Detection of early age-related macular degeneration using novel functional parameters of the focal cone electroretinogram

The focal cone electroretinogram is a sensitive marker for macular disease, but have we unlocked its full potential? Typically assessment of waveform parameters is subjective and focuses on a small number of locations (e.g. the a-wave). This study evaluated the discriminatory and diagnostic potential of 4 conventional and 15 novel, objectively determined, parameters in patients with early Age-related Macular Degeneration. Focal cone electroretinograms were recorded in 54 participants with early Age-related Macular Degeneration (72.9±8.2 years) and 54 healthy controls (69±7.7 years). Conventional a and b wave amplitudes and implicit times were measured and compared to novel parameters derived from both the 1st and 2nd derivatives and the frequency-domain power spectrum of the electroretinogram.Statistically significant differences between groups were shown for all conventional parameters, the majority of 1st and 2nd derivative parameters and the power spectrum at 25 and 30 Hz. Receiver operating characteristics showed that both conventional and 1st and 2nd derivative implicit times had provided the best diagnostic potential. A regression model showed a small improvement over any individual parameter investigated. The non-conventional parameters enhanced the objective evaluation of the focal electroretinogram, especially when the amplitude was low. Furthermore, the novel parameters described here allow the implicit time of the electroretinogram to be probed at points other than the peaks of the a and b waves. Consequently these novel analysis techniques could prove valuable in future electrophysiological investigation, detection and monitoring of Age-related Macular Degeneration

A morphological study of retinal changes in unilateral amblyopia using optical coherence tomography image segmentation.

OBJECTIVE: The purpose of this study was to evaluate the possible structural changes of the macula in patients with unilateral amblyopia using optical coherence tomography (OCT) image segmentation. PATIENTS AND METHODS: 38 consecutive patients (16 male; mean age 32.4+/-17.6 years; range 6-67 years) with unilateral amblyopia were involved in this study. OCT examinations were performed with a time-domain OCT device, and a custom-built OCT image analysis software (OCTRIMA) was used for OCT image segmentation. The axial length (AL) was measured by a LenStar LS 900 device. Macular layer thickness, AL and manifest spherical equivalent refraction (MRSE) of the amblyopic eye were compared to that of the fellow eye. We studied if the type of amblyopia (strabismus without anisometropia, anisometropia without strabismus, strabismus with anisometropia) had any influence on macular layer thickness values. RESULTS: There was significant difference between the amblyopic and fellow eyes in MRSE and AL in all subgroups. Comparing the amblyopic and fellow eyes, we found a statistically significant difference only in the thickness of the outer nuclear layer in the central region using linear mixed model analysis keeping AL and age under control (p = 0.032). There was no significant difference in interocular difference in the thickness of any macular layers between the subgroups with one-way between-groups ANCOVA while statistically controlling for interocular difference in AL and age. CONCLUSIONS: According to our results there are subtle changes in amblyopic eyes affecting the outer nuclear layer of the fovea suggesting the possible involvement of the photoreceptors. However, further studies are warranted to support this hypothesis

Histone Deacetylase Inhibition Restores Retinal Pigment Epithelium Function in Hyperglycemia.

In diabetic individuals, macular edema is a major cause of vision loss. This condition is refractory to insulin therapy and has been attributed to metabolic memory. The retinal pigment epithelium (RPE) is central to maintaining fluid balance in the retina, and this function is compromised by the activation of advanced glycation end-product receptors (RAGE). Here we provide evidence that acute administration of the RAGE agonist, glycated-albumin (gAlb) or vascular endothelial growth factor (VEGF), increased histone deacetylase (HDAC) activity in RPE cells. The administration of the class I/II HDAC inhibitor, trichostatin-A (TSA), suppressed gAlb-induced reductions in RPE transepithelial resistance (in vitro) and fluid transport (in vivo). Systemic TSA also restored normal RPE fluid transport in rats with subchronic hyperglycemia. Both gAlb and VEGF increased HDAC activity and reduced acetyl-α-tubulin levels. Tubastatin-A, a relatively specific antagonist of HDAC6, inhibited gAlb-induced changes in RPE cell resistance. These data are consistent with the idea that RPE dysfunction following exposure to gAlb, VEGF, or hyperglycemia is associated with increased HDAC6 activity and decreased acetyl-α-tubulin. Therefore, we propose inhibiting HDAC6 in the RPE as a potential therapy for preserving normal fluid homeostasis in the hyperglycemic retina

HDAC inhibition blocks Glyc-Alb induced activation of HDACs.

<p>(A) ARPE19 cells showed a significant decrease in Ac-α-tubulin at 6 h post treatment of Glyc-alb (100 μg/mL) compared to administration of the same concentration of Alb. ARPE19 cells showed an increase in HDAC1/2/3/6 activity (B) and HDAC6 activity (C) at 6 h post treatment with Glyc-alb (100 μg/mL) compared to the administration of the same concentration of Alb. 1 h pre-treatment with 100 nM TSA (a pan-HDAC inhibitor) prevented the effect of Glyc-Alb. Values represent means ± SE of individual measurements normalized to average TEER at 0 h, analyzed by Student T-test. Column numbers represent <i>n</i> for each condition. **<i>p</i><0.01, ***<i>p</i><0.001. Legend: Ac-α-tubulin, Ac-α-tub, acetyl-α-tubulin; Alb, albumin; Glyc-alb, glycated-albumin; HDAC, histone deacetylase; TSA, trichostatin-A.</p

HDAC inhibition blocks Glyc-alb induced reduction in TEER.

<p>Administration of 100 μg/mL Glyc-alb with and without TSA pretreatment (1 h) to (A) ARPE 19 cells and (B) hfRPE cells showing the resulting TEER at 6 h post treatment compared to the administration of the same concentration of Alb. (C) Concentration-response curve to TSA determined for ARPE19 cells exposed to 100 μg/mL Glyc-alb. Values represent means ± SE of individual measurements normalized to average TEER at 0 h, analyzed by one-way ANOVA. Column numbers represent <i>n</i> for each condition. *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001. Legend: Alb, albumin; Glyc-alb, gAlb, glycated-albumin; TEER, transepithelial electrical resistance; TSA, trichostatin-A.</p

HDAC6 inhibition blocks effect of Glyc-Alb.

<p>Pretreatment of ARPE19 cells with 1 μM TubA (an HDAC6 specific inhibitor) for 1 h prevented the reduction in TEER seen with Glyc-Alb measured at 6 h post treatment. Values represent means ± SE of individual measurements normalized to average TEER at 0 h, analyzed by ANOVA. Column numbers represent <i>n</i> for each condition. *<i>p</i><0.05. Legend: Alb, albumin; Glyc-alb, glycated-albumin; TEER, transepithelial electrical resistance; TubA, tubastatin-A.</p