Purpose. To investigate static upper eyelid pressure and contact with the ocular surface in a group of young adult subjects. Methods. Static upper eyelid pressure was measured for 11 subjects using a piezoresistive pressure sensor attached to a rigid contact lens. Measures of eyelid pressure were derived from an active pressure cell (1.14-mm square) beneath the central upper eyelid margin. To investigate the contact region between the upper eyelid and the ocular surface, the authors used pressure-sensitive paper and the lissamine-green staining of Marx's line. These measures, combined with the pressure sensor readings, were used to derive estimates of eyelid pressure. Results. The mean contact width between the eyelids and the ocular surface estimated using pressure-sensitive paper was 0.60 +/- 0.16 mm, whereas the mean width of Marx's line was 0.09 +/- 0.02 mm. The mean central upper eyelid pressure was calculated to be 3.8 +/- 0.7 mm Hg (assuming that the whole pressure cell was loaded), 8.0 +/- 3.4 mm Hg (derived using the pressure-sensitive paper imprint widths), and 55 +/- 26 mm Hg (based on contact widths equivalent to Marx's line). Conclusions. The pressure-sensitive paper measurements suggested that a band of the eyelid margin, significantly larger than the anatomic zone of the eyelid margin known as Marx's line, had primary contact with the ocular surface. Using these measurements as the contact between the eyelid margin and the ocular surface, the authors believe that the mean pressure of 8.0 +/- 3.4 mm Hg is the most reliable estimate of static upper eyelid pressure.

Analysis of the corneal topographic changes gives insight into the pressure applied by the upper and lower eyelids in different situations. These include greater upper eyelid pressure with increasing downward gaze and greater lower eyelid pressure compared with the upper eyelid in 40-degree downward gaze. There was some evidence that supports Marx line as the primary site of contact between the eyelid margins and the cornea.

The pressure of the eyelids on the cornea in short-term downward gaze resulted in optically and clinically relevant corneal changes. Correlation between the refractive corneal changes and eyelid parameters suggests that the angle, shape, and position of the eyelids influence the nature of the corneal changes. When high accuracy is required, refraction should be qualified by the visual tasks undertaken before assessment.

In this preliminary study, we have shown that soft contact lenses can produce small but significant changes in the morphology of the limbal/scleral region and that OCT technology is useful in assessing these changes. The clinical significance of these changes is yet to be determined.

PURPOSE:To investigate changes in tear film surface quality after commencing soft contact lens wear. METHODS: Tear film surface quality (TSQ) was assessed during the interblink period using dynamic videokeratoscopy at 25 Hz. A quantitative value of TSQ is derived for each raw Placido ring image. Eleven young subjects with normal tear characteristics participated in the study. Dynamic videokeratoscopy was taken three times per day; in the morning, at lunchtime, and in the afternoon. This was done on two baseline days (bare eye) and on the first and seventh days of lens wear for a conventional hydrogel lens and following a week of no lens wear, for a further week of silicone hydrogel lens wear. Additionally clinical tests to assess TSQ were conducted and subjects were also asked to rate the subjective dryness of their eyes. RESULTS: All lens wear measurements showed a significant worsening of TSQ compared to bare eye measurements (repeated measures ANOVA, P<0.01). A significant diurnal change was found on the first day of silicone hydrogel contact lens wear, where TSQ improved during the day (P=0.045). However, no diurnal changes were found in TSQ for the other lens wearing days or for the bare eye condition (P>0.05). The subjective rating of dryness correlated with TSQ values (Pearson's r=0.62, P<0.05) for the bare eye condition, but not during contact lens wear. TSQ derived from the right and left bare eyes of the same individuals showed a significant correlation (Pearson's r=0.61, P<0.05). CONCLUSIONS: The measurement of TSQ using dynamic videokeratoscopy differentiates between bare eye and lens wearing conditions. It also shows a small systematic improvement in tear surface quality during the first day of silicone hydrogel lens wear and a significant association with subjective dryness for the bare eye condition. (J Optom 2008;1:14-21 ©2008 Spanish Council of Optometrists) KEY WORDS: high speed videokeratoscopy; tear film; dry eye; contact lens. RESUMEN OBJETIVO:Investigar los cambios en la calidad de la superficie de la película lagrimal tras empezar a utilizar lentes de contacto blandas. MÉTODOS: Se evaluó la calidad de la superficie de la película lagrimal (CSPL) durante el periodo comprendido entre dos parpadeos consecutivos utilizando videoqueratoscopia (topografía corneal estándar) dinámica a 25 Hz. Para cada imagen registrada de los anillos de Plácido se derivó un valor cuantitativo de la CSPL. En el estudio participaron once sujetos jóvenes cuya lágrima presentaba características normales. Se realizaron medidas de videoqueratoscopia dinámica tres veces al día: por la mañana, a la hora de comer y por la tarde. Estas medidas se llevaron a cabo primero, en dos días distintos, para recabar datos de referencia (ojo desnudo, sin lente de contacto); posteriormente, el primer y el séptimo día de uso de una lente de contacto convencional de hidrogel y finalmente, y tras una semana sin utilizar lentes, se realizaron medidas el primer y el séptimo día de uso de una lente de hidrogel de silicona. De maner...