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A Tuulonen

Publications and source records attributed to A Tuulonen.

At least 19 recordsLinked to original sources
PubMed2000

Development of the standard reference plane for the Heidelberg retina tomograph.

BACKGROUND: Topometry of the optic disc is the quantitative assessment of the structure of the optic nerve head by means of three-dimensional parameters. The parameter values depend on definitions of intraocular reference planes. PURPOSE: To describe the development of intraocular reference planes in laser scanning tomography for the Heidelberg Retina Tomograph (HRT) using image intrinsic data with a fixed offset reference plane (320 microm) and to present a contour-line-based "flexible" standard reference plane ("SRP") for calculation of intrapapillary stereometric parameters taking the interindividual variability of optic disc topography into account. METHODS: Ten-degree triple images were obtained by laser scanning tomography from 99 glaucoma eyes and 180 normal eyes. The images were evaluated to assess the variability of height measurements of an optic disc border contour-line segment (6 degrees width) corresponding to the site of the papillo-macular bundle as indicated by the average optic disc surface inclination angle. RESULTS: The average optic disc surface inclination angle was -7 degrees +/- 3 degrees below the horizontal meridian (0 degrees). The 6 degrees wide contour-line segment for the SRP was chosen according to the average surface inclination angle (-10 degrees to -4 degrees). The reproducibility of the SRP-segment height measurements was 16.0+/-10.8 microm for normal eyes and 23.4+/-18.0 microm for glaucoma eyes. To ensure that the automatic reference level determination for intrapapillary parameters remained below the disc border height, we defined the SRP level at a 50 microm offset (>2 SD of average segment height reproducibility in glaucoma) added to the individual height position of the 6 degrees contour line segment. CONCLUSION: The flexible standard reference plane allows for automatic determination of intrapapillary variables once a disc border contour line is interactively defined. In contrast to a fixed offset reference plane (e.g. 320 microm below the mean retina height), the interindividual variability of optic disc topography (oblique insertion, glaucomatous surface flattening) is respected at the cost of the need for an accurate optic disc border outline.

Diagnostic Techniques, Ophthalmological↗
PubMed2000

Search for an optimal combination of structural and functional parameters for the diagnosis of glaucoma. Multivariate analysis of confocal scanning laser tomograph, blue-on-yellow visual field and retinal nerve fiber layer data.

BACKGROUND: The purpose of this study was to evaluate which of the structural and functional parameters--the Heidelberg Retina Tomograph (HRT), white-on-white (W/W) and blue-on-yellow (B/Y) visual fields and semiquantitative retinal nerve fiber layer (RNFL) scoring parameters--can give the best separation between non-glaucomatous and glaucomatous eyes. METHODS: Fifty-five subjects were included in this study: 32 nonglaucomatous subjects with mean age of 54 years, and 23 patients with ocular hypertension or glaucoma and mean age of 59 years. The HRT with software 1.11, the Humphrey 30-2 W/W and lens coloration-corrected B/Y visual fields, and semiquantitative RNFL scores were utilized. Stepwise logistic regression analysis was used in finding, from a given set of parameters, a best discriminating parsimonious subset to a logistic model, the discriminatory performance of which was evaluated by the area under the ROC curve. RESULTS: When all the structural and functional variables were considered, the RNFL total overall score gave the best separation between glaucomatous and non-glaucomatous eyes (ROC area 0.98). Without the RNFL scores and optic disc size-dependent HRT parameters in the model, the cup shape measure was selected first (ROC area 0.88). In the second step the RNFL thickness was selected (ROC area 0.91), and in the third step the corrected B/Y mean deviation (MD) was selected (ROC area 0.91). With only the HRT parameters in the model, the cup/disc ratio was selected first (ROC area 0.88). However, when the groups were matched for optic disc size, all disc size-dependent HRT variables lost their discriminant power. CONCLUSION: Cup shape measure and RNFL thickness, together with age- and lens coloration-corrected MD of the B/Y perimetry provided good discrimination between healthy individuals and patients with glaucoma.

Adult↗
PubMed2000

Optical coherence tomography and localized defects of the retinal nerve fiber layer.

PURPOSE: To test the capability of the optical coherence tomography (OCT) to demonstrate and quantitate retinal nerve fiber layer (RNFL) defects. METHODS: The authors examined 6 eyes of 6 chronic open angle glaucoma patients with the OCT. The patients had abnormal Humphrey 30-2 visual fields which corresponded to RNFL defects visible in monochromatic fundus images taken with a digital imaging system. The RNFL images were used for directing the OCT scans to areas where most information was believed to be obtainable. Several linear scans of different lengths across healthy and abnormal RNFL regions were made. RESULTS: When the OCT images were compared to RNFL photographs, the defective areas showed reduced backscattering with the OCT, being distinctly different from the adjacent normal RNFL. Except for one case the RNFL thickness values were smaller in the areas of abnormal appearance compared to areas of normal appearance. CONCLUSION: This preliminary study suggests that the OCT examination results of the RNFL are in good agreement with the RNFL appearance in monochromatic fundus images.

Axons↗
PubMed2000

Digital imaging and microtexture analysis of the nerve fiber layer.

PURPOSE: To describe the design of a digital retinal nerve fiber layer (RNFL) imaging techniques and present a new approach to measure the differences in RNFL patterns. METHODS: A digital camera body is connected to a wide-angle camera to obtain images of the RNFL, which are displayed in workstations throughout the clinic. In the on-line archive, images in Joint Photographics Experts Group (JPEG) format (100 KB per frame) are used. The hypothesis that changes in RNFL structure can be seen as changes in the microtexture of digital images was tested using an information theoretical approach (Kullback Information Distance, KID). A large KID value indicates a large difference, and a small KID value indicates a small difference in microtexture between the two regions. The material of this pilot study consists of 9 patients with glaucoma, 8 patients with ocular hypertension, and 7 normal subjects. RESULTS: The median KID value in the glaucoma group was 3.5, compared with the median KID values of 0.6 in the control groups. Although a trend could be seen in the measured values, because of a small sample size, the differences were not statistically significant. Five of 24 (21%) KID values overlapped between the glaucomatous group and the other two groups. CONCLUSION: Although digital imaging produces good quality RNFL images, further research is needed to establish minimum accepted specifications for digital imaging. In this pilot study, only the microtexture of the RNFL was measured in digital images. In the future, the approach can be expanded to include also properties of macrotexture and full color palette.

Exfoliation Syndrome↗
PubMed1999

Postoperative systemic corticosteroid treatment and Molteno implant surgery: a randomized clinical trial.

PURPOSE: To determine whether it is possible to improve the surgical success of Molteno implantation by causing a general suppression of collagen synthesis with postoperative oral prednisolone. METHODS: Twenty-two patients requiring single stage, single-plate Molteno implantation were randomized into two study groups: the control group A and the systemic prednisolone treatment group B. Serum markers of collagen metabolism were monitored. RESULTS: A successful outcome at the end of the 6-month follow-up, defined as final IOP > or =6 mmHg and < or =22 mmHg with less or equal number of antiglaucoma medication as preoperatively and no additional surgery was achieved in 9 of 11 (82 %) patients of group A and in 5 of 10 (50 %) patients of group B (p= 0.18). There was a statistically significant decrease in serum markers of collagen synthesis in the group B but not in the group A. CONCLUSION: The serum markers indicated a systemic effect of oral prednisolone on collagen synthesis in group B but it did not improve the surgical outcome as compared to the controls.

Administration, Oral↗
PubMed1999

The application of teleophthalmology in examining patients with glaucoma: a pilot study.

PURPOSE: To test the feasibility of teleophthalmology applications in examining patients with glaucoma, test its use for training purposes in an ophthalmology residency program and as a consultation link between primary healthcare unit and university eye clinic, and to introduce a preliminary model for economic assessment of telemedicine application in ophthalmology. METHODS: A video slit-lamp, an automated perimeter, a nonmydriatic fundus camera and a videoconferencing system were installed in a healthcare center in a rural area. Twenty-nine patients with glaucoma were examined in the rural healthcare center instead of the university eye clinic. A control group consisted of 41 glaucoma patients examined at the eye clinic one year earlier. An ophthalmic resident examined the patients together with the local general practitioner. An interactive video consultation was created with the university glaucoma clinic using ISDN connections and special application software. RESULTS: Both patient groups were equally satisfied with the ophthalmic service. Nearly all patients in the telemedicine group (96%) wanted to have their next visit in their own healthcare center instead of the university clinic. The most important reasons were reduction in traveling (97%), costs (92%), and time (92%). The costs of the telemedicine and conventional visits were equal, but decreased traveling saved $55 per visit. However, the quality of the images obtained in the remote center was poorer than that of the images obtained at the university clinic. CONCLUSION: The results of this pilot study indicate that further research with a larger number of patients is warranted to evaluate both methods, technology, and economics of teleophthalmology.

Academic Medical Centers↗
PubMed1998

Hemifield association between blue-on-yellow visual field and optic nerve head topographic measurements.

BACKGROUND: Blue-on-yellow (B/Y) perimetry can reveal visual field defects earlier and larger in extent than white-on-white (W/W) perimetry. The Heidelberg Retina Tomograph (HRT) produces a three-dimensional image of the optic disc. The aim of this study was to compare the strength of the association of the B/Y and W/W visual hemifield mean deviation (HMD) variables with the optic nerve head (ONH) morphological variables of the respective area. METHODS: We evaluated one randomly chosen eye of 40 normal subjects and 37 patients with ocular hypertension and different stages of glaucoma. The B/Y and W/W visual fields (program 30-2) were obtained with a Humphrey perimeter. Results of both visual fields were adjusted for the patient's age and lens transmission index measured with a lens fluorometer. HMD was calculated as the difference between the measured and expected hemifield mean sensitivity values, predicted by the regression model fitted in our nonglaucomatous subject data. The HRT with the software version 1.11 was used to acquire and evaluate the topographic measurements of the optic disc. RESULTS: The B/Y and W/W visual field HMDs showed statistically significant correlation with ONH parameters such as cup shape measure (CSM), rim volume, rim area, mean retinal nerve fiber layer (RNFL) thickness and RNFL cross-sectional area. With forward stepwise logistic regression analysis using B/Y hemifield data 38% of the glaucoma patient's normal W/W hemifields were classified abnormal. With the CSM alone in the model 52% of the cases were classified abnormal. CONCLUSIONS: B/Y visual field hemifield mean deviation values correlate well with ONH parameters examined with the HRT.

Adult↗
PubMed1998

Blue-on-yellow visual field and retinal nerve fiber layer in ocular hypertension and glaucoma.

BACKGROUND AND OBJECTIVE: It has been suggested that the clinically detectable changes of the blue-on-yellow (B/Y) visual field and retinal nerve fiber layer (RNFL) may precede standard white-on-white (W/W) visual field defects in the progression of glaucoma. The aim of this study was to test the relationship between the results of B/Y visual fields and semiquantitative RNFL evaluation in corresponding areas and to determine how the B/Y visual fields and RNFL scores label the normal W/W perimetry hemifields in patients with glaucoma and ocular hypertension. DESIGN: A cohort study. PARTICIPANTS AND METHODS: Monochromatic RNFL photographs of 32 normal subjects and 29 patients with ocular hypertension and different stages of glaucoma were assessed in a masked fashion. The B/Y and W/W visual fields (program 30-2) were examined with a Humphrey perimeter. The results of both visual fields were adjusted for the patients' age and lens transmission index measured with a lens fluorometer. MAIN OUTCOME MEASURE: Mean deviation (MD) of visual field and semiquantitative score of RNFL loss were measured. RESULTS: The total and hemifield MD values of B/Y and W/W visual field showed a statistically significant correlation with diffuse and overall score of RNFL loss in corresponding areas. The hemifield MD values of B/Y perimetry obtained from "normal" W/W hemifields of patients with early glaucoma were well correlated (r = -0.56) with respective RNFL loss scores found to be abnormal in 84% of hemispheres. The difference between the hemifield MD values of B/Y perimetry obtained from normal W/WAN hemifields of patients with ocular hypertension and patients with early glaucoma was not statistically significant (analysis of variance). The respective B/Y hemifield data of normal subjects were statistically significantly different from the data of patients with ocular hypertension and early glaucoma. CONCLUSIONS: The hemifield MD values of B/Y perimetry correlate well with semiquantitative scores of RNFL loss obtained from the corresponding hemisphere. The B/Y perimetry as well as RNFL assessment may show glaucomatous defects in a hemifield found to be normal on W/W perimetry. In subjects with ocular hypertension, the functional damage detected by B/Y perimetry may, in some cases, precede RNFL defects on conversion to glaucoma.

Adult↗
PubMed1998

Outcome of Molteno implantation surgery in refractory glaucoma and the effect of total and partial tube ligation on the success rate.

PURPOSE: To analyze the results of 87 consecutive one-stage Molteno implantations in 87 patients and evaluate the factors influencing the surgical outcome, especially the effect of intraoperative partial and total occlusion of the tube. METHODS: Successful outcome was defined as final intraocular pressure (IOP) between 6 and 22 mmHg with less or equal amount of glaucoma medication than preoperatively without loss of light perception. RESULTS: After a mean (+/-SD) follow-up of 24+/-17 months, the mean IOP was 18.1+/-16.0 mmHg compared to the preoperative mean of 42.4+/-11.1 mmHg (p<.0001). One-, 2- and 4.5-year life-table success rates were 90%, 75% and 50%, respectively. There was no statistically significant difference in the success rate between the eyes with total and partial tube occlusion (p=0.703). Postoperative hyphema, suprachoroidal hemorrhage and the number of systemic medications were the only factors significantly associated with failure. CONCLUSIONS: Molteno implantation is warranted in patients with refractory glaucoma who have undergone numerous previous surgical procedures.

Adolescent↗
PubMed1998

Laser scanning tomography of localised nerve fibre layer defects.

AIMS: Retinal nerve fibre layer photography is a well established method to qualitatively document early structural changes which might be induced by primary open angle glaucoma. The aim was to analyse localised retinal nerve fibre layer (RNFL) defects in a new quantitative way with respect to surface topography, defect width, and surface reflectivity by means of the technique of confocal scanning laser tomography. METHODS: 12 eyes of 12 patients with a localised RNFL defect documented in RNFL photographs and a normal appearance of the optic disc were enrolled in the study. Using confocal laser scanning tomography (Heidelberg retina tomograph, HRT) a series of 32 optical section images from different focal planes of the retina at the site of the RNFL defects were obtained. The optical section images, the reflectivity images, and the topographic images were analysed regarding the visibility of the RNFL defects. The mean surface height and the reflectance at the sites of the RNFL damage were measured and compared with the adjacent apparently normal retina. The width of the RNFL defect at 1 mm distance from the disc border was evaluated. RESULTS: RNFL defects could be detected in nine of 12 reflectivity images (75%). Single optical section images displayed the RNFL defects in 12 of 12 eyes. The defect width ranged from 0.11 to 1.0 mm. In six of 12 eyes a surface depression (34 (SD 5) microns; range 21-47 microns) was present. The reflectance ratio ranged from 0.68 to 0.94 at the site of the RNFL defect. In eyes with a glaucomatous scotoma in a 6 degrees grid visual field (VF), the defect width was at least 0.25 mm. Surface depression and low reflectance ratio were found irrespective of the presence of a scotoma in the 6 degrees grid VF. CONCLUSION: The majority of localised RNFL defects can be detected in reflectivity images from laser scanning tomograms. Localised RNFL defects may be differentiated according to surface topography into those with and those without a measurable surface depression. A small but deep RNFL defect is not necessarily associated with a scotoma in routine 6 degrees grid VF static perimetry.

Aged↗
PubMed1997

Molteno implantation for secondary glaucoma in juvenile rheumatoid arthritis.

OBJECTIVE: To evaluate the outcome of Molteno implantation in secondary glaucoma associated with juvenile rheumatoid arthritis. METHODS: Between January 1, 1986, and December 1, 1996, 27 eyes of 19 consecutive patients with secondary glaucoma due to juvenile rheumatoid arthritis received a Molteno implant. The diagnosis of juvenile rheumatoid arthritis was made according to the American Rheumatism Association criteria. RESULTS: At the end of the follow-up (mean, 40 months; range, 6-116 months), the mean (+/-SD) postoperative intraocular pressure (IOP) (14.4+/-4.3 mm Hg) was statistically significantly lower than the preoperative IOP (38.3+/-5.6 mm Hg) (P<.001). The Snellen visual acuity remained within 1 line of the preoperative level or improved in 23 (85%) of 27 eyes. A successful outcome (defined as a final IOP of > or =6 mm Hg and < or =22 mm Hg, with fewer than or an equal number of antiglaucoma medications as preoperatively) was achieved in 24 (89%) of 27 eyes. Life-table analysis success rates were 95% after 27 months and 90% after 52 months of follow-up. Postoperative complications included flat anterior chamber (3 eyes), tube block by iris or vitreous (3 eyes), cataract (3 eyes), cornea-tube touch (2 eyes), choroidal detachment (1 eye), corneal edema (1 eye), and corneal abrasion (1 eye). CONCLUSION: The Molteno implant is useful and well tolerated in controlling IOP in patients with glaucoma secondary to juvenile rheumatoid arthritis.

Adolescent↗
PubMed1997

Comparison of optic disc measurements by Heidelberg Retina Tomograph and manual planimetric techniques.

The inner edge of the scleral ring is used as a reference plane for manual, computer assisted optic disc measurements. As it is possible to identify this level with the Heidelberg Retina Tomograph, our aim was to compare manual measurements to those taken with the Heidelberg Retina Tomograph. The material of this pilot study consisted of 12 eyes of 12 patients with early glaucomatous optic disc, retinal nerve fiber layer and/or visual field abnormalities. Measurements of the optic disc and neuroretinal rim area were obtained using our manual planimetric techniques, and the Heidelberg Retina Tomograph. The mean optic disc areas measured smaller with the Heidelberg Retina Tomograph than with the manual techniques (average difference 0.13 mm2; p < 0.05). The neuroretinal rim area measurements and cup-to-disc area ratio using manual and Heidelberg Retina Tomograph techniques did not differ statistically significantly from each other. With the scleral ring as a reference plane, comparable optic disc measurements can be obtained with manual and laser techniques.

Aged↗
PubMed1997

Influence of lens autofluorescence on retinal nerve fiber layer evaluation.

BACKGROUND: Yellow-brown coloration of the human lens increases with age and is associated with increasing lens autofluorescence. This may interfere with retinal image through scatter and absorption. PATIENTS AND METHODS: We measured the lens autofluorescence (AF) of 30 eyes of 30 healthy subjects and evaluated their retinal nerve fiber layer (RNFL) visibility from fundus photographs. These otherwise healthy eyes showed a varying degree of yellow-brown coloration of the lens. Lens fluorometry was carried out with a previously described technique using blue-green AF range (495 nm/520 nm). RNFL photographs were taken with a Canon CF-60 ZA wide angle camera with blue (495 nm) interference filter and low-sensitivity, high resolution black-and-white film. RESULTS AND CONCLUSION: Lens yellowing expressed here by means of lens autofluorescence measurements, was statistically significantly (r = -0.53, p = 0.0008) correlated with the RNFL visibility score. In stepwise regression analysis adding age to the model including only the maximum AF did not reduce the residual standard deviation statistically significantly (p = 0.1). This suggests that lens yellowing has an effect on RNFL visibility and may be an important confounding factor in clinical RNFL evaluation.

Aged↗
PubMed1997

Fluorometry of the crystalline lens for correcting blue-on-yellow perimetry results.

PURPOSE: Optical and neural sources of short wavelength sensitivity should be separated in the assessment of the results of blue-on-yellow (B/Y) perimetry. It has been shown previously that lens autofluorescence is related directly to lens yellowing and age. The aim of this study was to find out if B/Y perimetry results can be better corrected by using lens fluorometry than by age. METHODS: The authors evaluated one randomly chosen eye of 40 normal subjects and 39 age-matched patients with ocular hypertension and different stages of glaucoma. The authors obtained the mean sensitivity (MS) of the 24-2 B/Y visual fields with a Humphrey perimeter and determined the lens transmission index (LTI) from the ratio between posterior and anterior autofluorescence peaks measured with their fluorometer. A multiple regression analysis was used to evaluate the variability of the B/Y MS by age and LTI in normal subjects. RESULTS: The authors found a statistically highly significant linear correlation of B/Y MS to LTI in healthy subjects (R = 0.83; P < 0.0001). The 95% prediction interval of the normal subjects was determined. The majority of the MS values of the ocular hypertensives were inside the prediction limits, whereas approximately half of the patients (4 of 9) with early glaucoma and the majority of patients (14 of 15) with moderate and advanced glaucoma were below the prediction interval. The residual standard deviation of the B/Y MS with age alone was larger than that with LTI alone in the model (3.66 dB and 3.22 dB, respectively). CONCLUSIONS: The interindividual variation of the lens transmission properties increases with age. The reference level for correcting B/Y perimetry results can be determined more precisely using fluorometry of the lens than with age alone.

Adult↗
PubMed1997

Capsule excision after failed Molteno surgery.

BACKGROUND AND OBJECTIVES: To determine the frequency of scar tissue formation requiring surgical intervention after single-plate Molteno implantation and the outcome of excision of the encapsulated bleb. PATIENTS AND METHODS: A retrospective study was performed on 95 eyes of 79 consecutive patients who underwent a single-stage Molteno implantation for refractory glaucoma. Fourteen eyes of 12 patients developed an encapsulated bleb. A successful outcome after bleb excision was defined as final intraocular pressure (IOP) between 6 and 22 mm Hg with the same amount of medication as preoperatively or less. RESULTS: At the end of the mean follow-up of 30 months (range 8 to 75), the mean IOP (19.7 +/- 3.8 mm Hg) after bleb excision was significantly lower than the preoperative IOP (35.2 +/- 10.1 mm Hg; P < .001). The overall conventional success rate was 75%. CONCLUSION: Excision of the encapsulated Molteno bleb offers an alternative in severely damaged eyes that have undergone several surgical procedures.

Adolescent↗
PubMed1997

Phacoemulsification with and without trabeculectomy in patients with glaucoma.

BACKGROUND AND OBJECTIVE: This retrospective study was performed to determine the postoperative intraocular pressure (IOP) control in patients with glaucoma who underwent phacoemulsification with and without trabeculectomy. PATIENTS AND METHODS: Thirty-five eyes underwent phacoemulsification, and 21 eyes underwent combined surgery. The minimum postoperative follow-up for both groups was 6 months. RESULTS: The average IOP decreased from 19.7 +/- 4.6 mm Hg preoperatively to 16.3 +/- 3.1 mm Hg in the phacoemulsification group, and from 21.2 +/- 5.9 mm Hg to 14.4 +/- 3.3 mm Hg in the combined group at 6 months (statistically not significant). There was no statistically significant difference between the groups in terms of visual acuity improvement or the number of glaucoma medications. CONCLUSION: Cataract surgery, with phacoemulsification alone and combined with trabeculectomy, induces a statistically and clinically significant reduction of IOP in patients with glaucoma.

Aged↗
PubMed1997

Correlation of blue-on-yellow visual fields with scanning confocal laser optic disc measurements.

PURPOSE: Visual field defects and changes in the optic nerve head are signs of glaucoma. It has been shown that blue-on-yellow (B-Y) perimetry can reveal visual field defects earlier and shows them larger than does white-on-white (W-W) perimetry. The Heidelberg retina tomograph (HRT) can produce three-dimensional images of the optic disc. The aim of this study was to find out how B-Y perimetry results correlate with optic disc parameters in comparison with W-W perimetry results. METHODS: One randomly chosen eye was evaluated in each of 40 normal subjects and 37 patients with ocular hypertension and different stages of glaucoma. B-Y and W-W visual fields (program 30-2) were obtained with a Humphrey perimeter. B-Y perimetry results were adjusted for the patient's age and lens transmission index measured with a lens fluorometer. The B-Y visual field adjusted mean deviation (MD) was calculated as the difference between the measured and expected mean sensitivity values, predicted by the regression model fitted in normal subjects. The HRT with software version 1.11 was used to acquire and evaluate topographic measurements of the optic disc. RESULTS: The cup shape measure showed strongest correlation with the MD of both the B-Y and W-W visual fields. The multiple correlation coefficients from quadratic regression were 0.65 for both visual fields. Except for peripapillary retinal nerve fiber layer measurements, the statistically significant correlations of the B-Y visual field indexes with other HRT parameters were equal to or better than those of W-W perimetry. CONCLUSIONS: B-Y perimetry MDs are well correlated with optic nerve head parameters measured with the HRT. In early stages of glaucoma, most HRT variables were better correlated with the B-Y MD than with the W-W MD.

Adult↗