Possible errors in the measurement of retinal lesions.

PURPOSE To determine the accuracy of the measurement of structure in the retina from fundus photographs. METHOD A model eye was developed to measure the retinal image size of the Zeiss fundus camera. A x 10 microscope objective with a focal length of 16.41 mm was used together with a microscope graticule. RESULTS Under emmetropic conditions the difference between the calculated and the measured magnification was 8.6%. The total change in magnification from myopia to hyperopia was -24.63% to +18.1%. When the camera position was altered with respect to the model eye by +/- 5 mm under myopic conditions the change in magnification was -4.5% and +6.8%. In the hyperopic condition the change was -5.6% to +4.6%. CONCLUSIONS Measuring the size of structure in the retina from photographs may therefore prove to be inaccurate but in some circumstances determining the percentage change in size may prove more reliable.

[1]  W. Lotmar.  DEPENDENCE OF MAGNIFICATION UPON THE CAMERA‐TO‐EYE DISTANCE IN THE ZEISS FUNDUS CAMERA , 1984, Acta ophthalmologica.

[2]  K Taylor,et al.  Automatic geometrical registration of fluorescein retinal angiograms. , 1990, Computers and biomedical research, an international journal.

[3]  C. Blauth,et al.  Demonstration of cerebral microemboli occurring during coronary artery bypass graft surgery using fluorescein angiography. , 1990, The Journal of audiovisual media in medicine.

[4]  C E Krakau,et al.  SOME ESSENTIAL OPTICAL FEATURES OF THE ZEISS FUNDUS CAMERA , 1977, Acta ophthalmologica.

[5]  Kenneth M. Taylor,et al.  Quantification of retinal damage during cardiopulmonary bypass: comparison of computer and human assessment , 1990 .

[6]  P. Baumbach,et al.  Absolute ocular fundus dimensions measured by multiple-beam interference fringes. , 1989, Investigative ophthalmology & visual science.

[7]  M. Snead,et al.  Calculated versus A-scan result for axial length using different types of ultrasound probe tip , 1990, Eye.

[8]  Influence of oxygenator type on the prevalence and extent of microembolic retinal ischemia during cardiopulmonary bypass. Assessment by digital image analysis. , 1990 .

[9]  C. Blauth,et al.  RETINAL MICROEMBOLISM DURING CARDIOPULMONARY BYPASS DEMONSTRATED BY FLUORESCEIN ANGIOGRAPHY , 1986, The Lancet.

[10]  P. Romano,et al.  Optic disc photogrammetry: magnification factors for eye position, centration, and ametropias, refractive and axial; and their application in the diagnosis of optic nerve hypoplasia. , 1989, Annals of ophthalmology.