Altered globe dimensions of axial myopia as risk factors for penetrating ocular injury during peribulbar anaesthesia

Abstract

We measured the range of equatorial horizontal widths (EHW) in axially myopic eyes and indentified the sites of staphyloma using B scan echography. One hundred eyes in 50 patients were studied. The axial lenghts (ALs) were sorted into five groups of increasing severity of myopia. The group mean AL, group mean EHW and the ratio of EHW/AL was calculated for each range. The results suggest that the increase in the AL in an axially myopic eye is assoiciated with an increase in the EHW. However, this increase in the group mean EHW is relatively small (2.3 mm) compared with the increase mean AL (8.2 mm) across the entire range. The ratio of EHW/AL decreased with an increase in the group mean AL. Therefore, the increase in EHW in an axially myopic eye is unlikely to be a significant risk factor for inadvertent ocular injury for peribulbar injections if a careful single medial canthal approach is used. There was high incidence of staphylomas in eyes with AL >29 mm, most were inferior to the posterior pole of the globe, and there were none at the equator.