Theodor Stappler

Tamponade properties of double-filling with perfluorohexyloctane and silicone oil in a model eye chamber

BackgroundThe use of perfluorohexyloctane as a heavier-than-water tamponade for long-term use is limited by its tendency to dispersion and associated intraocular inflammation. Double-filling with silicone oil and F6H8 produces a united, two-layer bubble, appearing as a single bubble. This has been proposed as a method of improving the utility of F6H8 as a tamponade.MethodsA surface modified polymethylmethacrylate model eye chamber was double-filled with perfluorohexyloctane and silicone oil to approximate a 90% fill. The proportion of silicone oil was increased in a stepwise fashion. A qualitative comparison of surface contact at each stage was made. Chambers with one, two or no indent were used. Dispersion by agitation of the chamber was assessed.ResultsWith less than 20% silicone oil it was difficult to force the two liquids to make contact. With more oil they united in the form of a single bubble joined at an interface. Once joined, the sides of the single bubble were drawn away from the wall of the chamber. As the proportion of silicone oil increased the area of lost contact increased and progressed inferiorly. Compared to F6H8 alone the double-fill reduced dispersion.ConclusionSilicone oil and F6H8 can unite to form a single bubble that changes the effectiveness of either tamponade agent on their own. The double-fill needs to have enough silicone oil to form a single bubble, but this needs to be kept as low as possible to avoid progressive loss of lateral tamponade. It does not provide good simultaneous superior and inferior tamponade. The double-fill reduces dispersion.

Endophthalmitis following intravitreal injections.

BackgroundTo report the clinical features, culture results, management and visual outcome of patients with endophthalmitis following intravitreal injections.MethodsRetrospective review of all patients with suspected endophthalmitis after intravitreal injections treated with intravitreal antibiotics (teicoplanin and ciprofloxacin) at a referral centre between January 2003 and December 2010.ResultsNineteen cases that had aqueous or vitreous biopsy were identified. Nine had negative culture. Ten had positive culture; Staphylococcus species in 4/10, Streptococcus species in 4/10, E. coli in 1/10 and gram-negative bacilli in 1/10. Symptoms developed within the first 48 hours in all. One of ten culture-positive cases had no pain on presentation, while 5/9 patients with negative culture reported pain. Initial treatment consisted of intravitreal antibiotics in all cases, 6/19 cases required a second intravitreal antibiotic injection, 4/19 underwent vitrectomy as secondary therapy. At the last follow up, 7/19 patients had visual acuity of 6/18 or better, 9/19 had visual acuity of 6/60 or worse.ConclusionThe overall numbers of patients with endophthalmitis following intravitreal injections has risen dramatically over the past years. In contrast to earlier reports of multicentre studies, outcome of patients is relatively poor in the current treatment settings. We did not find clinical features useful in identifying cases with negative culture.

A guide to the removal of heavy silicone oil

Aim: Heavy silicone oil removal can be challenging and differs considerably from conventional oil. Traditionally, strong active aspiration had to be applied through a long 18G needle just above the optic disc. We present a novel technique using a much shorter (7.5 mm) and smaller (20G) needle allowing its removal “from a distance.” Method: Active aspiration on a vacuum of 600 mm Hg of the “viscous fluid injector” was applied using the 20G cannula in a polymethylmethacrylate model eye chamber that was surface-modified to mimic the surface properties of the retina. Measurements were taken using still photographs. Results: Under injection the maximum diameter of a silicone oil bubble supported by interfacial tension alone was 5 mm for a steel and 7 mm for a polyurethane cannula. Under suction, the silicone bubble changed shape and became conical, thus further increasing the cannula’s reach. This conical shape illustrated “tubeless siphoning,” which is a physical property of non-Newtonian fluids. Discussion: The use of shorter and smaller gauge cannula for removal of Densiron obviates the need to enlarge the sclerotomy beyond 20G or to apply suction in close proximity to disc and fovea. This potentially reduces the risk of iatrogenic damage such as entry site tears or postoperative hypotony.

Injectability of silicone oil-based tamponade agents

Background/aims High viscosity silicone oils are used as tamponade agents to increase the resistance to emulsification; however, this makes the oils more difficult to inject. Increasing the extensional viscosity is one way to reduce emulsification. This study aimed to evaluate how silicone oils with increased extensional viscosity behave in terms of their ease of injection. Methods The shear viscosity and the length of time taken to inject 9 ml of Siluron 1000, Siluron 2000, Siluron 5000, SiliconMate, a 56/44 w/w blend of Siluron 1000/Siluron 5000 (Blend A) and a 90/10 w/w blend of Siluron 1000/PDMS 423kDa molecular weight (Blend B) were examined. Results The shear viscosity of Siluron 1000, Siluron 2000 and Siluron 5000 were within the expected ranges. The shear viscosity of Blend A was 2283 mPa s, Blend B was 4710 mPa s and SiliconMate was 995.3 mPa s. Siluron 1000 and SiliconMate had the shortest injection times as expected due to their lower shear viscosities. Comparison of Siluron 2000 and Blend A demonstrated that Siluron 2000 was easier to inject. Similarly, Blend B was easier to inject than Siluron 5000. Conclusion Silicone oil blends containing small percentages of a high molecular weight additive are easier to inject than single grade oils of the equivalent shear viscosity.

The effect of scleral exoplant removal on strabismus following retinal detachment repair.

PURPOSE Scleral buckling for retinal detachment is a well-reported cause of secondary strabismus. We analyzed the effects on motility of removal of the exoplant alone to determine whether this is warranted as a separate step in the surgical management of these patients. METHODS A retrospective case series of patients who underwent scleral exoplant removal due to symptomatic strabismus development following retinal detachment repair from 2007 to 2009 was conducted. Manifest horizontal and vertical deviations were treated as vectors of a single combined deviation (|dev|). Pre- and postoperative manifest |dev| in the primary position (|dev|(pp)) and in the gaze position of maximal deviation (|dev|(max)) were analyzed. RESULTS Five patients were identified, all with symptomatic, binocular diplopia in the primary position prior to exoplant removal. Median |dev|(pp) prior to exoplant removal was 21(Δ) and following removal was 21(Δ) (P = 0.81). The median |dev|(max) prior to exoplant removal was 33(Δ) and following removal, 22(Δ) (P = 0.82). Median follow-up was 8 months. There were no cases of retinal redetachment following the exoplant removal. No patient reported any subjective improvement of their diplopia. All 5 patients went on to have strabismus surgery as a separate procedure. CONCLUSIONS Median primary position deviation was unchanged by scleral buckle removal, and Exoplant removal has minimal long-term benefit on the strabismus following scleral buckling procedures.

Fibrous membranes in diabetic retinopathy and bevacizumab.

Purpose: The purpose of this study was to determine the histopathologic characteristics of bevacizumab-treated human proliferative diabetic retinopathy (PDR) membranes with particular regard to membrane vasculature as a step toward addressing the effects of the drug on PDR membranes. Intravitreous injection of bevacizumab, an antivascular endothelial growth factor monoclonal antibody, has recently been advocated as an adjunct in surgery for PDR. In this context, a clinically observed decrease in PDR epiretinal membrane vascularity (vascular regression) occurs from 24 hours to 48 hours after injection, but the exact mechanisms of drug action are unknown. Methods: A consecutive series of seven PDR membrane specimens that had been removed sequentially from seven bevacizumab-treated patients were studied retrospectively. The membrane specimens were examined using light microscopic methods, including immunohistochemistry. Results: Five of the seven membranes were clinically avascular (one contained “ghost” vessels) and did not hemorrhage during excision. Of these 5 specimens, which included 1 removed 7 days after a total of 6 intravitreous injections of 1.25 mg bevacizumab, 4 contained histologically detectable capillaries (1 did not). These blood vessels were lined by endothelial cells as determined by immunohistochemistry for the endothelial markers CD31 and CD34. The two remaining membranes were clinically and histologically still vascularized despite bevacizumab treatment. All the specimens also contained smooth muscle actin-containing fibroblastic cells within the collagenous stroma. Conclusion: The findings do not support the concept that the clinical phenomenon of vascular regression in PDR membranes after bevacizumab injection in the vitreous is resulting from obliteration of the membrane blood vessels. Another mechanism appears to be involved in at least some patients, possibly a vasoconstrictive response. Such a mechanism might explain reversal of the effects of bevacizumab that has been reported after this treatment.

Novel Heavy Tamponade for Vitreoretinal Surgery

PURPOSE The aim of this study was to produce a heavy tamponade with a specific gravity greater than 1.06 g/mL that was optically transparent, could be manufactured using simple processing, could be injected using standard clinical equipment, and would have appropriate biocompatibility. METHODS Aerosil silica was added to a phenyl trimethicone and mixed via a roller, overhead stirring, and ultrasonics. The refractive index, visible absorbance, and shear viscosity were measured. The injectability of the solutions was evaluated using the Accurus Viscous Fluid Injection system. The tamponade efficiency was assessed using a model eye chamber and compared with that of Densiron 68, Oxane HD, and F6H8. The biocompatibility was evaluated in vitro and in vivo in rabbits. RESULTS Tamponade agents were produced with specific gravities of 1.10, 1.11, 1.13, and 1.16 g/mL that had good optical clarity. Mixing using overhead stirring was sufficient to produce tamponade agents with shear viscosities in the range 1000 to 5000 mPa·s that were reproducible and stable during storage. The solutions were easier to inject using the Accurus Viscous Fluid Injection system than silicone oil 1000 mPa·s. The 11% silica solution had greater tamponade efficiency than Densiron 68 or Oxane HD. There was no evidence of cytotoxicity in vitro. Silica solution 11% induced cataract earlier than Polydimethylsiloxane 1000 (PDMS 1000). Silica solution 11% and phenyl trimethicone reduced the a-wave value at 1 week after vitrectomy, but recovery was observed at later time points. Silica solution 11% caused inner nuclear layer (INL) nuclei dropdown in inferior retina from 4 weeks postoperation. Polydimethylsiloxane 1000 induced a similar phenomenon in superior retina 12 weeks postoperation. CONCLUSIONS We have produced a heavy tamponade with good clarity that has appropriate shear viscosity, injectibility, enhanced tamponade efficiency, and biocompatibility similar to that of PDMS 1000.

Outcomes of delayed vitrectomy in open-globe injuries in young patients.

Purpose: The timing of vitrectomy for severe penetrating eye injury to the posterior segment remains controversial; this is particularly pertinent if patients are children and young adults. We present our results of the surgical procedure in young patients after penetrating eye injury using a delayed approach. Methods: Noncomparative interventional study of patients up to 29 years of age who had vitreoretinal surgery for penetrating eye injury. Surgical procedure was performed in seven eyes of six patients. Posterior vitrectomy was performed because of hemophthalmos after waiting for a mean of 49 days (range, 17-90 days) after posterior vitreous detachment was confirmed on ultrasound examination. Results: The mean postoperative follow-up period was 22 months (range, 9-35 months). Of the 7 patients, 6 (85.7%) achieved visual acuity (Snellen acuity) of 6/12 or better and 4 eyes (57.1%) reached 6/6. At the last follow-up, all patients were pseudophakic, 2 required secondary lens implants, and retinal detachment developed in 1 patient. Conclusion: This consecutive case series underlines the fact that a delayed approach is compatible with good visual prognosis in relatively young patients.

Is There a Role for Long-Term Silicone Oil Tamponade for More than Twelve Months in Vitreoretinal Surgery?

Despite modern and sophisticated vitreoretinal techniques, the authors are convinced that an underreported patient group exists, for whom long-term silicone oil tamponade is unavoidable. We conducted a literature review of the current evidence base in order to provide guidance on the ocular tolerance and side effects of long-term silicone oil, weighing up benefits against complications as well as providing an outlook on future silicone oils with improved physical properties. We advocate the removal of silicone oil in all cases; however, one has to recognise that long-term silicone oil tamponade may have to be considered as a measure of last resort for selected patients. There is a clinical need to develop novel, emulsification-resistant tamponades.

F4H5: a novel substance for the removal of silicone oil from intraocular lenses

Aim Adherent silicone oil on intraocular lenses (IOLs) following retinal detachment surgery induces large and irregular refractive errors and multiple images, and gives rise to glare, distorted and often poor vision. Its removal remains challenging, often requiring mechanical wiping or explantation. F4H5 is a new semifluorinated alkane into which silicone oil is readily soluble. The aim is to establish the effectiveness of F4H5 in removing silicone oil from three different types of IOL in vitro. Method Silicone lenses (Tecnis ZM900, Advanced Medical Optics, Inc.), hydrophobic acrylic lenses (MA60, Alcon Laboratories, Inc.) and PMMA lenses (Ocular Vision, Inc) were first immersed in phosphate-buffered saline, second in silicone oil, then in F4H5 (Fluoron GmbH) for 10 min and lastly vigorously agitated in F4H5 for 1 min. They were weighed at each stage using scales accurate to 0.0001 g to measure the weight of the adherent oil. Dynamic contact angle (DCA) analysis was used to assess their surface properties. Results Immersion in F4H5 alone removed 96.1% (±1.23) by weight of silicone oil from the hydrophobic acrylic lenses, 91.4% (±1.58) from the silicone and 95.6% (±1.44) from the PMMA IOLs. Immersion combined with 1 min of agitation increased the removal to 98.8% (±0.46) from the acrylic IOLs, to 93.7% (±0.48) from the silicone IOLs and to 100% (within ±0.0001 g) from every PMMA IOL. After treatment with F4H5, all IOL were optically clear. DCA hysteresis curves remained permanently altered. All measurements were highly reproducible. Conclusion F4H5 was highly effective at removing the bulk of the silicone oil from all three groups of IOL. The DCA measurements suggested that their surface properties were permanently modified.