I read with great interest the paper by Ooka and associates, in which they correlated the restored external limiting membrane (ELM) and photoreceptor inner and outer segment (IS/OS) junction after surgery for macular hole (MH). They suggested that the restoration of the ELM was associated closely with that of the IS/OS junction and presented representative cases with serial images from spectral-domain optical coherence tomography examinations showing restoration of the ELM and IS/OS junction.
I agree with their conclusion that the restoration of the ELM is associated closely with that of the IS/OS junction. However, the serial optical coherence tomography images in their Figure 3, representing the timed process of restoration, raised some questions. In their report, optical coherence tomography images showed a complete restoration of both the ELM and the IS/OS junction at 3 or 6 months after surgery. The restoration included the lucent area under the restored ELM, which also has been called an outer foveolar defect , outer foveal defect , and foveal cyst . In addition to the restoration of the ELM and IS/OS junction, however, their serial images seemed to show other characteristic changes after the surgery, including changes in foveal contour. In the left column in their Figure 3, the distance between nerve fiber layers seemed to increase with a complete restoration of the ELM and IS/OS junction at 3 months after surgery, and the inner retinal margin was distorted at 6 months after surgery. In the right column, a defect in the nerve fiber layers seen at 1 month was restored with partial restoration of IS/OS junction at 3 months after surgery, and foveal center thickness seemed to be thickened with a complete restoration of IS/OS junction at 6 months. A change in foveal contour, such as widening or thickening of the foveal center, may be assumed to be the result of the regeneration or rearrangement of retinal layers, including the outer nuclear layer, as was restoration of the defect on nerve fiber layers and development of a distorted inner retinal margin. These findings may provide another insight into the healing process after MH surgery.
Although the changes in foveal contour shown on the serial images, representing complete restoration of the outer foveolar defect, may be real, these changes also may be explained by the fact that the serial images may not have been obtained in the same area. In their prospective study, they cautiously may have selected the representative images of the thinnest area of the fovea because the thinnest area may be in the most approximated retina. However, this does not guarantee that the serial images were obtained at the same location. In addition, 3 or 6 months seems too short of a time for the outer foveolar defect to have healed completely, although recent observations have been unclear as to how long the defect persists after surgery.