SODIUM HYALURONATE 2.3% PREVENTS CONTACT BETWEEN INDOCYANINE GREEN AND RETINAL PIGMENT EPITHELIUM DURING VITRECTOMY FOR HIGHLY MYOPIC MACULAR HOLE RETINAL DETACHMENT

Injectable in situ cross-linking hyaluronan hydrogel for easier removal of posterior vitreous cortex in vitrectomy

PURPOSE

Removing transparent vitreous tissues, such as a residual vitreous cortex (VC) or proliferative membrane, without damaging the retina is often problematic in vitrectomy. We examined the feasibility of an injectable in situ cross-linking hyaluronan hydrogel (XL-HA) for vitrectomy.

STUDY DESIGN

Experiments using ex vivo and in vivo animal models.

METHODS

HA-dibenzocyclooctyne and HA-azidoethylamine solutions were mixed to form XL-HA, which then gradually formed a hydrogel. We tested the function of XL-HA in ex vivo porcine eyes. We then examined the performance of XL-HA in in vivo rabbit models of posterior vitreous detachment, posterior VC removal, and proliferative vitreoretinopathy.

RESULTS

The ex vivo study showed that XL-HA rapidly embedded triamcinolone acetonide, mimicking VC attached to the retina, and became hard enough to be pinched with tweezers within 3 minutes, allowing us to remove only the triamcinolone acetonide without impairing the internal limiting membrane. In the in vivo rabbit models, XL-HA injection improved posterior vitreous detachment, and the thin and fragile posterior VC or fibrous proliferative membrane was readily peeled off without any damage to the underlying retina as compared with untreated controls. A short-term intraocular biocompatibility test demonstrated that the intraocular pressure remained normal with XL-HA injected into the eye. In addition, transmission electron microscopy showed no obvious abnormalities in the cornea or in the inner and outer retina.

CONCLUSION

The results indicate that XL-HA is a potential adjunctive device to help make vitrectomy safe, effective, and successful.

Development of in situ crosslinked hyaluronan as an adjunct to vitrectomy surgery

Ophthalmologists have used hyaluronan (HA) products as adjuncts to ocular surgery since the 1970s. However, HA products are not always functional in surgeries of the posterior eye segment due to their lack of biomechanical strength. In this study, we developed an in situ crosslinked HA (XL-HA) and evaluated its potential as an adjunct to vitrectomy surgery in an in vitro model with a triamcinolone acetonide (TA) layer used as a pseudo residual vitreous cortex (RVC). Within a few minutes at concentrations over 0.9%, XL-HA, generated by the click chemistry of HA-dibenzocyclooctyne and HA-azidoethylamine, formed a hydrogel with the appropriate hardness for tweezers peeling. XL-HA (concentration, 0.76-1.73%) without dispersion successfully entered the TA layer and removed more than 45% of the total TA. Dynamic viscoelasticity helps to explain the rheological behavior of hydrogels, and the assessment results for XL-HA indicated that suitable concentrations were between 0.97% and 1.30%. For example, 1.30% XL-HA hydrogel reached sufficient hardness at 3 min for tweezers peeling, and the TA removal ability exceeded 70%. These results demonstrated that XL-HA was a potential adjunct to successful vitrectomy.

Evaluation of the hearing preservation and tissue response of dexamethasone and hyaluronic acid delivery during cochlear implantation on cats in a three-month period study

OBJECTIVE

To evaluate the effects of DX and HA on hearing preservation and tissue response with cochlear implantation in a cat mode.

METHODS

11 cats were bilaterally implanted with Nurotron electrode. According to the different treatment, 22 ears were subdivided into four following groups: Electrode (E) only, Electrode +HA (E+H), Electrode + DX (E+DX), and Electrode +HA +DX (E+H+DX). Auditory brainstem responses (ABR) thresholds were recorded before and 3 months after surgery. After 3 months of cochlear implantation histopathological assessment of all cochleae were performed .

RESULTS

At low frequencies, the mean ABR thresholds shift in animals treated with E+H+DX demonstrated a statistically significant difference. The proportion of cochleae showing fibrous tissue and new bone formation was 50% in E+H+DX group, 66.7% in E+DX group, 83.3% in E+H group and 100% in E group.

CONCLUSION

United HA and DX local delivery could provide better protection against hearing loss at low-frequency threshold and could more effectively reduce the trauma related to electrode insertion and the fibrous tissue formation around the electrode.

Viscoelastic-assisted inverted cover and free ILM flap techniques

statement: Surgical technique: an innovative way of using cohesive viscoelastic to stabilize the ILM flap during the cover inverted-flap and free-flap procedures.Summary statement: Surgical technique: an innovative way of using cohesive viscoelastic to stabilize the ILM flap during the covering step in the inverted-flap and free-flap procedures.

Role of Vital Dyes in Chromovitrectomy

ABSTRACT

Chromovitrectomy, the intraocular application of dyes to assist visualization of preretinal tissues during vitreoretinal surgery, was introduced to avoid ocular complications related to internal limiting membrane peeling, inadequate removal of the vitreous, and incomplete removal of epiretinal membranes. Since 2000, chromovitrectomy has become a popular approach among vitreoretinal specialists. The first vital dye used in chromovitrectomy, indocyanine green, facilitated identification of the fine and transparent internal limiting membrane. Following indocyanine green, trypan blue was introduced to identify epiretinal membranes, and triamcinolone acetonide stained the vitreous well. Recently, additional natural dyes such as lutein and anthocyanin from the açaí fruit have been proposed for intraocular application during vitrectomy. The main goal of this review was to study the role of vital stains in chromovitrectomy and report the latest findings in the literature.

Macular Hole in Myopic Eyes: A Narrative Review of the Current Surgical Techniques

Macular hole (MH) in myopic eyes is a disease arising from complex tractional forces exerted by vitreomacular interface, epiretinal tissue, and progressive scleral ectasia of the posterior ocular globe wall. This retinal disease requires vitreoretinal treatment for its repair, and the surgical intervention remains a challenge also for experienced surgeons. The aim of this review is to describe the current knowledge regarding the pathogenesis of MH in myopic eyes and to detail novel surgical techniques and technological advancements in its surgical management.

Vitrectomy in high myopia: a narrative review

Pathologic myopia is associated with degenerative changes of the globe, especially at the posterior pole. Eyes affected by pathologic myopia have higher odds to undergo posterior segment surgery and, in those eyes, vitreoretinal surgery is challenging. Many practical tips and tricks can make the surgical procedures simpler, significantly preventing sight-threatening intra- and post-operative complications. Moreover, novel surgical techniques and technological advancements (i.e. ad-hoc instrumentation, minimally invasive vitreoretinal surgery, filters, dye staining, intraoperative optical coherence tomography and 3-dimensional surgery) may play role in highly myopic eyes. The aim of the present work is to review practical tips and tricks, novel surgical techniques and technological advancements.

COMPARATIVE EVALUATION OF SEQUENTIAL INTRAOPERATIVE USE OF WHOLE BLOOD FOLLOWED BY BRILLIANT BLUE VERSUS CONVENTIONAL BRILLIANT BLUE STAINING OF INTERNAL LIMITING MEMBRANE IN MACULAR HOLE SURGERY

PURPOSE

To compare the structural and functional outcome of use of autologous heparinized whole blood before staining internal limiting membrane with brilliant blue (BB) versus conventional BB-assisted macular hole surgery.

METHODS

Sixty eyes of 60 patients were randomly divided equally in Group A (BB staining using whole blood) and Group B (conventional BB staining). Clinical assessment and spectral domain optical coherence tomography was done at baseline and 3 weeks, 6 weeks, 16 weeks, and 6 months postoperatively.

RESULTS

Group A eyes had a significantly higher best-corrected visual acuity as compared with Group B postoperatively (P < 0.001, <0.001, 0.004, 0.04 at 3, 6, 16 weeks, and 6 months). Inner segment/outer segment junction continuity was noted in greater number of eyes in Group A compared with Group B (P = 0.02, 0.002, 0.003, and 0.03 at 3, 6, 16 weeks, and 6 months). Eyes in Group A had significantly higher outer foveal thickness at 3 weeks (P = 0.001) and 6 weeks (P < 0.001) compared with Group B.

CONCLUSION

Use of whole blood before staining internal limiting membrane with BB causes earlier and better visual rehabilitation postoperatively, which could be attributed to earlier photoreceptor regeneration as evidenced by inner segment/outer segment junction continuity and increase in outer foveal thickness.

In vitro experiment to elucidate the mechanism of the 'soft shell technique' for preventing subretinal migration of perfluoro-octane

AIM

Perfluorocarbon liquid (PFCL) can migrate into subretinal space in detached and stiffened retina with open holes during vitreoretinal surgery. An innovative 'soft shell' technique was introduced to reduce the complication using hyaluronate (HA) to 'cover' the retinal hole. This study aims to study the effectiveness of this technique in vitro.

METHODS

Ex vivo porcine retina was mounted on a transwell insert. Beneath the retina was an aqueous solution. Two retinal holes were made using needle punctures. One of the two retinal holes was covered with HA. Perfluoro-n-octane (PFO) was added above the retina incrementally using a syringe pump. The height of PFO required to cause the migration of PFO through the retinal holes was measured. The 'pendant drop' method was carried out to measure the interfacial tensions between the PFO and aqueous, and between PFO and four different concentrations of HA solution.

RESULTS

A statistically higher PFO level was required to cause the migration of PFO through the retinal hole with HA coating than without HA coating (Tobit regression with p<0.05). The use of HA was associated with 2.39-fold increase in hydrostatic pressure before the collapse of the PFO interface at the retinal holes. The interfacial tension between PFO and HA solution with concentrations of 0.05%, 0.25%, 0.5% and 1% were 54.2±0.6, 55.3±0.6, 59.5±1.5 and 68.3±1.3 mN/m, respectively (mean±SD). The interfacial tension between PFO and aqueous with 1% HA coating (68.3±1.3 mN/m) was significantly higher than that without (37.4±3.4 mN/m) (p<0.05).

CONCLUSIONS

The interfacial tension between HA and PFO is higher than that between aqueous and PFO. This is a plausible physical explanation of how the 'soft shell' technique might work to prevent subretinal migration of PFCL.

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.

Use of viscoelastic substance in ophthalmic surgery - focus on sodium hyaluronate

Among viscoelastic substances, sodium hyaluronate has become the most popular for intraocular surgeries since the introduction of Healon^® (sodium hyaluronate 1%, 4 × 10⁶ daltons) in 1979. This review focuses on the recent development of a new generation of sodium hyaluronate agents with new rheologic properties and the relevant new techniques used in cataract, glaucoma, corneal, and vitreoretinal surgeries. The introduction of sodium hyaluronate agents with different rheologic properties has improved the safety and reliability of intraocular surgeries. Although there have been numerous studies reporting the effectiveness of viscoelastic substances in intraocular surgeries, rigorous validation by multi-center randomized control trials is lacking in many cases. At present, no single viscoelastic agent is most suitable to all of the various intraocular surgical techniques. Therefore, ophthalmologic surgeons should keep up with recent developments of viscoelastic agents and relevant surgical techniques for better patient care.

Viscoelastic agent retention and failed macular hole surgery

PURPOSE

To describe the retention of a viscoelastic agent as a possible cause of failed macular hole surgery.

METHODS AND PATIENTS

Three consecutive patients underwent macular hole surgery. A bubble of viscoelastic agent was used to prevent contact between indocyanine green dye and retinal pigment epithelium cells.

RESULTS

Macular hole repair failed in all three cases. After a second surgery the holes closed successfully.

CONCLUSION

The use of a dispersive viscoelastic agent to avoid indocyanine green toxicity in macular hole surgery may prevent the closure of the hole.

Effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation

The present study examined the effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation in animal models. Guinea pigs were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone, sodium hyaluronate or saline. Cats were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone or a mixture of triamcinolone with sodium hyaluronate. In guinea pigs, impedance changes and intracochlear tissue response were less for the hyaluronate and saline groups. In cats, impedance in the dexamethasone group increased similar to non-treated cats. Impedance of triamcinolone treated cats remained low for about two months after implantation, before increasing to levels similar to the other groups. Significant fibrous tissue growth was observed histologically. The results of the present study indicate that a single intracochlear application of hyaluronate or triamcinolone may postpone, but will ultimately not prevent the rise in impedance following cochlear implantation.

INDOCYANINE GREEN???ASSISTED INTERNAL LIMITING MEMBRANE PEELING FOR MACULAR HOLES

BACKGROUND

Indocyanine green (ICG) staining facilitates definitive internal limiting membrane (ILM) peeling during macular hole surgery (MHS), but might cause toxicity.

PURPOSE

To determine if ICG to assist in ILM peeling has an effect on anatomic or visual results in MHS with ILM peeling.

METHODS

Retrospective, comparative review including primary analysis of 173 cases undergoing MHS. Visual acuity >or=20/50, <or=20/200, three-line visual acuity improvement, and anatomic success rates were analyzed as endpoints.

RESULTS

The single operation hole closure rate was 87% with ICG versus 83% without ICG (P = 0.52). Postoperative median best-corrected visual acuity was 20/70 and 20/80 in the ICG and no ICG groups with median follow-up intervals of 8 and 9 months. The use of ICG was associated with a higher rate of <or=20/200, but ILM peeling and ICG use was not associated with better anatomic success, visual improvement, or >or=20/50 visual acuity.

CONCLUSIONS

ICG usage during macular hole surgery was not associated with worse visual outcomes, suggesting possible toxic effects reported are not clinically significant. If the ILM cannot be peeled effectively, ICG should be considered a safe option.

A Surgical Technique to Protect the Macular Hole in Indocyanine Green-Assisted Vitrectomy

A 38-year-old man with human immunodeficiency virus was referred for evaluation of retinal lesions in both eyes. Optical coherence tomography was performed after dilating the pupils. Biomicroscopy of the retina showed an atypical, solitary, yellowish-white lesion in the macula of both eyes with no inflammation of the vitreous. Optical coherence tomography of the lesions showed an area of extremely low reflectivity with well-defined but irregular borders in the outer retina. The surrounding retina showed normal reflectivity and was of normal thickness. Optical coherence tomography showed selective necrosis of the outer layers due to progressive outer retinal necrosis. Optical coherence tomography may serve as a useful tool for the early diagnosis of progressive outer retinal necrosis.

Intravitreal Staining of the Internal Limiting Membrane Using Indocyanine Green in the Treatment of Macular Holes

Surgical management of macular holes consists of pars plana vitrectomy, removal of the posterior hyaloid facia, and peeling of the epiretinal membranes (ERM). Additionally, removal of the internal limiting membrane (ILM) may enable an increase in the anatomic and functional success rates. However, recognition of fine ILM is difficult thus increasing the time that the macula is exposed to intraoperative light. Staining the ILM with indocyanine green (ICG) dye during vitrectomy facilitates recognition of the ILM and assures that all adjacent ERM are removed. Therefore, ICG-assisted ILM peeling has gained worldwide popularity among vitreoretinal surgeons. However, there are some concerns about the intravitreal ICG application. Reports in the literature described a variety of application techniques using different concentrations. The postoperative outcomes were controversial reporting heterogeneous anatomical and functional outcomes after ICG application, as well as descriptions of adverse effects related to the dye. We discuss the indications, techniques, surgical results, and complications after intravitreal ICG injection for the treatment of macular holes.

Prevention of Indocyanine Green Toxicity on Retinal Pigment Epithelium with Whole Blood in Stain-Assisted Macular Hole Surgery

PURPOSE

To examine whether whole blood prevents indocyanine green (ICG) toxicity on in vitro retinal pigment epithelium (RPE) and prevents RPE staining in ICG-assisted macular hole (MH) surgery.

DESIGN

In vitro study and prospective case series.

PARTICIPANTS

In vitro study and 20 patients who underwent ICG-assisted MH surgery (20 eyes).

METHODS

In the in vitro study, cultured human RPE cells were covered with balanced saline solution (BSS), heparinized whole blood, plasma, or packed red blood cells, then exposed to various concentrations of ICG. One cohort was incubated in the dark; the other cohort was exposed to light. Indocyanine green toxicity was evaluated by mitochondrial dehydrogenase assay. In the clinical study, a prospective noncomparative review of 20 consecutive patients (20 eyes) with stage 3 to stage 4 MH who underwent surgery with ICG to stain the internal limiting membrane (ILM) was performed. Indocyanine green solution (0.5 mg/ml) was used to stain the ILM after autologous whole blood covered the macular hole area. Postoperative staining of ICG on RPE was detected by an infrared-sensitive camera.

MAIN OUTCOME MEASURES

Cultured human RPE cell viability, macular hole closure rate, median visual acuity preoperatively and postoperatively, postoperative ICG staining, and retinal changes.

RESULTS

Cultured human RPE cells covered by whole blood or plasma showed no decrease of mitochondrial dehydrogenase even in 5.0 mg/ml concentration of ICG for 20 minutes with or without light exposure. Conversely, those exposed to ICG and covered with BSS demonstrated a significant decrease of mitochondrial dehydrogenase after incubation in 5, 2.5, and 1.0 mg/ml for 20 minutes in the dark and in 5 to 0.05 mg/ml with light. Clinically, no postoperative staining on RPE was detected. No atrophic RPE changes or other retinal changes were observed in the previous MH area that was covered by autologous whole blood in all 20 eyes on average follow-up of 10.6 months. The hole closed in 19 eyes (95%) on first surgery. Visual acuity improved in 17 eyes (85%) on most recent follow-up.

CONCLUSIONS

Whole blood prevents ICG toxicity in RPE cell culture and prevents staining of RPE in surgery of MH when the ILM is stained with ICG.