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Biomedical subjects

Timothy L Jackson

Publications and source records attributed to Timothy L Jackson.

At least 19 recordsLinked to original sources
PubMed2006

Identification of retinal breaks using subretinal trypan blue injection.

PURPOSE: To describe the use of subretinal trypan blue to identify retinal breaks during vitrectomy for rhegmatogenous retinal detachment (RD). DESIGN: Interventional case series. PARTICIPANTS: Five patients with RD in whom no retinal break could be identified by internal search with scleral indentation. METHODS: Trypan blue 0.15% was injected transretinally into the subretinal space using a 41-gauge cannula designed for macular translocation surgery. Perfluorocarbon heavy liquid was then injected into the vitreous cavity and the eye was rotated such that trypan blue was vented out of the break. The plume of trypan blue was used to identify retinal breaks, or in some cases staining of the break facilitated break detection. Subretinal fluid was then drained through the break or a drainage retinotomy and surgery was completed using standard techniques. MAIN OUTCOME MEASURE: Identification of previously unseen retinal breaks. RESULTS: This technique successfully identified a retinal break in 4 out of 5 patients. After absorption of the gas tamponade all retinas remained attached with a median visual acuity of 6/12. CONCLUSION: Failure to identify a retinal break during RD surgery is a well-recognized clinical challenge that may adversely affect outcome. In this setting, chromophore-assisted retinal break detection may be a useful surgical technique.

Adolescent↗
PubMed2006

Safety testing of indocyanine green in an ex vivo porcine retina model.

PURPOSE: To assess retinal toxicity of indocyanine green (ICG) in a porcine ex vivo perfusion organ culture model, and to measure intraretinal penetration of ICG applied to the retinal surface. METHODS: The retinal surface of fresh porcine retinal tissue was exposed to ICG 0.1% and 1% dissolved in glucose 5% for 1 and 30 minutes with and without concomitant illumination. Specimens were then kept in perfusion organ culture for 24 hours before examination by light microscopy and the TUNEL technique. Tissue samples treated with DNAse served as positive controls, and samples exposed to saline served as negative controls. Fluorescence microscopy was used to localize ICG at 1 minute, 60 minutes, 2 hours, and 3 hours after a 1-minute exposure of the retinal surface to ICG 1%. RESULTS: No increase in TUNEL-positive cells was observed after exposure to ICG 0.1% for 1 minute. Moderate apoptosis was found after 1-minute exposure to ICG 1% and 30-minute exposure to ICG 0.1%, and severe apoptosis was found after 30-minute exposure to ICG 1%. Concomitant application of light did not influence the degree of apoptosis. No signs of cell necrosis were found. After 1-minute exposure of the retinal surface, ICG 1% gradually penetrated the entire retina. CONCLUSIONS: ICG induced apoptosis but not necrosis in all nuclear retinal layers in a dose-dependent manner. Brief exposure to ICG 0.1% for 1 minute and illumination for 3 minutes simulated the intraoperative use of ICG. No retinal apoptosis or necrosis was observed. ICG briefly applied to the retinal surface gradually penetrated the entire retina.

Animals↗
PubMed2006

Human scleral hydraulic conductivity: age-related changes, topographical variation, and potential scleral outflow facility.

PURPOSE: To measure the specific hydraulic conductivity (K) of human sclera over a range of ages, to assess topographical variation, and to provide a theoretical estimate of potential scleral outflow facility. METHODS: Human donor sclera (n = 18; mean age 56.7 +/- 25.9 years; range 4-89) was clamped in a modified Ussing chamber connected to a water column set at 15.7 mm Hg. Column descent was measured over 24 hours at 20 degrees C with a digital micrometer. Scleral thickness of glutaraldehyde-fixed specimens was measured by light microscopy, taking the mean of 15 measurements per donor. Topographical variation in hydraulic conductivity (HC) was determined in an additional 10 donor eyes (mean age, 54.1 +/- 26.4 years; range 12-89), comparing anterior, equatorial, and posterior sclera. The potential transscleral outflow facility was calculated by multiplying HC by total scleral surface area and adjusting water viscosity to core body temperature. RESULTS: Mean K +/- 1SD in adults (>18 years) was 5.85 +/- 3.89 x 10(-18) m(2). K tended to be higher in pediatric donors, but there was no statistically significant age-related change. However, when all data sets were combined (n = 28), HC showed a significant decline with age. There was no significant topographical variation in HC. The potential transscleral outflow facility was 0.33 microL.min(-1).mm Hg(-1). CONCLUSIONS: Quantifying HC may help refine ocular pharmacotherapy, as transscleral water movement increases intraocular drug elimination and impedes transscleral drug delivery. The potential scleral outflow is two to three times higher than that which occurs in vivo; hence, medical or surgical interventions that fully exploit this pathway have considerable capacity to lower intraocular pressure.

Adolescent↗
PubMed2005

Effect of taurine and apical potassium concentration on electrophysiologic parameters of bovine retinal pigment epithelium.

The purpose of this study was to assess the effect of taurine and apical potassium concentration modelling in vivo light evoked changes on the transepithelial potential (TEP) and the transepithelial resistance (TER) of isolated bovine retinal pigment epithelium (RPE). Isolated specimens of bovine non-tapetal RPE-Bruch's-choroid (RPE-BC) were mounted in modified Ussing chambers. The apical and the basolateral side of the preparations were exposed to 10 mm and 10 microm concentrations of taurine in Krebs' medium with either 6.04 or 2.2 mm potassium in the apical compartment. TEP and TER were recorded over 140 min. TEP and TER decreased with exposure to taurine over the course of 1 hr followed by a stabilisation. The degree of this response did not depend on the concentration of taurine but was more pronounced when taurine was added to the apical compartment. Lowering apical potassium from 6.04 to 2.2 mm further pronounced the decrease of TEP and TER. The data show that light-induced release of taurine from the outer retina and light-induced decrease of the potassium concentration in the subretinal space synergistically lead to a temporary decrease in TEP and TER. Thereby, taurine uptake into the RPE is reduced probably by a reduction of the activity of the electrogenic Na+/taurine co-transporter of the apical RPE cell membrane. The findings suggest a mechanism whereby the sustained presence of taurine in the interphotoreceptor matrix following exposure to light may protect photoreceptor outer segments from light-induced oxidative stress.

Animals↗
PubMed2005

An experimental method for testing novel retinal vital stains.

There is uncertainty surrounding the safety of the vital stains currently used to assist macular surgery, and there may be other agents that are more suitable. This study aimed to validate a method of screening retinal vital stains for their potential surgical utility. Bovine retina was exposed to test agents at a range of concentrations. Masked observers determined the minimum dye concentration that reliably stained the retina, defined as the minimum visible concentration (MVC). Computer image analysis (CIE94 colour difference equation) was used to estimate the magnitude of the colour difference between stained and unstained retina. Agents that had favourable staining characteristics underwent safety testing using a retinal pigment epithelium and glial cell culture model. Cells were exposed to each agent and viability was assessed with a mitochondrial enzyme (MTT) assay, and fluorescent live-dead probe (ethidium homodimer-1/calcein-AM). Frozen sections were used to determine which retinal layers were stained. Techniques were tested on the following agents: alcian blue; diethyloxadicarbocyanine; Evan's blue; fast green; fluorescein; Janus green; methylene blue; naphthol green; neutral red; procian (reactive) yellow; rose bengal; and trypan blue. For most dyes, the results of image analysis showed that colour differences increased linearly with dye concentration, although some displayed a more exponential relationship. Five agents showed favourable staining characteristics: Evan's blue, rose bengal, naphthol green, neutral red, and trypan blue (MVC 0.02, 0.01, 0.1, 0.002, 0.01%, respectively). Safety testing of these five agents did not show toxicity, except in glial cells exposed to rose bengal. Relative to the negative control (saline), these showed a 48% reduction in viability using the MTT assay (p<0.001; t=4.71; CI 30-75%), and qualitative damage on fluorescence microscopy. Frozen sections showed that some agents produced diffuse staining of all retinal layers, others produced selective inner retinal staining. There are thousands of biological stains available and many of these may be more effective or safer than those currently used for retinal surgery. This study provides a means of screening potentially useful vital stains.

Animals↗
PubMed2005

Comparison of the Bain system and Uniflow universal anaesthetic breathing systems in spontaneously breathing young pigs.

OBJECTIVE: To compare minimum fresh gas flow (V(min)) requirements and respiratory resistance in the Uniflow and Bain anaesthetic breathing systems used in the Mapleson D mode. Animals Seven pigs, aged 8-12 weeks, anaesthetized for ophthalmic surgery. MATERIALS AND METHODS: Anaesthesia was maintained with halothane delivered in oxygen using a (Mapleson D) Bain breathing system. The V(min) that prevented re-breathing was found, and peak inspiratory (PIP) and peak expiratory (PEP) pressures measured. The fresh gas flow (V(f)) was then increased to V(min) + 50%, then V(min) + 100%, and respiratory pressures re-measured. A heat and moisture exchanger (HME) was inserted at the endotracheal tube and the procedure repeated. The breathing system was then exchanged for a Uniflow and the protocol repeated. After final disconnection from the breathing system, the animals' peak inspiratory and expiratory flows, tidal, and minute volumes (Vm) were measured over five respiratory cycles. RESULTS: The V(min) (L minute(-1); mL kg(-1) minute(-1)) required to prevent rebreathing in the Uniflow system [8.1(mean) +/-1.7 (SD); 332 +/- 94] was significantly greater than the Bain system (6.5 +/- 1.1; 256 +/- 64). At V(min), PEP with the Uniflow (3.5 +/- 0.1 cm H(2)O) was significantly higher than the Bain system (2 +/- 0.7 cm H(2)O), but PIP values did not differ (Uniflow -0.6 +/- 2.1 cm H(2)O; Bain system -0.2 +/- 0.6 cm H(2)O). With both systems, PEP increased significantly (p < 0.001) with each increase in V(f): Uniflow system 4.2 +/- 0.4 (V(min) + 50%) and 5.5 +/- 0.5 cm H(2)O (V(min) + 100%); Bain system 2.8 +/- 0.7 (V(min) + 50%) and 3.5 +/- 0.7 cm H(2)O (V(min) + 100%). Insertion of the HME did not alter pressures. The mean tidal volume was 6.4 +/- 1.6 mL kg(-1); mean Vm was 184.9 +/- 69.8 mL kg(-1) and mean respiratory rate was 28 +/- 5 breaths minute(-1). In one pig breathing with the Uniflow system PEP rose sharply; respiratory and heart rates increased, and ventricular dysrhythmias occurred. When the system was changed and V(f) reduced, physiological variables became normal. CONCLUSION: The study discredited the hypothesis that the two breathing systems behave similarly. Values for V(min) and PEP were higher with the Uniflow system. Increasing V(f) increased PEP with both systems. Insertion of an HME did not affect respiratory pressures. CLINICAL RELEVANCE: The Uniflow used in Mapleson D mode is not suitable for anaesthesia in young spontaneously breathing pigs.

Anesthesia, Inhalation↗
PubMed2004

Orientational contrast sensitivity and chromatic contrast thresholds in multiple sclerosis.

PURPOSE: To investigate abnormalities of orientational contrast sensitivity (CS) and chromatic contrast threshold (CCT) in multiple sclerosis (MS). DESIGN: Case control study. METHODS: Nine subjects (mean age, 42 +/- 11 years; range, 20-62 years) with MS, an expanded disability status scale of 3 or less, and normal visual acuity (VA) (logarithm of the minimum angle of resolution [logMAR] VA less than.1) in the tested eye were age-matched with 20 controls. Achromatic CS and CCT were measured using static, computer-generated sinusoidal gratings displayed on a high-resolution monitor. The CS and CCT of each subject were determined using a randomized double-staircase reversal algorithm; CS was measured at five spatial frequencies with horizontal orientation and three with vertical orientation; CCT was measured along the red-green and tritan confusion axes. The sensitivity thresholds of subjects were examined in relation to the mean sensitivity of controls for each spatial frequency. RESULTS: Two subjects had loss of horizontal and vertical CS, and three had isolated vertical loss. When compared with the control mean, there were significant reductions in red-green (P =.016) and tritan (P =.016) discrimination thresholds. CONCLUSION: This study used a computerized psychophysical test designed to minimize many of the test errors associated with earlier studies. It provides confirmatory evidence that MS may be associated with a loss of orientational CS and color vision, in the absence of reduced VA.

Adult↗
PubMed2004

The influence of path length and matrix components on ageing characteristics of transport between the choroid and the outer retina.

PURPOSE: To determine the relative influence of path length and matrix components on the movement of small solutes and water between the choroid and the outer retina. METHODS: Human and bovine Bruch's membrane-choroid (BC) tissue samples were mounted in modified Ussing chambers, and the diffusion of taurine and hydraulic conductivity (Lp) was determined. In humans, diffusion of taurine was determined as a function of age of the donor. The relative contribution of Bruch's membrane in the BC complex to transport processes was measured after its removal by laser ablation. Similarly, the effect of choroidal path length was determined. In humans, tracking the trend of age-related thinning provided samples of various path lengths. In young bovine animals (< or =2 years old), choroidal thickness was adjusted by laser ablation. RESULTS: Diffusion of taurine across human BC decreased linearly from 162.7 to 105.9 nanomoles/h per 3 mm between 10 and 90 years of age (P < 0.05). Ablation of Bruch's membrane increased diffusion of taurine from 129 to 287.9 nanomoles/h per 4 mm in human (donor age 55, 74, and 82 years; P < 0.005) but caused no statistically significant change in bovine BC. Diffusion of taurine across bovine BC was greater in samples with partially ablated choroid (218 nanomoles/h per 4 mm) than in normal control samples (128.75 nanomoles/h per 4 mm). Lp was not measurable in bovine samples after complete ablation of Bruch's membrane, but did not change significantly as the choroid thinned. CONCLUSIONS: The data suggest that both path length and matrix components contribute to the decline of diffusion of small solutes across BC with age. The importance of matrix components was also demonstrated in restricting the movement of water while choroidal thickness played little if any role.

Adolescent↗
PubMed2004

Fluorophore-assisted retinal break detection using antibodies to glial fibrillary acidic protein.

PURPOSE: To evaluate the role of fluorescent antibodies as a means of enhancing the detection of retinal breaks during vitrectomy for rhegmatogenous retinal detachment. METHODS: In ex vivo studies, unfixed, porcine retinal flatmounts were incubated with Cy3 anti-GFAP. Experiments were repeated in the presence of excess soluble GFAP and after surface excimer laser ablation through the internal limiting membrane, into the Müller cell foot processes. Tissue was also incubated with trypan blue, and cross-species immunoreactivity was determined in bovine, rabbit, and human retina. In vivo studies were conducted in a porcine model of rhegmatogenous retinal detachment. Cy3 anti-GFAP was injected into the vitreous cavity of eyes with retinal breaks and then rinsed from the eye. Barrier filters were fitted to the operating microscope to allow intraoperative visualization of tissue stained with Cy3. Excitation endoillumination was provided by a 532-nm diode-pumped laser. RESULTS: In ex vivo studies, retinal flatmounts exposed to Cy3 anti-GFAP showed minimal surface fluorescence, but exposed glial elements at the cut edge of the flatmount stained brightly, as did those exposed by excimer ablation of the Müller cell membrane. Blocking studies confirmed that binding was antigen specific. Trypan blue colocalized to the cut edge of retinal flatmounts. All species showed high levels of immunoreactivity except rabbit. In vivo studies demonstrated selective intraoperative staining of retinal breaks with a high level of specificity. CONCLUSIONS: Intraoperative vital staining of retinal breaks is possible in an animal model of retinal detachment. Ex vivo studies indicate that this occurs because the Cy3 anti-GFAP selectively binds the intermediate filaments of glial cells with damaged or destroyed cell membranes.

Aged↗
PubMed2004

Safety testing of indocyanine green and trypan blue using retinal pigment epithelium and glial cell cultures.

PURPOSE: Indocyanine green (ICG) and trypan blue have been advocated as vital stains for use during macular surgery. The safety of these agents was tested using a cell culture model. METHODS: Human retinal pigment epithelium (RPE) and Müller cell lines were exposed to ICG over a range of concentrations up to 0.5%, and trypan blue up to 0.2%. Cells were exposed to each dye for 5, 15, or 30 minutes, rinsed, and incubated 24 hours. Cell viability was measured using a mitochondrial dehydrogenase-assay and fluorescent live-dead probe. Experiments were repeated using 0.5% and 1% ICG and 0.06% and 0.12% trypan blue, with follow-up at 0, 1, 5, and 15 days. ICG experiments were repeated in the presence of illumination from a xenon light-source channeled through a surgical endolight, and using reduced osmolarity solutions of 0.1%, 0.5%, and 1% (185 vs. 275 mOsM). RESULTS: There was no clear relationship between cell viability and the concentration of the agent or duration of follow-up, except in RPE cells exposed to 1% ICG. These showed a linear (R(2) 0.9952) decline in viability with time, with a significant reduction by day 15 (P = 0.016). RPE cells exposed to ICG and illumination were not significantly different from the negative control, but when illumination was combined with low osmolarity, viability was reduced (P = 0.0016). ICG and illumination reduced Müller cell viability (P < 0.0001 for both 185 and 275 mOsM). Müller cells incubated with 185 mOsM 1% ICG showed a significant reduction in viability (P < 0.0001) not seen with the 185 mOsM 0.5% or 0.1% solutions or in the low-osmolarity RPE groups. CONCLUSIONS: The combination of exposure to 0.5% ICG and the newer endoillumination light-sources can damage cultured Müller cells. Although the preparations of ICG most commonly used clinically did not produce significant damage, relatively small changes in ICG osmolarity and concentration did. This suggests that safety margins are not large. Trypan blue is safe in a cell culture model.

Cell Line↗
PubMed2004

Safety testing of infracyanine green using retinal pigment epithelium and glial cell cultures.

PURPOSE: To undertake safety testing of infracyanine green (IFCG) in a cell culture model. METHODS: Experiments were undertaken in a cell culture model used previously to perform safety testing of indocyanine green (ICG). Human retinal pigment epithelium (RPE) and Müller cells were exposed to IFCG for 5 minutes, over a range of concentrations up to 0.5%. Experiments were repeated, using double-staining with trypan blue. Cell viability was measured at days 1, 5, and 15 using a mitochondrial dehydrogenase assay and a fluorescent live-dead probe containing calcein and ethidium homodimer-1. Viability was measured after exposure to 0.5% IFCG and 5 minutes of illumination with a vitrectomy endolight powered by a xenon light source. RESULTS: RPE viability was not reduced over the range of concentrations and follow-up intervals. RPE cells exposed to IFCG and illumination had reduced viability relative to the negative control (cells exposed to saline), but not relative to those exposed to saline and illumination. Glial cells showed reduced viability at days 1 and 5, but not day 15. Illumination did not further reduce viability. CONCLUSIONS: IFCG has been advocated as a safer macular vital stain than ICG. These results suggest that it is less likely to produce phototoxicity, but despite being nearly iso-osmolar, IFCG also produces damage in cultured glial cells.

Cell Culture Techniques↗
PubMed2004

Compartmental analysis of taurine transport to the outer retina in the bovine eye.

PURPOSE: To assess the relative resistance presented individually by Bruch's membrane-choroid (BC) and the retinal pigment epithelium (RPE) to movement of taurine between the choroidal circulation and the outer retina. To quantify the effect of light-evoked changes in subretinal potassium concentration on the transepithelial transport of taurine across bovine RPE. METHODS: Transport studies were performed in Ussing chambers with intact and RPE-denuded specimens of BC. RPE viability was monitored by recording transepithelial potential (TEP) and transepithelial resistance (TER). Taurine transport with substrate concentrations in the micro- and millimolar range, reflecting physiological taurine concentrations in plasma, retina, and subretinal space was quantified by high-performance liquid chromatography (HPLC) and radiotracer techniques. Taurine transport was also assessed after apical potassium concentration was lowered from 6.0 to 2.2 mM to mimic the effects of light. RESULTS: Transport of taurine across RPE-BC at a 10-mM substrate concentration increased from 32.92 before to 111.72 nanomoles/4 mm per hour after removal of the RPE. Similarly, at 50 microM taurine, transport rates increased from 0.158 to 0.439 nanomoles/4 mm per hour after removal of the RPE. At both high (10 mM) and low (50 microM) substrate concentrations, lowering of apical potassium was associated with decreased transport of taurine across the RPE. For taurine concentrations greater than 42 microM, the rate-limiting compartment for transport of taurine to the outer retina was the RPE monolayer. Similar rates were observed across each compartment for concentrations <42 microM. CONCLUSIONS: The magnitude and directionality of taurine transport across the RPE is determined solely by the driving taurine concentration gradient and is modulated by subretinal levels of potassium. Such modulation may provide a mechanism for conserving retinal taurine. Processes that increase the resistance to diffusion across Bruch's membrane such as human ageing and increased thickening and deposition of debris associated with age-related macular degeneration (AMD) are likely to affect transport across the RPE, culminating in a secondary retinal taurine deficiency.

Animals↗
PubMed2004

Taurine uptake by human retinal pigment epithelium: implications for the transport of small solutes between the choroid and the outer retina.

PURPOSE: To characterize the Michaelis-Menten kinetics of the taurine transporter (TT) in retinal pigment epithelium (RPE) freshly isolated from human donor eyes. To identify the rate limiting compartment in the pathway of taurine delivery from the choroidal blood supply to the outer retina composed by Bruch's-choroid (BC) and the RPE in the human older age group. METHODS: In human donor samples (4 melanoma-affected eyes, and 14 control eyes; age range, 62-93 years), radiochemical techniques were used to determine the RPE taurine accumulation at various exogenous concentrations. The transport capability of human RPE was obtained from a kinetic analysis of the high-affinity carrier over a substrate concentration of 1 to 60 microM taurine. RESULTS: Uptake of taurine into human RPE at a taurine concentration of 1 microM was independent of donor age (P > 0.05) and averaged at 2.83 +/- 0.27 (SEM) pmol/10 minutes per 6-mm trephine. Taurine transport by human RPE was mediated by a high-affinity carrier of K(m) 50 microM and V(max) of 267 pmol/10 minutes per 5-mm disc. CONCLUSIONS: In human donor RPE, uptake of taurine remained viable in the age range 62 to 93 years. Taurine transport rates in the RPE were lower than across the isolated BC complex, and thus the data suggest that the former compartment houses the rate-limiting step in the delivery of taurine to the outer retina.

Aged↗
PubMed2003

Monocular chromatic contrast threshold and achromatic contrast sensitivity in children born prematurely.

PURPOSE: To study the effect of prematurity on monocular chromatic contrast thresholds (CCT) and achromatic contrast sensitivity (ACS). DESIGN: Case-control study. METHODS: A prospective study of 59 children born at less than 33 weeks' gestation was undertaken. Subjects were identified during routine neonatal screening for retinopathy of prematurity and recalled for testing at age 7 to 13 years. Five had stage 1 retinopathy of prematurity, seven had stage 2, and three had stage 3. Sixty-eight full-term children were recruited as controls. Those with major cerebral or eye disease were excluded. The CCT and ACS were measured monocularly in the eye with better visual acuity using static, computer-generated, sinusoidal gratings, displayed on a high-resolution monitor. The CCT and ACS were determined using a randomized double-staircase reversal algorithm. The ACS was measured at five spatial frequencies (0.22, 0.44, 0.88, 1.75, and 3.50 cycles/degree), and the CCT was measured along red-green and tritan confusion axes. RESULTS: Red-green (P =.326) and tritan (P =.910) contrast thresholds and ACS (P >.394 for all spatial frequencies) were similar to the control group. CONCLUSIONS: Previous research suggests that prematurity adversely affects color vision and ACS. This study used a computerized psychophysical test that minimized the test errors inherent in many previous studies. Unexpectedly, CCT and ACS were found to be similar to full-term children.

Adolescent↗
PubMed2003

Human retinal molecular weight exclusion limit and estimate of species variation.

PURPOSE: To determine the maximum size of molecule capable of freely diffusing across human retina, referred to as the retinal exclusion limit (REL), and the location of any sites of high resistance to diffusion. To assess the degree of interspecies variation in the REL of three animals commonly used to model human disease. METHODS: Trephines of human neuroretina were mounted in a modified Ussing chamber. FITC-dextrans of various molecular weights (MWT) were dissolved in phosphate-buffered saline, and the rate of transretinal diffusion was determined over 24 hours with a spectrophotometer. The theoretical REL was calculated by extrapolating the linear relationship between the rate of diffusion and log(MWT). In separate experiments to determine the sites of barrier to diffusion, FITC-dextrans with a MWT greater than the calculated REL were applied to either the inner or outer retinal surface, processed as frozen sections, and viewed with a fluorescence microscope. Experiments to determine the REL were repeated in bovine, porcine, and rabbit retina. RESULTS: The REL in human tissue was 76.5+/-1.5 kDa (6.11+/-0.04 nm). The inner and outer plexiform layers formed the sites of highest resistance to diffusion. The REL in pigs, cattle, and rabbits were 60 +/- 11.5, 78.5 +/- 20.5, and 86 +/- 30 kDa, respectively (5.68 +/- 0.45, 6.18 +/- 0.61, and 6.38 +/- 0.88 nm). CONCLUSIONS: In humans, the inner and outer plexiform layers are sites of high resistance to the diffusion of large molecules, resulting in an REL of 76.5 kDa. There was only moderate interspecies variation in the REL of the animals studied, suggesting that they provide adequate models for the study of human transretinal macromolecular diffusion.

Aged↗
PubMed2003

An experimental model of rhegmatogenous retinal detachment: surgical results and glial cell response.

PURPOSE: To modify existing experimental models to simulate the typical clinical presentation of human rhegmatogenous retinal detachment (RRD), namely an RD caused by a retinal break, in a phakic eye, with a posterior vitreous detachment (PVD); to model RRD in a species that is anatomically similar to humans; and to characterize the glial cell response to RRD. METHODS: Mixed-breed pigs underwent vitrectomy, PVD, subretinal injection of viscoelastic, and creation of a break at the apex of the RD. The crystalline lens was not removed. Follow-up was for 0, 1, and 7 days. Tissue was processed for light and electron microscopy. The glial cell response was characterized using antibodies to glial fibrillary acidic protein (GFAP). RESULTS: Of 11 RRDs created in seven pigs, 10 increased in size and 1 decreased. Light and electron microscopy demonstrated typical features of RD. There was constitutive expression of GFAP in astrocytes and Müller cells with increased immunoreactivity from day 1. CONCLUSIONS: This study provided a model of RRD that simulates the typical clinical presentation in humans. It used techniques that most vitreoretinal surgeons are familiar with, and an animal that is widely available and anatomically similar to humans. Anatomic success was high, and the glial cell response established comparability with other species.

Animals↗