Limbal congestion is seen as a semi-circular zone of conjunctival/scleral congestion located on the limbal margin adjacent to the where the scleral landing zone bears down on the sclera.
Limbal congestion will be present when excessive PLTT is present in that meridian, causing increased capillary force suctioning the lens down on the sclera.
With OCT imaging the congestion area will appear as bunched up conjunctival tissue adjacent to the heavy bearing SLZ and has a similar appearance to the edge of an impact zone caused by a large object striking the ground.
Observe the PLTT profile with you slit lamp and look for a too thick PLTT profile. Perform over topography and a negative fluorescein test and see if sodium fluorescein floods into the lens bowl where the limbal congestion is present.
If too much PLTT is present in the zone of the limbal congestion, no sodium fluorescein flows in underneath the lens and over topography shows the flat axis in that meridian, the cause is excessive down pressure. Try to decrease the overall sag of the lens or steepen the BOZR in that meridian to reduce the excessive PLTT.
Note: In some cases, it will be necessary to use a toric back optic zone to achieve the desired results. For example in keratoconus, limbal congestion can often be seen at the 6 o’clock position. Steepening the overall BOZR can cause lens bearing in the horizontal meridian, so instead of steepening the overall BOZR, only the BOZR of the vertical meridian can be steepened, effectively decreasing the mid-peripheral PLTT in the vertical meridian without affecting the mid-peripheral PLLT of the horizontal meridian.