Information for Clinicians

Moorfields Motion Displacement Test (MDT)
Background for clinicians

The original Motion Displacement Test (MDT) was first developed in the early 1980s by Professor Fitzke at the Institute of Ophthalmology, London [1, 2]. The original test used a single line stimulus which was presented just above the blind spot (15,9) on a BBC computer (Figure 1).

Figure 1. Diagrammatic representation of original single line MDT
The white circle corresponds to central fixation (0,0) and the open circle the optic nerve head.

Figure 1, Diagrammatic representation of the origional MDT

The single line MDT was found to be a predictor of glaucomatous field loss,[3] with evidence of elevated motion displacement threshold in areas of the visual field estimated to be normal by standard automated perimetry (SAP).[4] The MDT was also found to be robust to the effect of media opacity.[5, 6] It was these properties that provided the rational to take the test onto a multi-location format in 1999.

Epidemiology studies show that the global estimate for open angle and angle closure glaucoma is in the region of 60 million. This figure is expected to approach 80 million by 2020. At least 50% of glaucoma sufferers in the industrial world are undiagnosed, with this figure reaching 90% in the developing world.[7-17]

The vision of the new Moorfields MDT is to address the global challenge of glaucoma detection by providing a modern, windows-based test suitable for PC use. The current test is presented on a 15-inch laptop computer with the aim of offering an affordable and portable method of case-finding in the community.

The Moorfields MDT has been under development since 1999 by the Glaucoma Research Unit at Moorfields in collaboration with the Institute of Ophthalmology, UCL. The partnership expanded to include City University, London in 2006. The test development has been strengthened by this university led research and the Moorfields MDT was awarded overall winner of the Medical Research Council (MRC) translational research innovation awards in the Medical Futures competition of 2008.

What is the Moorfields MDT?

The Moorfields MDT is a multi-location test which is presented on a standard computer screen. The patient is asked to look at a central spot and to press the computer mouse each time a line on the screen is seen to move.

The current test presents 32 line stimuli, which are each scaled by estimate of retinal ganglion cell density.[18] Each location corresponds to a location on the Humphrey 24-2 program, allowing pointwise comparison between the two instruments. The locations are selected by application of the Garway-Heath map of the anatomic relationship of the optic disc to the visual field.[19] The 32-location MDT fits on a standard 15-inch laptop screen at a test distance of 30 cm.

The line stimuli are white (124 cd/m2) and continuously presented on a grey background (10 cd/m2), giving a Michelson contrast of 85%. Each stimulus presentation is three oscillations at 200 msec per cycle.[20, 21] The threshold is recorded as the minimum detectable displacement, which is measured in minutes of arc. Motion displacement sensitivity is greater than predicted from retinal ganglion cell spacing and therefore falls into the category of hyperacuity.[22-24] The MDT task is to discriminate the positional change between two lines and may be regarded as a temporal form of vernier acuity.

Study of the summation properties of the MDT stimulus shows a linear relationship with the stimulus energy ([stimulus area] * [stimulus luminance – background luminance]) giving the relationship T = k √E [T = mdt threshold; K = constant; E = stimulus energy]. This threshold energy displacement law (TED) may be used to predict MDT threshold for different configurations of stimuli. Equivalent thresholds are found for stimuli of equivalent energy, showing that Ricco’s law applies to the MDT stimulus (figure 2).[25]

Figure 2. Plot of log MDT threshold as a function of log stimulus energy

Figure 2 Plot of log MDT threshold as a function of log stimulus energy

A staircase strategy was developed in 2004-5 and a normative database of 120 subjects (20 – 85 years) collected in 2006-8. Pilot comparison with glaucoma showed good topographical correspondence of the Moorfields MDT with standard automated perimetry, showing 70% pointwise agreement of the 32 matched locations. These studies were presented at The Association for Research in Vision and Ophthalmology (ARVO) meeting 2008 (Florida, USA), The International Perimetric Society (IPS) meeting 2008 (Nara, Japan) and the European Glaucoma Society (EGS) meeting 2008 (Berlin, Germany).

The early staircase MDT strategy was found to be too long for screening purposes (5-7 minutes per eye). The team has collaborated with  City University since 2006 to develop adaptive algorithms with aim of reducing the test duration.

The Moorfields MDT currently offers two strategies:

  1. ESTA, an enhanced suprathreshold strategy, which takes in the region of 90 -120 seconds per eye. ESTA is designed for rapid case finding in the community. The ESTA detection program was reported to outperform the Humphrey 76 point screening test, the Frequency Doubling Matrix screening test and Heidelberg Retinal Tomography in the preliminary findings of the St Kitts Eye Study presented by Associate Professor Paul Artes at ARVO 2008 (The St Kitts Eye Study (SKES): Design and Initial Findings. Artes et al.  IOVS 2008; 49: ARVO E-abstract 4080; http://www.scribd.com/doc/14946158/ArtesARVO09-StKitts ).

    Version 1 of ESTA offers large suprathreshold displacements

    Version 2 of ESTA offers optimised strategies based on current normative centile estimates a) 99.5 strategy b) 95 strategy. These are currently undergoing validation to establish pass-fail cut offs using a new global index termed "the probability of true damage" (PTD) which applies a novel spatial filter. This will be done for different populations in hospital and community settings.

    Collaborators for this study include:

    • Dr Francesco Oddone and Dr Lucia Tango Bietti Foundation, Rome, Italy.
    • Mrs Florence Rasquin MD, Consultant Ophthalmologist and Mrs Nacima Kisma FEBO MD, Erasmus Hospital, Brussels.
    • Mr Eamon Sharkawi FRCOphth Consultant Ophthalmologist, Jules-Gonin Eye Hospital, 15 Avenue de France, 1004 Lausanne, Switzerland.
    • Clare Gilbert, Professor of International Eye Health, The London School of Hygiene and Tropical medicine London UK.
  2. WEBS, a weighted binary search threshold strategy, which takes in the region of 4.5 – 5 minutes per eye and is designed for more detailed investigation in the hospital setting.

    The ESTA and WEBS algorithms are currently undergoing validation in a collaborative international study which is designed to compare the diagnostic precision of the Moorfields MDT with Standard Automated Perimetry (SAP), the Frequency Doubling Test (FDT) and the new Heidelberg Edge Perimeter (HEP) in very early ‘glaucoma.’ The patient selection criterion is by ‘structure’ using the Heidelberg retinal tomograph (HRT) as a reference standard (abnormal Moorfields regression, rim area greater than 0.5 mm2 and a disc area within the normal range). The study collaborators are:

    • Professor John Flanagan PhD MCOptom FAAO and Carmen Balian, Department of Ophthalmology and Vision Sciences, University of Toronto, Canada.
    • Associate Professor Paul Artes PhD and Glen Sharpe, Department of Ophthalmology and Vision Sciences, Dalhousie University, Halifax, Canada.
    • Dr Francesco Odone, Dr Lucia Tango and Manuele Michelessi, The Bietti Foundation, Rome.

Comparison of the Moorfields MDT with Octopus and Pulsar perimetry www.octopus.ch is being undertaken by the Hôpital Ophtalmique Jules-Gonin, University of Lausanne, Switzerland. This project is led by Dr Eamon Sharkawi with Dr Corinne Schnyder and Dr Hana Abouzeid.

The ESTA program has recently taken part in a community study which is led by Alfonso Antón MD PhD and Monica Fallon at the Hospital de la Esperanza y el Mar, Instituto Municipal de Investigaciones Médicas (IMIM, IMAS) and the Universidad Autónoma de Barcelona. The study objective is to assess the cost/effectiveness of screening for glaucoma through telemedicine.

The Singapore National Eye Centre (SNEC)
http://www.snec.com.sg/clinical/staff_glaucoma.asp has recently completed a study which tested the new MMDT Pandora response algorithm which allows for slow responders and offers improved estimate of reliability. The  project is led by Associate Professor Tin Aung and Dr Alicia How.

Current Development Work at the NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust & UCL Institute of Ophthalmology

One of the challenges of making comparison between the Moorfields MDT and standard automated perimetry is that different measurement scales are applied to the different psychophysical stimuli. The motion displacement threshold is recorded in minutes of arc and differential light sensitivity in decibels. We are currently exploring the relative dynamic range of each stimulus with the aim to provide a reference scale for improved comparison between the instruments.

The pixel size of standard LCD monitors limits the measurement of threshold in areas of high retinal sensitivity. We have recently overcome this by the development of a novel sub-pixel strategy. We are currently working on the development of an improved threshold strategy. We plan to incorporate an adaptive response algorithm which will allow for the effects of individual variation, learning and fatigue. We hope that the new threshold strategy will extend the role of the Moorfields MDT to monitor glaucoma progression. A new normative database will be undertaken when the threshold strategy and new response algorithm are fully developed.

Current and Future studies including diversification of the Moorfields MDT

  • A study investigating the effects of cataract on standard automated perimetry, Moorfields MDT, frequency doubling perimetry and the Heidelberg edge perimeter will shortly be conducted at The Moorfields out-reach clinic of St George’s. This study will be led by Mr Guz Gazzard and Ms Jay Varia and is designed to lead on from a recently published paper on the effect of straylight.[26]
  • A community optometry-based study is planned with Dr Paul Healey and Dr Ankur Mehta in Sydney Australia.
  • A study is planned to take place in 5 rural GP practices with poor access to eye care in Northern Greece. This will be led by Professor Fotis Topouzis at the Aristotle and University of Thessaloniki (AUTH), Greece.
  • Multiple feasibility studies are planned in Africa in collaboration with:
    1. Professor Roger Anderson http://biomed.science.ulster.ac.uk/vision/Professor-Roger-Anderson.html and Dr James Loughman http://optometry.dit.ie/staff/jloughman/profile.html through the Mozambique Eye Care project which is an Irish Aid/Higher Education Authority (HEA) initiative http://www.dit.ie/mozambique-eyecare
    2. Professor Clare Gilbert at the London School of Hygiene and Tropical medicine (LSHTM) www.lshtm.ac.uk/aboutus/people/gilbert.clare
    3. Mr Ian Murdoch, MSc  MD FRCOphth, Consultant Ophthalmologist at Moorfields Eye Hospital at the Moorfields Lions Eye Centre, Korle Bu, Ghana.
    4. Vision 2020 in Uganda www.vision2020royalfree-mulago.co.uk/default.html
    5. Righttosight let by Kate Coleman FRCOphth www.rightosight.com
    6. Akamba Aid fund www.akambaaidfund.org, led by Simon Frackiewicz The study will take place in the Akamba tribal region as a result of the radio 4 interview which took place in 2011
  • It is hoped that Professor Robert Stamper MD ucsfeye.net/rstamper.shtml will include the Moorfields MDT in a planned study in India.
  • Iris Asia www.irisasia.org , led by Mr Andy Richards FRCOphth, has expressed interest in potential studies in Cambodia, Sri Lanka and Nepal.
  • A future study is planned to investigate the role of new technology for the detection of glaucoma in the UK.
  • Mr Mark Westcott is currently exploring motion displacement deficits in Birdshot Chorioretinopathy with Dr Nacima Kisma at Moorfields Eye Hospital.
  • It is hoped that a collaboration will take place with Phil Clatworthy MD, neurologist at Bristol University UK, to explore the potential role of a neurological Moorfields MDT program in patients with stroke.
  • The development of a paediatric version of the MDT is planned in collaboration with Professor Jugnoo Rahi at Great Ormond Street Hospital for Children NHS Trust and The Institute of Child Health London http://www.ich.ucl.ac.uk/  Pilot testing in children with healthy eyes will shortly be undertaken in collaboration with City University through Professor David Thompson's vision screener for school's program http://www.city.ac.uk/health/research/research-areas/optometry/applied-vision-research-group/software-for-vision-assessment-and-screening-lab.

What are the Moorfields MDT’s advantages?

  • easily understood
  • portability
  • affordability
  • robust to optical blur
  • robust to cataract [5, 6, 26]

Register your interest

Register here for notification when the Moorfields MDT is officially released.

The commercialisation of the Moorfields MDT is being led by UCLB http://www.uclb.com/ It is anticipated the case finding version ESTA will be available towards the end of 2011 on completion of the validation programs.

MHRA approval was granted to the Moorfields MDT in 2006 for the collection of the normative database (CE Device 1/ 2006 / 009073). The CE mark will be upgraded to from Device 1 to Device 2a before it is commercially released as a case-finding device.

References

  1. Fitzke FW, Poinoosawmy D, Ernst W.Hitchings RA. Peripheral displacement thresholds in normals, ocular hypertensives and glaucoma., in Perimetry Update 1986/1987, E. Greve and A. Heijl, Editors. 1987; Kugler & Ghedini: The Hague, The Netherlands. pp 447-452.
  2. Fitzke FW, Poinoosawmy D, Nagasubramanian S.Hitchings RA. Peripheral displacement thresholds in glaucoma and ocular hypertension., in Perimetry Update 1988/1989, A. Heijl, Editor. 1989; Kugler & Ghedini: The Hague, The Netherlands. pp 399-405.
  3. Baez KA, McNaught AI, Dowler JG, Poinoosawmy D, Fitzke FW.Hitchings RA. Motion detection threshold and field progression in normal tension glaucoma. Br J Ophthalmol. 1995;79(2):125-8.
  4. Westcott MC, Fitzke FW.Hitchings RA. Abnormal motion displacement thresholds are associated with fine scale luminance sensitivity loss in glaucoma. Vision Res. 1998;38(20):3171-80.
  5. Membrey L.Fitzke FW. Effect of lens opacity on white-on-white perimetry, frequency doubling perimetry, and motion detection perimetry, in Perimetry Update 2000/2001, M. Wall and J. Wild, Editors. 2000; Kugler Publications: The Hague, The Netherlands. pp 259-266.
  6. Membrey L, Kogure S.Fitzke FW. A comparison of the effects of neutral density filters and diffusing filters on motion perimetry, white on white perimetry and frequency doubling perimetry, in Perimetry Update 1998/1999, M. Wall and J. Wild, Editors. 1998; Kugler Publications, The Hague, The Netherlands. pp 75-83.
  7. Quigley HA, Broman AT The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006; 90:262-267
  8. Bourne RR, Sukudom P, Foster PJ, Tantisevi V, Jitapunkul S, Lee PS, Johnson GJ.Rojanapongpun P. Prevalence of glaucoma in Thailand: a population based survey in Rom Klao District, Bangkok. Br J Ophthalmol. 2003;87(9):1069-74.
  9. Coffey M, Reidy A, Wormald R, Xian WX, Wright L.Courtney P. Prevalence of glaucoma in the west of Ireland. Br J Ophthalmol. 1993;77(1):17-21.
  10. Mitchell P, Smith W, Attebo K.Healey PR. Prevalence of open-angle glaucoma in Australia. The Blue Mountains Eye Study. Ophthalmology. 1996;103(10):1661-9.
  11. Quigley HA, West SK, Rodriguez J, Munoz B, Klein R.Snyder R. The prevalence of glaucoma in a population-based study of Hispanic subjects: Proyecto VER. Arch Ophthalmol. 2001;119(12):1819-26.
  12. Ramakrishnan R, Nirmalan PK, Krishnadas R, Thulasiraj RD, Tielsch JM, Katz J, Friedman DS.Robin AL. Glaucoma in a rural population of southern India: the Aravind comprehensive eye survey. Ophthalmology. 2003;110(8):1484-90.
  13. See JL.Chew PT. Glaucoma in Singapore. J Glaucoma. 2004;13(5):417-20.
  14. Tielsch JM, Katz J, Singh K, Quigley HA, Gottsch JD, Javitt J.Sommer A. A Population-based Evaluation of Glaucoma Screening: The Baltimore Eye Survey. Am J Epidemiol. 1991;134(10):1102-1111.
  15. Topouzis F, Coleman AL, Harris A, Koskosas A, Founti P, Gong G, Yu F, Anastasopoulos E, Pappas T.Wilson MR. Factors associated with undiagnosed open-angle glaucoma: the thessaloniki eye study. Am Ophthalmol. 2008;145(2):327-335.
  16. Nizankowska MH.Kaczmarek R. Prevalance of open angle glaucoma and ocular hypertension as a risk factor for primary open angle glaucoma in Wroclaw population. Wroclaw Epidemiology Study. Klin Oczna. 2004;106(1-2 Suppl):147-52.
  17. Dandona L, Dandona R, Srinivas M, Mandal P, John RK, McCarty CA.Rao GN. Open-angle glaucoma in an urban population in southern India: the Andhra Pradesh eye disease study. Ophthalmology. 2000;107(9):1702-9.
  18. Garway-Heath, D. F., J. Caprioli, et al. Scaling the hill of vision: the physiological relationship between light sensitivity and ganglion cell numbers. Invest Ophthalmol Vis Sci. 2000; 41 (7): 1774-82.
  19. Garway-Heath DF, Poinoosawmy D, Fitzke FW.Hitchings RA. Mapping the visual field to the optic disc in normal tension glaucoma eyes. Ophthalmology. 2000;107(10):1809-15.
  20. Verdon-Roe GM, Westcott MC, Viswanathan AC, Fitzke FW.Hitchings RA. Optimum number of stimulus oscillations for motion displacement detection in glaucoma, in Perimetry Update 2000/2001, M. Wall and J. Wild, Editors. 2000; Kugler Publications: The Hague, The Netherlands. pp 97-102.
  21. Westcott MC, Verdon-Roe GM, Viswanathan AC, Fitzke FW.Hitchings RA. Optimum stimulus duration for motion displacement detection in glaucoma, in Perimetry Update 2000/2001, M. Wall and J. Wild, Editors. 2000; Kugler Publications: The Hague, The Netherlands. pp 103-108.
  22. Exner S. Uber des Sehen von Bewegung und die Theorie des zusammengesetzten Auges. Sher. Akad. Wiss. Wien. (Math.-nat. Kl., Abt. 3). 1875;72:156-190.
  23. Scobey RP.Horowitz JM. Detection of image displacement by phasic cells in peripheral visual fields of the monkey. Vision Res. 1976;16(1):15-24.
  24. Westheimer G. Editorial: Visual acuity and hyperacuity. Invest Ophthalmol. 1975;14(8):570-2.
  25. Verdon-Roe GM, Westcott MC, Viswanathan AC, Fitzke FW.Garway-Heath DF. Exploration of the psychophysics of a motion displacement hyperacuity stimulus. Invest Ophthalmol Vis Sci. 2006;47(11):4847-55.
  26. The effect of induced intraocular stray light on perimetric tests. Bergin C, Redmond T, Nathwani N, Verdon-Roe GM, Crabb DP, Anderson RS, Garway-Heath DF. Invest Ophthalmol Vis Sci. 2011: Published online before print January 27, 2011, doi: 10.1167/iovs.10-6642.
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