Central lens opacities are likely to interfere with vision clinically. The method of Mehra and Minassian for grading central lens opacities is based on the area of the lens opacity obscuring the red reflex relative to the area of the clear red reflex. This is a rapid test that is useful in prevalence and epidemiological studies and which gives consistent results between observers.
Method:
(1) The pupil is undilated.
(2) A direct ophthalmoscope is used to observe the red reflex, set at +2 D and held approximately 33 centimeters from the eye.
Finding
Grade
clear red reflex, no opacities
0
few small dot opacities in the lens appearing as tiny scattered dark spots in the red reflex. Maximum area occupied by dots 1 square mm.
1
lens opacity obscuring part of the red reflex. Area obscured is smaller than area of clear red reflex
2A
lens opacity obscuring part of the red reflex. Area obscured equal to or larger than area of clear red reflex.
2B
lens opacity totally obscuring the red reflex
3
aphakia or displaced lens
4
unable to assess red reflex due to corneal opacity, etc.
5
after Table 1, page 802, Mehra (1988)
where:
• aphakia = absence of the lens
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