Fluid-filled Eye Research Articles

Quality of view through extended depth of focus intraocular lens in a model eye.

To compare the quality of images viewed through an extended depth of focus (EDF) intraocular lens (IOL) to that through multifocal or monofocal IOL. Experimental study METHODS: EDF IOL (Symfony®, ZXR00V, Johnson & Johnson Vision), diffractive multifocal (ZLB00, + 3.25D or ZMB00, + 4.0D), or monofocal (ZCB00V) IOL with a spherical power of + 20.0 diopter (D) was placed in a fluid-filled model eye with corneal aberrations similar to those of human eyes. A United States Air Force Resolution Grating Target was glued to the posterior surface of the model eye and viewed through a flat contact lens, a 60D or 128D wide-angle non-contact lens (Resight®) or wide-angle contact lens (MiniQuad®). The contrast of the grating images recorded with the EDF and multifocal IOLs were compared to those through the monofocal IOL. The grating images viewed through the flat contact lens were slightly blurred when viewed through the EDF IOL but clearer than those through the multifocal IOLs with very blurred images in the periphery. The contrast of the images viewed through the EDF and multifocal IOLs through the flat contact lens was significantly lower than through the monofocal IOL (P < 0.02). The contrast of the images viewed through the EDF IOL with 60D or 128D wide-angle non-contact lens was significantly lower than through the monofocal IOL (P < 0.05) but not with wide-angle contact lens. Our results suggest that vitreous surgeons can accomplish a clearer view during vitrectomy in EDF IOL-implanted eyes with a wide-angle viewing contact lens and a flat contact lens than in multifocal IOL-implanted eyes.

Minification of fundus optical coherence tomographic images in gas-filled eye.

BackgroundOptical coherence tomography (OCT) is being used increasingly to evaluate and manage a variety of retinal diseases, but not much is known about the minification of the OCT images in gas-filled eyes. The purpose of this study was to investigate the effect of gas-filled eyes on the size of the OCT images.MethodsThis was retrospective case series of 81 consecutive eyes of 79 patients who had macular hole surgery between April 2012 and September 2014. Images of the optic disc were taken with a spectral domain-OCT instrument 2 days after surgery in gas-filled, pseudophakic eyes and from the same eyes but fluid-filled one month after the surgery. The vertical length, horizontal width, and the area of the optic disc were measured in the OCT images.ResultsClear images were obtained from 50 eyes of 49 patients (mean age 66.4 ± 5.9 years). The mean vertical length and mean horizontal width of the optic disc in the gas-filled eyes were about 25 % shorter than that of fluid-filled eyes (vertical, 1213.8 ± 170.5 and 1650.6 ± 195.9 μm, P < 0.01; horizontal, 1169.4 ± 143.1 and 1526.4 ± 219.9 μm, P < 0.01). The mean area of the optic disc was 1.12 ± 0.34 mm2 in gas-filled eyes which was significantly smaller than that in fluid-filled eyes (1.88 ± 0.37 mm2) by 40.4 %.ConclusionsThe fundus images of gas-filled eyes are significantly smaller than that in the same fluid-filled eyes. The minification of the OCT images should be considered when analyzing images obtained from gas-filled eyes.Trial registrationTrial registration number: UMIN000007517. Date of registration: 3/21/2012.Electronic supplementary materialThe online version of this article (doi:10.1186/s12886-016-0306-1) contains supplementary material, which is available to authorized users.

Clinical Outcomes of Minimal Exposure to Indocyanine Green-Assisted Peeling of the Internal Limiting Membrane

Purpose: To evaluate the clinical outcomes of epiretinal membrane (ERM) surgery with minimal exposure to indocyanine green (ICG) dye-assisted internal limiting membrane (ILM) peeling compared with no ICG dye. Methods: We divided 33 eyes with ERM treated by vitrectomy into 2 groups. ICG dye was used in the first group of 18 eyes (ICG group) but not in the second group of 15 eyes (no dye [ND] group). In the ICG group, 0.25% diluted ICG dye was injected into the fluid-filled eye and removed with a back-flushing needle after 3-5 seconds to peel ILM. Value changes in several parameters including visual acuity, central macular thickness, Humphrey automated kinetic perimetric analysis, and peripapillary retinal nerve fiber layer (RNFL) thickness were followed up and compared according to ICG dye use. Results: No differences were found between the 2 groups in terms of visual acuity, central macular thickness, and peripapillary RNFL thickness preoperatively and at 6 months postoperatively (p = 0.125 for visual acuity, p = 0.734 for central macular thickness, p = 0.615 for RNFL thickness). Six months after surgery, no significant increase was found in any region of visual field in the ICG group (p = 0.392). The visual field was significantly increased in the superior region in the ND group (p = 0.042). The RNFL thickness in the temporal quadrant was significantly reduced at 6 months postoperatively compared to baseline values in both groups (p = 0.011 for ICG group, p = 0.042 for ND group). Conclusions: ICG dye-assisted ILM peeling does not aggravate clinical outcomes of ERM surgery in terms of visual acuity, central macular thickness, visual fields, or RNFL thickness and can be safely utilized with proper techniques. J Korean Ophthalmol Soc 2015;56(10):1572-1579

TRANS-TAMPONADE OPTICAL COHERENCE TOMOGRAPHY

To investigate the feasibility of trans-tamponade optical coherence tomography and evaluate factors contributing to image quality and acquisition success. Retrospective case series of eyes receiving Postoperative Day 1 optical coherence tomography imaging after vitrectomy and gas tamponade. The quality of the scans was graded by three independent expert readers. Clinical and surgical variables were recorded and correlated with scan quality. Eighty eyes were included in the study. An image quality classification scheme was developed (0-4, 0 = no image and 4 = comparable quality to trans-fluid optical coherence tomography). In 51 scans (64%), visualization of the inner retina and retinal pigment epithelium was achieved (Grades 2-4) but with variable image quality of the retinal layers. Twenty-nine scans (36%) achieved visualization of all retinal layers (Grades 3-4). Only 9 scans (11%) were of comparable quality to fluid-filled eyes (Grade 4). Pseudophakia (P = 0.0001), shorter operative times (P = 0.007), and macular surgery (P = 0.002) correlated with scan quality. An optimum scan protocol was developed to facilitate maximum quality images. Successful trans-tamponade optical coherence tomography through gas on Postoperative Day 1 is possible but significant variability exists in scan quality.

Intraoperative assessment of intraocular pressure in vitrectomized air-filled and fluid-filled eyes

To ascertain the difference of intraocular pressure (IOP) measurement between vitrectomized air-filled and fluid-filled eyes. Thirty-one eyes of 31 consecutive patients who underwent conventional vitrectomy and intraocular gas tamponade were assessed. After vitrectomy, IOP of the fluid-filled eyes was measured by Tono-Pen. Thereafter, fluid-air exchange was performed, and IOP of the air-filled eyes was measured again. The IOP within each fluid- and air-filled eye was varied by selecting settings on the vitrectomy system, from 10 to 50 mmHg with 5-mmHg increments. Postoperatively, IOP was assessed by both Tono-Pen and Goldmann applanation tonometry (GAT). Linear and nonlinear regression analyses were conducted between intraoperatively measured Tono-Pen readings and actual IOPs. Bland-Altman plot was used to assess the agreements between postoperatively measured Tono-Pen readings and GAT readings. The discrepancy between Tono-Pen readings and actual IOP in fluid-filled eyes was not significant, except for the profound high pressures over 45 mmHg. However, Tono-Pen readings in air-filled eyes were significantly lower than actual IOPs in all ranges, and Tono-Pen increasingly underestimates IOP at higher levels. Intraoperative Tono-Pen readings were correlated significantly with actual IOP and a quadratic equation evidenced the best fit (R(2) = 0.996). Postoperatively, difference of the measurements between Tono-Pen and GAT was not significant. Tono-Pen and GAT significantly underestimate actual IOP in air-filled eyes. It should be considered that actual IOP would be greater than the measured IOP in gas-filled eyes, even though the IOP is measured as normal.

An Optomechanical Model Eye for Ophthalmological Refractive Studies

To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery.

Incidence of postoperative hypotony in 25-gauge vitrectomy: oblique versus straight sclerotomies

ObjectiveTo compare the incidence of hypotony after oblique and straight sclerotomies in 25-gauge transconjunctival sutureless vitrectomy (TSV). DesignRetrospective, comparative, interventional case series. ParticipantsTwo hundred seventy-five eyes of 250 patients. MethodsWe reviewed 275 consecutive cases of 25-gauge TSV. Oblique incisions were performed on 141 eyes and straight incisions on 134 eyes. ResultsOn postoperative day 1, there was no significant difference in the incidence of hypotony (9.9% vs. 9.2%; p = 0.85) between oblique and straight incisions. The type of incision showed no statistical effect on hypotony in eyes filled with fluid (p = 0.91) or air-gas (p = 0.81). Hypotony was significantly reduced using air-gas endotamponade (4.8%) as compared to fluid-filled eyes (20.0%; p = 0.0001). ConclusionOblique incisions do not reduce the incidence of postoperative hypotony in fluid-filled eyes or with air-gas tamponade. Air-gas tamponade use results in a 4-fold reduction in the incidence of hypotony.

EFFECT OF INTRAVITREAL GAS TAMPONADE FOR SUTURELESS VITRECTOMY WOUNDS

To investigate the effect of gas tamponade on wound closure and postoperative hypotony by comparing fluid-filled and gas-filled eyes after 25-gauge sutureless vitrectomy using three-dimensional corneal and anterior segment optical coherence tomography. Twenty-four eyes of 24 patients who underwent a 25-gauge transconjunctival sutureless vitrectomy were included in this prospective study. A total of 72 scleral wounds were observed using three-dimensional corneal and anterior segment optical coherence tomography at 3 hours and at 1, 3, 7, and 14 days postoperatively. Scleral wound closure was defined as the absence of a scleral gap at the sclerotomy site, as observed using three-dimensional corneal and anterior segment optical coherence tomography. The rate of wound closure, intraocular pressure, and the incidence of complications were compared between the fluid- and gas-filled eyes. The rates of scleral wound closure at 3 hours and at 1, 3, 7, and 14 days were 26.2%, 28.6%, 35.7%, 52.4%, and 85.7% in fluid-filled eyes and 53.3%, 73.3%, 76.7%, 83.3%, and 93.3% in gas-filled eyes; these rates were significantly higher for the gas-filled eyes. The intraocular pressure was significantly higher in the gas-filled eyes than in the fluid-filled eyes on postoperative Day 1 but did not differ significantly between the 2 groups on postoperative Day 3 and thereafter. Three-dimensional corneal and anterior segment optical coherence tomography provided clear images of 25-gauge sutureless vitrectomy wounds and revealed that the sclerotomies closed faster in gas-filled eyes than in fluid-filled eyes. Thus, gas tamponade might be effective for the closure of sutureless vitrectomy wounds.

Transvitrectomy injection of low-viscosity substances

Sir, Ghosh et al.1 present three cases of inadvertent trypan blue injection into the subretinal space and suggest an alternative safer method of injection into the vitreous cavity using a backflush flute. Low-viscosity substances such as stains, triamcinolone, and heavy liquids are commonly used during vitrectomy surgery. We would like to suggest an alternative method of injecting any of these substances—that of injection through the vitrectomy probe itself. A three-way tap is inserted into the distal split point in the aspiration tubing of the vitrectomy probe and a syringe containing the low-viscosity substance is attached (Figure 1). To allow injection, the three-way tap is turned to close off the aspiration line to the vitrectomy pump and the substance injected via an assistant, with the surgeon directing the port of the probe to the desired location. After injection, the three-way tap is again turned off to the line, allowing active aspiration from the eye. Figure 1 Three-way tap turned towards aspiration line for transvitrectomy injection. The advantages of the system are that the injection is directed through the side port of the probe and hence not directly towards the retina, thus reducing the risk of subretinal injection. Furthermore, the injection can be directed to the area of interest, for example, peripheral membranes. There is no need to enter and exit the eye for injection or aspiration of the injected substance, thus reducing potential retinal tear formation and pathogen entry into the eye. A couple of points regarding the technique are worth observing. There is some dead space between the injection point on the three-way tap and the cutter port. With the set-up we have used this is ∼0.45 ml. This volume is irrelevant in terms of heavy liquids and diluted triamcinolone, but is more significant with low-volume membrane stains. We have, however, found that there is sufficient volume in the stains we have used to provide adequate staining. It is also important for the three-way tap to be primed with the infusion solution at the start of the case to avoid air injection during injection, which is important when injecting into a fluid-filled eye. In conclusion, this is a simple and safe technique that reduces instrument exchange and improves surgical flow.

Vital staining with indocyanine green: a review of the clinical and experimental studies relating to safety

Indocyanine green (ICG) is extremely effective when used as a vital stain during macular hole surgery. By staining the internal limiting membrane, ICG facilitates removal of this delicate and sometimes hard to visualize structure. There is, however, considerable debate regarding its safety. This review considers the clinical and experimental studies of ICG and a related agent, infracyanine green. Some clinical papers show visual field defects, reduced visual acuity, and persistence of ICG at the macula and optic nerve. Other clinical studies fail to demonstrate toxicity. The experimental studies are also conflicting, but there are emerging trends. These suggest that surgeons who continue to use ICG should use concentrations not greater than 0.05 mg/ml, in fluid-filled eyes, with short exposure times, iso-osmolar solutions, and avoid proximal or prolonged endoillumination of stained tissue. A smaller number of studies suggest that infracyanine green produces similar staining to ICG, and may possibly be safer, but there are too few well-designed studies to reach a conclusion. Although the use of ICG continues, on the balance of evidence, this review suggests that it is has the potential to produce subtle visual damage.

Wound Leakage and Hypotony After 25-Gauge Sutureless Vitrectomy: Factors Affecting Postoperative Intraocular Pressure

To investigate the factors related to postoperative hypotony after 25-gauge sutureless vitrectomy. Of 109 consecutive eyes undergoing sutureless vitrectomy, 95 fluid-filled eyes were randomly assigned to three groups according to the order of infusion cannula removal. In group 1 (30 eyes), the infusion was removed first. In group 2 (32 eyes), the infusion was removed after another cannula. In group 3 (33 eyes), the infusion was removed last. Intraocular pressure (IOP) was measured on preoperative day 1 and postoperative days 1, 7, and 30. Mean age was 58.9 +/- 11.6 years (range: 18 to 80 years). Among each factor (including order of infusion removal, age, sex, axial length, preoperative IOP, previous vitrectomy, indications for vitrectomy and lens status), only age was significantly correlated with IOP on postoperative day 1 (P = .019). In 13 eyes in which hypotony persisted through postoperative day 2 (IOP < or = 5 mm Hg), the age of the patients was significantly younger than those who did not experience persisting hypotony (P = .006). Younger patients were more likely to experience early postoperative hypotony.

Postoperative Complications Associated With 25-Gauge Pars Plana Vitrectomy

To report postoperative complications in eyes undergoing 25-gauge pars plana vitrectomy (PPV). Seventy consecutive eyes that underwent 25-gauge PPV for various indications, including epiretinal membrane, non-clearing vitreous hemorrhage, and idiopathic macular hole, and had a minimum follow-up of 12 weeks were reviewed retrospectively. Main outcome measures included best-corrected Snellen visual acuity, intraocular pressure (IOP), intraoperative complications, and postoperative complications. The mean visual acuity improved from 20/368 preoperatively to 20/105 postoperatively (P < .00005). Intraoperative complications included retinal tears in 2 eyes (2.9%). Postoperative complications included cataract progression in 17 eyes (42.5%), cystoid macular edema exacerbation in 5 eyes (7.1%), and retinal detachment in 1 eye (1.4%). Postoperative day 1 IOP was statistically lower than preoperative IOP in fluid-filled eyes (P = .031) but not in eyes filled with intravitreal air (P = .30) or gas (P = .52). Sclerotomy sutures were required intraoperatively in 5 eyes (7.1%) and postoperative day 1 hypotony was noted in 4 eyes (5.7%). All of these complications were noted in fluid-filled eyes except for one case of postoperative day 1 hypotony with gas tamponade. Intraoperative and postoperative complications were rare in this series of 25-gauge PPV. Postoperative cataract progression and hypotony were the most common complications. Fluid-filled eyes appear to have a higher risk of wound leakage and postoperative hypotony after 25-gauge PPV than eyes with air or gas tamponade.

Einfluss von Vitalfarbstoffen auf die Funktion der äußeren Blut-Retina-Schranke in vitro

The use of vital dyes in "chromovitrectomy" allows the easier removal of less recognizable structures like epiretinal membranes (EM) or the inner limiting membrane (ILM). In recent years numerous studies demonstrated the use of indocyanine green (ICG), trypan blue (TB) and patent blue (PB) for this indication. Reports of the possible risk of these dyes, i. e. especially ICG, in respect of reduced visual acuity results, possible visual field defects or alterations of the retinal pigment epithelium (RPE) resulted in limitations in their application. Human RPE cells and choroidal endothelial cells were cultured in monolayers on semipermeable membranes representing an in vitro model of the outer blood-retinal barrier. By measurement of the transepithelial electrical resistance (TER) the stable barrier function was determined. Two different models representing an air-filled and a fluid-filled eye were tested on the one hand by addition of the dye to the culture medium and, on the other, by direct application on the cell monolayer. In these two models ICG (5 mg/ml, 0.5 mg/ml, 0.125 mg/ml), TB (1.5 mg/ml, 0.15 mg/ml) and PB (2.4 mg/ml, 0.24 mg/ml) were applied for three minutes and the influence on the barrier function was determined. RPE cell growth was also tested in these two models after the application of ICG, TB and PB. Finally, monolayers of RPE cells were evaluated by transmission electron microscopy (TEM). After application of TB, PB and the lowest concentration of ICG of 0.125 mg/ml, the TER remained stable in both models. In contrast, ICG in a concentration of 5 mg/ml and 0.5 mg/ml caused a significant TER decrease in the model of the air-filled eye, whereas no influence on the function of the outer blood-retinal barrier was noted in the model of the fluid-filled eye. RPE cell growth rates were not influenced by the addition of the vital dyes, with the exception of ICG in a concentration of 5 mg/ml in the model of the air-filled eye, resulting in a temporary reduction of the cell count. In good correspondence to these results also in TEM intercellular blisters were noted after application of 5 mg/mL ICG for 3 minutes in the model of the air-filled eye. However, damage to the RPE cells themselves was not obvious. No pathological changes in the TEM were noted after application of TB and PB. The use of PB and TB at the posterior eye segment seems to be safe concerning damage to the PRE and its barrier function. In contrast, ICG in higher concentrations and with longer application times may cause a toxic effect on RPE morphology and function.

Vitrectomy surgery increases oxygen exposure to the lens: A possible mechanism for nuclear cataract formation

To report vitreous oxygen tension before, immediately after, and at longer times after vitrectomy. A prospective, interventional consecutive case series. Oxygen was measured using an optical oxygen sensor in patients undergoing vitrectomy. Intraoperatively, oxygen measurements were taken before and after vitrectomy in two intraocular locations: adjacent to the lens and in the mid-vitreous. Sixty-nine eyes underwent oxygen tension measurements at the time of vitrectomy. In baseline eyes, oxygen tension in the vitreous was low, measuring 8.7 +/- 0.6 mm Hg adjacent to the lens and 7.1 +/- 0.5 mm Hg in the mid-vitreous. The difference between the two locations was statistically significant (P < .003), indicating that vitreous gel maintains an intraocular oxygen gradient. Immediately after vitrectomy, oxygen tension in the fluid-filled eye was higher, measuring 69.6 +/-4.8 mm Hg adjacent to the lens and 75.6 +/- 4.1 mm Hg in the mid-vitreous. There was no statistically significant oxygen gradient between the two locations. The difference in oxygen tension pre- and postvitrectomy is highly statistically significant (P < .0001 lens, P < .0001 mid-vitreous). In eyes with a history of vitrectomy and previous removal of the vitreous gel, the intraocular oxygen tension was significantly higher than in eyes with a formed vitreous gel undergoing a first vitrectomy (P < .02 lens, P < .003 mid-vitreous). Vitrectomy surgery significantly increases intraocular oxygen tension during and for prolonged periods after surgery. This exposes the crystalline lens to abnormally high oxygen and may lead to nuclear cataract formation.

EFFECTS OF INDOCYANINE GREEN ON THE RETINA AND RETINAL PIGMENT EPITHELIUM IN A PORCINE MODEL OF RETINAL HOLE

This study was designed to emulate human macular hole surgery and to test the effects of indocyanine green (ICG) on the retina and retinal pigment epithelium (RPE). Yorkshire Cross pigs (n = 23) underwent vitrectomy, separation of the posterior cortical vitreous, and creation of a single retinal hole. In three study groups (n = 6, each group), air-fluid exchange was performed, following which balanced salt solution (BSS), 1.0% ICG, or 0.5% ICG was applied over the retinal hole. In one additional group (n = 5), 0.5% ICG was injected into the fluid-filled eye. At 4 weeks, the eyes were examined clinically, and fundus photographs were obtained before enucleation and light microscopic examination. Clinical evaluations documented a statistically significant difference between study groups (P = 0.036). There was a higher rate of moderate or severe RPE atrophy among animals where 1% or 0.5% ICG was applied in air-filled eyes (83% and 67%, respectively) compared with BSS controls (17%) and fluid-filled eyes receiving 0.5% ICG (40%). Histologic evaluation demonstrated a statistically significant difference between groups (P = 0.044), with extensive outer retinal degeneration observed in air-filled eyes receiving 1% or 0.5% ICG (66% and 60%, respectively) compared with BSS controls or fluid-filled eyes receiving 0.5% ICG (none of the eyes in either group). None of the study groups had any changes in the inner retina except at the retinal hole site. Retina exposed to ICG concentrations used in human vitreoretinal surgery had greater RPE atrophy and outer retinal degeneration than control eyes undergoing the same surgery without ICG. Eyes filled with infusion fluid during ICG injection had less damage to the RPE and outer retina than did air-filled eyes receiving ICG.

Cataract after Vitrectomy in Young Patients

The purpose of the study was to evaluate the occurrence of cataract in young patients after pars plana vitrectomy. The authors reviewed the medical records for previtrectomy and postvitrectomy lens changes in patients younger than 30 years of age at the Kellogg Eye Center, University of Michigan. Forty-nine patients (50 eyes) younger than 30 years of age (mean age, 23.5 years; range, 5 months-30 years) underwent phakic vitrectomy over a 12-year period. Cataracts were categorized as posterior subcapsular, nuclear sclerotic, or cortical. Cataracts also were graded as mild (1+), moderate (2+), or severe (3+). In this series of young patients, vitrectomy was performed for a wide range of ocular conditions, including trauma and complicated retinal detachment. Postvitrectomy cataract developed in 29 patients (60%). Eighteen patients (36%) had visually significant cataract on long-term follow-up (mean follow-up, 29.7 months; range, 6 months-13 years). The most common cataract was posterior subcapsular (57%), followed by nuclear sclerosis (23%), a combination of both (17%), and cortical cataract (3%). Patients with gas-filled eyes had a significantly higher rate of cataract formation than patients with fluid-filled eyes (P < 0.05). Postvitrectomy cataracts were more common in the authors' series compared with those of previous reports on young patients. Cataracts were most often posterior subcapsular and were significantly associated with the use of intraocular gas. The occurrence of postvitrectomy cataract appears to be higher in patients undergoing vitrectomy for complex ocular conditions, regardless of age.

Hemostatic Effects of Air Versus Fluid in Diabetic Vitrectomy

The potential hemostatic effect of an intravitreal air bubble after diabetic vitrectomy was studied in an animal model and in a randomized clinical trial. One day after vitrectomy with induced intraoperative hemorrhage, vitreous cavity hemorrhage was present in 60% of air-filled rabbit eyes compared with 27% of fluid-filled eyes. The prevalence and extent of hemorrhage was equal in the two groups on postoperative days 3 and 7. In a clinical trial of 51 eyes undergoing diabetic vitrectomy, 70% of eyes randomized to air-filled vitreous cavity after vitrectomy had vitreous cavity hemorrhage on postoperative day 1 compared with 50% of fluid-filled eyes. At 1 week, the incidence of hemorrhage was 78% for air and 61 % for fluid. The 6-month visual and anatomic results were similar in both groups. These findings suggest that an intravitreal air bubble neither improves hemostasis nor reduces the visual outcome after diabetic vitrectomy.

Effect of silicone oil on experimental traction retinal detachment.

The use of silicone oil as a retinal tamponade in the treatment of proliferative vitreoretinopathy is often complicated by membrane reproliferation. We studied the development of traction retinal detachments following the intravitreal injection of 15,000 retinal pigment epithelial cells in silicone-, perfluoropropane-, and fluid-filled rabbit eyes. By 28 days a higher proportion of silicone-filled eyes (83%) had severe proliferative vitreoretinopathy than either the perfluoropropane-filled (30%) or fluid-filled (10%) eyes. An in vitro proliferation assay using the vitreous samples showed that the silicone-filled vitreous had increased mitogenic activity for retinal pigment epithelial cells compared with the gas-filled or fluid-filled vitreous. Silicone oil appears to increase proliferation by stimulating the release of more or different mitogenic factors as well as by concentrating active factors into a smaller volume near the retina.