Spectral imaging of the area of internal limiting membrane peeling

Imaging the Area of Internal Limiting Membrane Peeling after Macular Hole Surgery

Background: The aim of this study was to compare en-face optical coherence tomography (OCT) imaging and confocal scanning laser ophthalmoscopy (cSLO) imaging at different wavelengths to identify the internal limiting membrane (ILM) peeling area after primary surgery with vitrectomy and ILM peeling for macular hole (MH). Methods: In total, 50 eyes of 50 consecutive patients who underwent primary surgery with vitrectomy and ILM peeling for MH were studied. The true ILM rhexis based on intraoperative color fundus photography was compared to the presumed ILM rhexis identified by a blinded examiner using en-face OCT imaging and cSLO images at various wavelengths. To calculate the fraction of overlap (FoO), the common intersecting area and the total of both areas were measured. Results: The FoO for the measured areas was 0.93 ± 0.03 for en-face OCT, 0.76 ± 0.06 for blue reflectance (BR; 488 nm), 0.71 ± 0.09 for green reflectance (GR; 514 nm), 0.56 ± 0.07 for infrared reflectance (IR; 815 nm) and 0.73 ± 0.06 for multispectral (MS). The FoO in the en-face OCT group was significantly higher than in all other groups, whereas the FoO in the IR group was significantly lower compared to all other groups. No significant differences were observed in FoO among the MS, BR, and GR groups. In en-face OCT, there was no significant change in the ILM peeled area measured intraoperatively and postoperatively (8.37 ± 3.01 vs. 8.24 ± 2.81 mm2; p = 0.8145). Nasal-inferior foveal displacement was observed in 38 eyes (76%). Conclusions: En-face OCT imaging demonstrates reliable postoperative visualization of the ILM peeled area. Although the size of the ILM peeling remains stable after one month, our findings indicate a notable inferior-nasal shift of the overall ILM peeling area towards the optic disc.

Spotlight on the Internal Limiting Membrane Technique for Macular Holes: Current Perspectives

Pars plana vitrectomy has become the standard procedure for primary macular holes (MHs) repair, including the removal of the posterior cortical vitreous, the stripping of eventual epiretinal membranes, and finally an intraocular gas tamponade. During this procedure, peeling the internal limiting membrane (ILM) has been proven to increase closure rates and avoid postoperative reopening in several researches. In fact, even in large MHs more than 400 µm, the advantage of peeling off the ILM was highlighted by better anatomical closure rates. Nevertheless, some authors suggested that ILM peeling is not always essential, because it generates various side effects in retinal structure and function. Furthermore, the ideal amount of ILM peeling and the most effective strategies for removing the ILM are still subject of research. Different surgical modifications have been reported as alternatives to traditional peeling in certain clinical settings, including ILM flaps, ILM scraping, and foveal sparing ILM peeling. As regards large MHs, the introduction of ILM inverted flap appeared as a game changer, offering a significantly higher >90% closure rate when compared to traditional ILM peeling. Modifications to inverted ILM flap procedures have been claimed in recent years, in order to define the best area and direction of ILM peeling and its correlation with functional outcomes. Moreover, several innovations saw the light in the setting of recurrent MHs, such as ILM free flap transposition, inverted ILM flap combined autologous blood clot technique, neurosensory retinal flap, and human amniotic membrane (HAM) plug, claiming higher anatomical success rate also in those complex settings. In conclusion, the aim of this review is to report how the success rate of contemporary macular surgery has grown since the turn of the century, especially for big and chronic MHs, analyzing in which way ILM management became a crucial point of this kind of surgery.

Cones in ageing and harsh environments: the neural economy hypothesis

PURPOSE

Cones are at great risk in a wide variety of retinal diseases, especially when there is a harsh microenvironment and retinal pigment epithelium is damaged. We provide established and new methods for assessing cones and retinal pigment epithelium, together with new results. We investigated conditions under which cones can be imaged and could guide light, despite the proximity of less than ideal retinal pigment epithelium.

RECENT FINDINGS

We used a variety of imaging methods to detect and localise damage to the retinal pigment epithelium. As age-related macular degeneration is a particularly widespread disease, we imaged clinical hallmarks: drusen and hyperpigmentation. Using near infrared light provided improved imaging of the deeper fundus layers. We compared confocal and multiply scattered light images, using both the variation of detection apertures and polarisation analysis. We used optical coherence tomography to examine distances between structures and thickness of retinal layers, as well as identifying damage to the retinal pigment epithelium. We counted cones using adaptive optics scanning laser ophthalmoscopy. We compared the results of five subjects with geographic atrophy to data from a previous normative ageing study. Using near infrared imaging and layer analysis of optical coherence tomography, the widespread aspect of drusen became evident. Both multiply scattered light imaging and analysis of the volume in the retinal pigment epithelial layer from the optical coherence tomography were effective in localising drusen and hyperpigmentation beneath the photoreceptors. Cone photoreceptors in normal older eyes were shorter than in younger eyes. Cone photoreceptors survived in regions of atrophy, but with greatly reduced and highly variable density. Regular arrays of cones were found in some locations, despite abnormal retinal pigment epithelium. For some subjects, the cone density was significantly greater than normative values in some retinal locations outside the atrophy.

SUMMARY

The survival of cones within atrophy is remarkable. The unusually dense packing of cones at some retinal locations outside the atrophy indicates more fluidity in cone distribution than typically thought. Together these findings suggest strategies for therapy that includes preserving cones.

The relationship between a dissociated optic nerve fibre layer appearance after macular hole surgery and Muller cell debris on peeled internal limiting membrane

PURPOSE

A dissociated optic nerve fibre layer (DONFL) is a characteristic change noted in inner retinal morphology after internal limiting membrane (ILM) peeling. It is thought to be due to trauma to Muller cells as the ILM is peeled from their attached end plates. In this study, we aimed to determine the extent and size of Muller cell debris on the retinal side of excised ILM and assess whether this correlated with the extent of DONFL observed postoperatively.

METHOD

Prospective single centre study of a consecutive series of patients undergoing macular hole surgery. Transmission electron microscopy of the ILM was used to assess Muller cell debris and postoperative spectral domain optical coherence tomography (SD-OCT) to assess the extent of DONFL. A variety of other pre- and postoperative features was also included.

RESULTS

Thirty-nine patients were analysed. There were retinal dimples characteristic of DONFL detected on SD-OCT in all 39 eyes. The portion of the retinal side of the ILM specimen covered by cellular debris ranged from 12% to 49%, with a median of 28%. Using linear regression, the percentage of retinal debris, the size of the debris and the postoperative visual acuity were significantly positively associated with the DONFL score. The total R squared for the model was 63.9%.

CONCLUSION

The extent of DONFL observed postoperatively can be partly explained by the amount of retinal side cellular debris on the retinal side of the peeled ILM. Surgical strategies which minimize this material could reduce the extent of DONFL.

Complications of Macular Peeling

Macular peeling refers to the surgical technique for the removal of preretinal tissue or the internal limiting membrane (ILM) in the macula for several retinal disorders, ranging from epiretinal membranes (primary or secondary to diabetic retinopathy, retinal detachment…) to full-thickness macular holes, macular edema, foveal retinoschisis, and others. The technique has evolved in the last two decades, and the different instrumentations and adjuncts have progressively advanced turning into a safer, easier, and more useful tool for the vitreoretinal surgeon. Here, we describe the main milestones of macular peeling, drawing attention to its associated complications.

ILM peeling technique influences the degree of a dissociated optic nerve fibre layer appearance after macular hole surgery

PURPOSE

We sought to assess the effect of two different internal limiting membrane [ILM] peeling techniques carried out during surgery for idiopathic macular holes on the postoperative extent of a dissociated optic nerve fibre layer appearance [DONFL].

METHODS

We collected prospective data of surgical records, videos, and pre- and postoperative imaging of a consecutive series of patients undergoing surgery for idiopathic macular hole with one of two surgeons. One surgeon used a forceps pinch-peel technique to peel the ILM, whereas the other surgeon used a diamond dusted membrane scraper. The extent of any DONFL was measured using spectral domain optical coherence tomography and blue reflectance imaging at three months postoperatively. A proportion of the ILMs removed were examined with transmission electron microscopy.

RESULTS

Fifty-seven patients were studied, with 41 in the forceps group and 16 in the scraper group. The groups were well matched, with no significant difference in any preoperative parameters. Some degree of DONFL was observed on the 3-month blue reflectance images in 88 % of the forceps group and 100 % of the scraper group [p = 0.14]. There was a significant difference in the total number of depressions in the nerve fibre layer typical of DONFL on OCT between the two groups [p = 0.001], and general regression analysis showed that the peeling technique used had the only significant association with the degree of DONFL observed. Electron microscopy showed large patches of cellular debris on the retinal side of the peeled ILM in 3 out of 4 cases in the scraper group and 1 out of 12 cases in the forceps group.

CONCLUSION

ILM peeling technique and possibly other surgeon-specific factors appear to influence the extent of DONFL observed after ILM peeling macular hole surgery.

A computer assisted method for nuclear cataract grading from slit-lamp images using ranking

In clinical diagnosis, a grade indicating the severity of nuclear cataract is often manually assigned by a trained ophthalmologist to a patient after comparing the lens' opacity severity in his/her slit-lamp images with a set of standard photos. This grading scheme is often subjective and time-consuming. In this paper, a novel computer-aided diagnosis method via ranking is proposed to facilitate nuclear cataract grading following conventional clinical decision-making process. The grade of nuclear cataract in a slit-lamp image is predicted using its neighboring labeled images in a ranked image list, which is achieved using a learned ranking function. This ranking function is learned via direct optimization on a newly proposed approximation to a ranking evaluation measure. Our proposed method has been evaluated by a large dataset composed of 1000 different cases, which are collected from an ongoing clinical population-based study. Both experimental results and comparison with several existing methods demonstrate the benefit of grading via ranking by our proposed method.

Imaging polarimetry in central serous chorioretinopathy

PURPOSE

To evaluate a noninvasive technique to detect the leakage point of central serous chorioretinopathy (CSR), using a polarimetry method.

DESIGN

Prospective cohort study.

METHODS

SETTING

Institutional practice.

PATIENTS

We examined 30 eyes of 30 patients with CSR.

MAIN OUTCOME MEASURES

Polarimetry images were recorded using the GDx-N (Laser Diagnostic Technologies). We computed four images that differed in their polarization content: a depolarized light image, an average reflectance image, a parallel polarized light image, and a birefringence image. Each polarimetry image was compared with abnormalities seen on fluorescein angiography.

RESULTS

In all eyes, leakage area could be clearly visualized as a bright area in the depolarized light images. Michelson contrasts for the leakage areas were 0.58 +/- 0.28 in the depolarized light images, 0.17 +/- 0.11 in the average reflectance images, 0.09 +/- 0.09 in the parallel polarized light images, and 0.11 +/- 0.21 in the birefringence images from the same raw data. Michelson contrasts in depolarized light images were significantly higher than for the other three images (P < .0001, for all tests, paired t test). The fluid accumulated in the retina was well-visualized in the average and parallel polarized light images.

CONCLUSIONS

Polarization-sensitive imaging could readily localize the leakage point and area of fluid in CSR. This may assist with the rapid, noninvasive assessment of CSR.