Subjective Versus Objective Depth Of Focus Comparison In An Aspherically Neutral Monofocal Intraocular Lens And Negatively Aspheric Enhanced Monofocal Intraocular Lens

To evaluate and compare the subjective versus objective depth of focus (DOF) in pseudophakic eyes implanted with either aspherically neutral monofocal (RayOne Rayner, UK) or a negatively aspheric enhanced monofocal (Tecnis Eyhance, Johnson & Johnson, USA) intraocular lenses (IOLs).

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

In this prospective, randomised, comparative study, 50 patients (100 eyes) were randomised to receive the same IOL bilaterally. Observations: Follow-ups were at 3-9 months post-surgery. The patients underwent uniocular LogMAR vision for distance and intermediate, refraction, defocus curves and iTrace assessments for objective DOF values. The subjective refraction data of defocus curve were converted to give equivalent DOF measurements. Primary outcome measure: DOF assessed on iTrace versus DOF values derived from defocus curve. Secondary outcome measures: LogMAR unaided distance and intermediate visual acuity, corrected distance and distance-corrected intermediate visual acuity at 66cm, pupil size and iTrace aberrometric scan size.

A total of 45 patients were enrolled in the study, of which 44 eyes had the Tecnis IOL and 46 eyes, the RayOne IOL. Subjective assessment of DOF for Eyhance Vs. RayOne 3-9 months were 2.60D±0.67D Vs. 2.09D±0.45D (p<0.01) and objective DOF from iTrace were 1.64D±0.83D Vs. 1.15D±1.37D (p=0.05). Primary outcome measure: Subjective DOF from defocus curve was significantly higher than objective DOF from iTrace in both IOL groups (p<0.01). Manifest refraction was 0.28D ±0.47 for Eyhance compared to 0.45D ± 0.50 for RayOne (p= 0.13). Pupil size on iTrace was 4.34± 0.50 for Eyhance vs 3.99±0.96 for RayOne (p<0.04). Scan size at 3-9 months was 2.79±0.55 for Eyhance vs 2.69±0.62 for RayOne (p= 0.40).

This study shows that there is a significant difference in subjective and objective assessment of DOF for the two groups of IOLs. iTrace appears to underestimate the depth of focus compared to subjective refraction. This is because the scan size is smaller than the pupil size and the visual axis is not always at the centre of the pupil. Eyhance gave better subjective measurements compared to RayOne with no significant difference in objective measurements. Subjective measurement of DOF appears to be more useful than objective assessment in undilated pupils.