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

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.

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.

Biopsy of the conjunctiva in dry eye patients establishes a correlation between squamous metaplasia and dry eye clinical severity

PURPOSE

The aim of this work was to evaluate the different grades of squamous metaplasia of the conjunctiva during the clinical course of dry eye syndrome, detecting the most characteristic morphological and morphometric changes by biopsy in order to provide a diagnostic classification.

METHODS

The conjunctiva was studied under light microscopy by conventional histological methods and by morphometric analysis in 165 patients and in 33 controls. Patients were classified according to the Schirmer 1 test, break-up time, rose Bengal staining, osmolarity and impression cytology. The epithelium and connective tissue, with their different cells and other structures, were studied.

RESULTS

The conjunctiva in dry eye patients showed progressive stratification, hyperplasia, hypertrophy and cellular flattening, with loss of goblet cell density and mucous layer. We found five pathological grades of squamous metaplasia and one normal grade. Clear nuclear alterations (indentation and binucleation) were found in the early grades of dry eye syndrome, but pyknotic nuclei and anucleated cells were only seen in the most severe grades. The smallest epithelial cells were found in the control group and their size increased with the severity of the dry eye syndrome. From the earliest stages to the most severe cases, increases in cellular separation were observed. There was also an increase in the number of inflammatory cells. Blood and lymphatic vessels showed alterations only in the most severe cases.

CONCLUSIONS

This is the first grading system proposed for biopsy evaluation of the ocular surface in dry eye patients. These morphological and morphometric studies alone were able, even in the earliest phases of dry eye, 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 increases in the stratification, epithelial cellular size and a general loss of goblet cells.

Topical nonsteroidal anti-inflammatory drugs for ophthalmic use: a safety review

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used agents that despite chemically heterogeneity, share similar therapeutic properties and adverse effects. Topical ophthalmic NSAIDs are limited to the relatively water soluble phenylacetic and phenylalkanoic acids as well as indole derivatives, which are more suitable for ophthalmic use. Topical ophthalmic NSAIDs are commonly used in the treatment of post-operative inflammation following cataract extraction and various surgical refractive procedures. They are also used in the prevention and treatment of cystoid macular oedema and for the treatment of allergic conjunctivitis. Absorption of topical ophthalmic NSAIDs through the nasal mucosa results in systemic exposure and the occurrence of adverse systemic events, including exacerbation of bronchial asthma. Local irritant effects of topical ophthalmic NSAIDs include conjunctival hyperaemia, burning, stinging and corneal anaesthesia. A more serious complication involves the association of topical ophthalmic NSAIDs with indolent corneal ulceration and full-thickness corneal melts. Analysis of NSAID-associated corneal events implicates the now defunct generic dicolfenac product, diclofenac sodium ophthalmic solution as the agent primarily responsible. However, these events generated a renewed interest in the safety of ophthalmic NSAIDs and a scrutiny of the pharmacology regarding NSAID action in the eye. An elucidation of possible pharmacodynamic explanations of NSAID-induced corneal injury includes the role of epithelial hypoxia, which not only appears to aid in determining the metabolic destination of arachidonate, it may play a key role in orchestrating a novel inflammatory response unrelated to prostanoid formation. The use of NSAIDs under conditions of corneal hypoxia may therefore not only result in a disappointing therapeutic response, it may result in a paradoxical inflammatory exacerbation. Other potential mechanisms include the relationship between NSAIDs and corneal matrix metalloproteinase and direct toxicity due to cytotoxic excipients such as surfactants, solubilisers and preservatives found in topical NSAID ophthalmic preparations. In general, ophthalmic NSAIDs may be used safely with other ophthalmic pharmaceuticals; however, concurrent use of agents known to adversely effect the corneal epithelium, such as gentamicin, may lead to increased corneal penetration of the NSAID. The concurrent use of NSAIDs with topical corticosteorids in the face of significant pre-existing corneal inflammation has been identified as a risk factor in precipitating corneal erosions and melts and should be undertaken with caution. Until clinical evidence dictates otherwise, data supporting theories of potential pharmacodynamic mechanisms of NSAID injury do not alter the favorable benefit-risk ratio of ophthalmic NSAID use when employed in an appropriate and judicious manner.

Increased expression of the type 1 growth factor receptor family in the conjunctival epithelium of patients with keratoconjunctivitis sicca

PURPOSE

To investigate the expression of type 1 growth factor receptors (epidermal growth factor receptor, ErbB2, and ErbB3) in the conjunctival epithelium of patients with keratoconjunctivitis sicca.

METHODS

Immunofluorescent staining and Western blotting were performed to grade the level of expression of the epidermal growth factor receptor ErbB2, and ErbB3 in conjunctival epithelial impression cytologies taken from both eyes of seven normal subjects and 22 patients with keratoconjunctivitis sicca.

RESULTS

Epidermal growth factor receptor staining was observed in a greater percentage of keratoconjunctivitis sicca than normal samples (P <.05). ErbB2 and ErB3 staining in the apical conjunctival epithelium was observed in both groups, but stronger ErbB2 and ErbB3 staining was noted in keratoconjunctivitis sicca conjunctival samples (P <.05). The relative levels of expression of these receptor proteins on immunoblots were consistent with immunofluorescent staining. On immunoblots, epidermal growth factor receptor protein was detected in 50% of keratoconjunctivitis sicca samples, but none of the normal samples (P <.025). The expression of ErbB2 and ErbB3 on immunoblots was also greater in the keratoconjunctivitis sicca samples (P <.05). Immunofluorescent staining scores for these receptors were correlated with conjunctival lissamine green staining scores (r =. 574, P <.01 for epidermal growth factor receptor; r =.620, P <.0025 for ErbB2; r =.502, P <.025 for ErbB3) and with corneal fluorescein staining (r =.409, P <.05 for ErbB2; r =.588, P <.005 for ErbB3).

CONCLUSION

The expression of the type 1 growth factor receptors is significantly greater in the conjunctival epithelium of eyes with keratoconjunctivitis sicca than normal eyes. The increased expression of these receptors was positively correlated with ocular surface dye staining. The increased expression of these receptors may contribute to the abnormal growth and differentiation of the conjunctival epithelium that occurs in keratoconjunctivitis sicca.