A new method to measure refractive error called GRAS (Gullstrand Refractive Analysis System) by Hessler et al. can be used to analyze the components of refractive error. Understanding these components is crucial for optometrists to effectively prescribe corrective lenses and identify potential causes of vision problems.
Between the ages of 6 and 15, the axial length of the eye increases by about 1 millimeter per year, while crystalline lens power decreases by about 3 diopters. Corneal power remains stable during this period. The GRAS method separates refractive error into its component parts, including axial length, corneal power, and crystalline lens power, allowing optometrists to distinguish between axial myopia (caused by excessive eyeball elongation) and refractive myopia (caused by abnormal corneal or lens curvature). This distinction is important because these two types of myopia progress differently and may require distinct treatment approaches.
Here’s how optometrists can use this method in practice:
Identify the cause of refractive error: By analyzing the individual components of refractive error with GRAS, optometrists can pinpoint the underlying cause of vision problems. This is important for determining the most appropriate treatment course.
Predict progression of myopia: Axial myopia is more likely to progress than refractive myopia. By identifying the type of myopia present, optometrists can better predict how a patient’s vision will change over time.
Develop treatment plans: Understanding the cause of myopia allows optometrists to develop individualized treatment plans. For example, if axial myopia is the culprit, interventions to slow eyeball growth may be recommended.
GRAS offers a valuable new tool for optometrists to improve their understanding of refractive error and provide better patient care. To learn more about GRAS, read the original article for in-depth methodology.
