Gonioscopy visible structures in anterior chamber

I.    Angle structures ( most anterior to most posterior)
  A.    Schwalbe's line (SL)
    i.    Termination of Descemet's membrane
          Where corneal scleral meshwork terminates anteriorly 
    ii.   Looks like a thin, glistening white line
    iii.  Posterior embryotoxin
          Anteriorly displaced SL visible with the slit lamp 
    iv.   Pigment can accumulate at ledge of Schwalbe's line
          Ledge due to different radii of curvature 
          between the angle recess and internal cornea 
    v.    Sampaolesi's Line
      a.    Pigment on the angle wall in a scalloped pigmented wave
      b.    Located above SL -- Usually in the inferior angle 
      c.    Associated with pigment dispersion or exfoliation syndrome 
      d.    Differentiate between Sampaolesi's line and pigmented SL 

  B.    Trabecular meshwork (TM)
    i.    Translucent and light grey
    ii.   Darkens with age
    iii.  Anterior portion (nonfiltering portion)
      a.    Runs from Descemet's to the area anterior to Schlemm's Canal 
      b.    Nonfunctioning portion
    iv.   Posterior portion (filtering portion) -- covers Schlemm's Canal
    v.    Coloration
      a.    Usually translucent gray
      b.    May have pigmentation
        1.    Usually in the inferior and nasal quadrants
        2.    In older patients, due to pigment epithelium becoming free over
              time.  Large pieces of pigment are trapped on surface of TM 
        3.    In heavily pigmented eyes, filtering portion is often pigmented.
              May be darker than the rest of the TM forming a two-toned TM
        4.    If pigment is significant, especially if superior GREATER than 
              inferior quadrants, suspect
          a.    Exfoliation syndrome
          b.    Pigment dispersion syndrome
          c.    Previous inflammation
    vi.   Schlemm's Canal (SC) or Canal of Schlemm
      a.    Covered by the filtering portion of the TM
            May be seen as a light grey line in translucent TM
      b.    Most pigmented band of TM (post 2/3 of TM) corresponds to
            canal of Schlemm
      c.    Will occasionally fill with blood when pressing on globe
            Only clearly visible if filled with blood
        1.    No blood if pressure within the canal is lower than the
              pressure in the anterior chamber
        2.    Pressure increased by increased pressure on goniolens
              (induced by practitioner)
        3.    Increased pressure by the patient (squeezing lids)
          a.    When pressure in the intrascleral circulation is higher 
                than in the canal of Schlemm, blood refluxes into the canal 
          b.    Increase in venous pressure occurs when patient squeezes
                lids against the lens then relaxes and blood enters SC 
        4.  Relax pressure on gonio lens and blood will dissipate

  C.    Scleral spur (SS)
    i.    Represents the continuation of the sclera into the AC
      a.    Attached anteriorly to the TM and posteriorly to the sclera
      b.    SC lies just anterior to SS
      c.    If see SS, means the filtering TM is not obstructed
    ii.   Appearance:  Thin, whitish band

  D.    Ciliary body band (CBB)
    i.    Coloration
      a.    In light eyes:  gray white
      b.    In dark eyes:  brown or charcoal grey
    ii.   CBB is broader inferiorly and temporally
      a.    May account for why AC is wider inferior and temporally

  E.    May see iris processes in some angles
    i.    Insert from iris to post Trabecular Meshwork
    ii.   Iris processes
      a.    Originate from the iris surface and bridge the angle
        1.    Usually attach at the level of the TM
        2.    Normal occurrence
        3.    Etiology:  mesodermal remnants
      b.    Appearance and frequency
        1.    Fine, lacy fibers or coarse dense network
        2.    Pigmentation
          a.    Dark irides:  brown or yellowish
          b.    Light irides:  gray or white
        3.    Appear more frequently in younger patients with dark irides
        4.    Become more prominent with age (due to accumulation of pigm.) 
        5.    Most dense nasally
        6.    The two eyes tend to mirror each other
      c.    Differentiate between iris processes 
            and peripheral anterior synechia (PAS) 
        1.    PAS
          a.    Characteristic of post-inflammatory conditions, 
                such as uveitis and acute angle closure 
          b.    Full thickness attachments of actual iris tissue that
                are attached to the angle wall
          c.    Appearance:  more uniform and solid than processes
          d.    With compression gonioscopy
            1.    Synechia will continue to hold against the angle wall
                  (tenting of the synechia)
            2.    Processes becomes lacier and will see wall behind them 
          e.    An abnormal occurrence and interferes with aqueous outflow 
                Iris processes do not interfere with aqueous outflow 
          f.    Location
            1.    Primary closure glaucoma:  PAS usually located in
                  superior angle
            2.    Inflammatory disease:  PAS usually located in inf. angle 

  F.    Angle depth
    i.    Inferior angle is widest
    ii.   Superior angle is the narrowest
    iii.  Normal difference in angles between quadrants 
          is only half a structure

II.   Recording
  A.    Angles
    i.    Use X diagram
    ii.   Record the most posterior structure seen - CBB, SS, TM, SL or none.

  B.    Interpretation of angles
    i.    If less than 1/2 of the TM is visible, 
          the patient is at risk for angle closure
    ii.   If CBB is seen, the angle is wide open
    iii.  If no structures are visible, the angle is closed
    iv.   % of narrow angles in the general population is 2 - 5%
      a.    Occludable angles is 1.64%
      b.    Angle closure glaucoma is 0.09%
    v.    Angle recession
      a.    Due to blunt trauma to the eye
      b.    Most common change is a tear in the ciliary body
      c.    Causes a posterior displacement of the CB along the iris root
      d.    Will see an irregular widening of the CBB
            and may also have color and texture changes
      e.    Diagnosis by case hx and comparison to the fellow eye
      f.    Due not usually see a change in IOP until years later
            Due to damage to the functioning of the ciliary body processes
    vi.   Plateau iris
      a.    Relatively rare type of primary angle closure glaucoma
      b.    More often in younger patients
      c.    On slit lamp, will have a normal or deep central anterior
            chamber depth and will also have a shallow peripheral angle and 
            flat iris contour 
      d.    Angle closure may be precipitated  
            if predisposed eye is widely dilated
        1.    Angle closes off due to folding of iris root against the wall
              of the endothelium which blocks the trabecular meshwork
      e.    Flashlight (shadow) test - Angle will look open
    vii.  Pupillary block
      a.    Due to apposition of iris to the crystalline lens when the
            iris is mid-dilated and somewhat lax
      b.    Pressure increase in posterior chamber forces iris root
            against the anterior wall of the angle
      c.    Aqueous cannot move from post. chamber to the ant. chamber
      d.    Occurs when the iris is recovering from dilation 
            (may happen hours after the gtts are instilled)

  C.    Pigmentation - Grade 0 to 4
        4: dense     3: moderate     2: light     1: trace     0: none
        Estimate an average if pigmentation is in sections

  D.    Record presence of iris processes in the appropriate quadrant

  E.    Record any anomalies in the appropriate quadrant