Hyperopic shift after refractive lens surgery in a patient with prior history of radial keratotomy

Julio C Hernandez-Camarena; Raul E Ruiz-Lozano; Brandon Rodriguez-Pinzon; Jorge E Valdez-Garcia

doi:10.4103/pajo.pajo_23_22

CASE REPORT

Year : 2022 | Volume : 4 | Issue : 1 | Page : 39

Hyperopic shift after refractive lens surgery in a patient with prior history of radial keratotomy

Julio C Hernandez-Camarena, Raul E Ruiz-Lozano, Brandon Rodriguez-Pinzon, Jorge E Valdez-Garcia
Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Mexico

Date of Submission	29-Mar-2022
Date of Decision	09-Jun-2022
Date of Acceptance	20-Jun-2022
Date of Web Publication	30-Jul-2022

Correspondence Address:
Julio C Hernandez-Camarena
Instituto de Oftalmologia y Ciencias Visuales, Centro Medico Zambrano Hellion, Av. Batallon de San Patricio No. 112. Col. Real de San Agustín, N.L. CP. 66278, Monterrey
Mexico

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/pajo.pajo_23_22

Abstract

Radial keratotomy (RK) was a popular refractive procedure in the 90s. However, more reproducible laser-assisted surgeries are currently preferred. Furthermore, RK patients who undergo cataract surgery experience variable refractive and keratometric changes during the early postoperatory period. Unfortunately, those post-RK patients currently require cataract surgery. A 58-year-old male with a history of RK in both eyes (OU) presented with a 2-year history of night glare and progressive vision loss due to a subcapsular cataract in OU. Using the double-K Holladay formula, bilateral phacoemulsification was performed. At 1 week, refraction was + 2.25/-1.00/27° (power [Pwr]: 39.25D) in oculus dextrus (OD) and + 3.00/−0.75/171° in oculus sinister (OS) (Pwr: 37.41D), achieving a best-corrected visual acuity (BCVA) of 20/30 OU. At 6 weeks, refraction was + 0.75/−0.75/18° (Pwr: 39.71D) in OD and + 1.00/−0.25/180° (Pwr: 38.33) in OS. BCVA remained 20/30 OU. The resulting transitory hyperopic shift after surgery demands a careful and comprehensive intraocular lens calculation preferably aiming toward myopic overcorrection.

Keywords: Cataract surgery, hyperopic shift, radial keratotomy, refractive lens surgery

How to cite this article:
Hernandez-Camarena JC, Ruiz-Lozano RE, Rodriguez-Pinzon B, Valdez-Garcia JE. Hyperopic shift after refractive lens surgery in a patient with prior history of radial keratotomy. Pan Am J Ophthalmol 2022;4:39

How to cite this URL:
Hernandez-Camarena JC, Ruiz-Lozano RE, Rodriguez-Pinzon B, Valdez-Garcia JE. Hyperopic shift after refractive lens surgery in a patient with prior history of radial keratotomy. Pan Am J Ophthalmol [serial online] 2022 [cited 2023 Mar 28];4:39. Available from: https://www.thepajo.org/text.asp?2022/4/1/39/353004

Introduction

Radial keratotomy (RK) consists of a procedure in which deep corneal incisions are made in a radial spoke-wheel pattern. These cuts result in a peripheral elevation, leading to a central corneal flattening. Unfortunately, the extent of flattening and the stability of the new curvature are mostly unpredictable.^[1] The development of new refractive laser-assisted procedures gradually phased out RK. However, the postoperative complications of RK suggest a complex and often controversial scenario for the corneal surgeon who intends to reoperate them.^[2] One of the main challenges is achieving precise refractive outcomes after intraocular lens (IOL) implantation, since the accuracy that current formulas grant for patients with nonoperated eyes is jeopardized in those who have undergone refractive surgery, especially RK.^[1]

Case Report

A 58-year-old male with a 20-year history of RK in both eyes (OU) came for evaluation referring a 2-year history of vision loss and night glare OU. Uncorrected visual acuity (UCVA) was 20/400 in the right oculus dextrus (OD) and left oculus sinister (OS) eye. Initial refraction was -3.25/-1.25/20° OD and -3.25/-2.00/130° OS, achieving a best-corrected visual acuity (BCVA) of 20/50 and 20/80. Slit-lamp examination shows ten corneal radial incisions of an approximate depth of 90%, an optical zone of 3.5 mm, and a posterior subcapsular cataract in OU [Figure 1]. The rest of the exploration was normal.

Corneal topography based on placid disk (Orbscan IIz, Bausch and Lomb, Rochester, NY, USA) was performed OU. A central 7-mm corneal flattening was observed in the axial curvature map in OU. The average keratometry was OD 40.9D and OS 37.4D, and the central pachymetry was 558 μm OD and 564 μm OS [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d. Keratometries were also measured using Pentacam HR (Oculus Optikgeräte GmbH, Wetzalar, Germany) and outpatient department (OPD) Scan-III (NIDEK CO., LTD. Gamagori, Japan) [Figure 3]a and [Figure 3]b. SimK for OD was 38.79/39.99 at 29° (topographic astigmatism of 1.2D) and 37.50/39.11 at 124° (topographic astigmatism of 1.61D) for OS.

Figure 1: (a) Slit-lamp examination of patient × s right eye showing prior radial keratotomies. (b) Posterior slit-lamp examination of patient × s right eye showing subcapsular cataract. (c) Slit-lamp examination of patient × s left eye showing prior radial keratotomy. (d) Posterior slit-lamp examination of patient × s left eye showing subcapsular cataract

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Figure 2: (a and b) Corneal axial and pachymetric maps of the right eye. (c and d) Corneal axial and pachymetric maps of the left eye

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After the assessment, cataract phacoemulsification and IOL placement were performed OU. To calculate the IOL power, the average of the calculations obtained from the double-K Holladay formula, optical coherence tomography (OCT)-based formula, and Barrett True-K formula (IOL power calculator from the American Society of Cataract and Refractive Surgery [ASCRS]) were used. Central 1.0, 2.0, 3.0, and 4.0 mm keratometric readings from the Pentacam HR Holladay Report were used. Average lens calculation power of 14.88D for OD and 17.93D for OS were obtained. Thus, a SN60EF (Acrysof IQ Monofocal, Alcon Novartis, Fort Worth, USA) +15.0D in OD and a SN6AT4 (Acrysof IQ Toric, Alcon Novartis, Fort Worth, USA) +18.0D in OS were used.

At 1-week visit, UCVA was 20/40 OD and 20/60 OS. SimK for OD was 38.88/40.37 at 19° (mean power: 39.25D) and 37.67/39.34 at 126° (mean power: 37.41D) for OS [Figure 3]c and [Figure 3]d. Refraction was + 2.25/-1.00/27° in OD and + 3.00/-0.75/171° in OS, achieving a BCVA of 20/30 OU. Slit-lamp examination showed mild edema on the 2.8-mm temporal corneal incisions OU. After 6 weeks, UCVA improved to 20/30 OD and 20/40 OS. Refraction was +0.75/-0.75/18° in OD and +1.00/−0.25/180° in OS, achieving a BCVA of 20/30 on OU. SimK for OD was 39.02/40.04 at 42° (mean power: 39.71D) and 37.21/38.166 at 124° (38.33) for OS [Figure 3]e and [Figure 3]f.

Figure 3: (a and b) Photograph showing preoperative OPD scan-III axial map of patient × s right and left eye, respectively. (c and d) OPD scan-III axial map at postoperative week 1 of the right and left eye, respectively. (e and f) Photograph showing postoperative week 6 OPD Scan-III axial map of right and left eye, respectively. OPD: Outpatient department

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Conclusion

RK is performed using radial incisions of variable depths into the corneal stroma, which produces a wound associated with mid-peripheral bulging of the cornea, compensatory central corneal flattening, and decreased refractive power.^[3] The 10-year follow-up of the Prospective Evaluation of Radial Keratotomy study that included 374 post-RK patients of 10 years of evolution, reported a hyperopic shift in 43% of them, in addition to an important diurnal variation in their refractions.^[2] After RK, a regression is expected in the first postoperative stages due to the healing of the corneal wounds and neovascularization along the radial incisions if the latter is presented.^[2] Diurnal variation, on the other hand, is considered secondary to corneal edema and diurnal fluctuations of intraocular pressure (IOP) and oxygen tension.^[1],[4] Other visual symptoms associated with poor vision quality, such as glare or halos, have been reported after the procedure and are directly related with the size of the optical zone. In addition, an increased corneal tissue vulnerability to trauma is reported owed to a reduction on its biomechanical strength.^[2] In this case, the decrease in vision and the appearance of glare symptoms were correlated with the manifestation of the subcapsular cataract on OU since they had a recent onset (2 years), hence a noncorneal approach was preferred to solve both symptoms and the refractive error.

IOL power calculation errors in eyes with prior refractive surgery occur for three main reasons: instrument error, a change in the corneal refractive index, and formula error.^[5] The ASCRS developed an online calculator that allows comparing different formulas for calculating the IOL in patients with this antecedent, among which the case of post-RK patients is included. For this, the formulas of Double-K Holladay 1, OCT-based, and Barrett True-K are considered a base.^[6] In a study conducted by Abulafia et al., it was found that in patients with previous refractive surgery, the Barrett True-K formula showed a mean absolute refraction prediction error level significantly lower than the other alternative formulas including Masket, Wang-Koch-Maloney, Shammas, and Haigis-L.^[7] In addition to a higher percentage of eyes within the range ± 0.50D of error predicted in refraction compared with the methods of adjusted Atlas, Masket, and Modified Masket. In eyes with no prior historical data, Barrett True-K had a smaller median absolute refraction prediction error and a higher percentage of eyes within <0.50D of the predicted error in refraction than the Shammas and Haigis-L formulas. The authors, therefore, propose the Barret True-K formula as the best alternative for patients with a history of refractive surgery, over the other alternative formulas. In another similar study, Packer et al. proposed a model where the Holladay formula was used to calculate IOL in post-RK patients.^[8] They found that 80% of the eyes undergoing surgery reached a spherical refractive equivalent within ± 0.50 diopter of emmetropia; attributing it to the fact that this formula considers the effective refractive power parameter and concluding that the final refractive result for these patients using the Holladay formula was adequate. Furthermore, Ma et al. tried to compare the three base formulas of the ASCRS calculator for the IOL calculus in patients with prior RK.^[3] They noticed that the OCT-based formula and the True-K formula yielded a hyperopic IOL prediction error 1 month after phacoemulsification surgery. They concluded that, although using the average IOL power prediction of the ASCRS calculator seems like the best option for these patients, no formula was capable to predict 80% of eyes within 1D target refraction at >4 months postoperative.^[3] Nevertheless, they affirm the necessity to develop a more precise formula for calculating IOL in these patients. Recently, the use of intraoperative wavefront aberrometry to predict residual refractive error and accurately calculate IOL power represents a potential tool for the management of challenging cases where the corneal curvature (anterior and/or posterior) and the accuracy of routine biometric IOL calculation is compromised.^[9]

To allow easy access to the incision and the capsular bag, some authors suggest that RK patients with unsatisfactory refractive outcomes after cataract surgery must undergo immediate correction of such errors.^[5] However, this approach is disfavored since patients with previous RK typically experience a hyperopic shift in the following weeks after cataract surgery, as it was observed in the present case.^[1],[10] These changes of refraction can be explained by the same mechanisms as those of the RK itself; transient corneal edema and ongoing corneal flattening are mostly experienced during the first postsurgical weeks. As reported by other authors, we observed an early flattening of the central cornea followed of a consequent central steepening at week 6 postoperative, a phenomenon that could partially explain the observed postoperative hyperopic shift (increase in the mean refractive power) [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]d, [Figure 3]e, [Figure 3]f.^[10] Other theories regarding the transient hyperopic shift in the early postoperative period are related to the leaky epithelial syndrome and the emphasis on the elevation of the IOP that can alter the corneal curvature and therefore the refractive error.^[10] The corneal epithelium plays an important role as a hydrophobic barrier. The surgical intervention suffered by these patients leads to corneal swelling and subsequent edema secondary to a pro-inflammatory state. In addition, this edema is exacerbated by the altered permeability of the post-RK corneal epithelium scars. Once a basal state of inflammation has been reached, the edema and the corneal epithelium permeability decrease, partly explaining the biomechanical and curvature changes in the mid-peripheral and central cornea (hyperopic shift).^[1],[10]

The role of the IOP changes on the corneal refractive status in eyes with RK has also been assessed. Busin et al. assessed the effects of IOP variations on the eyes of 18 post-RK rabbits and observed that changes within a physiological range (10–20 mmHg) were enough to reduce corneal refractive power by 0.50 D.^[4] The authors suggest that fluctuations in IOP may increase the risk of postoperative changes in visual acuity in humans with previous RK. Altogether this evidence points to the fact that diverse mechanisms are implicated in the changing refraction and corneal curvature/biomechanics of these patients, and therefore the necessity of a meticulous follow-up.

In conclusion, RK represented in its time a great advance as far as refractive surgery is concerned. However, like any pioneering technique, it entailed several associated complications that currently must be faced by the cornea and refractive surgery specialists. There is insufficient evidence regarding cataract surgery in post-RK patients, and it is even scarcer in terms of accurate IOL calculation. When analyzing the available evidence, we can conclude that the hyperopic shift is a poorly understood phenomenon frequently observed in this type of patient that should be thoughtfully considered at the time of IOL calculation and during the postoperative follow-up. New technologies, as intraoperative aberrometer, portray a promising tool for a more accurate IOL calculation in complex cases where biometric formulas precision is jeopardized. In such case, when using biometric formulas, having a target toward a myopic overcorrection (approximately −1.00D/−1.25D) at the time of IOL calculation may be advisable, in an attempt to compensate the undergoing hyperopic shift.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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