dogs and cats: assessment using in vivo confocal microscopy

OBJECTIVE

To determine the density of the canine and feline corneal neural network in healthy dogs and cats using in vivo confocal microscopy (IVCM). ANIMALS EXAMINED: A total of 16 adult dogs (9 Mesocephalic breeds, 7 Brachycephalic breeds) and 15 cats (9 Domestic Short-haired cats (DSH), 6 Persian cats) underwent IVCM.

PROCEDURE

Animals were examined with a confocal corneal microscope (HRTII/RCM; Heidelberg Retina Tomograph II/Rostock Cornea Module, Heidelberg Engineering, Dossenheim, Germany). The investigations focused on the distribution of the corneal nerves and quantification of central subepithelial and subbasal nerve plexus.

RESULTS

The corneal stromal nerve trunks, subepithelial and subbasal nerve plexus were observed. The nerve fiber density (NFD) quantified in nerve fiber length in mesocephalic dogs were 12.39 +/- 5.25 mm/mm(2) in the subepithelial nerve plexus and 14.87 +/- 3.08 mm/mm(2) in the subbasal nerve plexus. The NFD of the subepithelial nerve plexus in DSH cats was 15.49 +/- 2.7 and 18.4 +/- 3.84 mm/mm(2) in the subbasal nerve plexus. The subbasal NFD of DSH cats was significantly higher than in mesocephalic dogs (P = 0.037). The subepithelial NFD in brachycephalic dogs, and Persian cats were 10.34 +/- 4.71 and 9.50 +/- 2.3 mm/mm(2), respectively. The subbasal NFD measured 11.80 +/- 3.73 mm/mm(2) in brachycephalic dogs, and 12.28 +/- 4.3 mm/mm(2) NFD in Persian cats, respectively. The subepithelial and subbasal NFD in Persian cats were significantly lower than in DSH cats (P = 0.028, respectively, P = 0.031), in contrast to brachycephalic vs. mesocephalic dogs.

CONCLUSION

The noninvasive IVCM accurately detects corneal innervation and provides a reliable quantification of central corneal nerves.

Clinical applications of corneal confocal microscopy

Corneal confocal microscopy is a novel clinical technique for the study of corneal cellular structure. It provides images which are comparable to in-vitro histochemical techniques delineating corneal epithelium, Bowman's layer, stroma, Descemet's membrane and the corneal endothelium. Because, corneal confocal microscopy is a non invasive technique for in vivo imaging of the living cornea it has huge clinical potential to investigate numerous corneal diseases. Thus far it has been used in the detection and management of pathologic and infectious conditions, corneal dystrophies and ecstasies, monitoring contact lens induced corneal changes and for pre and post surgical evaluation (PRK, LASIK and LASEK, flap evaluations and Radial Keratotomy), and penetrating keratoplasty. Most recently it has been used as a surrogate for peripheral nerve damage in a variety of peripheral neuropathies and may have potential in acting as a surrogate marker for endothelial abnormalities.

Laser Scanning In Vivo Confocal Analysis of Keratocyte Density in Keratoconus

PURPOSE

Keratoconus is a form of progressive noninflammatory corneal ectasia. Although abnormalities have been documented at every level of the keratoconic cornea, the exact underlying pathophysiologic process remains unknown. This study aimed to determine the keratocyte density in human corneas with keratoconus imaged by laser scanning in vivo confocal microscopy.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Thirty-six eyes of 26 subjects with keratoconus compared with 33 eyes of 33 control subjects.

METHODS

Subjects were assessed via ophthalmic examination, computed topography, and laser scanning in vivo confocal microscopy.

MAIN OUTCOME MEASURES

Anterior and posterior stromal keratocyte density.

RESULTS

Mean age was 34.7+/-12.1 years in the control group, 38.4+/-11.0 years in the keratoconic with no contact lens wear group, and 38.5+/-10.3 years in the keratoconic with contact lens wear group. No significant difference was noted in age or gender between the groups. Mean keratocyte density in the control group was 786+/-244 cells/mm(2) in the anterior stroma and 293+/-35 cells/mm(2) in the posterior stroma. Anterior keratocyte density was higher than posterior keratocyte density (P<0.001). Anterior keratocyte density was significantly lower in contact lens-wearing keratoconic subjects in comparison with controls (463 vs. 786 cells/mm(2); P<0.001). Posterior keratocyte density was significantly lower in keratoconic subjects with no contact lens wear (236 vs. 293 cells/mm(2); P<0.001) and in keratoconic subjects with contact lens wear (208 vs. 293 cells/mm(2); P<0.001). In subjects with keratoconus, anterior keratocyte density correlated with central corneal thickness (r = 0.426, P = 0.012) and inversely with steepest keratometry values (r = -0.383, P = 0.028).

CONCLUSIONS

Keratocyte density is significantly lower in subjects with keratoconus, and the decline in keratocyte density correlates with indices of disease severity. In vivo confocal microscopy offers the opportunity to study early microstructural changes in the keratoconic cornea.

Confocal microscopy imaging of the cornea in patients with silicone oil in the anterior chamber after vitreoretinal surgery

OBJECTIVE

Evaluation of corneal morphology by confocal microscopy after vitreoretinal surgery complicated by passage of silicone oil into the anterior chamber. Design Case series (case control study).

METHODS

Eight patients (eight eyes) who had undergone vitreoretinal surgery and had silicone oil in the anterior chamber but no clinically evident corneal abnormalities made up the patient group. The control group consisted of eight patients (eight eyes) who had undergone vitreoretinal surgery with application of silicone oil tamponade but who had no silicone oil clinically observable in the anterior chamber. In vivo examination of the cornea using a ConfoScan 3 (Nidek Technologies) confocal microscope equipped with the standard 40x immersion lens was performed. Central, upper, and lower parts of the cornea were assessed separately. High-magnification evaluation of the status of corneal layers and endothelial cell density in upper parts of the cornea directly in contact with silicone oil in the anterior chamber and in parts of the cornea not in direct contact with silicone oil was carried out.

RESULTS

Alterations in corneal morphology, especially in endothelium and posterior and medium stroma, were observed. In all cases, changes were more advanced in the upper part of the cornea. Endothelial cell density was significantly decreased in upper parts of the cornea.

CONCLUSIONS

In patients with silicone oil in the anterior chamber, confocal microscopy imaging reveals early morphological alterations of the cornea before their clinical manifestation.

Contact lens-induced changes in the anterior eye as observed in vivo with the confocal microscope

The availability of the confocal microscope over the past decade has allowed clinicians and researchers to refine their understanding of the physiological and pathological basis of the ocular response to contact lens wear, and to discover previously unknown phenomena. Mucin balls, which form in the tear layer in patients wearing silicone hydrogel lenses, can penetrate the full thickness of the epithelium, leading to activation of keratocytes in the underlying anterior stroma. Epithelial cell size increases in response to all forms of lens wear, with lenses of higher oxygen transmissibility (Dk/t) interfering least with the normal process of epithelial desquamation. A higher density of Langerhans' cells is observed in the layer of the sub-basal nerve plexus among contact lens wearers, suggesting that contact lens wear may be altering the immune status of the cornea. Dark lines and folds are observed in the oedematous cornea in response to contact lens wear. Mechanical stimulation of the corneal surface, due to the physical presence of a contact lens, and the consequent release of inflammatory mediators, is the likely cause of reduced keratocyte density associated with lens wear. Highly reflective stromal 'microdot deposits' are observed throughout the entire stroma in higher numbers in lens wearers. 'Blebs' in the endothelium have a bright centre surrounded by a dark annular shadow; this appearance is explained with the aid of an optical model. The confocal microscope has considerable clinical utility in diagnosing Acanthamoeba and fungal keratitis. At the limbus, contact lenses can induce structural changes such as increases in basal epithelial cell size. An increased number of rolling leucocytes is observed in limbal vessels in response to low Dk/t lenses. It is concluded that the confocal microscope has considerable utility in contact lens research and practice.

In vivo confocal microscopy in the normal corneas of cats, dogs and birds

OBJECTIVE

To evaluate the applicability of in vivo confocal microscopy (IVCM) in veterinary ophthalmology and analyze the morphology of living, healthy cornea. ANIMALS EXAMINED: Thirty-seven dogs, 34 cats and five birds.

PROCEDURE

Various corneal sublayers were visualized in the central region using an in vivo confocal corneal microscope (HRTII/RCM).

RESULTS

An investigation method was developed and adapted for use on animals with varying skull forms and eye positions. Real-time images of the epithelial cells, the corneal stroma and the endothelial layer were obtained. The corneal stromal nerve trunks and the subepithelial and basal epithelial nerve plexus were visualized. In dogs, full corneal thickness (FCT) was 585 +/- 79 microm (mean +/- SD) and endothelial cell density (ECD) 3175 +/- 776 cells/mm(2) (mean +/- SD). In cats, FCT was 592 +/- 80 microm and ECD 2846 +/- 403 cells/mm(2). There were no significant differences between canine and feline FCT and ECD and no morphologic differences could be seen between dogs and cats. The bird images revealed a number of structural differences.

CONCLUSION

Noninvasive IVCM allows accurate detection of corneal sublayers, corneal pachymetry, endothelial cell density and corneal innervation in various animal species. For clinical usage, patients must be under general anesthesia. The confocal images provided anatomic reference images of various healthy corneal structures in dogs, cats and birds.

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.

Study of the factors associated with the presence of white dots in the corneas of regular soft contact lens users from an Asian country

PURPOSE

: To investigate factors associated with the presence of microdot deposits or white dots (WDs) on confocal microscopy in regular soft contact lens (SCL) users.

METHODS

: This cross-sectional observational study investigated changes in the cornea in regular SCL users by using an in vivo slit-scanning microscope (ConfoScan 3). Images were analyzed by noting the presence of highly reflective WDs. Factors associated with WDs were analyzed by using an unpaired t test with Welch correction.

RESULTS

: There were 56 SCL wearers. Of these, a group of 10 had WDs (GWD) in various parts of the cornea. They had worn SCLs for 7 to 20 years and had a mean total duration of SCL wear of 13.6 +/- 4.4 years. Their mean age was 35.8 +/- 10.4 years. They were compared with a group of SCL wearers with no evidence of WDs (GNWD). The mean age of GNWD was 29.1 +/- 7.2 years, with a mean duration of SCL use of 8.17 +/- 5.1 years. The two groups were compared in terms of age, total duration of SCL wear (years), duration in hours per week, SCL water content (%), mean cell density in the endothelium and stroma, endothelial cell coefficient of cell size variation, and percentage of hexagonal cells. Only the duration of SCL wear was significantly associated with the presence of WDs (p=0.0042). WDs were most commonly found in the posterior stroma (n = 9). Two patients had WDs in the epithelium, with one of these having WDs in the endothelium. All patients except one with a hazy left eye scan had WDs bilaterally and symmetrically.

CONCLUSIONS

: Confocal microscopy allows visualization of WDs in the corneas of Asian regular SCL users. Patients with WDs have a longer history of SCL wear. WDs may represent an early stage of corneal disease or degeneration associated with alterations in cell behavior.

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.

In Vivo Confocal Microscopy of the Ocular Surface

Over the past two decades, the applications of in vivo confocal microscopy to the investigation of ocular surface diseases in the living eye have been greatly extended. Confocal microscopy enables detailed investigation of tarsal and palpebral conjunctiva, central and peripheral cornea, tear film, and lids, and it allows evaluation of the ocular surface at the cellular level. High-quality imaging in both contact and noncontact modes has allowed new understanding of the functions of the ocular surface system, and in the coming years, such knowledge will become increasingly comprehensive and specific. Confocal microscopy may provide a link between well-established ex vivo histology and in vivo study of ocular pathology, not only in clinical science but also in clinical practice. The purpose of this review is to summarize the current knowledge about in vivo confocal microscopy of the ocular surface.

The corneal stroma during contact lens wear

Recent technological advances have lead to novel descriptions of the microanatomy of the corneal stroma. In the first section of this review, these findings and the role they play in the maintenance of vital properties such as corneal transparency, mechanical strength, homeostasis, wound-healing response and metabolism are described. In the second part, contact lens induced stromal alterations such as acidosis, oedema, striae, thinning and opacities are reviewed as well as the more recently described phenomenon of microdot deposits and keratocyte loss with an emphasis on how lens wearing stromal effects can be minimised.

Konfokale In-vivo-Hornhautmikroskopie nach Keratoplastik

BACKGROUND

Seven eyes with clear grafts after penetrating keratoplasty were examined with in vivo confocal corneal microscopy in 1999. Our aim was the confocal microscopic investigation of the subclinical changes in clear grafts after long-term follow-up.

METHODS

The preoperative diagnoses were keratoconus (two), granular corneal dystrophy (two), pseudophakic bullous keratopathy due to ACL (two), and corneal ulcer (one). The epithelium, corneal nerves, keratocytes of the anterior and posterior stroma, and endothelium were evaluated with confocal microscopy.

RESULTS

Mean density of basal epithelial cells was 3928+/-378 cells/mm(2) at 15 months and 3284+/-565 cells/mm(2) at 66 months postoperatively. At 15 months the keratocyte density was 750+/-113 cells/mm(2) in the anterior stroma and 601+/-98 cells/mm(2) in the posterior stroma, at 66 months 383+/-53 cells/mm(2) in the anterior stroma and 411+/-98 cells/mm(2) in the posterior stroma. Endothelial cell density decreased from 1719+/-576 cells/mm(2) (15 months) to 965+/-272 cells/mm(2) (66 months).

CONCLUSIONS

In the follow-up period a significant decrease of keratocyte and endothelial cell density was detectable with confocal microscopy. The clinical importance of our findings must be clarified with further examinations on more patients.

Intérêt du microscope confocal cornéen in vivo HRT2 pour l’étude de l’épithélium cornéo-conjonctival

PURPOSE

To show the advantages of the in vivo HRT2 confocal microscope corneal module for studying the superficial and peripheral corneal and conjunctival epithelia.

MATERIAL AND METHODS

We examined 15 patients whose superficial cornea was healthy and ten patients with keratoconjunctivitis sicca and/or rosacea. Some conjunctival imprints where taken on patients with superficial ocular disease and examined by immunofluorescence.

RESULTS

We found superficial corneal epithelial cells, corneoconjunctival Langerhans and dendritic cells, goblet cells, limbic epithelial junction, new blood vessels, as well as deeper corneal structures such as Bowman's membrane, keratocytes, corneal nerves, and endothelium. We also observed pathological corneal epithelium in keratoconjunctivitis sicca and substantial inflammatory and vascular changes in rosacea. In two cases of stem cell deficiency associated with rosacea, we observed goblet cells in the corneal epithelium. An interesting anatomical-clinical parallelism between in vivo confocal microscopy images and those obtained by ex vivo immunofluorescence was observed.

DISCUSSION

Central corneal pictures after explorations by in vivo HRT2 confocal microscopy are similar to those obtained with standard confocal microscopy. But conjunctiva, peripheral cornea and limbus are better examined at the surface and at medium depth with the HRT2. Diagnosis and therapy of superficial corneoconjunctival and limbal diseases are therefore made easier in vivo.

Determination of Microdot Stromal Degenerations Within Corneas of Long-term Contact Lens Wearers by Confocal Microscopy

PURPOSE

To ascertain whether a relationship exists between the presence of microdot deposits within the corneal stroma of long-term contact lens wearers as seen by confocal microscopy and the contact lens wear time, material, or other patient variables.

METHODS

Thirty-six myopic patients with a 15- to 43-year history of hard, rigid gas-permeable, or soft hydrogel contact lens wear and 12 age-matched emmetropic or spectacle-corrected myopic volunteers were included in this study. The numerical density and size of microdot deposits within the anterior, mid, and posterior stroma were determined with the confocal microscope, and the data were subjected to multiple regression statistical analysis.

RESULTS

Microdot deposits were encountered throughout the entire depth of the corneal stroma in all contact lens wearers. None of the control subjects showed microdot deposits. The numerical densities and the size range of microdots were similar in each of the stromal layers (anterior, mid, and posterior), with total mean values (+/- SD) for each parameter being 65.1 x 10(3) +/- 26.9 x 10(3) dots/mm (range, 21.4 x 10(3) to 121.1 x 10(3) dots/mm) and 3.04 +/- 0.92 microm (range, 1.5-5.0 microm), respectively.

CONCLUSIONS

Microdot deposits may represent granules of lipofuscinlike material within the corneal stroma of long-term contact lens wearers, formed as a result of chronic oxygen deprivation and chronic microtrauma to the cornea. No one in the control group showed microdot deposits. Among the independent variables, soft contact lens wear time had the most profound influence on numerical microdot density and size in our statistical equations.

David Maurice's contributions to optical ophthalmic instrumentation: roots of the scanning slit clinical confocal microscope

This paper explores the seminal contributions of David Maurice to the field of ophthalmic instrumentation. His development of the specular microscope, the scanning slit optical confocal microscope, and the corneal microfluorometer resulted in advances in our understanding of corneal morphology, physiology, and pathology. The development of the scanning slit, clinical confocal microscope is not a new paradigm or a paradigm shift, but a continuous series of interlinked technical advances from the early work of Vogt to Thaer's development of a clinical confocal microscope. For each instrument both the connection to the prior work of others and the unique advances are discussed and contrasted. This paper develops the connections and parallel developments in the instrument developments of Goldmann, Maurice, Svishchev, Baer, Koester, Masters, and Thaer. The evidence in support of the thesis consists of published papers, patents, personal communication, and study of Goldmann's book collection in Bern. A second theme is that knowledge of physics is a prerequisite for optical instrument development in ophthalmology. David Maurice had a university degree in physics and Hans Goldmann learned physics from his books. The contributions of David Maurice to optical instrumentation follow the major contributions of Goldmann and facilitated and stimulated other scientists who acknowledged their important intellectual debt to David Maurice.

Occupational corneal argyrosis in art silver solderers

PURPOSE

To determine the value of confocal and specular microscopy in the examination of corneal argyrosis in art silver solderers.

METHODS

Six patients with corneal argyrosis underwent a complete physical and ophthalmologic examination. Specular microscopy was performed in three cases, and in vivo confocal microscopy in four cases. Ultrasound biomicroscopy and corneal topography were performed in three cases. A conjunctival specimen of one patient was examined histologically in paraffin sections.

RESULTS

Slit-lamp examination showed gray, diffuse opacities in the deep corneal stroma. Confocal microscopy showed highly reflective deposits with a granular pattern anterior to the corneal endothelium and hypereflective keratocyte nuclei with visible cytoplasm in the anterior stroma. Specular microscopy demonstrated round white bodies anterior to the corneal endothelium. Silver deposits were not found histologically.

CONCLUSIONS

Silver solderers with long-term exposure to silver compounds are at high risk of developing corneal argyrosis. We conclude that specular microscopy and in vivo confocal microscopy provided important information for the diagnosis of corneal argyrosis.

Confocal microscopic evaluation of particles at the corneal flap interface after myopic laser in situ keratomileusis

PURPOSE

To investigate the appearance and origin of interface particles in the cornea after myopic laser in situ keratomileusis (LASIK) using the confocal microscope.

SETTING

Department of Optometry and Neuroscience, UMIST, Manchester, United Kingdom.

METHODS

An in vivo slit-scanning, real-time confocal microscope (Tomey ConfoScan P4) fitted with an Achroplan(R) 40X/0.75 NA immersion objective (Zeiss) was used to examine the morphology of the central cornea in 6 patients (12 eyes) at the initial visit (before surgery) and 1 week and 1, 3, and 6 months after LASIK for myopia.

RESULTS

In all eyes, several interspersed particles of variable size and brightness were observed 1 week after surgery at the flap interface. The overall density of these particles decreased with time (F = 14.34, P =.01). For analysis, the particles were divided by density into high brightness and low brightness. The low-brightness particles significantly decreased with time (F = 13.26, P =.02). The high-brightness particles remained constant in density at all postoperative visits (F = 1.3, P =.15). CONCLUSIOINS: The particles of low reflectivity may represent 1 or more types of remains. It is unclear whether the low-reflectivity particles will eventually disappear. The high-reflectivity particles may represent fine metallic debris arising from the mechanical drive mechanism and/or the disposable knife of the microkeratome. If they are metallic and magnetic, they could be cleared during surgery (immediately before flap replacement) using a specially adapted magnet.

Confocal microscopy of Thygeson's superficial punctate keratopathy

PURPOSE

To describe the changes seen with the confocal microscope in Thygeson's superficial punctate keratopathy (TSPK).

METHODS

Confocal microscopy was performed on six patients with TSPK presenting to Manchester Royal Eye Hospital from October 1999 to June 2001. Both eyes were examined including the normal fellow eyes of two patients with unilateral TSPK. Images were compared with age-matched controls.

RESULTS

Irregular nerve fibers, masked by considerable haze, were seen in the subepithelial nerve plexus immediately above Bowman's membrane in TSPK. Generalized haze was also present in the anterior stroma along with areas of high reflectivity, microdots, and reflective bodies. Keratocytes had highly reflective nuclei and cell bodies of irregular size, orientation, and shape. The changes were related to the duration of TSPK, were not seen in normal fellow eyes, and were also present in areas without lesions.

CONCLUSION

Confocal imaging of TSPK demonstrated considerable abnormalities in the subepithelial nerve plexus, Bowman's membrane, and the anterior stroma that were related to disease duration. Similar changes have been reported in a variety of corneal diseases and following laser corneal surgery. Recent evidence has supported interactions between the epithelium and Bowman's membrane and the anterior stroma in corneal disease and after laser corneal surgery. We speculate that such interactions may have a role in TSPK.

In vivo confocal microscopy of the human cornea

AIMS

To describe the optics of in vivo confocal microscopy, its advantages over previous methods, and to summarise the literature that arose from its use for the observation of the human cornea. A critical review of the clinical usefulness of this new technology for the corneal examination is undertaken.

METHODS

Confocal microscopes obtain increased resolution by limiting the illumination and observation systems to a single point. Rapid scanning is used to reconstruct a full field of view and allows for "real time" viewing.

RESULTS

Coronal sections of the in situ epithelium, Bowman's membrane, stroma, and endothelium can be visualised at a resolution of 1-2 micro m. A backscattered light intensity curve allows objective measurements of sublayer thickness and corneal haze to be taken. In vivo confocal microscopy is therefore particularly useful in the areas of infective keratitis, corneal dystrophies, refractive surgery, and contact lens wear, where it aids in differential diagnosis and detection of subtle short and long term changes. Real time endothelial cell assessment can also be performed.

CONCLUSION

Because of their ability to visualise living tissue at cellular levels, confocal microscopes have proved useful additions to the current clinical tools.

Three-dimensional confocal microscopy of the living human eye

Three-dimensional confocal microscopy of the living eye is a major development in instrumentation for biomicroscopy of the eye. This noninvasive optical technology has its roots in the application of optics to reflected light imaging of the eye. These instrument developments began with Leeuwenhoek's use of his single lens microscope to investigate the structure of the eye. There followed a series of connected instruments: the ophthalmoscope, the slit lamp, the specular microscope, and the clinical confocal microscope. In vivo confocal microscopy produces high contrast, reflected light images or optical sections through the depth of living ocular tissue. Stacks of registered optical sections can be transformed by computer visualization techniques into three-dimensional volume images of ocular tissues: cornea, ocular lens, retina, and optic nerve. The clinical confocal microscope has resulted in new diagnostic techniques and new cellular descriptions of ocular disorders and pathology.

Confocal microscopy of the human cornea in vivo

In vivo, scanning-slit, confocal microscopy offers improved resolution and has resulted in new discoveries of corneal pathology at the cellular level. The ability to provide high resolution, real-time images of the full thickness of the living human cornea gives the clinician and the researcher an important new tool.

Microstructural assessment of rare corneal dystrophies using real-time in vivo confocal microscopy

PURPOSE

To analyse and describe three cases of rare corneal dystrophy and highlight their in vivo microstructural features.

METHODS

Subject 1 was diagnosed with a posterior stromal fleck corneal dystrophy Two of her three children were also affected. Subjects 2 and 3 exhibited an almost identical clinical appearance on biomicroscopic examination, such that both clinically were diagnosed as having pre-Descemet's dystrophies. All subjects underwent in vivo confocal microscopy and approximately 300 sequential digital images were obtained and analysed for each cornea.

RESULTS

In vivo confocal microscopy of subject 1 demonstrated an abnormal appearance of numerous large ovoid particles, measuring 50-70 microm in diameter in the mid and posterior stroma as well as smaller hyperreflective dot-like intracellular deposits, of less than 1 microm diameter. Despite the near-identical clinical appearance, subjects 2 and 3 could be clearly differentiated by in vivo confocal microscopy. Subject 2 exhibited small, irregular, optically dense particles, mainly in the anterior stroma, whereas subject 3 possessed classical involvement of the stroma immediately adjacent to Descemet's membrane, with numerous regular small, hyperreflective particles.

CONCLUSIONS

The ability of in vivo confocal microscopy to localize and accurately measure various elements in different corneal layers may help to resolve whether abnormalities are intra- or extracellular, and aid clearer differentiation of rare corneal disorders.

Confocal microscopy of the normal human cornea

The slit-scanning confocal microscope is a new clinical paradigm that allows the living human cornea to be viewed at a magnification of 680 x and a lateral resolution of 1 mum. As such, it allows corneal morphology to be inspected at a cellular level. The corneas of both eyes of 119 subjects who were evenly distributed in age from 10-80 years were examined using a Tomey ConfoScan P4 in-vivo slit-scanning real-time confocal microscope (Erlangen, Germany). Good quality representative images of the various corneal layers were selected for detailed qualitative analysis and are displayed here. A grid of corneal layer versus age was constructed from these images; this tool can be used as a normative confocal microscopy reference against which suspected corneal abnormalities can be assessed.

Confocal microscopy after implantation of intrastromal corneal ring segments

OBJECTIVE

Confocal in vivo real-time microscopy was used to study the corneal morphologic features in eyes after Intrastromal Corneal Ring Segments (ICRS; now called KeraVision INTACS, KeraVision, Inc., Fremont, CA) implantation.

DESIGN

Noncomparative, interventional case series.

PARTICIPANTS

The authors performed confocal real-time microscopy on a total of 21 eyes from 11 patients. Seventeen eyes from 10 patients (five female, five male; mean age 32.3 years; range 22-42 years) underwent uncomplicated ICRS surgery to correct myopia and were examined after surgery (average 8.6 months; range 2-15 months). Three patients had the ICRS implanted into only one eye, and those eyes were compared with the untreated fellow eyes. One eye of another patient was examined 1 and 6 months after ICRS removal.

INTERVENTION

Flying slit-confocal microscopy was performed with water immersion objectives in the corneal center and near the nasal or temporal ICRS. Corneal optical sections were recorded in real time without further digital processing and were reviewed frame by frame.

MAIN OUTCOME MEASURES

Video frames selected from all corneal layers were evaluated qualitatively and quantitatively.

RESULTS

In the central cornea, we found normal morphologic features at all layers. In peripheral sections, epithelial cells with highly reflective nuclei in the basal cell layer were observed in six of 17 eyes (35%) implanted with ICRS. We found an intact corneal nerve plexus and undisturbed corneal endothelium immediately underneath the ICRS. Around the ICRS, moderate fibrosis was seen. In one eye, linear structures in bamboo-like orientation were detected after ICRS removal in the last keratocyte layer underneath the collapsed tunnel.

CONCLUSIONS

Whereas the central corneal zone appears unchanged, the corneal stroma adjacent to the ICRS displays a slight, but distinct, activation of wound healing. Epithelial cells with highly reflective nuclei in this region may be an indicator for an increased biologic stress caused by the device.

Morphological and functional analysis of immortalized human corneal endothelial cells after transplantation

Approximately 50% of donor corneas are unsuitable for keratoplasty due to an unacceptably low endothelial cell count. One way of overcoming this problem and minimizing wastage of donor corneas may be to transplant cultured human corneal endothelial cells onto these. In this study, we examined the morphological characteristics and functional attributes of endothelial layers formed after the transplantation of immortalized cells in vitro. Cultured human corneal endothelial cells, immortalized by transfection with a plasmid encoding SV40 T-antigen, were seeded onto human corneas denuded of their own endothelium. Seven days after transplantation the newly established monolayers were examined by light, confocal and scanning electron microscopy. Endothelial pump function was gauged by monitoring changes in corneal thickness during perfusion of the endothelial face. The endothelia formed from transplanted immortalized cells had a cobblestone-like appearance, being composed of polygonal units joined by junctional complexes. The stromal hydration state of corneas bearing such endothelial layers could be controlled during perfusion. This was an active process achieved via the Na(+)/K(+)-ATPase-dependent endothelial pump, as demonstrated by inhibiting the enzyme with ouabain. Transplantation of immortalized human corneal endothelial cells onto recipient corneas led to the establishment of new monolayers which had the morphology of the native ones in organ-cultured corneas. This model provides us with a means of studying the formation and function of corneal endothelial layers in vitro.

Confocal microscopy in Bowman and stromal corneal dystrophies

OBJECTIVE

To use confocal microscopy to demonstrate the similarity among three autosomal-dominant corneal dystrophies and the diversity of the deposit patterns within a single dystrophy.

DESIGN

A prospective, comparative case series.

PARTICIPANTS

Twenty patients (40 eyes) from 10 families suffering from Bowman or stromal dystrophy agreed to take part: 3 with Reis-Bückler dystrophy, 12 with granular dystrophy, and 5 with lattice type-I dystrophy. Of these, nine had recurrence in their grafts or after phototherapeutic keratectomy before the confocal examination. The confocal images of affected corneas were compared with those of ten normal control eyes (ten subjects).

INTERVENTION

All patients were examined by slit-lamp biomicroscopy. Confocal microscopy was performed with Achroplan 40x/numeric aperture (NA) = 0.75 and 63x/NA = 0.9 water immersion objectives. Image analysis was used to identify the corneal epithelial and stromal deposits correlated with each disorder.

MAIN OUTCOMES MEASURES

Selected images of the corneal layers were evaluated qualitatively for the size, shape, light scattering, and reflection of the deposits.

RESULTS

Slit-lamp biomicroscopy showed stromal involvement in all affected eyes. Confocal microscopy identified epithelial deposits in 30% of the eyes and stromal deposits in all eyes. The deposits within the epithelium were revealed more clearly with the 63x/NA = 0.9 objective (higher numeric aperture). Some of the confocal findings near the Bowman layer were common for all three dystrophies. Normal control eyes showed no epithelial or stromal deposits, either by biomicroscopy or confocal microscopy.

CONCLUSIONS

Confocal microscopy provides an in vivo evaluation of the deposits in the cornea, with a higher resolution than biomicroscopy. The confocal findings common to the three dystrophies may agree with previous hypotheses of the same genetic origin. It may be a useful adjunct to slit-lamp biomicroscopy, particularly when histopathologic studies cannot be performed.

Confocal microscopy of the cornea

This paper provides the clinician and the researcher with an in-depth manual on the use of a scanning-slit confocal light microscope for the clinical examination and investigation of the living human cornea in vivo. The scope of the paper includes a thorough explanation of the principles of various types of confocal microscopes as well as their limitations, a comprehensive review of the development of biomicroscopy of the eye, and a comparison of confocal microscopy and other optical techniques such as optical coherence tomography. The early work of Ridley, Goldmann and others on point illumination in early confocal instruments is described. The main part of the paper describes and illustrates the clinical examination of the living human cornea with the confocal microscope. Figures (many in color) from the normal cornea, the cornea with known parthologies, and the postsurgical cornea are selected for their educational value. Photographs of standard light microscopy of fixed, human corneal sections are compared with confocal maicroscopic images. Where appropriate, slit lamp color photographs are compared with confocal microscopic images. The clinical scanning-slit confocal microscope is an evolving instrument for biomicroscopy of the living eye.