With the increasing number of multifocal and accommodative intraocular lens (IOL) implantations being carried out, cataract surgery is fast becoming another form of refractive surgery.¹ Furthermore, since the newer multifocal IOLs have reduced functional loss for near, intermediate and distance visual acuity, those patients implanted with these lenses are generally very happy with the results.² It is however, less common for post-LASIK patients to undergo multifocal IOL implantation because it is considered by many to be a complex procedure.

"Some colleagues and I performed a search of available literature and could not find a published paper on multifocal IOL implantations in post-LASIK patients," said Dr Zeki Tunc, Assistant Professor of Ophthalmology at Maltepe University Medical School, Turkey. "Many sources regarded post-LASIK patients as unfit for multifocal IOL implantation," he added.

Believing that this surgical approach could be of benefit in some patients, Dr Tunc performed his first multifocal IOL implantation in a post-LASIK patient.

The case study

The 70-year old female patient received hyperopic LASIK nine years ago (OD: +3.75; OS: +3.50 -0.50 90). Upon formation of cataract, the same surgeon (Dr Tunc) performed bilateral phacoemulsification surgery and implanted two multifocal IOLs. The right eye received a ReZoom (AMO) refractive lens and the left eye, a Tecnis multifocal (AMO) aspheric diffractive lens.

"I believe that both these lenses have good and bad attributes, so I felt the best approach would be to mix and match the two in this case," said Dr Tunc.

The patient's preoperative and two month postoperative values were measured and evaluated using distance, intermediate and near visual acuity (using Snellen and Jaeger charts), topography, keratometric values, and postoperative contrast values (using contrastometer BA-4 and Optec 6500). IOL power calculation was performed using the clinical background method and the patient was also questioned about changes in quality of life, light reflections and general happiness following the implantation.

"IOL power calculation is difficult in post-refractive surgery patients because errors in keratometric evaluation resulting from corneal changes could lead to incorrect biometric calculations. These errors in IOL calculations have been shown to pose problems for both the patient and the surgeon,"^3,4 conceded Dr Tunc.

With regards to the calculation of keratometric values in post-refractive surgery patients, the topographical analysis, clinical background method, contact lens method, refractive and clinical derivation methods, intraoperative autorefraction and IOL power calculation with adjusted vertex distance methods could be used.⁵

"I prefer to use the 'clinical background method' which allows for the calculation of a postoperative K value by deducting the post-refractive spherical equivalent (SE) from the pre-operative K value. In order to achieve this, the following values must be known; preoperative corneal power, preoperative refraction, post-refractive stable refraction (before the formation of cataract). This method is now considered as the gold standard by most."⁵ said Dr Tunc.

Patient independence achieved

At two months, the postoperative uncorrected visual acuity (UCVA) was 0.8 and 1.0 for distance, J5 and J3 for intermediate and J3 and J1 for near vision. The patient's best corrected visual acuity (BCVA) was 1.0 and 1.0 for distance, J2 and J1 for intermediate and J1 and J1 for near visual acuity.

Refraction values were OD -0.75, OS +0.00. Contrast sensitivity measurements were 170 cycles per degree (cpd) without glare, 132 cpd with glare and a re-adaptation time of two seconds. There was also a distinct decrease in contrast sensitivity measurements at four months.

"The patient reported decreasing glare with no need for glasses, and she rated her overall satisfaction as 'good', which is great news," enthused Dr Tunc.