What is a Jaeger number anyway? And while we’re at it, how does it really apply to a patient’s level of reading capacity? In the clinical setting, we all too often overlook the nuances of near vision testing, forging ahead to obtain the quick and relatively standard measurement in US practice of “J-something.” Maybe you simplify it even further and merely record a Snellen equivalent such as “20/20” for a patient’s near vision testing. But does this really represent an accurate measure of a patient’s near vision?
To successfully treat presbyopia, we must first address the difficulties in truly quantifying a patient’s level of near visual acuity and the factors that contribute to random variability. After all, patients have no concept of the difference between testing J1 or J5. They just want to read! Perhaps the same is true of many surgeons who eagerly look for that particular Jaeger number that might translate into the successful treatment of a patient’s presbyopia. Although this may bring a high level of satisfaction to that particular surgeon, we must be cautious and remember that there is a significant difference between near visual function and functional near vision.
Consider the typical measurement of a patient’s near visual function: an ideal testing environment, high-contrast letters on a white card, the card held by a patient at any optimal distance to provide the highest level of resolution, and perhaps even a lamp present to provide enhanced illumination. In essence, it is an artificial environment created to test a patient’s capacity for letter recognition alone. This measurement of visual function certainly does not relate to the patient’s functionality. Now consider the patient’s measure of functional near vision: an ability to resolve reading material in real-life environments, where lighting, contrast, and numerous other parameters can vary significantly. Our myopic focus on a patient’s ability to see 5 letters on a near card might not necessarily spell success in a patient’s day-to-day capabilities for near vision.
Beyond the environmental factors at play, we must remember that the act of reading is a complex interaction involving the cerebral processing of thoughts and ideas through the identification of visual stimuli created by printed shapes and symbols. Reading can be affected not only by presbyopia, but also by refractive error, medications, trauma, systemic illness, and mental status. In considering these facts, the metrics of successful near vision might include an assessment of the patient’s reading speed, reading comprehension, and reading accuracy. This is not to say that patients should be tested in the office with a timer in hand followed by an oral book report, but merely we should consider the factors that make up true measures of success in a patient’s functional near vision.
As we continue to strive for the optimal treatment of presbyopia, we need to take these flaws in our day-to-day testing to heart. We need to develop standards that can be more representative of functional near vision, as opposed to only that of letter recognition in synthetic environments. We should be interested in developing a universal measure of sustainable reading performance. Until we truly account for these issues, perhaps we would be better served by including a measure of the patient’s subjective evaluation of near vision in addition to the objective measure of a Jaeger number. After all, we are all aware of patients who test J1+ with progressive glasses or multifocal IOLs, only to complain bitterly of an “inability to read.” There’s good reason: objective measures of near visual acuity thresholds represent a fraction of the subjective satisfaction and quality-of-life outcomes in our goal of treating presbyopia.