The Comparison Of The Measurement Value And The Theoretical Value For The Corneal Total Power With ORBSCAN

Objective: Discussing two kinds of measuring methods for corneal total power andcomparing the measurement value and the theoretical value with ORBSCAN and evaluating the accuracy of ORB SCAN.Methods: With ORBSCAN corneal topographic map measuring for 47 patients (91eyes ) of no corneal refractive surgery history the actual values of total mean power and keratometric mean power of the corneal vertex. By means of Gaussian formula and corneal hypothetical refractive index formula calculating the theoretical value of total mean power and keratometric mean power of the corneal vertex. With a statistical analysis of matching T test comparing above fou values;With a statistical analysis of simple T test comparing anterior surface curvature radius and posterior curvature radius in the patients and the general population; With a statistical analysis of matching T test comparing the actual values of the corneal total power in the corneal vertex and the 3 mm region. Results: Two theoretical values of the corneal total power of the corneal vertex bymeans of Gaussian formula and corneal hypothetical refractive index formula are statistically significant differences(P<0.01):the average deviation for -1.37±0.20D. The actual measurement values with the instrument of two different methods are also remarkably different(P<0.01):the average deviation of statistis for -1.57±0.78D. The theoretical values of Gaussian formula an the corresponding actual measurement values of the corneal total power is not statistically differences(P>0.05). Anterior surface curvature radius and posterior curvature radius in the patients and the general population is not statistically differences(P>0.05). The actual values of the corneal total power in the corneal vertex and the 3mm region is not statistically differences(P>0.05).Conclusion: ORBSCAN corneal topographic map measurement system and othercorneal curvature measuring system in calculation method and measuring principle have obvious difference. To achieve the ideal refractive status and avoid the measurement inacuuracy of the corneal total power with other corneal curvature measurement system basing for corneal hypothetical refractive index formula, we suggest to do a check with ORBSCAN basing for Gaussian formula for the patients preparing for the corneal and intraocular refractive surgery to assess the corneal refractive status in the situation of equipment conditions.