This study was designed to

examine the stability of basic eye

measurements determined by non-

mydriatic retinography and their use

for personal identification.

Means and standard deviations were calculated for the measurements madein each individual (abscissae and ordinates of the macula, papilla centre and first

bifurcation of the superior temporal vein, STV) using the set of valid dataillustrated in part in Table 1. The criterion used to identify each individual was thematching of all six variables. For each variable, the Thomson test was used to

identify or reject a match.

According to the corresponding principal component analysis (PCA),interindividual discrimination depends in high proportion on the abscissae and

ordinates of the first bifurcation of the STV. For this reason, we then examinedthe use of bifurcation of the ST artery.

REPRODUCIBILITY OF NONREPRODUCIBILITY OF NON--MYDRIATIC RETINOGRAPHIES:MYDRIATIC RETINOGRAPHIES:IMPLICATIONS FOR PERSONAL IDENTIFICATION SYSTEMSIMPLICATIONS FOR PERSONAL IDENTIFICATION SYSTEMS

EVER 2010EVER 2010celiasr@opt.ucm.esceliasr@opt.ucm.es

We estimated the means and deviations of the measurements in eachindividual (abscissae and ordinates of the first ST artery and vein bifurcations)

using the set of valid data.

An error was thus produced when one of the six variables measured in anindividual did not match the individual’s own pattern. The probability of intra-individual error was estimated from the proportion of errors (one or morediscrepancies) in the sample considered (using only the complete datasets

available).

The study sample comprised a set of 864retinographies obtained in 26 subjects aged 18 to 32

years, in which 4 characteristic anatomical structureswere identified.

For each anatomical structure, we determined thecoordinates x,y as the distances from a reference pointat the origin of both axes. This point was the lower leftcorner of the retinography.

The reproducibility of non-mydriatic retinal image measurements was highfor the selected points. However, the abscissae and ordinates of the macula

showed practically no discriminatory capacity and produced an increase in theprobability of intraindividual error. These two variables have thus beeneliminated from subsequent study.

Our findings point to the blood vessels of the retina as key structures onwhich to base the development of new identification security devices.

for personal identification.

Material

Sample

Table 1: Database used to examine the disriminatory capacity of retinographic measurements for 2

of the 4 structures identified. The figures indicate the number of measurements obtained in each

individual.

Table 5: Estimated probabilities of intra-individual error.

Alpha 0.01Number of errors 37

Probability of error 0.04282

Using this method an error is produced if any of the 6 variables in anindividual do not match the individual’s own pattern. The results obtained for

several significance levels are provided below:

Alpha 0.01 0.02 0.05

Probability of error 0.0060 0.0633 0.2048Table 2: Estimated probabilities of the intra-individual error for different levels of

significance for the 6 variables examined

However, if we only consider the variables abscissa and ordinate of the firstbifurcation of the STV, estimated intra-individual errors are:

Alpha 0.01 0.02 0.05Probability of error 0.0030 0.0181 0.0723

Table 3: Estimated probabilities of the intra-individual error for different levels of significance for the variables abscissa and ordinate of the first bifurcation of the STV.

Subject Bifurcation

vein x

Bifurcation

vein y

Bifurcation

artery x

Bifurcation

artery y

1 31 31 31 31

2 32 32 32 32

3 29 29 29 29

4 41 41 41 41

5 30 30 30 30

6 19 19 19 19

7 39 39 39 39

8 28 28 28 28

9 30 30 30 30

10 35 35 35 35

11 8 8 8 8

12 58 58 58 58

13 28 28 28 28

14 17 17 17 17

15 30 30 30 30

16 30 30 30 30

17 12 12 12 12

18 38 38 38 38

19 31 31 31 31

20 31 31 31 31

21 43 43 43 43

22 30 30 30 30

23 34 34 34 34

24 44 44 44 44

25 44 44 44 44

26 41 41 41 41

Total 864 864 864 864

These results indicate a lower probability of error when the data consideredcorrespond to structures such as vessel bifurcations rather than less easily-

defined structures such as the papilla and macula.

1. Boya Vegue J. Atlas de Histología y Organografía microscópica. Médica Panamericana, España, 2002, 393-407.2. Corcóstegui B. El fondo de ojo en la medicina práctica, Espasa, España, 1983, 29-45.3. El Danasoury MA. Prospective bilateral study of night glare after laser in situ keratomileusis with single zone and

transition zono oblation. J Refr Surg 199814 (5): 512-516, 4. Morgan MW. Visual function changes in eyes of aged patients. Vision and Aging: General and Clinical

Perspectives. Ed, A, A, Rosenblom. New York, 1986; 198-200.5. Putz R., Pabst R. Sobotta, Atlas de Anatomía Humana. Tomo I: Cabeza, Cuello, Miembro superior. Médica

Panamericana, Buenos Aires, Madrid, 2006, 362-370.6. Rodríguez S., Smith-Agreda J.M. Anatomía de los órganos del lenguaje, visión y audición. Médica Panamericana,

España, 1999, 250-270.7. Young B., Heath J.W. Wheater´s Histología Funcional. Elsevier España S.A., 2005, 382-391

Material

Figure 2: Focusing the TRC-NW200 retinographer

The retinographer used was theTRC-NW200 by Topcon that does not

require pharmacological mydriasis.Using a corrective lens, images can beobtained in ammetropic eyes of up to -

33 diopters in myopes and +40 inhyperopes.

To further constrain the estimation of this probability of error, we can assume

that the different variables in the individuals behave as independent variables andthen by estimating the probability of an interindividual match for each one(probability of error) the probability of the whole set of variables matching can be

calculated (interindividual probability of error).

The results obtained for this assumption are shown in Table 4.

This study was supported by a formal agreement between the Complutense University

of Madrid and Alta Eficacia Tecnología SL.

MAC X MAC Y BIF X BIF Y PAP X PAP YTOTAL 6 variables

TOTAL 2 variables

Alpha Probability of error

0.01 0.875 0.9 0.0875 0.06667 0.47917 0.63333 0.00139 0.00580.02 0.85 0.85833 0.07917 0.05833 0.43333 0.5875 0.00086 0.00460.05 0.79167 0.7875 0.07083 0.05 0.3375 0.52083 0.00039 0.0035

Tabe 4: Estimated probabilities of the inter-individual error for different levels of significance assuming the independence of variables.

The resolution of the image captured by the CCD camera is 3.15 million pixels.The angle captured is 45º for pupils larger than 4.00 mm and 30º for pupil sizes of

3.70 mm.

Non validretinography

Valid retinography

Pupil diameter <3.70 mm

Pupil diameter >3.70 mm

Figure 5: Artery and vein patterns of the retina in the left and right eyes

Figure 3: Example of the quality of the images obtainedFigure 4: Correct position of the subject for image capture. The

outer corner of the eye is aligned with a line in the instrument.