the medical records of all patients examined at the glaucoma clinic from january 2007 to march 2008 by one glaucoma specialist were reviewed , and if patients met the inclusion criteria of this study they were consecutively enrolled . all participants underwent a comprehensive ophthalmic examination , including visual acuity measurement , slit - lamp biomicroscopy , intraocular pressure measurement by goldmann applanation tonometry , central corneal thickness ultrasound pachymetry measurement , sap , matrix , gdx vcc , and oct . patients were eligible if they had a best - corrected visual acuity greater than 20/40 and a normal anterior chamber and open - angle on slit - lamp and gonioscopic examinations , respectively . participants with any other ophthalmic disease that could result in vf defects or who had histories of diabetes mellitus were excluded . a glaucomatous optic disc was defined as a disc showing increased cupping ( vertical cup - disc ratio > 0.6 ) , asymmetrical cupping ( a between - eye difference in the vertical cup - disc ratio of > 0.2 ) , diffuse or focal neural rim thinning , hemorrhage , or nerve fiber layer defects . glaucomatous eyes defined by sap ( sap group ) were those with a glaucomatous optic disc appearance and glaucomatous vf defects defined by the glaucoma hemifield test ( ght ) as outside 99% of age - specific normal limits and also with a pattern standard deviation ( psd ) outside 95% of the normal limit with the 24 - 2 full threshold program or the 24 - 2 swedish interactive threshold algorithm ( sita ) standard programs of the hfa . eyes with a glaucomatous optic disc appearance and a ght result outside 99% of the age - specific normal limits with a psd outside 95% of the normal limit with matrix were categorized by matrix as suffering from glaucoma ( matrix group ) . since there were no generalized criteria in matrix for diagnosing glaucoma , we arbitrarily applied the same criteria as in sap to the matrix results . we included only those patients who , within one month of the initial evaluation , yielded a reliable vf measurement , defined as a false - positive error < 15% , a false - negative error < 15% and a fixation loss < 20% in both sap and matrix . subsequently , 90 eyes were classified as glaucomatous in the sap group and 112 eyes were identified in the matrix group . all procedures conformed to the declaration of helsinki , and the study was approved by the ethics committee of the asan medical center . oct measures rnfl thickness with a low - coherence light source projected onto the retina . the time delay of the light backscatter from the rnfl compared with light reflected by a reference mirror is then calculated . circumpapillary rnfl was measured in the fast rnfl modeusing three 360-degree circular , high - resolution scans with a diameter of 3.4 mm that were centered on the optic disc . rnfl thicknesses of the collective quadrants ( 360 measure ) , as well as the individual temporal ( 316-45 ) , superior ( 46-135 ) , nasal ( 136-225 ) , and inferior ( 226-315 ) quadrants , were obtained for analysis . diagnostic categorization by stratus oct involves a software - based comparison of thickness parameters with an internal normative database of 328 eyes ; we also evaluated these parameters in our study . parameters on the stratus oct printout are annotated to indicate whether they fall outside of the 99% confidence interval ( ci ) , between the 95% and 99% cis ( borderline ) or within the 95% ci ( normal ) . in this study , only well - focused and centered scans with signal strengths seven were included , and a parameter was considered outside the normal limits if ci < 95% and within the normal limits if ci > 95% . slp imaging was performed in a standardized fashion ( gdx vcc software version 5.5.0 ) with a circular scan ( 3.2 mm in diameter ) centered on the optic disc . the general principles of slp with variable corneal polarization compensation ( vcc ) have been described in detail elsewhere.19 - 21 we only analyzed eyes with a scan quality score of eight or better . the slp parameters examined were tsnit ( temporal , superior , nasal , inferior , and temporal ) imaging , superior imaging , inferior average imaging , and the nerve fiber indicator ( nfi ) . the gdx vcc printout provides probabilities of abnormality based on a comparison with an internal database containing information on 540 normal eyes . in this study , a parameter was considered outside the normal limits if p<0.05 and within the normal limits if p>0.05 . for the nfi parameter , the manufacturer - suggested cutoff of < 30 was considered as within the normal limits , whereas values of 31 - 100 were considered abnormal . participants were classified based on the severity of their functional damage as assessed by sap and matrix . since no generalized criteria for categorizing glaucoma severity using matrix exists , we used the same mean deviation ( md ) values for both sap and matrix . with reference to the mean deviations of sap and matrix , each vf defect was classified as early ( no worse than -6db ) : groups s1 and m1 ; moderate ( worse than -6 db but not worse than -12db ) : groups s2 and m2 ; and advanced ( worse than -12db ) : groups s3 and m3.22 the s1 , s2 and s3 subgroups were classified according to sap severity , whereas subgroups m1 , m2 and m3 were determined by matrix severity scores . all statistical tests were performed using a statistical software package ( spss 15.0 for windows ; spss inc . , rnfl thicknesses measured by oct and gdx vcc were compared among the three groups categorized by md scores from both sap and matrix using a one - way analysis of variance ( anova ) with pairwise , post - hoc tukey comparisons . the normative classifications determined by the internal databases of the oct and gdx vcc instruments were compared among the three subgroups for each of sap and matrix using the chi - square test . the medical records of all patients examined at the glaucoma clinic from january 2007 to march 2008 by one glaucoma specialist were reviewed , and if patients met the inclusion criteria of this study they were consecutively enrolled . all participants underwent a comprehensive ophthalmic examination , including visual acuity measurement , slit - lamp biomicroscopy , intraocular pressure measurement by goldmann applanation tonometry , central corneal thickness ultrasound pachymetry measurement , sap , matrix , gdx vcc , and oct . patients were eligible if they had a best - corrected visual acuity greater than 20/40 and a normal anterior chamber and open - angle on slit - lamp and gonioscopic examinations , respectively . participants with any other ophthalmic disease that could result in vf defects or who had histories of diabetes mellitus were excluded . a glaucomatous optic disc was defined as a disc showing increased cupping ( vertical cup - disc ratio > 0.6 ) , asymmetrical cupping ( a between - eye difference in the vertical cup - disc ratio of > 0.2 ) , diffuse or focal neural rim thinning , hemorrhage , or nerve fiber layer defects . glaucomatous eyes defined by sap ( sap group ) were those with a glaucomatous optic disc appearance and glaucomatous vf defects defined by the glaucoma hemifield test ( ght ) as outside 99% of age - specific normal limits and also with a pattern standard deviation ( psd ) outside 95% of the normal limit with the 24 - 2 full threshold program or the 24 - 2 swedish interactive threshold algorithm ( sita ) standard programs of the hfa . eyes with a glaucomatous optic disc appearance and a ght result outside 99% of the age - specific normal limits with a psd outside 95% of the normal limit with matrix were categorized by matrix as suffering from glaucoma ( matrix group ) . since there were no generalized criteria in matrix for diagnosing glaucoma , we arbitrarily applied the same criteria as in sap to the matrix results . we included only those patients who , within one month of the initial evaluation , yielded a reliable vf measurement , defined as a false - positive error < 15% , a false - negative error < 15% and a fixation loss < 20% in both sap and matrix . subsequently , 90 eyes were classified as glaucomatous in the sap group and 112 eyes were identified in the matrix group . all procedures conformed to the declaration of helsinki , and the study was approved by the ethics committee of the asan medical center . oct measures rnfl thickness with a low - coherence light source projected onto the retina . the time delay of the light backscatter from the rnfl compared with light reflected by a reference mirror is then calculated . circumpapillary rnfl was measured in the fast rnfl modeusing three 360-degree circular , high - resolution scans with a diameter of 3.4 mm that were centered on the optic disc . rnfl thicknesses of the collective quadrants ( 360 measure ) , as well as the individual temporal ( 316-45 ) , superior ( 46-135 ) , nasal ( 136-225 ) , and inferior ( 226-315 ) quadrants , were obtained for analysis . diagnostic categorization by stratus oct involves a software - based comparison of thickness parameters with an internal normative database of 328 eyes ; we also evaluated these parameters in our study . parameters on the stratus oct printout are annotated to indicate whether they fall outside of the 99% confidence interval ( ci ) , between the 95% and 99% cis ( borderline ) or within the 95% ci ( normal ) . in this study , only well - focused and centered scans with signal strengths seven were included , and a parameter was considered outside the normal limits if ci < 95% and within the normal limits if ci > 95% . slp imaging was performed in a standardized fashion ( gdx vcc software version 5.5.0 ) with a circular scan ( 3.2 mm in diameter ) centered on the optic disc . the general principles of slp with variable corneal polarization compensation ( vcc ) have been described in detail elsewhere.19 - 21 we only analyzed eyes with a scan quality score of eight or better . the slp parameters examined were tsnit ( temporal , superior , nasal , inferior , and temporal ) imaging , superior imaging , inferior average imaging , and the nerve fiber indicator ( nfi ) . the gdx vcc printout provides probabilities of abnormality based on a comparison with an internal database containing information on 540 normal eyes . in this study , a parameter was considered outside the normal limits if p<0.05 and within the normal limits if p>0.05 . for the nfi parameter , the manufacturer - suggested cutoff of < 30 was considered as within the normal limits , whereas values of 31 - 100 were considered abnormal . participants were classified based on the severity of their functional damage as assessed by sap and matrix . since no generalized criteria for categorizing glaucoma severity using matrix exists , we used the same mean deviation ( md ) values for both sap and matrix . with reference to the mean deviations of sap and matrix , each vf defect was classified as early ( no worse than -6db ) : groups s1 and m1 ; moderate ( worse than -6 db but not worse than -12db ) : groups s2 and m2 ; and advanced ( worse than -12db ) : groups s3 and m3.22 the s1 , s2 and s3 subgroups were classified according to sap severity , whereas subgroups m1 , m2 and m3 were determined by matrix severity scores . all statistical tests were performed using a statistical software package ( spss 15.0 for windows ; spss inc . , chicago , il ) . rnfl thicknesses measured by oct and gdx vcc were compared among the three groups categorized by md scores from both sap and matrix using a one - way analysis of variance ( anova ) with pairwise , post - hoc tukey comparisons . the normative classifications determined by the internal databases of the oct and gdx vcc instruments were compared among the three subgroups for each of sap and matrix using the chi - square test . differences with a value of p<0.05 the mean age of the 90 participants in the sap group was 56.913.4 years , and the mean age of the 112 participants in the matrix group was 54.412.6 years . table 1 summarizes the demographics and clinical characteristics of both groups . in the sap group , 21 eyes were classified as s1 , 50 eyes as s2 , and 19 as s3 , according to md criteria . in the matrix group , 47 eyes were classified as m1 , 39 eyes as m2 , and 26 eyes as m3 ( table 2 ) . structural parameters assessed by oct and gdx vcc were compared in the sap subgroups and the matrix subgroups ( table 3 ) . average rnfl thickness measured by oct was 79.719.5 m in the sap group and 86.818.6 m in the matrix group ( p=0.41 ) . the average nfi determined by gdx vcc was 54.923.3 in the sap group and 46.022.4 in the matrix group ( p=0.67 ) . overall , no rnfl thickness parameter measured using either oct or gdx vcc differed , with statistical significance , between the sap and matrix groups . in the sap group , average , superior and inferior rnfl thicknesses measured by oct were significantly different between the s1 and s2 groups ( p=0.001 , 0.011 and 0.000 , respectively ) , whereas the average and inferior rnfl thicknesses were significantly different in the m1 and m2 groups ( p=0.016 and 0.013 , respectively ) . nasal and temporal rnfl thicknesses did not differ when the s1 and s2 or the m1 and m2 subgroups were compared . tsnit values , superior averages , tsnit sds , and nfis assessed by gdx vcc were significantly different between the s1 and s2 subgroups , but only nfis were significantly different between the m1 and m2 subgroups . all parameters of oct and gdx vcc were significantly different between the s2 and s3 subgroups and also between the s1 and s3 subgroups . matrix subgroup analysis also revealed significant differences between groups m2 and m3 , and m1 and m3 ( table 4 ) . we used the chi - square test to compare structural parameters interpreted with the internal normative databases . compared to abnormal classifications , percentages of such classifications among the subgroups were significantly different in all parameters in both the sap and matrix subgroups ( table 5 ) . structural parameters assessed by oct and gdx vcc were compared in the sap subgroups and the matrix subgroups ( table 3 ) . average rnfl thickness measured by oct was 79.719.5 m in the sap group and 86.818.6 m in the matrix group ( p=0.41 ) . the average nfi determined by gdx vcc was 54.923.3 in the sap group and 46.022.4 in the matrix group ( p=0.67 ) . overall , no rnfl thickness parameter measured using either oct or gdx vcc differed , with statistical significance , between the sap and matrix groups . in the sap group , average , superior and inferior rnfl thicknesses measured by oct were significantly different between the s1 and s2 groups ( p=0.001 , 0.011 and 0.000 , respectively ) , whereas the average and inferior rnfl thicknesses were significantly different in the m1 and m2 groups ( p=0.016 and 0.013 , respectively ) . nasal and temporal rnfl thicknesses did not differ when the s1 and s2 or the m1 and m2 subgroups were compared . tsnit values , superior averages , tsnit sds , and nfis assessed by gdx vcc were significantly different between the s1 and s2 subgroups , but only nfis were significantly different between the m1 and m2 subgroups . all parameters of oct and gdx vcc were significantly different between the s2 and s3 subgroups and also between the s1 and s3 subgroups . matrix subgroup analysis also revealed significant differences between groups m2 and m3 , and m1 and m3 ( table 4 ) . we used the chi - square test to compare structural parameters interpreted with the internal normative databases . compared to abnormal classifications , percentages of such classifications among the subgroups were significantly different in all parameters in both the sap and matrix subgroups ( table 5 ) . sap is considered to be a standard approach for detecting vf loss in glaucoma.1 however , sap may not be able to detect early functional changes because of redundancies in rgcs and optic nerve fibers , which can mask damage.23,24 as a screening device , humphrey matrix frequency doubling technology perimetry ( matrix ) is known to be similar to or better than the humphrey field analyzer.25 - 28 frequency doubling technology ( fdt ) perimetry was developed as a method to detect early glaucoma by attempting to functionally isolate " my " cells , which may be selectively damaged in the early stages of glaucoma.1,25,29 my cells are not functionally redundant ( making up 3 - 5% of all ganglion cells ) ; the fdt technique thus has the theoretical potential to identify early vf loss.30,31 matrix perimetry is an updated version of fdt perimetry , employing a larger number of stimulus locations and smaller targets than those used in fdt perimetry . matrix also provides the global indices of sap , such as md , psd and ght classification , in a standard printout.32 - 35 comparison of matrix and sap threshold sensitivities is not appropriate because the two technologies measure different aspects of retinal sensitivity sap assesses differential light sensitivity , and matrix obtains data on contrast sensitivity . although global indices were reported to be significantly correlated between sap and matrix,36,37 there is no consensus for the definition of glaucomatous vf defects as determined by matrix . therefore , we used the same criteria ( psd < 5% and abnormal ght ) to define glaucoma identified by both sap and matrix , and we divided patients into three groups according to the severity of the md . stratus oct and gdx vcc are the two most recent commercial instruments available to analyze peripapillary rnfl thickness . in many studies , both gdx vcc and oct showed relatively high diagnostic accuracies in glaucoma detection.38 - 41 average rnfl thickness by oct demonstrated a strong correlation with vf defects.42 the nfi data from gdx vcc also revealed a strong correlation with vf defects . however , rnfl thicknesses determined by oct in the nasal and temporal quadrants have been reported to show high measurement varia bilities.43 - 46 reus and lemij suggested that glaucoma patients with mild - to - moderate vf loss might be better monitored with the gdx vcc.47 kim and kook reported that abnormal scores obtained on fdt perimetry screening programs correlated negatively with rnfl retardation values , as measured in glaucomatous changes seen by slp.48 however , to our knowledge , no data confirming a relationship between vf loss and gdx and oct matrix data has been published . in this study , we divided patients into subgroups using md values from both sap and matrix . our results showed that all structural parameters except nasal and temporal rnfl thicknesses obtained by oct were significantly different among cases in the three different stages of glaucoma . these findings suggest good correlations between rnfl thickness parameters assessed by oct and gdx vcc on the one hand , and sap defects on the other , in patients in different stages of glaucoma . only nasal and temporal quadrant data of oct , and the inferior average of gdx vcc , showed no meaningful correlations between early ( s1 ) and moderate ( s2 ) glaucoma stages as assessed by sap . this might be explained by high measurement variability.43 - 45 the fact that nasal and temporal quadrants are relatively more resistant to glaucomatous damage may also partly explain these findings . however , not all structural parameters showed significant differences betweenearly ( m1 ) and moderate ( m2 ) stages of glaucoma as assessed by matrix . average and inferior rnfl thicknesses by oct and nfi by gdx vcc were significantly different between the m1 and m2 subgroups , but there were no differences in any other parameters . although some parameters did not differ between the m1 and m2 subgroups , all parameters assessed by gdx vcc and oct showed significant differences between the moderate ( subgroup m2 ) and advanced ( subgroup m3 ) patients . matrix is known to be superior to sap for detecting the early stages of glaucoma . in this study , we observed that although the matrix subgroups showed definite structural differences between cases of moderate and severe glaucoma as assessed by gdx and oct parameters , not all parameters differed between patients with early and moderate glaucoma . this could indicate that matrix can be an excellent screening device to detect early glaucoma , especially in the preperimetric stage , but it has difficulty in discriminating between the early and moderate stages of glaucoma . the other possible explanation for the poor correlation of structural damage with functional deficits as determined by matrix in early - to - moderate glaucoma stages is related to the reliability of matrix itself . we acknowledge that this is a limitation of our study . because the study design was retrospective , all participants underwent a comprehensive ophthalmic examination at the initial visit , including sap , fdt , oct , and gdx vcc . if reliability indices were poor during testing , the operator stopped the test , explained the process thoroughly , and then restarted the test . to maximize reliability and to minimize learning effect - related issues , we adopted strict vf inclusion criteria . to our knowledge , this is the first study to examine the relationship between functional and structural damage in glaucoma subgroups of different severities using both sap and matrix global indices . we concluded that glaucoma status as defined by both sap and matrix correlates with structural loss as assessed by oct and gdx vcc , but that such correlations are slightly weaker in the early - to - moderate glaucoma stages as defined by matrix .
purposeto evaluate and compare correlations between structural and functional loss in glaucoma as assessed by optical coherence tomography ( oct ) , scanning laser polarimetry ( gdx vcc , as this was the model used in this study ) , standard automated perimetry ( sap ) , and the humphrey matrix ( matrix).methodsninety glaucomatous eyes identified with sap and 112 eyes diagnosed using matrix were independently classified into six subgroups , either s1/m1 
 ( md>-6db ) , s2/m2 ( -12<md<-6db ) or s3/m3 ( md<-12db ) , according to the mean deviation ( md ) of each test . 
 average and sectoral retinal nerve fiber layer ( rnfl ) thickness and percentage of abnormal classifications using the internal normative databases of oct and gdx vcc were compared among the six subgroups.resultsin the sap subgroups , rnfl thickness values obtained by oct in the nasal and temporal quadrants and the inferior averages of gdx vcc did not differ between the s1 and s2 subgroups ( p=0.137 , 0.738 and 0.149 , respectively ) . in the matrix subgroups , no measurement parameters differed between the m1 and m2 groups except for the overall mean and average inferior rnfl thickness given by oct and the nfi values of gdx vcc ( p=0.013 , 0.016 and 0.029 , respectively ) . when abnormal classifications were compared , all measurement parameters , without exception , were significantly different in both the sap and the matrix subgroups.conclusionssap subgroups showed a good correlation of structural and functional defects when assessed using oct and gdx vcc . 
 these correlations were weaker in the matrix subgroups , especially in the early stages of glaucoma .