Eye examination

Ocular aberrometry: measuring the eye’s optical aberrations

You see well in the distance with your glasses, yet you notice halos, glare or a loss of sharpness at night? Ocular aberrometry is the examination that answers this question. By analysing every optical imperfection of your eye — not just ordinary myopia or astigmatism — it makes it possible to personalise laser treatment and to explain certain visual complaints that a standard refraction cannot capture. Here is what this examination measures, what it is for and how it is performed.

Direct answer: a complete optical assessment of the eye

In brief. Aberrometry measures the full range of the eye’s optical aberrations, whether low-order (myopia, hyperopia, astigmatism) or higher-order (spherical aberration, coma, trefoil). Depending on the technique, it relies either on mapping the cornea (corneal aberrometry, performed in the office with the Sirius+ topographer) or on analysing a beam of light passing through the entire eye (ocular wavefront aberrometry). The examination, quick and non-contact, serves mainly two purposes: to personalise laser treatment (wavefront-guided surgery) and to explain visual complaints such as halos or night-time glare. It is not painful and requires no special preparation.

What are optical aberrations?

An optically perfect eye would focus all light rays onto a single precise point on the retina. In reality, no eye reaches this perfection: optical imperfections, called aberrations, slightly scatter the rays and degrade the quality of the perceived image.

Two categories are distinguished:

Low-order aberrations: these are myopia, hyperopia and regular astigmatism. They account for the greater part of the visual error and are corrected by glasses, contact lenses or conventional refractive surgery.
Higher-order aberrations: these are more subtle — spherical aberration, coma, trefoil, tetrafoil… They alter standard visual acuity measured on a letter chart little or not at all, but they degrade visual quality in demanding conditions: low light, night driving, contrast vision. They are often responsible for the halos and glare that some patients describe even with optimal optical correction.

What is aberrometry used for?

Ocular aberrometry is useful in several clinical situations:

Personalising laser treatment (wavefront-guided): conventional refractive surgery corrects myopia, hyperopia and astigmatism. Wavefront-guided surgery goes further: it incorporates the map of higher-order aberrations to reshape the cornea in a personalised way. The goal is to reduce these aberrations along with the main refractive error, in order to improve the quality of night vision. To learn more, see our LASIK and pre-operative assessment pages.
Understanding a night-time visual complaint: a patient who reports halos and glare at night despite satisfactory visual acuity may have elevated higher-order aberrations. Aberrometry documents them objectively and allows a concrete discussion with the patient.
Evaluation before and after refractive surgery: comparing aberrations before and after the procedure provides information about the quality of the optical outcome beyond visual acuity alone. It can also help identify an iatrogenic cause of a post-operative complaint.
Monitoring an irregular cornea: in cases of keratoconus or irregular corneal astigmatism, aberrometry quantifies the degradation of optical quality and helps guide the treatment decision (cross-linking, scleral lens, surgery).

How is the examination performed?

Aberrometry is carried out in the office, as part of the pre-operative assessment or a dedicated consultation. It is straightforward:

Positioning: you rest your chin on the chin rest of the Sirius+ topographer and fixate on a light point. No contact with the eye, no anaesthetic drops.
Acquisition: the device projects luminous rings (Placido disc) and captures, with a Scheimpflug camera, the precise shape of both surfaces of the cornea. From this map, the software calculates the optical aberrations induced by the cornea. Acquisition takes a few seconds per eye, without contact.
Analysis: the software breaks the aberrations down into Zernike polynomials. Each term corresponds to a type of aberration. The total RMS (root mean square) of the higher-order aberrations summarises the overall level of optical degradation.

The examination is quick and causes no discomfort. If you wear contact lenses, it is best to remove them at least 30 minutes before the examination so as not to disturb the associated corneal surface measurements.

Corneal aberrometry and total ocular aberrometry

There are two complementary approaches. Corneal aberrometry, performed in the office using the Sirius+ topographer, measures the aberrations induced by the cornea alone. Total ocular aberrometry, obtained with a Hartmann-Shack type wavefront aberrometer, measures the aberrations of the whole eye, including cornea and crystalline lens; it is used in particular when planning a personalised laser treatment.

These two measurements complement each other: corneal aberrometry, combined with topography, helps to understand the cornea’s share in a visual complaint, while total aberrometry reflects the final optical outcome perceived by the eye.

From measurement to personalised treatment

The aberration map obtained from aberrometry has more than explanatory value: it can also be used to personalise a laser treatment. Wavefront-guided surgery (wavefront-guided) incorporates this map into the ablation profile, so as to correct the aberrations specific to your eye in addition to the main refractive error. This is one of the three main approaches to tailored LASIK, alongside the optimised profile and topography-guided treatment.

The details of these methods, their indications and how the choice is made in the office are covered in our dedicated article: Personalised LASIK: wavefront, topography or optimised profile. For patients wondering about the safety of the procedure, see also our page on the safety of refractive surgery.

FAQ

Frequently asked questions

Is aberrometry painful?

No, it is an entirely non-contact examination of the eye. The light beam used is of very low power and causes no unpleasant sensation. The examination is finished within a few seconds per eye.

What is the difference between aberrometry and standard refraction?

Standard refraction measures the main error of the eye — myopia, hyperopia, astigmatism — to determine the correction for glasses or contact lenses. Aberrometry measures the full range of the eye’s optical imperfections, including the higher-order aberrations that degrade visual quality in demanding conditions without being captured by a standard refractive assessment. The two examinations are complementary.

Are all laser treatments wavefront-guided?

No. There are several laser treatment profiles: conventional treatments based on refraction alone, wavefront-optimized treatments that account for the shape of the cornea in a generic way, and wavefront-guided treatments that incorporate the patient’s individual aberrometry map. The choice of profile depends on the clinical indication and the results of the pre-operative examinations.

Can aberrometry explain my night-time halos?

Yes, this is one of its main clinical uses. A high level of spherical aberration or coma can be responsible for halos and glare at night despite satisfactory visual acuity. Aberrometry documents and quantifies this complaint objectively. To learn more, see our article on halos and glare at night after refractive surgery.

Does the pupil need to be dilated for aberrometry?

In most cases, the examination is performed without dilation for a measurement under natural conditions. In certain indications — a suspicious large pupil at night, in-depth analysis — a measurement under dilation may be carried out in addition. Your ophthalmologist will determine the protocol suited to your situation.

Scientific sources

Applegate RA, Sarver EJ, Khemsara V. Are all aberrations equal? J Refract Surg. 2002;18(5):S556-S562. PMID: 12361157
Marsack JD, Thibos LN, Applegate RA. Metrics of optical quality derived from wave aberrations predict visual performance. J Vis. 2004;4(4):322-328. PMID: 15134479
Wan KH, Liao XL, Yu M, Tsui RWY. Wavefront aberrometry repeatability and agreement — a comparison between Pentacam AXL Wave, iTrace and OPD-Scan III. Ophthalmic Physiol Opt. 2022;42(6):1326-1337. PMID: 36102169
French Society of Ophthalmology (SFO). Report on imaging and wavefront analysis in refractive surgery.

Having an ocular aberrometry examination

If you would like a complete optical assessment — before refractive surgery, to understand a night-time visual complaint, or to evaluate the quality of your vision — book an appointment with Dr Moïse Tourabaly. Aberrometry is performed during a consultation at the Cachan practice, as part of a pre-operative assessment or a dedicated consultation.

This article is intended for information and educational purposes. It is not a substitute for a medical consultation. The indication and interpretation of an aberrometry are the responsibility of your ophthalmologist. Sources: articles indexed on PubMed; recommendations of the French Society of Ophthalmology (SFO).