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Co-author(s)
Sinapis, Dimitrios, Moorfields Eye Hospital, London, United Kingdom
(P)
Verdon-Roe, Gay Mary, Moorfields Eye Hospital, London, United Kingdom
Bergin, Ciara, City University, London, United Kingdom
Redmond, Tony, University of Ulster, Coleraine, United Kingdom
Nathwani, Neil, City University, London, United Kingdom
Crabb, David, Moorfields Eye Hospital, London, United Kingdom
Anderson, Roger, University of Ulster, Coleraine, United Kingdom
Garway-Heath, David, Moorfields Eye Hospital, London, United Kingdom
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Purpose: to explore the
effects of simulated cataract on threshold measurements with four psychophysical
stimuli, each used for the perimetric detection of glaucoma.
Design:
Experimental study. Participants: Six psychophysically experienced healthy
volunteers were recruited [mean age 26, range 21 to 29, years; distance
refractive correction plano to - 4.25 DSph].
Methods: Cataract was simulated
by one of five white opacity filters (WOFs) of increasing density, inserted
into wide-framed spectacles. A baseline measure (no WOF) of intraocular
stray light (ISL) was estimated for each subject using a C-Quant straylight
meter (Oculus, Wetzlar, Germany). This was repeated for each grade of
filter. Each subject underwent 6 test sessions over a 2 week period.
For each session, one of the filter conditions was randomly selected
and the subject was tested on the 4 perimeters [Standard Automated Perimetry
(SAP), 24-2 SITA; Frequency Doubling Technology (FDT) Matrix, N-24-2;
Heidelberg Edge Perimeter (HEP), ASTA; Moorfields Motion Displacement
Test (MDT), WEBS1-2], in a randomised order.
Main outcome measure: pointwise
comparison of the threshold (standardised z) measurements with each
grade of filter to the baseline, for each instrument.
Results: SAP thresholds
were unaffected by low grade WOF. However, SAP, FDT and HEP each showed
a highly significant (p<0.001) increase in thresholds for moderate to
large increases in straylight (50-150%). There was no statistically
significant change in average MDT thresholds across all filters.
Conclusions:
SAP, FDT and HEP thresholds were all affected by induced ISL levels
equivalent to mild to moderate cataract. The stimulus used in the Moorfields
MDT has been shown to be resistant to the effects of simulated cataract,
which is consistent with earlier reports of the original single line
MDT. 3-5 This is an important feature of a glaucoma case-finding device,
helping to maintain test specificity.
References: 1. www.moorfieldsmdt.co.uk
2. Bergin C, Moosavi R, Crabb DP, Verdon-Roe GM, Westcott MC,Viswanathan
AC, Fitzke FW, Garway-Heath DF. Developing and evaluating threshold
algorithms for the Moorfields Motion Displacement Test (MDT). Invest
Ophthalmol Vis Sci. 2008: ARVO E-Abstract 1108. 3. 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 4. 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.
5. 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. |