Calculation of eye length

Eye length is calculated using a model with corneal values and refraction and is a guide value. This guideline value should not be used for diagnosis, but it can be used as an evaluation aid if a biometer is not available

Guide values are calculated for children aged 8 to 12 years. These values may deviate by ±0.73 mm or ±3.0 % of the true measured axial length measurement. Ninety-five percent of the values derived from the formula fall within about three-quarters of a millimeter of the "true" axial length (measured with an interferometric biometer).Morgan PB, McCullough SJ, Saunders KJ. Estimation of ocular axial length from conventional optometric measures. Cont Lens Anterior Eye. 2020 Feb;43(1):18–20.