[Diagnostics and therapy for normal tension glaucoma]

Pooled data from "The Baltimore Eye Survey", "The Blue Mountains Eye Study", "The Beaver Dam Eye Study", "The Rotterdam Study" and "The Melbourne VIP" showed a strong age-dependent prevalence of open angle glaucoma. Patients younger than 60 years have a prevalence of open angle glaucoma of less than 1 %. Beginning with the age of 60 the prevalence increases exponentially. The prevalence of open angle glaucoma in persons in the 8(th) age decade reaches up to 5 %. Among these patients, 30-50 % have normal intraocular pressure. The diagnostics and therapy for open angle glaucoma with normal intraocular pressure (IOP), also called normal tension glaucoma, is a complex and often interdisciplinary challenge. Established causative factors for developing a glaucomatous optic nerve atrophy in normal tension glaucoma are: relatively increased IOP, older age, non-dippers (0-10 %) or extreme dippers (> 20 %) concerning nocturnal arterial blood pressure drop, small vessel disease with cardiovascular disease and cerebral microgliosis (white matter lesions), decreased blood flow in the optic nerve head, extreme dip of the optic nerve head blood flow in the morning, cerebral blood flow dysregulation and the epsilon4-allele polymorphism of the apolipoprotein E-gene. Clinical pathways are presented for the diagnostics and therapy for normal tension glaucoma.

[TalkingEyes-and-more]

To avoid the clinical manifestation of a vascular disease like stroke it is necessary to detect early vascular signs, to begin a therapy before the outbreak of the vascular disease happens. "TalkingEyes-and-more" is an interdisciplinary and quality-assessed program for prevention of vascular diseases. In several "screening-centers" in Germany interested citized were examined by non-invasive and fast methods to estimate the vascular risk. The examinations were performed on site, the medical evaluation of the data and images were performed centrally in the reading center of the Private Center of Preventive Medicine and Eye Diagnostics" in Erlangen by medical doctors. Alterations of the microvessels become often at first visible in retinal vessels. "TalkingEyes-and-more" examined telemedically the retinal vessels by a patented approach regarding microangiopathic abnormalities. In addition other risk factors like arterial blood pressure, intima media thickness of the carotid artery, cholesterol, fasting glucose, extended bodymass index, and others were documented. By these data a risk index is calculated and a proposal for improving the risk factors is generated.

Automated segmentation of the optic nerve head for diagnosis of glaucoma

Glaucoma is the second most common cause of blindness worldwide. Low awareness and high costs connected to glaucoma are reasons to improve methods of screening and therapy. A well-established method for diagnosis of glaucoma is the examination of the optic nerve head using scanning-laser-tomography. This system acquires and analyzes the surface topography of the optic nerve head. The analysis that leads to a diagnosis of the disease depends on prior manual outlining of the optic nerve head by an experienced ophthalmologist. Our contribution presents a method for optic nerve head segmentation and its validation. The method is based on morphological operations, Hough transform, and an anchored active contour model. The results were validated by comparing the performance of different classifiers on data from a case-control study with contours of the optic nerve head manually outlined by an experienced ophthalmologist. We achieved the following results with respect to glaucoma diagnosis: linear discriminant analysis with 27.7% estimated error rate for automated segmentation (aut) and 26.8% estimated error rate for manual segmentation (man), classification trees with 25.2% (aut) and 22.0% (man) and bootstrap aggregation with 22.2% (aut) and 13.4% (man). It could thus be shown that our approach is suitable for automated diagnosis and screening of glaucoma.

Telemedizinisch unterstütztes Screening der retinalen Gefäße („Talking Eyes”)

BACKGROUND

Cerebral and retinal vessels behave similarly under the influence of vascular risk factors. Several groups have shown that retinal microvascular abnormalities represent an independent risk factor with regard to strokes and heart attacks.

AIM OF THE STUDY

The aim of this study was to perform a prospective screening examination with regard to retinal microvascular abnormalities as well as an extended vessel diagnosis in a subgroup of patients with lower arteriovenous risk values.

METHODS

In the course of a prospective cross-sectional study ("Talking Eyes") between 1.9.2001 and 1.8.2002 a telemedical-supported screening of the retina (study I) was carried out in 7,163 subjects. The patients were selected without any inclusion or exclusion criteria. The mean age was 48.2 +/- 8 years (18 - 83 years) with a sex distribution of 39.2 % females to 60.8 % males. Digital fundus photos of the right and left eyes were taken for all patients. The pictures were taken without pupil dilation using a CANON-NM camera. The pictures and case histories were stored in a central server using web-based software (MedStage, Siemens). In a central reading centre, the arteriovenous ratio of both eyes was determined telemedically using the Parr-Hubbard formula and the retinas subjected to a standardised examination by an ophthalmologist. The retinal risk factor was calculated on the basis of the arteriovenous ration, the presence of microvascular abnormalities and the case history. The reproducibility of measurement of the arteriovenous ratio (Kronbach alpha coefficient) was evaluated by double measurements on 1,332 images. In a subgroup of study I with arteriovenous ratio values < 0.76 (N = 107), an extended vessel diagnosis with measurement of 24-h blood pressure and vessel-relevant blood values (homocysteine, cholesterol, LDL, HDL, CRP, TG, HbA1c) was carried out (study II).

RESULTS

Study I: The Kronbach alpha coefficient as a measure of reproducibility amounted to 0.77. The mean arteriovenous ratio of the retinal vessels was 0.83 +/- 0.09 and showed a pronounced age dependence (R = 0.9, p < 0.0001). On multivariate testing the arteriovenous ratio correlated significantly (R = 0.33, p < 0.001) with the factors age, systolic blood pressure, diastolic blood pressure and body mass index. Diastolic blood pressure followed by age had the largest influence. The prevalence of microvascular abnormalities in the right (RE) and left (LE) eyes, respectively were: cotton wool foci RE 0.0015 %, LE 0.003 %, retinal haemorrhage RE 0.1 %, LE 0.1 %, focal stenoses RE 3.4 %, LE 3.4 %, tortuositas vasorum RE 4.1 %, LE 4.0 %, arteriovenous crossing signs RE 11.2 %, LE 11.2 %. On multivariate testing the occurrence of microvascular abnormalities correlated significantly (R = 0.38, p < 0.001) with the factors high blood pressure known from case history, body mass index, and gender. Arterial hypertension had the strongest influence followed by diastolic blood pressure. The calculated retinal risk factor correlated with the prevalence of angina pectoris. Study II: 2/3 of the subjects with arteriovenous risk factor values < 0.76 exhibited pathologically high 24-h blood pressure values. For these patients there were significant correlations between the arteriovenous ratio and the low-density lipoprotein concentration as well as the Framingham risk score.

CONCLUSION

In the course of a prospective, telemedical-supported screening examination of the retinal vessels of more than 7,000 subjects the arteriovenous ratio exhibited a strong dependence on age and blood pressure. Among the subjects with lowered arteriovenous ratio values, 2/3 exhibited arterial hypertension in the 24-h blood pressure determination.

Telematisch assistierte Selbsttonometrie (TAS)

BACKGROUND

Close supervision of intraocular pressure (IOP) means monitoring an important risk factor for glaucoma.

METHOD

After instruction in its use, patients measure their own IOP several times a day with the Drager self-tonometer. The measurements are subsequently transmitted to a server via the telephone keypad and recorded separately for each patient. The software enables statistical evaluation of the pressure levels collected.

RESULTS

Up to now 30 of 35 patients transmit measurements or had done so for at least 6 months. Registration of measurement levels covering months and years provides the opportunity for optimizing treatment and hence can be considered a start toward quality assurance in the treatment of glaucoma patients.

CONCLUSION

TAS is a cost-efficient method for obtaining long-term profiles of eye pressure. Thus, the possibility exists for early therapeutic intervention in patients at risk. The compliance gained by the close relationship between the physician and the patient represents a positive prognostic factor.

Multimodal retinal image registration for optic disk segmentation

OBJECTIVES

The analysis of the optic disk morphology with the means of the scanning laser tomography is an important step for glaucoma diagnosis. A method we developed for optic disk segmentation in images of the scanning laser tomograph is limited by noise, non-uniform illumination and presence of blood vessels. Inspired by recent medical research, we wanted to develop a tool for improving optic disk segmentation by registration of images of the scanning laser tomograph and color fundus photographs and by applying a method we developed for optic disk segmentation in color fundus photographs.

METHODS

The segmentation of the optic disk for glaucoma diagnosis in images of the scanning laser tomograph is based on morphological operations, detection of anatomical structures and active contours and has been described in a previous paper. The segmentation of the optic disk in the fundus photographs is based on nonlinear filtering, Canny edge detector and a modified Hough transform. The registration is based on mutual information using simulated annealing for finding maxima.

RESULTS

The registration was successful 86.8% of the time when tested on 174 images. Results of the registration have shown a very low displacement error of a maximum of about 5 pixels. The correctness of the registration was manually evaluated by measuring distances between the real vessel borders and those from the registered image.

CONCLUSIONS

We have developed a method for the registration of images of the scanning laser tomograph and fundus photographs. Our first experiments showed that the optic disk segmentation could be improved by fused information from both image modalities.

Diagnosis of glaucoma by indirect classifiers

OBJECTIVES

Demonstration of the applicability of a framework called indirect classification to the example of glaucoma classification. Indirect classification combines medical a priori knowledge and statistical classification methods. The method is compared to direct classification approaches with respect to the estimated misclassification error.

METHODS

Indirect classification is applied using classification trees and the diagnosis of glaucoma. Misclassification errors are reduced by bootstrap aggregation. As direct classification methods linear discriminant analysis, classification trees and bootstrap aggregated classification trees are utilized in the problem of glaucoma diagnosis. Misclassification rates are estimated via 10-fold cross-validation.

RESULTS

Indirect classification techniques reduce the misclassification error in the context of glaucoma classification compared to direct classification methods.

CONCLUSIONS

Embedding a priori knowledge into statistical classification techniques can improve misclassification results. Indirect classification offers a framework to realize this combination.

Functional imaging of the retinal microvasculature by scanning laser Doppler flowmetry

PURPOSE

to image functionally perfused retinal vessels and to assess quantitatively the intercapillary space of the retinal microvasculature.

METHOD

The base of functional imaging and the quantitative assessment of the retinal vasculature is the two-dimensional map of the retina encoded by the laser Doppler frequency shift. By Scanning Laser Doppler Flowmetry (HRF. Heidelberg Engineering) the laser Doppler frequency shift of 16.384 retinal sites (256 pixels x 64 lines, spatial resolution 10 mum) of a retinal area of 2.7 x 0.7 mm was gained. The image processing was performed by a recently described algorithm (AFFPIA). Using the data of the laser Doppler frequency shift of every retinal site, a color-coded retinal image was established showing perfused vessels and capillaries. By automatic pattern analysis of this image vessels and capillaries were identified and segmented. Based on this image the distances in [microm] of every retinal site to the next vessel or capillary were calculated ("distance to next capillary"). The functional imaging of the retinal perfusion was demonstrated in (1) normal retina, (2) retinal arterial occlusion, and (3) proliferative retinopathy. Intraobserver reliability of the quantitative assessment of the parameter "distance to next capillary" was estimated by measuring 10 eyes of 10 subjects at 5 different days by one observer. Interobserver reliability of the quantitative assessment was evaluated by analysing 10 perfusion maps by 5 different operators. In 93 eyes of 71 normal subjects (mean age 40.4 mu 15 years) the juxtapapillary retina was quantitatively evaluated.

RESULTS

QUALITATIVE EVALUATION: The functional images of the retinal perfusion of eyes with normal retina, with retinal arterial occlusion, and with proliferative retinopathy corresponded well with the fluorescein angiography. Perfused vessels and capillaries became visible in a high local resolution. QUANTITITATIVE ASSESSMENT: The coefficient of reliability of the introobserver and interobserver reproducibility of the parameter 'mean distance to next capillary" was 0.74, and 0.95, respectively. The quantitative assessment of the perfusion showed that the major part of the retinal sites (>700%) had distances to the next capillary lower than 30 microm 46% of the retinal area had distances to the next capillary from 0-20 microm 26% of the retina had distances from 20-30 microm, 12% of the retina had distances from 30-40 microm 7% of the retina had distances from 40-50 microm, 4% of the retina had distances from 50-60 microm, and 4% of the retinal sites showed distances to the next capillary greater than 60 mum. The mean distance to the next capillary or vessel was calculated with 21 +/- 6.5 microm.

CONCLUSION

By non-invasive Scanning Laser Doppler Flowmetry in combination with adequate software it is possible to perform a functional imaging of the retinal vasculature and to measure all index for the functional density of retinal capillaries and vessels.

Retinal microcirculation correlates with ocular wall thickness, axial eye length, and refraction in glaucoma patients

PURPOSE

To examine the correlations of refraction, axial eye length, and posterior eye wall thickness with retinal microcirculation.

PATIENTS AND METHODS

In a prospective study, 25 patients with primary open-angle glaucoma, 12 patients with ocular hypertension, and 12 healthy subjects were examined; only one eye of each participant was considered in the analysis. Posterior eye wall thickness and axial eye length were measured with standardized A-scan ultrasonography. Retinal microcirculation temporal to the optic disc was determined by a scanning laser Doppler flowmeter using automatic full-field perfusion image analyzer software.

RESULTS

In glaucoma patients, temporal retinal mean flow exhibited significant correlation to the eye wall thickness (r = 0.470, P = 0.042), axial eye length (r = -0.570, P = 0.011), and refraction of the eye (r = 0.520, P = 0.022). In glaucomatous eyes, the temporal retinal mean flow was significantly lower than in healthy subjects or in ocular hypertensive patients (P = 0.01).

CONCLUSIONS

Myopic eyes have longer axial eye length and thinner ocular wall than emmetropic eyes. In glaucoma patients, the longer the axial eye length and the thinner the ocular wall, the more reduced the retinal microcirculation. The reduced microcirculation found in myopic glaucomatous eyes might contribute to the development of glaucomatous damage in these eyes.

Changes in ocular blood flow velocities during external counterpulsation in healthy volunteers and patients with atherosclerosis

BACKGROUND

External counterpulsation (ECP) is a new noninvasive means of augmenting organ perfusion by applying ECG-triggered diastolic pressure to the vascular bed of the lower limbs. In this study, effects of ECP on changes of ocular blood flow velocities were studied.

METHOD

Mean, systolic and diastolic flow velocities of the ophthalmic artery were measured by Doppler sonography before and during ECP. Twelve healthy volunteers (age 31.3+/-4.3 years) and 12 patients with severe atherosclerosis (inclusion criteria: two atherosclerotic risk factors, at least one severe coronary stenosis, age 62.1+/-5.3 years) were included in the study.

RESULTS

In healthy subjects, ECP changed diastolic flow velocity of the ophthalmic artery nonsignificantly from 21.6+/-7.7 to 23.7+/-10.5 cm/s. Systolic flow velocity decreased significantly from 36.1+/-13.6 to 28.9+/-10.2 cm/s (P<0.01). Mean flow velocity changed nonsignificantly from 28.1+/-9.4 to 26.5+/-9.9 cm/s. In atherosclerotic patients, mean flow velocity increased significantly from 26.3+/-11.4 to 29.3+/-11.2 cm/s (P<0.001), which was caused by significant diastolic flow augmentation from 19.7+/-9.1 to 23.9+/-9.7 cm/s (P<0.001). Systolic flow velocity was not changed significantly (from 34.2+/-12.8 to 32.6+/-11.8 cm/s).

CONCLUSION

No significant change of mean blood flow velocity in the ophthalmic artery was found in young healthy subjects. In elderly patients with atherosclerosis, ECP significantly increased blood flow velocity in the ophthalmic artery by 11.4%. This may indicate an ocular perfusion benefit in these patients as a result of ECP and could also explain the increase of perfusion found in patients with retinal ischemia after ECP.

Screening models for glaucoma

For social and economic reasons, glaucoma screening is a useful and necessary task, with possible benefits for individuals and the health care system arising from the early diagnosis and early therapy of patients with glaucoma. Early treatment of patients with glaucoma decreases the probability that those patients will become blind and lowers the direct and indirect costs for patients with glaucoma. Most of the reported studies dealing with glaucoma screening used only one parameter (eg, intraocular pressure) to detect and to discriminate glaucoma patients from healthy subjects. Glaucoma screening devices might be combined to obtain the best specificity and sensitivity. Because the diagnosis of glaucoma is very closely associated with a morphologic change in the optic nerve head, one screening parameter should be the morphology of the papilla. To increase specificity and sensitivity, a combination of morphologic and functional testing might be useful. In this review, we report the context of glaucoma screening in terms of health economics, the testing quality of devices for functional and morphologic screening, and the results of a pilot study.

Telemedicine in the control of intra-ocular pressure

Glaucoma is one of the most common causes of blindness in the Western world and a major risk factor is increased intra-ocular pressure. We therefore used telemedicine in its control. Patients measured their intra-ocular pressure several times a day with a portable instrument and the values were then entered into a portable digital assistant. These data were transmitted by a modem to a central server. If the intra-ocular pressure was pathologically high, an email message was automatically sent to the ophthalmologist. The pressure curve, including a statistical analysis, was displayed in an easily readable chart format. Ten patients with glaucoma participated in a trial. Self-tonometry with telemedicine enabled continuous evaluation of the patient by the ophthalmologist. This approach offered the advantage of controlling the treatment remotely. Advantages for the patient were that the measurements were easily done at home under normal conditions, and the patient could control when the measurement and data transmission would be performed. Telemedicine is a cost-effective technique enabling the early diagnosis of pathologically increased intra-ocular pressure.

[On line ophthalmologic education. Live transfers and on demand lectures via Internet]

Continuing medical education for ophthalmologist is important and demanded from the board of ophthalmic organizations. The use of new multimedia possibilities provided by the internet, offers an alternative to acquire the training sessions requested by the board. Aim of the paper is to show the efforts made, to place an internet-based training website for ophthalmologists by transferring live ophthalmology events via the internet. The live-transfers of selected lectures is realized by transferring the original sound compatible to the software "Real-Audio-Player" with an rate of 8000 Hz (encoding-depth 14 bits). By using this software it is possible to follow the lectures live. It includes also 2 live-pictures of 2 digital camcorders to show the appropriate slides from the lecturer. The live broadcasted lectures were afterwards revised and are available at any time as "on-demand lectures" with original sound and slides. Since November 1997, 15 continuing medical education events for ophthalmologists of the University Erlangen-Nürnberg, Germany and from other universities were live broadcasted covering all aspects of phthalmology can be viewed as "on-demand lectures" with original-sound and slides under the internet-addresse http:¿www.onjoph.com/deutsch/live.html. The broadcasted events of workshops were watched via the internet with the appropriate software by 3500 persons, and approximately 5200 persons were listening at least one of the lectures since 1997.

Continuous assessment of intraocular pressure - telematic transmission, even under flight- or space mission conditions

Fluid shift after entering into microgravity, but also under equivalent flight conditions leads to enormous increase of intraocular pressure. To assess this precisely position - and gravity independent, handsome, automatic tonometers have been developed (German-Spacelab D1-Mission, German-Spacelab D2-Mission, German-Russian-MIR-Mission) telemetric transmission of measuring results of course would find scientific but also functional interest. The same is true for recently designed automatic intraocular pressure sensors, registering intraocular pressure continuously, day and night. Also recently designed new automatic ophthalmodynamometer, allowing directly to assess the intracranial pressure, but also perfusion pressure within the eye also could benefit from a direct telemetric transmission. New technical solutions allowing for the first time even telematic data transmission, are reported.

[Changes in retinal blood flow by topical administration of 0.1% dipivefrin]

PURPOSE

Most of the antiglaucomatous drugs affect ocular blood flow. Blood flow of the anterior uvea under the effect of glaucoma medication has been described in the literature, but measurement of microcirculation at the posterior pole correlated to glaucoma medication is rarely found. We present a placebo-controlled study in which we focused on the short and long-term effects of topical dipivefrine 0.1% on the microcirculation of the retina and optic nerve head.

PATIENTS AND METHODS

In a randomized, placebo-controlled double-masked study we examined 40 healthy persons (21 male and 19 female) with a mean age of 35 +/- 4.6 years. Two groups of volunteers (n = 20) were treated either with placebo or dipivefrine 0.1% for 5 days twice a day. Measurement of microcirculation was done at baseline, 30 min after the first application and on days 3 and 5. Microcirculation was evaluated by scanning-laser Doppler flowmetry (SLDF, Heidelberg Engineering; Heidelberg, Germany) [retinal and optic nerve head capillary blood flow (ONH)]. Systemic parameters were checked at all times of blood flow measurement (blood pressure, pulse); intraocular pressure (IOP) was also measured at baseline, 30 min after and on days 3 and 5.

RESULTS

Systemic parameters: None of serum medications affected blood pressure or pulse. Dipivefrine 0.1% lowered the IOP significantly (P = 0.01). Microcirculation: dipivefrine 0.1% leads to a significant reduction of retinal capillary blood flow (P = 0.01). ONH blood flow was not significantly affected by dipivefrine 0.1%.

CONCLUSION

Retinal capillary perfusion is affected by dipivefrine 0.1% medication. In neuroprotection, it is of interest that glaucoma medication did not alter the microcirculation in a way that leads to an increase of hypoxemia. Therefore, we consider dipivefrine 0.1% not to be useful for long-term glaucoma treatment.

[New avenues of communication for continuous medical education: first experiences of live broadcasting of ophthalmologY congresses via Internet]

BACKGROUND

The usage of the Internet in live-broadcasting ophthalmological lectures might be helpful in the education of eye doctors. The purpose is to report first experiences of a live-broadcasted congress.

METHOD

The congress "Autonomic Innervation and Microcirculation of the Eye--Implications in Glaucoma Pathophysiology", held in the Department of Ophthalmology of the University Erlangen-Nürnberg at the 27th January 1999 was live-broadcasted via Internet by the electronic journal "Online Journal of Ophthalmology" (www.onjoph.com). The congress was organized by the "Sonderforschungsbereich 539, Glaukome, einschliesslich PEX" of the University Erlangen-Nürnberg. The original sound of the lectures was digitized by 8000 Hz and coded with 14 bit. Using the free software "Real-Audio-Player" the user could hear the speech of the lecturer in radio quality. Two live-pictures from two digital video cameras and the digitized slides were available at the screen within two frames. Two weeks before all 6576 ophthalmologists in Germany were informed about the event by conventional mail.

RESULTS

The live-broadcasted congress was followed by 899 online-participants (899/6576 = 13.6%). 238 of 899 participants were able to hear the original sound. 154 of 6576 (2.3%) ophthalmologists answered by FAX. 18% of the answering eye doctors have followed the congress by Internet. Mainly all (98%) of them were very interested in live-broadcasted lectures or congresses and wanted to be informed about the next lecture or congress broadcasted by means of Internet. The lectures-on demand of this congress with sound and pictures are now available under the address http:/(/)www.onjoph. com/global/livewrk1/Default.htm.

CONCLUSION

The major part of eye doctors in Germany seems very interested in live-broadcasted lectures for online-education. In the first national-wide trial 899 of 6576 informed eye doctors followed the congress.

Automatic full field analysis of perfusion images gained by scanning laser Doppler flowmetry

BACKGROUND

Scanning laser Doppler flowmetry (SLDF) enables the measurement of the laser Doppler frequency shift in retinal tissue. This process allows the quantification of retinal and optic nerve head perfusion in an area of 2.7 mm x 0.7 mm within 2 seconds and with a spatial resolution of 10 microns x 10 microns. Owing to the local heterogeneity of the retinal microcirculation itself and to heart associated pulsation the capillary retinal blood flow depends on location and time. Because of technical limitations measurements of flow are only valid in retinal points with adequate brightness and focus, and away from big vessels. To include the heart beat associated pulsation and the spatial heterogeneity of retinal blood flow into the evaluation of blood flow an algorithm was developed examining automatically the whole SLDF perfusion image.

AIM

To report intraobserver reliability and interobserver reliability of a new method for analysing automatically full field perfusion images.

METHOD

The base of blood flow calculation by the automatic full field perfusion image analyser (AFFPIA) was 16,384 intensity time curves of all pixels of the whole perfusion image gained by the SLDF. AFFPIA calculates the Doppler frequency shift and the haemodynamic variables flow, volume, and velocity of each pixel. The resulting perfusion image was processed with respect to (1) underexposed and overexposed pixels, (2) saccades, and (3) the retinal vessel tree. The rim area and the saccades were marked interactively by the operator. The capillaries and vessels of the retinal vessel tree were identified automatically by pattern analysis. Retinal vessels with a diameter greater than 30 microns, underexposed or overexposed areas, and saccades were excluded automatically. Based on the whole perfusion image total mean flow, total mean volume, total mean velocity, standard deviation, cumulative distribution curve of flow, and the capillary pulsation index were calculated automatically. Heart beat associated pulsation of capillary blood flow was estimated by plotting the mean capillary flow of each horizontal line against time. Intraobserver reliability was estimated by measuring 10 eyes of 10 subjects on five different days by one observer. Interobserver reliability of AFFPIA was evaluated by analysing 10 perfusion maps by five different operators. To find a baseline of retinal blood flow, perfusion maps of 67 eyes of normal subjects with a mean age of 40.4 (SD 15) years were evaluated by AFFPIA.

RESULTS

The coefficient of reliability of the intraobserver reproducibility of flow was 0.74. The coefficient of reliability of the interobserver reproducibility was 0.95. The juxtapapillary retinal capillary flow was temporally 484 (SD 125), nasally 450 (117); the rim area capillary flow was 443 (110). The mean capillary pulsation index of retinal flow was 0.56 (0.14).

CONCLUSION

Retinal blood flow evaluation by the AFFPIA increases significantly the interobserver reliability compared with conventional evaluation of 100 microns x 100 microns areas in SLDF images with the original Heidelberg retina flowmeter software. The intraobserver reliability of AFFPIA was in the same range as conventional evaluation.

Visual field defect and perfusion of the juxtapapillary retina and the neuroretinal rim area in primary open-angle glaucoma

BACKGROUND

At this time little information is available about the relationship between glaucomatous visual field defects and impaired blood flow in the optic nerve head. The purpose of this study was to examine blood flow of the juxtapapillary retina and the rim area of the optic nerve head in primary open-angle glaucoma with a borderline visual defect.

METHODS

Juxtapapillary retinal and neuroretinal rim area blood flow was measured by scanning laser Doppler flowmetry (SLDF). The visual field was evaluated by static perimetry (Octopus-G1). The optic nerve head was assessed on 15 degrees color stereo photographs. We examined 116 eyes of 91 patients with POAG with controlled IOP and 66 eyes of 44 healthy individuals. The POAG group was divided into eyes with a mean defect lower than 2 dB (POAG group I) and in eyes with a mean defect equal to or greater than 2 dB (POAG group II). The mean age of POAG group I and POAG group II was 55 +/- 11 years and 57 +/- 10 years, respectively. The mean age of the control group was 45 +/- 15 years. The eyes of POAG group I had an average C/D ratio of 0.71 +/- 0.18 with an average mean defect of the visual field of 0.97 +/- 0.68 dB; the eyes of POAG group II had an average C/D ratio of 0.80 +/- 0.17 with an average mean defect of the visual field of 8.2 +/- 6.0 dB. The intraocular pressure on the day of measurement in POAG group I was 18.2 +/- 3.7 mmHg, in POAG group II 17.6 +/- 4.0 mmHg, and in the control group 15.1 +/- 2.5 mmHg. For statistical analysis, age-matched groups of 32 normal eyes of 32 subjects (mean age 52 +/- 10 years) were compared to 18 glaucomatous eyes of 18 patients (POAG group I, mean age 55 +/- 11 years) and 59 glaucomatous eyes of 59 patients (POAG group II, mean age 55 +/- 10 years).

RESULTS

In the eyes of POAG group I and POAG group II, both juxtapapillary retinal blood flow and neuroretinal rim area blood flow were significantly decreased compared to an age-matched control group: neuroretinal rim area "flow" POAG group I -65%, POAG group II -66%; juxtapapillary retina "flow" POAG group I -52%, POAG group II -44%. All eyes of the POAG group I (MD < 2 dB) and 56 of 61 eyes of the POAG group II (MD > = 2 dB) showed a retinal perfusion lower than the 90% percentile of normal blood flow. We found no correlation between reduction of juxtapapillary or papillary blood flow and mean defect in POAG eyes.

CONCLUSION

Glaucomatous eyes with no defects or borderline visual field defects as well as glaucomatous eyes in an advanced disease stage show significantly decreased optic nerve head and juxtapapillary retinal capillary blood flow.