Optic Nerve Head Photographs Research Articles

Optical Coherence Tomography Measurement of the Retinal Nerve Fiber Layer in Normal and Juvenile Glaucomatous Eyes

The aim of this study was to quantitatively assess and compare the thickness of the retinal nerve fiber layer (RNFL) in normal and glaucomatous eyes of children using the optical coherence tomograph. The mean RNFL thickness of normal eyes (n = 26) was compared with that of glaucomatous eyes (n = 26). The eyes were classified into diagnostic groups based on conventional ophthalmological physical examination, Humphrey 30-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. The mean RNFL was significantly thinner in glaucomatous eyes than in normal eyes: 95 ± 26.3 and 132 ± 24.5 µm, respectively. More specifically, the RNFL was significantly thinner in glaucomatous eyes than in normal eyes in the inferior quadrant: 87 ± 23.5 and 122 ± 24.2 µm, respectively. The mean and inferior quadrant RFNL thicknesses as measured by the optical coherence tomograph showed a statistically significant correlation with glaucoma. Optical coherence tomography may contribute to tracking of juvenile glaucoma progression.

Long-term outcomes in asians after acute primary angle closure

Purpose To determine the long-term outcome of Asian eyes with an acute attack of primary angle closure (APAC) and to identify risk factors at presentation associated with the development of glaucomatous optic nerve damage. Design Cross-sectional observational case series. Participants Ninety individuals who were initially seen with APAC 4 to 10 years previously at 2 Singapore hospitals. Methods All subjects underwent a complete eye examination, including visual acuity, visual field testing, dilated eye examination, and optic nerve head photography. The optic discs were judged clinically and photographically as to whether there was glaucomatous optic neuropathy present, and visual fields were assessed for corresponding visual field loss. All visual fields and optic nerve photographs underwent a second evaluation by an experienced, but masked, glaucoma specialist, who assessed whether the changes were compatible with glaucoma. Main outcome measures The main outcome measures were blindness (defined as best-corrected visual acuity worse than 6/60 and/or central visual field of less than 20° in the attack eye) and glaucomatous optic neuropathy (GON). Results A total of 90 of 170 eligible subjects (65.2%) were examined. All subjects were Asian and were predominantly Chinese (78 subjects [86.7%]). There were 61 females (67.8%), and the age of the subjects was 62.0±9.0 years (mean ± standard deviation) at the time of APAC, with a mean duration of 6.3±1.5 years from the time of the APAC episode to the study examination. Sixteen (17.8%) subjects were blind in the attack eye; half of the cases of blindness were caused by glaucoma. Forty-three subjects (47.8%) had GON, with 13 eyes (15.5%) having markedly cupped optic discs (cup-to-disc ratio >0.9). Thirty-eight eyes (58%) had best-corrected vision worse than 6/9, with cataract responsible for close to half the cases of poor vision. There were no identifiable risk factors related to the APAC episode that were significantly associated with the presence of GON. Conclusions Several years after being seen with APAC, 17.8% of subjects examined were blind in the attack eye, and almost half had glaucomatous optic nerve damage. Vision was also reduced in a large number of individuals, largely from unoperated cataract. Subjects with APAC would benefit from regular follow-up to monitor for visual field decline and glaucoma development.

Flicker comparison of optic disc photographs: sensitivity and specificity

Examination and documentation of the optic nerve head are essential in monitoring glaucoma patients. Even minor changes in optic nerve head morphology can be visualised using the so-called flicker test: Two optic nerve head photographs, taken at consecutive examinations, are superimposed by projection. When occluding the pictures in a rapid alternating fashion, changes in optic nerve head morphology appear as motion. In this study, we evaluated sensitivity and specificity of the flicker test. A set of 33 pairs of serial optic disc slides was used as gold standard. These 33 pairs had been classified earlier by 3 independent groups of experts. 23 had been classified as "no change over time", 10 had been classified as "change". All 33 pairs were now evaluated by flicker comparison in a masked fashion. Flicker comparison usually took 1 minute per pair of slides. Sensitivity was 90 %, specificity was 65 %. The sensitivity was reasonably high. The moderate specificity was due to some cases showing "change" with the flicker comparison which might have been overlooked by the expert groups. Flicker comparison is an easy, fast and reliable technique to evaluate pairs of consecutive optic disc photographs.

Interobserver variability of optic disk variables measured by confocal scanning laser tomography

PURPOSE: To assess the interobserver variation of confocal laser scanning tomographic measurements of the optic nerve head and to address the question of whether the addition of clinical optic disk photographs is helpful in outlining the optic disk margin and in reducing the observer-related variation of the measurements. PATIENTS AND METHODS: Optic disk variables for 16 eyes of 16 patients with glaucoma, generated by confocal laser scanning laser tomography (Heidelberg Retina Tomograph), were independently evaluated by four experienced glaucoma specialists, and the interobserver variability was calculated. A second separate review by the same observers included the use of clinical stereoscopic color optic nerve head photographs to aid definition of the optic disk margin. RESULTS: Optic disk parameters with the smallest interobserver variation were cup shape measure, maximum cup depth, height variation contour, and mean height contour. The intraobserver variation of these parameters did not increase when clinical optic disk slides were additionally available. Parameters with the highest interobserver variation were volume below surface, volume below reference, volume above surface, and volume above reference. The observer variation of these optic disk parameters increased significantly for two of the four examiners when clinical optic disk slides were additionally available for outlining the optic disk margin. CONCLUSION: Confocal laser scanning tomography of the optic nerve head can be improved significantly if clinical optic disk photographs are additionally available to help in outlining the optic disk margin. Because interobserver variation in the tomographic optic disk measurements can be significant, even if experienced observer are involved, tomographic optic disk measurements may be centralized in reading centers in the case of multicenter studies.

Identifying early glaucomatous changes: Comparison between expert clinical assessment of optic disc photographs and confocal scanning ophthalmoscopy

Objective To compare the ability of expert clinicians, using qualitative assessment of stereoscopic optic disc photographs, and confocal scanning laser ophthalmoscope imaging to discriminate between healthy persons and patients with early glaucoma. Design Comparative instrument validation study. Participants Seventy-two healthy persons and 51 patients with early glaucoma (average visual field mean deviation, −3.6 dB). Early glaucoma was defined as a history of ocular hypertension and a reproducible visual field defect scoring 5 or less in the Advanced Glaucoma Intervention Study classification, regardless of optic disc appearance. Intervention Stereoscopic optic nerve head (ONH) photography and Heidelberg Retina Tomograph (HRT) imaging, (Heidelberg Engineering GmbH, Dossenheim, Germany). Main outcome measures Ability of clinical assessment of stereoscopic ONH photographs and analysis of HRT parameters, taking into account the optic disc size, to detect early glaucomatous optic disc changes. Results The specificity of the majority opinion of five observers to detect early glaucomatous optic disc changes was 94.4%, with a sensitivity of 70.6%. Using the HRT analysis, the specificity was 95.8% and the sensitivity was 84.3%. Conclusions Heidelberg Retina Tomograph image analysis that takes into account the optic disc size is more sensitive than clinical assessment of stereoscopic optic disc photographs in distinguishing between healthy persons and patients with early glaucoma.

IMAGING OF THE OPTIC NERVE HEAD AND NERVE FIBER LAYER IN GLAUCOMA

Glaucoma is an optic neuropathy in which irreversible loss of ganglion cells may precede the development of visual field defects and visible optic nerve changes. The diagnosis and management of glaucoma depends on accurate and reliable intraocular pressure (IOP) measurements, visual field analysis, and optic nerve head (ONH) evaluations. The ONH appearance has been used by clinicians since the time of Helmholtz and von Graefe to assess the status of glaucoma; however, the interpretation of the ONH is subjective, and there is wide variation among observers and even among examinations by the same observer. 52,63,73 Stereoscopic ONH photography is one of the simplest technologies that can be used by the clinician, and its utility is extremely high. The cost is relatively low, and stereoscopic ONH photographs permit objective recording of the ONH appearance. 63 These photographs allow the clinician to compare the appearance of the ONH in three dimensions between clinic visits. Despite the low cost and high utility, the Baltimore Eye Study 74 illustrated the potential problem of photography in that high quality stereoscopic photographs could not be obtained in 47% of the glaucoma patients and 22% of normal subjects. Furthermore, stereoscopic ONH photography does not provide a truly objective system for interpretation of ONH appearance and change over time. ONH analyzers preceded the development of the confocal scanning laser ophthalmoscope (CSLO). The ONH analyzers were a necessary first step, but variability and lack of resolution as well as high cost eliminated nearly every device of this type including the Rodenstock Optic Nerve Head Analyzer (G. Rodenstock Instrument GmbH, Postfuch, Germany), Humphrey Retinal Analyzer, and the PAR IS 2000/Topcon IMAGEnet. Even the Glaucoma-Scope, which produced better reproducibility than its predecessors at a relatively low cost, is no longer commercially available. In an era of skepticism but great promise, most still consider visual field testing to be the reference standard, but the earliest visual field defect may indicate as much as 40% ganglion cell death. 59 In addition, automated perimetry is a subjective psychophysical test that demands a high degree of performance for a long period and may not suit those individuals who may have advanced visual, mental, or physical deficits. Therefore, much attention has been placed on developing technology to assist in the early detection and progression of glaucoma. The purpose of this review is to give a brief yet comprehensive look at the technology and literature available to image the optic nerve head and the nerve fiber layer in glaucoma. Much of the current literature concerns the Heidelberg Retina Tomograph ([HRT], Heidelberg Engineering GmbH, Heidelberg, Germany), the Nerve Fiber Analyzer or GDx, and Optical Coherence Tomography (Humphrey Systems Inc, Dublin, CA). Consistent with the past, many new methods such as retinal thickness mapping, multifocal electroretinography (ERG), and pattern ERG have appeared trying to prove themselves, whereas the existing devices are constantly being updated with new knowledge and attempts to increase utility.

Accuracy of scanning laser polarimetry in the diagnosis of glaucoma.

To determine the diagnostic accuracy of scanning laser polarimetry. A total of 95 healthy subjects and 102 patients with glaucoma met all inclusion criteria. Data collected on each participant included an automated visual field examination, stereoview optic nerve head photographs, intraocular pressure measurement, and a screening and full scanning laser polarimetry study. Each participant was classified as "normal," "glaucoma," or "uncertain" by each of 3 ophthalmologists based on all available clinical information, with the exception of the scanning laser polarimetry results. Before data analysis, 4 diagnostic algorithms for the full-test mode and 2 for the screening mode were chosen to be evaluated for their sensitivity and specificity in detecting glaucoma. Of the 4 algorithms tested for the full-test mode, "the number" (abnormal test score, >35) had sensitivities of 57%, 71%, and 81% for early, moderate, and severe glaucoma, respectively. Specificity was 89%. For the screening test, sensitivities were much lower, particularly for those with severe glaucoma damage. Scanning laser polarimetry can help to differentiate subjects with normal findings from patients with glaucomatous damage. Even the best algorithm tested, however, failed to detect a substantial number of subjects with severe damage. Further study is needed before scanning laser polarimetry can be recommended as a screening method for glaucoma.

Agreement in Assessing Glaucomatous Discs in a Clinical Teaching Setting with Stereoscopic Disc Photographs, Planimetry, and Laser Scanning Tomography

Agreement between three observers--two recently trained fellows and their supervisor--was measured using estimations of cup/disc ratio from stereoscopic optic nerve head photographs and planimetric measurements of cup/disc ratio. Agreement between the clinicians' planimetric measurements of cup/disc ratio and laser scanning tomographic measurements of cup/disc ratio also was assessed. From 16 stereoscopic optic nerve head photographs of 16 subjects, the three observers performed clinical estimations of horizontal and vertical cup/disc ratios and planimetric measurements of cup/disc ratios. Interobserver agreement was measured using intraclass correlation coefficients (ICCs). Agreement between the planimetric cup/disc ratios and laser scanning tomographic cup/disc ratios obtained with the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) also was measured using ICCs. The difference between the planimetric and HRT cup/disc ratios was calculated. The agreement between observers for clinical estimations from stereoscopic optic nerve head photographs (ICC = 0.74 horizontally and 0.83 vertically) was substantial. Agreement between the observers' planimetric measurements of cup/disc ratio was substantial (ICC = 0.79). Agreement between HRT cup/disc ratio and each observer's planimetric cup/disc ratio was moderate (ICC = 0.57-0.65), with large confidence intervals. The cup/disc ratio measured with HRT was an average of 0.07 to 0.11 larger than the planimetric cup/disc ratio. Substantial agreement between observers can be achieved when estimating cup/disc ratio with stereoscopic optic nerve head photographs and with planimetric measurements of cup/disc ratios, provided there is a standard protocol and sufficient training period. Good agreement is critical in a teaching institution to ensure accurate follow-up care of patients with glaucoma, especially if patients are examined by different clinicians. Laser scanning tomography is a more repeatable and objective method, which may provide further standardization of optic nerve head assessments. Future studies will determine the reference plane that optimizes agreement between the HRT findings and each clinician's estimations.

A third locus (GLC1D) for adult-onset primary open-angle glaucoma maps to the 8q23 region

Purpose: Two genes for adult-onset primary open-angle glaucoma have been mapped to chromosomes 2cen-q13 and 3q21-q24. We studied a family with adult-onset primary open-angle glaucoma in which the disease did not map to these two chromosomal regions. Methods: We ascertained a four-generation family with adult-onset primary open-angle glaucoma in which the disease status of individuals was objectively assigned using defined criteria. Complete ophthalmologic examinations, visual field testing, optic nerve head photographs, and venous blood samples were obtained. Family members were genotyped using polymerase chain reaction amplification of microsatellite polymorphic markers. Linkage analysis was performed and lod scores were calculated. Haplotype transmission data were analyzed. Results: A total of 20 subjects in three successive generations agreed to participate in the study. This included samples from eight affected subjects, one glaucoma suspect, one normal individual, and two spouses in generations II and III, and an additional eight individuals in generation IV. The phenotype in this family appears to be variable, with onset of visual field loss in middle age, followed by modest elevation of intraocular pressure and progression of the disease in older individuals. Linkage was established with a group of DNA markers located in the 8q23 region. A lod score value of 3.61 was obtained using marker D8S1471. Three other markers from the same region gave lod score values of over 3.0. Haplotype transmission data identified two recombination events that placed the gene in a 6.3-cM region flanked by D8S1830 and D8S592. The disease-bearing haplotype was inherited by eight affected subjects and three glaucoma suspects. Conclusion: We present evidence for a third adult-onset primary open-angle glaucoma locus (GLC1D) on chromosome 8q23. The genetic heterogeneity of adult-onset glaucoma is evident from the multiplicity of chromosomal loci associated with this disease.

Effect of optic nerve head drusen on nerve fiber layer thickness

Objective The purpose of the study was to evaluate the effect of optic nerve head drusen (ONHD) on nerve fiber layer (NFL) thickness by visual field testing, red-free photography of NFL, and optical coherence tomography (OCT). Design The study design was a prospective clinical study. Participants Twenty-three eyes of 15 consecutive patients with ONHD and 27 eyes of 27 age-matched control subjects participated. Intervention Ophthalmologic examination, color and red-free photography, automated Humphrey visual field testing, and OCT were performed. Each of the drusen study eyes were graded on a scale of 0 to III based on the amount of visible ONHD. Grade 0 represented the absence of clinically visible ONHD, and grade III represented an optic nerve head with abundant drusen. Main outcome measures Findings from clinical evaluation and color optic nerve head photographs and NFL evaluation by red-free photography, visual fields, and OCT were measured. Results The number of study eyes with visual field defects increased with the higher grade drusen discs, corresponding both with progressively thinner NFL measurements by OCT and NFL loss shown by NFL photography. The NFL evaluation showed NFL thinning by red-free photography in 12 (71%) of 17 eyes with visible drusen (grades I–III discs) and visual field defects in 9 (53%) of 17 eyes in this group. By OCT measurements, the superior and inferior NFLs were significantly thinner in the eyes with visible ONHD compared with those of control eyes in the superior quadrant ( P < 0.001) and inferior quadrant ( P = 0.004). Compared with grade 0 discs, grades I through III discs showed statistically significant thinning of the NFL superiorly ( P < 0.001). No statistical significant thinning of the NFL was seen in grade 0 discs compared with those of control subjects. Conclusions Optical coherence tomography is able to detect NFL thinning in eyes with ONHD and appears to be a sensitive and early indicator of NFL thinning. Increased numbers of clinically visible ONHD correlated with NFL thinning shown by OCT measurements and both visual field defects and NFL loss seen by red-free photography.

P 304 Title: Computer analysis of optic nerve head photographs: The difference between real and filtered images

P 304 Title: Computer analysis of optic nerve head photographs: The difference between real and filtered images

Computer analysis of optic nerve head photographs: the difference between real and filtered images.

Computer analysis of optic nerve head photographs: the difference between real and filtered images.

Quantification of Nerve Fiber Layer Thickness in Normal and Glaucomatous Eyes Using Optical Coherence Tomography

Quantitative assessment of nerve fiber layer (NFL) thickness in normal and glaucomatous eyes, and correlation with conventional measurements of the optic nerve structure and function. We studied 59 eyes of 33 subjects by conventional ophthalmologic physical examination, Humphrey 24-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. Nerve fiber layer thickness as measured by optical coherence tomography demonstrated a high degree of correlation with functional status of the optic nerve, as measured by visual field examination (P = .0001). Neither cupping of the optic nerve nor neuroretinal rim area were as strongly associated with visual field loss as was NFL thickness (P = .17 and P = .21, respectively). Cupping correlated with NFL thickness only when the cup was small (cup-to-diameter ratio, 0.1 to 0.3) or large (cup-to-diameter ratio, 0.8 to 1.0) (P = .006); there was no correlation between cupping and NFL thickness otherwise. Nerve fiber layer, especially in the inferior quadrant, was significantly thinner in glaucomatous eyes than in normal eyes (P = .04). Finally, we found a decrease in NFL thickness with aging, even when controlling for factors associated with the diagnosis of glaucoma (P = .03). Nerve fiber layer thickness can be measured using optical coherence tomography. These measurements provide good structural and functional correlation with known parameters.

Foveal Flicker Sensitivity Abnormalities in Early Glaucoma

This study tested the hypothesis that (a) evidence of foveal visual dysfunction could be elicited in glaucoma subjects by measuring flicker sensitivity as a function of time after onset of an adapting field for a suitably chosen set of test and adaptation parameters and that (b) such dysfunction would be related to high blood pressure. Three groups of subjects were tested: (a) subjects with primary open-angle glaucoma but only minimal field loss, (b) normal control subjects, and (c) control subjects found to be suspect for glaucoma. The protocol included measurement of pulse rate and blood pressure, administration of Humphrey 30-2 visual fields and optic nerve head photography, and administration of a battery of psychophysical tests in Maxwellian view. This battery included a test of flicker sensitivity measured at middle wavelengths as a dynamic function of time after onset of a long-wavelength adapting field. The dynamic light-adaptation functions of subjects with glaucoma were much more likely to be unstable than were the corresponding functions of normal subjects. In addition, the dynamic light-adaptation functions of subjects with high blood pressure for their pulse rate were significantly less stable than the correspond ing functions of subjects without high blood pressure for their pulse rate. Moreover, the ratio of mean arterial pressure to pulse rate was significantly less for normal subjects than for either glaucoma subjects or for glaucoma-suspect subjects. We infer that among people with primary open-angle glau coma but with only minimal field loss, there often is foveal dysfunction associated with cardiovascular disease. Evidence of such dysfunction appears to require the use of stimulus conditions that tax the ability of the visual system to respond appropriately.

Intra- and inter-observer variation of optic nerve head measurements in glaucoma suspects using disc-data.

The aim of this study was to determine the intra- and inter-observer variation in the use of a system designed for exact measurements from standard optic nerve head photographs. The commercially available system consisted of a colour CCD Videocamera, a dedicated frame grabber and customized software run on a IBM AT compatible computer. Masked measurements were made 3 times by 2 observers, from stereophotographs of the optic nerve head of 56 eyes from 30 glaucoma suspects. The cup was defined on the basis of contour, not pallor and the disc area was defined as the area inside Elschnig's ring. Intra-observer variances were 0.001 +/- 0.001 mm2 for cup area (mean +/- SD), 0.002 +/- 0.002 mm2 for disc area and 0.002 +/- 0.003 mm2 for rim area. These values for intra-observer variance were comparable with the results obtained using manual planimetric techniques. Intra-observer variance for disc area was significantly larger for the less trained of the two experienced observers. Inter-observer variances were 0.004 +/- 0.009 mm2 for cup area, 0.008 +/- 0.013 mm2 for disc area and 0.009 +/- 0.014 mm2 for rim area. These inter-observer variances were significantly larger than those previously reported for manual planimetry. The absolute differences between the two observers ranged from -0.35 to +0.20 mm2 (-0.08 +/- 0.11 mm2) for cup area, from -0.38 to +0.15 mm2 (-0.08 +/- 0.11 mm2) for disc area and from -0.29 to +0.34 mm2 (-0.06 +/- 0.12 mm2) for rim area.(ABSTRACT TRUNCATED AT 250 WORDS)

Digital Measurement of Pallor-Disc Ratio

In an effort to quantitate optic nerve head pallor, a method has been devised to measure pallor-disc ratio using optic nerve head photographs. After electronically scanning photographs through various Wratten filters, it was observed that a red filter produces good contrast between the disc and the retinal surface, while a green filter produces good contrast between the pale area of the disc and the remaining normal-appearing nerve head. A computer program fitted an elliptical form to both the disc region of red image and the pale area of green image. Pallor-disc ratios were calculated on both area and radial bases. Reproducibility of 3.5% for the area ratios and 7% for the radial ratios were obtained.