Purpose:
To determine if morphometric details of the limbal region under the upper eyelid can be obtained using OCT, and if so, to morphometrically characterize the vessels and epithelium.
Methods:
In 20 normal subjects, images tangential to the limbus were acquired with an ultra-high resolution optical coherence topographer (UHROCT) after manual retraction of the upper eye lid. The system, with 3µm axial and 10µm lateral resolution, was used to acquire a cube of data across the limbus, starting with clear cornea and transitioning to bulbar conjunctiva, at a rate of 47,000 A-scans/s. Image attributes were measured using ImageJ and in particular the lower scattering corneal/conjunctival epithelial layer and vessels were measured.
Results:
The figure shows a median filtered UHROCT image of the limbus under the eyelid. The uppermost layer is conjunctival epithelium with brighter circular and oval areas being conjunctival vessels. Below these are episcleral vessels and below this layer is scleral tissue (illustrating the detailed deeper drainage that can be imaged). Limbal corneal epithelial thickness (+/- se) was 95.3 +/- 15 microns, and conjunctival epithelial thickness was 69.9 +/- 5 microns. The average vessel diameter (+/- se) was 28.7 +/- 2 and 34.9 +/- 3 microns in the conjunctiva and episclera respectively (paired t-test p=0.16).
Conclusions:
Upper bulbar conjunctival and limbal tissue can be imaged (and therefore measured) using the UHROCT. These morphometric characteristics will enable us to begin to determine how the the upper limbus adjusts to being chronically covered by the upper lid.
Keywords: cornea: epithelium • conjunctiva • imaging/image analysis: clinical