Controlled depth penetrant apparatus and method

A surgical instrument for performing a radial keratotomy on the eye of an animal, whereby the cornea of said eye is penetrated inwardly from its outer surface while leaving adjacent to its inner surface an unpenetrated portion thereof, comprising:

• a cutting blade for penetrating said cornea;
• driving means connected to said cutting blade for advancing or retracting said cutting blade relative to the outer surface of said cornea;
• depth sensing means for determining the depth of penetration of said cutting blade into said cornea relative to said outer surface and generating a signal proportional thereto;
• thickness sensing means for determining the thickness of said cornea between the outer and inner surfaces of said cornea at a point directly adjacent to said thickness sensing means, which thickness sensing means determine the thickness of said cornea at substantially the point of penetration of said cutting blade and generate a signal proportional thereto, and;
• comparator means connected to said depth sensing means, thickness sensing means, and driving means, which compare said signal proportional to the depth of penetration of said cutting blade into said cornea relative to said outer surface to an input signal proportional to the desired unpenetrated thickness adjacent to the inner surface of said cornea and to said signal proportional to the thickness of said cornea at substantially the point of penetration of said penetrant means, said point serving substantially as a common reference point for said depth sensing means and said thickness sensing means which comparator means thereafter provide an output signal which controls said driving means so that the penetration of said cutting blade inwardly from the outer surface of said cornea is adjusted so as to leave unpenetrated a portion of said cornea adjacent the inner surface.

A method of penetrating a material having an outer surface and a substantially inaccessible inner surface with penetrant means, wherein said penetration is effected inwardly from said outer surface while leaving adjacent to said inner surface an unpenetrated portion of said material, comprising the steps of:

• determining the thickness of said material between the outer and inner surfaces thereof by thickness sensing means at a point directly adjacent to said thickness sensing means, said point being substantially the point of intended penetration of said penetrant means, and generating a signal proportional thereto;
• penetrating said material with said penetrant means;
• advancing or retracting said penetrant means relative to the outer surface of said material by driving means connected thereto;
• determining the depth of penetration of said penetrant means into said material relative to said outer surface thereof by depth sensing means and generating a signal proportional thereto, and;
• comparing said signal proportional to the depth of penetration of said penetrant means into said material relative to said outer surface thereof to an input signal proportional to the desired unpenetrated thickness adjacent to the inner surface of said material and to said signal proportional to the thickness of said material at substantially the point of penetration of said penetrant means said point serving substantially as a common reference point for said depth sensing means and said thickness sensing means by comparator means, and thereafter controlling said driving means so that the penetration of said penetrant means inwardly from the outer surface of said material is adjusted so as to leave unpenetrated a portion of said material adjacent the inner surface.

A surgical method for performing a radial keratotomy on the eye of an animal wherein the cornea of said eye is penetrated inwardly from its outer surface with a cutting blade while leaving adjacent to its inner surface an unpenetrated portion of said cornea and a plurality of incisions are made which incisions radiate from the anterior pole to the limbus of said cornea, said incisions being effected by the steps of:

• determining the thickness of said cornea between the outer and inner surfaces thereof by thickness sensing means at a point directly adjacent to said thickness sensing means, said point being substantially the point of intended penetration of said cutting blade and generating a signal proportional thereto;
• penetrating said cornea with said cutting blade;
• advancing or retracting said cutting blade relative to the outer surface of said cornea by driving means connected thereto;
• determining the depth of penetration of said cutting blade into said cornea relative to said outer surface thereof by depth sensing means and generating a signal proportional thereto, and;
• comparing said signal proportional to the depth of penetration of said cutting blade into said cornea relative to said outer surface thereof to an input signal proportional to the desired unpenetrated thickness adjacent to the inner surface of said cornea and to said signal proportional to the thickness of said material at substantially the point of penetration of said cutting blade said point serving substantially as a common reference point for said depth sensing means and said thickness sensing means by comparator means, and thereafter controlling said driving means so that the penetration of said cutting blade inwardly from the outer surface of said cornea is adjusted so as to leave unpenetrated a portion of said cornea adjacent the inner surface.