A 72-year-old male recently returned to our clinic for routine contact lens follow up reporting good success with the contact lens on his right eye. He had been fitted with a scleral lens six years ago following penetrating keratoplasty for endothelial dysfunction post-cataract surgery. Slit lamp examination showed moderate conjunctival injection with significant inferior conjunctival prolapse at 5 o’clock and 8 o’clock (Figure 1).
Conjunctival prolapse is a scleral lens complication that occurs when the conjunctival tissue migrates over the limbus and onto the peripheral cornea. In our experience, conjunctival prolapse occurs (in varying degrees) in approximately 20% to 30% of scleral lens wearers and has been noted in patients who have a wide range of corneal and/or ocular surface disease pathologies. The mechanisms for conjunctival prolapse are often multifactorial and may be related to the resting position of the lens, height differentials in the cornea/limbus, and pressure forces beneath the lens.
Today, we know that scleral lenses do not center on the eye; rather, they position slightly inferior and temporal. The malposition of scleral lenses is the result of gravitational forces secondary to the weight of the lenses, the “watermelon seed” effect of the upper lid pushing the lens downward, and, perhaps most importantly, observations of scleral shape indicating that the superior nasal sclera is higher compared to the inferior temporal sclera.
Therefore, when the lens is placed onto the eye, it lands first at the point of greatest elevation (superior nasal), which forces the lens toward the area of lesser resistance in the opposite inferior-temporal direction.
The anterior corneal shape can influence the location and extent of the prolapse. This is best seen with the elevation display map of the corneal topographer in which the blue areas represent the areas of greatest cornea depression and, thus, the greatest tear layer depth. It is in these depressed areas that the conjunctiva is most susceptible to prolapse as the tear layer depth attempts to equalize its pressure.
In certain susceptible patients, the conjunctiva will be “sucked” into any area in which significant lens clearance exists. Figure 1 demonstrates that the atmospheric pressure (outside of the scleral lens) is greater than the pressure beneath the lens is, which results in a closed negative pressure system (suction force).
This suction force is clearly illustrated by the fact that the conjunctiva recedes just seconds following lens removal (Figure 2) and then reoccurs seconds following the reapplication of the scleral lens (Figure 3). CLS