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    Diagnosing early-stage AMD with a dark adaptation device

    Measuring dark adaptation impairment useful in screening for early AMD



    Research findings

    I recently collected data for six patients (aged 60 to 75 years) who were known before DA testing with the device to have AMD.  Five of the six patients had a corrected visual acuity of 10/10 P2 in both eyes (except one who was monophthalmic); the other patient had a corrected visual acuity of 6.3/10 P2 in both eyes.


    As expected, all six patients had severely impaired dark adaptation (an RI greater than 6.5 minutes in one or both eyes) consistent with AMD. This is perhaps not surprising given that drusen cause degeneration of retinal pigment epithelium cells, which may in turn cause hypoxia and mechanical stress to the photoreceptors.


    More interestingly, I also undertook a consecutive case series study that included 16 patients (aged 60 to 80 years) who presented with normal retinal health based on clinical examination. Of these 16 clinically normal patients, 10 were confirmed to be AMD-free by DA (an RI of less than 6.5 min in both eyes) but six were discovered to have subclinical AMD (an RI greater than 6.5 min in one or both eyes). 


    Thus, a surprising 38% (six of 16) of the patients with clinically normal retinal health actually had undiagnosed AMD. Although this was only a small study, these findings are important because they highlight that early-stage AMD cannot and should not be ruled out in older patients with a normal retina examination and good visual acuity.


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