Quantification of the Posterior Cornea Using Swept Source Optical Coherence Tomography.

Area of Science:

• Ophthalmology
• Anatomy
• Medical Imaging

Background:

• Accurate measurement of corneal structures is crucial for planning advanced ophthalmic procedures.
• The transition zone (TZ) of the cornea, potentially containing progenitor cells, plays a role in endothelial regeneration.
• Optical coherence tomography (OCT) offers a non-invasive method for anterior segment imaging.

Purpose of the Study:

• To define and describe optical coherence tomography (OCT) measurement parameters for the corneal endothelium/Descemet's membrane (DM) complex and the peripheral transition zone (TZ).
• To evaluate these measurements in a healthy ethnically Chinese population.

Main Methods:

• Anterior segment OCT imaging was performed on 129 healthy Chinese subjects.
• Key landmarks, including the scleral spur (SS) and Schwalbe's line (SL), were identified.
• Endothelial arc length (EAL) was measured as the SL-to-SL distance, and TZ width was approximated using a ratio derived from scanning electron microscopy (SEM) data.

Main Results:

• The mean endothelial arc length (EAL) was 12.15 ± 0.58 mm, and the mean transition zone (TZ) width was 156 ± 20 μm.
• Vertical EAL was found to be significantly greater than horizontal EAL (P = 0.03).
• A validated relationship TZ = 0.20*(TZ+TM) was established from SEM data.

Conclusions:

• OCT enables the measurement of corneal endothelium/DM diameter and approximation of TZ width.
• These OCT-derived measurements are valuable for preoperative planning in procedures like Descemet's membrane transplantation (DMT).
• The ability to approximate TZ width using OCT is a significant advancement for understanding its role in endothelial regeneration.