Ablation of Ctrp9, Ligand of AdipoR1, and Lower Number of Cone Photoreceptors in Mouse Retina.

Purpose: C1q/TNF-related protein (CTRP) 9 is one of the adiponectin paralogs, and a genetic ablation of its receptor, AdipoR1, is known to cause retinal degeneration. The purpose of this study was to determine the role played by CTRP9 in the retina. Methods: The retinas of Ctrp9 gene knockout (KO) and wild type (WT) mice were examined by electroretinography (ERG), histology, RNA sequencing, and quantitative real-time PCR. Results: The amplitude of the photopic ERG elicited by the maximum stimulus intensity was smaller by 40% in the Ctrp9 KO mice than in WT mice at 8 weeks of age. However, the photopic ERGs was not reduced from 8 weeks to 6 months of age. The amplitudes of the scotopic ERGs were not reduced in the Ctrp9 KO mice at 8 weeks and 6 months of age. No distinct histological abnormalities were found in the retinal sections but the density of peanut agglutinin-stained cells in the retinal flat mount of KO mice was reduced to about 70% of that of WT mice. Genomewide RNA sequencing of the retina revealed the absence of the expression of CTRP9 in both KO and WT mice. RNA sequencing and quantitative real-time PCR analysis showed that the expressions of the transcripts of genes expressed in cones, Opn1sw, Opn1mw, Gnat2, and Cnga3, were reduced in the KO mice retina, however, the degree of expression of the transcripts in rods was not significantly reduced. Conclusions: CTRP9 is released ectopically from other tissues, and it regulates the number of cones in the mouse retinas.

Steeper Macular Curvature in Eyes With Non-Highly Myopic Retinitis Pigmentosa.

Purpose: A posterior staphyloma has been reported to be present in some eyes with retinitis pigmentosa (RP), and the purpose of this study was to determine the macular curvature of non-highly myopic RP eyes. Methods: This was a retrospective, observational study. The medical charts of the right eyes of 143 patients with RP and 60 controls whose axial length ranged from 21.5 mm to 26.0 mm were reviewed. The mean curvature of Bruch's membrane within 6 mm of the central macula obtained from the horizontal optical coherence tomographic images were evaluated as the mean macular curvature index (MMCI). The relationships between the MMCI and other clinical factors were assessed. Results: The mean MMCI of RP patients (-13.73 ± 9.63 × 10-5 µm-1) was significantly lower than that of the controls (-6.63 ± 5.63 × 10-5 µm-1). This indicated a deeper concave shape of the macula in RP eyes (P < 0.001). The MMCI was significantly correlated with the age (r = 0.20; P = 0.016) and the axial length (r = -0.24; P = 0.004). Further analysis suggested a nonlinear effect of the ellipsoid zone width on the macular curvature in the RP eyes. Conclusions: There is a high incidence of steeper macular curvatures even in non-highly myopic RP eyes, and the steepness was also affected by the degree of photoreceptor degeneration.

Electrically Evoked Potentials Are Reduced Compared to Axon Numbers in Rhodopsin P347L Transgenic Rabbits With Severe Photoreceptor Degeneration.

Purpose: To determine the relationship between the amplitudes of the electrically evoked potentials (EEPs) and the number of optic nerve axons at a late stage of retinal degeneration in rhodopsin P347L transgenic (Tg) rabbits, a model of retinitis pigmentosa. Methods: Six eyes of six wild-type (WT) (43.8 ± 7.5 months of age) and six eyes of six Tg (40.3 ± 2.6 months of age) rabbits were studied. The EEPs were elicited by 1 to 5 mA of transcorneal electrical stimulation. The first positive wave, the P1 component, was analyzed. After euthanasia, the number of axons in the optic nerve was counted. Results: The threshold current to elicit a P1 was significantly higher in Tg rabbits than WT rabbits. The amplitude of P1 elicited by 5 mA in Tg rabbits was about 24% of that in WT rabbits (P < 0.01). The number of axons in the optic nerve of Tg rabbits was reduced to about 59% of that of WT rabbits (P < 0.01). The correlation between the axon number and the amplitude of the P1 in Tg and WT rabbits was not significant. The mean ratio of the P1 amplitude/axon in Tg rabbits was decreased to 53% of that in WT rabbits (P < 0.05). Conclusions: The degree of reduction in the EEP in Tg rabbits is more severe than the reduction in the number of optic nerve axons. The use of transcorneal electrical stimulation to determine the suitable candidates for prosthesis at the end-stage of retinitis pigmentosa may underestimate the condition of the optic nerves.

Course of loss of photoreceptor function and progressive Müller cell gliosis in rhodopsin P347L transgenic rabbits.

Long living animal models of retinitis pigmentosa (RP) can provide important information on the retinal changes that occur at the late stages of photoreceptor degeneration. The rhodopsin Pro347Leu transgenic rabbit (P347L Tg) is a model of RP, and it has been used to analyze the functional and morphological changes in the retina following the degeneration of the photoreceptors. They have also been used to test newly-developed therapies to treat eyes with photoreceptor degeneration. However, assessments of the retinal changes in P347L Tg rabbits older than 1-year have not been reported even though the data are important for research on developing new therapies to restore vision at the end stages of RP. The purpose of this study was to determine the time course of the loss of photoreceptor function and the changes in the morphology of the retina of P347L Tg rabbits. The experiments were performed on 26 older P347L Tg rabbits. The results showed that the amplitudes of the ERGs of the P347L Tg rabbits gradually decreased and reached <10 µV between 30- and 54-months-of-age. Histological analysis at these later stages showed a loss of the photoreceptor layer, and OCT analysis showed absence of the layering of the retina. However, the thickness between the inner limiting membrane and the outer plexiform layer was about 1.7 times thicker than the corresponding thickness of WT rabbits in the OCT images. This thickening was caused by a marked gliosis of the entire retina which was confirmed by light and transmission electron microscopy. In addition, immunohistochemical analysis showed there was excessive staining of the glial fibrillary acid protein in the older P347L Tg rabbits although the rod ON bipolar cells and horizontal cells were still present in the inner nuclear layer. Our results indicate that the P347L Tg rabbit progressed to complete photoreceptor loss within 30- and 54-months-of-age and severe gliosis altered the morphology of the retina.

Three cases of acute-onset bilateral photophobia.

PURPOSE: To report the findings in 3 cases of bilateral negative electroretinograms (ERGs) with acute onset of photophobia. STUDY DESIGN: Retrospective case series. METHODS: The medical charts of the 3 patients were reviewed. RESULTS: A 43-year-old woman, a 68-year-old woman, and a 41-year-old woman were referred to Nagoya University Hospital. Their main symptom was bilateral acute photophobia. None of the patients had any systemic diseases or specific medical history. The decimal best-corrected visual acuity (> 0.8) and Humphrey visual fields (mean deviation > -3 dB) were relatively well preserved in all 3 patients. The optical coherence tomography (OCT) and fundus autofluorescence findings were essentially normal. Fluorescein angiography showed mild leakage in 1 patient but no abnormality in the other 2 patients. However, the ERGs of the 3 patients had the features of abnormal ERGs found in patients with incomplete congenital stationary night blindness (CSNB). Exome analyses found no pathogenic variants related to known CSNB-related genes. The symptoms and ERGs of the 3 patients have not progressed or recovered after a relatively long follow-up period. CONCLUSION: The ERG characteristics of 3 patients with bilateral photophobia were similar to those of incomplete CSNB, suggesting post-phototransductional abnormalities. The symptoms and genetic analyses indicated the possibility of an acquired condition rather than a hereditary retinal disease.

CLINICAL COURSE OF PARANEOPLASTIC RETINOPATHY WITH ANTI-TRPM1 AUTOANTIBODY IN JAPANESE COHORT.

PURPOSE: To report the clinical course of eyes with paraneoplastic retinopathy caused by an autoantibody against transient receptor potential cation channel, subfamily M, member 1 (TRPM1). METHODS: Ten paraneoplastic retinopathy patients with retinal ON-bipolar cell dysfunction, including six melanoma-associated retinopathy, from eight institutions in Japan were evaluated for the presence of an anti-TRPM1 antibody. The results of ophthalmic examinations and the presence of anti-TRPM1 antibody were analyzed. RESULTS: Five patients were positive for the anti-TRPM1 antibody. These patients had similar clinical findings in both eyes at the time of diagnosis; relatively preserved best-corrected visual acuity, absence of fundus and optical coherence tomography abnormalities, and specific abnormalities of the electroretinography (ERG); and negative-type ERGs with bright stimulus flashes. One patient whose retinal ON-bipolar cells remained dysfunctional for the entire testing period, although the anti-TRPM1 antibody had disappeared. On the other hand, the ERGs recovered in 2 cases within 2 years after the onset. One case progressed to additional impairment of the photoreceptors with deterioration of ERGs. One case died and the clinical course was unavailable. CONCLUSION: Paraneoplastic retinopathy patients with retinal ON-bipolar cell dysfunction possess autoantibodies against TRPM1 at the onset of the disease process; however, the clinical course of these eyes can be different.

Significant Relationship of Visual Field Sensitivity in Central 10° to Thickness of Retinal Layers in Retinitis Pigmentosa.

Purpose: To determine the relationship between the sensitivity of the retina in the central 10° and the thickness of the retinal layers in patients with retinitis pigmentosa (RP). Methods: Fifty-two RP patients were studied. All of the patients had been examined by the Humphrey Field Analyzer 10-2 program (HFA10-2) and spectral-domain optical coherence tomography (SD-OCT). The thicknesses of the photoreceptor outer segment (OS), outer nuclear layer (ONL), inner nuclear layer (INL), and the retinal nerve fiber layer (RNFL) were measured at 1°, 3°, 5°, 7°, and 9° from the fovea. The same measurements were made on the SD-OCT images of 40 healthy subjects and used as controls. The relationships between the retinal sensitivities and retinal layer thicknesses were determined. Results: The thicknesses of the OS and ONL and their product were significantly and positively correlated with the retinal sensitivities. The thickness of the INL was significantly and negatively correlated with the sensitivity. The strongest correlation with the sensitivity was with the OS thickness (marginal R2 [mR2] = 0.525, P < 0.001), followed by the product of the OS and ONL thicknesses (mR2 = 0.420, P < 0.001), ONL thickness (mR2 = 0.416, P < 0.001), and the INL thickness (mR2 = 0.014, P = 0.044). The thickness of the RNFL was not correlated with the sensitivity (mR2 = 0.005, P = 0.331). Conclusions: In contrast to previous reports, the thickness of the OS reflected the retinal sensitivity better than the product of OS and ONL.

Quantification of Macular Microvascular Changes in Patients With Retinitis Pigmentosa Using Optical Coherence Tomography Angiography.

Purpose: To evaluate the microvascular changes in eyes with RP quantitatively using optical coherence tomography angiography (OCTA) and to determine whether the correlations between these indices and the severity of RP are significant. Methods: This was a retrospective, observational study. The medical records of 53 RP patients and 46 controls were reviewed. The OCTA images were obtained with the Cirrus 5000 with Angioplex, and an automated program was used to analyze the microvascular patterns. The perfusion density (PD) and vessel length density (VLD) were used as indices of the microvascular density, whereas the vessel diameter index (VDI) was used as a measure of the caliber of the vessels. The width of the ellipsoid zone (EZ) in the OCT images and the mean deviation (MD) of the Humphry Field Analyzer (HFA) were used to determine the severity of the RP. Student's t-tests and Spearman's correlation tests were used. Results: Both the PD and VLD in the superficial and deep plexuses and the whole retina were significantly reduced, and the VDI was significantly increased in RP patients compared with the corresponding values of the controls (P < 0.001). Spearman's rank tests indicated the RP severity was significantly correlated with the PD and VLD in all three layers (P < 0.001, r ranging from 0.50 to 0.87) and significantly correlated with VDI in the deep and the whole retina (P < 0.001, ranging from -0.64 to -0.73). Conclusions: Quantitative changes in the microvascular density might be useful for examining the pathophysiology of RP.

Longitudinal study of visual field changes determined by Humphrey Field Analyzer 10-2 in patients with Retinitis Pigmentosa.

The aim of this study is to determine the progress of the visual field defects obtained by the Humphrey Field Analyzer 10-2 program (HFA 10-2) in patients with retinitis pigmentosa (RP). The medical records of 45 eyes of 45 RP patients who had at least 3 visual field tests were reviewed. Linear mixed models were used to follow the changes of the mean deviation and the average sensitivity of 4, 12, and 20 points in three concentric squares, designated as S4, S12, and S20. The median follow-up time was 3.86 years [range: 1.93 to 9.86, IQR (Interquartile range): 3.01 to 4.93]. The median number of the visual field tests was 3 (range: 3 to 15, IQR: 3 to 4). The mean change of the MD was -0.46 dB/year (-5.80%/year). When the patients were grouped by the average initial MD, the less advanced group had slower progressions than the more advanced group in S4, S12, and S20. These results should be useful in understanding the pathological changes of RP in the central visual field.

Temporal Properties of Flicker ERGs in Rabbit Model of Retinitis Pigmentosa.

Purpose: We determined the effects of a remodeled inner retina on the flicker electroretinograms (ERGs) in a rabbit eye at an advanced stage of inherited retinal degeneration. Methods: Six wild-type (WT) and four rhodopsin P347L transgenic (Tg) rabbits were studied at 18 months of age. Flicker ERGs were elicited by sinusoidal stimuli at frequencies of 3.906 to 50.781 Hz. To block the ON and OFF retinal pathways, 2-amino-4-phosphonobutyric acid (APB), and 6-cyano-7-nitroquinoxaline-2, 3(1H, 4H)-dione (CNQX), respectively, were injected intravitreally. The amplitudes and phases of the fundamental components of the pre- and postdrug ERGs were analyzed. The postsynaptic APB (ON-) and CNQX (OFF-) sensitive components were determined by examining the phases and amplitude vectors. Results: The temporal properties of the Tg rabbits were different from those of the WT rabbits and had unique features; at 3.906 Hz, the amplitude was depressed but it increased by more than 3.5-fold at 15.625 Hz. The reduction of the amplitude at 3.906 Hz in Tg rabbits was caused by a cancelation of the ON and OFF components by a phase difference of 180°. On the other hand, an increase in the amplitude at 15.625 Hz in Tg rabbits was caused by the summation of the ON and OFF components, which had an approximate 120° phase difference. Conclusions: The temporal properties of the flicker ERGs of Tg rabbits were affected markedly by the remodeling of the retinal neurons. Evaluations of the flicker ERGs in RP eyes must be done with careful considerations of the current findings.