Vision screener
Generally, the present invention relates to medical devices and a method of vision screening, and more particularly to a pediatric vision screening system and method thereof that identifies a risk factor for amblyopia or diagnoses amblyopia by measurement of microstrabismus. An embodiment of the invention is directed to a method of patient screening for risk factors for amblyopia which includes the steps of illuminating the eye with polarized light, scanning the polarized light about the eye, capturing the retro-reflected light emanating back from the eye, analyzing the retro-reflected light to determine ocular misalignment; and calculating a metric to determine if the patient passes or fails the screening test thereby providing an indication that the patient may have a risk of amblyopia based on either strabismus or anisometropia. The method is effective at detecting amblyopia related to focusing problems without the measuring the focus of the eye directly.
1. A method of detection of microstrabismus in order to diagnose amblyopia, comprising the steps of:
a) illuminating the eye with polarized light;
b) scanning the polarized light about the eye;
c) capturing the retro-reflected light emanating back from the eye;
d) analyzing the retro-reflected light to determine ocular misalignment without measuring for focus; and
e) calculating a metric to determine if the patient has evidence of microstrabismus which thereby diagnoses amblyopia.
2. The method of claim 1 wherein the polarized light is linearly polarized.
3. The method of claim 1 wherein the polarized light is circularly polarized.
4. The method of claim 1 wherein scanning the polarized light includes periodic rotation of light at a predetermined oblique angle to the eye and at a predetermined angular frequency.
5. The method of claim 4 wherein scanning the polarized light includes periodic rotation of light at a predetermined oblique angle to the eye and at a predetermined angular frequency delivered to both eyes simultaneously.
6. The method of claim 4 wherein scanning the polarized light includes periodic rotation of light at a predetermined oblique angle and a predetermined angular frequency delivered to both eyes sequentially.
7. The method of claim 1 wherein capturing the retro-reflected light includes an optical detector disposed optically conjugate to the light source and the eye.
8. The method of claim 1 wherein analyzing includes polarization filtering of the retro-reflected light into orthogonal components.
9. The method of claim 8 wherein analyzing includes subtracting the filtered orthogonal polarization components.
10. The method of claim 1 wherein analyzing includes comparing the frequency spectrum of the retro-reflected light to the angular frequency of light incident upon eye.
11. The method of claim 1 wherein calculating the ocular misalignment of the eye includes determining whether the angular offset exceeds a predetermined threshold value.
12. The method of claim 1 wherein the metric is a binocularity score given by
Binocularity
=
Number
of
bilateral
readings
Number
of
unilateral
readings
+
Number
of
bilateral
readings
×
100
%
.
13. The method of claim 12 wherein a predetermined minimum threshold above which is needed to classify the patient as “passed”, otherwise “refer”.
14. The method of claim 1 wherein the step of calculating the metric is conducted multiple times and further includes the step of detecting a lack of eye fixation, indicating the possibility of anisometropia.
15. The method of claim 14 wherein calculating non repeating binocularity scores indicates a risk factor for anisometropia.
16. The method of claim 15 wherein if said non repeating binocularity scores exceed a predetermined clinically established threshold, the patient is indicating a risk factor for amblyopia.
17. The method of claim 15 wherein a mean value and standard deviation is calculated from multiple binocularity scores.
18. The method of claim 15 wherein if the deviations in the binocularity scores vary by more than 2 standard deviations from the mean binocularity score, the patient is indicating a probability of a risk factor for amblyopia.
19. The method of claim 15 including the step of calculating the variability in repetitive binocular score determinations and if the standard deviation of repetitive scores exceeds a predetermined clinically established threshold, the patient is indicating a probability of a risk factor for amblyopia.
20. A method of detection of microstrabismus in order to diagnose amblyopia, comprising the steps of:
a) illuminating the eye with polarized light;
b) scanning the polarized light about the eye;
c) capturing the retro-reflected light emanating back from the eye;
d) analyzing the retro-reflected light to detect eye wandering without measuring focal differential between eyes; and
e) calculating a metric to determine if the patient has evidence of microstrabismus which thereby diagnoses amblyopia.
21. The method of claim 20 wherein the step of calculating includes performing scan to scan frequency spectrum analysis.
22. The method of claim 21 wherein frequency spectrum analysis includes fast Fourier transform techniques.
23. The method of claim 20 wherein the step of calculating includes repetitive binocular score determinations.
24. The method of claim 21 including the step of calculating the ratio of the captured signal at the scanning frequency to the captured energy at the frequency doubled scanning frequency, and if the ratio does not exceed a predetermined clinically established threshold, the patient is indicating a probability of a risk factor for amblyopia.