Final answer:
Astigmatism is a vision defect caused by the eye's inability to evenly focus light, often due to corneal irregularities. It can be detected with a special chart and is corrected with eyeglasses that have a cylindrical correction. 'ICD 9 irregular unspecified astigmatism' refers to a medical diagnosis code that was used for this condition under the ICD-9 system.
Step-by-step explanation:
Astigmatism is a common vision defect characterized by an unevenness or asymmetry in the focus of the eye. This condition typically arises from irregularities in the shape of the cornea, though it can also stem from lens irregularities or unevenness in the retina. These irregularities in the eye can cause rays of light to focus at different points, leading to images appearing elongated or distorted, which can manifest as less distinct vision.
To detect astigmatism, one can use a special chart, as illustrated in Figure 26.8. When viewed with one eye at a time, without spectacles, different lines may appear darker or clearer if astigmatism is present. The correction of astigmatism often involves a cylindrical correction in eyeglass prescriptions, as opposed to spherical corrections that are used for short- or farsightedness, which are uniform along all axes.
When astigmatism is described as irregular unspecified, it denotes that the astigmatism does not fit into the typical regular pattern and the specific details of the astigmatism's irregularity are not determined. In the context of ICD-9, 'ICD 9 irregular unspecified astigmatism' would refer to a diagnostic code used for insurance and medical records to denote this type of astigmatism before the transition to ICD-10 which includes more detail and complexity in coding.