IOL Position and Refractive Change After Nd:YAG Laser Posterior Capsulotomy

Summary

After cataract surgery, the thin natural membrane that holds the artificial lens in place can slowly turn cloudy. This is called posterior capsule opacification. It makes vision blurry and can cause glare. The standard treatment is a short, painless laser procedure called Nd:YAG capsulotomy, which opens a small clear window in the cloudy membrane.

Opening this membrane changes the support structure around the artificial lens. Eye doctors do not agree on what happens next. Some studies found that the lens shifts slightly backward in the eye after the laser treatment, some found that it shifts forward, and some found no movement at all. It is also unclear whether such a small shift changes how well a person sees or the strength of their glasses. One reason for these mixed results may be that each study used a different imaging device, and these devices measure the depth of the front chamber of the eye in different ways.

This study measures the position of the artificial lens in the same eye with three different imaging devices, before and after the laser treatment. The devices are called IOLMaster 700, CASIA2, and Pentacam AXL. All three take detailed pictures of the front of the eye without touching it. The study team wants to find out whether the artificial lens moves after the laser treatment, how much it moves, whether any movement changes vision or the glasses prescription, and whether the three devices give matching results.

Who can take part

People who had cataract surgery at least three months ago, who now have a cloudy membrane behind the artificial lens, and whose eye doctor has already decided that the laser treatment is needed.

What taking part involves

Taking part does not change the laser treatment in any way. The decision to perform the treatment, the technique, and the laser settings are made by the treating doctor for medical reasons and are not influenced by the study. The study only adds extra measurements before and after the treatment.

There are three study visits:

* Visit 1, on the day of the laser treatment and before the laser is used. The extra measurements take about 30 to 45 minutes.
* Visit 2, about one week after the treatment. The extra measurements take about 15 to 20 minutes.
* Visit 3, about one month after the treatment. The extra measurements take about 30 to 45 minutes.

At each visit the study team checks how well you can see, measures the strength of glasses that gives you the sharpest vision, examines your eye with a slit lamp, measures the pressure inside your eye, and takes images with the imaging devices. All of these are standard eye examinations used in everyday clinical practice. Nothing is inserted into the eye, and there are no injections, no medicines, and no radiation. Drops to widen the pupil are not needed for the study.

Taking part is voluntary. You can stop at any time, without giving a reason and without any disadvantage for your medical care. Your laser treatment and all routine follow-up visits go ahead either way. There is no payment for taking part, and taking part brings no direct medical benefit. However, the detailed examination may reveal something that would not be noticed during routine follow-up, such as raised eye pressure. If this happens, you will be told and any necessary care will be arranged as part of your normal treatment at no extra cost.

Study data are stored under a study code instead of your name.

Conditions

• Posterior Capsule Opacification
• Pseudophakia
• Refractive Errors

Interventions

PROCEDURE

Nd:YAG laser posterior capsulotomy

Routine Nd:YAG laser posterior capsulotomy performed for visually significant posterior capsule opacification according to the department's standard clinical protocol. Indication, technique, energy settings and capsulotomy size are determined by the treating ophthalmologist and are not modified by the study. Procedural parameters are documented for analysis.

DIAGNOSTIC_TEST

Anterior segment swept-source OCT

Non-contact anterior segment optical coherence tomography providing anterior chamber depth, anterior chamber angle and volume, automated three-dimensional IOL tilt and decentration, corneal tomography, pachymetry and pupil parameters. Primary device for the primary outcome measure.

DIAGNOSTIC_TEST

Swept-source optical biometry

on-contact optical biometry providing anterior chamber depth, keratometry, total keratometry, axial length, central corneal thickness, white-to-white and pupillometry.

DIAGNOSTIC_TEST

Scheimpflug-based anterior segment tomography

Scheimpflug-based anterior segment tomography providing anterior chamber depth, SimK, total corneal refractive power, true net power, posterior keratometry, pachymetry mapping, corneal irregularity indices, chamber angle and volume, and axial length.

DIAGNOSTIC_TEST

Subjective manifest refraction

Autorefraction as starting value followed by subjective manifest refraction with Jackson cross-cylinder refinement, yielding sphere, cylinder, axis and spherical equivalent, plus uncorrected and best-corrected distance visual acuity in logMAR. The refractionist is masked to previous refraction values at the post-capsulotomy visits.

Sponsors & Collaborators

• Vienna Hospital Association

  lead OTHER_GOV

Eligibility

Min Age

18 Years

Max Age

100 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-09-01

Primary Completion

2027-08-31

Completion

2027-08-31

Countries

• Austria

Study Locations