Lensometry

Excerpt

Lensometry measures the strength and prescription of eyeglasses or contact lenses using a lensmeter, an instrument sometimes referred to as a focimeter, vertometer, or Lensometer™. The two common indications for lensometry are the measurement of the power of spectacles during an ophthalmic examination and the verification of spectacle prescriptions created in an optical laboratory.

Lensometry is based on the concept of lens neutralization, which states that the resultant power of a lens system is equal to the power required to neutralize its properties towards a net value of zero. The inbuilt lenses of a lensmeter are an adjustable collimator. Lensmeters may be manual, semi-automated, or fully automated. The lensmeter makes it possible to measure the dioptric vertex power, optical center, cylindrical axis, and prism of a lens; some lensmeters can also measure the amounts of tint, light transmission, and ultraviolet transmission of a lens.

This activity reviews the indications, contraindications, necessary preparation, technique, and clinical significance of lensometry while highlighting the role of the interprofessional eye care team in caring for patients who use lenses to correct refractive errors.