Original papers: Does strabismus surgery induce significant changes of corneal topography?

To determine whether strabismus surgery significantly influences corneal curvature, corneal topography was measured in 68 patients before and both one day and three months after strabismus surgery. With few exceptions, early corneal topographic changes were moderate, statistically not significant and nearly disappeared after 3 months. Long term absolute astigmatism increased not significantly by 0.16 D. Our results demonstrate that strabismus surgery can induce transitory but usually no long term changes of corneal topography. Patients should be informed, however, that in rare cases an induced astigmatism may persist.

[Effect of strabismus operation of corneal topography]. / Einfluss der Strabismusoperation auf die Hornhautwölbung.

BACKGROUND: In order to determine the short- and long-term influence of strabismus surgery on corneal curvature, a prospective study was carried out measuring corneal topography before and after operation. PATIENTS AND METHODS: Corneal topography was performed using a computer assisted videokeratoscope. 77 eyes of 74 patients were examined 1 day before and 1 day as well as 3 months after surgery. Data of the semimeridians at 0 degree, 90 degrees, 180 degrees and 270 degrees in the 3-, 5- and 7-mm zone and of the corneal center were analyzed. Objective refraction, induced astigmatism and simulated keratometer reading were evaluated. 39 horizontal recess-resect procedures. 12 inferior rectus recessions, 10 horizontal resections. 10 inferior oblique recessions and 6 other procedures were performed. RESULTS: The spheric equivalent of objective refraction decreased by 0.23 D. The absolute astigmatism increased by 0.16 D, the maximum change was 1 D. Changes of objective refraction were statistically not significant. The simulated keratometer reading increased by 0.2 D postoperatively and returned to the initial value after 3 months. With few exceptions, corneal topographic changes were small, statistically not significant and nearly disappeared after 3 months. Corneal flattening tended to occur in the semimeridian of resection while corneal steepening was observed at the site of recession. CONCLUSIONS: The influence of strabismus surgery on corneal astigmatism is usually small and mostly transitory. In a few cases, however, the induced astigmatism persists. Patients should be informed about this possibility preoperatively.

[Primary vitrectomy in rhegmatogenous retinal detachment]. / Primäre Vitrektomie bei rhegmatogener Ablatio retinae.

For therapy of uncomplicated rhegmatogenous retinal detachment, a buckling procedure is the standard surgical technique today. In complicated cases, e.g., retinal redetachment after a failed buckling procedure, vitrectomy is established. Meanwhile it is being discussed whether or not certain retinal detachments, e.g., with atypically large tears, should be treated with primary vitrectomy. We studied retrospectively all primary vitrectomies for retinal detachment without proliferative vitreoretinopathy (PVR) that were operated upon during 1992 in Würzburg Eye Hospital (32 patients). In 56% (18 eyes) of the patients a subtotal or total retinal detachment was seen preoperatively; in 47% (15 eyes) the macular region was detached. In 25% (8 eyes) large retinal tears were seen (> 1 h). The other patients showed atypical horseshoe tears partly central to the equator or multiple holes. Seventy-eight percent (25 eyes) of all cases were successfully vitrectomized with one operation and revealed good results using intraocular tamponade (SF-6/air mixture). Seven patients needed further vitrectomy partly using silicone oil as an intraocular tamponade. In cases of rhegmatogenous retinal detachment with atypical tears or non-identified holes, vitrectomy without the buckling procedure is a good alternative, because the rate of successful results is as high as what is achieved with buckling procedure in uncomplicated cases.

[Results of pars plana vitrectomy with intraocular SF-6 gas tamponade in complicated retinal detachment]. / Ergebnisse nach Pars-plana-Vitrektomie mit intraokularer SF-6-Gas-Tamponade bei komplizierter Ablatio retinae.

Vitrectomy following complicated retinal detachment (PVR, giant tears, persistent retinal detachments or redetachments) has become standard in ophthalmic surgery. Intraocular tamponade is performed with gas (e.g. SF-6) or silicone oil. We retrospectively analyzed our functional and anatomical results after vitrectomy with SF-6 gas tamponade in complicated cases of retinal detachment. Ninety-four severe retinal detachments in 85 patients were treated by vitrectomy using SF-6 gas tamponade in the period from July 1990 to June 1991. In 68% of eyes complete retinal reattachment was achieved with the use of SF-6 gas. Thirty-two per cent of the operated eyes developed retinal redetachment an average of 3.4 weeks after initial surgery; 27% of those eyes were treated again with the use of silicone oil. The success rate using vitrectomy with SF-6 gas ranged between 46% and 74%, depending on pathogenetic factors. The best results were obtained in patients receiving primary vitrectomy for complicated retinal detachment. It is concluded that SF-6 gas is a successful tool in the treatment of severe retinal detachment with primary vitrectomy. In cases of persistent or recurrent detachment of the retina the results are not equally good and these cases merit consideration of silicone oil tamponade, depending on the severity of the disease process. However, no definite preoperative criteria for the success of vitrectomy and gas tamponade were identified.

Problems and timing in the removal of silicone oil.

The risk associated with silicone oil removal after complex vitreoretinal surgery is unclear. Therefore, a cohort of 87 consecutive cases of silicone oil removal were analyzed. Eyes with attached retina before silicone oil removal with a follow-up of at least 5 months were included into the study. Forty-eight eyes had severe proliferative diabetic retinopathy; 39 eyes had complex proliferative vitreoretinopathy or giant retinal tears after trauma. Additional clinical features included the presence of a secondary cataract or secondary glaucoma in some eyes. The rate of postoperative complications was different in the two groups: 75% of proliferative diabetic retinopathy patients remained attached; of proliferative vitreoretinopathy patients, only 48.5% remained stable. Whereas success was independent of the duration of intraocular silicone oil tamponade in proliferative diabetic retinopathy, removal of silicone oil was more successful in cases of proliferative vitreoretinopathy in which there was a longer period of silicone oil tamponade. Complications occurring usually were severe and led to a loss of visual acuity. The removal of silicone oil from eyes with secondary glaucoma resulted in an improvement in 68% of patients. The rate of vitreoretinal complications after silicone oil removal, even in cases with a clinically stable-appearing retina, is rather high. Silicone oil removal therefore has to be considered a procedure posing new and ill-defined risks, especially if the indications for the use of silicone oil as an internal tamponade are rather strict. Exact criteria for the timing and safe removal of silicone oil in these complex vitreoretinal disorders still need to be defined.

[Possibilities of silicone oil removal after complex vitreoretinal surgery]. / Möglichkeit der Silikonölentfernung nach komplexer vitreoretinaler Chirurgie.

The question of the long-term risks and benefits of silicone oil removal after complex vitreoretinal surgery involving the use of silicone oil has not yet been answered. A consecutive series of 50 eyes from which silicone oil had been removed were therefore analyzed in a retrospective study. In all cases the retina was completely attached and seemed to be stabilized before silicone oil removal. The reasons for the original surgery were severe proliferative diabetic retinopathy (PDR) in 20 cases and proliferative vitreoretinopathy (PVR) in 30, in 2 of which PVR developed after perforating injuries. Silicone oil was removed because the retina was clinically stable and completely attached, and in some cases cataract or glaucoma was present. The complication rate after silicone oil removal in these situations varied widely in dependence on the form of disease. After PDR stable conditions were achieved in 70% of cases after silicone oil removal. After PVR with retinal detachment the situation remained stable in only 50%. The most frequent complication was retinal redetachment because of recurrent PVR, accounting for 80% of all failures. The success rate with silicone oil removal after PDR in this study was independent of the duration of tamponade, which had lasted for about 1 year in most cases. Following PVR, silicone oil removal seems to be more safer after long-term tamponade (22 months) than after a shorter duration (12 months). Secondary glaucoma during silicone oil tamponade could be influenced positively in 70% of all cases by silicone oil removal. Because of the relatively high rate of complications after silicone oil removal, especially in PVR, the indications for removal must be carefully considered.