Biomedical subjects
Ivan R Schwab
Publications and source records attributed to Ivan R Schwab.
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Evolution of the tapetum.
PURPOSE: To review, contrast, and compare current known tapetal mechanisms and review the implications for the evolution of the tapetum. METHODS: Ocular specimens of representative fish in key piscine families, including Acipenseridae, Cyprinidae, Chacidae; the reptilian family Crocodylidae; the mammalian family Felidae; and the Lepidopteran family Sphingidae were reviewed and compared histologically. All known varieties of tapeta were examined and classified and compared to the known cladogram representing the evolution of each specific family. RESULTS: Types of tapeta include tapetum cellulosum, tapetum fibrosum, retinal tapetum, invertebrate pigmented tapetum, and invertebrate thin-film tapetum. All but the invertebrate pigmented tapetum were examined histologically. Review of the evolutionary cladogram and comparison with known tapeta suggest that the tapetum evolved in the Devonian period 345 to 395 million years ago. Tapeta developed independently in at least three separate orders in invertebrates and vertebrates, and yet all have surprisingly similar mechanisms of light reflection, including thin-film interference, diffusely reflecting tapeta, Mie scattering, Rayleigh scattering, and perhaps orthogonal retroreflection. CONCLUSION: Tapeta are found in invertebrates and vertebrates and display different physical mechanisms of reflection. Each tapetum reflects the wavelengths most relevant to the species' ecological niche. With this work, we have hypothesized that the tapetum evolved independently in both invertebrates and vertebrates as early as the Devonian period and coincided with an explosion of life forms.
Corneal perforation during laser blepharoplasty.
A 61-year-old woman presented with photophobia, pain, epiphora, and decreased vision as a result of two iatrogenic corneal perforations sustained during carbon dioxide laser blepharoplasty. The management and course of the case are outlined. Laser blepharoplasty complications are reviewed. This case highlights the potential occurrence of corneal penetration with laser blepharoplasty. Meticulous awareness of the laser effects on periocular tissue must be kept in mind at all times during laser blepharoplasty to avoid unnecessary intraocular side effects and undesirable postoperative outcomes.