Objective Quantification Of Depth Of Focus In Pseudophakic Eyes

To derive a method to quantify the objective depth-of-focus (DOF) using visual Strehl’s ratio based on Optical Transfer Function (VSOTF) on ray tracing (Tracey) aberrometer which can be comparable to clinical DOF obtained from the clinical defocus curve in two groups of pseudophakic eyes with different aspheric profiles.

Sussex Eye Hospital, University Hospitals Sussex NHS Foundation Trust, Brighton. UK &

Tracey Technologies, Huston, USA.

Two groups of patients implanted with negatively aspheric (Eyhance, J&J) and aspherically neutral (RayOne, Rayner) were assessed between 3-9 months for LogMAR distance and intermediate vision, 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: To determine the specific threshold of VSOTF which matches the subjective DOF. Secondary outcome: LogMAR unaided distance (UCDVA) and intermediate visual acuity (UIVA), corrected distance (CDVA) and distance-corrected intermediate visual acuity (DCIVA), manifest refraction, pupil size, iTrace aberrometric scan size and relationship of peak VSOTF vs. DOF.

Date from 43 eyes with Eyhance and 42 RayOne IOLs were available. Primary outcome measure: A 30% threshold of VSOTF was found equivalent to the subjective DOF. Secondary outcomes: LogMAR UCDVA & UCIVA was significantly better with Eyhance (0.04 ± 0.09 vs. 0.10 ± 0.12, p= 0.02 and 0.29 ± 0.15 vs. 0.38 ± 0.15, p= 0.02). DCIVA was better with Eyhance (0.27 ± 0.17 vs. 0.37 ± 0.10, p=0.01). Manifest refraction was 0.28D±0.47 for Eyhance compared to 0.45 D ± 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). Multiple factors influence peak VSOTF in pseudophakic eyes.

Our study showed that 30% threshold of VSOTF values on Tracey measurements (Nanavaty Threshold) gives an objective estimate of DOF which is equivalent to clinical depth of focus derived from defocus curve. This threshold measurement on Tracey is likely to replace the existing laborious defocus curve assessment in pseudophakic eyes.