Cengiz Türksever

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.

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.

Retinal vessel oxygen saturation in patients suffering from inherited diseases of the retina.

PURPOSE The aim of this study was to evaluate the oxygen saturation in patients with inherited diseases of the retina. METHODS Fundus oximetry images were taken using a retinal vessel analyser (IMEDOS Systems UG, Jena, Germany). Retinal vessel oximetry was performed in 53 eyes of 27 patients suffering from inherited retinal diseases and compared to 22 eyes of 11 healthy controls. The oxygen saturation in all four major retinal arterioles (A-SO2) and venules (V-SO2) were measured and their difference (A-V SO2) was calculated. The data were compared within groups and to controls. RESULTS Based on V-SO2 values, the rod-cone dystrophy group (66.46%; SD, ± 5.09) could well be differentiated from controls 54.02% (SD, ± 3.04), from cone-rod dystrophies 57.56% (SD, ± 5.66), as well as from inherited maculopathies 58.42% (SD, ± 4.74). The mean A-SO2 in the rod-cone dystrophy group was increased to 98.96% (SD, ± 6.06, p<0.014), while in the cone-rod group and in the maculopathy group it was 92.75% (SD, ± 3.75), respectively 94.44% (SD ± 4.85), closer to the normal values (92.68%; SD, ± 3.53, p>0.05). The A-V SO2 difference, as an indirect indicator for retinal oxygen use, was reduced in the rod-cone patients, however only when the controls were taken into account (p=0.01). CONCLUSION This is to our knowledge the first study which proposes the retinal vessel oximetry to be a sensitive measure for differentiating rod-cone dystrophy patients not only from controls, but also from patients with other inherited retinal dystrophies.

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).

Effect of ageing on the retinal vascular responsiveness to flicker light in glaucoma patients and in ocular hypertension

Aim To evaluate the effect of ageing on the retinal vascular responsiveness to flicker light in glaucoma and ocular hypertension (OHT). Methods Retinal vascular response to flicker was measured with the retinal vessel analyser in 56 healthy subjects (59±9 years), 50 primary open-angle glaucoma (POAG) (60±10 years) and 46 OHT patients (62±9 years). In the glaucoma group, the less damaged eye; in the OHT group, the eye with the higher intraocular pressure; and in healthy controls, one randomly selected eye was considered. Parametric and non-parametric linear regression analysis, as well as a model of covariance analysis (ANCOVA) was used to evaluate the effect of age on the vascular response. Results In all three groups (N=152) absolute (Pearson R: −0.19, p<0.019; Spearman R: −0.22, p<0.006) and relative change (Pearson R: −0.18, p<0.027; Spearman R: −0.21, p<0.010) were statistically associated with age. The ANCOVA showed no difference between the three groups in this regard (absolute change: p=0.43; relative change: p=0.51). Conclusions Vascular responsiveness to flicker light decreases with age in healthy individuals, in glaucoma patients and in OHT patients. This effect seems to be comparable between the tested groups, and age-related change in vascular responsiveness to flicker light seems an unlikely risk factor for glaucoma.

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).

Retinal Vessel Oxygen Saturation in Giant Cell Arteritis Patients without Ocular Symptoms

BACKGROUND The aim of this study was to determine subclinical ocular ischemia related to giant cell arteritis (GCA) by means of retinal oximetry (RO) measurements. PATIENTS AND METHODS Four test-retest RO images per eye were taken with the retinal vessel analyser (IMEDOS Systems UG, Jena). RO measurements in arterial (A-SO2) and venous (V-SO2) retinal vessels and their difference (A-V SO2) were calculated in GCA patients and compared to those of age-matched controls. RESULTS GCA biopsy and duplex sonography positive patients (n=8, 13 eyes) from the Basler Riesenzellarteriitis Kohorte study (BARK) were recruited. In controls (n=6, 10 eyes), the mean (± SD) A-SO2 and V-SO2 were measured at 93.89% (± 3.0) and at 55.60% (± 3.4), respectively. In the GCAs, a reduction in the A-SO2 to 93.37% (± 3.3) and an increase in V-SO2 to 61.13% (± 3.6) were found. The A-V SO2 difference was reduced in the GCAs to 32.24% (± 3.8) whereas in the controls the difference was 38.31% (± 2.8). CONCLUSIONS Oxygen metabolism is affected in cases with GCA. Thus, RO may provide additional data in the diagnosis of GCA, even when no ophthalmic symptoms have been reported.

Comparing Short-Duration Electro-Oculograms with and without Mydriasis in Healthy Subjects.

BACKGROUND In order to obtain artifact-free electro-oculogram recordings the subjects cooperation is necessary. The aim of our study is to evaluate the recording characteristics of short-duration EOG and to compare the effect of mydriasis on electro-oculogram recordings in a cohort of controls. PATIENTS AND METHODS Electro-oculogram recordings were performed on a light-emitting diode stimulus screen using a RETI-port gamma plus2 system (RETIscan™, Roland Consult). Fast oscillations were set at 1.5 sec (6 cycles; total duration 75 sec).The dark phase included: pre-adaptation (6 min), alternate fixation (4 min), fixation-rest (20 sec), 100 sweeps. The light phase included: light adaptation (4 min), alternate fixation (10 min), fixation-rest (20 sec), 250 sweeps. The amplifier band pass was filtered at 0.1÷50 Hz. The background illumination in mydriasis was 100 cd/m2 and in miosis--450 cd/m2. RESULTS A total of 55 controls participated and were divided into three age groups [number; mean (years, y); ±SD]: group 1: 18-20 years (19; 19.49 years; ±0.89); group 2: 20-40 years (18; 27.91 years; ±5.39) and group 3: 40-60 years (18; 48.66 years; ±4.00). The Arden ratio, dark-trough and light-peak did not differ between recordings with or without mydriasis (p=0.914; p=0.880; p=0.680, linear mixed-effects model). The age did not influence the Arden ratio, dark-trough, light-peak (p=0.206; p=0.112; p=0.155). Arden ratio, dark-trough, light-peak were comparable between tested eyes (p=0.934; p=0.193; p=0.270). CONCLUSIONS Short-duration electro-oculograms allow successful recording, furthermore, the application of mydriasis does not influence the quality of the recording.

Analysis of risk factors for long-term glaucomatous damage development.

PURPOSE The aim of this study was to analyze predictors of long-term glaucoma progression. PATIENTS AND METHODS We followed 17 primary open angle glaucoma patients (POAG) and 25 ocular hypertensives (OHT) over three years, with regular follow-up examinations of both eyes every 6 months. Glaucoma damage was quantified by optical coherence tomography (retinal nerve fiber layer - OCT RNFL) and by perimetry. Corneal and hand temperature (infrared thermometer), corneal hysteresis, pachymetry and ocular pulse amplitude (OPA) readings were taken at baseline, and applanatory intraocular pressure and retinal vessel analysis recordings were made at baseline and follow-up visits. Forward-stepwise multiple regression analysis was performed. RESULTS With OCT-RNFL progression as the dependent variable, the model selected initial diagnosis (OHT less probable of progressing), baseline RNFL thickness, retinal arterial and venous diameter and arterial flicker response as significant damage predictors. For visual field damage progression, these were: corneal temperature, OPA, initial diagnosis and venous flicker response (all p<0.05). CONCLUSION Initial damage and vascular factors are strong predictors of future glaucoma progression.