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L. T. Labriola, R. A. Bilonick, P. M. Brennen, T. R. Friberg; Drusen Size as an Indicator of Drusen Area Using Drusen Detection Software. Invest. Ophthalmol. Vis. Sci. 2010;51(13):102.
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© ARVO (1962-2015); The Authors (2016-present)
Drusen area is important in many classification paradigms for AMD. The number of large drusen is correlated with total drusen area. We investigated the relationship between the number of small to large drusen and the total drusen area in AMD patients.
We assessed the drusen count distribution and drusen area of 513 participants of the AREDS and PTAMD study who had drusen in both eyes using a previously validated, semi-automated drusen detection software. We analyzed the central macula using circles of 1000 and 3000 µm diameter. Small drusen had a normalized diameter (ND) of <62 µm, medium or intermediate had a ND of 63-124 µm, and large drusen had a ND of 125-249 µm. We assumed that each druse within the ranges given above had a diameter equal to the average of the size limits of that range. For example, a small drusen (0-62 µm) would averaged 31 µm in diameter. An intermediate druse (63-124 µm) averaged 93 µm, etc. We then computed the total drusen area from the drusen distribution. We fitted structural equation models (SEMs) that related the measured drusen area and the counts of the drusen in each size range to investigate their relationship.
The results for the SEMs are presented in Table 1. For the central 1000 µm region, intermediate drusen had the highest correlation with drusen area (0.89). For the central 3000 µm region, the number of small drusen had the highest correlation (0.90) to total drusen area.
In the 3000 µm area, the number of intermediate drusen was more reflective of the total drusen area than the number of large drusen, but the coefficient values were close. In the 1000 µm area, the number of intermediate drusen was more predictive of total drusen area than the number of large drusen. We concluded that the number of large drusen is not necessarily a better reflection of total drusen area than the number of small drusen. We suggest that the concept of number of large drusen as a good indicator of total drusen area should be revisited with respect to the use of other possible size category indicators.
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