Mucus alteration and eye dryness. A possible relationship

Why Chain Length of Hyaluronan in Eye Drops Matters

The chain length of hyaluronan (HA) determines its physical as well as its physiological properties. Results of clinical research on HA eye drops are not comparable without this parameter. In this article methods for the assessment of the average molecular weight of HA in eye drops and a terminology for molecular weight ranges are proposed. The classification of HA eye drops according to their zero shear viscosity and viscosity at 1000 s-1 shear rate is presented. Based on the gradient of mucin MUC5AC concentration within the mucoaqueous layer of the tear film a hypothesis on the consequences of this gradient on the rheological properties of the tear film is provided. The mucoadhesive properties of HA and their dependence on chain length are explained. The ability of HA to bind to receptors on the ocular epithelial cells, and in particular the potential consequences of the interaction between HA and the receptor HARE, responsible for HA endocytosis by corneal epithelial cells is discussed. The physiological function of HA in the framework of ocular surface homeostasis and wound healing are outlined, and the influence of the chain length of HA on the clinical performance of HA eye drops is illustrated. The use of very high molecular weight HA (hylan A) eye drops as drug vehicle for the next generation of ophthalmic drugs with minimized side effects is proposed and its advantages elucidated. Consequences of the diagnosis and treatment of ocular surface disease are discussed.

Ultrastructural Study of the Conjunctiva in Patients with Keratoconjunctivitis Sicca not Associated with Systemic Disorders

Purpose

The aim of this work was to evaluate ultrastructural alterations of the conjunctiva during the clinical course of keratoconjunctivitis sicca (KCS), and to detect its earliest and most characteristic morphological changes.

Methods

The conjunctiva was studied in biopsies from 75 patients and 10 controls. Patients were classified according to the results of the Schirmer I test, break-up time, rose Bengal staining, osmolarity and impression cytology.

Results

The conjunctiva in these KCS patients showed progressive hyperplasia, hypertrophy and cellular flattening, with diminution of goblet cell density and microvilli. In the severe cases, the epithelial cells lost their organelles, and fibrous material increased. From the early phases of KCS, clear nuclear alterations (indentation, binucleation) were found, but pyknotic nuclei or anucleated cells were only observed in the most severe cases. From the earliest stages to the most severe cases of KCS, decreases in cell membrane interdigitations were observed parallel to increases in the number and size of desmosomes. There were also increases in the number of inflammatory cells. Alterations in blood vessels were only observed in the most severe cases.

Conclusions

Morphological studies alone were able even in the earliest phases of KCS, to detect the squamous metaplasia that progresses from the surface of the epithelium to the connective tissue. This degenerative or adaptative cellular process was characterized mainly by marked proliferation of the cytoskeleton and a general loss of organelles, mitochondria being the least affected.

New Perspectives on Dry Eye Definition and Diagnosis: A Consensus Report by the Asia Dry Eye Society

For the last 20 years, a great amount of evidence has accumulated through epidemiological studies that most of the dry eye disease encountered in daily life, especially in video display terminal (VDT) workers, involves short tear film breakup time (TFBUT) type dry eye, a category characterized by severe symptoms but minimal clinical signs other than short TFBUT. An unstable tear film also affects the visual function, possibly due to the increase of higher order aberrations. Based on the change in the understanding of the types, symptoms, and signs of dry eye disease, the Asia Dry Eye Society agreed to the following definition of dry eye: "Dry eye is a multifactorial disease characterized by unstable tear film causing a variety of symptoms and/or visual impairment, potentially accompanied by ocular surface damage." The definition stresses instability of the tear film as well as the importance of visual impairment, highlighting an essential role for TFBUT assessment. This paper discusses the concept of Tear Film Oriented Therapy (TFOT), which evolved from the definition of dry eye, emphasizing the importance of a stable tear film.

Functional morphology of mucosal goblet cells based on spatial separation of orifice openings to the surface--application to the rabbit bulbar conjunctiva

The purpose of the study was to assess spatial separation of goblet cell orifices observed at the surface of the rabbit bulbar conjunctiva by scanning electron microscopy (SEM) specimens of the bulbar conjunctiva from 8 healthy pigmented rabbits were obtained using a special preparation technique by which the tissue was carefully stretched out during glutaraldehyde fixation. On high magnification prints of SEM images of the conjunctival surface, the locations of goblet cell openings (orifices) to the apical surface were marked and the centre-to-centre spacing between all such orifices measured. Across the regions of interest (ROI), with averaged dimensions of 322 μm × 230 μm (adjusted for tissue shrinkage), the averaged value for the distances between all orifices was 196 μm (range 141-241 μm), with the calculated density of orifices being 412 mm(-2). A sequential order-based analysis of the spatial separation between orifices indicated a predictable value of 6 μm, a separation that showed a nearly linear inter-dependence over distances of at least 200 μm. The openings of goblet cells to the surface of unstimulated bulbar conjunctiva have a organized spatial distribution that is consistent with there being an organized control of goblet cell secretion.

Assessment of goblet cell orifice distribution across the rabbit bulbar conjunctiva based on numerical density and nearest neighbors analysis

PURPOSE

To assess density and spatial distribution of the goblet cell orifices at the surface of the rabbit bulbar conjunctiva as an indicator of functional activity.

METHODS

Specimens of the superior or inferior bulbar conjunctiva from six healthy young adult (2 kg) pigmented rabbits were obtained using a special preparation technique by which the conjunctiva was carefully stretched out during fixation with buffered glutaraldehyde. The apical surface of the specimens was examined by scanning electron microscopy. From high magnification prints, the areas and dimensions of 32-49 orifices/image were measured. In addition, the centre-to-centre spacing and spatial distribution of the orifices were assessed using a nearest neighbors principle.

RESULTS

The bulbar conjunctival surface is composed of polygonal cells decorated with surface microplicae and in between which are individual goblet cell orifices. The goblet cell orifices are characterized by tending to be oval in shape (long:short dimensions ratio of 1.57 +/- 0.23) and usually having a distinct line of microvilli around the perimeter. The orifices had a wide range of areas (from 13 to 188 μm(2); group mean +/- SD of 54 +/- 36 μm(2)), and distribution of orifice areas was skewed or even bimodal. The overall orifice density was 387 +/- 68/mm(2), with the group-averaged nearest neighbors distance being 34 +/- 3 μm. Comparisons of the measured nearest neighbors distances to that for an optimum spacing based on numerical density reveals the goblet cell orifices to be slightly further apart and that they were not obviously in groups or clustered.

CONCLUSIONS

Goblet cell orifices at the bulbar conjunctival surface, a presumed indicator of functional secretory activity, appear to have reproducible density and a discrete and reasonably predictable spatial distribution.

Goblet cells of the normal human bulbar conjunctiva and their assessment by impression cytology sampling

Goblet cells of the conjunctiva are the main source of mucus for the ocular surface. The objectives of this review are to consider the goblet cells as assessed by various histological, cytological and electron microscopy methods, and to assess the consistency of published reports (over more than 25 years) of goblet cell density (GCD) from impression cytology specimens from nominally healthy human subjects. Reported GCD values have been notably variable, with a range from 24 to 2226 cells/mm² for average values. Data analysis suggests that a high density of goblet cells should be expected for the healthy human conjunctiva, with a tendency toward higher values in samples taken from normally covered locations (inferior and superior bulbar conjunctiva) of the open eye (at 973 +/- 789 cells/ mm²) than in samples taken from exposed (interpalpebral) locations (at 427 +/- 376 cells/mm²). No obvious change in GCD was found with respect to age, perhaps because the variability of the data did not allow detection of any age-related decline in GCD. Analyses of published data from 33 other sources indicated a trend for GCD to be lower than normal across a spectrum of ocular surface diseases.

Tear Film Lipid Layer Alterations in Allergic Conjunctivitis

PURPOSE

To assess the alterations of the tear film lipid layer and tear functions in patients with seasonal allergic conjunctivitis (SAC) and to compare the results with healthy control subjects.

METHODS

Seventy-eight eyes of 39 consecutive patients diagnosed as SAC (mean age 32.6 years; 11 male, 28 female) as well as 20 eyes of 10 healthy control subjects (mean age 32.5 years; 6 male, 4 female) underwent slit-lamp examinations, tear film breakup time measurements (BUT), corneal fluorescein stain scoring, Schirmer test, and tear film lipid layer interferometry. The 2 groups were then compared for the examined parameters. RAST and serum IgE level evaluations were also carried out in the patients to confirm the diagnosis of allergy.

RESULTS

The mean BUT was 3.4 +/- 1.5 seconds in patients with SAC compared with the mean value of 12.4 +/- 2.4 seconds in the controls (P < 0.05). There were no significant differences in relation to Schirmer test values between the 2 groups; 78% of the patients with SAC had grade 3 or above dry eye change in tear film lipid layer interferometry, whereas none of the controls had an interferometry grade greater than 3 (grade 1-2 normal; grade 3-4 dry eye; grade 5 severe dry eye). Eyes with SAC had significantly higher tear film lipid layer thickness ranges compared with the control eyes (P < 0.05).

CONCLUSION

SAC was associated with advanced tear instability and thickening of the tear film lipid layer. Evaluation of the tear film lipid layer thickness might be useful in the assessment of the extent of dry eye disease and the treatment outcomes in patients with allergy.

Menopause and dry eye. A possible relationship

The hormonal status and in particular sex steroids play a role in the ocular surface homeostasis and function, during the whole life and in both sexes, accomplished by estrogenic and androgenic receptors located on corneal and conjunctival epithelia and Meibomian gland. The ocular surface is an integrated unit and any dysfunction results in a scarce or unstable preocular tear film which produces dry eye, a chronic inflammatory condition with increasing incidence as people get older but always more frequent among females. In post-menopausal women endocrine changes join the aging effects in the pathogenesis of dry eye, but still it remains controversial whether estrogen or androgen deficiency or their imbalance impair ocular surface function. Another questionable issue concerns the efficacy of hormonal replacement therapy in the amelioration of dry eye symptoms and recovery of tear function, since the scientific literature stands in between a therapeutic or a promoting effect of eye dryness. Therapy of dry eye is usually based upon topical administration of tear substitutes; estrogen or androgen-based eye drops represents a promising innovative treatment based upon important scientific rationale.

Heterogeneity in the ultrastructure of the mucous (goblet) cells of the rabbit palpebral conjunctiva

AIM

The purpose of this study was to assess objectively the ultrastructure of the secretory granules in rabbit conjunctival mucin-producing 'goblet' cells.

METHOD

The upper eyelids from five young adult dioestrous female rabbits were dissected out, stretched onto a cardboard support and prepared for transmission electron microscopy by repeated application of an isotonic two per cent glutaraldehyde fixative at room temperature. Post-fixation treatment included osmium tetroxide and staining with uranyl acetate and lead citrate. Low magnification micrographs were taken of the goblet cells of the conjunctiva, printed at a magnification of approximately 6,000 and the number, size and features of the secretory granules assessed.

RESULTS

Across the entire palpebral conjunctiva of all five rabbits, the majority of mucous cells displayed a goblet shape and the secretory granules were uniformly pale in staining. The average width of the goblet cells was 10.8 +/- 1.1 microm and the diameter of the secretory granules was 0.82 +/- 0.16 microm. However, in localised regions across the palpebral conjunctiva of two of the rabbits, some goblet cells were different in that the secretory granules had either a denser-staining core, in which some of the granules were densely staining (while others were pale) or most of the granules were densely staining. These mucous cells had an average diameter of 10.3 +/- 1.7 microm and the granule diameters averaged 0.88 +/- 0.01 microm. For these abnormal goblet cells, inflammatory cells were found in their immediate vicinity. Occasionally, goblet cells were seen to be in the process of degranulation with associated apparent cell necrosis and the mucin granule diameter was close to 1 microm.

CONCLUSIONS

The ultrastructure of the mucin-containing secretory granules of the conjunctival mucous cells is not necessarily homogeneous in character and further attention needs to be given to the effects of localised inflammation in the tissue and to possible hormonal influences.

Relationship between goblet cell density and tear function tests

AIM

The objective of this study was to find a relationship between goblet cell density (GCD) and other diagnostic tests of dry eye in a group of normal healthy Chinese subjects. The capability of using GCD as a tear function test was assessed.

METHOD

A total of 42 optometry students with no contact lens wear history were recruited. Subjects were required to fill in a dry eye questionnaire. The non-invasive tear break-up time (NITBUT) of each subject was measured, followed by phenol red thread test (PRTT) and tear break-up time (TBUT) tests. Conjunctival epithelial cells from the inferior nasal bulbar conjunctiva were harvested by the impression cytology technique. The specimens collected were labelled and stained with PAS (Periodic Acid Schiff)-haematoxylin. The goblet cells and the conjunctival epithelial cells were counted under a light microscope of 100x magnification. Spearman's rho (rho) correlation test was used to analyse the relationship between GCD and the other tear function tests.

RESULTS

With a probability level of 0.0051 (corrected for a cumulative familywise error rate of p = 0.05), GCD was found to have no correlation with NITBUT (rho = -0.193, p = 0.222), McMonnies Dry Eye Scores (MCDES) (rho = -0.052, p = 0.742), PRTT (rho = - 0.188, p = 0.234) and TBUT (rho = 0.246, p = 0.117).

CONCLUSION

There was no correlation between GCD and MCDES, NITBUT, PRTT and TBUT. The GCD alone is not a useful diagnostic test for tear film instability in normal eyes although it is a good indicator in the diagnosis of ocular surface diseases.

Evaluation of a mucoadhesive tablet for ocular use

The present study investigates the use of a polymer mixture containing Carbopol 974P and drum dried waxy maize starch to obtain prolonged drug release to the anterior eye segment. Two dosage forms with this composition are compared: a hydrated polymer dispersion and a minitablet. A model fluorescent tracer is used to study the ocular release and diffusion from the two dosage forms in humans. To evaluate the prolongation in the cornea/tearfilm compartment, the Apparent Fluorescein TurnOver (%/min) is calculated. The parameters Cmax, tmax, and C9h are used to characterize the pharmacokinetics of Na-fluorescein in the anterior chamber. Furthermore, the swelling behavior of the minitablet is evaluated macroscopically, while the degree of interaction with mucin is characterized by rheological measurements. Calculation of an acceptability score and a slug irritation potential is performed to evaluate user acceptability. In contrast to the hydrated dispersion, the minitablet significantly decreases the Apparent Fluorescein TurnOver (%/min) (P<0.05) and increases the apparent fluorescence in the anterior chamber 9 h after application of the preparation. Rheological data demonstrate the presence of elastic interactions between the polymer and mucin. The dry core of the minitablet becomes fully hydrated after approximately 2 h and is subsequently transformed into a highly concentrated gel. The acceptability of the minitablet is comparable to that of the polymer dispersion. Prolonging the release of Na-fluorescein to the anterior eye segment is only feasible with the dry preparation.

The conjunctival epithelium in dry eye subtypes: effect of preserved and non-preserved topical treatments

PURPOSE

To determine the effect of topical treatments on the conjunctiva in dry eye.

METHODS

N = 134 dry eye subjects were diagnosed using a protocol of McMonnies dry eye symptom survey score > 14, fluorescein break up time (FBUT) < 10 s and presence of rose Bengal staining. Differential diagnosis of dry eye subtypes was based on biomicroscopic signs and ocular/medical history. Superficial perilimbal bulbar conjunctival epithelial samples were collected using impression cytology. The nucleo-cytoplasmic ratio (N/C), goblet cell density (GCD) and expression of monoclonal antibodies HLA DR and CD23 were determined. The ocular surface characteristics of untreated subjects, those receiving preserved dry eye treatments and those receiving non-preserved treatments were compared with each other and with controls. Ocular surface characteristics of dry eye subtypes were also examined.

RESULTS

An increase in N/C (p = 0.011), reduction in GCD (p = 0.0001) and increase in expression of HLA DR (p = 0.0001) and CD23 (p = 0.0001) were detected in the untreated group compared to controls. No significant differences were found between the group receiving non-preserved dry eye treatments and untreated dry eye group. The group receiving preserved treatments had a reduced GCD (p = 0.0003) and increased expression of HLA DR (p = 0.0003) and CD23 (p = 0.0001) compared to the group receiving non-preserved treatments. Dry eye subtype specific differences in HLA DR and CD23 expression were noted.

CONCLUSIONS

The conjunctival inflammation and reduced goblet cell density of dry eye is exacerbated by use of preserved topical agents, and is not significantly improved by use of non-preserved artificial tear supplements alone. Therapeutic strategies for dry eye should aim to increase goblet cell density and control ocular surface inflammation.

The ratio of albumin to lactoferrin in tear fluid as a diagnostic tool in primary Sjögren's syndrome

PURPOSE

To compare the protein composition of tear fluid obtained from patients with primary Sjögren's syndrome, patients with other connective tissue diseases and control individuals.

METHODS

SDS polyacrylamide gel electrophoresis followed by staining with Coomassie blue and Western blotting.

RESULTS

Comparison revealed the presence of a characteristic difference in the ratio of intensity between the albumin and lactoferrin bands. An albumin:lactoferrin ratio above 2:1 was significantly more common in patients with primary Sjögren's syndrome than in patients with other connective tissue diseases or the controls.

CONCLUSION

An albumin:lactoferrin ratio above 2:1 may therefore prove of use when diagnosing 1(0)SS. Used as a test, its sensitivity was 67% and its specificity 100%.

Dry eye with only decreased tear break-up time is sometimes associated with allergic conjunctivitis

PURPOSE

The authors' clinical experience has suggested that there is a form of dry eye with only decreased tear break-up time, which is associated with allergic conjunctivitis. The current study was performed to verify this hypothesis.

METHOD

The authors recruited patients with two types of dry eye syndrome, those with only decreased tear break-up (BUT type) and those with positive vital staining (staining type). Individuals without any symptoms or signs served as controls. All subjects were compared regarding symptoms, Schirmer and tear clearance test results, conjunctival papillary formation, antigen-specific serum-IgE level (s-IgE), and goblet cell density of the palpebral conjunctiva. Antigen-induced allergic conjunctivitis was produced in guinea pigs, and histopathologic changes of the conjunctiva were examined.

RESULTS

Patients with the BUT-type dry eye syndrome were younger and their symptoms were as severe as the staining type. The Schirmer and tear clearance test results were better, and the papillary formation and s-IgE were observed more than in the BUT type. The average goblet cell density in the BUT-type syndrome was 625.4 +/- 193.2/mm2, which was significantly less than 1005.6 +/- 294.5/mm2 in the controls (P < 0.01). The average goblet cell density was significantly decreased in the allergic animals (10.40 +/- 1.11/0.2 mm) compared with that of the controls (16.21 +/- 0.26/0.2 mm) or the anti-allergic drug-treated group (13.69 +/- 0.30/0.2 mm) (P < 0.01).

CONCLUSION

These results support the authors' hypothesis that decreased break-up time is in part associated with the decreased goblet cell density caused by allergic conjunctivitis.

The normal human tear glycoprotein profile detected with lectin probes

Tear samples were collected from 46 healthy volunteers evenly distributed according to sex and age (mean age 43.5 years). Samples were denatured in a Tris-HCl sample buffer containing 2-mercaptoethanol and SDS, and applied to a gradient SDS-polyacrylamide gel for electrophoresis. The proteinaceous material was transferred to nitrocellulose by a semi-dry blotting technique, and the glycoprotein content subsequently visualized by incubation with four lectins (WGA, PHA, PSA and SBA) and staining with avidin horseradish-peroxidase. Glycoprotein bands were generally found to be significantly less frequent in persons under the age of 30 years. Apart from this the technique gave a uniform picture of the glycoprotein profile, with only modest differences according to age and/or sex. The technique may therefore be suitable for the detection of differences in the glycoprotein composition indicative of disease.

Measurement of wettability of the corneal epithelium. II. Contact angle method

Adult rabbit corneas were saline-rinsed, mucolytic-rinsed, or wiped to remove mucus. The corneas were allowed to dry in air; sessile droplets of saline were placed on the surface at various drying times, and their equilibrium contact angle theta measured. Several stages of drying can be distinguished: 1) an initial period when excess water is present, with either complete spreading of droplets or very low value of theta; 2) a 'plateau' region lasting about 20-25 min in which theta is low and changes slowly with time, and reflects the intrinsic wettability of the surface; 3) a region when more severe drying takes place and theta rises sharply. Computed tables are used with known values of theta and the surface tension of the saline drops, to give the surface tension of the corneal surface and the interfacial tension between cornea and saline. Acetylcysteine-washed corneas showed a plateau value of about 16 degrees and corneal surface tension of 69.3 mN/m. Rinsed corneas remained fully wettable (theta = 0 degrees) for longer than 90 min; hence the plateau value must also be near zero and corneal surface tension about 72 mN/m. Mechanically-wiped corneas dried more rapidly and theta rose continuously with no marked plateau value, indicating much lower wettability due to cellular damage (about 40 mN/m).

Lectin-binding sites in the anterior segment of the human eye

The anterior segment of the human eye was screened for differences in the lectin-binding patterns of Con A, PNA, GS-I, WGA, SBA, DBA, and UEA-I to enable cell typing for cell-culture purposes. An immunohistochemical technique combining an indirect antibody-lectin method with the avidin-biotin system was used. Con A and WGA were bound by all cells except the conjunctival goblet cells. UEA-I was exclusively bound by both vascular endothelial cells and some corneal and conjunctival epithelial cells. The binding of GS-I, PNA, SBA, and DBA showed an uneven pattern and differed among the cases investigated. The reasons for these differences are not clear. Our results indicate that the usefulness of lectins for cell-typing purposes is restricted and must be determined for every case.