Ultrasound Biomicroscopic Features Of The Normal Lower Eyelid

Purpose: To report the ultrasound biomicroscopic features of normal lower eyelid structures.Methods: Thirty lower eyelids of fifteen healthy adults were randomized and prospectively subjected to Ultrasound Biomicroscopy (Quantel Aviso with 50 MHz transducer) by two independent observers (an ophthalmologist and an optometrist). The measurements were performed in upgaze, with the probe perpendicular to the lower eyelid margin in the mid-pupillary line, two limbal lines, and two canthal lines. The tarsus, orbicularis, capsulopalpebral fascia, and retractor-conjunctiva complex were assessed for two parameters: echogenicity (hyper/hypoechoic) and measurement in millimeters.Results: Mean age was 25 years (range 20-39 years), 15 (50%) were right lower eyelids and 8 were males. The first layer, skin-orbicularis complex appeared hyperechoic. The second layer was hypoechoic band which represents the tarsal plate superiorly and capsulopalpebral fascia inferiorly. This was noted to be continuous and of almost uniform thickness in the normal eyelids. The glandular structure of meibomian glands was identified in 100% cases. The hyperechoic layer below the capsulopalpebral fascia is the retractor-conjunctiva complex. The mean thickness of pretarsal and pre-septal orbicularis was 0.68 +/- 0.18 mm and 0.89 +/- 0.16 mm, respectively. The tarsal plate measured 0.57 +/- 0.12 mm, capsulopalpebral fascia 0.42 +/- 0.13 mm and the retractor-conjunctiva complex 0.79 +/- 0.18 mm. On Bland-Altman analysis, the majority of the measurements had mean agreements between -0.14 mm and +0.12 mm. Anatomical differentiation was not useful in the canthal region.Conclusion: Echogenicity and thickness of normal lower eyelid structures as measured by UBM are reported. The test is non-invasive, with a good inter-observer agreement.