Thick Cornea with High Back Elevation

The cornea plays a crucial role in refraction and so help in good visual acuity. with its thickness and back elevation being essential parameters in diagnosing and managing corneal diseases such as keratoconus.

The normal human cornea has a central thickness of approximately 540-550 µm. The periphery is generally thicker, reaching up to 700 µm. Corneal thickness is influenced by genetics, hydration, and intraocular pressure.Thick Cornea (\> 540 µm): Seen in conditions such as corneal edema and Fuchs' dystrophy. Thin Cornea (\< 500 µm): Observed in keratoconus, LASIK-induced thinning, and corneal ectasia.

Back corneal elevation is assessed using corneal topography or tomography, typically referenced to a best-fit sphere (BFS). In normal cases, Back corneal elevation is usually ≤12 µm above the BFS, indicating a structurally healthy cornea without signs of ectasia. Susceptible elevation ranges between 12-20 µm, which may be an early indicator of corneal instability, such as subclinical keratoconus. Therefore, it should be evaluated alongside other parameters, including pachymetry, anterior curvature, and biomechanical properties. Abnormal back corneal elevation is generally considered \>20 µm, particularly if localized or asymmetric, and is strongly associated with corneal ectatic disorders such as keratoconus, pellucid marginal degeneration, or post-LASIK ectasia. This abnormal elevation is often accompanied by other risk factors, including increased posterior corneal curvature, corneal thinning, and significant asymmetry, necessitating further assessment and monitoring.

Many cases of thick cornea are associated with high back elevation and this discourage refractive surgery in such cases so in investigator's study the investigator will follow up these cases to determine if these corneas are considered normal corneas or not.