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Park and Park: 10-Prism-Diopter Fixation Test for Amblyopia
Original Article

J Korean Ophthalmol Soc 2009;50(2):269-274.

Published online: 3 January 2009

DOI: https://doi.org/10.3341/jkos.2009.50.2.269

10-Prism-Diopter Fixation Test for Amblyopia

Joo Youn Park, MD, Song Hee Park, MD

Department of Ophthalmology, Soonchunhyang University College of Medicine, Seoul, Korea

Address reprint requests to Song Hee Park, MD Department of Ophthalmology Soonchunhyang University College of Medicine #657 Hannam‐ dong, Yongsan‐ gu, Seoul 140‐743, Korea Tel: 82‐2‐709‐9354, Fax: 82‐2‐798‐7797, E-mail: scheye@hosp.sch.ac.kr

Received 12 September 2008       Accepted 24 November 2008

Copyright © 2009 Korean Ophthalmological Society

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To evaluate the clinical usefulness of the 10-prism-diopter (PD) fixation test in the diagnosis of amblyopia.

Methods

The study comprised 132 children (42 normal, 90 amblyopes) who underwent the 10-PD fixation test and stereoacuity test. The sensitivity, specificity, false-positive and false-negative rates of the 10-PD fixation test were analyzed according to the clinical diagnosis.

Results

The 10-PD fixation test sensitivity was 86%, the specificity was 61%, the false-positive rate was 17% and the false-negative rate was 24%. Data showed agreement between the 10-PD fixation test and the stereoacuity test (γ=0.737, p=0.000). The results in the 10-PD base-down test and base-out test also showed agreement (γ=0.779, p=0.000).

Conclusions

The 10-PD fixation test is a simple and useful method in detecting amblyopia.

Keywords: Amblyopia, 10 prism diopter fixation test

References

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Figure 1.
Responses to 10-PD base-out test. We regarded A and B as positive response that means equal fixation preference, C and D as negative response or suppression. (A) Non fixating eye (right eye) makes convergence and left eye maintain fixation while also converging. (B) Both eyes make version movement to the opposite side on which the prism was placed, followed by a convergence to the fixation target. (C) Version movement of both eyes, with no convergence. (D) No movement of either eye.
jkos-50-269f1.tif
Table 1.
Baseline characteristics of patients
Amblyopia group
 Normal group p*
strabismic amblyopia anisometric amblyopia
Age at time of test performed (years) 7.2±1.5 7.6±1.8 6.4±2.4 0.305
Visual acuity of amblyopic eye 0.48±0.16 0.44±0.19 - 0.125
Total 90 42 -

* Statistical significance was tested by paired-t test. p<0.05.

Table 2.
Definitions of sensitivity, specificity, false-positive, and false-negative rates in the diagnosis of amblyopia
Clinical Test t Amblyopia Normal Total
Amblyopia A B A+B
Normal C D C+D
Total A+C B+D A+B+C+D

Sensitivity=A/(A+B); Specificity=D/(C+D); False-positive rate=C/(A+C); False-negative rate=B/(B+D)

Table 3.
The results of 10-prism-diopter fixation test
Clinical 10-PD test* Amblyopia Normal Total
Amblyopia Strabismic amblyopia 32 4 36
Anisometropic amblyopia 50 4 54
Normal 17 25 42
Total 99 33 132

* 0-PD test=both 10-prism-diopter base-down and base-down test.

Table 4.
The results of stereopsis
Clinical Stereopsis Amblyopia Normal Total
Amblyopia 77 13 90
Normal 9 33 42
Total 86 46 132
Table 5.
Comparison of results in 132 patients examined by 10-PD base-down test (left) and 10-PD base-out test (right)
10-PD* base-down test
 10-PD* base-out test
Amblyopia Normal Amblyopia Normal
Amblyopia 72 18 69 21
Normal 12 30 12 30
Total 84 48 81 51

* PD=prism diopter.

Table 6.
Comparison of sensitivity, specificity, false-positive rates and false-negative rates of 10-PD base-down and 10-PD base-out test.
10-PD* 10-PD*
base-down test base-out test
Sensitivity 80% 76%
Specificity 71% 71%
False-positive rate 14% 15%
False-negative rate 37% 41%

* PD=prism diopter.

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