Computerized analysis of retinal vessel width and tortuosity in premature infants.
OBJECTIVE
To determine, with novel software, the feasibility of measuring the tortuosity and width of retinal veins and arteries from digital retinal images of infants at risk of retinopathy of prematurity (ROP).


METHODS
The Computer-Aided Image Analysis of the Retina (CAIAR) program was developed to enable semiautomatic detection of retinal vasculature and measurement of vessel tortuosity and width from digital images. CAIAR was tested for accuracy and reproducibility of tortuosity and width measurements by using computer-generated vessel-like lines of known frequency, amplitude, and width. CAIAR was then tested by using clinical digital retinal images for correlation of vessel tortuosity and width readings compared with expert ophthalmologist grading.


RESULTS
When applied to 16 computer-generated sinusoidal vessels, the tortuosity measured by CAIAR correlated very well with the known values. Width measures also increased as expected. When the CAIAR readings were compared with five expert ophthalmologists' grading of 75 vessels on 10 retinal images, moderate correlation was found in 10 of the 14 tortuosity output calculations (Spearman rho = 0.618-0.673). Width was less well correlated (rho = 0.415).


CONCLUSIONS
The measures of tortuosity and width in CAIAR were validated using sequential model vessel analysis. On comparison of CAIAR output with assessments made by expert ophthalmologists, CAIAR correlates moderately with tortuosity grades, but less well with width grades. CAIAR offers the opportunity to develop an automated image analysis system for detecting the vascular changes at the posterior pole, which are becoming increasingly important in diagnosing treatable ROP.
Wilson
Clare M
CM
Department of Optometry and Visual Science, City University, Northampton Square, London, United Kingdom. clarewil25@yahoo.com
Cocker
Kenneth D
KD
Moseley
Merrick J
MJ
Paterson
Carl
C
Clay
Simon T
ST
Schulenburg
William E
WE
Mills
Monte D
MD
Ells
Anna L
AL
Parker
Kim H
KH
Quinn
Graham E
GE
Fielder
Alistair R
AR
Ng
Jeffrey
J
D003198:Computer Simulation; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007231:Infant, Newborn; D007234:Infant, Premature; D008954:Models, Biological; D010781:Photography; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000002:abnormalities* / Q000473:pathology*; D012178:Retinopathy of Prematurity / Q000473:pathology*