Angle Kappa And Unaided Reading Speed In Pseudophakic Eyes With Monofocal Intraocular Lens

The aim of this study was to assess the relationship between angle kappa (k) and the unaided reading speed & smallest font size in pseudophakic eyes following implantation of an monofocal intraocular lens aimed at an emmetropic refractive outcome.   

University Hospitals Sussex NHS Foundation Trust, Brighton, United Kingdom.

This was a prospective, single eye study on patients undergoing routine cataract surgery with an aspherically neutral monofocal IOL and expected to achieve 20/40 or better unaided vision. Eyes with surgical complications or co-existing ocular pathology were excluded.  At 3-9 months post-surgery, manifest refraction, uncorrected & best-corrected distance (UCDVA & BCDVA) & uncorrected near (UCNVA) LogMAR acuity, spherical equivalent (SEQ) was assessed. Angle k was assessed on iTrace (Tracey Technologies, USA) and unaided reading speed and smallest print size were assessed using the Salzburg Reading Desk.  

Out of 412 recruited patients, data on 301 patients were available (99 dropped out due to the Covid pandemic, 10 lost for follow-ups and 2 died). Median UCDVA, BCDVA, UCNVA and SEQ were 0.14LogMAR (IQR= 0.02 to 0.24 LogMAR), 0LogMAR(IQR=-0.08 to 0.02) and 0D(IQR=-0.13D to -0.07D) respectively. The unaided reading speed was 100-150wpm in 42.8% followed by 151-200wpm in 26.1%. 30.9% read 0.4-0.5 LogMAR followed by 10.8% for 0.3-0. Mean angle k was 2.42±1.66degrees (95% CI: 2.35-2.48degrees). Angle k was negatively correlated with unaided reading speed (R=-0.18, p=0.01) but there was no significant correlation with smallest reading font (R=-0.08, p=0.21).

Angle kappa significant affects unaided reading speed and not the smallest font size in monofocal pseudophakic patients. Larger angle kappa has reduced unaided reading speed.