Had LASIK twenty years ago, and now a cataract: why the implant calculation is more delicate, and how it is approached
The first LASIK patients of the 1990s and 2000s are now reaching the age of cataract. Their cornea, reshaped by the laser, can no longer be measured like an ordinary cornea, and the classic implant calculation formulas go wrong, almost always in the same direction. Dedicated methods exist, they have been the subject of meta-analyses, and they now make it possible to approach the accuracy of a cataract operation on a never-operated eye, provided it is known that the eye has been operated on. Here is what changes, what you should bring to the consultation, and what can be expected from the result.
UNDERSTANDING
Why does a laser-treated cornea throw off the calculation?
The calculation of the power of a cataract implant rests on two main measurements: the length of the eye and the curvature of the cornea, called keratometry. Refractive surgery does not change the length of the eye, but it modifies the cornea in a way that the instruments do not anticipate. This is where the error arises.
A LASIK or a PRK for myopia flattens the front surface of the cornea at the centre, over a zone of about six millimetres. Keratometers, for their part, measure the curvature over a ring of three millimetres and assume that the back surface follows the front surface in a fixed ratio, that of a cornea that has never been operated on. After a laser, this ratio is no longer true: the front surface has been flattened, the back surface has not. The instrument therefore overestimates the power of the cornea.
An error that almost always goes in the same direction
If the cornea is measured as too powerful, the formula assigns the implant too low a power. The result is postoperative hypermetropia: the patient, who had seen clearly in the distance without glasses since the LASIK, ends up needing them for distance as well as for near. This is the most characteristic refractive surprise of laser-treated eyes, and the leading review on the subject makes it the first cause of dissatisfaction in this population (PMID 27423631).
The second trap lies in the formulas themselves. To predict where the implant will sit in the eye, most of them use the curvature of the cornea as a clue: a flat cornea suggests a “flat” eye, and therefore an implant positioned further forward. After a myopic laser, the cornea is flat because it has been sculpted, not because the eye is small; the formula is wrong a second time. After a laser for hypermetropia, the cornea has been steepened at the centre and the error reverses, towards residual myopia.
The third trap is more discreet: an operated cornea is often less regular, with optical aberrations that do not exist in a never-operated eye. They do not distort the calculation, but they influence the choice of type of implant, in particular tolerance of a multifocal implant.
Why the operated cornea throws off the calculation
Instruments measure the front surface of the cornea and assume the back surface follows it. After a laser for myopia, this is no longer true.
Never-operated cornea
The two surfaces keep the same ratio. The formula knows it and calculates correctly.
Cornea after LASIK for myopia
The front surface is flatter, the back surface is not. The instrument measures a cornea that is too powerful.
Cornea measured as too powerful
The classic measurement sees only the front surface and applies a ratio that is no longer true.
Implant calculated too weak
An ordinary formula compensates for a corneal power that does not exist.
Hypermetropia after the operation
The patient, clear in the distance since the laser, needs glasses again. Dedicated formulas avoid this trap.
Teaching diagram, proportions exaggerated for legibility. Telling the surgeon that the eye was operated on with a laser triggers the use of suitable formulas.
THE METHODS
How the calculation is corrected today
The first generation of methods required the complete history: the refraction before the laser, the refraction obtained afterwards, the measurements of the original cornea. This is the “clinical history method”, long considered the reference. It has a major flaw: twenty years later, this record no longer exists, or is no longer reliable, because the refraction has changed with age and with the onset of the cataract. A 2016 meta-analysis showed, moreover, that history-based methods predicted less well than methods without history (PMID 26948792).
The “no-history” formulas
The Haigis-L formula, published in 2008, was the first designed to do without the old records: it corrects the keratometry measured by the biometer using a curve established on 187 operated eyes, and predicted the refraction to within ±0.50 dioptre in 61% of cases and within ±1 dioptre in 84% (PMID 18812114). It opened the way to the current formulas.
The Barrett True-K formula, in its “no-history” version, is today the most studied. On 88 eyes operated on with LASIK or PRK, it gave a lower median error than the other methods of the calculator of the American cataract surgery society, and a higher proportion of eyes within ±0.50 dioptre (PMID 27006324). A network meta-analysis published in 2024 in the American Journal of Ophthalmology, covering 24 studies and 1,172 eyes, ranks it among the three most accurate methods, with the OCT formula and the Masket formula, ahead of the Haigis-L (PMID 37865389).
The practical advantage is that it is built into modern biometers. A Cleveland Clinic study of 143 eyes showed that the calculation performed directly in the biometer with Barrett True-K did as well as an approach combining several formulas on the online calculator, with a mean absolute error of 0.36 dioptre after myopic LASIK and 0.41 dioptre after hypermetropic LASIK (PMID 35067661). A Chinese study of 78 eyes confirms that the recent formulas, EVO and Barrett True-K in the lead, perform equally well when their dedicated versions are used (PMID 38848053).
Measuring the back surface of the cornea
Scanning biometers, such as the IOLMaster 700 used at the Cachan practice, now measure the back surface of the cornea and calculate a “total keratometry”, which no longer assumes the fixed ratio between the two surfaces. On 129 eyes with a previously operated cornea, this measurement combined with the Haigis formula brought the mean absolute error down to 0.50 dioptre after myopic LASIK, against 0.72 with classic keratometry (PMID 31399324). The Shammas formula, updated in 2024 on 495 eyes, reaches 66.7% of eyes within ±0.50 dioptre, level with the no-history Barrett True-K (PMID 39313859).
A final approach measures the refraction of the eye during the operation, once the lens has been removed, in order to adjust the power of the implant in real time. On 1,067 eyes operated on in 177 American centres, this intraoperative aberrometry did slightly better than Barrett True-K (PMID 39720186). It remains little available in France, and is not used at the practice.
How the calculation has progressed
Four generations of methods, from oldest to newest. The newest no longer need the laser record.
Clinical history
It required the refraction before the laser and the correction performed. Twenty years later, this record is often missing.
Haigis-L, the first without a record
Published in 2008, it corrects the corneal measurement using a curve established on operated eyes.
Barrett True-K, built into the biometer
Among the most accurate methods in a 2024 meta-analysis, with or without the old record.
Total keratometry
The biometer also measures the back surface of the cornea and no longer assumes a fixed ratio between the two surfaces.
At the Cachan practice, the calculation combines several dedicated formulas on the IOLMaster 700; their results are compared before the implant is chosen.
IN CONSULTATION
What you should bring, and what the assessment looks for
The most useful piece of information comes down to one sentence to say from the very first consultation: “I have had laser surgery on my eyes”. An old laser treatment is not always visible at examination, especially after a PRK, and a flattened cornea can pass for a naturally flat cornea. A surgeon who is unaware of it will use an ordinary formula, with the error described above. This information alone triggers the use of dedicated formulas.
Many patients do not think of mentioning it, precisely because the laser worked: twenty years without glasses erase the memory of an operation. Others had it abroad, or with a technique whose name they have forgotten. It does not matter: LASIK, PRK, LASEK or radial keratotomy, each leaves its own signature on the cornea, and each calls for an appropriate calculation method.
The old record remains useful when it exists: the refraction before the laser and the correction performed make it possible to use the “with history” versions of the formulas, and to cross-check the results. A study of 36 eyes that received a multifocal implant after LASIK shows that, when the old data are available, all the formulas perform equally well but one; without these data, the no-history Barrett True-K gave the lowest median error, 0.33 dioptre (PMID 30633788). A partial record is better than none, but its absence is no longer an obstacle.
What you bring to the assessment
A single piece of information changes the calculation method. The rest refines it.
Without an old record, the calculation is still possible: recent formulas do without it.
The assessment at Cachan
The preoperative cataract assessment includes, for these eyes, biometry on the IOLMaster 700 with total keratometry, and corneal topography, which maps the treated zone, its centring and its regularity. Topography also tells whether the optical zone is wide and well centred, which determines the choice of an extended depth-of-focus implant, or whether the cornea is too irregular for that. These two examinations are carried out at the Cachan practice or at the Cabinet ophtalmologique Sorbonne Saint-Michel (Paris 5th), not at the Paris 13 practice.
The calculation is then performed with several dedicated formulas, the results of which are compared. When they converge, confidence is good. When they diverge, the surgeon chooses in full knowledge of the facts, often by aiming for slight myopia rather than strict emmetropia, because a small amount of myopia is better tolerated than hypermetropia.
The rest of the pathway does not change: the operation takes place at the Clinique Sainte-Geneviève, in the 14th arrondissement of Paris, after an anaesthesia consultation, with checks at day 2, at one month and at one year. The definitive glasses, if any are needed, are prescribed at the one-month check, or three to four weeks after the second eye.
THE RESULT
What accuracy to expect, and which implant to choose
It must be said clearly: even with the most accurate methods, accuracy remains slightly lower than for a never-operated eye. Across all cataract operations, the European registry reports 72.7% of eyes within ±0.50 dioptre of the target (PMID 29685779). After myopic LASIK, the most accurate series come close to 65 to 67% (PMID 39313859), and studies on multifocal implants after laser report 47 to 62% depending on the series (PMID 32680481, PMID 29685778). The gap has narrowed considerably over fifteen years, but it has not disappeared.
Accuracy that approaches the average of all operated patients
Share of eyes that end up within 0.50 dioptre of the intended correction, according to published series.
All cataract surgery patients72.7%
After LASIK for myopia65 to 67%
Multifocal implant after laser47 to 62%
The lighter part of a bar shows the range between series. All operated patients: European registry EUREQUO.
This is why the patient who has had laser surgery should know, before the cataract operation, that a supplementary correction remains possible: glasses, or a laser touch-up on the cornea, performed at the Clinique Laser Victor Hugo once the refraction has stabilised. In the Dutch series of 77 eyes with a multifocal implant after myopic LASIK, 20.8% of eyes had a laser touch-up for a residual refraction (PMID 28823437); after hypermetropic LASIK, 22.5% (PMID 29685778).
Multifocal, EDOF or monofocal?
The patient who has had LASIK is, almost by definition, someone who does not like glasses. The temptation of a multifocal implant is therefore strong, and it is sometimes reasonable: the Dutch series cited above obtained a mean uncorrected visual acuity close to 20/30 after multifocal implants in former myopes, with a less predictable result beyond six dioptres of initial myopia (PMID 28823437). A Chinese series of 21 eyes with a trifocal implant finds 90.5% of eyes within ±1 dioptre and good satisfaction (PMID 32680481).
But the operated cornea imposes a reservation. A review published in 2026 stresses that simultaneous-vision implants are more sensitive to the residual aberrations of a remodelled cornea, and that predictability remains lower after hypermetropic laser (PMID 42632564). A 2025 review recommends choosing the implant according to the aberration profile of the cornea, measured at topography, and regards extended depth-of-focus implants, and the “plus” monofocal implant, as more tolerant options than a diffractive multifocal (PMID 40752793).
One point reassures those who have had laser surgery in the past: the laser has done nothing to the eye that makes the cataract operation itself riskier. The cornea is thinner, but the cataract incision is made at the periphery, outside the treated zone, and the work inside the eye is the same. What changes is decided beforehand, in the calculation, and afterwards, in any adjustment.
Frequently asked questions
I had LASIK: should I say so before a cataract operation?
Yes, it is the piece of information that weighs most on the result. An old laser is not always visible at examination, and without this information, an ordinary formula calculates an implant that is too low in power, which leaves hypermetropia (PMID 27423631).
My LASIK record has disappeared. Is that serious?
No. Current formulas, such as the no-history Barrett True-K or the Shammas formula, do without the old record and are among the most accurate in recent studies (PMID 37865389, PMID 39313859). A record remains useful for cross-checking results, but its absence is no longer an obstacle.
What accuracy can be expected?
A little less than for a never-operated eye: the most accurate series report 65 to 67% of eyes within ±0.50 dioptre of the target after myopic LASIK, against 72.7% in the European registry on unoperated eyes (PMID 39313859, PMID 29685779). A touch-up or glasses remain possible.
Can one have a multifocal implant after LASIK?
It is possible on a regular cornea, with a wide, centred treated zone, and it has been studied. The result is less predictable than elsewhere, with a laser touch-up in about one eye in five in the published series (PMID 28823437). An extended depth-of-focus implant is often more tolerant.
And after a PRK rather than a LASIK?
The calculation problem is the same: the cornea has been flattened at the surface, and the same dedicated formulas apply. The studies, in fact, group LASIK and PRK together (PMID 27006324). After radial keratotomy, which is older, the difficulty is greater and the follow-up longer.
Does an old laser make cataract surgery riskier?
No. The incision is made at the periphery of the cornea, outside the treated zone, and the work inside the eye is identical. The difficulty lies in calculating the implant before the operation, not in the operation itself.
If the result is not good, what can be done?
Once the refraction has stabilised, a laser touch-up on the cornea, at the Clinique Laser Victor Hugo, corrects a residual gap; glasses remain the simplest option for a small gap. A 2025 review places corneal correction as first-line in this case (PMID 40929562).
Consultations in Cachan, Paris 13 and at the Sorbonne Saint-Michel practice (Paris 5th) · Tel. +33 1 45 47 08 11
Scientific sources
- Alio JL, et al. Cataract surgery on the previous corneal refractive surgery patient. Surv Ophthalmol. 2016. PMID 27423631
- Pan X, et al. Intraocular lens power calculation in eyes after myopic laser refractive surgery and radial keratotomy: Bayesian network meta-analysis. Am J Ophthalmol. 2024. PMID 37865389
- Chen X, et al. Metaanalysis of intraocular lens power calculation after laser refractive surgery in myopic eyes. J Cataract Refract Surg. 2016. PMID 26948792
- Haigis W. Intraocular lens calculation after refractive surgery for myopia: Haigis-L formula. J Cataract Refract Surg. 2008. PMID 18812114
- Abulafia A, et al. Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia. J Cataract Refract Surg. 2016. PMID 27006324
- Ferguson TJ, et al. IOL power calculations after LASIK or PRK: Barrett True-K biometer-only calculation strategy yields equivalent outcomes as a multiple formula approach. J Cataract Refract Surg. 2022. PMID 35067661
- Rong X, et al. Accuracy of 12 intraocular lens power formulas after corneal myopic refractive surgery. J Refract Surg. 2024. PMID 38848053
- Wang L, et al. Evaluation of total keratometry and its accuracy for intraocular lens power calculation in eyes after corneal refractive surgery. J Cataract Refract Surg. 2019. PMID 31399324
- Shammas HJ, et al. Updating the no-history method in intraocular lens power calculation after myopic laser vision correction. J Cataract Refract Surg. 2024. PMID 39313859
- Fram NR, et al. Refractive prediction accuracy using intraoperative aberrometry versus Barrett True-K formula following corneal refractive surgery. Clin Ophthalmol. 2024. PMID 39720186
- Vrijman V, et al. Evaluation of different IOL calculation formulas of the ASCRS calculator in eyes after corneal refractive laser surgery for myopia with multifocal IOL implantation. J Refract Surg. 2019. PMID 30633788
- Vrijman V, et al. Multifocal intraocular lens implantation after previous corneal refractive laser surgery for myopia. J Cataract Refract Surg. 2017. PMID 28823437
- Vrijman V, et al. Multifocal intraocular lens implantation after previous hyperopic corneal refractive laser surgery. J Cataract Refract Surg. 2018. PMID 29685778
- Li QM, et al. Trifocal diffractive intraocular lens implantation in patients after previous corneal refractive laser surgery for myopia. BMC Ophthalmol. 2020. PMID 32680481
- Susanna BN, et al. Cataract surgery following refractive surgery: principles for success. Asia Pac J Ophthalmol. 2025. PMID 40752793
- Rodriguez-Calvo-de-Mora M, et al. Management of presbyopic patients with previous corneal refractive surgery: phenotype-driven considerations and functional classification. Arch Soc Esp Oftalmol. 2026. PMID 42632564
- Lundström M, et al. Risk factors for refractive error after cataract surgery: analysis of 282 811 cataract extractions reported to the European Registry of Quality Outcomes for cataract and refractive surgery. J Cataract Refract Surg. 2018. PMID 29685779
- Kanclerz P, et al. Surgical options for correcting refractive surprise after cataract and lens surgery: review and meta-analysis. J Cataract Refract Surg. 2025. PMID 40929562
Further reading
- Cataract surgery: how it goes and choosing the implant
- The preoperative cataract assessment
- Corneal topography
- LASIK: principle and procedure
This article is intended for information only and does not replace a medical consultation. Indications, expected benefits and risks depend on each individual situation. For any question about your vision, consult an ophthalmologist.
Written and reviewed by Dr Moïse Tourabaly, ophthalmic refractive surgeon — former chef de clinique (Quinze-Vingts National Eye Hospital).
Last updated: October 4, 2026
