[GRIN (gradient-index) intraocular endoscopy--possibilities and limits--a review]

Microendoscope techniques got a more important role in intraocular diagnostic and therapy. The used optical systems are fiberbundle-endoscopes and gradient-index (GRIN)-endoscopes. This study is concerned with the possibilities and limits of GRIN-endoscopes in pig eye models and in clinical use.

Several simulated intraocular techniques (phacoemulsification, implantation of intraocular lenses, vitrektomie, extraction of lost lens parts out of the corpus vitreous, extraction of metal foreign bodies) were done on pig eyes under GRIN-endoscopic control (GRIN-endoscope with diameter of 0.89 mm, Volpi, Switzerland). 3 clinical patients with cornea or lens opacities were examined.

The image quality of simulated operations on pig eyes in clear intraocular conditions with a GRIN-endoscope was good. Also the clinical intraocular examinations could be done well, although the additional information were different. The in vivo examinations gave in one case no information (vitreous opacities very tight), in one case a relative information (mild vitreous opacities) and in one case an additional information (vitreous opacities rare).

GRIN-endoscopes could complement the intraocular endoscopic spectrum in selected cases. At clear intraocular conditions good pictures were possible. GRIN-endoscopes could be used in cases where endoillumination is necessary. Then additional visual informations to the illumination are possible. The possibility to get overview images is limited with the actual endoscope probes. Ultrasound examination should be done in all cases with opacities of the anterior parts of the eye to get informations about the conditions inside the eye. Working inside the eye is possible with experience in this technique although a GRIN-endoscope has no stereopsis. Future developments should be done in stereopsis, several endoscope-tips and better handling (footpedal-controlling, autofocus).