Margarita G. Todorova

Retinal vessel oxygen saturation and its correlation with structural changes in retinitis pigmentosa

To study the influence of retinal structural changes on oxygen saturation in retinitis pigmentosa (RP) patients.

Retinitis pigmentosa and ocular blood flow

Is the concept of integrative, preventive and personalised medicine applicable to the relationship between retinitis pigmentosa (RP) and ocular blood flow (OBF)? RP encompasses a group of hereditary diseases of the posterior segment of the eye characterised by degeneration, atrophy and finally loss of photoreceptors and retinal pigment epithelium, leading to progressive visual loss. Many different mutations affecting different genes can lead to the clinical picture of RP. Even though the disease has a clear genetic background, there are obviously other factors influencing the manifestation and progression of RP. In this review, we focus on the role of OBF. There is evidence that, in PR patients, OBF is more reduced than one would expect secondary to the retinal atrophy. The main cause of this additional component seems to be primary vascular dysregulation (PVD) syndrome. As PVD syndrome is partly treatable, a vascular evaluation of RP patients is meaningful. Based on the outcome, a targeted individualised, preventive or supportive treatment might be introduced in selected RP patients.

Reproducibility of retinal oximetry measurements in healthy and diseased retinas

Retinal oximetry (RO) has been established as a non‐invasive method to analyse oxygen saturation in retinal vessels. The aim of our study was to determine the reproducibility of RO images in healthy and in diseased retinas.

Metabolic and functional changes in retinitis pigmentosa: comparing retinal vessel oximetry to full-field electroretinography, electrooculogram and multifocal electroretinography

To determine a relationship between the retinal vessel saturation alterations and the residual retinal function measured by means of full‐field electroretinography (full‐field ERG), electrooculogram (EOG) and multifocal electroretinography (mfERG) in patients with retinitis pigmentosa (RP).

Peripapillary retinal vessel diameter correlates with mfERG alterations in retinitis pigmentosa.

To investigate relationship between the peripapillary retinal vessel diameter and the residual retinal function, measured by mfERG, in patients with retinitis pigmentosa (RP).

LED-generated Multifocal ERG On- and Off-responses in Complete Congenital Stationary Night Blindness – A Case Report

We report on the application of a light emitting diode (LED) screen to elicit multifocal ERG on- and off-responses in a patient presenting with the complete type of congenital stationary night blindness (cCSNB): A 63-years old woman was diagnosed with cCSNB by means of standard ERG procedures and dark adaptometry. To confirm this diagnosis and to investigate topographical differences of on- and off-responses a multifocal approach employing long-duration stimuli was added. Results of mfERG-testing were averaged in three groups (a central area of 7.5°, a ring area of 7.5–21.9° and a peripheral ring of 21.9–31.1°). When compared to normal controls (n = 4) on-responses (P1-amplitudes) were severely reduced symmetrically at all eccentricities, while off-responses showed no reduction resulting in an increased off/on-ratio. Furthermore on-latencies of P1 were delayed symmetrically at all eccentricities, whereas off-latencies were normal. To our knowledge this is the first report of multifocal on- and off-responses in a CSNB-patient. Stimulus-generation with a LED-screen provides the advantage of a stable luminance during the long-duration on-phase.

Reduced metabolic function and structural alterations in inherited retinal dystrophies: investigating the effect of peripapillary vessel oxygen saturation and vascular diameter on the retinal nerve fibre layer thickness

To evaluate the relationship between the peripapillary metabolic alterations [retinal vessel Oximetry (RO)] and the structural findings [retinal vessel diameter and retinal nerve fibre layer thickness (RNFL)] in patients with inherited retinal dystrophies (IRD).

The trilateral link between anaesthesia, perioperative visual loss and Flammer syndrome.

BackgroundA variety of factors have been linked to perioperative visual loss during or directly after nonocular and ocular surgeries. Prolonged immobilization, biochemical factors and hemodynamic instability have been discussed as factors in the pathogenesis of this devastating complication. Perioperative visual loss in four consecutive patients, all featuring Flammer syndrome, is reported herein. To our knowledge, we present the first case series, which associates perioperative visual loss with Flammer syndrome. We assume that a low perfusion pressure, disturbed autoregulation of the ocular blood flow and altered drug sensitivity in such subjects, play significant role in the pathogenesis of this dreaded complication.Cases presentationWe analysed the medical records of four consecutive patients with permanent perioperative visual loss and complemented our findings with additional history taking and clinical examinations. A variety of tests was performed, including colour Doppler ultrasonography of the retroocular vessels, static and dynamic retinal vessel analysis. The visual loss was unilateral in three patients and bilateral in one. An extensive review of published perioperative vision loss cases was conducted.All four patients were male Caucasians, and exhibited prominent signs and symptoms of Flammer syndrome. The visual loss originated from a propensity for unstable ocular blood flow, combined with hyperreactivity toward pharmacological stimuli, leading together to disturbed autoregulation of the blood supply, and subsequently - to ocular hypoxia. An identified intrinsic hypoperfusion diathesis was a crucial pathophysiologic link in all of the patients. Other, yet unknown systemic or local factors may also be involved in this process.ConclusionsA review of numerous publications of perioperative visual loss and our data, support our hypothesis for a novel pathophysiologic model and incorporate Flammer syndrome as a distinct risk factor for paradoxical visual loss, during nonocular and ocular surgeries, or invasive procedures. To prevent the complications produced by disturbed blood flow autoregulation in such patients, guidelines for screening and tailored preoperative approach are given.

Efficacy of Vitrectomy Combined with Subretinal Recombinant Tissue Plasminogen Activator for Subretinal versus Subpigment Epithelial versus Combined Hemorrhages.

Background: The aim of this study was to compare the outcomes after subretinal recombinant tissue plasminogen activator (rtPA) treatment for subretinal hemorrhages (SRH), subpigment epithelial hemorrhages (SPH), and combined subretinal and subpigment epithelial hemorrhages (CH). Methods: An observational analysis of patients treated with subretinal rtPA was performed. The primary endpoint was the assessment of visual improvement (best-corrected visual acuity, BCVA) after surgery. Secondary endpoints were evaluation of the maximal hemorrhage diameter (MHD) and central macular thickness (CMT) measured by spectral domain optical coherence tomography. Results: From a total of 83 eyes included in the study, 19 eyes showed SRH, 11 eyes SPH, and 53 eyes CH. For SRH and CH, the mean BCVA, MHD, and CMT improved significantly (p < 0.05). For patients with SPH, both the mean MHD and CMT decreased significantly (p < 0.05), whereas the mean BCVA improved only slightly after surgery (p = 0.28). Conclusion: Vitrectomy combined with subretinal rtPA injection and gas or air tamponade has a strong functional and anatomical effect on both SRH and CH and also seems to slightly improve the anatomical outcome in SPH.

Preserved functional and structural integrity of the papillomacular area correlates with better visual acuity in retinitis pigmentosa

PurposeLinking multifocal electroretinography (mfERG) and optical coherence tomography (OCT) findings with visual acuity in retinitis pigmentosa (RP) patients.DesignProspective, cross-sectional, nonintervention study.SubjectsPatients with typical RP and age-matched controls, who underwent SD-OCT (spectral domain OCT) and mfERG, were included.MethodsMfERG responses were averaged in three zones (zone 1 (0°–3°), zone 2 (3°–8°), and zone 3 (8°–15°)). Baseline-to-trough- (N1) and trough-to-peak amplitudes (N1P1) of the mfERG were compared with corresponding areas of the OCT. The papillomacular area (PMA) was analyzed separately. Correlations between best-corrected visual acuity (BCVA, logMAR) and each parameter were determined.Main outcome measuresComparing structural (OCT) and functional (mfERG) measures with the BCVA.ResultsIn RP patients, the N1 and N1P1 responses showed positive association with the central retinal thickness outside zone 1 (P≤0.002), while the central N1 and the N1P1 responses in zones 1, 2, and 3—with the BCVA (P≤0.007). The integrity of the IS/OS line on OCT showed also a positive association with the BCVA (P<0.001). Isolated analysis of the PMA strengthened further the structure–function association with the BCVA (P≤0.037). Interactions between the BCVA and the OCT, respectively, the mfERG parameters were more pronounced in the RP subgroup without macular edema (P≤0.020).ConclusionIn RP patients, preserved structure–function of PMA, measured by mfERG amplitude and OCT retinal thickness, correlated well with the remaining BCVA. The subgroup analyses revealed stronger links between the examined parameters, in the RP subgroup without appearance of macular edema.