Central corneal thickness

Central Corneal Thickness (CCT) is a key ophthalmological measurement that refers to the thickness of the central zone of the cornea. This measurement is crucial in the diagnosis and management of various eye diseases and conditions, including glaucoma, keratoconus, and is also significant in determining the suitability of a patient for refractive surgery procedures such as LASIK.

Overview

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The central corneal thickness can vary significantly among individuals. On average, the CCT is about 540 micrometers in adults, but it can range from 480 to 600 micrometers. Measurements of CCT are typically performed using pachymetry, which can be conducted through various methods including ultrasound pachymetry and optical coherence tomography (OCT).

Clinical Significance

The measurement of CCT has been found to have significant clinical implications:

• Glaucoma: CCT is a critical factor in the assessment of glaucoma risk. Thinner corneas have been associated with an increased risk of developing glaucoma. Additionally, CCT can affect intraocular pressure (IOP) readings, with thinner corneas potentially leading to underestimation of IOP, a key factor in glaucoma management.

• Refractive Surgery: Determining CCT is essential before undergoing refractive surgery procedures such as LASIK. A sufficient corneal thickness is necessary to ensure the safety and effectiveness of the surgery, as the procedure involves reshaping the cornea to correct vision.

• Keratoconus: In conditions like keratoconus, where the cornea becomes thinner and bulges outward, CCT measurements can help in diagnosing the condition and monitoring its progression.

Measurement Techniques

Several techniques are available for measuring CCT:

• Ultrasound Pachymetry: This is the most common method, involving the use of a handheld device that measures the corneal thickness using ultrasound waves.

• Optical Coherence Tomography (OCT): OCT is a non-contact method that provides high-resolution images of the cornea, allowing for accurate CCT measurements.

• Specular Microscopy: Though primarily used for endothelial cell analysis, it can also provide estimates of corneal thickness.

Conclusion

Central Corneal Thickness is a vital measurement in ophthalmology, influencing the diagnosis, management, and therapeutic outcomes of various eye conditions. Accurate measurement of CCT is essential for the proper assessment of glaucoma risk, the safety and effectiveness of refractive surgery, and the diagnosis and monitoring of corneal diseases like keratoconus.