Central retinal vascular trunk deviation in unilateral normal-tension glaucoma.

PURPOSE: To investigate whether the position of the central retinal vascular trunk (CRVT), as a surrogate of lamina cribrosa (LC) offset, was associated with the presence of glaucoma in normal-tension glaucoma (NTG) patients. METHODS: The position of the CRVT was measured as the deviation from the center of the Bruch's membrane opening (BMO), as delineated by spectral-domain optical coherence tomography imaging. The offset index was calculated as the distance of the CRVT from the BMO center relative to that of the BMO margin. The angular deviation of CRVT was measured with the horizontal nasal midline as 0° and the superior location as a positive value. The offset index and angular deviation were compared between glaucoma and fellow control eyes within individuals. RESULTS: NTG eyes had higher baseline intraocular pressure (P = 0.001), a larger ß-zone parapapillary atrophy area (P = 0.013), and a larger offset index (P<0.001). In a generalized linear mixed-effects model, larger offset index was the only risk factor of NTG diagnosis (OR = 31.625, P<0.001). A generalized estimating equation regression model revealed that the offset index was larger in the NTG eyes than in the control eyes for all ranges of axial length, while it was the smallest for the axial length of 23.4 mm (all P<0.001). CONCLUSIONS: The offset index was larger in the unilateral NTG eyes, which fact is suggestive of the potential role of LC/BMO offset as a loco-regional susceptibility factor.

Biomechanical Properties of Bruch's Membrane-Choroid Complex and Their Influence on Optic Nerve Head Biomechanics.

Purpose: The purpose of this study was to measure the rupture pressure and the biomechanical properties of porcine Bruch's membrane (BM)-choroid complex (BMCC) and the influences of BM on optic nerve head (ONH) tissues. Methods: The biomechanical properties of BMCC were extracted through uniaxial tensile tests of 10 BMCC specimens from 10 porcine eyes; the rupture pressures of BMCC were measured through burst tests of 20 porcine eyes; and the influence of BM on IOP-induced ONH deformations were investigated using finite element (FE) analysis. Results: Uniaxial experimental results showed that the average elastic (tangent) moduli of BMCC samples at 0% and 5% strain were 1.60 ± 0.81 and 2.44 ± 1.02 MPa, respectively. Burst tests showed that, on average, BMCC could sustain an IOP of 82 mm Hg before rupture. FE simulation results predicted that, under elevated IOP, prelamina tissue strains increased with increasing BM stiffness. On the contrary, lamina cribrosa strains showed an opposite trend but the effects were small. Conclusions: BMCC stiffness is comparable or higher than those of other ocular tissues and can sustain a relatively high pressure before rupture. Additionally, BM may have a nonnegligible influence on IOP-induced ONH deformations.

Biomechanical properties of native basement membranes.

Basement membranes are sheets of extracellular matrix that separate epithelia from connective tissues and outline muscle fibers and the endothelial lining of blood vessels. A major function of basement membranes is to establish and maintain stable tissue borders, exemplified by frequent vascular breaks and a disrupted pial and retinal surface in mice with mutations or deletions of basement membrane proteins. To directly measure the biomechanical properties of basement membranes, chick and mouse inner limiting membranes were examined by atomic force microscopy. The inner limiting membrane is located at the retinal-vitreal junction and its weakening due to basement membrane protein mutations leads to inner limiting membrane rupture and the invasion of retinal cells into the vitreous. Transmission electron microscopy and western blotting has shown that the inner limiting membrane has an ultrastructure and a protein composition typical for most other basement membranes and, thus, provides a suitable model for determining their biophysical properties. Atomic force microscopy measurements of native chick basement membranes revealed an increase in thickness from 137 nm at embryonic day 4 to 402 nm at embryonic day 9, several times thicker that previously determined by transmission electron microscopy. The change in basement membrane thickness was accompanied by a large increase in apparent Young's modulus from 0.95 MPa to 3.30 MPa. The apparent Young's modulus of the neonatal and adult mouse retinal basement membranes was in a similar range, with 3.81 MPa versus 4.07 MPa, respectively. These results revealed that native basement membranes are much thicker than previously determined. Their high mechanical strength explains why basement membranes are essential in stabilizing blood vessels, muscle fibers and the pial border of the central nervous system.

Photoreceptor Layer Thickness Changes During Dark Adaptation Observed With Ultrahigh-Resolution Optical Coherence Tomography.

Purpose: To examine outer retinal band changes after flash stimulus and subsequent dark adaptation with ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods: Five dark-adapted left eyes of five normal subjects were imaged with 3-µm axial-resolution UHR-OCT during 30 minutes of dark adaptation following 96%, 54%, 23%, and 0% full-field and 54% half-field rhodopsin bleach. We identified the ellipsoid zone inner segment/outer segment (EZ[IS/OS]), cone interdigitation zone (CIZ), rod interdigitation zone (RIZ), retinal pigment epithelium (RPE), and Bruch's membrane (BM) axial positions and generated two-dimensional thickness maps of the EZ(IS/OS) to the four bands. The average thickness over an area of the thickness map was compared against that of the dark-adapted baselines. The time-dependent thickness changes (photoresponses) were statistically compared against 0% bleach. Dark adaptometry was performed with the same bleaching protocol. Results: The EZ(IS/OS)-CIZ photoresponse was significantly different at 96% (P < 0.0001) and 54% (P = 0.006) bleach. At all three bleaching levels, the EZ(IS/OS)-RIZ, -RPE, and -BM responses were significantly different (P < 0.0001). The EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ time courses were similar to the recovery of rod- and cone-mediated sensitivity, respectively, measured with dark adaptometry. The maximal EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ response magnitudes doubled from 54% to 96% bleach. Both EZ(IS/OS)-RPE and EZ(IS/OS)-BM responses resembled dampened oscillations that were graded in amplitude and duration with bleaching intensity. Half-field photoresponses were localized to the stimulated retina. Conclusions: With noninvasive, near-infrared UHR-OCT, we characterized three distinct, spatially localized photoresponses in the outer retinal bands. These photoresponses have potential value as physical correlates of photoreceptor function.

An experimental study of the elastic properties of the human Bruch's membrane-choroid complex: relevance to ageing.

AIM: To investigate the mechanical properties (stress-strain relation, elasticity, hysteresis, response to stress spikes and drops) of isolated human Bruch's membrane-choroid, as well as the effect of ageing and aged related macular degeneration (AMD). METHODS: 13 Bruch's membrane-choroid complexes were obtained from human donors (21-97 years). Two samples (aged 85 and 95) showed signs of AMD including large, soft drusen, choroidal neovascularisation, and/or disciform scars. Various hydrostatic pressures (stress) were applied to the choroidal surface of mid-peripheral samples mounted in a modified open Ussing chamber. Linear scans of the tissue were recorded by optical coherence tomography (OCT) and the pressure induced deformation (strain), elasticity, hysteresis, and response to pressure spikes and drops measured. RESULTS: The elasticity of human Bruch's membrane-choroid complex decreased linearly with ageing (p<0.001) after the age of 21 with an approximate reduction of 1% per year. The decrease was not exaggerated in AMD. The recoil capacity of Bruch's membrane-choroid was not affected by ageing. The response to pressure spikes/drops was similar in age matched normal and AMD eyes. The results suggest that although the aged induced decrease in Bruch's membrane elasticity may contribute to breaks in this membrane in AMD leading to neovascularisation this is not sufficient. The presence of other factors is required for its development. CONCLUSION: The elasticity of Bruch's membrane-choroid complex decreases with age while recoil capacity does not. The decrease was not exaggerated in AMD.

Retinal Biochemistry, Physiology and Cell Biology.

The vitreous, the vasculature of the retina, macular pigments, phototransduction, retinal pigment epithelium, Bruch's membrane and the extracellular matrix, all play an important role in the normal function of the retina as well as in diseases. Understanding the pathophysiology allows us to target treatment. As ocular angiogenesis, immunity and inflammation are covered elsewhere, those subjects will not be discussed in this chapter.

Albumen Transport to Bruch's Membrane and RPE by Choriocapillaris Caveolae.

PURPOSE: The choriocapillaris (CC), the capillary network of the choroid, is positioned adjacent to Bruch's membrane (BM) and the RPE. The aim of this study was to clarify the mechanism(s) for transport of serum albumen from CC lumen to RPE. METHODS: Alexa647 conjugated to BSA (BSA-A647) or PBS was administrated via the femoral vein to young and aged wild-type (WT; C57BL/6J) mice and Caveolin-1 knockout mice (Cav1(-/-)). Mice were perfused with PBS and killed at 30 minutes, 1 hour, and 4 hours after injection. Eyecups were cryopreserved, and cryosections were analyzed on a Zeiss 710 confocal microscope. Bovine serum albumin conjugated to gold nanoparticles (BSA-GNP) was administrated through the left common carotid artery. Mice were perfused with PBS and killed at 30 minutes after injection. Eyecups were embedded after fixation, and 70-nm-thick sections were analyzed on a Hitachi H7600 transmission electron microscope. RESULTS: In eyes of WT young mice, BSA-A647 was transported to the RPE at 30 minutes and diffused to the photoreceptor layer by 1 hour. In contrast, most BSA-A647 was found in the CC in Cav1(-/-) eyes. The majority of BSA-GNP found in the CC of young WT mice was on the luminal side in caveolae at 30 minutes after injection. In aged WT mice, BSA-GNPs were found in defective tight junctions between endothelial cells and appeared trapped at the diaphragm of fenestrations. CONCLUSIONS: Normally, CC carefully regulates transport system of BSA from lumen to BM by caveolae-mediated transcytosis; however, endothelium cells of aged control WT mice have leaky tight junctions and lacked regulated BSA transport.

In Vivo Choroidal Vascular Lesions in Diabetes on Swept-Source Optical Coherence Tomography.

Diabetes induces microvascular diseases including diabetic retinopathy and choroidopathy which reciprocally promote the pathogenesis, although optical coherence tomography images of diabetic choroidopathy remains to be documented. Here we evaluated the qualitative characteristics of choroidal vascular lesions in patients with diabetes and their association with diabetic retinopathy on swept-source optical coherence tomography (SS-OCT) images. We retrospectively reviewed 110 consecutive eyes of 110 patients with diabetes and 35 eyes of 35 healthy subjects for whom SS-OCT images (6x6-mm scans centered on the fovea) of sufficient quality were acquired. The curve of chorioretinal sections was flattened using Bruch's membrane as a reference surface, followed by generation of en-face images. We characterized choroidal vascular lesions and evaluated their association with the logarithm of the minimum angle of resolution visual acuity (logMAR VA), retinal and choroidal thicknesses, and diabetic retinopathy severity. En-face SS-OCT images showed unvisualized vessels in Sattler's layer in 33 eyes (30.0%). Focal narrowing was seen in choroidal vessels in Haller's layer in 56 eyes (50.9%). The choroidal vessels ended in the superficial or middle portion of Haller's layer, referred to as vascular stumps, in 20 eyes (18.2%). Diabetic eyes had these findings more frequently than nondiabetic eyes. The subfoveal choroid was thicker in eyes with focal vascular narrowing and vascular stumps than in eyes without such lesions. Vascular stumps in Haller's layer were significantly related to diabetic retinopathy severity, logMAR VA, and central retinal and choroidal thicknesses. These novel findings on SS-OCT images would promote the better understanding of complicated pathogenesis in diabetic retinopathy and choroidopathy.

Changes in Bruch's membrane and related structures with age.

Age-related macular disease is a major and growing public health burden in developed Caucasian societies, accounting for about 50% of blind registration. Evidence exists that this is an emerging problem in Eastern Asia, although the phenotype appears to differ from that seen in Western society. It is likely that several genes are involved, and that the genes or allelic variants conferring are common. Environment plays a major role in its pathogenesis, and it is believed that genetic susceptibility becomes apparent only if there are sufficient environmental pressures. There is no therapy currently available that will have an impact on the prevalence of blindness from age-related macular disease. It has been shown that visual loss occurs as a reaction to ageing changes in Bruch's membrane, which is interposed between the choriocapillaris and the retinal pigment epithelium. The age changes in all three structures have been partly characterised, and as a consequence, multiple putative pathogenic mechanisms have been proposed. Cross-sectional studies of populations with different genetic background and life styles would serve to prove the importance of inheritance and environment. Molecular genetic analysis of blood from affected sibling pairs from these sources may indicate the relevant genes, the prevalence of which may differ in different communities. Enquiries as to life styles may determine important environmental influences. Examination of donor eyes from these communities may reveal distinctive features that may reflect the variation in genetic predisposition and environmental pressures. It is hoped that the findings from such studies will lead to novel and potentially successful management strategies.

Influence of translaminar pressure dynamics on the position of the anterior lamina cribrosa surface.

PURPOSE: To determine how the translaminar pressure difference (TLPD) and gradient (TLPG) influence the position of anterior lamina cribrosa (LC) surface. METHODS: Twenty-six eyes of 26 healthy subjects were subjected to enhanced-depth imaging volume scanning of the optic nerve using spectral-domain optical coherence tomography (SD-OCT). The anterior LC surface depth (LCD) relative to the Bruch's membrane (BM) opening was measured at 11 equidistant planes, and the LC thickness (LCT) was measured at three locations (superior midperipheral, midhorizontal, and inferior midperipheral). Intraocular pressure and lumbar cerebrospinal fluid pressure (CSFP) were measured on the same day as the SD-OCT examination. The TLPD was defined as the difference between IOP and CSFP (i.e., IOP-CSFP), and the TLPG as the TLPD divided by LCT (i.e., TLPD/LCT). RESULTS: Subjects were aged 63.4 ± 8.0 years and comprised 12 males and 14 females. Regression analyses revealed a significant association between a larger mean LCD and male sex (P = 0.002), and between a larger central LCD and male sex (P ≤ 0.012), larger TLPD (P = 0.048), and higher TLPG (P = 0.029). There was no significant association between IOP, CSFP, and LCT, and either the mean LCD (P = 0.438, 0.368, and 0.416, respectively) or central LCD (P = 0.284, 0.085, and 0.144, respectively). CONCLUSIONS: A larger central LCD was associated with larger TLPD and higher TLPG in healthy eyes, which indicates that the translaminar pressure dynamics may play a role in the position of the anterior LC surface relative to BM opening in healthy human eyes.

The relationships of age changes in retinal pigment epithelium and Bruch's membrane.

PURPOSE: To study the correlations between age, Bruch's membrane (BM) thickness, retinal pigment epithelial (RPE) autofluorescence, and RPE residual body content. METHODS: Eight-millimeter-diameter macular discs from 88 unpaired human eye bank eyes were obtained within 72 hours of death, fixed in 10% neutral buffered formalin, and hemisected horizontally. One portion of the macular disc was embedded in paraffin and stained with periodic acid-Schiff for the measurement of BM thickness. RPE autofluorescence measurements were performed on unstained, deparaffinized sections. A second portion of the macular disc was prepared for electron microscopy to evaluate RPE residual body content. Linear and polynomial regression techniques were used to investigate the correlations between age, BM thickness, RPE autofluorescence, and RPE residual body content. RESULTS: Bruch's membrane thickness increased with age according to the linear model. RPE autofluorescence and RPE residual body content also increased with age, but the correlations were best approximated by a quadratic model. The correlations between RPE autofluorescence and residual body content and between BM thickness and RPE autofluorescence were best approximated by a linear regression model. There was considerable variation in these correlations between specimens and within the same age group. CONCLUSIONS: Although the changes in RPE and Bruch's membrane increased with age and there was a direct correlation between changes in the two tissues, there was considerable variation within each age group and between specimens. This probably reflects the multifactorial nature of the process.

Fate of human retinal pigment epithelial cells seeded onto layers of human Bruch's membrane.

PURPOSE: To determine the fate of human retinal pigment epithelial (RPE) cells seeded onto different layers of human Bruch's membrane (BM). METHODS: Bruch's membrane explants were prepared from 16 human cadaver eyes (7 eyes age <50 years; 9 eyes >50 years) by removing native RPE cells with ammonium hydroxide to expose the RPE cell basal lamina (BL). The inner collagenous layer (ICL) and elastin layer (EL) were exposed by removing apical layers sequentially by mechanical and enzymatic means. Synchronized first passage human RPE cells (15,000 cells/(6-mm-diameter explant) were plated onto each layer of human BM. The RPE cell reattachment and apoptosis rates at 24 hours, proliferation rates and mitotic index 24 hours after growth stimulation, and the ability of RPE cells to repopulate the explant surface were determined on each layer. RESULTS: RPE cell reattachment was highest on BL but decreased on deeper layers of BM. The apoptosis rate of attached cells increased as deeper layers of BM were exposed. The proliferation rate and mitotic index of the grafted cells were higher on BL than on deeper layers. RPE cells plated onto BL repopulated the explant surface within 14 +/- 3 days, whereas cells plated onto the ICL and EL eventually died and never reached confluence. CONCLUSIONS: The fate of RPE cells seeded onto BM depends on the ultrastructural layer of BM available for reattachment. These findings suggest that the ability of transplanted RPE cells to repopulate bare BM will depend on the layer of BM available for RPE cell reattachment.

Retinal pigment epithelium wound healing in human Bruch's membrane explants.

PURPOSE: To compare retinal pigment epithelium (RPE) resurfacing on the RPE basement membrane and inner collagenous layer (ICL) in human submacular Bruch's membrane explants. METHODS: Debridements were created in RPE-choroid-sclera explants (mean donor age 71.91 +/- 7.76 years) to create defects exposing the RPE basement membrane (RPEbm(+) defects), the ICL immediately below the RPE basement membrane (superficial ICL, [SICL]) or deeper layers of the ICL (DICL). Eleven pairs of eyes--four pairs with one eye having an RPEbm(+) defect and the fellow eye having an SICL defect and seven pairs with corresponding RPEbm(+) and DICL defects--were observed for 10 days by visualizing RPE ingrowth with 4',6'-diamino-2-phenylindole (DAPI) filters. At day 10, specimens were processed for scanning electron microscopy. RESULTS: Resurfacing of localized RPE defects occurred to some degree in all 11 pairs of eyes. No significant difference in the percentage of resurfacing of RPEbm(+) defects (67.35% +/- 18.82%) and SICL defects (64.26% +/- 16.07%) was observed although healing of the SICL showed more variability in the morphology of RPE cells migrating into the defect. Significant differences in healing were observed between pairs with RPEbm(+) defects versus DICL defects (84.07% +/- 15.35% and 54.00% +/- 14.54% resurfacing, respectively). RPE ingrowth into DICL defects exhibited the greatest morphologic variability. CONCLUSIONS: RPE basement membrane supports RPE resurfacing of localized RPE defects. The deeper portion of the ICL of aged submacular human Bruch's membrane does not support RPE resurfacing to the same extent as does the RPE basement membrane. The poor RPE resurfacing observed in DICL defects mimics the histopathological findings in patients with age-related macular degeneration after excision of choroidal new vessels.

Iris pigment epithelium attachment to aged submacular human Bruch's membrane.

PURPOSE: To determine whether iris pigment epithelium (IPE) cells can attach to aged submacular human Bruch's membrane and to assess whether IPE cells express the integrin subunits that may be necessary to bind to the known extracellular matrix ligands present in Bruch's membrane. METHODS: IPE cells were seeded onto the RPE basement membrane (RPEbm) or inner collagenous layer (ICL) of aged submacular Bruch's membrane as microaggregates or were expanded in culture until enough cells could be obtained for seeding. Cell morphology and the percentage of cell coverage were determined 1 or 7 days after seeding. Messenger RNA was extracted from cultured and uncultured IPE cells and analyzed by RT-PCR. The expression of integrin subunits alpha1 to alpha6 and beta1 mRNA was examined. RESULTS: Coverage by uncultured IPE was low on both surfaces at day-1 (RPEbm, 7.9% +/- 4.8%; ICL, 5.0% +/- 2.5%) with few intact cells present. Culturing IPE improved attachment with similar coverage on both surfaces and no significant difference between day-1 (RPEbm, 89.9% +/- 9.1%; ICL, 63.4% +/- 26.5%) and day-7 (RPEbm, 97.8% +/- 2.3%; ICL, 94.7% +/- 6.6%). By day-7, cell morphology and coverage on both surfaces was variable, ranging from few intact cells to a high degree of coverage by flattened cells. All integrin subunits studied were expressed in cultured cells, whereas alpha2, alpha3, and alpha4 showed less or no expression in uncultured cells. CONCLUSIONS: Upregulation of integrin mRNA expression may be one explanation for the difference in coverage by cultured versus uncultured IPE cells. The presence of dead, dying, or flattened cells at day 7 indicates that IPE may not survive or differentiate on aged submacular Bruch's membrane.

Reattachment of cultured human retinal pigment epithelium to extracellular matrix and human Bruch's membrane.

PURPOSE: To determine the mechanism of reattachment of harvested human retinal pigment epithelium (RPE) to RPE-derived extracellular matrix and Bruch's membrane. METHODS: Confluent first-to third-passage human RPE were harvested from tissue culture and plated onto RPE-derived extracellular matrix or human Bruch's membrane exoplants denuded of cells by treatment with 0.02 N ammonium hydroxide. The authors measured RPE reattachment to uncoated surfaces or surfaces precoated with extracellular matrix proteins (fibronectin, laminin, vitronectin, or type IV collagen), antibodies to extracellular matrix-proteins, or the synthetic peptide RGDS (arginine-glycine-aspartate-serine). Some RPE were pretreated with anti-beta 1 integrin antibodies before plating onto either substrate. RESULTS: Coating the surface of either RPE-derived extracellular matrix or Bruch's membrane with fibronectin, laminin, vitronectin, or type IV collagen increased the RPE attachment rate. Exposing RPE to anti-beta 1 integrin antibodies or RGDS or precoating the surface with antibodies to fibronectin, laminin, vitronectin, or type IV collagen decreased the RPE attachment rate to both surfaces. The RPE attachment rate to Bruch's membrane was lower when the exoplants were harvested from the macula of older (age, 70 to 90 years) versus younger (age, 30 to 40 years) persons (52.4 +/- 3.6% versus 64.3 +/- 3.5%, respectively; P < 0.05). CONCLUSIONS: The attachment of cultured human RPE cells to human Bruch's membrane or to RPE-derived extracellular matrix is mediated by an interaction between the beta 1-subunit of integrin on the RPE surface and ligands in the extracellular matrix that include laminin, fibronectin, vitronectin, and type IV collagen. The lower rate of RPE reattachment to the macula from older human cadaveric eyes may have implications for studies aimed at RPE transplantation in elderly persons.

Reengineering of aged Bruch's membrane to enhance retinal pigment epithelium repopulation.

PURPOSE: An earlier study showed that age-related changes in the inner collagen layer (ICL) inhibit RPE cell repopulation of human Bruch's membrane. The present study was undertaken to determine the effect of cleaning and/or an extracellular matrix (ECM) protein coating on the reattachment, apoptosis, proliferation, and final surface coverage of the transplanted RPE cells. METHODS: Explants of aged Bruch's membrane with ICL exposed were prepared from five human cadaveric eyes (donor ages, 69-84 years) and treated with Triton X-100 and/or coated with a mixture of laminin (330 microg/mL), fibronectin (250 microg/mL), and vitronectin (33 microg/mL). Viable human fetal and ARPE-19 cells (n = 15,000) were plated onto the surface and the RPE reattachment, apoptosis, and proliferation ratios were determined on the modified surfaces. Cells were cultured up to 17 days to determine the surface coverage. Ultrastructure of the modified Bruch's membrane and RPE morphology were studied with transmission and scanning electron microscopy. RESULTS: Reattachment ratios of fetal human RPE and ARPE-19 cells were similar on aged ICL (41.5% +/- 1.7% and 42.9% +/- 2.7%, P > 0.05). The reattachment ratio increased with ECM protein coating and decreased with detergent treatment. Combined cleaning and coating restored the reattachment ratio of the fetal RPE cells, but failed to increase the reattachment ratio of ARPE-19 cells. The highest apoptosis was observed on untreated ICL. Cleaning and the combined procedure of cleaning and ECM protein coating decreased fetal RPE cell apoptosis. Only RPE cells plated on cleaned or cleaned and ECM-coated ICL demonstrated proliferation that led to substantial surface coverage at day 17. CONCLUSIONS: Age-related changes that impair RPE repopulation of Bruch's membrane can be significantly reversed by combined cleaning and ECM protein coating of the ICL. Development of biologically tolerant techniques for modifying the ICL in vivo may enhance reattachment of the RPE and its repopulation of aged ICL.

Decreasing hydraulic conductivity of Bruch's membrane: relevance to photoreceptor survival and lipofuscinoses.

Deterioration of visual performance leading to blindness is particularly severe in the early-onset forms of Batten disease. Metabolic support of the neural retina is critically dependent on the choroidal blood supply and on efficient transport pathways through Bruch's membrane and the retinal pigment epithelium (RPE). Conversely, degradation products and, in particular, damaged membranous components of photoreceptor outer segments must be removed in the opposite direction. Incomplete breakdown of damaged "spent" discs leads to the age-related accumulation of lipofuscin-like pigments in the RPE, and these in turn influence the degenerative changes in Bruch's membrane. The generalized and extensive deposition of lipofuscin-like material in Batten disease is therefore likely to exacerbate the degenerative changes in Bruch's membrane, and thereby compromise local fluid dynamics. The hydrodynamic properties of Bruch's membrane were examined in normal donor eyes and showed a precipitous decline of hydraulic conductivity during early life. In fact, the maximal capacity for fluid transport was halved for every 17 years of life. This finding is therefore highly relevant to the development of ensuing pathology in the neuronal ceroid-lipofuscinoses.

Retinal pigment epithelial repopulation in monkeys after submacular surgery.

BACKGROUND: Transplantation of retinal pigment epithelium may be a treatment for retinal diseases, such as age-related macular degeneration and hereditary macular degeneration. Before transplantation studies are undertaken, questions concerning repopulation of retinal pigment epithelial cells in situ and photoreceptor repair after submacular surgery need to be addressed. METHODS: We removed the retinal pigment epithelium from Bruch's membrane in the macaque monkey in the macula and outside the vascular arcades. This model allowed the study of in situ retinal pigment epithelium regrowth and photoreceptor repair for 9 months following débridement. RESULTS: Fluorescein angiography revealed a window defect in the area of denuded retinal pigment epithelium. Histologic studies revealed repopulated nonpigmented retinal pigment epithelial cells in the denuded areas in both the early and late periods. At 9 months, the repopulated retinal pigment epithelium was associated with repaired, normal-appearing photoreceptor outer segments. Retinal pigment epithelium regrowth was observed only if Bruch's membrane was intact. CONCLUSIONS: Repopulation of retinal pigment epithelium in the adult primate can occur rapidly and can support the repair of damaged photoreceptors following submacular surgery.

Autologous retinal pigment epithelium and choroid translocation in patients with exudative age-related macular degeneration: short-term follow-up.

PURPOSE: To evaluate the feasibilty of translocating autologous retinal pigment epithelium cells and choroid after the removal of a subfoveal choroidal neovascular membrane in patients with exudative age-related macular degeneration. DESIGN: Interventional case series. METHODS: This was a prospective evaluation of six patients with a follow-up of 7 to 13 months. All patients had large (> 1 disk diameter) subfoveal choroidal membranes, five with subretinal hemorrhage. Preoperative visual acuity ranged from 20/400 to 20/200. After the extraction of the neovascular complex, an autologous peripheral full-thickness patch of retinal pigment epithelium, Bruch membrane, choriocapillary, and choroid was cut out from the midperiphery and repositioned under the macula. Functional tests included Early Treatment Diabetic Retinopathy Study vision testing, fixation testing on a optical coherence tomography monitor, fluorescein and indocyanine green angiography, and scanning laser ophthalmoscopy autofluorescence. RESULTS: The retinal pigment epithelium patch appeared flat and had a brown furry aspect in four patients. Fixation was on the patch in these four patients. Postoperative vision ranged from 20/200 to 20/64, with a 2-line increase in three patients. Revascularization was visible on fluorescein and indocyanide angiography in three patients examined in this manner. Normal retinal pigment epithelium autofluorescence was present over the patch in four patients. CONCLUSIONS: The translocation of a full-thickness patch with autologous peripheral retinal pigment epithelium to the macula after choroidal neovascular membrane extraction was feasible and may result in a surviving and functioning graft for more than 1 year. Longer follow-up to evaluate its long-term benefit is necessary, as well as refinement of the surgery.