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 us that the global estimate for open angle and angle closure glaucoma 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 standard PC use. The current test is presented on a 15-inch laptop computer with the aim of offering affordable and portability for case-finding in the community.

The new 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 MRC translational research awards in the Medical Futures competition of 2008.

What is the new Moorfields MDT?

The new 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 uses 32 line stimuli, which are scaled by estimate of retinal ganglion cell density. 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.[18] The new 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 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.[19, 20] 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 it therefore falls into the category of hyperacuity.[21-23] 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).[24]

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

Recent work has included the development of a normative database and pilot comparison with glaucoma. The results of 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).

City University has developed adaptive algorithms over the last two years which have the benefit of reducing the test duration. The Moorfields MDT now offers two new strategies:

  1. ESTA, an enhanced suprathreshold strategy which takes 90 seconds per eye. This is designed for rapid case finding in the community.
  2. WEBS, a weighted binary search strategy which takes 4.5 – 5 minutes per eye and is designed for more detailed investigation in the hospital setting.

These two new strategies are currently undergoing validation in a collaborative international study which will 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’ (glaucoma selection criterion is by ‘structure’ using the Heidelberg retinal tomograph (HRT): 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, Department of Ophthalmology and Vision Sciences, University of Toronto, Canada.
  • Dr Paul Artes PhD, 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 study uses the same selection criterion as above.

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 ).

The ESTA program is also taking 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 ESTA program will shortly be joining studies at the Singapore National Eye Centre (SNEC) http://www.snec.com.sg/clinical/staff_glaucoma.asp led by Assoc Prof Tin Aung and Dr Alicia How.

A study will take place in 5 GP practices in Northern Greece led by Professor Fotis Topouzis and Dr Androniki Glystra  at the Aristotle and University of Thessaloniki (AUTH), Greece.

A community pilot study is planned with Dr Paul Healey and Ankur Mehta in Sydney Australia.

Future studies:

  • A study is planned to investigate the role of new technology for the detection of glaucoma in the UK.
  • A study is planned to investigate the potential of extending the role of the Moorfields MDT to monitor glaucoma progression.
  • The development of a paediatric test is planned in collaboration with Jugnoo Rahi at Great Ormond Street Hospital for Children NHS Trust and The Institute of Child Health London http://www.ich.ucl.ac.uk/

MHRA approval was granted to the Moorfields MDT in 2006 (CE / 2006 / 009073).

What are the Moorfields MDT’s advantages?

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

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 it will be available in 2011 on completion of the validation programs.

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 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.
  19. 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.
  20. 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.
  21. 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.
  22. 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.
  23. Westheimer G. Editorial: Visual acuity and hyperacuity. Invest Ophthalmol. 1975;14(8):570-2.
  24. 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.
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