Corneal Curvature Stability With Increased Intraocular Pressure

Abstract

Corneal shape and refraction were found to show only minor evidence of instability under conditions of IOP loading. The small number and minor degree of corneal changes recorded under IOP loading suggest that under these conditions of measurement, corneal stability may be the result of stress stiffening. However, mechanisms for corneal shape changes that depend on limbal and scleral rigidity may also contribute to corneal shape stability.

Abnormal Rubbing and Keratectasia

“…For example, the distal end of the subject's index finger was used to apply firm force to the eye through the skin adjacent to the lateral canthus, approximately 8 to 10 mm posterior to the temporal limbus. 57 IOP was increased from 18 to 56 mm Hg for one subject and from 12 to 62 mm Hg for the other. 57 An IOP of 50 to 110 mm Hg was recorded with tight-squeeze blinking.…”

Epithelial Responses to Rubbing-Related Mechanical Forces

“…4,5 IOP spikes are associated with corneal stress stiffening. 28 As discussed below, rubbing involves the combination of rubbing compression force that squeezes the epithelium against the anterior stroma. However, the anterior stroma is stress-stiffened by the distending force of the IOP spike induced by the combination of rubbing and eye closure.…”

“…Digital pressure on the eye through the adnexal skin was found to spike IOP by 50%-130% when the touch was light and by 200%-400% when the touch was firm. 28 Those IOP spikes were recorded with eyes open. However, strong eye closure spikes IOP from 50 to 110 mm Hg.…”

Eye Rubbing and Keratoconus: A Literature Review

“…60 Gentle and firm eye rubbing are able to temporarily increase the IOP two, and four fold respectively. 61 Massaging of a rabbit eye in vivo has produced an IOP of 150 mm Hg, although, whether this level would be possible in humans is difficult to establish. 62 These rubbing forces causing IOP fluctuation secondary to indention of the cornea are likely to be associated with corneal curvature transfer and development or progression of keratoconus.…”