Anterior Segment and Corneal Parameters in Keratoconus and High Myopic Astigmatism Using Schiempflug Imaging

Comparison of Anterior Segment and Corneal Parameters in Keratoconus and High Myopic Astigmatism Using Schiempflug Imaging

The purpose of this study was to compare Scheimpflug corneal tomography findings in keratoconus and high myopic astigmatic eyes, as well as to establish the parameters distinguishing keratoconus from high myopic astigmatism.

Keratoconus is a progressive, non-inflammatory corneal ecstatic disorder caused by alteration in the structure and organization of corneal collagen fibers. It results in uneven steepening of the cornea, resulting in irregular astigmatism that cannot be totally corrected with glasses, impairing the quality of life . However, in many cases, increased axial length adds to the myopic component of refractive error . Thereafter, keratoconus patients frequently have axial high myopia with irregular astigmatism . Furthermore, early diagnosis of keratoconus aids in the timely management of the condition, thus improving patients' quality of life. According to research, high myopia, in addition to the degree of astigmatism, is an alarming sign that requires further corneal assessment to rule out any corneal abnormalities such as keratoconus. Furthermore, keratoconus could be misdiagnosed as meridional amblyopia attributable to myopic astigmatism due to the lack of corneal tomography measurements . As a result, it is critical to evaluate all high myopia patients, particularly those considering refractive surgery, for high-risk corneas.

The criteria for diagnosing and classifying keratoconus are based on anterior corneal curvature data obtained using Placido-based corneal topography . Early alterations in eyes with keratoconus, however, have been found on the posterior corneal surface . Scheimpflug imaging uses a revolving Scheimpflug camera to determine the front and back surfaces of the cornea, hence measuring the overall thickness. Several studies have utilized Scheimpflug tomography to evaluate anterior segment parameters between normal eyes and eyes with keratoconus , but the utility of Scheimpflug imaging to distinguish between keratoconus and high myopic astigmatism has not been thoroughly examined.

Inclusion Criteria:

• keratoconus patient
• virgin clear cornea with high myopic astigmatism
• normal cornea with high myopic astigmatism

Exclusion Criteria:

• patients had previous ocular surgery
• ocular diseases rather than keratoconus
• contact lens wearer
• corneal opacity and corneal dystrophy