Durable 3D murine ex vivo retina glaucoma models for optical coherence tomography.

Durable and standardized phantoms with optical properties similar to native healthy and disease-like biological tissues are essential tools for the development, performance testing, calibration and comparison of label-free high-resolution optical coherence tomography (HR-OCT) systems. Available phantoms are based on artificial materials and reflect thus only partially ocular properties. To address this limitation, we have performed investigations on the establishment of durable tissue phantoms from ex vivo mouse retina for enhanced reproduction of in vivo structure and complexity. In a proof-of-concept study, we explored the establishment of durable 3D models from dissected mouse eyes that reproduce the properties of normal retina structures and tissue with glaucoma-like layer thickness alterations. We explored different sectioning and preparation procedures for embedding normal and N-methyl-D-aspartate (NMDA)-treated mouse retina in transparent gel matrices and epoxy resins, to generate durable three-dimensional tissue models. Sample quality and reproducibility were quantified by thickness determination of the generated layered structures utilizing computer-assisted segmentation of OCT B-scans that were acquired with a commercial HR-OCT system at a central wavelength of 905 nm and analyzed with custom build software. Our results show that the generated 3D models feature thin biological layers close to current OCT resolution limits and glaucoma-like tissue alterations that are suitable for reliable HR-OCT performance characterization. The comparison of data from resin-embedded tissue with native murine retina in gels demonstrates that by utilization of appropriate preparation protocols, highly stable samples with layered structures equivalent to native tissues can be fabricated. The experimental data demonstrate our concept as a promising approach toward the fabrication of durable biological 3D models suitable for high-resolution OCT system performance characterization supporting the development of optimized instruments for ophthalmology applications.

Position of the ISTENT Inject® Trabecular Micro-Bypass System Visualized with the NIDEK GS-1 Gonioscope-A Postoperative Analysis.

Glaucoma is one of the leading causes of irreversible blindness globally and is characterized by the gradual loss of retinal ganglion cells. The primary risk factor for the development and progression of glaucoma is increased intraocular pressure (IOP). Numerous surgical interventions exist to lower IOP should conservative therapy fail. One trend in recent years has been minimally invasive glaucoma surgery (MIGS) as an alternative to traditional methods. The ISTENT inject® is an ab interno trabecular micro-bypass implant designed to be implanted through the trabecular meshwork into the Schlemm's canal to lower IOP. The aim of the study was the postoperative visualization and description of the positioning of the ISTENT inject® using automated circumferential goniophotography. Patients with symptomatic cataracts and mild to moderate primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEX), and pigment-dispersion glaucoma were included who underwent combined cataract surgery with the ISTENT inject® and received postoperative automated gonioscopy with the NIDEK Gonioscope GS-1 to visualize the location of the implant. Twenty-four implants of 14 eyes in 11 patients could be visualized. Out of the implants, 14.3% were in the trabecular meshwork, 46.4% were at the border between the trabecular meshwork and scleral spur, 25% were below the trabecular meshwork, and 14.3% of the implants were not detectable in the gonioscopy. In the overall cohort, a statistically significant IOP reduction was found over the 12-month postoperative observation period. Even in three eyes, in each of which both stents were located below the trabecular meshwork, an IOP reduction over 12 months was observed compared to the baseline IOP. In this study, vertical two-dimensional positioning of the ISTENT inject® was performed for the first time using NIDKE GS-1 automated 360° goniophotography. The method is suitable for postoperative visualization, control, and documentation of positioning after ISTENT inject® implantation. Further studies are needed to analyze the correlation between positioning of the ISTENT inject® in the chamber angle and postoperative IOP reduction.

Sub-Retinal Injection of Human Lipofuscin in the Mouse - A Model of "Dry" Age-Related Macular Degeneration?

Lipofuscin (LF) accumulates during lifetime in the retinal pigment epithelium (RPE) and is thought to play a crucial role in intermediate and late age-related macular degeneration (AMD). In an attemt to simulate aged retina and to study response of retinal microglia and RPE cells to LF, we injected a suspension of LF into the subretinal space of adult mice. LF suspension was obtained from human donor eyes. Subretinal injection of PBS or sham injection served as a control. Eyes were inspected by autofluorescence and optical coherence tomography, by electroretinography and on histological and ultrastructural levels. Levels of cytokine mRNA were determined by quantitative PCR separately in the RPE/choroid complex and in the retina. After injection of LF, microglial cells migrated quickly into the subretinal space to close proximity to RPE cells and phagocytosed LF particles. Retinal function was affected only slightly by LF within the first two weeks. After longer time, RPE cells showed clear signs of melanin loss and degradation. Levels of mRNA of inflammatory cytokines increased sharply after injection of both PBS and LF and were higher in the RPE/choroid complex than in the retina and were slightly higher after LF injection. In conclusion, subretinal injection of LF causes an activation of microglial cells and their migration into subretinal space, enhanced expression of inflammatory cytokines and a gradual degradation of RPE cells. These features are found also in an aging retina, and subretinal injection of LF could be a model for intermediate and late AMD.

Sub-Retinal Injection of Human Lipofuscin in the Mouse - A Model of "Dry" Age-Related Macular Degeneration?

Lipofuscin (LF) accumulates during lifetime in the retinal pigment epithelium (RPE) and is thought to play a crucial role in intermediate and late age-related macular degeneration (AMD). In an attemt to simulate aged retina and to study response of retinal microglia and RPE cells to LF, we injected a suspension of LF into the subretinal space of adult mice. LF suspension was obtained from human donor eyes. Subretinal injection of PBS or sham injection served as a control. Eyes were inspected by autofluorescence and optical coherence tomography, by electroretinography and on histological and ultrastructural levels. Levels of cytokine mRNA were determined by quantitative PCR separately in the RPE/choroid complex and in the retina. After injection of LF, microglial cells migrated quickly into the subretinal space to close proximity to RPE cells and phagocytosed LF particles. Retinal function was affected only slightly by LF within the first two weeks. After longer time, RPE cells showed clear signs of melanin loss and degradation. Levels of mRNA of inflammatory cytokines increased sharply after injection of both PBS and LF and were higher in the RPE/choroid complex than in the retina and were slightly higher after LF injection. In conclusion, subretinal injection of LF causes an activation of microglial cells and their migration into subretinal space, enhanced expression of inflammatory cytokines and a gradual degradation of RPE cells. These features are found also in an aging retina, and subretinal injection of LF could be a model for intermediate and late AMD.

The first reported case of a deletion of the entire RPGR gene in a family with X-linked retinitis pigmentosa.

Clinical phenotypes of a patient with a deletion of the entire RPGR gene have not been described in the literature yet. We hereby report a new mutation in a family of X-linked retinitis pigmentosa (×lRP), showing the deletion of the entire RPGR gene. Gene therapy for inherited retinal diseases holds great promise; however, so far there has been no approved treatment of RPGR-mediated retinitis pigmentosa. The presented evidence of genotype-phenotype correlation may be useful for genetic diagnosis or even genetic treatment in the near future.

Overexpression of Neuregulin-1 Type III Has Impact on Visual Function in Mice.

Schizophrenia is associated with several brain deficits, including abnormalities in visual processes. Neuregulin-1 (Nrg1) is a family of trophic factors containing an epidermal growth factor (EGF)-like domain. It is thought to play a role in neural development and has been linked to neuropsychiatric disorders. Abnormal Nrg1 expression has been observed in schizophrenia in clinical studies. Moreover, in schizophrenia, there is more and more evidence found about pathological changes of the retina regarding structural, neurochemical and physiological parameters. However, mechanisms of these changes are not well known. To investigate this, we analysed the function of the visual system using electroretinography (ERG) and the measurement of visual evoked potentials (VEP) in transgenic mice overexpressing Nrg1 type III of three different ages (12 weeks, 24 weeks and 55 weeks). ERG amplitudes tended to be higher in transgenic mice than in control mice in 12-week old mice, whereas the amplitudes were almost similar in older mice. VEP amplitudes were larger in transgenic mice at all ages, with significant differences at 12 and 55 weeks (p values between 0.003 and 0.036). Latencies in ERG and VEP measurements did not differ considerably between control mice and transgenic mice at any age. Our data show for the first time that overexpression of Nrg1 type III changed visual function in transgenic mice. Overall, this investigation of visual function in transgenic mice may be helpful to understand corresponding changes that occur in schizophrenia, as they may find use as biomarkers for psychiatric disorders as well as a potential tool for diagnosis in psychiatry.

Removal of RPE lipofuscin results in rescue from retinal degeneration in a mouse model of advanced Stargardt disease: Role of reactive oxygen species.

Accumulation of lipofuscin in the retinal pigment epithelium (RPE) is a hallmark of aging and is associated with retinal degeneration encountered in age-related macular degeneration (AMD) and Stargardt disease (SD). Currently, treatment for lipofuscin-induced retinal degeneration is unavailable. Here, we report that Remofuscin (INN: soraprazan, a tetrahydropyridoether small molecule) reverses lipofuscin accumulation in aged primary human RPE cells and is non-cytotoxic in aged SD mouse RPE cells in vitro. In addition, we show that the removal of lipofuscin after a single intravitreal injection of Remofuscin results in a rescue from retinal degeneration in a mouse model of advanced SD which is even accompanied by an amelioration of the retinal dysfunction. Finally, we demonstrate that the mechanism causing lipofuscinolysis may involve the reactive oxygen species generated via the presence of Remofuscin. These data suggest a possible therapeutic approach to untreatable lipofuscin-mediated diseases like AMD, SD and lipofuscinopathies in neurodegenerative diseases.

Enhanced Visualization of Retinal Microvasculature via Deep Learning on OCTA Image Quality.

PURPOSE: To investigate the impact of denoising on the qualitative and quantitative parameters of optical coherence tomography angiography (OCTA) images of the optic nerve and macular area. METHODS: OCTA images of the optic nerve and macular area were obtained using a Canon-HS100 OCT device for 48 participants (48 eyes). Multiple image averaging (MIA) and denoising techniques were used to improve the quality of the OCTA images. The peak signal-to-noise ratio (PSNR) as an image quality parameter and vessel density (VD) as a quantitative parameter were obtained from single-scan, MIA, and denoised OCTA images. The parameters were compared, and the correlation was analyzed between different imaging protocols. RESULTS: In the optic nerve area, there were significant differences in the PSNR and VD in all measured regions between the three groups (P < 0.0001). The PSNR of the denoised group was significantly higher than that of the other two groups (P < 0.0001). The VD in the denoised group was significantly lower than that in the single-scan group in all measured regions (P < 0.0001). In the macular area, there were significant differences in the PSNR and VD in all measured regions among the three groups. The PSNR of the denoised group was significantly higher than that of the other two groups (P < 0.0001). The VD in the denoised group was significantly lower than that in the single-scan group in all measured regions. The VD around the optic nerve in the denoised group was correlated with that in the single-scan group (R = 0.9403, P < 0.0001), but the VD in the MIA group was not correlated with that in the single-scan group (R = 0.2505, P = 0.2076). The VD around the fovea in the denoised and MIA images was correlated with that in the single-scan group (R = 0.7377, P < 0.0001; R = 0.7005, P = 0.0004, respectively). CONCLUSION: Denoising could provide an easy and quick way to improve image quality parameters, such as PSNR. It shows great potential in improving the sensitivity of OCTA images as retinal disease markers.

Shot-noise limited, supercontinuum-based optical coherence tomography.

We present the first demonstration of shot-noise limited supercontinuum-based spectral domain optical coherence tomography (SD-OCT) with an axial resolution of 5.9 µm at a center wavelength of 1370 nm. Current supercontinuum-based SD-OCT systems cannot be operated in the shot-noise limited detection regime because of severe pulse-to-pulse relative intensity noise of the supercontinuum source. To overcome this disadvantage, we have developed a low-noise supercontinuum source based on an all-normal dispersion (ANDi) fiber, pumped by a femtosecond laser. The noise performance of our 90 MHz ANDi fiber-based supercontinuum source is compared to that of two commercial sources operating at 80 and 320 MHz repetition rate. We show that the low-noise of the ANDi fiber-based supercontinuum source improves the OCT images significantly in terms of both higher contrast, better sensitivity, and improved penetration. From SD-OCT imaging of skin, retina, and multilayer stacks we conclude that supercontinuum-based SD-OCT can enter the domain of shot-noise limited detection.

Expression of purinergic receptors on microglia in the animal model of choroidal neovascularisation.

To investigate the effect of P2 receptor on microglia and its inhibitor PPADS on choroidal neovascularization. Forty CX3CR1GFP/+ mice were randomly divided into 8 groups. In addition to the normal group, the rest of groups were receiving laser treatment. The retina and choroid from the second, third, fourth and fifth group of mice were taken in the 1, 4, 7, 14 days after laser treatment. The mice in the sixth and seventh group received intravitreal injection of 2 µl PPADS or PBS respectively immediately after laser treatment. The mice in the eighth group received topical application of PPADS once per day of three days. The mice in sixth, seventh and eighth group received AF and FFA examination on the fourth day after laser treatment. Immunofluorescence histochemical staining and real-time quantitative PCR were used to evaluate P2 expression and its effect on choroidal neovascularization. After laser treatment, activated microglia can express P2 receptors (P2X4, P2X7, P2Y2 and P2Y12). The expression of P2 increased on the first day after laser damage, peaked on the fourth day (tP2X4 = 6.05, tP2X7 = 2.95, tP2Y2 = 3.67, tP2Y12 = 5.98, all P < 0.01), and then decreased. After PPADS inhibition, compared with the PBS injection group, the mRNA of P2X4, P2X7, P2Y2 and P2Y12 were decreased significantly in the PPADS injection group (tP2X4 = 5.54, tP2X7 = 9.82, tP2Y2 = 3.86, tP2Y12 = 7.91, all P < 0.01) and the PPADS topical application group (tP2X4 = 3.24, tP2X7 = 5.89, tP2Y2 = 6.75, tP2Y12 = 4.97, all P < 0.01). Compared with the PBS injection group, not only the activity of microglia cells but also the leakage of CNV decreased significantly (P < 0.01) in the PPADS injection group and the PPADS topical application group. But between two PPADS groups, the leakage of CNV had no difference (P = 0.864). After laser induced CNV, activated microglia can express P2 receptors. The P2 receptor inhibitor, PPADS, can significantly affect the function of microglia and inhibit the formation of choroidal neovascularization.

Lack of WWC2 Protein Leads to Aberrant Angiogenesis in Postnatal Mice.

The WWC protein family is an upstream regulator of the Hippo signalling pathway that is involved in many cellular processes. We examined the effect of an endothelium-specific WWC1 and/or WWC2 knock-out on ocular angiogenesis. Knock-outs were induced in C57BL/6 mice at the age of one day (P1) and evaluated at P6 (postnatal mice) or induced at the age of five weeks and evaluated at three months of age (adult mice). We analysed morphology of retinal vasculature in retinal flat mounts. In addition, in vivo imaging and functional testing by electroretinography were performed in adult mice. Adult WWC1/2 double knock-out mice differed neither functionally nor morphologically from the control group. In contrast, the retinas of the postnatal WWC knock-out mice showed a hyperproliferative phenotype with significantly enlarged areas of sprouting angiogenesis and a higher number of tip cells. The branching and end points in the peripheral plexus were significantly increased compared to the control group. The deletion of the WWC2 gene was decisive for these effects; while knocking out WWC1 showed no significant differences. The results hint strongly that WWC2 is an essential regulator of ocular angiogenesis in mice. As an activator of the Hippo signalling pathway, it prevents excessive proliferation during physiological angiogenesis. In adult animals, WWC proteins do not seem to be important for the maintenance of the mature vascular plexus.

Retina Vascular Perfusion Dynamics During Exercise With and Without Face Masks in Healthy Young Adults: An OCT Angiography Study.

Purpose: To determine possible impacts on retinal microvasculature in healthy young adults during exercise with a face mask, using optical coherence tomography angiography (OCTA). Methods: Twenty-three healthy participants (23 eyes, 17 women and 6 men) performed the incremental continuous running test (ICRT) with different masks. OCTA of the macula and optic nerve head were performed before and after ICRT to detect changes in retinal vessel density (VD). All participants were in groups A, B, and C (before ICRT) and groups A', B', and C' (after ICRT), which comprised data from volunteers without a mask, with a surgical mask, and with an N95 mask, respectively. Results: Before ICRT, group C showed significantly reduced VD in the superficial plexus (SP), except foveal VD, compared with group A (P < 0.05). After ICRT, groups B' and C' showed significantly shorter maximum running time, lower oxygen saturation, and lower perifoveal VD of SP compared with group A' (P < 0.05). Conclusions: Use of an N95 mask reduced VD in SP even under quiescent conditions, which might have clinical implications for protecting healthy workers and indoor manual labor workers from potential risks of retinal damage due to long-term mask use. Moreover, mask use while exercising might lead to attenuated exercise ability and lower VD in SP, which should be investigated in additional studies. Translational Relevance: Retina vascular perfusion dynamics could be monitored in vivo by OCTA, which would be valuable to study physiologic retinal blood flow redistribution and potential impacts on retinal vascular perfusion during exercise with face masks.

Gene therapy with caspase-3 small interfering RNA-nanoparticles is neuroprotective after optic nerve damage.

Apoptosis, a key mechanism of programmed cell death, is triggered by caspase-3 protein and lowering its levels with gene therapy may rescue cell death after central nervous system damage. We developed a novel, non-viral gene therapy to block caspase-3 gene expression using small interfering RNA (siRNA) delivered by polybutylcyanoacrylate nanoparticles (CaspNPs). In vitro CaspNPs significantly blocked caspase-3 protein expression in C6 cells, and when injected intraocularly in vivo, CaspNPs lowered retinal capsase-3 immunofluorescence by 57.9% in rats with optic nerve crush. Longitudinal, repeated retinal ganglion cell counts using confocal neuroimaging showed that post-traumatic cell loss after intraocular CaspNPs injection was only 36.1% versus 63.4% in lesioned controls. Because non-viral gene therapy with siRNA-nanoparticles can selectively silence caspace-3 gene expression and block apoptosis in post-mitotic neurons, siRNA delivery with nanoparticles may be promising for neuroprotection or restoration of central visual system damage and other neurological disorders. The animal study procedures were approved by the German National Act on the use of experimental animals (Ethic Committee Referat Verbraucherschutz, Veterinärangelegenheiten; Landesverwaltungsamt Sachsen-Anhalt, Halle, Germany, # IMP/G/01-1150/12 and # IMP/G/01-1469/17).

A modified protocol for isolation of retinal microglia from the pig.

Microglia are the resident immune cells in the retina. To investigate their properties and behaviour, a reliable and yielding procedure to culture them is necessary. We here describe a way of isolation of microglial cells from the porcine retina, as pig eyes are similar to human eyes in size, structure and vasculature, including similarities in proteins and pathways. Retina was isolated from fresh pig eyes, dissociated by a mixture of collagenase, hyaluronidase and DNAse, and passed through a cell strainer. After triple centrifugation with decreasing velocity and re-suspension, cells were seeded into poly-d-lysine coated culture flasks and cultured using DMEM and macrophage-colony stimulating factor (M-CSF). Number of cells increased gradually during the first 10-14 days, till they could be split and used for experiments. Identity of isolated cells as microglia was assessed by immunostaining against the microglia/macrophage markers Iba1, CD11b, CD68, CD45 and TMEM119. Phagocytic function of microglia could be demonstrated by phagocytosis of fluorescence beads and their response to lipopolysaccharide (LPS). As a conclusion, we developed a protocol for isolation and cultivation of pig retinal microglial cells that are suitable for research in the laboratory.

The Hippo pathway component Wwc2 is a key regulator of embryonic development and angiogenesis in mice.

The WW-and-C2-domain-containing (WWC) protein family is involved in the regulation of cell differentiation, cell proliferation, and organ growth control. As upstream components of the Hippo signaling pathway, WWC proteins activate the Large tumor suppressor (LATS) kinase that in turn phosphorylates Yes-associated protein (YAP) and its paralog Transcriptional coactivator-with-PDZ-binding motif (TAZ) preventing their nuclear import and transcriptional activity. Inhibition of WWC expression leads to downregulation of the Hippo pathway, increased expression of YAP/TAZ target genes and enhanced organ growth. In mice, a ubiquitous Wwc1 knockout (KO) induces a mild neurological phenotype with no impact on embryogenesis or organ growth. In contrast, we could show here that ubiquitous deletion of Wwc2 in mice leads to early embryonic lethality. Wwc2 KO embryos display growth retardation, a disturbed placenta development, impaired vascularization, and finally embryonic death. A whole-transcriptome analysis of embryos lacking Wwc2 revealed a massive deregulation of gene expression with impact on cell fate determination, cell metabolism, and angiogenesis. Consequently, a perinatal, endothelial-specific Wwc2 KO in mice led to disturbed vessel formation and vascular hypersprouting in the retina. In summary, our data elucidate a novel role for Wwc2 as a key regulator in early embryonic development and sprouting angiogenesis in mice.

Biodegradable Nanoparticles Based on Pseudo-Proteins Show Promise as Carriers for Ophthalmic Drug Delivery.

Purpose: Drug delivery to treat ocular diseases still is a challenge in ophthalmology. One way to achieve drug delivery that is investigated currently is topical administration of drug-loaded polymeric nanoparticles (NPs) that are able to penetrate ocular barriers. The purpose of this study was optimal preparation of NPs made from pseudo-proteins and evaluation of their ability to penetrate ocular tissues. Methods: Biodegradable NPs of various types were prepared by nanoprecipitation of pseudo-protein composed of l-leucine (L), 1,6-hexanediol (6), and sebacic acid (8) (8L6). Arginine-based cationic polyester amides 8R6 and comb-like polyester amide containing lateral PEG-2000 chains along with 8L6 anchoring fragments in the backbones were used to construct positively charged and PEGylated NPs. They were loaded with fluorescein diacetate (FDA) or rhodamine 6G (Rh6G) as fluorescent probes. Suspensions of the NPs were given to cultivated microglial cells and retinal pigment epithelial (RPE) cells as well as topically on eyes of C57BL/6 mice. Penetration of NPs into the eyes was checked by fluorescence analysis. Results: NPs were prepared, and their properties were characterized. Cultured microglial cells and RPE cells took up the NPs. After topical administration, penetration of NPs into the cornea of the eyes was clearly seen. Small amounts of fluorescent dyes were also found in the lens, the retina, and the sclera depending on the type of NPs. Conclusions: The results showed that the new NPs penetrate ocular tissues after topical administration and are internalized by the cells. This raises confidence that the NPs may be useful carriers of therapeutic agents for ocular delivery.

ALTERED RETINAL PERFUSION IN PATIENTS WITH INACTIVE GRAVES OPHTHALMOPATHY USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

Objective: The aim of this study was to evaluate retinal and optic nerve head (ONH) perfusion in patients with inactive Graves ophthalmopathy (GO) and compare it to healthy controls using optical coherence tomography angiography (OCTA). Methods: Twenty-nine eyes of 29 patients with inactive GO (study group) and 29 eyes of 29 healthy subjects (control group) were included in this study. The vessel density (VD) data in the superficial and deep retinal OCT angiogram of the macula and the radial peripapillary capillary network (RPC) were extracted and analyzed. OCTA was performed using RTVue XR Avanti with AngioVue (Optovue Inc, Fremont, CA). Clinical activity was evaluated using the clinical activity score, the severity assessment using the NOSPECS classification. Results: The VD in the superficial OCT angiogram and in the OCT angiogram of the ONH was significantly lower in the GO group when compared to the control group (whole en face, P = .016; parafovea, P = .026; RPC peripapillary, P = .027). There was no significant correlation between VD and functional parameters or the NOSPECS classification. Conclusion: Macular VD and ONH capillary density measured using OCTA were significantly lower in the study group compared to healthy controls. Noninvasive quantitative analysis of retinal perfusion using OCTA could be useful in monitoring patients with GO. Abbreviations: CAS = clinical activity score; GO = Graves ophthalmopathy; OCTA = optical coherence tomography angiography; ONH = optic nerve head; RPC = radial peripapillary capillary; rSp = Spearman's correlation coefficient; VD = vessel density.

Occurrence of Transmembrane Protein 119 in the Retina is Not Restricted to the Microglia: An Immunohistochemical Study.

PURPOSE: Recently, a new marker protein for microglial cells in the brain was postulated, transmembrane protein 119 (TMEM119), raising the hope for a new opportunity to reliably and unambiguously detect microglial cells in histologic sections. It was of interest whether TMEM119 also was a reliable microglial marker in the retina. METHODS: Anti-TMEM119 antibodies of two providers were used to label microglia in the murine retina, and labeling properties were compared to those of antibodies against Iba1 and CD11b. As an example of a pathologic situation, labeling for TMEM119 was also performed in eyes treated by an argon laser as an experimental model for choroidal neovascularization. RESULTS: TMEM119 immunoreactivity (IR) was found on microglial cells in the naïve retina. However, specificity and sensitivity of TMEM119 IR varied clearly depending on the source of the antibody, age of the mouse, and location of retinal microglia. After laser treatment, however, microglial cells lost their IR for TMEM119 at the site of the laser spot. Moreover, other cells became positive for TMEM119; for example, Müller cells. CONCLUSIONS: TMEM119 is a useful marker for the microglia in the brain. However, retinal microglia shows variable IR for TMEM119, and the microglia is not the only cell showing TMEM IR. Therefore, TMEM119 appears not to be applicable as a general marker for the retinal microglia in pathologic situations. TRANSLATIONAL RELEVANCE: Reliable detection and quantification of microglial cells is of high importance to study disease mechanisms and effects of therapeutic approaches in the retina.