[Use of resources in cataract surgery-More waste is (not) always possible]

BACKGROUND

Aspects of ecological sustainability are becoming more important in the healthcare system. The use of resources is particularly high in the operating theater. Cataract surgery is one of the most frequent procedures in ophthalmology and even in medicine overall. Its CO₂ footprint is therefore quantitatively relevant. Approaches to conserve resources can be implemented at the levels of production and transport of materials and also in the form of reduction and management of waste.

MATERIAL AND METHODS

In this paper the sources of the waste load, the management of waste separation, the implementation of single-use instruments and the influence of innovative technologies during cataract surgery are presented based on the current literature.

RESULTS

Particularly the use of plastic materials for packaging and single-use instruments, also for reasons of hygiene, lead to an increased waste production. The simple separation of compound materials is difficult and only meaningful if the materials used in eye operations can be recycled; however, international comparisons show that cataract surgery can be performed with the same quality of results while conserving resources. Measures in organization and infrastructure are presented.

CONCLUSION

In the future, innovative strategies should be developed and the use of resources in Germany should also be critically questioned in order to reduce the CO₂ footprint of cataract surgery.

CG dinucleotides enhance promoter activity independent of DNA methylation

Most mammalian RNA polymerase II initiation events occur at CpG islands, which are rich in CpGs and devoid of DNA methylation. Despite their relevance for gene regulation, it is unknown to what extent the CpG dinucleotide itself actually contributes to promoter activity. To address this question, we determined the transcriptional activity of a large number of chromosomally integrated promoter constructs and monitored binding of transcription factors assumed to play a role in CpG island activity. This revealed that CpG density significantly improves motif-based prediction of transcription factor binding. Our experiments also show that high CpG density alone is insufficient for transcriptional activity, yet results in increased transcriptional output when combined with particular transcription factor motifs. However, this CpG contribution to promoter activity is independent of DNA methyltransferase activity. Together, this refines our understanding of mammalian promoter regulation as it shows that high CpG density within CpG islands directly contributes to an environment permissive for full transcriptional activity.

[Mechanical pupillary dilatation using rings in small pupils during cataract surgery : Video article]

OBJECTIVE

The purpose of mechanical pupillary dilatation in small pupils is a sufficient visualization of the lens to be able to perform capsulorhexis, phacoemulsification and intraocular lens implantation.

INDICATIONS

The indications for mechanical dilatation are fulfilled in patients where a sufficient pharmacological preoperative pupil dilatation is not possible.

SURGICAL TECHNIQUE

During routine cataract surgery specific foldable rings can be employed to dilate the pupil with the appropriate injector under viscoelastic substances. These rings are carefully placed at the pupillary margin until circular pupillary dilatation up to 6-7 mm is achieved. After intraocular lens implantation and before removing the viscoelastic substance the rings are slowly folded into the injector and then removed. The surgical technique is demonstrated in detail with the help of a video of the operation, which is available online.

RESULTS

Mechanical pupillary dilatation was possible in all patients studied (n = 14), which allowed uncomplicated phacoemulsification and intraocular lens implantation. For both ring systems studied the mean pupillary dilatation was 6.6 mm. At the end of surgery, the pupillary diameter was 4.89 mm using a Malyugin ring (MST, Redmond, Washington, USA) and 4.93 mm with an I‑ring (Visitec, Waltham, MA, USA; P > 0.05). Small lesions at the pupillary margin or pigment dispersion during implantation or explantation depended mostly on the individual patient situation and not on the ring used.

CONCLUSION

Mechanical pupillary dilatation with rings allows sufficient dilatation to perform cataract surgery. Both the Malyugin ring and the I‑ring achieved smooth and atraumatic pupillary dilatation.

[Influence of Macular Hole Width on Visual Acuity, Endotamponade and Closure Rate]

Background: The influence of the width of a full-thickness macular hole on preoperative visual acuity and its role for the intraoperative approach and closure rate were analysed in a prospective study. Methods: For 47 patients with a full thickness macular hole, a precise analysis of the central retina was performed with SD-OCT. An SF₆-gas-air mixture was used, with a lower concentration (15 %) for smaller holes ≤ 400 µm (group 1, n = 17) and a higher concentration (30 %) for larger holes > 400 µm (group 2, n = 30). Besides preoperative visual acuity, postoperative IOP fluctuations and closure rate were reviewed. Results: The mean hole width with SD-OCT was 419 ± 155 µm, with a significant negative correlation with preoperative visual acuity (r = - 0.56, p = 0.002). In the first group, mean early postoperative IOP was 23 mmHg and in the second group 33 mmHg (p < 0.001). Thus, for small macular holes, early postoperative IOP decompensation from gas expansion in the eye could be minimised. The closure rate was 90 %, with no significant difference between the two groups (p > 0.05). Conclusion: Determining the width of a macular hole with SD-OCT is an important indicator for the necessary endotamponade. Using a lower gas concentration (15 %) for smaller holes (≤ 400 µm) to prevent postoperative IOP fluctuations does not negatively influence closure rates.

[Relevant Parameters of Optic Nerve Analysis from Spectral Domain OCT for Glaucoma Diagnostics]

BACKGROUND

In early diagnosis and follow-up of patients with glaucoma anatomic-diagnostic examinations have become more important in addition to static perimetry. Patients with open angle glaucoma suffer a slow visual field loss due to the loss of ganglion cells, which these examinations could detect earlier than perimetry can.

METHODS

Parameters of the optical coherence tomography (OCT) were analysed in 89 patients (175 eyes) with advanced open angle glaucoma. In a prospective study, the functional findings from static perimetry (HFA-II, 24-2-programme) and the anatomic parameters of optic nerve analysis with SD-OCT (Cirrus-OCT) were evaluated.

RESULTS

The results showed a mean deviation (MD) in perimetry of - 8.31 ± 9.76 dB and in the analysis of the optic nerve head of 71.93 ± 15.86 µm retinal nerve fibre layer (RNFL) as well as 85.54 ± 28.2 µm RNFL for the inferior quadrant, 0.95 ± 0.46 mm(2) for the rim area and 0.69 ± 0.18 for the vertical CD ratio. There was a significant correlation (p < 0.05) between MD und RNFL (r = 0.603), as well as RNFL of the inferior quadrant (r = 0.620), rim area (r = 0.552) and average CD ratio (r = - 0.551). The best correlation for the optical nerve head analysis was found between MD and vertical CD ratio (r = - 0.568).

CONCLUSIONS

There was a good correlation between functional and anatomic parameters in perimetry and OCT. In particular, the mean and inferior retinal nerve fibre layer thickness, the rim area, and the vertical CD ratio revealed to be significant parameters in glaucomatous eyes.

Genomic profiling of DNA methyltransferases reveals a role for DNMT3B in genic methylation

DNA methylation is an epigenetic modification associated with transcriptional repression of promoters and is essential for mammalian development. Establishment of DNA methylation is mediated by the de novo DNA methyltransferases DNMT3A and DNMT3B, whereas DNMT1 ensures maintenance of methylation through replication. Absence of these enzymes is lethal, and somatic mutations in these genes have been associated with several human diseases. How genomic DNA methylation patterns are regulated remains poorly understood, as the mechanisms that guide recruitment and activity of DNMTs in vivo are largely unknown. To gain insights into this matter we determined genomic binding and site-specific activity of the mammalian de novo DNA methyltransferases DNMT3A and DNMT3B. We show that both enzymes localize to methylated, CpG-dense regions in mouse stem cells, yet are excluded from active promoters and enhancers. By specifically measuring sites of de novo methylation, we observe that enzymatic activity reflects binding. De novo methylation increases with CpG density, yet is excluded from nucleosomes. Notably, we observed selective binding of DNMT3B to the bodies of transcribed genes, which leads to their preferential methylation. This targeting to transcribed sequences requires SETD2-mediated methylation of lysine 36 on histone H3 and a functional PWWP domain of DNMT3B. Together these findings reveal how sequence and chromatin cues guide de novo methyltransferase activity to ensure methylome integrity.

[Effect of ocular compression on anterior chamber dimensions in cataract surgery using topical anaesthesia]

PURPOSE

Ocular compression is part of the preparation before cataract surgery to reduce the incidence of a positive intraoperative pressure. The purpose of this clinical study was to assess the influence of ocular compression on the anterior chamber dimensions and biometric parameters before cataract surgery using topical anaesthesia.

METHODS

In a prospective, comparative observational study the biometric parameters were assessed with slitlamp-adapted anterior segment OCT (SL-OCT, Heidelberg Engineering) and ultrasound biometry (A-Scan+, Sonomed) in 51 consecutive patients (51 eyes) with a mean axial eye length of 22.90 ± 1.05 mm before cataract surgery. The measurements were performed in all patients before and immediately after ocular compression (Oculopressor G-15392, Geuder). In 32 patients the measurements were repeated 10 minutes after ocular compression.

RESULTS

The optical and acoustic values of the anterior chamber depth did not change significantly after ocular compression (p > 0.05). Digital gonioscopy with OCT revealed a mean increase of the anterior chamber angle of 2.37° (p < 0.001) from 45.75 ± 7.28° to 48.12 ± 7.28°, and the angle opening distance of 37 µm (p = 0.017) from 627 ± 184 µm to 664 ± 162 µm. Also the average acoustic axial vitreous distance decreased significantly from 15.22 ± 0.98 to 15.18 ± 0.96 mm (p = 0.034) with a posterior shift in the relative lens position (p = 0.018).

CONCLUSIONS

In this clinical study, only slight anterior chamber and biometric changes were observed after ocular compression before cataract surgery using topical anaesthesia. There was a significant increase of the anterior chamber angle and angle opening distance with a concomitant decrease of the vitreous distance and shifting of the iris lens diaphragm.

[Surgical treatment of chronic macular oedema with a combination therapy]

BACKGROUND

The treatment of therapy-resistent chronic macular oedema remains a challenge. Therefore a combination therapy, consisting of medical, biological and mechanical components was assessed.

METHODS

A surgical treatment was performed in 35 eyes (34 patients) with chronic and therapy-resistant macular oedema, resulting from diabetic maculopathy (n = 25), vitreoretinal traction (n = 7) or following a retinal venous occlusion (n = 3). An intravitreal injection of bevacizumab was given on the day before surgery, consisting of pars plana vitrectomy with ILM peeling with Brilliant Blue G (BBG), as well as an air tamponade combined with postoperative prone positioning. The visual function and the central retinal thickness were measured in follow-up.

RESULTS

Functionally, the visual acuity could be stabilised to an average of 0.18 and macular oedema was reduced in most patients. Anatomically, a significant reduction in central macular thickness by 193 µm (29 %), from 598 µm to 405 µm (p < 0.001), and a regression in the intraretinal cystoid changes were observed. No significant complications occurred, whereas in 6 patients additional consecutive treatment was necessary.

CONCLUSION

A stabilisation of the visual acuity and an improvement in the structural retinal situation could be achieved by an elaborate combination therapy, based on a pharmacological, a biological and a mechanical approach. Long-term follow-up and consecutive supplementary treatments are necessary to ensure the functional stability.

DNA-binding factors shape the mouse methylome at distal regulatory regions

Methylation of cytosines is an essential epigenetic modification in mammalian genomes, yet the rules that govern methylation patterns remain largely elusive. To gain insights into this process, we generated base-pair-resolution mouse methylomes in stem cells and neuronal progenitors. Advanced quantitative analysis identified low-methylated regions (LMRs) with an average methylation of 30%. These represent CpG-poor distal regulatory regions as evidenced by location, DNase I hypersensitivity, presence of enhancer chromatin marks and enhancer activity in reporter assays. LMRs are occupied by DNA-binding factors and their binding is necessary and sufficient to create LMRs. A comparison of neuronal and stem-cell methylomes confirms this dependency, as cell-type-specific LMRs are occupied by cell-type-specific transcription factors. This study provides methylome references for the mouse and shows that DNA-binding factors locally influence DNA methylation, enabling the identification of active regulatory regions.

[Clinical experience with brilliant blue G staining of the retinal surface]

BACKGROUND

Staining of the retinal surface has improved the intraoperative removal of semitransparent membranes during macular surgery. The purpose of this study was to evaluate the clinical experiences with brilliant blue G (BBG) staining of the retinal surface.

METHODS

BBG (Brilliant peel, Fluoron) was applied during vitrectomy and macular surgery in 43 patients. In 47 % there was a macular hole (MH), whereas 53 % had epiretinal membranes (ERM). Intraoperatively BBG was applied on the retinal surface under infusion or air conditions for 30 - 60 s. In MH the internal limiting membrane (ILM) and in ERM the membrane was removed. Postoperatively all patients were examined on average after 9 weeks.

RESULTS

Although intraoperative BBG staining was less intensive compared to ICG staining, the staining was sufficient to safely remove the semitransparent membranes in all cases. In all patients with MH hole closure was achieved, and in 96 % with ERM the metamorphopsiae decreased. The mean decimal visual acuity increased from 0.25 ± 0.13 to 0.37 ± 0.20 (p < 0.05) and improved in 63 % of the patients. Clinically, there were no toxic side-effects from BBG staining.

CONCLUSIONS

BBG allowed a complete and selective staining of the retinal surface. Thus, ILM and ERM could be removed safely during macular surgery. No clinical retinal toxicity was observed.