An astigmatism nomograph system, the system comprising: a processor having access to memory media storing instructions executable by the processor to: calculate an expected astigmatism coefficient for a patient subject to a first corneal laser treatment as a first difference between a pre-operative astigmatism coefficient and a correction astigmatism coefficient, wherein the pre-operative astigmatism coefficient represents a first measurement of a cornea of the patient before the first corneal laser treatment, and the correction astigmatism coefficient represents changes to the cornea planned for the first corneal laser treatment; receive an indication that the first corneal laser treatment on the cornea of the patient was performed according to the correction astigmatism coefficient; receive an actual astigmatism coefficient of the cornea of the patient, wherein the actual astigmatism coefficient represents a second measurement of the cornea after a time period after the first corneal laser treatment; and calculate a nomograph value based on a second difference between the expected astigmatism coefficient and the actual astigmatism coefficient; and use the nomograph value to calibrate the correction astigmatism coefficient for a subsequent corneal laser treatment on another patient, wherein the second difference for the subsequent corneal laser treatment on the other patient is smaller than the second difference for the first corneal laser treatment, wherein the nomograph value is calculated based on a sample population of patients, wherein the pre-operative astigmatism coefficient, the correction astigmatism coefficient, the expected astigmatism coefficient, the actual astigmatism coefficient, and the second difference are determined for each patient in the sample population, wherein the nomograph value is calculated as an empirical function of the actual astigmatism coefficient versus the expected astigmatism coefficient for the sample population, characterized in that a data point of the empirical function is determined using a median value of the actual astigmatism coefficient, and the empirical function is calculated using curve fitting of a plurality of the data points. a processor having access to memory media storing instructions executable by the processor to: calculate an expected astigmatism coefficient for a patient subject to a first corneal laser treatment as a first difference between a pre-operative astigmatism coefficient and a correction astigmatism coefficient, wherein the pre-operative astigmatism coefficient represents a first measurement of a cornea of the patient before the first corneal laser treatment, and the correction astigmatism coefficient represents changes to the cornea planned for the first corneal laser treatment; receive an indication that the first corneal laser treatment on the cornea of the patient was performed according to the correction astigmatism coefficient; receive an actual astigmatism coefficient of the cornea of the patient, wherein the actual astigmatism coefficient represents a second measurement of the cornea after a time period after the first corneal laser treatment; and calculate a nomograph value based on a second difference between the expected astigmatism coefficient and the actual astigmatism coefficient; and use the nomograph value to calibrate the correction astigmatism coefficient for a subsequent corneal laser treatment on another patient, wherein the second difference for the subsequent corneal laser treatment on the other patient is smaller than the second difference for the first corneal laser treatment, calculate an expected astigmatism coefficient for a patient subject to a first corneal laser treatment as a first difference between a pre-operative astigmatism coefficient and a correction astigmatism coefficient, wherein the pre-operative astigmatism coefficient represents a first measurement of a cornea of the patient before the first corneal laser treatment, and the correction astigmatism coefficient represents changes to the cornea planned for the first corneal laser treatment; receive an indication that the first corneal laser treatment on the cornea of the patient was performed according to the correction astigmatism coefficient; receive an actual astigmatism coefficient of the cornea of the patient, wherein the actual astigmatism coefficient represents a second measurement of the cornea after a time period after the first corneal laser treatment; and calculate a nomograph value based on a second difference between the expected astigmatism coefficient and the actual astigmatism coefficient; and use the nomograph value to calibrate the correction astigmatism coefficient for a subsequent corneal laser treatment on another patient, wherein the second difference for the subsequent corneal laser treatment on the other patient is smaller than the second difference for the first corneal laser treatment, wherein the nomograph value is calculated based on a sample population of patients, wherein the pre-operative astigmatism coefficient, the correction astigmatism coefficient, the expected astigmatism coefficient, the actual astigmatism coefficient, and the second difference are determined for each patient in the sample population, wherein the nomograph value is calculated as an empirical function of the actual astigmatism coefficient versus the expected astigmatism coefficient for the sample population, characterized in that a data point of the empirical function is determined using a median value of the actual astigmatism coefficient, and the empirical function is calculated using curve fitting of a plurality of the data points.