Experimental vitreous and aqueous replacement with perfluorophenanthrene. Clinical, histologic, and electrophysiologic results

INCIDENCE OF AND RISK FACTORS FOR DISSOCIATED OPTIC NERVE FIBER LAYER AFTER EPIRETINAL MEMBRANE SURGERY

PURPOSE

To investigate the incidence of and risk factors for a dissociated optic nerve fiber layer (DONFL) after epiretinal membrane surgery.

METHODS

Two hundred and ninety-six primary pars plana vitrectomy operations for epiretinal membrane that were eligible for inclusion in the study. All patients received a complete ophthalmologic examination and color fundus photography, optical coherence tomography preoperatively and postoperatively. DONFL group and non-DONFL group was compared. Univariate and multivariate analyses were performed to establish the risk factors for DONFL.

RESULTS

A DONFL developed in 30 of the 296 eyes (incidence, 10.1%). Internal limiting membrane (ILM) peeling was performed in 29 of 30 eyes (96.7%) in the DONFL group and 126 of 266 eyes (47.4%) in the control group (P < 0.001). Intravitreal gas tamponade was performed in 21 eyes (70.0%) in the DONFL group and 133 eyes (50.0%) in the control group (P = 0.038). The ILM peeling (odds ratio, 32.22 [4.33-240.0]; P = 0.001) and intravitreal gas tamponade (odds ratio, 2.33 [1.03-5.28]; P = 0.042) were significantly associated with DONFL.

CONCLUSION

It was found that ILM peeling and intravitreal gas tamponade were correlated with postoperative DONFL. The ILM peeling with intravitreal gas tamponade was more strongly correlated with postoperative DONFL formation than was ILM peeling alone.

Retinal layers measurements in healthy eyes and in eyes receiving silicone oil-based endotamponade

Purpose

To characterize the concordance/symmetry of each retinal layers in individuals without macular pathology and to further characterize the localization of inner retinal thinning in eyes receiving silicone oil-based endotamponade.

Methods

Retinal layers of one hundred eyes of 50 individuals without macular pathology were imaged using spectral domain optical coherence tomography (SD-OCT) and manually segmented using ImageJ software (developed by Wayne Rasband, NIH, Bethesda, MD, USA). In the second part of the study, retrospective analysis of 3028 cases of pars plana vitrectomy in University Eye Hospital Cologne, Germany, was conducted, retrieving nine patients with silicone oil-based endotamponade with no macular condition interfering retinal layers measurements. These patients had retinal detachment not involving the macula due to various conditions. In these patients, retinal layer segmentation was performed and compared with the fellow eye.

Results

There is a moderate-to-high concordance for all retinal layers between the right and the left eye of the same individual. In eyes receiving silicone oil-based endotamponade, the inner retinal layers become subsequently thinner. Ganglion cell and inner plexiform layers contribute most to this thinning, that is, 0.537 ± 0.096 mm³ compared with 0.742 ± 0.117 mm³; p = 0.006. Outer retinal layers were not affected by silicone oil-based endotamponade (p = 0.439 for the differences of calculated outer retinal layers).

Conclusion

Ganglion cell and inner retinal layers become subsequently thinner after the use of silicone oil-based endotamponade. This study advocates the use of spectral domain optical coherence tomography for patient management with silicone oil endotamponade to early detect subsequent retinal thinning.

Unanticipated vision loss after pars plana vitrectomy

Although advances in vitreoretinal surgical techniques and technology have helped to minimize the risks associated with surgical manipulation of the retina, retinal pigment epithelium, and optic nerve, unanticipated or unexplained visual loss still occurs. We review causes of vision loss encountered after pars plana vitrectomy, including retinal toxicities, vascular events, and optic neuropathies, and we suggest strategies to limit or prevent them.

[Perfluorocarbon liquids and vitreoretinal surgery in 2011]

Perfluorocarbon liquids (PFCLs) are one of the most innovative recent tools for vitreoretinal surgery. PFCLs are characterized by their number of carbon atoms, which has an impact on the density, viscosity, surface tension, vapor pressure, the boiling point, and the refraction index. PFCLs are routinely used because of their high gravity (double that of water) and their low viscosity. Furthermore, they are immiscible in water, optically clear with refraction indices similar to that of water, allowing visualization of an interface between the PFCL and saline. The use of intravitreally injected liquid PFCLs as adjunctive agents to vitreoretinal surgery plays an important role in facilitating retinal reattachment, especially in cases of giant retinal tear, trauma, and/or proliferative vitreoretinopathy. PFCLs are also used as intraoperative instruments to re-establish intraocular volume, assist in separating membranes adherent to the retina (in proliferative diabetic retinopathy, for example), and manage the dislocated crystalline lens and intraocular lens.

High-density silicone oil (Densiron) as a primary intraocular tamponade: 12-month follow up

BACKGROUND

The high-density silicone oil (Densiron 68), a mixture of F6H8 with silicone oil, seems to be a therapeutic option, at least in selected patients with complex inferior retinal re-detachment, where standard procedures have already failed. In an interventional case series we used Densiron as a primary endotamponade.

METHODS

Twelve eyes of 12 patients aged 31 years to 85 years with inferior complex rhegmatogenous retinal detachment with secondary proliferative vitreoretinopathy (PVR) grades CP2 to CA8 were included. Surgical techniques (pars plana vitrectomy, membrane peeling, retinotomy, retinectomy, endophotocoagulation, cryocoagulation, endotamponade) did not include a scleral buckling procedure (except one eye). Mean duration of the Densiron endotamponade was 78.3 +/- 29.74 days, with a mean follow up after removal of 400.6 +/- 85.4 days.

RESULTS

After Densiron removal, four patients (33.3%) showed a stable reattached retina without further interventions, while, in six patients (50%), recurrent retinal re-detachment appeared during endotamponade, generally within 2 months. One patient (8.3%) developed re-detachment 5 months after Densiron removal. One eye (8.3%) lost light perception due to severe intraretinal fibrosis with chronic hypotonia, despite complete retinal re-attachment. Visual acuity improved from mean logarithm of the minimum angle of resolution (logMAR) of 2.95 +/- 1.21 to 1.87 +/- 1.32 (statistically significant, P = 0.022). Side effects included temporary inflammatory reaction/fibrin accumulation (n = 2/2), moderate-to-severe intraretinal fibrosis (n = 3), elevated intraocular pressure (IOP) (n = 3), emulsification (n = 2), sterile hypopyon (n = 1), vitreous haemorrhage (n = 1) and chronic hypotony (n = 1).

CONCLUSION

Primary anatomical success rate of 33.3% was less encouraging than as expected. Especially, re-detachments within the posterior staphyloma in highly myopic patients were common during Densiron endotamponade. However, the surgical success increased to 75% after reintervention, even without the use of an additional encircling band. The observed adverse effects and the functional outcomes do not contraindicate the use of Densiron as an internal tamponade for a period of 3 months.

Biocompatibility assessment of liquid artificial vitreous replacements: relevance of in vitro studies

The biocompatibility of liquid artificial vitreous replacements is generally assessed by performing tests in animal models before their clinical use, whereas in vitro experimentation is seldom carried out due to their physico-chemical characteristics. Since their introduction in vitreoretinal surgery, however, the use of some certified vitreous replacements has been discouraged after clinical trials, because of the occurrence of serious side effects. This observation suggests that the tests currently performed for biocompatibility assessment cannot fully guarantee their safety when they are used in humans. Here we review the available literature on in vitro biocompatibility testing of liquid artificial vitreous replacements and survey our own experience on the subject, obtained by using primary retinal cell cultures, seeded on micro-porous inserts. We suggest that in vitro biocompatibility assessment, conducted before experiments in animal models, could improve the required safety evaluation and decrease the risk of undesired side effects, as well as providing a beneficial reduction of animal experimentation.

Perfluoro-n-octane as a postoperative vitreoretinal tamponade in the management of giant retinal tears

BACKGROUND

Despite recent advances in giant retinal tear repair, retinal redetachment remains an issue. This may be due to inadequate retinal tamponade with silicone oil or perfluorocarbon gas that allows fluid to seep back under the edge of the tear. We propose short-term postoperative retinal tamponade with perfluoro-n-octane liquid to overcome this problem. Theoretical advantages include the reduced likelihood of proliferative vitreoretinopathy. It is easier to remove than silicone oil due to its lower viscosity, and supine posturing is more manageable from a patient perspective.

METHODS

A retrospective case series of 16 giant retinal tear repairs without significant proliferative vitreoretinopathy is presented. Lens-sparing vitrectomy was performed with endolaser to the edge of the tear and the entire retinal periphery. Scleral buckling was not utilized. Perfluoro-n-octane was used as a postoperative tamponade for a mean of 16.4 days (range, 6-50 days).

RESULTS

The retina was reattached at the end of the procedure in all 16 cases. Redetachment occurred in only 1 (6.3%) of 16 cases.

CONCLUSION

Postoperative tamponade with perfluoro-n-octane may decrease the rate of redetachment in giant retinal tear repair compared with silicone oil or perfluorocarbon gas alone. We found no adverse effects directly attributable to perfluoro-n-octane.

First experiences with high-density silicone oil (Densiron) as an intraocular tamponade in complex retinal detachment

BACKGROUND

In this study, we evaluated the anatomic and functional outcome and intraocular adverse effects after a 3-month endotamponade with Densiron 68, a mixture of F(6)H(8) with silicone oil, in complex inferior re-detachments.

METHODS

Forty-eight eyes of 48 patients aged 27-82 years with retinal re-detachment due to proliferative vitreoretinopathy (PVR) grades CP1 to CA7 were included. Mean duration of the Densiron endotamponade was 108.7+/-66.9 days, with a mean follow-up after removal of 102.8+/-31.9 days.

RESULTS

Twenty-two patients (45.8%) showed stable retinal reattachment after Densiron removal. Fourteen patients (29.2%) developed retinal re-detachment after removal, generally within 1 month and in the upper circumference (n=8). In 11 patients (22.9%) recurrent re-detachment (inferior n=8) appeared during Densiron endotamponade. In one eye (2.1%) treatment was primarily unsuccessful. Visual acuity improved from mean logMAR 1.66+/-1.03 to 1.47+/-0.97 (not statistically significant, P=0.257). Side effects included temporary inflammatory reaction (n=10), fibrin accumulation (n=6), sterile hypopyon (n=2), vitreous hemorrhage (n=6), elevated IOP (n=5), emulsification (n=4) and chronic hypotony (n=4).

CONCLUSION

The anatomical success rate without further interventions of 45.8% (22 of 48 patients) seems unsatisfactory. However, in evaluating the potential of Densiron, it should be considered that all patients in this study had previous surgery with standard procedures, including silicone oil, which had already failed. Intraoperative laser photocoagulation of the periphery of the upper quadrants might reduce the risk of retinal re-detachments.

ADVERSE SIDE EFFECTS WITH PERFLUOROHEXYLOCTANE AS A LONG-TERM TAMPONADE AGENT IN COMPLICATED VITREORETINAL SURGERY

BACKGROUND

To report long-term intraocular tolerance of perfluorohexyloctane (F(6)H(8)).

METHODS

F(6)H(8) was used as an endotamponade in 18 patients (9 male and 9 female) with a median age of 65 years (range, 14-82 years) and complicated pathologic conditions of the inferior fundus: rhegmatogenous retinal detachment (17 patients) and tractional retinal detachment owing to proliferative diabetic retinopathy (1 patient). In six eyes, additional proliferative vitreoretinopathy was present. The use of F(6)H(8) was primary in 2 patients, and 16 patients had had previous retinal detachment surgery (median number, 2). F(6)H(8) was left in the eye for a median duration of 8 weeks (range, 2-14 weeks).

RESULTS

The median follow-up period was 6 months (range, 3-18 months). Permanent reattachment was achieved in 10 (56%) eyes after removal of F(6)H(8). In 8 (44%) of 18 eyes, a redetachment occurred. Two eyes became phthisic. Adverse side effects included photophobia in two patients, pain in two, hypotony in four, early emulsification in one, corneal lesion in one, fibrinous membranes in five, posterior lens opacification in one, and retinal scar formation in one.

CONCLUSION

Perfluorohexyloctane provides good support to the inferior retina. Because of numerous adverse side effects, it should be considered carefully when used as a long-term tamponade. Early removal may reduce the number of side effects.

Management of traumatic retinal detachment with vitreon in children

PURPOSE

To report the use of perfluoroperhydrophenanthrene (vitreon) for traumatic retinal detachment in children.

METHODS

Vitreon was used as an intraoperative adjunct in 34 children with complicated retinal detachment secondary to penetrating and perforating trauma. The characteristics of the injuries, the final visual acuities, the postoperative complications and the rate of anatomic success were evaluated in a retrospective study.

RESULTS

Patients were followed-up an average of 20 months. Eighteen retinas (53%) were reattached, and the postoperative visual acuity was counting fingers or better in 9 cases (26%), and only 4 eyes saw better than 10/200 at last follow-up. Hypotony developed in 7 (21%) of 34 eyes.

CONCLUSION

Management of traumatic retinal detachment in children is difficult. Vitreon, as other perfluorocarbons, may be an effective intraoperative tool for vitreoretinal surgery in pediatric eyes that suffer trauma.

Comparative study of vitrectomy for dropped nucleus with and without the use of perfluorocarbon liquid. Clinical, electrophysiological and visual field outcomes

PURPOSE

To compare pars plana vitrectomy for dropped nucleus with and without perfluorocarbon liquid.

METHODS

24 eyes with dropped nucleus were randomized to undergo PPV with perfluorodecalin, (study, n=12) and without it (control, n=12). Visual acuity, IOP, visual evoked response and electroretinography were noted at study entry and up to 3 months after PPV. Humphrey perimetry was done at 3 months.

RESULTS

Final visual acuity was >20/60 in 75% of study eyes and 41.6% of controls. The two groups were statistically comparable with regard to the above parameters before PPV and during follow-up. The timing of vitrectomy did not significantly influence the final visual acuity. A higher rate of complications was seen in the control group.

CONCLUSIONS

Perfluorodecalin facilitated the procedure and possibly minimized complications, and was found to be safe for intraoperative use in terms of recovery of visual acuity, stable ERG and VER, and normal visual fields.

Effects of perfluorophenanthrene on the human corneal endothelium

PURPOSE

To evaluate long term effects of perfluorophenanthrene (C12F24), a perfluorocarbon fluid, in the anterior chamber of the human eye, where residual perfluorophenanthrene was retained in the eye postoperatively.

METHODS

Slit-lamp microscopic and specular microscopic examinations of 4 eyes of 4 patients were performed. All the eyes were operated for complicated retinal detachment and they were aphakic at the end of the operations. Mean follow-up period was 10 months (6-16 months).

RESULTS

Perfluorophenanthrene was seen in the anterior chamber in the first or second day postoperatively as a single drop. In the third week, postoperatively, the first signs of splitting the perfluorophenanthrene (fish egging phenomena) was observed. There was no sign of corneal or anterior segment toxicity with the slit lamp microscopic examinations and the intraocular pressure was within normal limits during the follow-up period in all eyes. However, some structural changes of the corneal endothelium were shown by specular microscopy. Decreased endothelial cell density, a reversed illumination pattern in which the normally dark cellular boundaries appear bright and intracytoplasmic light reflecting bodies were signs of cellular damage at the contact sites whereas no significant changes were seen at non contact sites.

CONCLUSION

Residual perfluorophenanthrene in the anterior chamber does not induce gross corneal damage or ocular inflammation, although structural changes indicating the damage of the corneal endothelium, can be shown by specular microscopy at the contact sites. Corneal endothelial changes seem to arise from a contact-dependent effect of the perfluorophenanthrene.

Biomaterials used in the posterior segment of the eye

The treatment of posterior segment eye disease and related conditions has improved greatly in recent years with the advent of new therapies, materials and devices. Vitreoretinal conditions, however, remain significant causes of blindness in the developed world. Biomaterials play a major role in the treatment of many of these disorders and the success rate of vitreoretinal surgery, especially in the repair of retinal detachment and related conditions, would increase with the introduction of new and improved materials. This review, which focuses on disorders that feature retinal detachment, briefly describes the anatomy of the eye and the nature and treatment of posterior segment eye disorders. The roles, required properties and suitability of the materials used in vitreoretinal surgery as scleral buckles, tamponade agents or drug delivery devices, are reviewed. Experimental approaches are discussed, along with the methods used for their evaluation, and future directions for biomaterial research in the posterior segment of the eye are considered.