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G. M. Verdon-Roe, C. Bergin, T. Redmond, N. Nathwani, D. P. Crabb, R. S. Anderson, D. F. Garway-Heath; The Effect of Induced Intraocular Stray Light (Cataract Simulation) on Thresholds of Standard and Newer Perimetric Tests. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5292.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of increases in intraocular stray light (ISL) on threshold measurements made by four modern forms of perimetry: Standard Automated Perimetry (SAP) using a HFA II (SITA 24-2), Frequency Doubling Perimetry (FDT) using a Zeiss Matrix (N-24-2), the Heidelberg Edge Perimeter (HEP; ASTA) and the Moorfields Motion Displacement Test (MDT; WEBS)
Six healthy psychophysically experienced observers were recruited (mean age 26yrs [21yrs, 29yrs]), refractive correction [0 D,-4.25D]). Five white opacity filters (WOF), each scattering light by a different amount, were used to create incremental increases in ISL. Resultant ISL values were measured with each WOF and at baseline (no WOF) for each subject using a C-Quant Straylight Meter (Oculus, Wetzlar, Germany). An average 25 yr old has an ISL value of ~0.85dB, an increase of 40% in ISL to 1.2dB, is similar to that of a 70 yr old. Each WOFs created an increase in ISL between 10-150% from baseline, ranging from effects similar to normal aging to those of considerable cataract. Each subject underwent 6 test sessions over a 2 week period; each session consisted of the 4 perimetric tests using one of the five WOFs and baseline (both instrument and filter were randomised).
The reduction in sensitivity from baseline was normalised with respect to the spread of the respective normative values from each instrument (in some cases derived from in-house data) allowing comparison of standardised (z) scores. Initially both MDT and SAP measured thresholds were invariant; however with for both moderate to large increases in straylight (50-150%) SAP, FDT and HEP were highly significantly affected (p<0.001), while MDT remained unaffected.
The Moorfields MDT measurement of threshold is robust to effects of additional stray light as compared to SAP, FDT and HEP
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