Pterygia (singular pterygium) are triangular, wing-shaped overgrowths of fibrovascular tissue on the front surface of the eye, extending from the conjunctiva on the whites of the eye over the transparent tissue of the cornea. Though pterygia are harmless and benign, they can cause some issues such as inducing astigmatism and decreased visual acuity, discomfort from recurrent inflammation, and cosmetic problems (who wants to have a wing growing across their eye?). While many patients are content to put up with a little pterygium, current treatment options for bothersome pterygia are centered mainly around surgical techniques.
Pterygia are found to be more prevalent in equatorial countries due to the association with UV exposure, and is more common in males and those with outdoor vocation or hobbies. In the US, the prevalence of pterygia varies from under 2% in the northern states, including northern California above 40°N latitude, to up to 15% in the more southern states. Southern Californian areas including Los Angeles and Ventura Counties find themselves closer to the higher rates of pterygia due to constant sun exposure and the number of surfers. Pterygia is also referred to as surfer’s eye.
The aim of pterygium surgery is to, of course, remove the pterygium but in a way that restores affected vision, improves cosmesis (bodily beauty), and results in as few complications as possible post-operatively, including the recurrence of another pterygium. The removal of the pterygium tissue not only uncovers the clear cornea but also leaves a defect in the affected conjunctiva over the whites of the eye. There are three types of surgical methods for removal of pterygia:
- Bare sclera technique, in which the pterygium is excised and that’s that
- Simple closure, using absorbable stitches to close the gap left in the conjunctiva
- Tissue grafting, which can involve a conjunctival autograft (taken from another section of the patient’s eye), or amniotic membrane transplantation (yes, that’s tissue taken from a donor human placenta after birth and stuck onto your eye. But hey, we’ve used placentas for weirder things) – the tissue grafts are then placed over the conjunctival defect and secured with a fibrin glue or sutures
Compared to bare sclera and amniotic membrane transplantation, conjunctival autografting has been shown to be associated with a lower rate of pterygium recurrence.
Lasers and Pterygia
In a novel study out of Singapore earlier this year, researchers investigated the use of the femtosecond laser for creating the conjunctival autograft to use in pterygium surgery. If femtosecond lasers sound familiar to you, your brain may be thinking back to the time you read about cataract extraction or laser refractive surgery.
The study compared the outcomes of pterygium surgery in three groups:
- an experienced ophthalmologist performing surgery with a femtosecond laser-assisted autograft
- an experienced ophthalmologist performing surgery with a manually prepared autograft using surgical scissors, and
- a group of trainee eye doctors given surgical scissors and told to hack away (presumably they had some degree of pterygium excision knowledge).
After a total of 196 eyeballs had been freed of their pterygia, several factors were examined. When the laser-assisted group was compared to the manual autograft group with the experienced ophthalmologist, surgical time and post-operative discomfort were similar, but both factors were found to be a little worse in the trainee group, which took longer to perform the surgery and resulted in higher discomfort scores. The researchers also found that complication rates between the laser-assisted and manual autograft groups performed by the experienced surgeon were not statistically different, but unsurprisingly was found to be significantly higher in the trainee group. However, in a pleasant turn of events, all groups, including the trainee group, experienced an improvement in astigmatism after surgery. After one year of follow-up, 7.7% of eyes having undergone pterygium excision with a trainee doctor experienced the regrowth of a pterygium, while recurrence rates were 2.5% for the femtosecond laser-assisted group and 3.8% in the experienced manual surgery group, not considered to be statistically significant.
Overall, conjunctival autograft harvesting using a femtosecond laser was found to be comparable to that using traditional manual techniques. The reliability, ultra-thinness, and accuracy of an autograft created with femtosecond laser were similar when manual conjunctival autografts were performed by an experienced ophthalmologist. All-importantly, the pterygium recurrence rates between laser-assisted and manually-prepared autograft techniques appear to be much the same.
The researchers behind the study suggested pterygium surgery with laser-assisted conjunctival autograft preparation could become an additional offering at eye clinics already equipped with a femtosecond laser. However, the cost-effectiveness of such a procedure, particularly when the results are comparable to cheaper manual techniques, still needs to be determined.
Dr. Michel, Chief Ophthalmologist at Ventura County Lasik uses a no-stitch technique to replace the Pterygium growth and prevent recurrence with normal tissue. His recurrence rate is superior at less than 1% which is why he’s known in Los Angeles and Ventura Counties as the king of Pterygium.
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