Discriminating Between Normal and Glaucomatous Eyes Using the Modified ISNT Rule

PURPOSE: To evaluate the diagnostic ability of the modified ISNT rule (disc rim thickness of the smaller of inferior and superior > the larger of nasal and temporal) for normal and glaucomatous eyes compared to the classic ISNT rule (disc rim thickness of inferior > superior > nasal > temporal). METHODS: Color stereo optic disc photographs of 113 normal subjects and 108 open angle glaucoma patients with early and moderate stage were morphometrically evaluated. The classic ISNT rule and the modified ISNT rule were assessed by masked evaluation of disc photographs at the 3, 6, 9 and 12 o'clock positions. RESULTS: Among normal subjects, 58 of 113 eyes (51.3%) were normal and in open angle glaucoma patients, 104 of 108 eyes (96.3%) were abnormal with the classic ISNT rule. Among normal subjects, 98 of 113 eyes (94.2%) were normal and in open angle glaucoma patients, 102 of 108 eyes (94.4%) were abnormal with the modified ISNT rule. The modified ISNT rule was more accurate than the classic ISNT rule in terms of Cohen's Kappa analysis used for discriminating between normal and glaucomatous eyes. CONCLUSIONS: The modified ISNT rule is useful for differentiating between normal and glaucomatous optic nerves and easily applied in clinical practice.

Comparison of Optic Disc Measurements between Computer-aided Morphometry and Heidelberg Retina Tomograph

PURPOSE: To compare optic disc measurements between computer-aided morphometry and Heidelberg Retina Tomograph (HRT). METHODS: For 59 patients with primary open-angle glaucoma and 9 subjects with ocular hypertension, measurements of the optic disc area and neuroretinal rim area were obtained using our computer-aided morphometric techniques and the HRT. RESULTS: The mean optic disc areas measured with the HRT was smaller than those with the computer-aided techniques (p=0.02). Rim area and rim area to disc area were significantly (p

Quantification of Retinal Nerve Fiber Layer Thickness in the Normal Subjects Using Optical Coherence Tomography

Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross sectional images of retina with approximately 10micrometer resolution. This study was designed to evaluate the quantification of nerve fiber layer [NFL] thickness in normal eyes using OCT. We studied 66 eyes of 66 subjects by conventional ophthalmoscopic physical examination, Humphrey central 30-2 visual fields, stereoscopic optic nerve head photography, retinal nerve fiber layer photography, HRT and OCT. Imaging with OCT was performed circumferentially around the optic nerve head with a circle diameter of 2.3mm & 3.4mm using an internal fixation technique. At a scan diameter of 2.3mm and 3.4mm, average, superior, inferior, nasal and temporal NFL thicknesses were 125.45 +/-19.05 micrometer, 150.33 +/-25.53micrometer, 154.55 +/-25.72 micrometer, 102.89 +/-29.13micrometer, and 92.65 +/-27.04micrometer and 109.02 +/-15.68 micrometer,135.53 +/-22.65 micrometer, 132.98 +/-20.19micrometer, 73.11 +/-26.85 micrometer and 89.70 +/-14.65 micrometer each. The NFL was thickest in the superior and inferior quadrants,thinnest in the nasal quadrant at a scan diameter of 2.3mm, and thinnest in the temporal quadrant at a scan diameter of 3.4 mm. In general the thickness for the 2.3 mm scans was greater than that for the 3.4mm scans.NFL thickness decreased significantly with age in the temporal quadrants [P<0.05]. At a scan diameter of 3.4 mm, NRA decreased significantly with decreased average NFL thickness and average NFL thickness decreased significantly with decreased disc area [P<0.05]. By direct investigation of the NFL with OCT, earlier diagnosis of glaucoma and earlier detection of glaucomatous progression can be made, before conventional signs such as visual field loss, cupping of the optic nerve head, and NFL defects are evident, thus allowing earlier treatment and reducing the damage.

The Difference of the Optic Disc Size Calculated Using a Modified Formula of an Ellipse from Those Obtained with Twelve Radii

The aim of this study was to compare optic disc size obtained using the two methods Color polaroid photographs of optic disc of 130 normal subjects and 174 patients with glaucoma were evaluated by means of computeraided morphometry. In the first method, the optic disc size were calculated by applying the modified formula of an ellipse, where area=pi/4xthe horizontal diameterxthe vertical diameter. In the second method, we obtained optic disc size [] using the twelve radii that were measured every 30 degrees. Magnification effects of the eye and camera were corrected in the two methods. The measurements of the optic disc area(2.49mm2), cup area(1.01mm2) and neuroretinal rim area (1.49mm2) by the first method were significantly(P<0.003, Wilcoxon signed -rank test) different from the measurements by the second method(2.48mm2, 1.03mm2, 1.45mm2, respectively) (the average difference; 0.05+/-0.05mm2, 0.05+/-0.05mm2, 0.07+/-0.06mm2,respectively). The mean error for the neuroretinal rim area was 4.2+/-3.3% in the normal group and 7.5+/-8.5% in the glaucoma group(P=0.005). It increased with decreasing neuroretinal rim area and increasing visual field defects. Thus the magnification corrected measurements of the horizontal and vertical diameters and the modified formula of an ellipse can be used for a quick approximate estimation of the optic disc size, but cannot replace more accurate method of optic disc measurements using twelve radii.

Regional Comparison of Heidelberg Retinal Tomographic Measurements of Normal and Early Glaucomatous Optic Nerve Head

To estimate normal values for optic nerve head parameters in Korean adults and establish pattern of early glaucomatous neuroretinal rim loss, we measured the mean value of each parameter according to 6 predefined sectors with Heidelberg Retina Tomograph. 500 eyes of normal 500 individuals and 30 eyes of early primary open angle glaucoma patients whose mean defect was less than -5dB in automated threshold perimetry(Humphrey programs C30-2) were enrolled in this study. Comparing with normal subjects, the early glaucoma group had significant difference in 8 parameters(p<0.05). The neuroretinal rim area in normal eyes were significantly largest in the nasal inferior and nasal sectors, decreased in the order of nasal superior, temporal inferior, temporal, nasal inferior, and nasal sectors(p<0.05). We established normal values of optic nerve head parameters in Korean adults and these results suggest the regional preference of optic nerve head damage in early glaucoma.

Regional Comparison of Heidelberg Retinal Tomographic Measurements of Normal and Early Glaucomatous Optic Nerve Head

To estimate normal values for optic nerve head parameters in Korean adults and establish pattern of early glaucomatous neuroretinal rim loss, we measured the mean value of each parameter according to 6 predefined sectors with Heidelberg Retina Tomograph. 500 eyes of normal 500 individuals and 30 eyes of early primary open angle glaucoma patients whose mean defect was less than -5dB in automated threshold perimetry(Humphrey programs C30-2) were enrolled in this study. Comparing with normal subjects, the early glaucoma group had significant difference in 8 parameters(p<0.05). The neuroretinal rim area in normal eyes were significantly largest in the nasal inferior and nasal sectors, decreased in the order of nasal superior, temporal inferior, temporal, nasal inferior, and nasal sectors(p<0.05). We established normal values of optic nerve head parameters in Korean adults and these results suggest the regional preference of optic nerve head damage in early glaucoma.

Optic Disc and EarIy Glaucomatous Visual Field Loss

In the early stages of glaucoma the disc changes prior to the visual field loss, so assessment of the optic disc is very important for the evalutation of the glaucoma patient. The most senstitive techniques for detecting changes of the optic disc require highly sophisticated instruments, such as computerized image analyzer, which are expensive and not generally available in clinical practice. Less expensive, but reliable, is color stereoscopic photography. The aim of this topic is to assess glaucomatous discs and look for the features of the optic disc that are commonly associated with early visual field defect. Forty-three eyes of 28 patients were included in this investigation. The criteria for inclusion were a cup/disc(C/D) ratio more than 0.4 by direct ophthalmoscopy, no visual field defect with Goldmann perimetry, and open anterior chamber angle. Each optic disc was photographed with a Canon fundus camera with Polaroid 600 Plus. Each photographic set was then examined stereoscopically for morphologic parameters: 1) comparison of vertical versus horizontal C/D ratio; 2) presence of nasal cupping; 3) presence of overpassing vessels; 4) presence of baring of circumlinear vessles; 5) presence of peripapillary atrophy; 6) ratio of the thinnest neuroretinal rim(NRR) width in the vertical sectors to the NRR width of the temporal sector. All subjects were examined for central visual field with the automated static perimeter, Humphrey program C 30-2 with STATPAC. The C/D ratio estimated by direct ophthalmoscopy consistently showed smaller C/D ratio than that by the stereophotographic method. Parameter with highest probability value to differentiate between the optic disc of early visual filed loss and the optic disc of normal subjects was "Ratio of the thinnest NRR width in the vertical sectors to the NRR width of the temporal sector

Optic disc and early glaucomatous visual field loss

In the early stages of glaucoma, the disc changes prior to visual field loss, so assessment of the optic disc is very important for the evaluation of the glaucoma patient. The aim of this study is to assess the glaucomatous disc and to look for the features of the optic disc that are commonly associated with early visual field loss. Forty-three eyes of 28 patients were included in this investigation. The criteria for inclusion were a cup/disc(C/D) ratio of more than 0.4 by direct ophthalmoscopy, no visual field defect with Goldmann perimetry, and open anterior chamber angle. Each optic disc was photographed with a Canon fundus camera with Polaroid 600 Plus film. Each photographic set was then examined stereoscopically for morphologic parameters: 1) comparison of vertical versus horizontal C/D ratio; 2) presence of nasal cupping; 3) presence of overpassing vessels; 4) presence of baring of circumlinear vessels; 5) presence of peripapillary atrophy; 6) ratio of the thinnest neuroretinal rim(NRR) width in the vertical sectors of the NRR width of the temporal sector. All subject's central visual fields were examined with an automated static perimeter, Humphrey program C30-2 with STATPAC. The C/D ratio estimated by direct ophthalmoscopy consistently showed a smaller C/D ratio than that found by the stereophotographic method. The parameter with the highest probability value to differentiate between the optic disc of the early visual field loss and the optic disc of normal subjects was "Ratio of the thinnest NRR width in the vertical sectors to the NRR width of the temporal sector < or = 85%". Although it has less resolving power than slide film, a stereo disc photograph with Polaroid film is a quick and simple method of recording changes, and the ratio of the thinnest NRR width in the vertical sectors to the temporal sector is a good predictive parameter for detection of early visual field loss.