Method of analyzing astigmatism and apparatus for performing corneal surgery

A method of correcting astigmatism of the eye of a patient comprising the steps of:

• measuring pre-operative astigmatism of the eye of a patient to obtain parameters of a magnitude and axis of astigmatism in a 0.degree. to 180.degree. range;
• defining an aimed astigmatism including a magnitude and axis, the axis being an angle presented in a 0.degree. to 180.degree. range;
• effecting a surgical treatment on the cornea of an eye of the patient based on the measured parameters of pre-operative astigmatism and aimed astigmatism;
• measuring an achieved astigmatism following the surgical treatment which differs from said aimed astigmatism, the achieved astigmatism having a magnitude and axis, the axis being an angle presented in a 0.degree. to 180.degree. range;
• doubling the angles of the axes of said pre-operative astigmatism, said aimed astigmatism and said achieved astigmatism to convert the axes to a 360.degree. range;
• calculating an aimed induced astigmatism vector in said 360.degree. range which is the vector sum of the aimed astigmatism and the pre-operative astigmatism in said 360.degree. range, calculating a surgically induced astigmatism vector which is the vector sum of the achieved astigmatism and the pre-operative astigmatism in said 360.degree. range, and calculating a difference vector in said 360.degree. range as the vector difference between said aimed induced surgical vector and said surgically induced astigmatism vector, said difference vector representing the vector difference between the aimed astigmatism and the achieved astigmatism in said 360.degree. range;
• and
• halving the angles of the aimed induced astigmatism vector, the surgically induced astigmatism vector and the difference vector to return the angle values to a 0.degree. to 180.degree. range and
• utilizing the magnitude and angle of said difference vector in said 0.degree. to 180.degree. range as surgical parameters to obtain the aimed astigmatism.

An apparatus for performing corneal surgery comprising:

• means for performing surgery on a patient's cornea;
• control means for controlling the means for performing surgery;
• and
• processing means having an input for receiving magnitude and angle values of measured pre-operative astigmatism of an eye of a patient, magnitude and angle values of aimed astigmatism to be achieved following surgery, and magnitude and angle values of surgically induced astigmatism after a prior surgery intended to correct said pre-operative astigmatism, said processing means being operative to determine surgical parameters to treat the cornea of the eye of the patient to achieve said aimed astigmatism by vectorially adding the pre-operative astigmatism and the aimed astigmatism to obtain an aimed induced astigmatism vector;
• vectorially adding the pre-operative astigmatism and said surgically induced astigmatism to obtain a surgically induced astigmatism vector, and
• vectorially subtracting the surgically induced astigmatism vector from the aimed astigmatism vector to obtain a difference vector which represents the vector difference between said aimed astigmatism and said surgically induced astigmatism,
• said processing means further having an output at which magnitude and angle values of said difference vector are provided as output signals, said output of the processing means being connected to said control means for controlling the surgery on the patient's cornea based on said output signals.

A method of performing surgery on the cornea of an eye of a patient to correct astigmatism of the eye, said method comprising:

• examining an eye of a patient for astigmatism and evaluating the astigmatism in terms of magnitude at a steepest axis,
• defining a non-zero aimed astigmatism to remain following surgery,
• vectorially adding the evaluated pre-operative astigmatism and the non-zero aimed astigmatism to obtain a vector representing dioptric force and axis intended to achieve an aimed induced astigmatism vector, and
• surgically effecting relative steepening of the cornea in a direction and magnitude corresponding to the aimed induced astigmatism vector.

A method of performing surgery on the eye of a patient to correct astigmatism of the eye, said method comprising:

• examining an eye of a patient for astigmatism and evaluating the astigmatism in terms of magnitude at a steepest axis,
• defining an aimed astigmatism to remain following surgery,
• surgically applying a dioptric force along an axis to produce a surgically induced astigmatism in the eye,
• vectorially adding the evaluated pre-operative astigmatism and the surgically induced astigmatism to obtain a surgically induced astigmatism vector,
• vectorially adding the aimed astigmatism and the evaluated pre-operative astigmatism to obtain an aimed induced astigmatism vector, and
• vectorially subtracting the aimed induced astigmatism vector from the surgically induced astigmatism vector to produce a difference vector having parameters of magnitude and direction for effecting a second surgical application of dioptric force and axis to achieve said aimed astigmatism.