Measuring corneal radius with illumination

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    Measuring Radius
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SUMMARY

The discussion centers on calculating the corneal radius using magnification and lens formulas. The user applied a magnification of 0.0156, leading to an object distance (o) of -1538.46 cm and a focal length (f) of 24.38 cm. However, the user realized an error in flipping the object and image distances, which resulted in a calculated corneal radius of 48.76 cm, significantly deviating from the average corneal radius of approximately 5 mm found in literature. This highlights the importance of correctly applying optical formulas in measurements.

PREREQUISITES
  • Understanding of optical magnification principles
  • Familiarity with lens formulas (1/f = 1/i + 1/o)
  • Basic knowledge of corneal anatomy and measurements
  • Experience with unit conversions in optics
NEXT STEPS
  • Review the principles of optical magnification and its applications in medical measurements
  • Study the lens formula in detail, including practical examples
  • Research the average corneal radius and its clinical significance
  • Explore common errors in optical measurements and how to avoid them
USEFUL FOR

Optometrists, ophthalmologists, medical students, and anyone involved in optical measurements and corneal assessments.

ewang
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Homework Statement
An ophthalmometer* is used by optometrists to measure the curvature of a patient’s cornea by shining an illuminated shape on the cornea and measuring the size of the reflected image relative to the object. For one patient, the object was 24 cm from their cornea and the image height was 0.0156 times the height of the object. What is the radius of this patient’s cornea?
Relevant Equations
f = R/2
1/f = 1/i + 1/o
m = -i/o
Since magnification is 0.0156, I have:
m = -i/o
0.0156 = -24cm/o
o = -1538.46 cm

1/f = 1/i + 1/o
1/f = 1/24 cm - 1/1538.36 cm
f = 24.38 cm
R = 48.76 cm

However, when I look up the average corneal radius, the google results show ~5 mm. Did I do something wrong?
 
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Shoot nevermind, I flipped object and image distances.
 

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