Epithelial response in penetrating keratoplasty.

In 30 patients who were followed up, discrete corneal epithelial dots developed in a strictly confined area of the peripheral donor cornea within two months after penetrating keratoplasty. The incidence was higher, although not statistically significant, in the disparate group (55%) as compared to the isometric group (30%). The change in dot density that occurs after nylon suture removal is consistent with the idea of lateral cell movement in the corneal epithelium. This study confirms that donor epithelium persists for long periods of time.

Atraumatic transfer of the donor corneal button.

PURPOSE: To devise a method for atraumatic transfer of the donor corneal button by using a corneal shovel. METHOD: The donor cornea is lifted with a microcorneal shovel, and the epithelial surface dried with a microsponge applied to the corneal shovel to create a seal. This allows the shovel to be rotated through 180 degrees over the host eye with no movement of the donor cornea. The seal is then broken by applying a drop(s) of fluid onto the epithelial surface of the donor cornea or by touching the edge of the donor cornea to the edge of the host cornea. The donor cornea then slides or is floated onto the host eye. RESULTS: This technique has been performed on 52 corneal transplants with no complications such as slippage or falling off of the donor corneal button during transfer. CONCLUSION: This method provides a useful atraumatic surgical procedure for stabilising and transferring the donor cornea during corneal transplantation.

Developmental differences in visual processing: strategy versus structure.

The present study was an examination of two contrasting explanations for the finding that young children tend to classify objects according to similarity relations whereas adults emphasize dimensional structure. Subjects from three different age groups were given tasks that tapped different aspects of the visual process: Feature search, Conjunction search, and Restricted Classification tasks. In addition, three different stimulus objects (a highly separable, a highly integral, and an intermediate dimensional combination) were studied to explore the contribution of stimulus structure in dictating the nature of the processing mode. The results provided evidence against the view that children perceive objects according to a more primitive holistic structure. Rather, the results can be taken with past research to suggest that less efficient visual processing may lead the younger subjects to adopt a classification strategy that emphasizes similarity relations. In addition, the current research supported Garner's (1974, The processing of information and structure, Potomac, MD: Erlbaum) suggestion that the nature of the processing mode is stimulus-driven.