New techniques have cut the recurrence rate in pterygium surgery from 50% to 5% or less.
New techniques and much higher success rates have lowered the threshold for performing pterygium surgery. What was once an inoperable pterygium—or a pterygium too small to consider—is now a candidate for surgical intervention. But there are still choices to be made. This article will summarize the progress made with pterygium removal and the choices that many surgeons have found to improve outcomes.
The incidence of pterygium varies greatly, from 1% to 12%, depending on geographic location, patient skin color, age, exposure to the sun, and other environmental factors. The same variables also affect the incidence of recurrence.
In the early days, the defect was surgically removed and the bare area allowed to heal by secondary intention. Unfortunately, recurrence was common—in up to 50% of cases—due to reexposure to the same causative factors, as well as the additional impact of the excision itself. Often the recurrence was worse than the primary pterygium. Modifications of the procedure designed to address recurrence generally failed.
Excision and Autografts
The choices surgeons make with respect to the procedure have a powerful influence on outcomes. The first area where surgeons have options involves the excision process. I advocate a conservative excision since it avoids the development of scar tissue, muscle restriction, and other problems (Figure 1). A video I developed (www.BetterEyeSurgery.com; Pterygium Surgical Techniques, April, 2009) illustrates this process and other techniques described in this article.
The introduction of conjunctival autografting, beginning with Ken Kenyon, MD, and his group in the 1980s, had a significant impact on recurrence rates.1,2 Compared to procedures that left a bare sclera, autografts reduced the recurrence rate from 50% to the range of 5% to 10%. The grafts were most frequently obtained from patients’ bulbar conjunctivae. I find that with this technique, healing is rapid and sutures can be removed within about 2 weeks. Limitations include significant discomfort, resulting from suture placement in a truamatized area already inflamed before surgery. An attempt to address this problem led to the next evolution in pterygium surgery: fibrin glue.
First described by Koryani, using fibrin adhesives in place of sutures to secure the conjunctival autograft led to a dramatic reduction in post-surgical pain.3 Fibrin glue had previously been used outside ophthalmology for over 25 years and in 11 million procedures. Although fibrin is derived from blood, there has been no report of viral or prion-mediated disease transmitted to a recipient in any of these procedures.
The benefits of fibrin glue can be dramatic. Even before I came to feel fully comfortable with my techique, the percentage of my early patients experiencing moderate to severe postoperative pain dropped from near 40% to just 4%. Phone calls from patients who were uncomfortable after surgery simply stopped.
Using Fibrin Glue
The adhesive typically comes in two components: thrombin and fibrinogen. Fibrinogen serves as a catalyst to accelerate the clotting reaction that binds the surfaces. An appealing feature of this adhesive is that surgeons can adust the speed of polymerization to match their surgical technique. If full strength thrombin is used, the glue will bond in 10 to 15 seconds. I find it best to dilute fibrinogen with balanced salt solution (BSS). Using a 10:1 dilution (ie, 9 parts BSS and 1 part thrombin) will significanlty slow polymerization. The fibrinogen can be diluted further, to 100:1, for a 2-minute cure time. Polymerization time is an important choice the surgeon must make.
In addition to selecting the ideal dilution ratio, I recommend using only a small volume of the combined materials, as excess adhesive will allow the autograft to slide too much. When I glue two tissue surfaces together, I apply just a drop or two of thrombin to the scleral surface and then dab it dry with a cotton tip applicator. Next, I put the fibrinogen on the stromal side of the graft. Finally, I flip the graft over, mixing the two components—just like putting peanut butter on one piece of bread, jelly on the other, and then putting them together. I then have 15 or 20 seconds to stretch the graft and oppose the edges where the pterygium was removed (Figure 2).
Once the graft tissue is positioned, I have learned to resist the temptation to make small adjustments. There is a tendency among surgeons, particularly eye surgeons, to want perfection. In this case, further manipulation of the graft will interfere with polymerization, weakening the bond without a significant benefit.
In my experience, the lowest recurrence rate comes when using conjunctiva for the graft. This was elegantly put by Ken Kenyon, who said, “The best substitute for conjunctiva is conjunctiva.” However, many surgeons find harvesting the conjunctival autograft to be very cumbersome. The ideal autograft must be very thin, so that it is cosmetically appealing and does not dislodge. This type of excision is technically difficult, but worth learning.
The use of amniotic membrane was an important innovation, especially for surgeons who previously used the bare sclera technique and were not yet comfortable with conjunctival autografts. Many companies provide good amniotic tissue. Bio-Tissue Inc. (Miami, FL) makes a cryopreserved membrane, and IOP Ophthalmics (Costa Mesa, CA) makes a freeze-dried version. The IOP product is a little less expensive, and there are no storage issues or refrigeration requirements. In my experience, both types of materials work equally well.
The amniotic graft should be larger than the conjunctival defect by 3 to 4 mm. When excising the pterygium, I cauterize and open a space underneath the surrounding conjunctiva to tuck in the amniotic tissue. It is important to remember that recurrent pterygia do not arise from the bare scleral bed where the original pterygium was removed. Rather, recurrences arise from the surrounding subconjunctival Tenon’s fascia, and it is this location that needs attention. When I position an amniotic membrane graft, I tuck it in 3 to 4 mm on all sides beyond the margin of the conjunctival defect.
For additional protection, mitomycin C (MMC) can be used. I apply MMC (0.02%) for 1 to 3 minutes before placing the graft, minimizing exposure of the bare scleral surface to MMC and rinsing with about 30 mL of BSS after application. The use of an amniotic graft plus MMC lessens the risk of corneal and scleral melts, with outcomes similar to what we see with conjunctival autografts—a recurrence rate of about 5%.
I currently use a combination of amniotic membrane and conjunctival autograft. Using the amniotic tissue is a preventive measure: it is used for the same reason as MMC but achieves significantly lower recurrence rates in my own experience.
To begin the amniotic membrane plus conjunctival autograft technique, I remove the pterygium in the standard fashion. A piece of amniotic membrane is prepared either as a long, straight strip or in the shape of the letter C (“C-Shaped Technique”). This strip is tucked into the subconjunctival space surrounding the excision site (Figure 3). A little fibrin glue can be placed underneath the conjunctiva to help hold it in place temporarily. The conjunctival autograft is prepared and placed as described earlier. The entire technique has reduced the rate of recurrence, from about 5% with conjunctival autografts alone, to less than 1%.4
This approach works well because it combines the advantages of both conjunctival autografting and amniotic membrane. The combinination is more time-consuming and surgically demanding, but it is the best procedure I have used.
Preparation of the Autograft
The preparation of the conjunctival autograft has been influenced by the use of fibrin adhesives. The surgical technique is best communicated by watching the video cited above and requires significant practice. However, I can offer a few tips and choices. I cut the tissue to the same shape and size as the scleral defect, cutting towards the limbus, on both sides. I also like to dissect into the peripheral cornea in order to include limbal stem cells. There is some debate on whether this is effective, but I believe it is.
After I excise the graft, I slide the tissue over the adjacent pterygium excision site, so that the limbus of the graft and excision site align. I apply the adhesive components: thrombin on the bare sclera and fibrinogen on the graft. I then invert the graft, setting it in place and mixing the fibrin glue components. I smooth it out with blunt forceps and use a squeegee motion to stretch the graft into place.
Impact on Vision
Occasionally, we see a pterygium patient who has a small amount of astigmatism that worsens once the tissue is removed. This appears to be related to some corneal remodelling caused by the presence of the pterygium. In some instances, a patient has had naturally occuring astigmatism whose impact was lessened by the pterygium. Ironically, once the pterygium was removed, the eye returned to its native astigmatic state.
When I see a patient who has a large pterygium and surprisingly good vision, I make it a point to let them know that their vision may be negatively impacted, if only temporarily. Generally, these patients have good long-term results after surgery.
It is vital to communicate clearly with patients about appropriate expectations of visual outcomes after pterygium removal. Patients must understand all risks involved, including the possibility of recurrence regardless of the technique used. The consent process should ensure patients understand that multiple factors, including future environmental exposure, impact long-term outcomes.
Every patient also deserves to know when the surgeon plans to use fibrin adhesives. Some people may have religious objections to products derived from blood, or hypothetical concerns about blood-borne disease. Surgeons needs to disclose all these factors to be fully honest, and patients need to know that perfection is not a likely outcome.
THE BOTTOM LINE
Choices in surgical technique can have an enormous impact on the short- and long-term success of pterygium removal. Recurrence rates plummet when surgeons who use a bare sclera technique convert to using a conjunctival autograph, and surgeons using conjunctival autograft will find it advantageous to add subconjunctival amniotic membrane.
John A. Hovanesian, MD, FACS, practices at Harvard Eye Associates, Laguna Hills, CA. He is a clinical assistant professor at the UCLA Jules Stein Eye Institute and a consultant to IOP Ophthalmics. Medical writer Jerry Stein, PhD, assisted in the preparation of this manuscript.
1. Thoft, RA. Conjunctival transplantation. Arch Ophthalmol. 1977;95:1425-7.
2. Herman WK, Doughman DJ, Lindstrom RL. Conjunctival autograft transplantation for unilateral ocular surface diseases. Ophthalmology. 1983;90(9):1121-6.
3. Koranyi G, Seregard S, Kopp ED. The cut-and-paste method for primary pterygium surgery: long-term follow-up. Acta Ophthalmologica Scandinavica. 2005;83(3):298-301.
4. Hovanesian J. Results of pterygium excision using amnionic membrane beneath the healthy conjunctiva surrounding a conjunctival autograft. Presented at the American Society of Cataract and Refractive Surgery Meeting; April 4-9, 2008; Chicago, IL.