MIAMI Internal limiting membrane peeling is not essential to successful macular hole surgery and may even be detrimental to final visual acuity when attempted too aggressively, according to a study of 193 eyes (183 patients).
Recently, internal limiting membrane (ILM) peeling has been advocated to improve the results of macular hole surgery, said William E. Smiddy, MD, a professor of ophthalmology at Bascom Palmer Eye Institute at the University Miami School of Medicine. However, there is a high success rate reported in numerous surgical series in which ILM peeling was not pursued or, earlier back, even considered.
The distribution for the current study is comparable to other reported series of predominantly stage III and IV holes, and there was an appreciable proportion of formerly operated holes. Visual acuity preoperatively was 20/60 or worse in 96% of cases.
Dr. Smiddy performed all operations. I attempted to remove the ILM from around the hole in all cases, he said. Long-acting gas and a 2-week face-down period were also criteria. Mean follow-up was 14 months.
The ILM was completely removed in 23% of patients and partially removed in 43%, but in the remaining 34% it was only dissected without successful removal, Dr. Smiddy said. The degree of ILM peeling did not correlate with the initial visual acuity, the stage and duration of the macular hole or the presence of an operculum.
Primary anatomic success was ac hieved in 93% of patients and an additional 4% underwent successful re oper- ation. The rate of anatomic success was actually slightly higher in the patients who had dissection only, and this difference was statistically significant, he said.
Reflecting previous reports, anatomic success correlated with better preoperative visual acuity and shorter duration of the macular hole. Anatomic success did not correlate with the process of an operculum, the stage of the hole or the extent of any commensurate petechial hemorrhage.
Visual results were comparable to previous studies. In total, 76% of anatomically successful patients re gained two or more lines, of whom 60% regained 20/50 or better. The visual acuity increase and rate of 20/50 or better correlated with better preoperative vision and shorter duration, Dr. Smiddy said.
In contrast, when considering only the anatomically successful cases, the degree of ILM peeling did not correlate with the mean final visual improvement or poor final visual acuity. But the degree of ILM peeling did correlate at the endpoint of final visual acuity being greater than or equal to 20/50.
One deficiency of the study was that the technique used during the duration of the study did not allow for reproducible ILM peeling and removal. More importantly, though, there were not any no-touch control ILM peeling cases, Dr. Smiddy said. The series also included a higher proportion than usual of cases which had failed previous macular hole surgery. This distribution may have skewed the results.
In any event, the role of the internal limiting membrane in the pathogenesis of macular holes may be passive. The membrane acts as a broken barrier that may be degenerative and allow access of glial cells to the retinal surface. It is also a template for the migration, contraction and proliferation of those glial elements onto the ILM to enlarge the hole, Dr. Smiddy said.
Macular hole surgery may conceivably work by mimicking the occult stage of the hole. Redirecting the glial migration across a template of an air or oil interface reverses the effects of the previous glial contraction. Thus a possible rationale for ILM peeling may be to reduce the centripetal forces and also to stimulate gliosis in a dose that perhaps is somewhat reproducible quantitatively, he said.
Cases in the current series for which the ILM peel was unsuccessful may have sustained more surgical trauma from prolonged attempts to develop the edge of the hole and therefore resulted in more gliosis, accounting for a higher anatomic success rate but a lower visual success rate. Conversely, the higher rate of visual acuity at the endpoint of 20/50 or better in a successfully peeled group may reflect the opposite. This rate, though, is less than for a retinal trauma, Dr. Smiddy said.
Nonetheless, we had a very good success rate overall. Barring a truly controlled study requiring over 400 patients, a reasonable consensus is to attempt ILM peeling without making overly aggressive maneuvers that risk damage to the inner retina, he said.
For Your Information:
- William E. Smiddy, MD, can be reached at Bascom Palmer Eye Institute, 900 Northwest 17th St., Room 255, Miami, FL 33136; (305) 326-6172; fax (305) 326-6417; e-mail: email@example.com.