|- prescription = myope & astigmatism = astigmatic & tear production = normal -> lens = hard
|- age = young & astigmatism = astigmatic & tear production = normal -> lens = hard
|- prescription = hypermetrope & astigmatism = not astigmatic & tear production = normal -> lens = soft
|- age = young & astigmatism = not astigmatic & tear production = normal -> lens = soft
|- age = pre-presbyopic & astigmatism = not astigmatic & tear production = normal -> lens = soft
|- tear production = reduced -> lens = none
|- age = presbyopic & prescription = myope & astigmatism = not astigmatic -> lens = none
|- age = pre-presbyopic & prescription = hypermetrope & astigmatism = astigmatic -> lens = none
|- age = presbyopic & prescription = hypermetrope & astigmatism = astigmatic -> lens = none


|- -> lens = none
|  |- astigmatism = not astigmatic & tear production = normal -> lens = soft
|  |  |- age = presbyopic & prescription = myope -> lens = none
|  |- prescription = myope & astigmatism = astigmatic & tear production = normal -> lens = hard
|  |- age = young & astigmatism = astigmatic & tear production = normal -> lens = hard


|- -> lens = none
|  |  tear production = normal
|  |  |- astigmatism = astigmatic
|  |  |  |- prescription = myope -> lens = hard
|  |  |  |- age = young -> lens = hard
|  |  |- astigmatism = not astigmatic -> lens = soft
|  |  |  |- age = presbyopic & prescription = myope -> lens = none


|- -> lens = none
|  |- astigmatism = not astigmatic & tear production = normal -> lens = soft
|  |  |- age = presbyopic & prescription = myope -> lens = none
|  |  | prescription = myope & tear production = normal -> lens = hard
|  |  |  | age = young & tear production = normal -> lens = hard


|- -> lens = none
   |- tear production = normal
      |- astigmatism = astigmatic
      |  |- prescription = myope -> lens = hard
      |  |- age = young -> lens = hard
      |-  astigmatism = not astigmatic -> lens = soft
         |- age = presbyopic & prescription = myope -> lens = none

|- -> lens = none
   |- astigmatism = not astigmatic & tear production = normal -> lens = soft
      |- age = presbyopic & prescription = myope -> lens = none
      | prescription = myope & tear production = normal -> lens = hard
         | age = young & tear production = normal -> lens = hard

|- -> lens = none
   |- tear production = normal
      |- astigmatism = not astigmatic -> lens = soft
         |- age = presbyopic & prescription = myope -> lens = none
         | prescription = myope -> lens = hard
            | age = young -> lens = hard

