Table 1. Mensuration of Human Extraocular Muscles*

  INSERTIONS  
  Distance of Insertion Midpoint from Cornea  
  Adults Infants  
  Fuchs50 Weiss56 Apt64 Whitnall44 Weiss56  
Muscle Average Range Average Range Average Range Average of 12 authors Average Range Range of Insertion Distance from
Cornea Across Entire Tendon,
Greatest-shortest Motais52
Medial rectus 5.5 4.3–6.7 5.85 5.0–6.7 5.3 3.6–7.0 5.84 3.6 3.0–4.3 5.5–7.0
Inferior rectus 6.5 5.3–8.2 6.85 6.0–7.5 6.8 4.8–8.5 6.65 5.0 4.0–5.5 5.5–8.0
Lateral rectus 6.9 5.3–8.2 6.75 6.25–7.75 6.9 5.4–8.5 7.18 4.9 4.0–5.5 6.7–7.0
Superior rectus 7.7 6.8–9.0 8.01 6.75–9.0 7.9 6.2–9.2 7.88 5.8 5.0–7.0 6.5–11.0

  TENDON AT INSERTION†  
    Width  
    Adults Infants  
  Length Fuchs50
(emmetropic eyes)		 Weiss56 Adachi46 Weiss56  
Muscle Merkel43 Hesser48 Average Range Average Range Average Average Shape
Medial rectus 3.7 3.5 10.3 8.8–12.0 10.76 10.0–12.5 9.9 7.35 Straight or slightly convex forward
Inferior rectus 5.5 4.5 9.8 7.8–13.2 10.35 10.0–11.1 9.0 6.35 Convex forward, lateral part more anterior, frequently greater width lateral to vertical meridian
Lateral rectus 8.8 8.0 9.2 8.5–10.2 9.67 8.3–12.0 8.4 5.85 Straight
Superior rectus 5.8 5.0 10.6 8.5–13.2 10.75 10.0–11.25 10.0 6.95 Convex forward, lateral part more anterior, ⅔ of width lateral to vertical meridian

MUSCLES
Cross Section (mm2)
  Length Excluding Tendon Measured Maximum                
  Adults Infants Nakagawa53§     Ratio of Area to Lateral Rectus Area Volkmann55   Thickness Schneller66 Width Schneller66
Muscle Whitnall44 Volkmann55 Adachi46 Mühlendyck65 Schneller66 Male Female Calculated: Volkmann55‖ Infants Schneller66 Weight (g) Adult Infant Adult Infant
Medial rectus   40.8 40.7 22.6 28.0 31.0 28.1 17.39 10.27 1.04 0.75 1.69 1.3 10.3 7.9
Inferior rectus   40.0   17.8   31.1 28.3 15.85   0.95 0.67        
Lateral rectus   40.6 45.8 24.8 31.6 47.6 40.8 16.73 8.63 1.0 0.72 1.6 1.25 9.2 6.9
Superior rectus   41.8   23.5   24.0 20.9 11.34   0.68 0.51        
Superior oblique 40 32.2       10.0 11.4 8.36   0.50 0.29        
Inferior oblique 37 34.5       17.3 14.1 7.89   0.47 0.29        

  Angle to Vertical Plane (%)
Duke-Elder39		 Arc of contact (mm) Innervation: Action‖  
Muscle Average Range Zoth57 Cranial Nerve Primary Secondary
Medial rectus     6.33 III Adduction (99.9%) None
Inferior rectus 23   9.83 III Infraduction (74%) Excycloduction (16%)
            Adduction (10%)
Lateral rectus     13.25 VI Abduction (99.9%) None
Superior rectus 23   8.92 III Supraduction (76%) Incycloduction (16%)
            Abduction (8%)
Superior oblique 54 32–64 5.23 IV Incycloduction (64%) Infraduction (33%)
            Abduction (3%)
  51 33–57 16.74 III Excycloduction (59%) Supraduction (40%)
Inferior oblique           Abduction (1%)

  Number of Muscle Fibers¶  
    Children  
  Adults Infants 18 Months Size of Motor Unit**
Muscle Bors230 Kato51 Tergast229 Torre232 Goldschmidt47 Kato51 Goldschmidt47 Mühlendyck65 Tergast229 Torre232 Bors230 Goldschmidt47
Medial rectus 21,950 28,631   5,580   41,575 45,529 41,515 25,932 1:1.7   1:4.8 1:3.9
Inferior rectus 20,809 25,880 10,350     23,79     1:2.0   1:6.3  
Lateral rectus 27,214 35,058 11,965 24,400 31,639 22,608 28,075 23,327 1:3.3 1:4.9, 1:6 1:5.8 1:6.6
      19,760 31,735                
Superior rectus 20,156       28,084              
                      1:4.3  
Superior oblique   9,254 14,866       16,135       1:5.3,1:6.8 1:5.2  
Inferior oblique 17,557         15,488         1:7.0  

Nerves¶
Number of Nerve Fibers
      Bors230 Bjorkman & Wolfahrt231 Torre232
Nerve Rosenthal228 Tergast229 Proximal Distal Proximal Proximal Distal
III 15,000   13,763   24,000    
IV 1100–1200   1782   3400 2440  
            2100  
VI 2000–2500 3600 3862 4698 6600 5000 4650
            3300  


*Dimensions in millimeters; dimensions refer to adults unless otherwise specified.
†See Figure 6 for oblique muscles.
‡Maximum cross section occurs at the approximate level of the posterior pole of the globe.
§Based on length, weight, and assumed density.
‖Percentages calculated from Robinson.344
¶Double entries refer to two specimens.
**Number of muscle fibers per nerve fiber.