Eyelid pressure: Inferences from corneal topographic changes

Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia.
Cornea (Impact Factor: 2.36). 02/2009; 28(2):181-8. DOI: 10.1097/ICO.0b013e31818a7d61
Source: PubMed

ABSTRACT It is known that eyelid pressure can influence the corneal surface. However, the distribution of eyelid pressure and the eyelid contact area and the biomechanics of the changes are unknown. Although these factors are difficult to directly measure, analysis of eyelid-induced corneal topographic changes and eyelid morphometry enables some inferences to be drawn.
Eighteen subjects, aged between 19 and 29 years, with normal ocular health were recruited. Corneal topographic changes were measured after 4 conditions consisting of 2 downward gaze angles (20 and 40 degrees) and 2 types of visual tasks (reading and steady fixation). Digital photography recorded the width of Marx line, the assumed region of primary eyelid contact with the cornea.
Significantly larger corneal changes were found after the 40-degree downward gaze conditions compared with 20-degree conditions because of the upper eyelid contact (P < 0.001). For the 40-degree downward gaze tasks, the lower eyelid changes were greater than those because of the upper eyelid (P < 0.01). The upper eyelid Marx line width was associated with the amplitude of corneal change (R = 0.32, P < 0.05).
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.

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Available from: Alyra Shaw, Jul 30, 2015
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    • "Using the calibration equation for a pressure cell assumes that the entire cell is loaded by the eyelid margin (i.e., over a width of more than 1.14 mm). Current evidence suggests that the area of primary contact between the upper eyelid and eye surface is likely to be less than 1 mm [3], [12]. Once the contact area between the cornea and upper eyelid has been confirmed, eyelid pressure measurements can be scaled based upon this contact area. "
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    ABSTRACT: In this paper, novel procedures were developed using a thin (0.17 mm) tactile piezoresistive pressure sensor mounted on a rigid contact lens to measure upper eyelid pressure. A hydrostatic calibration system was constructed, and the influence of conditioning (prestressing), drift (continued increasing response with a static load), and temperature variations on the response of the sensor were examined. To optimally position the sensor-contact lens combination under the upper eyelid margin, an in vivo measurement apparatus was constructed. Calibration gave a linear relationship between raw sensor output and actual pressure units for loads between 1 and 10 mmHg ( R <sup>2</sup> = 0.96 ). Conditioning the sensor prior to use regulated the measurement response, and sensor output stabilized about 10 s after loading. While sensor output drifts slightly over several hours, it was not significant beyond the measurement time of 1 min used for eyelid pressure. The error associated with calibrating at room temperature but measuring at ocular surface temperature led to a very small overestimation of pressure. Eyelid pressure readings were observed when the upper eyelid was placed on the sensor, and removed during a recording. When the eyelid pressure was increased by pulling the lids tighter against the eye, the readings from the sensor significantly increased.
    IEEE Transactions on Biomedical Engineering 11/2009; DOI:10.1109/TBME.2009.2022550 · 2.23 Impact Factor
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    ABSTRACT: 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.
    Investigative ophthalmology & visual science 10/2009; 51(4):1911-7. DOI:10.1167/iovs.09-4090 · 3.66 Impact Factor
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    ABSTRACT: To determine whether Marx's line of the upper lid is visible in upgaze without lid eversion, thus raising the possibility that the line may not be the contact area for the upper lid wiping of the ocular surfaces. Consecutive patients in a broad-spectrum practice were enrolled. Exclusion criteria included patients of Asian descent, active anterior segment pathology, obvious lid alterations or deformities, strabismus more than 20Delta. A 20-microL drop of 2% fluorescein was instilled into the lower eyelid conjunctival sac. The complete length of the upper lid margin, in upward fixation (approximately 45 degrees , with the eyes open), was examined for Marx's line. Sixty-eight males and 131 females were enrolled. The age range was 18 to 80 years; mean age = 51.7 +/- 14.3 years. Before eyelid eversion, Marx's line was visible in 99.0% of eyes and was visibly continuous for the entire eyelid margin length in 93.2% of eyes. Marx's line of the upper lid is visible in upgaze, without lid eversion, suggesting that is not the contact area for the upper lid wiping of the ocular surfaces in that position of gaze. Further research is required to determine the position and visibility of the line through all other lid positions during blinking.
    Eye & contact lens 03/2010; 36(3):149-51. DOI:10.1097/ICL.0b013e3181d9ee3c · 1.68 Impact Factor
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