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Purpose To examine the effect of a short pause in blinking on the quantitative topographic parameters of the corneal surface. Setting Refractive corneal surgery unit of a university eye hospital. Methods Using a TMS-1 instrument (Computed Anatomy, Inc.), corneal topographic parameters were measured 5 and 15 seconds after a complete blink in 12 healthy subjects. The main outcome measures were changes in the surface regularity index (SRI) and the surface asymmetry index (SAI). Results During the pause in blinking, the mean SRI value increased from 0.18 ± 0.19 (SD) to 0.30 ± 0.19 ( P P = .079, not statistically significant). There were no significant changes in the values for potential visual acuity, corneal refractive power, or astigmatism. Conclusion The results indicated a significant change in corneal topography during even a short pause in blinking. In follow-up studies using corneal topography, all measurements should be done at a fixed time after a complete blink.

Our topography system is an enhancement of a standard TMS-1 corneal topograph instrument (Computed Anatomy Inc., New York, NY, USA). Topographic images are captured at a rate of 4 s(-1), allowing the recording of a series of 120 images in 30 s after a complete blink. In this prospective preliminary study 15 healthy volunteers were examined. The main outcome measures were the time profile of changes in surface regularity index (SRI), surface asymmetry index (SAI) and simulated keratometry values (K1, K2). After a blink there was a tendency for improvement in ocular surface regularity. Later trends were less clear. Our topography system makes possible the detailed evaluation of tear-film dynamics in the post-blink period. The new technique may play an important role in the diagnosis of various tear-film abnormalities; the results may also have significant implications in the planning of refractive surgeries.

We carried out an investigation into the morphological and quantitative corneal properties in dry eye with various underlying pathologies. Ten patients with aqueous tear deficiency, 8 with dysthyroid ophthalmopathy, 8 with chronic lagophthalmos and 10 normal participants were examined. Confocal microscope images were taken at the centre and at the lower and upper periphery of the cornea. Quantitative and morphological assessments of the epithelium, of the sub-basal nerves, of the stroma and the endothelium were made. The epithelial and corneal thicknesses were measured. The mean superficial and intermediate epithelial cell densities in the central cornea in the patient groups were significantly lower than in normal participants (p

Purpose To assess whether the type of corneal topographic pattern is stable during a 1-minute pause in blinking in healthy subjects. Setting First Department of Ophthalmology, Semmelweis University, Budapest, Hungary. Methods Corneal topographic images were recorded 5, 15, 30, and 60 seconds after a complete blink in the right eyes of 36 healthy subjects using the TMS-1 instrument in a prospective observational study. The topographic pattern of each image was assessed from the color-coded topographic map and classified into 5 groups (in order of decreasing regularity: round, oval, symmetric bow-tie, asymmetric bow-tie, and irregular). Results During the 60-second period, a change in the type of topographic pattern was found in 19 subjects (53%), whereas in 17 subjects (47%) the pattern was stable. The alteration of the topographic pattern was statistically significant ( P Conclusions Immediately after blinking, the ocular surface regularity improves, possibly due to the building up of the tear film. This is followed later by the distortion of the ocular surface, which is the precursor of the tear-film break up phenomenon. Because of these changes, even in healthy eyes, the optimization and standardization of the postblink time of topographic image capture are very important, especially for planning refractive surgery.

To detect tear film regularity changes in the 15 seconds after a blink, by using a new high-speed videotopographic method.The new system, based on a standard corneal topograph, allows registration of four photokeratoscopic images per second. Altogether, 15 eyes of 15 healthy volunteers and 7 eyes of 7 patients with dry eye were examined in this prospective preliminary study. The main outcome measures were changes in surface regularity index (SRI), surface asymmetry index (SAI), and corneal power.The corneal surface became more regular in the first few seconds after a blink. In healthy eyes, the trend line of SRI and SAI decreased (improved) significantly (P0.001) after a blink, in 10 of 15 eyes for the SRI and in 13 of 15 for the SAI. In the typical cases, the trend line for SRI reached its minimum level, on average, at 7.1 +/- 3.9 seconds after a blink and that for the SAI at 5.4 +/- 2.7 seconds. Similar trends were found in the dry-eye group. The changes in keratometric measures were small (mean range,1.5% of the absolute value) and showed no definite trends.High-speed videotopography provides the possibility of quantitative measurement of tear-film dynamics and may have clinical value in the management of ocular surface disorders. After a blink, it takes the tear film approximately 3 to 10 seconds (tear film build-up time) to reach the most regular state. However, despite surface-regularity changes, the measured corneal powers are stable.