[Ultrasonographic study of posterior vitreous detachment in emmetropic eyes].

Vitreoretinal relationships can be evaluated by biomicroscopic examination and ultrasound. We analyzed 220 normal and emmetropic eyes in a population between the ages of 20 to 80 years to evaluate the position of the posterior vitreous surface (prospective study). We found that: Most cases of very partial and very peripheral P.V.D. (71/220 eyes; 32%), especially those confined to the nasal quadrant (50/71 eyes), corresponded to a simple increase of reflectivity of the vitreous base rather to than real PVD. Twenty-five per cent of the patients over the age of 80 years did not have PVD. The frequency of partial PVD located in 2, 3 and 4 quadrants except the posterior pole was very low, regardless of age. These partial PVD are transient. Fifty-eight per cent of the patients over the age of 80 years had a complete PVD. This percentage is clearly lower than that reported by most of the large biomicroscopic studies. The extension of PVD always begins at the vitreous base and ends at the posterior pole. This extension occurs around the age of 60-65 years and results, in most cases (35/38 eyes; 92%), in complete PVD with collapse. A prepapillary ring is a specific sign of complete PVD with or without collapse, but its absence (5/38 eyes) does not indicate the absence of PVD. The frequency of giant lacune is maximal (16/32 eyes; 50%) for young people between the ages of 30 and 40 years, then decreases as PVD becomes complete. The average level of reflectivity of the vitreous body is highest for patients between the ages of 70 and 80 years, but this variation is only very slight. This study also stresses the clinical criteria used to make the ultrasonic differential diagnosis between PVD and giant lacunae.