Assessment of Goblet Cell Orifice Distribution Across the Rabbit Bulbar Conjunctiva Based on Numerical Density and Nearest Neighbors Analysis

Abstract

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 μm²; group mean +/− SD of 54 +/− 36 μm²), and distribution of orifice areas was skewed or even bimodal. The overall orifice density was 387 +/− 68/mm², 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.

• Bulbar conjunctiva
• goblet cell orifices
• nearest neighbors analysis
• rabbit
• scanning electron microscopy