Cellular fibronectin and tenascin in experimental perforating scleral wounds with incarceration of the vitreous.

BACKGROUND: Posterior perforating eye injury carries a high risk of visual loss due to the formation of intravireal and epiretinal scar tissue. Intraocular scar formation in patients with retinal detachment has been shown to be associated with elevated intravitreal FN levels. The extracellular matrix glycoproteins fibronectin (FN) and tenascin (TN) have been located in epiretinal scar membranes. As both FN and TN are also involved in healing of cutaneous and corneal wounds, we undertook to study their expression in rabbit perforating scleral wounds with vitreous incarceration. METHODS: A perforating scleral wound was produced and sutured without removal of vitreous from the wound in 18 pigmented rabbits. The rabbits were killed at various times (1 h to 21 days) after the operation, and the indirect immunohistochemical method was used for demonstration of FN and TN. Monoclonal mouse hybridoma antibodies 52 DH1 and 100 EB2, recognizing the cellular form of FN (cFN) and TN, respectively, were used. RESULTS: During the first post-operative week immunoreaction for glycoproteins, both the locally produced cFN and TN, were observed at the scar tissue containing the prolabed vitreous and the adjacent sclera. Subsequently, the reaction gradually shifted to the vitreal side of the wound, and 3 weeks after the operation it was almost completely restricted to a separated mass of vitreous beneath the scar. CONCLUSION: The expression of cFN and TN in the scleral scar and vitreous is indicative of their local synthesis. The shift of the expression of those proteins to the vitreal side of the wound with time suggests that the scarring process in the vitreous is delayed compared to the sclera.

Energy levels needed for cyclophotocoagulation: a comparison of transscleral contact cw-YAG and krypton lasers in the rabbit eye.

The energy levels needed for cyclophotocoagulation using either transscleral contact krypton or cw-YAG lasers were compared in pigmented rabbits. The same transscleral laser probe was used for both lasers. With the krypton laser, 0.25 J of energy caused macroscopically detectable lesions, and 1.5 J led to widespread destruction of the ciliary body. With the cw-YAG laser, the first detectable lesions were produced at 0.5 J. Similarly, at higher energies, twice as much energy was required using the cw-YAG as compared with using the krypton laser to produce comparable lesions. Histologically, lesions of the same macroscopic severity made with the two lasers were similar. We conclude that the transscleral contact krypton laser is an efficient instrument for cyclophotocoagulation. Although these results may not be directly applied to human eyes, it appears that the poorer scleral transmission of the krypton beam is offset by its higher level of absorption in the pigmented epithelium of the ciliary body.

Comparison of retinal lesions produced by transscleral krypton laser photocoagulation, transpupillar krypton laser photocoagulation and cryocoagulation.

We compared the retinal lesions produced by transscleral and transpupillar krypton lasers and cryocoagulation. Transscleral laser photocoagulation was applied under indirect ophthalmoscope visual control with indentation of the sclera by the laser probe. Transpupillar laser was performed with a Volk 90D lens. The power and the spot size were adjusted to create lesions of similar size and intensity as in transscleral photocoagulation. The output power needed for transscleral photocoagulation was 0.2W with exposure time of 3-5 sec. In the transpupillar photocoagulation the output power was 0.3W and the exposure time 2-3 sec, respectively. The lesions were studied histologically 1h, 1, 3, 7, 30 and 60 days after treatment. Histopathological studies of the krypton laser lesions revealed destruction and scarring of the outer layers of the retina and the choroid. The lesions produced by transpupillar and transscleral laser appeared to be rather similar. These results indicate that, in the rabbit eye, there is no difference between the lesions produced by the transpupillar or transscleral route of laser application. Transscleral laser application may have clinical advantages over transpupillary laser in the eyes with hazy media or in other cases when transpupillar laser is not possible.

Transcleral contact krypton-laser photocoagulation of the retina in rabbits.

Transcleral contact retinal krypton laser photocoagulation of the retina was studied in rabbit eyes. The laser application was performed under indirect ophthalmoscope visual control with indentation of the sclera by the laser probe. Retinal lesions were produced with powers ranging from 0.2 to 0.3 W and application times between 1 and 2 sec. The lesions were studied histologically 2, 5, 10, 12, 20, 30 and 70 days after treatment. Histopathological examination of the lesions showed damage of mainly the outer retinal layers in light lesions, and to all layers of the retina in the more intense lesions. No scleral damage was observed in the light lesions, whereas transient oedema of the inner sclera was seen in the intense lesions. Studies with enucleated rabbit eyes showed that indentation of the sclera by the laser probe substantially decreased the power needed to produce a retinal lesion. It is concluded, that when used with scleral indentation, transscleral krypton laser photocoagulation of the retina can be performed with minimal damage to the sclera.