[Macular hole evaluation with 10-MHz and 20-MHz ultrasonography and optical coherence tomography]

To evaluate and compare the data provided by 10-MHz and 20-MHz ultrasonography and optical coherence tomography (OCT) in macular hole exploration.

Sixty patients with macular hole at different stages were included in the study from January 2002 to April 2003. All patients received three successive examinations: an echographic examination with a 10- and 20-MHz probe (Quantel Medical Cinescan) and an examination with optical coherence tomography (OCT) (Humphrey Zeiss).

In stages I and II, the 10-MHz examination was not a useful tool; in certain cases the 20-MHz examination highlighted stage II macular holes. OCT was better than ultrasonography in all these cases: it clearly defined the outline of the hole and perifovea posterior vitreous detachment (PVD). In stage III, the 10-MHz examination only allowed the visualization of the high reflectivity of the prefoveal operculum; the 20-MHz examination could also measure the thickness of the macular neuroepithelium. OCT very precisely visualized the hole as well as the opercula and the detachment of the posterior hyaloid located in the macular area but still attached to the papilla. In stage IV, the 10-MHz examination confirmed total PVD. High-frequency ultrasound examination and OCT provided somewhat similar information. OCT provided the advantage of measuring the hole.

It is possible now to use probes of frequencies higher than 10 MHz for the study of the posterior pole and the vitreomacular junction at the cost of a more reduced exploration area than that usually obtained with a 10-MHz probe and a lower reflectivity of the interfaces encountered. One is indeed very quickly limited by noise if the gain is increased. Usually, the standard gain with 20 MHz is close to 90 dB and beyond 100 dB, the images are uninterpretable because of noise.

The 10-MHz ultrasonography is very useful for an overall assessment of the vitreous body, its mobility, and in searching for PVD. The 20-MHz examination gives very valuable information on the analysis of the vitreomacular junction, approaching the precision level provided by OCT. It demands a very rigorous examination protocol. OCT, however, remains better for the fine morphological study of this zone, unless opaque media studies are necessary to determine the maximum frequency usable to increase the space resolution of the lesions of the posterior pole. In this case, the combined ultrasonographic study using 10 and 20 MHz provides a valid diagnosis and a therapeutic approach to the posterior pole.