Abstract
Purpose: :
The moderately dry eye is difficult to diagnose, in part, because it is not known what pathological microscopic ocular surface changes have occurred leading to reported symptomology. The dry eye mouse model was chosen to define such structural alterations induced by the dry eye condition.
Methods: :
Twelve C57BL/6 mice, 6 normal and in 6 ocular dryness was induced by administration of scopolamine hydrobromide (0.5mg/0.2ml) QID, and exposure to a dry environment for 5 (n=3) and 10 (n=3) days. The lids were fixed in 2% glutaraldehyde and processed for histology using an established protocol. Thick sections with palpebral conjunctiva were stained with 1% toluidine blue and viewed with an Olympus IX70 microscope. The palpebral epithelial measurements were obtained using NIH Image 1.63 and the number of goblet cells assessed based on histological criteria and their location.
Results: :
The epithelium near the lid margin is stratified and lacks goblet cells. Over the next 411.1 ± 73.3µm the epithelium gradually tapers down from 8 to 3-4 layers of cells and goblet cells become present. In this region, the control epithelium averaged 23.2 ± 3.4µm and was significantly (P<0.05) thicker than the 5 day (17.0 ± 3.4µm) and the 10 day (17.8 ± 2.6µm). The control averaged 19.3 ± 8.5 goblet cells versus 28.3 ± 18.9 for the 5 day and 25.0 ± 4.4 for the 10 day. No significance (P>0.05) was found between the groups in this respect. However, in the normal, 36% of the goblet cells had an epithelial coverage, compared to 54% for the 5 day and 56% for the 10 day.
Conclusions: :
This study showed that the mouse stratified palpebral conjunctival epithelium becomes significantly thinner in experimentally dry eye. The density of goblet cells did not change, but ocular surface access for goblet cells appeared inhibited by surrounding epithelial cells, which may in this manner slow down the progress of goblet cells towards the palpebral surface.
Keywords: conjunctiva • eyelid • microscopy: electron microscopy