Structural influences such as the "black line" or corneal lid defects appeared to influence the recurrence of breakup in the same region. The S-TBUD quantitative image analysis technique demonstrates that the tear film of subjects with dry eye continues to rapidly destabilize after an initial first break; thus, a low TBUT was combined with a high DAGR. The central corneal region of subjects with dry eye appeared especially susceptible to increased tear breakup when compared with controls.

1. We report here a psychophysical technique for studying the spectral sensitivity of jumping spiders (family Salticidae), based on a newly discovered oculomotor reflex. 2. Our results, obtained from Maevia inclemens (Salticidae), are compatible with electrophysiological findings of retinal cells maximally sensitive in the green and ultraviolet regions of the spectrum. 3. Sensitivity to longer wavelengths (greater than 650 nm) has been controversial. In our study jumping spiders are shown to have a broad spectral sensitivity function extending from the ultraviolet (330 nm) to the deep red (700 nm).

The swelling properties of the anterior and posterior stroma of bovine and rabbit corneas were examined by three different methods. The results show that the posterior stroma can swell more than the anterior stroma. Also, at a given swelling pressure, the posterior stroma is more hydrated than the anterior stroma. In a third experiment it is demonstrated that the posterior stroma is also more hydrated in the living eye. It is concluded that the stroma is not a homogeneous structure. The superficial stroma has different physiological properties from the deep stroma. These differences must be taken into account in theoretical models of corneal deturgescence.

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The overall 24-h and 30-day anesthesia-related and in-hospital perioperative mortality rates in our study are comparable with other similar studies from tertiary pediatric centers.

ABSTRACT.Purpose: During blinking the lids apply a shear force to the corneal epithelium. The aim of this study was to determine if a shear force applied to the epithelial surface increases the rate at which cells shed. Methods: The shedding rate was studied in perfused whole rabbit eyes, and the effect of a shear force examined by exposing the corneas to a stirred solution. Control corneas were exposed to a static solution. The shedding rate and size of shed cells were measured, and the number of terminally differentiated cells on the corneal surface determined after 6 h of perfusion using ethidium bromide. Results: Compared with controls, the shear force increased the cell shedding rate from the corneal surface significantly (p < 0.01, paired t-test). The increase was due to small cells with a longest dimension less than 25 pm. The number of terminally differentiated cells on the epithelial surface did not increase. Conclusiom Because of the decrease in size, and the change in appearance of shedding cells, it is proposed that the increase in cell shedding rate was due to an increase in the number of apoptotic cells, and not to an increase in terminally differentiated cells. It is suggested that in the human eye, under adverse conditions, shear forces due to blinking may play a role in creating apoptotic cells.

The results suggest that the spontaneous cell shedding rate of the in vivo rabbit corneal epithelium is 5 to 15 cells/min/cornea. This is much lower than estimates of about 100 cells/min/cornea based upon in vitro corneal superfusion. One explanation of this slow shedding rate is that factors which were absent during our collection methods (such as blinking) would normally increase shedding. Another possibility is that cells in the corneal epithelium may have a much longer life span than previously reported; rather than a few days, the epithelium could take several months to completely replace all cells. Whatever the explanation, the measured spontaneous shedding rate does not complement the reported production rate of new cells. It is necessary to revise our understanding of the kinetics of epithelial homeostasis.

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