Clinical evaluation of multiparameter correction equations for Goldmann applanation tonometry.

PURPOSE: To evaluate and compare the multiparameter equations in correcting intraocular pressure (IOP) measurements obtained using the Goldmann applanation tonometer (IOPG) for the effects of central corneal thickness (CCT), corneal curvature (R), and age in different ethnic populations. METHODS: Data of IOPG, CCT, R, and age were collected from three clinical centers. The sample size consisted of 945 eyes of 945 glaucoma patients or suspects (669 Europeans, 127 African Americans, and 149 Indians). The 'corrected IOP' was calculated using five multiparameter equations to decrease the association of CCT, R, and age with measured IOP. Regression analyses were performed to calculate variance (r(2)) and determine the association of CCT, R, and age with IOPG and corrected IOP (residual association). RESULTS: Overall, CCT accounted for the majority of variance in IOPG, while R and age had a much smaller effect, with the combined effect on IOPG ranging from 4.7 to 7.5% in the three data sets. The residual association of CCT, R, and age with corrected IOP in the three groups ranged from 0.2 to 1.3% and 0.5 to 1.8% with the application of the Elsheikh and the Chihara equations, respectively. The residual association of CCT, R, and age with corrected IOP calculated using the Ehlers, Orssengo and Pye, and Shimmoyo equations were 7-11.5, 1.8-11.7, and 4.6-8.3%, respectively. CONCLUSION: The Elsheikh and the Chihara equations better decreased the association of CCT, R, and age with measured IOP than the Ehlers, Orssengo and Pye, and Shimmoyo equations.

A preliminary longitudinal study of the retinal nerve fiber layer in progressive multiple sclerosis.

Thinning of the retinal nerve fiber layer (RNFL) of clinically unaffected eyes is seen in patients with multiple sclerosis (MS). It is uncertain when this thinning occurs, and whether ongoing RNFL loss can be measured over time with optical coherence tomography (OCT). Using time-domain OCT, we studied 34 patients with progressive MS (16 primary progressive MS, 18 secondary progressive; 14 male; 20 female; mean age at study entry 51 years; median EDSS 6; mean disease duration at study entry 12 years) on two occasions with a median interval of 575 (range 411-895) days apart. Eighteen healthy controls (10 male; eight female; mean age at study entry 46 years) were also studied twice, with a median interval of 656 days (range 398-890). Compared to controls, the patients had significant decreases in the RNFL thickness and macular volume of their clinically unaffected eyes at study entry. No significant decrease in RNFL thickness was observed between baseline and follow-up in either patients or controls. Macular volume declined significantly in patients and controls, but there was no difference in this change between the two groups. The study findings suggest that time domain OCT detects little disease-related ongoing loss of retinal axons in progressive forms of MS and has limited use for monitoring potential neuroprotective therapies at this stage of disease. Further studies are needed using higher-resolution OCT systems and in larger groups of patients, to elucidate the timing and mechanism of RNFL loss that is observed in clinically unaffected nerves in MS.

HRT-3 Moorfields reference plane: effect on rim area repeatability and identification of progression.

AIMS: To assess the effect of the Moorfields Reference Plane on Heidelberg Retina Tomograph (HRT) rim area repeatability and its effect on progression rates using an event analysis. METHODS: The HRT reference plane (RP) defines structures above as "rim" and below as "cup." The Moorfields RP applies the Standard RP (located 50 microm posterior to the temporal disc margin) at baseline and maintains the distance between the Standard RP and the reference ring (located in the image periphery) for follow-up images. The Moorfields RP was applied to an HRT test-retest dataset, and rim area repeatability coefficients were calculated. Repeatability coefficients were compared between the Moorfields, Standard and 320 (located 320 microm posterior to the reference ring) RPs. The Moorfields RP was applied to HRT images from 198 ocular hypertensives, acquired over 6 years. HRT progression required rim area baseline/follow-up differences exceeding the repeatability coefficient in two or more sectors, with confirmation in at least one of two consecutive images. Field progression was assessed using Advanced Glaucoma Intervention Study criteria. RESULTS: The Moorfields RP improved rim area repeatability compared with the Standard RP; repeatability was similar between the Moorfields and the 320 RP. The frequency of identified progression using Moorfields RP was 40% compared with 28% for the 320 RP. There was a greater percentage with concurrent field progression -15.1% (Moorfields RP) compared with 12.1% (320 RP). CONCLUSIONS: Although rim area repeatability was similar using the 320 RP and the Moorfields RP, the latter resulted in greater rates of detection of change.

The morphology of the optic nerve head in the Singaporean Chinese population (the Tanjong Pagar study): part 1--Optic nerve head morphology.

BACKGROUND/AIMS: To investigate the correlation between optic disc parameters and their association with demographic variables in a Chinese population. METHODS: Disc data were obtained from 929 subjects aged > or = 40 years from the Tanjong Pagar glaucoma survey of Singapore, using a novel planimetric method of sequential stereo-photographs. Biometric data (refractive error, keratometry, axial length, anterior chamber depth, lens thickness) were used to calculate ocular magnification. Camera magnification was quantified with a model eye. A "normal" dataset of 622 subjects was generated by exclusion of subjects with abnormal results on psychophysical testing, an occludable angle or an intraocular pressure > 97.5th percentile in either eye. RESULTS: Median disc area (DA), cup area (CA), and rim area (RA) were 2.09 (range 1.28-4.01) mm2, 0.69 (0.01-1.90) mm2 and 1.38 (0.82-2.50) mm2, respectively. There was strong evidence of an association between DA and RA (Spearman's rho 0.624, p<0.001). DA and RA were significantly greater in men (median DA = 2.20; range 1.30-3.56; median RA, 1.45; range 0.85-2.30) than women (median DA, 2.00; range 1.28-4.01; median RA, 1.36; range 0.82-2.49, p<0.001). DA increased with age (Spearman's rho 0.115, p = 0.004), while RA was unrelated (rho -0.041; p = 0.308). CONCLUSIONS: The morphometric characteristics of optic discs in Chinese Singaporeans are very similar to those described in other groups, with the temporal sector rim having the smallest area. Disc and rim areas vary with sex (men > women). Disc area (but not that of the rim) increases with age.

The morphology of the optic nerve head in the Singaporean Chinese population (the Tanjong Pagar study): part 2--Biometric and systemic associations.

BACKGROUND/AIMS: To investigate the association of biometric and systemic variables with optic disc characteristics in Chinese Singaporean adults. METHODS: Ocular, biometric and medical data including intraocular pressure, refractive error, keratometry, axial length (AL), anterior chamber depth, corneal and lens thickness as well as optic disc data (using planimetry of stereo-photographs) were obtained from 622 normal subjects aged > or = 40 years from the Tanjong Pagar glaucoma survey of Singapore. RESULTS: Disc area (DA) was positively associated with AL and height but was unrelated to corneal thickness. Following adjustment for IOP and sex, DA remained positively associated with AL, height and age. Neuroretinal rim area (RA) was also significantly and positively associated with AL and also with height. RA was negatively associated with IOP and was unrelated to blood pressure, history of diabetes, myocardial infarction, stroke or migraine. CONCLUSIONS: These data on a Chinese Singaporean population identify height and axial length of the globe as significantly associated with rim area of the disc. These features should be taken into account in statistical assessments of optic nerve head morphometry. This may improve the discriminative ability of image analysis to detect glaucomatous changes. In addition, we identified a statistically significant but small inverse association between rim area and IOP within the normal statistical range.

Practical recommendations for measuring rates of visual field change in glaucoma.

To date, there has been a lack of evidence-based guidance on the frequency of visual field examinations required to identify clinically meaningful rates of change in glaucoma. The objective of this perspective is to provide practical recommendations for this purpose. The primary emphasis is on the period of time and number of examinations required to measure various rates of change in mean deviation (MD) with adequate statistical power. Empirical data were used to obtain variability estimates of MD while statistical modelling techniques derived the required time periods to detect change with various degrees of visual field variability. We provide the frequency of examinations per year required to detect different amounts of change in 2, 3 and 5 years. For instance, three examinations per year are required to identify an overall change in MD of 4 dB over 2 years in a patient with average visual field variability. Recommendations on other issues such as examination type, strategy and quality are also made.

Optic nerve magnetization transfer imaging and measures of axonal loss and demyelination in optic neuritis.

Magnetization transfer imaging is an MRI technique that provides quantitative information about in vivo tissue integrity, including myelin and axonal content, and is expressed as the magnetization transfer ratio (MTR). The optic neuritis lesion can model the MS lesion in vivo and permits use of non-invasive markers of optic nerve myelination (visual evoked potential [VEP] latency) and retinal neuroaxonal loss (optical coherence tomography [OCT]) to provide further information about the in vivo substrates of optic nerve MTR. Twenty-five patients with optic neuritis were studied using an optic nerve MTR sequence, quantitative visual function testing, VEPs and OCT, along with 15 controls. MTR was reduced in affected nerves compared to both clinically unaffected nerves from patients and control nerves (P < 0.001). Whole-nerve MTR correlated modestly with central-field VEP latency but more strongly when lesion-only MTR was measured, when a modest correlation with whole-field VEP latency emerged. OCT-quantified retinal neuroaxonal loss also correlated with MTR. In conclusion, markers of optic nerve myelination and axonal loss both correlate with optic nerve MTR. Because axonal loss following optic neuritis also results in myelin loss, the relative contributions of the two pathological conditions to the MTR measures cannot be estimated from this study.

Quantification of optic nerve head topography in optic neuritis: a pilot study.

AIMS: To investigate optic nerve head topography in patients with optic neuritis compared to controls using the Heidelberg retina tomograph-II (HRT-II) and to determine if detected changes are related to visual function and electrophysiology. METHODS: 25 patients with a previous single episode of unilateral optic neuritis and 15 controls were studied with HRT-II, visual evoked potentials, and pattern electroretinogram. Patients also had testing of visual acuity, visual field, and colour vision. RESULTS: In affected eyes compared to fellow eyes, there was reduction of both the mean retinal nerve fibre layer (RNFL) thickness at the disc edge (p = 0.009) and the neuroretinal rim volume (p = 0.04). In affected eyes compared to control eyes, the three dimensional optic cup shape measure was increased (p = 0.01), indicative of an abnormal cup shape. There were no other significant differences in HRT-II measures. Within patient interocular difference correlation was used to investigate the functional relevance of these changes and demonstrated associations between RNFL thickness change and changes in visual acuity, visual field, and colour vision. Colour vision change was also associated with change in neuroretinal rim volume. CONCLUSIONS: HRT detects functionally relevant changes in RNFL thickness and neuroretinal rim volume between eyes affected by optic neuritis and unaffected fellow eyes.

The relative effects of corneal thickness and age on Goldmann applanation tonometry and dynamic contour tonometry.

AIMS: To establish the effects of central corneal thickness (CCT) on intraocular pressure (IOP) measured with a prototype Pascal dynamic contour tonometer (DCT), to evaluate the effect of CCT and age on the agreement between IOP measured with the Pascal DCT and Goldmann applanation tonometer (GAT), and to compare the interobserver and intraobserver variation of the DCT with the GAT. METHODS: GAT and DCT IOP measurements were made on 130 eyes of 130 patients and agreement was assessed by means of Bland-Altman plots. The effect of CCT and age on GAT/DCT IOP differences was assessed by linear regression analysis. Interobserver and intraobserver variations for GAT and DCT were assessed in 100 eyes of 100 patients. RESULTS: The mean difference (95% limits of agreement) between GAT and DCT was -0.7 (-6.3 to 4.9) mm Hg. GAT/DCT IOP differences increased with thicker CCT (slope 0.017 mm Hg/microm, 95% CI 0.004 to 0.03, r2 = 0.05, p = 0.01), and with greater age, slope 0.05 mm Hg/year (95% CI 0.012 to 0.084, r2 = 0.05, p = 0.01). The intraobserver variability of GAT and DCT was 1.7 mm Hg and 3.2 mm Hg, respectively. The interobserver variability was (mean difference (95% limits of agreement)) 0.4 (-3.5 to 4.2) mm Hg for GAT and 0.2 (-4.9 to 5.3) mm Hg for DCT. CONCLUSIONS: GAT is significantly more affected than DCT by both CCT and subject age. The effect of age suggests an age related corneal biomechanical change that may induce measurement error additional to that of CCT. The prototype DCT has greater measurement variability than the GAT.

Factors affecting the test-retest variability of Heidelberg retina tomograph and Heidelberg retina tomograph II measurements.

AIMS: To evaluate the test-retest variability of stereometric parameter measurements made with the Heidelberg retina tomograph (HRT) and Heidelberg retina tomograph-II (HRT-II), and to establish which parameter(s) provided the most repeatable and reliable measurements with both devices. An investigation into the factors affecting the repeatability of the measurements of this parameter(s) was conducted. METHODS: 43 ocular hypertensive and 31 glaucoma subjects were recruited to a test-retest study. One eye from each subject underwent HRT and HRT-II imaging by two observers on each of two occasions within 6 weeks of each other. Lens grading was carried out by LOCS III grading and Scheimpflug camera generated densitogram analysis. RESULTS: Rim area (RA) and mean cup depth measurements were found to be least variable. Both inter-test reference height difference and image quality had a strong relation (R(2)>0.5, p<0.0001) with inter-test RA difference and, together, are responsible for 70% of RA measurement variability. Image quality was influenced by lens opacity, cylindrical error, and age. Inter-test RA measurement differences were unrelated to the observer or visit interval. CONCLUSIONS: RA represents an appropriate measure for monitoring glaucomatous progression. Reference height difference and image quality were the factors that most influenced RA measurement variability. Image analysis strategies that address these factors may reduce test-retest variability.

Improving the repeatability of Heidelberg retina tomograph and Heidelberg retina tomograph II rim area measurements.

AIMS: To devise and test strategies for improving Heidelberg retina tomograph (HRT and HRT-II) rim area (RA) repeatability and assess the benefit of the strategies in time series of HRT images. METHODS: The effect of the standard and 320 microm reference planes and image quality on RA repeatability was assessed in a test-retest HRT image dataset from 74 subjects. A longitudinal HRT image dataset from 30 ocular hypertensive subjects was analysed by linear regression of RA over time, with each of the reference planes and using a manual image alignment facility. RA variability was estimated by comparing the standard deviation of residuals (RSD) generated by each linear regression. RESULTS: RA repeatability was better with the 320 microm reference plane (repeatability coefficient 0.17 mm(2)), improving further with only good quality images (repeatability coefficient 0.08 mm(2)). For the longitudinal data, a significant (p<0.0001) reduction in the RSD from 0.10 to 0.05 mm(2) was obtained with the 320 microm reference plane. Manual alignment led to a further significant (p<0.0001) reduction in the RSD to 0.04 mm(2). CONCLUSIONS: The findings support the use of a 320 microm reference plane and manual image alignment to analyse RA over time. The estimates of RA repeatability may be used to define thresholds for glaucomatous change.

Interobserver agreement on visual field progression in glaucoma: a comparison of methods.

AIM: To examine the level of agreement between clinicians in assessing progressive deterioration in visual field series using two different methods of analysis. METHODS: Each visual field series satisfied the following criteria: more than 19 reliable fields, patient age over 40 years, macular threshold at least 30 dB. The first three fields in each series were excluded to minimise learning effects: the following 16 were studied. Five expert clinicians assessed the progression status of each series using both standard Humphrey printouts and pointwise linear regression (PROGRESSOR). The level of agreement between the clinicians was evaluated using a weighted kappa statistic. RESULTS: A total of 432 tests comprising 27 visual field series of 16 tests each were assessed by the clinicians. The level of agreement on progression status between the clinicians was always higher when they used PROGRESSOR (median kappa = 0.59) than when they used Humphrey printouts (median kappa = 0.32). This was statistically significant (p = 0.006, Wilcoxon matched pairs signed rank sum test). CONCLUSIONS: Agreement between expert clinicians about visual field progression status is poor when standard Humphrey printouts are used, even when the field series studied are long and consist solely of reliable fields. Under these ideal conditions, clinicians agree more closely about patients' visual field progression status when using PROGRESSOR than when inspecting series of Humphrey printouts.

Variability across the optic nerve head in scanning laser tomography.

AIM: To characterise measurement variability in scanning laser tomography of the optic nerve head. METHODS: 21 normal and 21 glaucoma subjects underwent same and separate day test-retest Heidelberg retina tomograph imaging by the same and different operators. RESULTS: Rim area was most reproducible among parameters. Its variability tended to be highest temporally and increased (p<0.05) with testing involving different operators and visits. Nature of regional variability differed between glaucoma and normal eyes and between standard and 320 micro m reference planes. CONCLUSIONS: Rim area is reproducible and potentially useful as a marker of progression. Pattern of variability and the influence of different reference planes, disease, operators, and visits should be considered when evaluating progression.

The phenotype of normal tension glaucoma patients with and without OPA1 polymorphisms.

AIM: Polymorphisms in OPA1, the gene responsible for autosomal dominant optic atrophy, were recently found to be strongly associated with normal tension glaucoma (NTG). The aim of this study was to determine whether OPA1 polymorphisms affect the phenotype of NTG patients. METHODS: A retrospective analysis was performed of 108 well characterised NTG patients who had been genotyped for OPA1 variations, and who had previously undergone automated perimetry and Heidelberg retina tomography (HRT). 25 NTG patients had the at-risk OPA1 genotype (IVS 8 +4 C/T; +32 T/C) and 83 NTG patients did not. Differences between groups were sought in a wide range of structural, psychophysical, and demographic factors. These included sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, laterality of glaucoma, presenting and highest diurnal intraocular pressure (IOP), initial cup-disc (CD) ratio, baseline visual field global indices, and optic disc parameters as measured by HRT. For a subgroup of patients with at least 5 years of follow up and 10 visual field tests, pointwise linear regression analysis (PROGRESSOR for Windows software) was applied to the visual field series. RESULTS: There was no significant difference in the two groups with respect to sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, or laterality of glaucoma. The comparison of IOP, CD ratio and visual field global indices, MD and CPSD in the two groups showed no significant difference. There were no differences in the mean values for any of the HRT parameters analysed. For the subgroup of patients with at least 5 years of follow up, there was also no significant difference in the number of patients with progressing locations, the mean number of progressing locations per subject, the mean slope of the progressing locations or the mean slope for whole visual field. CONCLUSIONS: The absence of phenotypic differences in normal tension glaucoma patients with and without the OPA1 polymorphisms IVS 8 +4 C/T; +32 T/C suggest that these OPA1 polymorphisms do not underlie any major phenotypic diversity in these patients.

Effect of treatment by medicine or surgery on intraocular pressure and pulsatile ocular blood flow in normal-pressure glaucoma.

PURPOSE: To study the effect of trabeculectomy and monotherapy with topical betaxolol, brimonidine and latanoprost on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in patients with normal-pressure glaucoma (NPG). METHODS: In this retrospective study NPG patients attending the glaucoma research unit at Moorfields Eye Hospital were reviewed. Patients treated by surgery or topical medication (betaxolol, brimonidine or latanoprost) who had pre- and post-treatment IOP and POBF measurements were studied. For those patients who were having treatment to both eyes, one eye was selected at random for analysis. RESULTS: A total of 147 patients were reviewed. Forty-three eyes were receiving betaxolol 0.5%, 58 eyes latanoprost 0.005%, 23 eyes brimonidine 0.2% and 23 eyes had undergone trabeculectomy surgery. There were more female than male patients in all four groups, and the groups were similar with regards age. Pre-treatment IOP and POBF values were similar among the groups ( P=0.27, P=0.08 respectively). Post-treatment IOP values tended to be lower than pre-treatment values for all four groups. All groups had an increased POBF except for betaxolol, where POBF decreased. CONCLUSION: Patients treated by trabeculectomy and those receiving topical latanoprost and brimonidine had lower IOP and higher POBF following treatment. The betaxolol-treated group, despite a slight decrease in IOP, had a decreased POBF. Lowering IOP by treatment may not necessarily be associated with an increase in POBF.

Use of high spatial resolution perimetry to identify scotomata not apparent with conventional perimetry in the nasal field of glaucomatous subjects.

AIM: To examine whether high spatial resolution perimetry (HSRP) could identify fine scale scotomata which may not be apparent with conventional perimetry. The HSRP was performed in the nasal field, as this location is a recognised site for the early occurrence of glaucomatous defects. METHOD: 16 early glaucoma eyes, 17 glaucoma suspect eyes, and 20 age matched healthy control eyes underwent conventional automated perimetry using the 24-2 program of the Humphrey field analyser (HFA) and HSRP. The HSRP was performed in the nasal field by testing 9 x 9 degrees of 100 tested points separated by 1 degree and the results compared with the HFA 24-2 program. RESULTS: Mean HSRP thresholds were significantly abnormal in the suspect and glaucoma eyes, with elevated levels of asymmetry between the superior and inferior nasal field. Overall, 7/17 (41%) suspect eyes (95% confidence interval 5/17 (29%) to 7/17 (41%)) had nasal scotomata on HSRP, although their HFA 24-2 fields failed to identify any defects. In glaucomatous eyes, 15/16 (94%) eyes had HSRP scotomata (95% CI 14/16 (88%) to 15/16 (94%)). In 12 these coexisted with HFA 24-2 defects at the same location, while in three eyes only HSRP identified scotomata in the nasal field. CONCLUSION: HSRP can identify scotoma in glaucomatous eyes in the nasal field which may be missed with the lower spatial resolution of conventional perimetry.

Glaucomatous optic disc changes in the contralateral eye of unilateral normal pressure glaucoma patients.

OBJECTIVE: To evaluate the optic disc for structural abnormalities in the contralateral eye of unilateral normal pressure glaucoma patients. DESIGN: Cross-sectional study. PARTICIPANTS: Fifty-three unilateral normal pressure glaucoma patients. TESTING: Optic disc imaging with the Heidelberg Retina Tomograph (HRT). MAIN OUTCOME MEASURES: Optic disc structural parameters. RESULTS: Of the contralateral (normal visual field) eyes, 79.2% were found to have an abnormal optic disc by HRT analysis. Of the glaucomatous (abnormal visual field) eyes, 94.3% were found to have an abnormal disc. The patterns of disc abnormality were defined as marked or moderate diffuse thinning of the neuroretinal rim (NRR) or broad or narrow focal thinning of the NRR. The most common pattern in the contralateral eyes was moderate diffuse thinning of the NRR (45.2%). The most frequently abnormal segments were the nasal superior (73. 8%) followed by the nasal inferior and the global NRR parameter (both 54.8%). CONCLUSIONS: A high frequency of NRR thinning was found in the contralateral (normal visual field) eyes of unilateral normal pressure glaucoma patients by HRT analysis. Knowing whether these abnormalities predict future progression to the development of visual field abnormality must wait until longitudinal studies are completed. If a disc abnormality is shown to predict future field loss, then early identification will allow early treatment.

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.

Mapping the visual field to the optic disc in normal tension glaucoma eyes.

PURPOSE: To establish the anatomical relationship between visual field test points in the Humphrey 24-2 test pattern and regions of the optic nerve head (ONH) DESIGN: Cross-sectional study. PARTICIPANTS: Glaucoma patients and suspects from the Normal Tension Glaucoma Clinic at Moorfields Eye Hospital. METHODS: Sixty-nine retinal nerve fiber layer (RNFL) photographs with well-defined RNFL defects and/or prominent bundles were digitized. An appropriately scaled Humphrey 24-2 visual field grid and an ONH reference circle, divided into 30 degrees sectors, were generated digitally. These were superimposed onto the RNFL images. The relationship of visual field test points to the circumference of the ONH was estimated by noting the proximity of test points to RNFL defects and/or prominent bundles. The position of the ONH in relation to the fovea was also noted. MAIN OUTCOME MEASURES: The sector at the ONH corresponding to each visual field test point, the position of the ONH in relation to the fovea, and the effect of the latter on the former. RESULTS: A median 22 (range, 4-58), of a possible 69, ONH positions were assigned to each visual field test point. The standard deviation of estimations was 7.2 degrees. The position of the ONH was 15.5 degrees (standard deviation 0.9 degrees ) nasal and 1.9 degrees (standard deviation 1.0 degrees ) above the fovea. The location of the ONH had a significant effect on the corresponding position at the ONH for 28 of 52 visual field test points. CONCLUSIONS: A clinically useful map that relates visual field test points to regions of the ONH has been produced. The map will aid clinical evaluation of glaucoma patients and suspects, as well as form the basis for investigations of the relationship between retinal light sensitivity and ONH structure.