Defocus Curves Show Emerging Presbyopia Reduces Near Vision As Patients Age

Defocus curves of patients with emerging presbyopia demonstrate decreasing visual acuity that rapidly worsens between the ages of 46 and 48, with very-near vision beginning to significantly decline at the age of 40, according to research published in Clinical Ophthalmology. These defocus curve studies can help clinicians predict expected intermediate and near visual acuity with specific lenses.

Healthy phakic adults (N=60) volunteered for this prospective analysis, conducted at a single facility (ClinicalTrials.gov Identifier: NCT04474782). Participants exhibited bilateral best-corrected visual acuity (BCVA) of 20/20 or better, and were divided into 4 groups: 14 who were 37 and 39 years of age, 16 aged 40 to 42 years of age, and 15 each in the 43 to 45 years and 46 and 48 years of age groups. 

The researchers determined individuals’ manifest refraction with a phoropter and positioned trial set lenses in a trial frame. They also assessed BCVA according to early treatment diabetic retinopathy study (ETDRS) chart and applied loose lenses in steps from +0.50 D to -3.00 D to the front of the trial frame, converting acuity values to logarithm of the minimum angle of resolution (logMAR).

The study affirmed the relationship of progressive decrease in near vision along with years of life, including very-near acuity significantly worsening after age 40. Specifically, VA began and continued to decrease at defocus step -0.50 D in the 4 groups (P <.0002, P =0, P =0, P =0), respectively. Participants 46–48 years of age displayed significantly reduced VA from steps -1.00 D to -2.00 D compared with the remaining groups (P <.037, P =.022, P =.017). Beginning at 40 cm near point, the youngest group showed significantly better logMAR vision compared with individuals 46 to 48 years of age (P =.001).

“Eye care providers will now be able to directly inform patients that following cataract surgery, vision at different ranges will be most similar to when they were a certain age,” according to the analysis. Looking at defocus curves based on life years may help patients develop realistic expectations for what their vision will be like after cataract surgery or other treatments. Investigators list the expanding array of treatments for presbyopia as including multifocal, extended depth of focus, pseudo-accommodative intraocular lenses (IOLs), and pharmacological options.

Clinical trials for IOLs have built defocus curves with a step at -1.50 D to signify intermediate sight at 66 cm, and the step of -2.50 D for near vision at 40 cm. Previous studies have found eye strain from under-corrected or uncorrected presbyopia may cause lower computer-focused work productivity and possible social isolation from reduced ability to participate in screen-based recreational activities.

The sample included 96.7% Caucasian, and 50% women. Limitations of this analysis include curves for ages 37 to 48 only, lack of racial diversity, and no exploration for the effect of refractive error on visual acuity at defocus steps. Investigators added that this binocular defocus curve set is the first to illustrate curves not specific to an IOL, but for phakic individuals with emerging presbyopia.

Disclosures: This study was financially supported by Alcon. Several investigators have disclosed affiliations with Alcon, and/or the biotech, medical device, or pharmaceutical industries. Please see the original reference for complete disclosures.