ABSTRACT.Purpose: To find the most reliable and efficient noninvasive technique to clinically detect a posterior vitreous detachment. Methods: In a prospective study of 30 eyes in 30 patients with macular pucker or macular hole formation, the posterior vitreous cortex was examined 1 day prior to a scheduled vitrectomy. Three independent investigators classified the posterior vitreous cortex of each eye as 'attached' or 'detached' via slit-lamp biomicroscopy (BM), 10-MHz B-scan ultrasonography (I 3 Innovative Imaging Inc.), and optical coherence tomography [OCT III Stratus Ò (Carl Zeiss Meditec Inc.) and RTVue-100 OCT (Optovue Corp.)]. These preoperative findings were then compared during a triamcinolone acetonide-assisted vitrectomy 1 day later. Results: Triamcinolone acetonide-assisted vitrectomy showed in 60% a posterior vitreous detachment and in 40% an attached posterior vitreous cortex. Preoperatively conducted B-scan ultrasonography and BM revealed the highest, correct evaluation of the posterior vitreous status. The prediction of the OCT was confirmed intraoperatively in 12.5%. In all other cases, the evaluation by OCT was not possible or was inadequate. Conclusion: The prognostic most reliable but investigator-dependent methods to clinically detect whether the posterior vitreous cortex is detached are B-scan ultrasonography and BM. The objective technique of the high-resolution, twodimensional time-domain OCT allows only in a few cases a clear differentiation of preretinal structures.

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ABSTRACT.Purpose: To evaluate the posterior vitreous adhesion status in patients with a history of central or branch retinal vein occlusion and to compare the results with the natural time-course of posterior vitreous detachment in healthy agerelated controls. Methods: A retrospective chart review in terms of the posterior vitreous adhesion status was performed in 132 patients (133 eyes) with a history of a central (CRVO) or branch (BRVO) retinal vein occlusion. All patients underwent vitrectomy. Based on the operation reports, the vitreous adhesion status was classified as attached, partially detached or completely detached. The results were compared to the natural time-course of posterior vitreous detachment development in healthy age-related controls. Results: Eighty-one eyes met the inclusion and exclusion criteria. Fifty-two eyes (64%) had a history of CRVO and 29 eyes (36%) a history of BRVO, respectively. In the CRVO group, the posterior vitreous was attached in 47 eyes (90%) and completely detached in five eyes (10%). In the BRVO group, the posterior vitreous was attached in 27 eyes (93%), partially detached in 1 eye (3%) and completely detached in another eye (3%). A subdivision into age classes and a comparison with healthy age-related controls [data by WeberKrause & Eckardt (1997) Ophthalmologe, 94,[619][620][621][622][623] showed in patients between 65 and 69 years of age an attached posterior vitreous cortex in 72% in healthy eyes, in 100% in CRVO (p = 0.109) and in 89% in BRVO (p = 0.440), in patients between 70 and 79 years of age an attached posterior vitreous cortex in 56% in healthy eyes, in 86% in CRVO (p = 0.010) and in 100% in BRVO (p = 0.038) and in patients between 80 and 89 years of age an attached posterior vitreous cortex in 43% in healthy eyes, in 100% in CRVO (p = 0.191) and in 67% in BRVO (p = 0.582) (Fisher's exact t-test). Conclusion: In patients with a history of CRVO or BRVO, the posterior vitreous cortex stays attached more frequently in all age groups in comparison with the healthy age-related controls.

The development of molecularly targeted therapies for certain types of cancers has led to the consideration of population enrichment designs that explicitly factor in the possibility that the experimental compound might differentially benefit different biomarker subgroups. In such designs, enrollment would initially be open to a broad patient population with the option to restrict future enrollment, following an interim analysis, to only those biomarker subgroups that appeared to be benefiting from the experimental therapy. While this strategy could greatly improve the chances of success for the trial, it poses several statistical and logistical design challenges. Because late-stage oncology trials are typically event driven, one faces a complex trade-off between power, sample size, number of events, and study duration. This trade-off is further compounded by the importance of maintaining statistical independence of the data before and after the interim analysis and of optimizing the timing of the interim analysis. This paper presents statistical methodology that ensures strong control of type 1 error for such population enrichment designs, based on generalizations of the conditional error rate approach. The special difficulties encountered with time-to-event endpoints are addressed by our methods. The crucial role of simulation for guiding the choice of design parameters is emphasized. Although motivated by oncology, the methods are applicable as well to population enrichment designs in other therapeutic areas.