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At least 631 records · Page 35Linked to original sources

Sutureless amniotic membrane fixation using fibrin glue for ocular surface reconstruction in a rabbit model.

PURPOSE: Amniotic membrane transplantation has become an important treatment option for corneal surface reconstruction. However, suture fixation of the transplant has various disadvantages like corneal irritation, scarring, graft loss due to membrane shrinkage, and the need for subsequent suture removal. Replacement of sutures by bioadhesives might be an advantageous alternative. This controlled study was designed to evaluate a new sutureless technique for amniotic membrane fixation onto the corneal surface by using fibrin glue. METHODS: Standardized disks of cryopreserved amniotic membranes were transplanted onto the deepithelialized cornea of 12 rabbits using either conventional suture fixation or a new fibrin glue technique. The rabbits were followed-up with slit-lamp examination and fluorescein staining until epithelialization was completed. Consecutively, the rabbits were killed and the eyes processed for histology and immunohistochemistry for cytokeratin-3. RESULTS: All membranes of both groups stayed in place throughout the follow-up time and showed a progressive graft epithelialization that was completed after 12 days. Whereas suture-fixated membranes showed progressive tissue shrinkage, fibrin-glued sheets remained unaltered. In the bioadhesive group, histology revealed a smooth fibrin layer in the graft-host interface and a continuous, stratified layer of cytokeratin-3 expressing corneal epithelial cells on the membrane surface. In contrast, suture-fixated membranes showed contracted and prominent membrane edges with epithelial ingrowth into the submembrane interface. CONCLUSION: Our results demonstrate the general feasibility of reproducible and reliable sutureless amniotic membrane fixation onto the corneal surface in rabbits. Stable adherence is maintained until epithelialization is completed. The sutureless technique gives sufficient manipulation time for the sheet before the final cross-linking process is completed. Furthermore, several advantageous characteristics could be demonstrated as increased biocompatibility, better epithelialization pattern and the lack of membrane shrinkage.

Amnion↗

The role of the corpus callosum in the development of interocular eye alignment and the organization of the visual field in the cat.

In young cats, the posterior portion of the corpus callosum was sectioned 13--29 days after birth. The animal's eyes were photographed at weekly intervals for six months using the pupil-reflex method. From the corneal reflection evident in the photographs the degree of alignment for the optical axes of each cat was estimated (Sherman, 1972). The 17 experimental cats all showed a significant tendency toward permanent divergent strabismus, as compared to six normal cats. The limits of the visual field were determined for both groups of cats using a perimetry technique similar to that of Sprague and Meikle (1965) and Sherman (1973). With one eye open normal cats responsed from 90 degrees ipsilateral to 45 degrees past the vertical midline into the contralateral visual field. With either eye the experimental cats responsed from 90 degrees ipsilateral to approximately the vertical midline. The loss of visual responsiveness is within the contralateral region of the normally binocular zone. Three cats received the same operation at 9, 13, or 20 months old. Eye alignment and visual field perimetry were unaffected by the surgery. It is not known whether the observed abnormalities result from arrested development, or disruption of intrinsically determined ocular alignment.

Animals↗

[The optostatic system and abnormal ocular movements].

The function of the oculomotor system is to assure gaze movements. Its equilibrium is essential to allows the stability of gaze, especially fixation. Therefore, an opto-static system is necessary to complete the kinetic organisation of eye movements. A disorder in this opto-static system produces abnormal eye movements. Their appearance depends on the location nd on the nature of the lesion in the opto-static system.

Cerebral Cortex↗

A clinical comparison of visual field testing with a new automated perimeter, the Humphrey Field Analyzer, and the Goldmann perimeter.

Automated threshold static perimetry with the Humphrey field analyzer and kinetic and suprathreshold static perimetry with the Goldmann perimeter were performed on 171 eyes: 69 with glaucoma or ocular hypertension, 69 with "neurologic" disorders, and 33 normal. The two fields were similar or differed only slightly in 78% of eyes overall and in 88% when both fields appeared reliable. In general, defects were slightly more extensive using the Humphrey than the Goldmann perimeter. In 21% of the eyes with glaucoma or ocular hypertension, defects were found with the Humphrey perimeter that were not present with the Goldmann perimeter. Patient fixation was more difficult to maintain on the Humphrey than Goldmann perimeter. Poor fixation accounted for 9% of the automated fields being inadequate whereas only 2% of the manual fields were inadequate. The results indicate that the Humphrey Field Analyzer is capable of reliably detecting and quantitating visual field defects.

Adolescent↗

Intermittent exotropia: stimulus characteristics affect tests for retinal correspondence and suppression.

BACKGROUND AND PURPOSE: Prior studies have reported various sensory responses in subjects with intermittent exotropia [X(T)]. These varying responses have been proposed due to differences in stimulus targets, backgrounds, or even a lack of control of binocular alignment. This study investigated the effects of varying target and background stimuli while controlling binocular alignment. METHODS: Eight X(T)s of the divergence excess or basic type were presented dichoptic computer generated visual stimuli while an infra red eye movement monitoring system determined horizontal eye position of each eye. Target and background were varied to assess their effect on sensory responses during latent and manifest exotropia. RESULTS: Most of our X(T)s demonstrated, while tropic, a consistent, i.e., dominant, type of retinal correspondence, i.e. a response that occurred on most tests, independent of the stimulus or background used for testing. Four subjects demonstrated harmonious anomalous retinal correspondence (HARC) while three subjects demonstrated normal retinal correspondence (NRC) with three out of four of the tests. In two out of four stimuli used for testing, one subject demonstrated NRC and another HARC. CONCLUSIONS: Complex backgrounds resulted in the largest number of suppressions, whereas blank backgrounds decreased the number of reported suppressions.

Adaptation, Ocular↗

[Possibilities of computer-assisted processing of the results of an examination of the visual system].

The authors present the first results of examining the vision system with the use of an automated programmed complex realized in the 'C' program language in the IBM and Dos operation system, that helped present in a chart the distribution of the ocular light sensitivity and time of the sensomotor reaction in every site of the visual field of 40-50 degrees. The results evidence that computer-aided methods may be effectively used to assess the light sensitivity of the eye, contrast sensitivity, space summation, rod and cone interactions, the topography of color photoreceptors, and the function of the posterior section of the eye in abnormalities of the retina and the optic nerve, as well as to monitor visual function rehabilitation after treatment.

Adaptation, Ocular↗