We all have patients who measure 20/20 but still have vision complaints. These situations can be frustrating, because the patient is usually right—something else is hindering their vision. These newer diagnostic tools can help you think beyond visual acuity to diagnose any number of conditions.
Black on White
Rarely do you see such extreme contrast as black letters on a white background in the real world, and yet that is what we use to test subtle vision changes. Our trusty Snellen chart, introduced back in 1862, still works, even though we know it may not be a truly sensitive test of vision.
But we now have access to better testing to augment our visual acuity testing. Contrast sensitivity testing (M&S Technology) can identify subtle vision changes due to everything from cataracts to retinal disease. Research shows contrast color testing (Konan Medical) is far superior to Ishihira plates, which can miss more than 50% of protanopes.1 Point-spread-function (PSF) images with the VMax PSF phoropter (VMax Vision) helped a second-year optometry student provide more accurate refractions compared with three faculty members (with more than 50 years of refracting experience between them) using a standard manual phoropter.2
For many, the crystalline lens becomes dysfunctional long before insurance will cover a cataract procedure. Some may even argue that presbyopia is the beginning of notable lens dysfunction. As the lens continues to grow, it starts with presbyopic issues and then begins to scatter light. Thus, devices such as the HD analyzer (Visiometrics) can be valuable in detecting pathology based on light scatter from the lens or tear film.
Other helpful technologies include those with Scheimpflug imaging capabilities. Clinicians can capture Scheimpflug images with the camera perpendicular to the slit beam, imaging about 25,000 data points to create a 3-D model of the anterior segment. The Pentacam (Oculus), Galilei (Ziemer) and now the VX130 (Visionix) all include Scheimpflug imaging, which can reveal pathology ranging from subtle keratoconus to early refractive lens changes, even in patients seeing 20/20 vision.
Ocular Issues Front to Back
Although dry eye disease (DED) typically manifests with fluctuating vision, many of these patients measure 20/20 and complain of blurry vision. Diagnostic tools such as the Keratograph 5M (Oculus), LipiView (Johnson & Johnson Vision) and osmolarity testing (TearLab) can help reveal an underlying DED etiology.
In retinal disease, patients with early epiretinal membranes and mild diabetic macular edema may still test 20/20. Here, OCT imaging is key. Most early macular degeneration remains undiagnosed, even though patients with early signs will have night vision issues while still measuring 20/20 on high contrast testing. More sensitive tests such as dark adaptometry (AdaptDx, Maculogix) can uncover the diagnosis in about six minutes.
When things just don’t add up, consider neurological diseases affecting the eye and use pupil testing, color vision and visual field testing. While the swinging flashlight test can be difficult and doesn’t identify a subtle RAPD without filters, a new technology, Eyekinetix (Konan Medical), provides an RAPD assessment in less than 40 seconds and can identify subtle asymmetry indicating neurological disease or neuropathies such as glaucoma.
The 20/blurry patient is both a challenge and an opportunity. Most of these patients have seen multiple doctors and are still searching for answers. Our ability to listen carefully, measure more effectively and use advanced diagnostics and clinical acumen can provide some much-needed insight into these cases.
This is what separates us from remote refractions; we complete an entire ocular health assessment, benefiting both the patient and our practice. It’s well worth the effort.
Note: Dr. Karpecki consults for companies with products and services relevant to this topic.
1. Birch J. Efficiency of the Ishihara test for identifying red-green colour deficiency. Ophthalmic Physiol Opt. 1997;17(5):403-8.
2. Newman C, Lievens C, Kabat A, Weber J. Repeatability of the Vmax voice activ subjective refractor (VASR) and traditional refractive methods in a healthy population. Poster presented at 2018 ARVO Annual Meeting, April 29, 2018, Honolulu, Hawaii.