Ocular pulse amplitude is reduced in patients with advanced retinitis pigmentosa

Mouse microphthalmia-associated transcription factor (Mitf) mutations affect the structure of the retinal vasculature

PURPOSE

Mice carrying pathogenic variants in the microphthalmia transcription factor (Mitf) gene show structural and functional changes in the retina and retinal pigment epithelium. The purpose of this study was to assess the vascular changes in Mitf mice carrying pathogenic variants by determining their retinal vessel diameter.

METHODS

Mice examined in this study were: B6-Mitf^mi-vga9/+ (n = 6), B6-Mitf^{mi-enu22(398)} /Mitf^{mi-enu22(398)} (n = 6) and C57BL/6J wild type mice (n = 6), all 3 months old. Fundus images were taken with a Micron IV camera after intraperitoneal injection of fluorescein salt. Images were adjusted to enhance contrast and a custom written MATLAB program used to extract the mean vascular diameter at a pre-defined distance from the optic disc. The number of vessels, mean diameter and mean total diameter were examined.

RESULTS

The mean diameter of retinal veins in Mitf^{mi-enu22(398)} /Mitf^{mi-enu22(398)} mice was 18.8% larger than in wild type (p = 0.026). No differences in the mean diameter of the retinal arteries were found between the genotypes. Mitf^{mi-enu22(398)} /Mitf^{mi-enu22(398)} mice have 17.2% more retinal arteries (p = 0.026), and 15.6% more retinal veins (p = 0.041) than wild type. A 24.8% increase was observed in the mean combined arterial diameter in mice with the Mitf^{mi-enu22(398)/} Mitf^{mi-enu22(398)} compared to wild type mice (p = 0.024). A 38.6% increase was found in the mean combined venular diameter in mice with the Mitf^{mi-enu22(398)} /Mitf^{mi-enu22(398)} pathogenic variation as compared to wild type (p = 0.004). The mean combined retinal venular diameter in the Mitf^mi-vga9/+ mice was 17.8% larger than in wild type (p = 0.03).

CONCLUSION

An increase in vascularization of the retina in Mitf^{mi-enu22(398)} /Mitf^{mi-enu22(398)} mice was found, indicating an increased demand for blood flow to the retina.

Retinal Vascular Abnormalities in Different Types of Inherited Retinal Dystrophies Assessed by Optical Coherence Tomography Angiography

Purpose:

To investigate the retinal vascular characteristics among patients with different types of inherited retinal dystrophies (IRDs).

Methods:

This comparative cross-sectional study was conducted on 59 genetically confirmed cases of IRD including 37 patients with retinitis pigmentosa (RP) (74 eyes), 13 patients with Stargardt disease (STGD) (26 eyes), and 9 patients with cone-rod dystrophy (CRD) (18 eyes). Both eyes of 50 age- and sex-matched healthy individuals were investigated as controls. All participants underwent optical coherence tomography angiography to investigate the vascular densities (VDs) of superficial and deep capillary plexus (SCP and DCP) as well as foveal avascular zone area.

Results:

In RP, significantly lower VD in whole image (P = 0.001 for DCP), fovea (P = 0.038 for SCP), parafovea (P < 0.001 for SCP and DCP), and perifovea (P < 0.001 for SCP and DCP) was observed compared to controls. In STGD, VD of parafovea (P = 0.012 for SCP and P = 0.001 for DCP) and fovea (P = 0.016 for DCP) was significantly lower than controls. In CRD, the VD of parafovea (P = 0.025 for DCP) was significantly lower than controls. Whole image density was significantly lower in RP compared to STGD (P < 0.001 for SCP) and CRD (P = 0.037 for SCP). VD in parafovea (P = 0.005 for SCP) and perifovea (P < 0.001 for SCP and DCP) regions was significantly lower in RP compared with STGD. Also, foveal VD in STGD was significantly lower than RP (P = 0.023 for DCP).

Conclusion:

Our study demonstrated lower VDs in three different IRDs including RP, STGD, and CRD compared to healthy controls. Changes were more dominant in RP patients.

Choroidal hyper-reflective foci and vascularity in retinal dystrophy

Purpose:

To investigate choroidal hyper-reflective foci (HRF) in subjects with retinal dystrophy [Stargardt's disease (SGD) and retinitis pigmentosa (RP)] and their association with demographics, visual acuity, choroidal thickness (CT), and choroidal vascularity index (CVI).

Methods:

Single center retrospective study of subjects with previously diagnosed SGD or RP. Swept-source optical coherence tomography images were analyzed for the presence of choroidal HRFs and CVI using previously validated automated algorithm. A Spearman's rank correlation coefficient was used to evaluate the correlation between the number of HRF and various baseline parameters including age, visual acuity, intraocular pressure, and other optical coherence tomography (OCT) parameters (CT, choroidal area, and CVI) were evaluated in these subjects.

Results:

This study included 46 eyes (23 subjects) and 55 eyes (28 subjects) with previously diagnosed RP and SGD, respectively. In the RP group, the mean number of HRFs was 247.9 ± 57.1 and mean CVI was 0.56 ± 0.04. In SGD group, mean HRF was 192.5 ± 44.3 and mean CVI was 0.41 ± 0.04. Mean HRF was significantly greater in the RP group (0.02), however, the mean CVI was not statistically different. In RP, mean HRF were correlated only with CVI (r = 0.49; P = 0.001), however, in SGD, it correlated with only choroidal area (r = 0.27; P = 0.04).

Conclusion:

Choroidal HRF were present in both RP and SGD subjects with more HRFs in those with RP. These HRFs were associated with alteration in choroidal vascularity, which further adds into the pathogenesis of these diseases.

CORRELATIONS BETWEEN CHOROIDAL STRUCTURES AND VISUAL FUNCTIONS IN EYES WITH RETINITIS PIGMENTOSA

The author report the structural changes in the inner and outer choroid determined by the binarization of enhanced depth imaging optical coherence tomographic images in 100 eyes with retinitis pigmentosa compared with 60 normal controls and significant correlations between the inner choroidal structures and visual functions in the eyes with retinitis pigmentosa.

Purpose:

To investigate the choroidal structures in the enhanced depth imaging optical coherence tomographic images in eyes with retinitis pigmentosa (RP) and to determine correlations between the choroidal structures and visual functions.

Methods:

The enhanced depth imaging optical coherence tomographic images of 100 eyes with typical RP and 60 age-, sex-, and axial length–matched normal eyes were binarized using ImageJ. The cross-sectional luminal and stromal areas of the inner and outer subfoveal choroid of 1,500-µm width were measured. The inner choroid included the choriocapillaris and medium vessel layer, and the outer choroid included the larger vessel layer.

Results:

In the inner choroid, the luminal area and the ratio of luminal/total choroidal area (L/C ratio) were significantly smaller in RP than in controls (P = 0.010, P < 0.001, respectively), whereas the stromal area was not significantly different (P = 0.114). The inner choroidal L/C ratio was significantly correlated with the best-corrected visual acuity, mean deviation, foveal sensitivity, width of the ellipsoid zone, and central foveal thickness in RP after adjusting for the axial length, age, and sex (all P < 0.005).

Conclusion:

The significant correlations between the inner choroidal structures and the visual functions and retinal structures indicate that the choroidal structures are altered in association with the progression of RP.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN PATIENTS WITH RETINITIS PIGMENTOSA

PURPOSE

To evaluate the correlation between the flow density measured by optical coherence tomography angiography and functional parameters in patients with retinitis pigmentosa.

METHODS

Twenty eyes of 20 patients with retinitis pigmentosa and 21 eyes of 21 healthy subjects were prospectively included in this study. Optical coherence tomography angiography was performed using RTVue XR Avanti with AngioVue (Optovue Inc). The macula was imaged with a 6 × 6-mm scan, whereas for the optic nerve head a 4.5 × 4.5-mm scan was taken. Visual acuity, visual field parameters (mean deviation and visual field index), full-field electroretinography, and multifocal electroretinography were tested for correlation with flow density data.

RESULTS

The flow density (whole en face) in the superficial/deep retinal OCT angiograms and in the optical coherence tomography angiography of the optic nerve head was significantly lower in the retinitis pigmentosa group when compared with the control group (P < 0.001). The flow density in the superficial retinal OCT angiogram (fovea) correlated significantly with the visual acuity (rSpearman = -0.77, P < 0.001) and the visual field parameters (visual field index: rSpearman = 0.56, P = 0.01; mean deviation: rSpearman = 0.54, P = 0.01).

CONCLUSION

Patients with retinitis pigmentosa show a decreased macular and optic nerve head perfusion compared with healthy subjects. The flow density measured using optical coherence tomography angiography correlated with subjective and objective functional parameters.

Choroidal structural analysis and vascularity index in retinal dystrophies

PURPOSE

To assess choroidal structural changes in patients with retinal dystrophies using choroidal vascularity index (CVI), a novel optical coherence tomography (OCT) based tool.

METHODS

This retrospective study included 26 patients with retinal dystrophies (17 with retinitis pigmentosa, four with Stargardt disease, three with cone-rod dystrophy, one each with Best disease and Bietti crystalline dystrophy) and 32 healthy controls. Subfoveal OCT images were used for analysis. Mean CVI was compared between retinal dystrophy and control group, as well as among the retinal dystrophy subgroups.

RESULTS

Mean CVI in eyes with retinal dystrophies was 52 ± 9% and it was significantly lower compared to that in normal eyes (70 ± 3%, p < 0.001). The differences among subgroups of retinal dystrophy were not statistically significant (p = 0.084). All types of retinal dystrophy were associated with lower CVI (all p < 0.001), after adjusting for age, gender, visual acuity and duration of symptoms. Older age was also shown to be independently associated with lower CVI (p = 0.012). Gender, visual acuity (VA) and duration of symptoms did not significantly affect CVI.

CONCLUSION

Decreased choroidal vascularity was seen in eyes with retinal dystrophies. (CVI) may be a helpful tool in monitoring choroidal involvement in retinal dystrophies.

EDI-OCT evaluation of choroidal thickness in retinitis pigmentosa

PURPOSE

To evaluate choroidal thickness (CT) in retinitis pigmentosa (RP) using enhanced depth imaging (EDI) optical coherence tomography (OCT).

METHODS

A retrospective analysis of a group of patients with RP who underwent EDI-OCT was performed. Choroidal thickness measurements were compared with those of age- and sex-matched healthy subjects. In the RP group, the possible association between subfoveal CT and some clinical parameters (visual acuity, age, age at disease onset, duration of the disease, macular thickness, visual field loss, electroretinography [ERG]) was evaluated.

RESULTS

The study recruited 39 patients with RP with an average age of 43.3 ± 11.3 years while the control group consisted of 73 healthy subjects with an average age of 42.9 ± 12.10 years. On average, CT was significantly thinner in the RP group compared to the controls (p<0.0001). In the RP group, we could not find any significant association between CT and the considered clinical parameters even if there was a trend for decreasing CT with increasing age (r = -0.23, p = 0.096). In the control group, subfoveal CT showed a slightly significant correlation with age (r = -0.21, p = 0.04) but not with macular thickness and visual acuity.

CONCLUSIONS

In our series, CT was significantly lower in the RP group in comparison with the controls, as measured by EDI-OCT, but did not correlate with age, age at onset, duration of the disease, macular thickness, visual acuity, visual field loss, or ERG responses. Although the clinical implications of choroidal changes in RP have not yet been clearly determined, the evaluation of choroidal features may provide information that could be useful to clarify the pathophysiology of the disease.

High-resolution Imaging in Male Germ Cell-Associated Kinase (MAK)-related Retinal Degeneration

PURPOSE

To describe the characteristics of MAK-related retinal degeneration using optical coherence tomography angiography (OCTA) and adaptive optics scanning laser ophthalmoscopy (AOSLO).

DESIGN

Cross-sectional study.

METHODS

Six patients with rod-cone degeneration and disease-causing mutations in MAK were evaluated with visual acuity, spectral-domain OCT, confocal AOSLO, and OCTA. Foveal avascular zone (FAZ) area, vessel densities, and perfusion densities of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in the central macula in all 6 patients were compared with 5 normal subjects. Cone spacing was measured in 4 patients from AOSLO images and compared with 37 normal subjects.

RESULTS

Patients ranged from 25 to 81 years of age (mean, 52 years). Visual acuity varied from 20/13 to 20/40+2, except in 1 patient with cystoid macular edema whose vision was 20/60- and 20/70+1. The SCP (P = .012) and DCP (P = .013) vessel density and perfusion density (P =.015 and .013, respectively) were significantly lower in patients compared to normal subjects in the parafoveal region 1.0-3.0 mm from the fovea, but were similar to normal subjects within 1.0 mm of the fovea. The FAZ area was not significantly different from normal (all P ≥ .24). Cone spacing was normal at almost all locations in 2 patients with early disease and increased in 2 patients with advanced disease.

CONCLUSIONS

Although retinal vascular densities are reduced and cone spacing is increased in advanced disease, central foveal structure is maintained until late stages of disease, which may contribute to preservation of foveal vision in eyes with MAK-related retinal degeneration.

Reduced Central Retinal Artery Blood Flow Is Related to Impaired Central Visual Function in Retinitis Pigmentosa Patients

PURPOSE

We evaluated the test-retest repeatability of blood flow velocities in the retrobulbar central retinal artery (CRA) and explored whether reduced blood flow is related to the degree of visual function loss in retinitis pigmentosa (RP) patients with wide range of disease severity.

MATERIALS AND METHODS

We measured CRA peak systolic velocity (PSV) and end diastolic velocity (EDV) to calculate mean flow velocity (MFV) in 18 RP patients using color Doppler imaging with spectral flow Doppler (GE Logiq7 ultrasound) twice in each eye at each of two visits within a month. At each of these two visits, we measured ETDRS visual acuity (VA), quick Contrast Sensitivity Function (qCSF), Goldmann visual fields (GVF), 10-2 Humphrey visual fields (HVF), and dark-adaptation at 5° from fixation with the AdaptDx; multifocal electroretinography (mfERG) was obtained at a single visit.

RESULTS

Mean coefficients of variation for PSV, EDV and MFV were 16.1-19.2% for within-visit measurements and 20.1-22.4% for between-visit measures. Across patients, greater visual function loss assessed with VA (p = 0.04), extinguished versus measurable amplitude in ring 1 for mfERG (p = 0.001), and cone-only versus rod function with the AdaptDx (p = 0.002) were statistically significantly correlated with reduced MFV in the CRA when included a multilevel multivariate regression model along with the qCSF and HVF results, which all together accounted for 47% of the total variance in MFV. GVF log retinal areas (V4e and III4e; p = 0.30 and p = 0.95, respectively) and measurable far peripheral vision during GVF testing (p = 0.66) were not significantly related to MFV.

CONCLUSIONS

MFV in the CRA decreased with impaired central vision due to loss of both rod and cone function, had good test-retest repeatability, and may serve as a biomarker outcome to determine the potential physiological basis for improvements in RP clinical trials of therapies with indirect effects on blood flow to the retina.

The discovery of the Flammer syndrome: a historical and personal perspective

This review describes the clinical and basic research that led to the description of Flammer syndrome. It is narrated from a personal perspective. This research was initiated by the observation of an increased long-term fluctuation of visual fields in a subgroup of glaucoma patients. As these patients had strikingly cold hands, peripheral blood flow was tested with a capillary microscopy, and vasospastic syndrome (VS) was diagnosed. Further studies on these patients revealed frequently weakened autoregulation of ocular blood flow and increased flow resistivity in retroocular vessels. Their retinal vessels were more rigid and irregular and responded less to flickering light. Holistic investigation demonstrated low blood pressure, silent myocardial ischaemia, altered beat-to-beat variation, altered gene expression in the lymphocytes, slightly increased plasma endothelin level and increased systemic oxidative stress. This combination of signs and symptoms was better described by the term primary vascular dysregulation (PVD) than by VS. Subsequent studies showed additional symptoms frequently related to PVD, such as low body mass index, cold extremities combined with slightly increased core temperature, prolonged sleep onset time, reduced feelings of thirst, increased sensitivity to smell and also for certain drugs and increased retinal venous pressure. To better characterise this entire syndrome, the term Flammer syndrome (FS) was introduced. Most subjects with FS were healthy. Nevertheless, FS seemed to increase the risk for certain eye diseases, particularly in younger patients. This included normal-tension glaucoma, anterior ischaemic optic neuropathy, retinal vein occlusions, Susac syndrome and central serous chorioretinopathy. Hereditary diseases, such as Leber’s optic neuropathy or retinitis pigmentosa, were also associated with FS, and FS symptoms and sings occurred more frequent in patients with multiple sclerosis or with acute hearing loss. Further research should lead to a more concise definition of FS, a precise diagnosis and tools for recognizing people at risk for associated diseases. This may ultimately lead to more efficient and more personalised treatment.

[Ocular blood flow and retinal electrogenesis in retinitis pigmentosa]

AIM

to investigate correlations between changes in ocular hemodynamics revealed by color Doppler flow mapping (CDFM) and pulsed-wave (PW) Doppler imaging, one the one hand, and electrical activity of the retina, on the other, in patients with early, moderate, and severe retinitis pigmentosa (RP).

MATERIAL AND METHODS

A total of 20 patients (40 eyes) aged from 16 to 40 years (28.4 ± 8.2 years on average) with retinitis pigmentosa were enrolled. The control group consisted of 20 healthy volunteers of the same age range. All participants underwent full-field electroretinography (ERG), flicker ERG, and macular ERG as well as blood flow assessment in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary arteries (SPCA) by means of CDFM and PW-Doppler.

RESULTS

Ocular blood flow in CRA and SPCA appeared disturbed in patients with early RP. In cases of moderate and severe RP, the peak systolic velocity of CRA and SPCA blood flow was significantly decreased. Systolic and end diastolic blood flow velocities in CRA and SPCA has been shown to be directly related to full-field ERG a-wave and b-wave amplitudes, correspondingly, but negatively correlated with their implicit times.

CONCLUSION

The revealed decrease in CRA and SPCA blood flow indices proves retinal and choroidal circulation deficit in patients with advanced RP. As shown, moderate blood flow changes are already present in early RP and progress as retinal photoreceptors and bipolar cells become suppressed, which may be useful for RP diagnosis and monitoring.

Choroidal Thickness Analysis in Patients with Usher Syndrome Type 2 Using EDI OCT

To portray Usher Syndrome type 2, analyzing choroidal thickness and comparing data reported in published literature on RP and healthy subjects. Methods. 20 eyes of 10 patients with clinical signs and genetic diagnosis of Usher Syndrome type 2. Each patient underwent a complete ophthalmologic examination including Best Corrected Visual Acuity (BCVA), intraocular pressure (IOP), axial length (AL), automated visual field (VF), and EDI OCT. Both retinal and choroidal measures were measured. Statistical analysis was performed to correlate choroidal thickness with age, BCVA, IOP, AL, VF, and RT. Comparison with data about healthy people and nonsyndromic RP patients was performed. Results. Mean subfoveal choroidal thickness (SFCT) was 248.21 ± 79.88 microns. SFCT was statistically significant correlated with age (correlation coefficient -0.7248179, p < 0.01). No statistically significant correlation was found between SFCT and BCVA, IOP, AL, VF, and RT. SFCT was reduced if compared to healthy subjects (p < 0.01). No difference was found when compared to choroidal thickness from nonsyndromic RP patients (p = 0.2138). Conclusions. Our study demonstrated in vivo choroidal thickness reduction in patients with Usher Syndrome type 2. These data are important for the comprehension of mechanisms of disease and for the evaluation of therapeutic approaches.

Measurement of Choroidal Thickness Following Caffeine Intake in Healthy Subjects

PURPOSE

The aim of this study is to investigate the effect of 200 mg caffeine on subfoveal choroidal thickness (CT) in the macular area as measured by enhanced depth imaging optical coherence tomography (EDI-OCT) in healthy subjects.

MATERIALS AND METHODS

Fifty healthy individuals (study group) and 50 healthy individuals (control group) were enrolled in study. In the study group, participants received a 200 mg caffeine capsule and the control group consisted of subjects who received plasebo capsule. The subfoveal CT was measured by EDI-OCT before the caffeine intake and at 30 min, 1 h, 2 h, 3 h, 4 h and 6 h following caffeine intake.

RESULTS

SFCT after caffeine intake was significantly decreased at 30 min, 1 h, 2 h, 3 h and 4 h compared to the baseline measurement, while the difference between baseline and 6 h was not statistically significant in the study group. There were no significant differences between the baseline and the other measurement times in the control group (p > 0.05).

CONCLUSION

The thinning of CT begins about 30 min after the oral ingestion of 200 mg of caffeine and lasts for about four hours.

Prevalence of thrombophilic genetic factors among patients with retinitis pigmentosa

PURPOSE

To determine the prevalence of thrombophilic factors in patients with retinitis pigmentosa (RP).

METHODS

Fifty consecutive patients with RP and 50 controls matched by age and gender were tested for the presence of the following mutations: factor II (GA20210), factor V Leiden (GA1691), methylenetetrahydrofolate reductase (CT677), factor XIIIa (Val→Leu), β-fibrinogen (GA455), tumor necrosis factor receptor (TNFRII) (M196R), plasminogen activator inhibitor-1 (PAI-1) (4 G/5 G), and plasminogen activator inhibitor-1 (PAI-1) (GA844).

RESULTS

The following heterozygous mutations were found in patients/controls: factor V Leiden (12/14), factor XIIIa (20/30), methylenetetrahydrofolate reductase 677 TT (48/52), β-fibrinogen GA455 (36/36), TNFRII (M196R) (40/42), PAI-1 4 G/5 G (40/48), and PAI-1 GA844 (50/52). The difference between patients with RP and the control group was not statistically significant for the prevalence of any of the studied factors (P > 0.05).

CONCLUSION

In this study, thrombophilic mutations were not increased in patients with RP. Thrombophilic mutations do not seem to be risk factors for RP. Routine investigation of hereditary thrombophilia in these patients is not justified.

Association of retinal vessel attenuation with visual function in eyes with retinitis pigmentosa

Purpose

To investigate the association between visual changes and retinal vessel attenuation in patients with retinitis pigmentosa (RP).

Design

A retrospective, longitudinal, observational cohort study.

Methods

We analyzed 45 eyes from 45 subjects who were followed-up for ≥3 years at our clinic. Using the computer-based Interactive Vessel Analysis program, central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were determined. Age- and sex-matched controls from normal subjects were selected from our archived fundus photograph library. Visual acuity, visual field area (Goldmann perimetry, V4e white test light), mean deviation (Humphrey perimetry, central 10-2 program), and central macular thickness (optical coherence tomography) were analyzed for correlations with CRAE and CRVE.

Results

Both CRAE and CRVE were significantly decreased in RP eyes (94.9±13.5 μm and 155.6±20.0 μm, respectively) compared with control eyes (138.1±14.7 μm and 215.0±20.4 μm, respectively, both P<0.001). After 3 years of follow-up, visual field area was associated with both CRAE (r=0.584, P<0.01) and CRVE (r=0.500, P=0.008). A significant association was also observed between mean deviation and CRAE (r=0.298, P=0.047). In eyes with RP, a narrower vessel caliber at baseline was associated with a larger decline in visual acuity over the 3-year follow-up interval (CRAE: r=−0.344, P=0.021; CRVE: r=−0.314, P=0.035).

Conclusion

Retinal vessel caliber is associated with some visual functions in patients with RP.

Retinal vessel oxygen saturation and vessel diameter in retinitis pigmentosa

PURPOSE

To assess retinal vessel oxygen saturation and retinal vessel diameter in retinitis pigmentosa.

METHODS

A retinal oximeter (Oxymap ehf., Reykjavik, Iceland) was used to measure retinal vessel oxygen saturation and vessel diameter in ten patients with retinitis pigmentosa (RP) (mean age 49 years, range 23-71 years). Results were compared with age- and gender-matched healthy individuals. All patients had advanced stage of the disease with visual fields restricted to the macular region.

RESULTS

Oxygen saturation in retinal venules was 58.0 ± 6.2% in patients with RP and 53.4 ± 4.8% in healthy subjects (p = 0.017). Oxygen saturation in retinal arterioles was not significantly different between groups (p = 0.65). The mean diameter of retinal arterioles was 8.9 ± 1.6 pixels in patients with RP and 11.4 ± 1.2 in healthy controls (p < 0.0001). The corresponding diameters for venules were 10.1 ± 1.2 (RP) and 15.3 ± 1.7 (healthy, p < 0.0001).

CONCLUSIONS

Increased venous saturation and decreased retinal vessel diameter suggest decreased oxygen delivery from the retinal circulation in retinitis pigmentosa. This is probably secondary to tissue atrophy and reduced oxygen consumption.

Examining the choroid in ocular inflammation: a focus on enhanced depth imaging

The choroid is the vascular layer that supplies the outer retina and is involved in the pathogenesis of several ocular conditions including choroidal tumors, age related macular degeneration, central serous chorioretinopathy, diabetic retinopathy, and uveitis. Nevertheless, difficulties in the visualization of the choroid have limited our understanding of its exact role in ocular pathology. Enhanced depth imaging optical coherent topography (EDI-OCT) is a novel, noninvasive technique that is used to evaluate choroidal thickness and morphology in these diseases. The technique provides detailed objective in vivo visualization of the choroid and can be used to characterize posterior segment inflammatory disorders, monitor disease activity, and evaluate efficacy of treatment. In this review we summarize the current application of this technique in ocular inflammatory disorders and highlight its utility as an additional tool in monitoring choroidal involvement in ocular inflammation.

Subfoveal choroidal thickness in patients with chronic heart failure analyzed by spectral-domain optical coherence tomography

PURPOSE

To evaluate the subfoveal choroidal thickness (SFCT) measured by enhanced depth imaging optical coherence tomography (EDI-OCT) in eyes of chronic heart failure (CHF) patients.

METHODS

Fifty-six patients with CHF and 56 age- and gender-matched healthy individuals were enrolled. The SFCT was measured by EDI-OCT. The ejection fraction of left ventricle (EFLV), age, intraocular pressure (IOP), axial length (AL), systolic and diastolic blood pressure, and ocular perfusion pressure (OPP) were also measured.

RESULTS

Mean SFCT was 181.2 ± 80.23 μm in the study group and 283.6 ± 52.4 μm in the control group (p = 0.000). There was a statistically significant correlation between the SFCT and each of EFLV and age. SFCT value was not statistically significantly associated with AL, IOP and OPP.

CONCLUSION

Our results suggest that SFCT is lower in eyes of CHF patients compared to age- and gender-matched healthy individuals.

ET-1 plasma levels, choroidal thickness and multifocal electroretinogram in retinitis pigmentosa

AIM

To assess the relationship between both photoreceptor function and choroidal thickness and endothelin-1 (ET-1) plasma levels in patients with early stage retinitis pigmentosa (RP).

MAIN METHODS

We compared 24 RP patients (14 males and 10 females), 25 to 42 years of age (mean age: 34±7 years) with 24 healthy controls (12 males and 12 females) aged between 28 and 45 years (mean 36±6.8 years). All patients underwent visual field test, electroretinogram and multifocal-electroretinogram and choroidal thickness measurement by using spectral domain optical coherence tomography.

KEY FINDINGS

RP patients had a visual acuity of 0.95, a mean defect of the visual field of -7.90±1.75 dB, a pattern standard deviation index of 6.09±4.22 dB and a b-wave ERG amplitude of 45.08±8.24 μV. Notably RP subjects showed significantly increased ET-1 plasma levels and reduced choroidal thickness compared with controls: respectively, 2.143±0.258 pg/ml vs. 1.219±0.236 pg/ml; p<0.002 and 226.75±76.37 μm vs. 303.9±39.87 μm; p<0.03. Spearman's correlation test highlighted that the increase of ET-1 plasma levels was related with the decrease of choroidal thickness (r=-0.702; p<0.023) and the increase of implicit time in both ring 2 (r=-0.669; p<0.034) and ring 3 (r=-0.883; p<0.007) of mfERG.

SIGNIFICANCE

Increased ET-1 plasma levels may play a key role in the impairment of retinal and choroidal blood flow due to the vasoconstriction induced by ET-1. This could lead to worsening of the abiotrophic process of the macular photoreceptors.

Altered antioxidant-oxidant status in the aqueous humor and peripheral blood of patients with retinitis pigmentosa

Retinitis Pigmentosa is a common form of hereditary retinal degeneration constituting the largest Mendelian genetic cause of blindness in the developed world. It has been widely suggested that oxidative stress possibly contributes to its pathogenesis. We measured the levels of total antioxidant capacity, free nitrotyrosine, thiobarbituric acid reactive substances (TBARS) formation, extracellular superoxide dismutase (SOD3) activity, protein, metabolites of the nitric oxide/cyclic GMP pathway, heme oxygenase-I and inducible nitric oxide synthase expression in aqueous humor or/and peripheral blood from fifty-six patients with retinitis pigmentosa and sixty subjects without systemic or ocular oxidative stress-related disease. Multivariate analysis of covariance revealed that retinitis pigmentosa alters ocular antioxidant defence machinery and the redox status in blood. Patients with retinitis pigmentosa present low total antioxidant capacity including reduced SOD3 activity and protein concentration in aqueous humor. Patients also show reduced SOD3 activity, increased TBARS formation and upregulation of the nitric oxide/cyclic GMP pathway in peripheral blood. Together these findings confirmed the hypothesis that patients with retinitis pigmentosa present reduced ocular antioxidant status. Moreover, these patients show changes in some oxidative-nitrosative markers in the peripheral blood. Further studies are needed to clarify the relationship between these peripheral markers and retinitis pigmentosa.

Does fundus fluorescein angiography procedure affect ocular pulse amplitude?

Purpose. This study examines the effects of fundus fluorescein angiography (FFA) procedure on ocular pulse amplitude (OPA) and intraocular pressure (IOP). Materials and Methods. Sixty eyes of 30 nonproliferative diabetic retinopathy patients (15 males, 15 females) were included in this cross-sectional case series. IOP and OPA were measured with the Pascal dynamic contour tonometer before and after 5 minutes of intravenous fluorescein dye injection. Results. Pre-FFA mean OPA value was 3.05 ± 1.36 mmHg and post-FFA mean OPA value was 2.93 ± 1.28 mmHg (P = 0.071). Pre-FFA mean IOP value was 17.97 ± 1.99 mmHg and post-FFA mean IOP value was 17.81 ± 2.22 mmHg (P = 0.407). Conclusion. Although both mean OPA and IOP values were decreased after FFA procedure, the difference was not statistically significant. This clinical trial is registered with Australian New Zealand Clinical Trials Registry number ACTRN12613000433707.

Decreased retinal-choroidal blood flow in retinitis pigmentosa as measured by MRI

PURPOSE

To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP).

METHODS

MRI studies were performed in 6 RP patients (29-67 years) and 5 healthy volunteers (29-64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial spin-labeling technique at 0.5 × 0.8 × 6.0 mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed.

RESULTS

Basal BF in the posterior retinal-choroid was 142 ± 16 ml/100ml/min (or 1.14 ± 0.13 μl/mm(2)/min) in the control group and was 70 ±19 ml/100ml/min (or 0.56 ± 0.15 μl/mm(2)/min) in the RP group. Retinal-choroidal BF was significantly reduced by 52 ± 8 % in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced, and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2).

CONCLUSIONS

This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal-choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.

Topical isopropyl unoprostone for retinitis pigmentosa: microperimetric results of the phase 2 clinical study

Introduction

The purpose of this study was to determine whether topical 0.15% isopropyl unoprostone (IU), a BK-channel activator, could improve or maintain the central retinal sensitivity in patients with middle- to late-stage retinitis pigmentosa (RP). IU was approved for glaucoma and ocular hypertension in 1994. The drug re-profiling strategy is one of the effective ways to develop safe drugs for patients with RP.

Methods

A randomized, double-blind, and placebo-controlled phase II safety/efficacy trial was conducted. One hundred and nine patients with middle- to late-stage RP having a visual acuity of ≥0.5 were studied at six ophthalmological centers in Japan. The treatments of IU/day were divided into three groups: placebo group; two-drop group; and four-drop group for 24 weeks. The primary outcome measure was changes in the retinal sensitivity from baseline in the central 2° determined by MP-1 microperimetry (MP-1, Nidek, Japan). The secondary outcomes were changes in best-correct visual acuity, contrast sensitivity, retinal sensitivity of the central 10° by MP-1, mean deviation (MD) by a Humphrey field analyzer (HFA; Carl Zeiss Meditec, Dublin, CA, USA) 10-2, and the Visual Functioning Questionnaire 25 (VFQ-25) questionnaire scores.

Results

There was a tendency for a dose-dependent responsiveness in retinal sensitivity in the central 2°, MD, and total VFQ-25 score after 24 weeks of IU instillation by a simple linear regression analysis. A stratified analysis showed a significant dose-dependent responsiveness of the 2° central retinal sensitivity in more advanced patients (P = 0.028). The number of patients having a ≥4 dB decrease in the primary outcome measure was significantly fewer in the four-drop group than in the placebo group (P = 0.02). No adverse reactions were observed.

Conclusions

A higher dose of IU can delay progression of the central retinal sensitivity decrease through an improvement of retinal sensitivity.

Blood flow and anatomical MRI in a mouse model of retinitis pigmentosa

This study tested the sensitivity of an arterial spin labeling MRI method to image changes in retinal and choroidal blood flow (BF) and anatomical thickness of the retina in the rd10 mouse model of retinitis pigmentosa. High-resolution (42 × 42 μm) MRI was performed on rd10 mice and age-matched controls at 25, 35, and 60 days of age (n = 6 each group) on a 7-T scanner. Anatomical MRI was acquired, and quantitative BF was imaged using arterial spin labeling MRI with a separate cardiac labeling coil. Histology was obtained to confirm thickness changes in the retina. In control mice, the retinal and choroidal vascular layers were quantitatively resolved. In rd10 mice, retinal BF decreased progressively over time, while choroidal BF was unchanged. The rd10 retina became progressively thinner at later time points compared with age-matched controls by anatomical MRI and histology (P < 0.01). BF and anatomical MRI were capable of detecting decreased BF and thickness in the rd10 mouse retina. Because BF is tightly coupled to metabolic function, BF MRI has the potential to noninvasively assess retinal diseases in which metabolism and function are perturbed and to evaluate novel treatments, complementing existing retinal imaging techniques.

The ocular pulse amplitude at different intraocular pressure: a prospective study

PURPOSE

To investigate changes in ocular pulse amplitude (OPA) during a short-term increase in intraocular pressure (IOP) and to assess possible influences of biometrical properties of the eye, including central corneal thickness (CCT) and axial length.

METHODS

In a prospective, single centre study, OPA and IOP as measured by dynamic contour tonometry (DCT) were taken before baseline- and post-OPA (delta) intravitreal injection of 0.05 ml anti-vascular endothelial growth factor agents. Analysis was performed employing linear regression with baseline- and post (delta)-OPA differences as the dependent and post-IOP as well as delta IOP as the independent variable. A multilinear regression analysis with delta OPA as the dependent variable and baseline IOP, post-IOP, CCT and axial length as independent variables was conducted.

RESULTS

Forty eyes of 40 patients were included. IOP and OPA increased significantly after injection (IOP mean increase ± SD: 17.83 ± 9.83 mmHg, p < 0.001; OPA mean increase ± SD: 1.39 ± 1.16 mmHg, p < 0.001). For every mmHg increase in IOP, the OPA showed a linear increase of 0.05 mmHg (slope 0.05, 95% CI: 0.02-0.09, p = 0.003, r(2) = 0.20). Multiple regression analysis with delta OPA as the dependent variable revealed a partial correlation coefficient of 0.47 (p = 0.003) for post-IOP as the only significant contribution.

CONCLUSION

A clear positive relationship between OPA measurements and IOP levels was shown in a clinical routine setting using DCT focusing on baseline and postinterventional comparisons of OPA values after intravitreal injections in patients with exudative age related macular degeneration. When considering the OPA for diagnostic purposes, we recommend indication of corresponding IOP values.

Ocular pulse amplitude and associated glaucomatous risk factors in a healthy Hispanic population

BACKGROUND

With increasing evidence that vascular risk factors play a role in the development of glaucoma, it is critical to be familiar with factors related to intraocular blood flow, such as the ocular pulse amplitude (OPA). This study evaluates OPA and factors related to it in a healthy, Hispanic population.

METHODS

Refractive error, corneal curvature, Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT), OPA, axial length, and central corneal thickness (CCT) measurements were obtained on 104 Hispanic subjects recruited from the community.

RESULTS

OPA ranged from 0.7 to 4.7 mmHg (mean, 2.1 +/- 0.8 mmHg) and showed a significant correlation with refractive error, axial length, GAT, and DCT (r=0.250, -0.358, 0.460, 0.378; P=0.011, <0.001, <0.001, and <0.001, respectively). Mean intraocular pressure with GAT was 15.6 mmHg. Mean CCT was 541.2 microm. The average refractive error was 0.75 diopters (D) of myopia, with 25% having >1.00 D myopia.

CONCLUSION

Normal OPA values have not been studied in Hispanic populations. OPA is thought to provide information regarding ocular blood flow; however, more studies are needed to determine its significance in glaucoma treatment.

Low levels of plasma endothelin-1 in patients with retinitis pigmentosa

Purpose:

The aim of this study was to elucidate the role of endothelin-1 (ET-1) in the pathophysiology of retinitis pigmentosa (RP).

Methods:

Plasma ET-1 levels and ophthalmic features in 50 RP patients were compared with those in 20 healthy-eye control subjects. Plasma ET-1 concentrations were determined using a commercially available enzyme-linked immunosorbent assay kit.

Results:

Mean plasma ET-1 levels of RP patients (1.88 ± 0.56 pg/mL) were significantly lower than those of control subjects (2.30 ± 0.30 pg/mL, Mann-Whitney’s U test; P < 0.01). However, ET-1 concentrations varied markedly in each patient. Among RP patients, a significant correlation of ET-1 concentrations was not observed in terms of its hereditary forms or other clinical factors.

Conclusion:

ET-1 may be important in the pathogenesis of RP, and measurement of its plasma concentrations may also contribute to additional insights into the retinal hemodynamics of RP.

Comparison of dynamic contour tonometry and Goldmann applanation tonometry and their relationship to corneal properties, refractive error, and ocular pulse amplitude

BACKGROUND

Accurate intraocular pressure (IOP) measurement is essential in diagnosing and managing glaucoma. Dynamic contour tonometry (DCT) is less dependent on corneal properties, such as thickness, elasticity, and rigidity, than Goldmann applanation tonometry (GAT). This study examined the relationship between GAT and DCT as well as their relationship with corneal properties and ocular pulse amplitude (OPA).

METHODS

GAT, DCT, OPA, pachymetry, refractive error, and corneal curvature measurements were obtained on 115 healthy volunteers.

RESULTS

Participants with thicker corneas (>or=580 microm) had higher IOP measurements with GAT than DCT (P = 0.005). Those with thinner corneas (<or=520 microm) had lower IOP with GAT versus DCT (P = 0.008). GAT and DCT readings did not differ significantly in corneas with average thickness (521 to 579 microm). A clinically significant IOP difference between DCT and GAT was found in 18.2% of subjects. A correlation was found between OPA and both refractive error and IOP (R(2) = .343, P < 0.0001). OPA was higher with increased IOP and decreased myopia.

CONCLUSION

DCT provides IOP measurements that are less dependent on corneal factors than GAT, aiding in diagnosis and treatment of patients with ocular hypertension and glaucoma. Additional studies are necessary to examine the relationship between OPA, refractive error, and IOP and its possible association with increased incidence of glaucoma in myopic patients.

The clinical utility of dynamic contour tonometry and ocular pulse amplitude

PURPOSE

To determine if ocular pulse amplitude (OPA) as measured by dynamic contour tonometry (DCT) is related to severity of glaucoma, and if intraocular pressure (IOP) as measured by DCT is related to central corneal thickness (CCT).

METHODS

Patients were selected from the Duke Eye Center glaucoma clinic. Fifty-five eyes of 32 patients were included; right and left eyes were analyzed separately. CCT, OPA, DCT IOP, Goldmann applanation tonometry (GAT), Tonopen applanation tonometry (TAT), and systemic blood pressure were measured. Advanced Glaucoma Intervention Study score and mean deviation of visual field, and vertical and horizontal cup-disc ratios were recorded in a masked manner. Descriptive statistics were obtained, and OPA, DCT IOP, GAT, and TAT underwent univariate analyses to assess for relationships with predictor variables.

RESULTS

OPA, DCT IOP, GAT, and TAT were positively associated with CCT and with having no surgical intervention for right and left eyes, and were negatively associated with vertical and horizontal cup-disc ratios.

CONCLUSIONS

Increased OPA seems to correlate with less severe glaucoma and with increased CCT. DCT IOP seems to be affected by CCT along with GAT and TAT.

Physiological diurnal variability and characteristics of the ocular pulse amplitude (OPA) with the dynamic contour tonometer (DCT-Pascal)

PURPOSE

The Pascal dynamic contour tonometer (DCT) allows measurement of intraocular pressure (IOP) independently of corneal properties. It records, simultaneously, haemodynamic IOP fluctuations and the difference between the systolic and the diastolic IOP corresponding to the ocular pulse amplitude (OPA). The OPA indirectly reflects choroidal perfusion and could be considered as an independent risk factor in glaucoma. We aimed to establish the physiological diurnal variability of the OPA and its correlations with other biophysical parameters because its characteristics remain partly unclear.

METHOD

Prospective study including 52 eyes of 28 normal subjects with Goldmann applanation tonometry (GAT) IOPs < 22 mmHg. Subjects treated with systemic medications that could interfere with blood pressure or heart rate were excluded. IOP was measured at 9:00 am, 1:00 pm, and 4:00 pm by GAT and DCT. Two consecutive GAT followed by three consecutive DCT measurements were performed in each session by the same clinician (SP). Only DCT measurements with quality 1 and 2 were taken into account. Blood pressure, pulse rate, and central corneal thickness (CCT) were recorded after the last IOP measurements. Spearman correlation coefficient was used for assessment of correlations.

RESULTS

Mean age was 40 +/- 14 years. Mean DCT values were significantly higher than GAT readings (mean = 16.8 +/- 2.0 vs. 15.2 +/- 2.8 mmHg, P < 0.02). The mean OPA was 2.2 +/- 0.7 mmHg (range: 1-3.4 mmHg). The mean amplitude of diurnal OPA fluctuations was 0.4 mmHg. There was no significant difference in the mean OPA values at each time of the diurnal curve. The intraclass correlation (ICC) of only one OPA measurement in relation to part of total variance due to inter-measurement variation was 78%. Averaging over three independent readings of OPA improved ICC to 91%. The OPA was correlated with GAT (r = 0.31, P < 0.0001) and DCT IOP measurements (r = 0.49, P < 0.0001). It was correlated neither with blood pressure nor with age. OPA values of both eyes of the same individual were highly correlated (r = 0.89, P < 0.0001).

CONCLUSION

In normal healthy eyes, the ocular pulse amplitude remains stable during normal outpatient office hours and was not correlated with blood pressure or age of patients.

Évaluation clinique du tonomètre dynamique de contour Pascal®

PURPOSE

The Pascal dynamic contour tonometer (DCT) was designed to measure IOP independently of corneal properties. This study aimed at 1) assessing the intra- and interindividual variability of DCT IOP measurements, the differences between DCT and applanation tonometry IOP measurements (APL), and their correlations with central corneal thickness (CCT); 2) analyzing the variability of the ocular pulse amplitude (OPA) and its correlations with age, blood pressure (BP), cardiac beat pulse (CP), diagnosis of glaucoma, IOP, and severity of glaucomatous visual field (VF) defects.

METHODS

Twenty-five normal subjects (25 eyes), 14 patients with ocular hypertension (27 eyes), and 54 glaucomatous patients (104 eyes) were included in this prospective study. In the first 12 normal subjects, three consecutive IOP measurements were taken by three different observers using DCT, directly followed by three measurements with APL by the same observer. In the following 13 subjects, the reverse sequence was followed. In the other group, the IOP measurements (three DCT and three APLs) were taken by the same observer. Only DCT measurements with quality levels 1-3 were considered for analysis.

RESULTS

In the normal group, DCT IOP measurement variability varied between 4.4%-7.3% (intraobserver variation coefficient) and 8% (interobserver variation coefficient). DCT IOP measurement was not influenced by the sequence of measurements or the observer. DCT overestimated IOP by a mean of 2.2 mmHg compared with APL (p<0.001). The 95% limits of agreement for each subject tested with both tonometers ranged from -0.5 mmHg to +6.3 mmHg. IOP APL and DCT measurements were strongly correlated. Both DCT and APL were not correlated with CCT. OPA ranged from 1.2 mmHg to 6.6 mmHg (mean, 3.1+/-1.2 mmHg) and was comparable between the three observers. Intraobserver OPA variability ranged from 7.6% to 9.5%. The interobserver OPA variability coefficient was 8.8%. OPA was only correlated with systolic BP (p<0.05). In glaucomatous patients, the correlation between DCT and APL IOP measurements was highly significant (r=0.860, p<0.001). DCT overestimated IOP by a mean 2 mmHg compared with APL (p<0.001). IOP differences between both tonometers were not influenced by the sequence of measurements. Unlike APL, DCT was not or only slightly influenced by CCT (p=0.07 for DCT; p=0.001 for APL). The mean difference between IOP DCT and APL was larger in thin corneas (<520 microm): 2.8+/-3.1 mmHg versus 0.8+/-2.3 mmHg in thick corneas (580 microm) (p=0.001). OPA was not correlated with age. It was positively correlated with IOP (p<0.001), systolic BP (p=0.047), and MD (mean deviation) (p=0.018). It was negatively correlated with diastolic BP (p=0.003), cardiac frequency (p<0.001), severity of glaucomatous VF defects (p=0.002), and PSD (pattern standard deviation) (p=0.008). It was significantly higher in the OHT subgroup and significantly lower in the NTG subgroup (p<0.05). In both groups, the IOP difference between DCT and APL was not correlated with age (p>0.05).

CONCLUSIONS

IOP measurements with the Pascal(R) DCT and APL correlated well and were reproducible. DCT IOP measurement variability was slightly higher than APL with relatively wide 95% limits of agreement. Considering the entire study population, DCT overestimated IOP by a mean 2.0 mmHg compared with APL. DCT was independent of CCT, especially in thin corneas. The DCT does not appear to be clinically advantageous over the Goldmann tonometer in the IOP measurement in thick corneas. Therefore an IOP follow-up by APL tonometry and pachymetry appeared to be mandatory for the interpretation of the true IOP. Interindividual OPA variations were high, as was measurement variability. OPA was correlated with BP, cardiac frequency, IOP, diagnosis of glaucoma, and severity of glaucomatous VF defects. These must be considered in the clinical interpretation of this parameter.

Dynamic contour tonometry: principle and use

Interindividual variability of central corneal thickness has been found to be a source of error for conventional Goldmann applanation tonometry. The dynamic contour tonometer represents a potentially new technology for non-invasive and direct intraocular pressure (IOP) measurement, and has been proposed to accurately measure the true IOP irrespective of the corneal thickness. It is based on the principle that when the tip of the device exactly matches the contour of the cornea, the pressure measured by a transducer placed on its tip is an accurate indicator of the true IOP. This device is also capable of measuring the ocular pulse amplitude, a variable that has controversial significance in the diagnosis and management of glaucoma. Even though this technique seems to be very promising, further studies are required to conclusively determine the effectiveness of the dynamic contour tonometer in patients having an abnormal or irregular corneal contour.

Intraocular pressure and ocular pulse amplitude comparisons in different types of glaucoma using dynamic contour tonometry

PURPOSE

To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPA) in patients with different types of glaucoma, ocular hypertension (OHT), and normal controls (NC) using dynamic contour tonometry (DCT) and the goldmann applanation tonometry (GAT).

METHODS

906 eyes of 501 adult patients in the following five groups were included in this cross-sectional study: primary open angle glaucoma (POAG), normal tension glaucoma (NTG), Pseudoexfoliative Glaucoma (PXG), OHT, and NC. The following tests were performed simultaneously during a single visit: IOP using DCT and GAT; OPA using DCT and central corneal thickness (CCT) using ultrasound pachymetry. Mixed effects regression models were used to compare the DCT and GAT IOP measurements in the five groups; the effect of CCT on IOP and the relationship between OPA and IOP within each group.

RESULTS

DCT consistently had higher IOP values than GAT in POAG, PXG, NTG, and controls (p < 0.001) but not in OHT (p = 0.84). DCT IOP did not change while GAT IOP showed a non-significant increase (p = 0.09) with increased corneal thickness in each group. OPA was found to be highest in OHT (3.61 mmHg) and lowest in the control group (2.86 mmHg) and significantly increased with IOP in all groups.

CONCLUSIONS

DCT measures an IOP that is significantly higher than GAT IOP in glaucoma and control subjects but not in ocular hypertensives. Furthermore, the DCT may measure an IOP that is independent of the CCT, which may not be true for the GAT, which increases with the CCT. OPA was highest in OHT and may be affected by the IOP.

Intraocular pressure and ocular pulse amplitude using dynamic contour tonometry and contact lens tonometry

BACKGROUND

The new Ocular Dynamic Contour Tonometer (DCT), investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland) allows simultaneous recording of intraocular pressure (IOP) and ocular pulse amplitude (OPA). It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens,a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland).

METHODS

Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens, and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens.

RESULTS

No difference (P = 0.09) was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg) and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +/- 4.03 mm Hg). The IOP values of SmartLens (mean: 20.25 mm Hg, median: 19.00 mm Hg, SD: +/- 4.96 mm Hg) were significantly higher (P = 0.0008) both from Goldmann tonometry and DCT. The OPA values of the DCT (mean: 3.08 mm Hg, SD: +/- 0.92 mm Hg) were significantly lower (P = 0.0003) than those obtained by SmartLens (mean: 3.92 mm Hg, SD: +/- 0.83 mm Hg).

CONCLUSIONS

DCT was equivalent to Goldmann applanation tonometry in measurement of IOP in a small group of normal subjects. In contrast, SmartLens (contact lens tonometry) gave IOP readings that were significantly higher compared with Goldmann applanation tonometer readings. Both devices, DCT and SmartLens provide the measurement of OPA which could be helpful e.g. for the management of glaucoma.

Unrecordable pulsatile ocular blood flow may signify severe stenosis of the ipsilateral internal carotid artery

AIM

To examine the relation between stenosis of the internal carotid artery (ICA) and pulsatile ocular blood flow (POBF).

METHODS

In 57 eyes of 30 patients who were referred for Doppler ultrasound examination of the ICA we measured POBF and analysed the correlation with degree of ipsilateral ICA stenosis.

RESULTS

There was a significant negative correlation between POBF and ipsilateral ICA stenosis (Pearson correlation coefficient, r=-0.516, p<0.0001). In 14 eyes POBF could not be measured by the OBF tonometer, and in 11 of these cases (79%) severe stenosis (>75%) of the ipsilateral ICA was present. When these eyes were excluded from analysis, there was no correlation between POBF and ICA stenosis (r=-0.02, p=0.91). Among these 43 eyes in which POBF could be measured it ranged 667-2095 microl/min with a mean of 970.72 microl/min.

CONCLUSION

Low or unrecordable POBF may signify severe stenosis of the internal carotid artery. POBF is not a direct reflection of ipsilateral ICA blood flow.

The impact of ocular blood flow in glaucoma

Two principal theories for the pathogenesis of glaucomatous optic neuropathy (GON) have been described--a mechanical and a vascular theory. Both have been defended by various research groups over the past 150 years. According to the mechanical theory, increased intraocular pressure (IOP) causes stretching of the laminar beams and damage to retinal ganglion cell axons. The vascular theory of glaucoma considers GON as a consequence of insufficient blood supply due to either increased IOP or other risk factors reducing ocular blood flow (OBF). A number of conditions such as congenital glaucoma, angle-closure glaucoma or secondary glaucomas clearly show that increased IOP is sufficient to lead to GON. However, a number of observations such as the existence of normal-tension glaucoma cannot be satisfactorily explained by a pressure theory alone. Indeed, the vast majority of published studies dealing with blood flow report a reduced ocular perfusion in glaucoma patients compared with normal subjects. The fact that the reduction of OBF often precedes the damage and blood flow can also be reduced in other parts of the body of glaucoma patients, indicate that the hemodynamic alterations may at least partially be primary. The major cause of this reduction is not atherosclerosis, but rather a vascular dysregulation, leading to both low perfusion pressure and insufficient autoregulation. This in turn may lead to unstable ocular perfusion and thereby to ischemia and reperfusion damage. This review discusses the potential role of OBF in glaucoma and how a disturbance of OBF could increase the optic nerve's sensitivity to IOP.