Confocal biomicroscopic changes of the corneal layers following MyoRing implantation with corneal collagen crosslinking in keratoconus

Purpose. To study morphological changes in the cornea by confocal microscopy of simultaneous MyoRing implantation with corneal crosslinking in patients with keratoconus. Material and methods. The clinical study included 15 patients (16 eyes) with progressive keratoconus. All patients underwent a combination treatment: implantation of MyoRing intrastromal corneal rings (Dioptex GmBH, Linz, Austria) in combination with corneal crosslinking. The number of cells and quality indicators in each layer of the cornea were compared before and during 36 months after surgery. Results. Qualitative analysis of the cornea showed transient disturbances of the subepithelial nerve plexus, an increase in the reflectivity of stromal keratocytes, and moderate fibroplasia in the middle parts of the stroma in the area of the intrastromal pocket. During the follow-up period of 12 months or more after surgery, no significant changes in the corneal ultrastructure were detected in the dynamics. There was no significant decrease in endothelial cell density in the postoperative period. Conclusion. Analysis of morphological changes confirms the safety of a combination of simultaneous implantation of the MyoRing intrastromal ring and corneal crosslinking in stage II-III keratoconus by confocal microscopy and allows dynamic observation of changes in the corneal structure during intrastromal surgery. Key words: keratoconus, confocal microscopy, intrastromal corneal rings, MyoRing, corneal crosslinking.

Embryonic quail eye development in microgravity

The US-Russian joint quail embryo project was designed to study the effects of microgravity on development of Japanese quail embryos incubated aboard Mir. For this part of the project, eyes from embryonic days 14 and 16 (E14 and E16) flight embryos were compared with eyes from several groups of ground-based control embryos. Measurements were recorded for eye weights; eye, corneal, and scleral ring diameters; and numbers of bones in scleral ossicle rings. Transparency of E16 corneas was documented, and immunohistochemical staining was performed to observe corneal innervation. In addition, corneal ultrastructure was observed at the electron microscopic level. Except for corneal diameter of E16 flight embryos, compared with that of one of the sets of controls, results reported here indicate that eye development occurred normally in microgravity. Fixation by cracking the shell and placing the egg in paraformaldehyde solution did not adequately preserve corneal nerves or cellular ultrastructure.

Corneal ultrastructure after excimer laser keratectomy

The Argon fluoride excimer laser emits light at 193nm. At a fluence of 500mJ/CM2, one micron of organic tissue should be removed. This removal occurs by the disruption of chemical bonds rather than the normal heat vaporization seen with other types of lasers. These characteristics should allow the use of this laser in performing precise removal of superficial corneal scars and opacities as well as inducing changes in corneal curvature for refractive corrections. In our studies we will report the ultrastructural changes induced in both primates and man following excimer laser treatment.Following excimer laser treatment, the primates were followed for two years and the corneas removed for morphological studies. The human specimens were taken at various times after excimer treatment for clinical reasons, all having to do with unfavorable outcomes. All human specimens were taken at the time of transplantation of a new cornea to these eyes. The specimens were fixed with 2% paraformaldehyde and 2% gluderaldehyde in cacodylate buffer at pH 7.3. After fixation, these specimens were dehydrated, imbedded in Spurr epoxy resin, then sectioned and examined ultrastructurally.