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 identified the sites of staphyloma using B scan echography. One hundred eyes in 50 patients were studied. The axial lengths (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 associated 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.

Using High-Resolution 3D Magnetic Resonance Imaging to Quantitatively Analyze the Shape of Eyeballs with High Myopia and Provide Assistance for Posterior Scleral Reinforcement

“…The axial length, horizontal length, vertical length, and volume of the highly myopic eyes were greater than those of the emmetropic eyes, with the axial length obviously increasing more than the vertical and the horizontal lengths. These findings are similar to those made by Vohra and Good [23] and suggest that the expansion of highly myopic eyes might be predominantly axial. The amplification of the horizontal length was less pronounced than that of the vertical length, a finding that differs from the results of Atchison et al [24,25] .…”

Effects of Form Deprivation on Peripheral Refractions and Ocular Shape in Infant Rhesus Monkeys (Macaca mulatta)

“…Many techniques—x-ray tomography,45 B-scan ultrasonography,46 computed tomography,47 optical coherence reflectometry,48 MRI23–25,49—have been used to compare eye shape and refractive error in humans. Although there is substantial variability in eye shape between subjects, between studies, and within a given refractive error group, there is general agreement that the eyes of humans with emmetropia are typically oblate and that the eyes of those with myopia have larger equatorial (horizontal) diameters and much longer axial lengths.…”

Relation between Axial Length and Ocular Parameters

“…Several studies have investigated changes in eyeballs according to elongation of AL, a cause of axial myopia. Vohra and Good [2] suggested that expansion of highly myopic eyes may be predominantly axial rather than global, at least when compared in the horizontal meridian. Zhou et al [3] reported that emmetropic eyes usually have similar lengths and widths, but that myopic eyes are greater in length than width and that the dimension differences increase quickly with increases in myopia.…”