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Goblet cell changes may be linked to dry eye after LASIK
Researchers are exploring microkeratomes and suction rings and the damage they may cause to conjunctival goblet cells.
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LISBON — A transient decrease in the population of conjunctival goblet cells after LASIK may be associated with post-LASIK dry eye syndrome, a group of surgeons has suggested.
Ahmed Galal, MD, and colleagues at the Vissum Ophthalmological Institute in Alicante, Spain, noted a discrepancy between the time needed for severed nerves to regenerate and the duration of dry eye after LASIK.
“If the nerve is recovering between 3 and 6 months, we should have a full histopathology of the conjunctival surface at the corneal surface again after 6 months,” Dr. Galal said during a telephone interview with Ocular Surgery News. “So why are the patients still having dry eye after 6 months?”
To answer this question, the researchers conducted a prospective, controlled, noncomparative study of 22 eyes of 22 patients undergoing LASIK for the correction of myopia. Dr. Galal presented the results at the European Society of Cataract and Refractive Surgeons meeting.
The researchers performed conjunctival impression cytology at the superior bulbar conjunctiva and the inferior-temporal conjunctiva before LASIK and then 1 week and 1, 3 and 6 months postoperatively to assess the effect of the surgery on the population of conjunctival goblet cells.
The Moria LASIK 2 microkeratome with a –1 suction ring was used for all the procedures.
The samples were stained and examined using optical microscopy with 100X and 200X magnification to analyze cellular density, epithelial morphology and nuclear chromatin matter.
The mean preoperative goblet cell density was 485 cells/mm2. Postoperative samples showed a statistically significant decrease in mean goblet cell count to 312 cells/mm2, Dr. Galal said.
By 3 months after LASIK, the mean goblet cell count had increased to 430/mm2, still subnormal.
Dr. Galal said that 6 months after surgery, there was goblet cell reduction of up to 40% to 50%, a statistically significant difference from preop.
He said the study suggests that LASIK patients should continue using artificial tears for at least 6 months after surgery.
Cytology slides of conjunctival goblet cells at 40X magnification pre-LASIK (left) and post-LASIK (right). | |
Cytology slides of conjunctival goblet cells at 20X magnification pre-LASIK (left) and post-LASIK (right). Images: Galal A | |
More than nerve damage
Although this study was limited to one microkeratome and one type of suction ring, Dr. Galal said that goblet cell damage can be caused by any suction ring. He said the degree of damage depends on a variety of factors.
“I think the design of the suction ring might play some role here, as well as the time of application,” he said in an interview. “So the speed of the microkeratome is one factor.”
Dr. Galal said this study suggests that goblet cell damage occurs when vacuum is used to achieve suction on the globe. He said this theory has not been explored previously because others have shown that dry eye after LASIK is related to corneal nerve damage. He said the fact that neurotrophic dry eye is related to the severing of corneal nerves during LASIK flap creation is well accepted. But he said it is thought that the corneal nerves regenerate by 6 months after LASIK, so the persistence of dry eye syndrome beyond 6 months has been unexplained.
“We have only contemplated the nerve-cut theory, ignoring that most of those patients need to be treated up to 1 year even with the artificial tears,” he said.
Dr. Galal noted that more research is needed in this area. “We cannot be conclusive at this stage because we have to compare in a wide scale more patients, more microkeratomes, different suction rings, timing and pressure as well,” he said.
Future work
Further research into the role of goblet cells in post-LASIK dry eye is under way, according to Dr. Galal. He said the IntraLase laser keratome requires a longer suction ring application time than conventional microkeratomes, and the amount of goblet cell damage associated with IntraLase flap creation is the subject of a current investigation.
“We are essentially comparing the Moria M2 microkeratome to IntraLase because IntraLase needs 50 seconds or even 1 minute to perform the cut while the mechanical keratomes need about 10 seconds or even less,” he said.
Dr. Galal said it is hoped that future research at the Vissum Institute will lead to the development of a suction ring with a smaller area of contact with the surface of the globe.
“We are now in the process of designing this suction ring, and we will study the effects of this suction ring on the goblet cells. If it will induce less damage, this will support the theory,” he said. “It’s a large step on the way to study more and more about goblet cells.”
For Your Information:
- Ahmed Galal, MD, can be reached at Vissum, Insituto Oftalmologico de Alicante, Avda. de Denia, s/n, 03016 Alicante, Spain; 34-965-150-025; fax: 34-965-151-501; e-mail: dr_ahmgalal@hotmail.com.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.