Heier H, Brinchmann-Hansen O
Center of Industrial Research, Ullevål University Hospital, Oslo, Norway.
Invest Ophthalmol Vis Sci. 1989 Apr;30(4):674-7.
When measuring the width of the blood column and the superimposed central light reflex of retinal vessels from fundus photographs, we find that the measurements are affected by focusing error, unless certain steps are taken to reduce its effect. Thus, we recommend using a scanning microdensitometer to extract the density profile of the blood column from the negative, and convert the density profile to an intensity profile by means of the characteristic curve of the film. In this paper we model the imaging process on a computer, and find that the half value width of the intensity profile is relatively insensitive to focus error. However, the maximum intensity of the central light reflex is still sensitive to focus error. Both these results are in agreement with experimental studies.
在通过眼底照片测量视网膜血管血柱宽度及叠加的中央光反射时，我们发现这些测量会受到聚焦误差的影响，除非采取某些措施来减小其影响。因此，我们建议使用扫描显微密度计从底片提取血柱的密度分布，并通过胶片的特性曲线将密度分布转换为强度分布。在本文中，我们在计算机上对成像过程进行建模，发现强度分布的半值宽度对聚焦误差相对不敏感。然而，中央光反射的最大强度对聚焦误差仍然敏感。这两个结果均与实验研究一致。
