as can best be seen in fig1 horizontal microscissors 10 generally include a blade assembly 12 , an outer probe robe 14 , housing 16 , inner cutter robe 18 and a means for providing rotation of inner cutter rod 18 relative to outer probe robe 14 . in the preferred embodiment illustrated in fig1 rotation of inner cutter rod 18 is provided by spring 20 , return spring 22 , hub 24 and plunger 26 in a manner that will be described below . other methods of rotating inner cutter rod 18 , such as the assembly disclosed in u . s . pat . no . 5 , 263 , 958 ( deguillebon , et al .) or the bell and crank assembly disclosed in u . s . pat . no . 4 , 258 , 716 ( sutherland ) may also be used . as can be seen in fig2 and 3 , inner cutting blade 28 is attached to inner cutter robe 18 at the distal end of rod 18 . blade 28 may be attached to rod 18 by any suitable method but welding or laser welding is preferred . rod 18 is preferably made from 304 stainless steel with a nominal outside diameter of 0 . 0255 inches . blade 28 preferably is made from 420 stainless steel with a hardness of between 48 - 52 rc . blade 28 preferably is between 0 . 007 inches and 0 . 009 inches thick with a length l i of between 0 . 05 inches and 0 . 15 inches . as can be seen in fig2 blade 28 is attached to rod 18 at an angle α relative to the longitudinal axis of rod 18 of between 40 ° and 50 °, with 45 ° 30 &# 39 ; being preferred . as can be seen in fig3 cutting edge 30 of blade 28 lays at an angle β relative to the major axis of rod 18 ( rod 18 being elliptical in cross section when cut at an angle ). angle β preferably is between 30 ° and 40 ° with 35 ° 23 &# 39 ; being more preferred . as can be seen in fig4 and 5 , outer cutting blade 32 is attached to outer probe tube 14 at the distal end of tube 14 . blade 32 may be attached to tube 14 by any suitable method but welding or laser welding is preferred . tube 14 is preferably made from 304 stainless steel tubing with an outside diameter of between 0 . 0355 inches and 0 . 0360 inches and an inside diameter of between 0 . 0250 inches and 0 . 0265 inches . blade 32 preferably is made from 420 stainless steel with a hardness of between 48 - 52 rc . blade 32 preferably is between 0 . 007 inches and 0 . 009 inches thick with a length l o of between 0 . 08 inches and 0 . 14 inches . as can be seen in fig4 blade 32 is attached to tube 14 at an angle σ relative to the longitudinal axis of tube 14 of between 120 ° and 130 °, with 126 ° being preferred . as can be seen in fig5 cutting edge 34 of blade 32 lays at an angle γ relative to the major axis of tube 14 ( tube 14 being elliptical in cross section when cut at an angle ). angle γ preferably is between 5 ° and 10 ° with 7 ° 45 &# 39 ; being more preferred . as can be seen in fig1 and 6 , the difference in angles α and σ results in an inference fit between blades 28 and 32 that allows scissors 10 to make clean , smooth cuts in fibrous tissue . as seen in fig6 for ophthalmic applications , it is preferred that when blades 28 and 32 are in the open position , angle φ is at least 65 °, although larger or smaller angles may also be used . in use , rotation of rod 18 is accomplished through plunger 26 acting on hub 24 . as can be seen in fig1 proximal end 36 of rod 18 is fixed within hub 24 by any suitable method ( for example , gluing ). hub 24 contains ears or tabs ( not shown ) that ride within spiral slots 38 cut into the interior surface of throat 40 in plunger 26 . when plunger 26 is depressed , the tabs on hub 24 follows spiral slots 38 , causing hub 24 and rod 18 to rotate . this description is given for purposes of illustration and explanation . it will be apparent to those skilled in the relevant art that changes and modifications may be made to the invention described above without departing from its scope or spirit .
the present invention includes a stationary outer blade and a rotating inner cutting blade . a unique blade design and geometry allows clean , smooth cuts in fibrous tissue .