APPLANATION TONOMETRY AND CENTRAL CORNEAL THICKNESS

Readings with the Goldmann applanation tonometer were made at various intraocular hydrostatic pressures and compared with central corneal thickness and radius in rabbit and in man. Linear correlations were established between hydrostatic pressure and applanation readings, with correlation coefficients close to 1.0. In rabbits the tonometer readings were generally too low. [1]

Corneal response to orthokeratology.

PURPOSE:The technique of orthokeratology produces a corneal response to the mechanical pressures exerted by rigid contact lenses. This paper reports a study which investigated the topographic and pachometric corneal changes induced by orthokeratology. METHODS:Six young myopic subjects (11 eyes) wore “accelerated orthokeratology” lenses (OK-74; Contex Inc., Sherman Oaks, CA) in a high Dk material (AirPerm; Dk = 88) for 28 days. Corneal and epithelial thickness were measured topographically using the Holden-Payor optical micropachometer, and corneal topography was monitored using the EyeSys system. RESULTS:Refractive error change reached 1.71 +/- 0.59 D reduction in myopia after 28 days. After 1 day of lens wear, statistically significant central corneal flattening was noted, which progressed to reach 0.22 +/- 0.07 mm (1.19 +/- 0.38 D) at 28 days. [2]

Corneal nerves: structure, contents and function

This review provides a comprehensive analysis of the structure, neurochemical content, and functions of corneal nerves, with special emphasis on human corneal nerves. A revised interpretation of human corneal nerve architecture is presented based on recent observations obtained by in vivo confocal microscopy (IVCM), immunohistochemistry, and ultrastructural analyses of serial-sectioned human corneas. Current data on the neurotransmitter and neuropeptide contents of corneal nerves are discussed, as are the mechanisms by which corneal neurochemicals and associated neurotrophins modulate corneal physiology, homeostasis and wound healing. [3]

Photochemical Kinetic Modeling for Oxygen-enhanced UV-light-activated Corneal Collagen Crosslinking

Aims: To derive analytic formulas for the efficacy of type-II corneal collagen crosslinking (CXL) based on coupled macroscopic kinetic equations with an emphasis on the role of oxygen.Study Design: modeling and analysis of type-II CXL Place and Duration of Study: Taipei, Taiwan, between Feb. and June 2017. Methodology: Coupled macroscopic kinetic equations are derived under the quasi-steady state condition. For type-I CXL, the riboflavin triplet state [RF3] interacts directly with the stroma collagen substrate for crosslinking. For type-II process, [RF3] interacts with the ground-state oxygen [O2] to form a reactive oxygen singlet (ROS) which can relax to [O2], or interact with the extracellular matrix for crosslinking. [4]

Corneal Thinning and Opacity following Selective Laser Trabeculoplasty: A Case Report

Aims: Selective laser trabeculoplasty (SLT) (Lumenis, Santa Clara, CA) was developed in 1999 as a means to lower IOP in patients with glaucoma. It is a relatively safe procedure. We report a rare side effect of corneal opacity and stromal haze with corneal thinning and hyperopic shift following SLT.

Presentation of Case: Case report.

Results: A 50 year-old Asian male who underwent SLT OD developed mild corneal edema and slightly elevated intraocular pressure (IOP) one day after procedure. He was prescribed anti-inflammatory drops. One week afterwards, he developed a small corneal abrasion centrally. He was given topical antibiotics and asked to continue anti-inflammatory drops. On postoperative day 8, his corneal abrasion healed, but he developed stromal corneal haze. Topical steroids were begun. By postoperative week #2, his visual acuity and stromal haze had improved. His corneal thickness decreased from 600 µms to 468 µms. After one year, he had almost complete resolution of his corneal pathology but had residual corneal thinning and flattening. [5]

Reference

[1]  Ehlers, N., Bramsen, T. and Sperling, S., 1975. Applanation tonometry and central corneal thickness. Acta ophthalmologica53(1), pp.34-43.

[2] Swarbrick, H.A., Wong, G. and O’Leary, D.J., 1998. Corneal response to orthokeratology. Optometry and vision science: official publication of the American Academy of Optometry, 75(11), pp.791-799.

[3] Müller, L.J., Marfurt, C.F., Kruse, F. and Tervo, T.M., 2003. Corneal nerves: structure, contents and function. Experimental eye research76(5), pp.521-542.

[4] Lin, J.T., 2017. Photochemical kinetic modeling for oxygen-enhanced UV-light-activated corneal collagen crosslinking. Ophthalmology Research: An International Journal, pp.1-8.

[5] Song, J., Yu, D., Song, A., Palmares, T., Song, H.S. and Song, M., 2014. Corneal thinning and opacity following selective laser trabeculoplasty: a case report. Journal of Advances in Medicine and Medical Research, pp.279-287.

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