|Year : 2022 | Volume
| Issue : 2 | Page : 365-368
Management of refractive surprise after phacoemulsification due to a decentered laser-assisted in situ keratomileusis zone: Intraocular lens power calculation using aphakic refraction methods
Samrat Chatterjee, Deepshikha Agrawal
Cornea and Anterior Segment Services, MGM Eye Institute, Raipur, Chhattisgarh, India
|Date of Submission||28-Nov-2021|
|Date of Acceptance||31-Jan-2022|
|Date of Web Publication||13-Apr-2022|
MGM Eye Institute, 5th Mile, Vidhan Sabha Road, Raipur - 493111, Chhattisgarh
Source of Support: None, Conflict of Interest: None
A 39-year-old male with prior history of having undergone laser-assisted in situ keratomileusis (LASIK) in both eyes was referred for management of refractive surprise of +5.0 diopter following phacoemulsification with intraocular lens (IOL) implantation in the left eye. The IOL power was re-calculated using post-LASIK IOL power formulae, but it did not differ significantly from that of the implanted IOL. Topography in the left eye showed decentration of the laser ablation zone and mild ectasia. An IOL exchange was performed in the following steps: IOL extraction, postoperative aphakic refraction to calculate IOL power, and IOL implantation. Postoperatively, there was no refractive surprise. In the right eye, the IOL power was calculated using post-LASIK IOL power formulae, which did not result in postoperative refractive surprise. Our experience highlights the efficiency of aphakic refraction over post-LASIK IOL power formulae in predicting IOL power in eyes with decentered laser ablations.
Keywords: Aphakic refraction method, intra-ocular lens power calculation, laser in situ keratomileusis, post-LASIK intra-ocular lens power formulae, refractive surprise
|How to cite this article:|
Chatterjee S, Agrawal D. Management of refractive surprise after phacoemulsification due to a decentered laser-assisted in situ keratomileusis zone: Intraocular lens power calculation using aphakic refraction methods. Indian J Ophthalmol Case Rep 2022;2:365-8
|How to cite this URL:|
Chatterjee S, Agrawal D. Management of refractive surprise after phacoemulsification due to a decentered laser-assisted in situ keratomileusis zone: Intraocular lens power calculation using aphakic refraction methods. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2022 May 18];2:365-8. Available from: https://www.ijoreports.in/text.asp?2022/2/2/365/342989
Previous cornea-based laser vision correction surgery like laser-assisted in situ keratomileusis (LASIK) is an important risk factor for refractive surprises after cataract surgery. Although over the years there have been many refinements in intraocular lens (IOL) power calculation in eyes with prior LASIK surgery, errors related to index of refraction and measurement of corneal radius, and inherent errors within the IOL formulae continue to challenge ophthalmologists even today.,, In this report, we describe our experience of managing refractive surprise after phacoemulsification in a patient with prior LASIK by using the aphakic refraction method because the routine post-LASIK IOL power formulae were found to be inadequate in predicting the correct power of the IOL.
| Case Report|| |
A 39-year-old male businessman who had undergone LASIK in both eyes in 2011 was diagnosed with cataract in both eyes in November 2019 by his ophthalmologist. He underwent an uneventful phacoemulsification in the left eye elsewhere, and a + 12.0 diopter (D) acrylic IOL was implanted. Postoperatively, there was a refractive error of +5.0 D in the operated eye and he was referred to our institute for further management.
On examination, his uncorrected visual acuity in both eyes was 20/300 [Table 1], while the best spectacle-corrected visual acuity in the operated left eye was 20/20, N6 (with +5.00 D sphere, add +3.00 D). A comprehensive examination of the anterior and posterior segments was unremarkable but for the presence of corneal scars consistent with a LASIK flap in both eyes, 3+ nuclear sclerosis in the right eye, and an in-the-bag acrylic IOL in the left eye. A diagnosis of axial myopia and status post LASIK in both eyes, nuclear cataract in the right eye, and pseudophakia with under-correction (refractive surprise) in the left eye was made.
|Table 1: Visual acuity, refraction, and intraocular lens power calculation in both the eyes at presentation|
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IOL power was re-calculated using the post-LASIK IOL power formulae available in an online IOL calculator, and the mean IOL power to achieve post-operative emmetropia was +12.90 D (range: 11.38D to 16.46D), which did not differ from the power of the IOL that was already implanted. Axial curvature maps on corneal topography showed flattening of the central cornea in both the eyes consistent with a laser ablation zone [Figure 1]. The laser ablation zone was well-centered in the right eye but grossly decentered in the left eye with a suspicious area of ectasia. The patient was advised IOL exchange, and it was decided to use the aphakic refraction method,,,, for calculation of IOL power as the power obtained from the various post-LASIK IOL power formulae did not differ greatly from the power of the implanted IOL, nor account for the +5.0 D of under-correction. The patient underwent an uneventful IOL explantation. On the first postoperative day, refraction was performed, and the mean power obtained by the different aphakic refraction methods [see [Box 1]] was +17.86 D [Table 2]. The next day, an acrylic foldable IOL of +18.0 D was implanted. The postoperative course was uneventful, and at one month, his best spectacle-corrected visual acuity was 20/20, n6 [Table 2]. The explanted IOL was shared with the manufacturing company and they confirmed the power to be +12.0 D, same as that printed on the label.
|Figure 1: Placido-based corneal topography (a and b) and corneal tomography of the Pentacam scheimpflug system (c to f) of the patient. The right eye (a-e) shows central corneal flattening but absence of any decentration of the laser ablation zone, or ectasia. The left eye (b-f) shows large decentration of the laser ablation zone, localized elevation in the anterior-enhanced elevation map but no overall ectasia|
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|Table 2: Calculation of intraocular lens power calculation based on aphakic refraction and postoperative outcome in the left eye|
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Due to the COVID-19 pandemic, the patient was lost to review. He was examined again in September 2021. His refraction in the left eye was stable [Table 2]. He underwent an uneventful phacoemulsification in the right eye, and an IOL was implanted in the same sitting, the power of which was calculated using different post-LASIK IOL power formulae [Table 3]. The postoperative period was uneventful with no refractive surprise [Table 3].
|Table 3: Visual acuity, calculation of intraocular lens power, and postoperative outcome in the right eye|
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| Discussion|| |
In the right eye of our patient in which the LASIK ablation zone was well-centered, the post-LASIK IOL power calculation formulae correctly predicted the IOL power, but in the left eye, with a large decentration of the ablation zone, these same formulae were found to be erroneous and ineffective. Instead, the aphakic refraction method was found to be successful in predicting the correct IOL power.
Aphakic refraction methods,,,, are purely refractive methods of IOL power calculation that do not require a measurement of the corneal curvature, axial length, or IOL position, thereby circumventing the errors that occur with the standard IOL power calculation methods. This method has been reported to be effective in eyes with high myopia, previous refractive surgery, corneal scars, large irregular astigmatism, posterior staphyloma, and a silicone oil-filled vitreous cavity.,,, Our successful use of this technique in an eye with a decentered LASIK ablation zone adds to the above indications.
Mackool et al., suggested the “extraction-aphakic refraction-implantation technique.” While these authors performed cataract extraction, aphakic refraction, and IOL re-implantation on the same day, we spread the procedures over a few days. We felt that refraction in the out-patient department immediately after the IOL explantation would not only be uncomfortable for the patient, but also carry risk of infection. Other investigators,, have reported performing intraoperative refraction after cataract extraction with handheld autorefractors. While this approach avoids returning to the operating theater for the second time, intraoperative refraction has certain challenges like variability in the refractive index of the balanced salt solution and viscoelastic devices, and achieving correct alignment between the pupil and the autorefractor, all of which may affect the IOL power calculation. Also, handheld autorefractors may not be available with all, and intraoperative manual retinoscopy or autorefraction risks the sterility of the operative field. As all the aphakic refraction formulae,,, differ in the assumption of the vertex distance of refraction and the A-constants (Box), we chose to use the average of the powers obtained by different formulae. Retrospectively, this appeared to be a sound strategy as relying on a single formula would have resulted in either under- or over-correction by at least 1 D.
| Conclusion|| |
Based on our experience, we would suggest that all patients with a prior history of cornea-based laser vision correction undergo corneal topography to rule out decentration of the laser-ablation zone or ectasia. If these are present, aphakic refraction method may be a better alternative to calculate the power of the IOL than the standard formulae for post-LASIK IOL power.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]