Assessment of conjunctival goblet cell density using laser scanning confocal microscopy versus impression cytology

Imaging assessment of conjunctival goblet cells in dry eye disease

Dry eye disease (DED) is a widespread, multifactorial, and chronic disorder of the ocular surface with disruption of tear film homeostasis as its core trait. Conjunctival goblet cells (CGCs) are specialised secretory cells found in the conjunctival epithelium that participate in tear film formation by secreting mucin. Changes in both the structure and function of CGCs are hallmarks of DED, and imaging assessment of CGCs is important for the diagnosis, classification, and severity evaluation of DED. Existing imaging methods include conjunctival biopsy, conjunctival impression cytology and in vivo confocal microscopy, which can be used to assess the morphology, distribution, and density of the CGCs. Recently, moxifloxacin-based fluorescence microscopy has emerged as a novel technique that enables efficient, non-invasive and in vivo imaging of CGCs. This article presents a comprehensive overview of both the structure and function of CGCs and their alterations in the context of DED, as well as current methods of CGCs imaging assessment. Additionally, potential directions for the visual evaluation of CGCs are discussed.

Multi-Focus Image Fusion Using Focal Area Extraction in a Large Quantity of Microscopic Images

The non-invasive examination of conjunctival goblet cells using a microscope is a novel procedure for the diagnosis of ocular surface diseases. However, it is difficult to generate an all-in-focus image due to the curvature of the eyes and the limited focal depth of the microscope. The microscope acquires multiple images with the axial translation of focus, and the image stack must be processed. Thus, we propose a multi-focus image fusion method to generate an all-in-focus image from multiple microscopic images. First, a bandpass filter is applied to the source images and the focus areas are extracted using Laplacian transformation and thresholding with a morphological operation. Next, a self-adjusting guided filter is applied for the natural connections between local focus images. A window-size-updating method is adopted in the guided filter to reduce the number of parameters. This paper presents a novel algorithm that can operate for a large quantity of images (10 or more) and obtain an all-in-focus image. To quantitatively evaluate the proposed method, two different types of evaluation metrics are used: “full-reference” and “no-reference”. The experimental results demonstrate that this algorithm is robust to noise and capable of preserving local focus information through focal area extraction. Additionally, the proposed method outperforms state-of-the-art approaches in terms of both visual effects and image quality assessments.

Mechanobiology of conjunctival epithelial cells exposed to wall shear stresses

The human conjunctival epithelial cells (HCEC) line the inner sides of the eyelids and the anterior part of the sclera. They include goblet cells that secret mucus into the tear film that protects the ocular surface. The conjunctival epithelium is subjected to mechano-physical stimuli due to eyelid movement during blinking, during wiping and rubbing the eyes, and when exposed to wind and air currents. We cultured primary HCEC under air-liquid interface (ALI) conditions in custom-designed wells that can be disassembled for installation of the in vitro model in a flow chamber. We exposed the HCEC after ALI culture of 8-10 days to steady and oscillatory airflows. The in vitro model of HCEC was exposed to steady wall shear stresses (sWSS) of 0.5 and 1.0 dyne/cm² for lengths of 30 and 60 min and to oscillatory wall shear stresses (oWSS) of 0.5 and 0.77 dyne/cm² amplitudes for a length of 10 min. Cytoskeletal alterations and MUC5AC mucin secretion in response to WSS were investigated using immunohistochemically fluorescent staining and enzyme-linked lectin assay (ELLA), respectively. The results revealed that both exposure times and sWSS values increased the polymerization of F-actin filaments while mucin secretion decreased. However, after a recovery of 24 h in the incubator we observed a decrease of F-actin fibers and mucin secretion only for exposure of 30 min. The length of exposure was more influential on cytoskeletal alterations than the level of sWSS. The very small effect of sWSS on mucin secretion is most likely related to the much smaller amount of goblet cell than in other mucus-secreting tissue. The results for both oWSS amplitudes revealed similar trends regarding F-actin and mucin secretion. Immediately post-exposure we observed an increase in polymerization of F-actin filaments while mucin secretion decreased. However, after 24-h recovery we observed that both F-actin and mucin secretion returned to the same values as for unexposed cultures. The results of this study suggest that WSS should be considered while exploring the physiological characteristics of HCEC.

Moxifloxacin based axially swept wide-field fluorescence microscopy for high-speed imaging of conjunctival goblet cells

Goblet cells (GCs) in the conjunctiva are specialized epithelial cells producing mucins on the ocular surface. GCs play important roles in maintaining homeostasis of the ocular surface, and GC dysfunction is associated with various complications including dry eye diseases. Current GC examination methods, which are conjunctival impression cytology and confocal reflection microscopy, have limitations for routine examination. Fluorescence microscopy using moxifloxacin was recently introduced as a non-invasive and high-contrast imaging method, but further development is needed to be used for GC examination. Here we developed a non-invasive high-speed high-contrast GC imaging method, called moxifloxacin based axially swept wide-field fluorescence microscopy (MBAS-WFFM). This method acquired multiple fluorescence images with the axial sweeping of the focal plane to capture moxifloxacin labeled GCs on the tilted conjunctival surface in focus and generated all-in-focus images by combining the acquired images. The imaging field of view and imaging speed were increased to 1.6 mm × 1.6 mm and 30 fps. An image processing method was developed for the analysis of GC density. MBAS-WFFM was applied to alkali burn mouse models and detected GC damage and recovery via longitudinal imaging. MBAS-WFFM could assess the status of GCs rapidly and non-invasively. We anticipate MBAS-WFFM to be a starting point for non-invasive GC examination and the diagnosis of GC associated diseases. For example, MBAS-WFFM could be used to classify dry eye diseases into detail categories for effective treatment.

Association between conjunctival goblet cells and corneal resident dendritic cell density changes in new contact lens wearers

BACKGROUND

To explore the interlink between conjunctival goblet and corneal dendritic cell density after six months of lens wear and to predict dendritic cell migration to the central cornea based on goblet cell loss in the conjunctiva as a response to contact lens wear.

METHODS

Sixty-nine subjects who had never previously worn contact lenses were observed for six months; 46 were fitted with contact lenses and 21 served as a control group. Corneal confocal microscopy was used to quantify goblet and dendritic cell density before and after six months of daily lens wear. Symptomatic and asymptomatic groups were identified in the lens-wearing group using a combination of signs and symptoms present. Pearson's correlation was used to determine associations between the total change of cell densities after six months of lens wear.

RESULTS

At baseline, there was no association between conjunctival goblet and corneal dendritic cell density (p > 0.05). After six months, there was an inverse association between the absolute change of conjunctival goblet and corneal dendritic cell density (ρ = -0.34, p = 0.03) in all participants (n = 69). Dendritic cell density in the central cornea was increased by 1.5 cells/mm² for every decrease of 1 goblet cell/mm² in the conjunctiva.

CONCLUSIONS

After six months of wear, contact lens-induced goblet cell loss can partially predict resident corneal dendritic cell migration to the central cornea (observed as an increase in dendritic cell density). The associations between total cell density change after six months was established in wearers regardless of lens symptomatology, suggesting that cell density changes as a physiological adaptation to regulate the effect of contact lens wear on the ocular surface.

Novel Approaches for Imaging-Based Diagnosis of Ocular Surface Disease

Imaging has become indispensable in the diagnosis and management of diseases in the posterior part of the eye. In recent years, imaging techniques for the anterior segment are also gaining importance and are nowadays routinely used in clinical practice. Ocular surface disease is often synonymous with dry eye disease, but also refers to other conditions of the ocular surface, such as Meibomian gland dysfunction or keratitis and conjunctivitis with different underlying causes, i.e., allergies or infections. Therefore, correct differential diagnosis and treatment of ocular surface diseases is crucial, for which imaging can be a helpful tool. A variety of imaging techniques have been introduced to study the ocular surface, such as anterior segment optical coherence tomography, in vivo confocal microscopy, or non-contact meibography. The present review provides an overview on how these techniques can be used in the diagnosis and management of ocular surface disease and compares them to clinical standard methods such as slit lamp examination or staining of the cornea or conjunctiva. Although being more cost-intensive in the short term, in the long term, the use of ocular imaging can lead to more individualized diagnoses and treatment decisions, which in turn are beneficial for affected patients as well as for the healthcare system. In addition, imaging is more objective and provides good documentation, leading to an improvement in patient follow-up and education.

On the in vivo assessment of goblet cells of the human bulbar conjunctiva by confocal microscopy - A review

BACKGROUND

In vivo confocal microscopy (IVCM) has been used for over 10 years to assess the goblet cell density (GCD) within the human conjunctiva, but the reported values have been variable with no obvious indications as to why.

METHODS

From publications between 2008 and 2019, representative GCD values were extracted, as well as on the image sampling strategy used.

RESULTS

Average GCD values for any particular group of individuals ranged from 7 to 979 goblet cells / sq. mm, and with one notable outlier removed, an overall group-mean value for GCD (+/- SD) from single site locations was 207 +/- 143 goblet cells / sq. mm from 15 data sets for those usually designated as control subjects, with a value of 190 +/- 161 goblet cells / sq. mm calculated from 20 single site data sets from other (patient) groups. An overall analysis indicated that the reported average values for GCD from different groups of individuals increased according to the number of images assessed / individual (Spearman rho = 0.304), on the number of individuals evaluated to generate an averaged value for each group (rho = 0.367), and the total number of images assessed (rho = 0.346, multivariate analysis partial r = greater or = to 0.522).

CONCLUSIONS

In the use of confocal microscopy to assess the number of goblet cells in the human bulbar conjunctiva, the substantial differences reported appear to be linked to the protocols used for image selection, and some type of standardization needs to be developed.

Multiple count sampling of goblet cells in microscope high-power fields using conjunctival impression cytology

BACKGROUND

Published studies indicate that assessments of goblet cell density using conjunctival impression cytology has provided very variable results, but the reasons for this are unclear. Systematic analyses of the sources of variability are required.

METHODS

From 20 healthy young adults, conjunctival impression cytology specimens were obtained using a supported filter unit applied to the superior bulbar conjunctiva. The filters were stained with Giemsa and 10 non-overlapping, randomly selected high-power field images were obtained from each specimen and the numbers of goblet cells per high-power field counted.

RESULTS

From all 200 high-power fields assessed, the numbers of goblet cells ranged from zero to 74, with an overall mean value of 11.6 ± 14.8 per high-power field. From each successive set of 10 microscope field images from all individuals, the average number of goblet cells ranged from 23.2 in the first high-power field that obviously included numerous goblet cells down to 6.2 per high-power field. As the outcome from multiple counts/individual was systematically increased, these averages progressively decreased from 23.2 to 11.6 per high-power field, and while the standard deviation values also progressively declined (from 7.9 to 5.5 per high-power field), the relative variability (as the co-efficient of variation) did not, and increased to averaged values of over 100 per cent.

CONCLUSIONS

These analyses indicate that there is a benefit of making multiple counts of goblet cells from different high-power fields, but that there is no obvious benefit of using more than five to seven high-power fields for any particular specimen.

In vivo fluorescence imaging of conjunctival goblet cells

Conjunctival goblet cells (GCs) are specialized epithelial cells that secrete mucins onto the ocular surface to maintain the wet environment. Assessment of GCs is important because various ocular surface diseases are associated with their loss. Although there are GC assessment methods available, the current methods are either invasive or difficult to use. In this report, we developed a simple and non-invasive GC assessment method based on fluorescence imaging. Moxifloxacin ophthalmic solution was used to label GCs via topical administration, and then various fluorescence microscopies could image GCs in high contrasts. Fluorescence imaging of GCs in the mouse conjunctiva was confirmed by both confocal reflection microscopy and histology with Periodic acid-Schiff (PAS) labeling. Real-time in-vivo conjunctival GC imaging was demonstrated in a rat model by using both confocal fluorescence microscopy and simple wide-field fluorescence microscopy. Different GC densities were observed in the forniceal and bulbar conjunctivas of the rat eye. Moxifloxacin based fluorescence imaging provides high-contrast images of conjunctival GCs non-invasively and could be useful for the study or diagnosis of GC related ocular surface diseases.

Diagnostic criteria for limbal stem cell deficiency before surgical intervention-A systematic literature review and analysis

An accurate diagnosis of limbal stem cell deficiency (LSCD) is the premise of an appropriate treatment; however, there is no consensus about the diagnostic criteria for LSCD. We performed a systematic literature search of the peer-reviewed articles on PubMed, Medline, and Ovid to investigate how LSCD was diagnosed before surgical intervention. The methods used to diagnose LSCD included clinical presentation, impression cytology, and in vivo confocal microscopy. Among 131 eligible studies (4054 eyes), 26 studies (459 eyes, 11.3%) did not mention the diagnostic criteria. In the remaining 105 studies, the diagnosis of LSCD was made on the basis of clinical examination alone in 2398 eyes (62.9%), and additional diagnostic tests were used in 1047 (25.8%) eyes. Impression cytology was used in 981 eyes (24.2%), in vivo confocal microscopy was used in 29 eyes (0.7%), and both impression cytology and in vivo confocal microscopy were used in 37 eyes (0.9%). Our findings suggest that only a small portion of patients underwent a diagnostic test to confirm the diagnosis of LSCD. Treating physicians should be aware of the limitations of clinical examination in diagnosing LSCD and perform a diagnostic test whenever possible before surgical intervention.

Reconsidering the central role of mucins in dry eye and ocular surface diseases

Mucins are key actors in tear film quality and tear film stability. Alteration of membrane-bound mucin expression on corneal and conjunctival epithelial cells and/or gel-forming mucin secretion by goblet cells (GCs) promotes in ocular surface diseases and dry eye disease (DED). Changes in the mucin layer may lead to enhanced tear evaporation eventually contributing to tear hyperosmolarity which has been associated with ocular surface inflammation. Inflammatory mediators in turn may have a negative impact on GCs differentiation, proliferation, and mucin secretion. This sheds new light on the position of GCs in the vicious circle of DED. As contributor to ocular surface immune homeostasis, GC loss may contribute to impaired ocular surface immune tolerance observed in DED. In spite of this, there are no tools in routine clinical practice for exploring ocular surface mucin deficiency/dysregulation. Therefore, when selecting the most appropriate treatment options, there is a clear unmet need for a better understanding of the importance of mucins and options for their replacement. Here, we comprehensively revisited the current knowledge on ocular surface mucin biology, including functions, synthesis, and secretion as well as the available diagnostic tools and treatment options to improve mucin-associated homeostasis. In particular, we detailed the potential link between mucin dysfunction and inflammation as part of the uncontrolled chronic inflammation which perpetuates the vicious circle in DED.

Epithelial dysplasia in pterygium postoperative granuloma

Pterygium postoperative granuloma (PPG) is one of the common complications of pterygium surgery. In order to provide the structural features of PPG, and to further explore its pathogenetic mechanism, we analyzed clinical and pathological characteristics of 12 PPG cases. New blood vessels were observed under a slit lamp in PPG and peripheral conjunctival tissues. In vivo confocal imaging showed that there was extensive neovascularization in the stroma, accompanied by infiltration of dendritic cells and inflammatory cells. Dense fibrous structures were observed in some PPG tissues. H&E staining results confirmed neovascularization and inflammatory cells in PPG tissues. In addition, H&E staining exhibited epithelioid tissue covering some PPG tissues. The immunofluorescence results demonstrated that the PPG epithelium was negative for K19, K10 and Muc5AC. Compared with the normal conjunctiva and pterygium, the expression of collagen IV in PPG basement membrane decreased, the expression of pan-cytokeratin (PCK), claudin 4 and E-cadherin in PPG epithelium was significantly lower, while the expression of vimentin, α-SMA and Snail was significantly increased. Therefore, our results suggest that the expression of epithelial keratin markers and goblet cell specific mucin marker is downregulated in the PPG tissues, and it likely is associated with the occurrence of EMT in granulomatous tissues.