Computerized analysis of retinal vessel width and tortuosity in premature infants.

PURPOSE: 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.

Optic disk size and optic disk-to-fovea distance in preterm and full-term infants.

PURPOSE: Few studies have assessed optic disk and retinal morphology in infants. Here the optic disk and optic disk-to-fovea distance were measured in preterm and full-term infants in vivo. METHODS: Optic disk (OD) dimensions and the center-to-center distance between the OD and the macula were measured using digital imaging in infants undergoing routine ophthalmic examinations. Postmenstrual age of the mother at the time of examination ranged from 32 to 50 weeks. From each image, the OD-to-fovea distance (ODF) and the OD height (ODH) and OD width (ODW) were measured. RESULTS: In 51 retinal images from 51 infants, mean +/- SD values obtained were 4.4 +/- 0.4 mm (ODF), 1.41 +/- 0.1 9 mm (ODH), and 1.05 +/- 0.13 mm (ODW). These dimensions did not change significantly over the age range studied. The mean value for the ratio between ODF and mean OD diameter (ODF/DD) was 3.76. CONCLUSIONS: Results of this in vivo study suggest that though the optic nerve head diameter increases by more than 50%, only limited growth occurs at the highly organized area of the posterior pole from birth to adulthood. This study discusses the finding of a large-angle kappa in infants and the use of a disk macula/disk diameter ratio in the diagnosis of optic nerve hypoplasia.