Authors: Theodora A M Siepman Marijke Wefers BettinkRemeijer Rogier Q Hintzen
Publish Date: 2010/05/12
Volume: 257, Issue: 10, Pages: 1654-1660
Abstract
Optical coherence tomography OCT and scanning laser polarimetry GDx ECC are noninvasive methods used to assess retinal nerve fiber layer RNFL thickness which may be a reliable tool used to monitor axonal loss in multiple sclerosis MS The objectives of this study are 1 to compare OCT with the GDx ECC 2 to assess and compare the RNFL thickness in subgroups of MS Ophthalmologic examination and RNFL assessment by OCT and GDx were performed in 65 MS patients 26 relapsingremitting RRMS ten secondaryprogressive SPMS 29 primaryprogressive PPMS Twentyeight patients 43 had a history of optic neuritis ON Adjustments were made for age and disease duration RNFL thickness was reduced in eyes with previous ON p 001 No differences were found between PPMS and relapseonset MS OCT and GDx ECC measurements were moderately correlated rho = 073 p 001 Visual fieldmean deviation MD values correlated with OCT means r = 044 p 001 and GDx ECC TSNIT average r = 041 p 001 In patients without previous ON EDSS correlated with MD r = −036 p 001 visual fieldpattern standard deviation PSD r = 030 p 005 OCT means r = −031–030 p 005 and macular volume r = −037 p 001 For MSIS29 physical impact score significant correlations were found with MD r = −048 p 001 and PSD r = 048 p 001 Conclusions No differences between PPMS and relapseonset MS subgroups were found RNFL thickness was reduced in eyes with previous ON Although OCT and GDx ECC findings were moderately correlated and showed significant correlations with measures of visual function in patients without previous ON EDSS correlated significantly with visual and OCT measures but not with GDx ECCThe central origin of irreversible disability in patients with multiple sclerosis MS lies in axonal loss 1 Brain atrophy on magnetic resonance imaging MRI is the most used marker to monitor disease progression However correlations between MRI measurements and clinical disability are limited 2 3 More specific measures of axonal damage and neuronal loss in MS are neededThe retina is part of the central nervous system and easily accessible for clinical examination The retinal nerve fiber layer RNFL is composed predominantly of unmyelinated axons of retinal ganglion cells Measurements of the RNFL give relatively direct measures of axons and thus of axonal damage Optical coherence tomography OCT and scanning laser polarimetry GDx are noninvasive methods used to measure peripapillary retinal nerve fiber layer RNFL thickness Both are established techniques used in glaucoma to detect early glaucomatous damage 4 OCT measures RNFL thickness by using interference patterns of backscattered nearinfrared light analogous to Bscan ultrasound and with an axial resolution of less than 10 μm 5 In contrast GDx indirectly quantifies the RNFL thickness by using polarized light that undergoes a phase shift after passing through the RNFL 6 GDx ECC is a new device with enhanced corneal compensation GDx ECC It has been introduced to optimize images of RNFL morphology by improving the signaltonoise ratio and to obtain a better structure–function relationship than with earlier versions of GDx the GDx FCC and GDx VCC 7 8 9 Both OCT and GDx analyse and express the average RNFL thickness in micrometers However because of the difference in technique of both methods the RNFL measurements of OCT and GDx in microns are not comparable 5Several studies with OCT have demonstrated RNFL thinning in optic neuritis ON 10 11 12 and MS 13 14 15 16 17 18 19 20 21 22 In patients with optic neuritis or MS fewer studies have used GDx 23 24 25 Comparative studies on differences between OCT and GDx RNFL measurements mostly have been performed in controls glaucoma 26 and only three groups published comparisons of the two techniques in MS patients 27 28 29 30 31 However the only studies available on GDx in MS until now made use of GDx VCC instead of the newer software version GDx ECC From these groups only one investigated correlations with disability EDSS but not with MS subtype 27 29 30 These studies comparing OCT with GDx have produced conflicting results concerning the discriminating value of both techniquesConsecutive patients with a diagnosis of MS were recruited through the Department of Neurology of the Erasmus Medical Centre Rotterdam from December 2004 to March 2008 Patients were included if the diagnosis was verified by one of the senior neurologists based on the McDonald criteria 32 For specific subcomparison of MS types we purposely included a relatively high number of patients with primary progressive MS PPMS Excluded were patients with ophthalmologic diseases that might impair or bias OCT and GDx ECC measurements eg diabetes primary open angle glaucoma abnormal discs with suspicion of normal tension glaucoma anomaly of the disc opacity of cornea or lens severe nystagmus The medical ethical committees of the participating hospitals approved this study and all patients gave written informed consentAll patients underwent a neurological and ophthalmologic examination Type of MS relapseonset RRMS/SPMS or PPMS time since first symptoms time since diagnosis Expanded Disability Status Scale EDSS Multiple Sclerosis Impact Scale MSIS29 and Multiple Sclerosis Severity Scale MSSS were assessedMSIS29 measures the physical and psychological impact of MS from the patient’s perspective The physical subscale includes 20 items and the psychological subscale nine items Total scores for both subscales are generated by summing individual items scored 1–5 with high scores indicating greater impact 33 MSSS corrects EDSS for disease duration time since first symptoms by comparing an individual’s disability with the distribution of scores in cases having equivalent disease duration 34 To be able to compare outcome parameters in different groups we aimed to match for disease duration time since first symptoms and time since diagnosis
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