# Zonular fibre Insertion-to-Limbus Distance (ZLD): normative data to assess lens position and diagnose ectopia lentis

## TL;DR

This study establishes a new method to measure lens position using the Zonular Lens Distance (ZLD), providing normative data to help diagnose lens subluxation and related disorders.

## Contribution

The study introduces ZLD as a novel parameter to assess lens position and quantify ectopia lentis with normative data from healthy subjects.

## Key findings

- Average ZLD in healthy eyes is 1.34 mm with a range of 0.7–2.1 mm.
- Older age is associated with larger ZLD (P = 0.036).
- Smaller pupil diameter correlates with larger ZLD (P < 0.001).

## Abstract

Subluxation of the crystalline lens (Ectopia Lentis, EL) can lead to significant visual impairment and serves as a diagnostic criterion for genetic disorders such as the Marfan syndrome. There is no established criterion to diagnose and quantify EL. We prospectively investigated the distance between the zonular fibre insertion and the limbus (ZLD) in healthy subjects as a parameter to assess the position of the lens, quantify EL and provide normative data.

This prospective, observational, cross-sectional study includes one-hundred-fifty eyes of 150 healthy participants (mean age 28 years, range 4–68). Pupils were dilated with tropicamide 0.5% and phenylephrine 2.5% eyedrops. ZLD was measured in mydriasis at the slit lamp as the distance between the most central visible insertions of the zonular fibres on the lens surface and the corneoscleral limbus. Vertical pupil diameter (PD) and refractive error were recorded. If zonular fibre insertions were not visible, the distance between limbus and the pupillary margin was recorded as ZLD.

145 right and 5 left eyes were examined. 93% of study subjects were Caucasian, 7% were Asian. In eyes with visible zonular fibre insertions (n = 76 eyes), ZLD was 1.30 ± 0.28 mm (mean ± SD, range 0.7–2.1) and PD was 8.79 ± 0.57 mm (7.5–9.8). In the remaining 74 eyes, ZLD was 1.38 ± 0.28 mm (0.7–2.1), and PD was 8.13 ± 0.58 mm (6.7–9.4). For all eyes, ZLD was 1.34 ± 0.29 mm (0.7–2.1), and PD was 8.47 ± 0.66 mm (6.7–9.8). Refractive error and sex did not significantly affect ZLD. Smaller PD and older age were associated with larger ZLD (P < 0.001 and P = 0.036, respectively).

Average ZLD was 1.34 mm in eyes of healthy subjects. Older age correlated with larger ZLD. These normative data will aid in diagnosing and quantifying EL.