Predictability of Existing IOL Formulas After Cataract Surgery in Patients with a Previous History of Radial Keratotomy: A Retrospective Cohort Study and Literature Review

INTRODUCTION

This study aims to evaluate the accuracy of 12 different intraocular lens (IOL) power calculation formulas for post-radial keratotomy (RK) eyes. The investigation utilizes recent advances in topography/tomography devices and artificial intelligence (AI)-based calculators, comparing the results to those reported in current literature to assess the efficacy and predictability of IOL calculations for this patient group.

METHODS

In this retrospective study, 37 eyes from 24 individuals with a history of RK who underwent cataract surgery at Hoopes Vision Center were analyzed. Biometry and corneal topography measurements were taken preoperatively. Subjective refraction was obtained 6 months postoperatively. Twelve different IOL power calculations were used, including the American Society of Cataract and Refractive Surgery (ASCRS) post-RK online formula, and the Barrett True K, Double K modified-Holladay 1, Haigis-L, Panacea, Camellin-Calossi, Emmetropia Verifying Optical (EVO) 2.0, Kane, and Prediction Enhanced by Artificial Intelligence and output Linearization-Debellemanière, Gatinel, and Saad (PEARL-DGS) formulas. Outcome measures included median absolute error (MedAE), mean absolute error (MAE), arithmetic mean error (AME), and percentage of eyes achieving refractive prediction errors (RPE) within ± 0.50 D, ± 0.75 D, and ± 1 D for each formula. A search of the literature was also performed by two independent reviewers based on relevant formulas.

RESULTS

Overall, the best performing IOL power calculations were the Camellin-Calossi (MedAE = 0.515 D), the ASCRS average (MedAE = 0.535 D), and the EVO (MedAE = 0.545 D) and Kane (MedAE = 0.555 D) AI-based formulas. The EVO and Kane formulas along with the ASCRS calculation performed similarly, with 48.65% of eyes scoring within ± 0.50 D of the target range, while the Equivalent Keratometry Reading (EKR) 65 Holladay formula achieved the greatest percentage of eyes scoring within ± 0.25 D of the target range (35.14%). Additionally, the EVO 2.0 formula achieved 64.86% of eyes scoring within the ± 0.75 D RPE category, while the Kane formula achieved 75.68% of eyes scoring within the ± 1 D RPE category. There was no significant difference in MAE between the established and newer generation formulas (P > 0.05). The Panacea formula consistently underperformed when compared to the ASCRS average and other high-performing formulas (P < 0.05).

CONCLUSION

This study demonstrates the potential of AI-based IOL calculation formulas, such as EVO 2.0 and Kane, for improving the accuracy of IOL power calculation in post-RK eyes undergoing cataract surgery. Established calculations, such as the ASCRS and Barrett True K formula, remain effective options, while under-utilized formulas, like the EKR65 and Camellin-Calossi formulas, show promise, emphasizing the need for further research and larger studies to validate and enhance IOL power calculation for this patient group.

Radial keratotomy: background and how to manage these patients nowadays

In this review, we presented the principles of radial keratotomy (RK), its evolution, enhancement, and complications, and strategies to manage the consequences of RK in the present day. It is essential to understand the RK procedure f, the theoretical background that supported this surgery, the current effect on the cornea, and how to approach patients needing vision improvement. These patients are developing cataracts that need to be handled well, from the IOL calculation to the surgical procedure. Guided keratorefractive surgery is the most accurate procedure to improve these patient's vision and life. Nevertheless, some patients may need other approaches, such as sutures, penetrating keratoplasty, corneal rings, and pinhole implants, depending on the degree of irregularity of the cornea, ablation depth for guided surgery or if the sutures are open.

Cataract surgery following refractive surgery: Principles to achieve optical success and patient satisfaction

A growing number of patients with prior refractive surgery are now presenting for cataract surgery. Surgeons face a number of unique challenges in this patient population that tends to be highly motivated to retain or regain functional uncorrected acuity postoperatively. Primary challenges include recognition of the specific type of prior surgery, use of appropriate intraocular lens (IOL) power calculation formulas, matching IOL style with spherical aberration profile, the recognition of corneal imaging patterns that are and are not compatible with toric and/or presbyopia-correcting lens implantation, and surgical technique modifications, which are particularly relevant in eyes with prior radial keratotomy or phakic IOL implantation. Despite advancements in IOL power formulae, corneal imaging, and IOL options that have improved our ability to achieve targeted postoperative refractive outcomes, accuracy and predictability remain inferior to eyes that undergo cataract surgery without a history of corneal refractive surgery. Thus, preoperative evaluation of patients who will and will not be candidates for postoperative refractive surgical enhancements is also paramount. We provide an overview of the specific challenges in this population and offer evidence-based strategies and considerations for optimizing surgical outcomes.

Comparison of the accuracy of three intraocular lens power calculation formulas in cataract patients with prior radial keratotomy

PURPOSE

To compare the accuracy of three intraocular lens (IOL) formulas in Chinese cataract patients with prior radial keratotomy (RK).

METHODS

Medical records of cataract patients with prior RK at Beijing Tongren Hospital were retrospectively analysed. The absolute error (AE) was calculated as the absolute difference between the actual postoperative spherical equivalent and the predicted spherical equivalent. The AE and percentages of eyes with AE within 0.5D, 1.0D, and 2.0D for three formulas [Barrett True-K, Holladay 1 (D-K), Haigis] were calculated and compared.

RESULTS

Forty-seven eyes of 28 cataract patients were included. The Median AE (MedAE) was significantly different among the three formulas (P < 0.001). The MedAE was lowest for the Barrett True-K formula (0.62), followed by the Haigis (0.76), and Holladay 1 (D-K) (1.16). The percentages of eyes with AE within 0.5D, and 1.0D were significantly different among the 3 formulas (P = 0.009, and P < 0.001). The Barrett True-K formula achieved the highest percentages (46.8%) of eyes with AE within 0.5D. Haigis achieved the highest percentages (70.21%) of eyes with AE within 1.0 D.

CONCLUSIONS

Barrett True-K is the most accurate IOL power calculation formula among the 3 formulas and Haigis is an alternative choice. Considering the relatively lower accuracy of IOL formulas in cataract patients with prior RK, newer and more accurate IOL formulas are desirable.

"Rapid and reversible alteration in corneal contour and power associated with Netarsudil/Latanoprost"

Purpose

To describe a previously unreported case of reversible myopic shift with corresponding changes in corneal contour in a patient treated with netarsudil/latanoprost.

Observations

A 72-year-old male with history of primary open angle glaucoma, prior cataract surgery, and remote radial keratotomy surgery was treated with fixed-dose combination of netarsudil/latanoprost. Despite no prior history of refractive shift in the twenty years since radial keratotomy surgery, on one month follow-up, he reported reduced visual acuity and presented with approximately 1.50 D shift in both eyes. There were associated corneal contour changes. No corneal epithelial bullae or edema were appreciated. Netarsudil/latanoprost was discontinued and timolol was initiated. One month later, both refractive error and corneal contour returned to prior levels.

Conclusions

Netarsudil is a rho-kinase and norepinephrine transporter inhibitor that may be effective in the treatment of primary open angle glaucoma resistant to other topical treatments. In addition to corneal epithelial bullous edema previously reported, this drug may induce reversible changes in corneal contour in patients with prior corneal or refractive surgery.

A rare case of infectious keratitis that developed 27-years after radial keratotomy

Purpose

To report a rare case of bacterial infectious keratitis that developed 27 years after radial keratotomy.

Observations

A 48-year-old female who underwent bilateral radial keratotomy (RK) 27-years previous presented at our department with pain and visual loss in her right eye after being diagnosed with bacterial keratitis by her primary care physician. Slit-lamp examination showed a focus at the deep layer of the cornea, endothelial plaque, and hypopyon. Treatment with topical fortified levofloxacin and cefmenoxime eye drops was initiated. However, at 2 days after the initiation of treatment, there was no improvement, so anterior chamber irrigation and a bacterial smear/culture were performed. The smear showed many gram-positive cocci, yet no organism was detected in the culture. We suspected the causative bacteria to be methicillin-resistant Staphylococcus aureus (MRSA) due to her job (i.e., nursing staff) and the treatment course. Thus, we initiated treatment with 0.5% arbekacin eye drops for the suspected MRSA keratitis, and it was effectively controlled.

Conclusions and Importance

The findings in this case indicate that the incisions used for RK are delicate/fragile and can easily open doors to infection, as they remain unstable for many years post surgery.

A pinhole implant to correct postoperative residual refractive error in an RK cataract patient

Purpose

To report the clinical outcomes after implantation of a pinhole supplementary implant (Xtrafocus, Morcher GmbH, Stuttgart, Germany) to correct fluctuating residual refraction after cataract surgery in a patient with a history of radial keratotomy (RK).

Observations

A 62-year-old patient who had radial keratotomy 22 years earlier, underwent uneventful bilateral cataract surgery using the ASCRS IOL-Calculator for post-RK. Postoperatively, the patient showed fluctuating subjective manifest refraction (MR) on both eyes. To correct the large fluctuating residual refractive error and subjectively worse visual acuity, Xtrafocus IOL was implanted in the right eye. One week later, the uncorrected distance visual acuity (UDVA) was already 0.1 logMAR and the patient stated to have stable vision. Three months after Xtrafocus implantation, the UDVA was −0.04 logMAR which did not improve with MR and the patient expressed high satisfaction, good subjective binocular contrast sensitivity, comparable visual field outcomes, and an elongated depth of focus.

Conclusions and Importance

The pinhole sulcus implant not only helped eliminate the fluctuation in residual refraction after cataract surgery, but also provided an elongated depth of focus without greatly affecting the visual field. The supplementary implantation of the Xtrafocus lens can offer an effective option for the treatment of instable refractive errors after cataract surgery in patients with a history of corneal surgery.

Biology of keratorefractive surgery- PRK, PTK, LASIK, SMILE, inlays and other refractive procedures

The outcomes of refractive surgical procedures to improve uncorrected vision in patients-including photorefractive keratectomy (PRK), laser in-situ keratomileusis (LASIK), Small Incision Lenticule Extraction (SMILE) and corneal inlay procedures-is in large part determined by the corneal wound healing response after surgery. The wound healing response varies depending on the type of surgery, the level of intended correction of refractive error, the post-operative inflammatory response, generation of opacity producing myofibroblasts and likely poorly understood genetic factors. This article details what is known about these specific wound healing responses that include apoptosis of keratocytes and myofibroblasts, mitosis of corneal fibroblasts and myofibroblast precursors, the development of myofibroblasts from keratocyte-derived corneal fibroblasts and bone marrow-derived fibrocytes, deposition of disordered extracellular matrix by corneal fibroblasts and myofibroblasts, healing of the epithelial injury, and regeneration of the epithelial basement membrane. Problems with epithelial and stromal cellular viability and function that are altered by corneal inlays are also discussed. A better understanding of the wound healing response in refractive surgical procedures is likely to lead to better treatments to improve outcomes, limit complications of keratorefractive surgical procedures, and improve the safety and efficiency of refractive surgical procedures.

Effects and risks of 3.2-mm transparent corneal incision phacoemulsification for cataract after radial keratotomy

Objective

This study was performed to analyze the visual outcomes and complications of phacoemulsification using a 3.2-mm transparent corneal incision in eyes with cataract after radial keratotomy (RK).

Methods

We retrospectively reviewed cases of lens phacoemulsification and intraocular lens implantation after RK. The main measurement results were postoperative best-corrected visual acuity (BCVA), endothelial cell density, and complications.

Results

Overall, 19 eyes of 12 patients with 8 (n = 6), 12 (n = 7), and 16 (n = 6) RK cuts were included in the study. Intraoperative wound dehiscence occurred in two eyes with 16 RK cuts. Successful phacoemulsification with intraocular lens implantation was performed in all eyes. The mean BCVA at the last follow-up (0.19 ± 0.13 LogMAR) was significantly better than the preoperative BCVA (0.72 ± 0.54 LogMAR). However, there was a significant reduction in the corneal endothelial cell density after surgery (2384.0 ± 833.4/mm² vs. 1716.95 ± 906.79/mm²).

Conclusions

Surgeons should be aware of the risk of wound dehiscence in patients who undergo phacoemulsification after RK. A small transparent corneal incision or scleral tunnel incision is recommended.

Delayed infectious keratitis in a patient with radial keratotomy and floppy eyelid syndrome treated with simple interrupted stitches

A 55-year-old male presented with an infectious keratitis in his left eye, affecting one of the incisions of the radial keratotomy he had undergone thirty-four years ago. Suturing the incision with two simple interrupted stitches was key to the resolution of the infection. Floppy eyelid syndrome was also found in this patient. Could this act as a risk factor for infectious keratitis in radial keratotomy? To our knowledge, this is the first reported case describing the association between both conditions, and the second reported case where sutures have been used as an adjuvant treatment in these types of cases.

Descemet membrane endothelial keratoplasty for endothelial decompensation after previous radial keratotomy

Purpose

To report Descemet membrane endothelial keratoplasty (DMEK) for endothelial decompensation in an eye with previous radial keratotomy.

Observations

A history of radial keratotomy may hasten endothelial dysfunction. Previously reported surgical treatments include penetrating kerotoplasty and Descemet stripping automated endothelial keratoplasty.

Conclusions and Importance

DMEK may be successfully used in post-RK eyes with good recovery of visual acuity and patient satisfaction.

Intraocular lens power calculation after radial keratotomy and LASIK - A case report

Purpose

To report a challenging intraocular lens (IOL) power calculation case who received both radial keratotomy (RK) and laser-assisted in situ keratomileusis (LASIK).

Observations

A 51-year-old man had received refractive surgery with RK and later enhanced by LASIK more than 20 years ago. He developed severe cataract in left eye with best-corrected visual acuity of 20/100. The IOL power calculation was made using several methods available at the American Society of Cataract and Refractive Surgery (ASCRS) online calculator, including IOL calculation formulas for post-LASIK condition (Shammas, Haigis-L, Barrett True K no history, and Potvin-Hill Pentacam) and formulas for post-RK condition (Double K-modified Holladay 1 based on Oculus Pentacam and IOL Master, and Barrett True K). Haigis-L, Shammas and Barrett true K no history were found to be most accurate in predicting IOL power.

Conclusions

Haigis-L, Shammas and Barrett true K no history are reliable formulas for IOL power calculation in patients who received both RK and LASIK.

Effects of a semi-scleral contact lens on refraction and higher order aberrations

PURPOSE

To investigate effects of Rose K2 XL semi-scleral contact lenses (Menicon Co.) on visual acuity and higher-order aberrations in eyes with irregular corneas.

METHODS

One hundred and twelve eyes of 84 patients fitted with Rose K2 XL lenses were analysed. Participants were in 4 clinical groups: keratoconus, intra-corneal ring segments, radial keratotomy, and penetrating keratoplasty. Corrected distance visual acuity and ocular aberrations were determined before lens wear and 60 min into lens wear. The i-Trace aberrometer was used to determine aberrations at 4.5 mm pupil size.

RESULTS

There were 55, 22, 19 and 16 eyes in keratoconus, intra-corneal ring segments, radial keratotomy and penetrating keratoplasty groups, respectively. Before lens wear, eyes had poor corrected distance vision acuity (mean and standard deviation +0.55 ± 0.33 logMAR), high negative spherical equivalent refraction (-6.4 ± 3.7 D), high cylindrical errors (4.5 ± 2.2 D), large higher-order root-mean-squared (HO-RMS) aberration (1.5 ± 1.3 μm) and large higher-order aberration components. Cylinder was particular high for the penetrating keratoplasty group (mean 5.9 ± 2.5 D), root-mean-squared third-order coma was lowest for the radial keratotomy group (0.7 ± 1.0 μm), and fourth-order spherical aberration was highly negative for the intra-corneal ring segment group (co-efficient -0.4 ± 0.7 μm). With lens wear, the values changed considerably. Corrected distance visual acuity improved by 0.51 ± 0.31 logMAR, cylinder decreased by 3.6 ± 2.1 D, HO-RMS aberration reduced by 1.1 ± 1.2 μm, and higher-order aberration components decreased considerably. Magnitudes of group changes reflected the magnitudes before lens wear.

CONCLUSIONS

Rose K2 XL semi-scleral contact lenses were effective in improving vision and reducing ocular aberrations for eyes with irregular corneas.

Implantation of a Multifocal Toric Intraocular Lens after Radial Keratotomy and Cross-Linking with Hyperopia and Astigmatism Residues: A Case Report

Radial keratotomy is a refractive surgical technique, widely used in the 80s and early 90s to correct myopia and astigmatism, but now overcome by more recent laser techniques. Important consequences, often in patients with more than 45 years of age, are progressive hyperopic shift and/or an increase in corneal astigmatism, whose main cause seems to be an increase in the curvature radius of the central portion of the cornea. This seems to be due to radial keratotomy incisions – with the consequent need for cross-linking – intraocular pressure, and corneal biomechanical parameters. The authors propose phacoemulsification with a customized multifocal toric intraocular lens implantation to correct the induced shift and hyperopic astigmatism. A decent postoperative visual acuity was observed with good patient satisfaction. A specific protocol must be applied to optimize the correct diagnosis, presurgical evaluation and postsurgical outcomes that are to be maintained over time, without regressions.

Correction of hyperopia with astigmatism following radial keratotomy with daily disposable plus spherical contact lens: a case report

Purpose

To report the refractive correction in a case of hyperopia and astigmatism following radial keratotomy.

Methods

A case report.

Results

A 47-year-old woman, who had undergone refractive surgery for radial keratotomy in both eyes 22 years before the present study, presented to our clinic with blurred vision. Her best corrected visual acuity, with spectacle correction of +3.50 DS/−1.50 DCX130° in the right eye and +3.75 DS/−1.50 DCX80° in the left eye, was 0.2 logMAR and 0.3 logMAR, respectively. Her keratometric readings were 35.75 D/36.75 D at 74° and 35.25 D/36.25 D at 61°, respectively. Prompted by intolerance to glasses, the patient requested for contact lenses. First, we applied a rigid, gas-permeable contact lens. However, we noted poor fitting due to central corneal flattening. Subsequently, we applied a conventional plus spherical soft contact lens (PSSCL), which is thick in the center and can therefore correct hyperopia and low-grade astigmatism simultaneously. The conventional PSSCL showed slightly inferior decentration, with good movement, and the patient was satisfied with it. After ascertaining the patient’s living habits, we decided that a daily disposable soft contact lens would most meet her needs. The final prescription was a daily disposable PSSCL; the patient was satisfied with her corrected visual acuity of 0.0 logMAR in the right eye and 0.0 logMAR in left eye. Her daily disposable PSSCL-corrected visual acuity was stable during the 10-month follow-up.

Conclusion

For patients displaying hyperopia with astigmatism following radial keratotomy, the PSSCL may confer better corrected visual acuity and acceptability.

Fuchs' dystrophy associated with radial keratotomy: Lamellar or perforating keratoplasty?

CASE REPORT

A 70 year-old male patient with a history of radial keratotomy suffering from Fuchs' dystrophy and a cataract. The patient received a two-step surgery: lens phacoemulsification and intraocular lens implant, followed by descemet stripping automated endothelial keratoplasty in both eyes, four months later. There were no complications apart from a recurrent cystoid macular oedema in both eyes. The best corrected visual acuity was 20/40 both eyes, and the patient was satisfied.

DISCUSSION

Descemet stripping automated endothelial keratoplasty may be considered as an alternative to penetrating keratoplasty in the case of endothelial dysfunction and radial keratotomy in patients with no corneal ectasia or significant stromal opacity.

Multifocal Corneal Excimer Femtosecond Laser in situ Keratomileusis following Radial Keratotomy: A Case Report with Six Months of Follow-Up

We report the case of a 46-year-old female patient who was referred to our clinic (Orasis Eye Clinic, Reinach, Switzerland) seeking improvement of her distance and near visual acuity. Radial keratotomy (RK) was performed at a younger age on both eyes to correct -5 D myopia. The patient underwent a bilateral same-session multifocal corneal excimer femtosecond laser (Supracor) keratomileusis correction. We introduce a new correction approach, possibly suitable for presbyopic patients previously treated with RK, and we present several potential novel advantages such as enhanced near, intermediate vision, and improvement in quality of life. This is the first report of a bilateral excimer laser treatment attempt of presbyopia following RK.

Penetrating keratoplasty after radial keratotomy and recurrent immune overreaction

A 32-year-old man suffering from keratoconus was treated with radial keratotomy. Twenty weeks later, he presented visual deterioration, edema and corneal perforation. A penetrating keratoplasty was required. The postoperative course was regular, but after 9 months, the patient presented kerato-uveitis. Subsequent phlogistic relapses occurred approximately every 6 months during the following 5 years. The performed cultures were positive only during the first episode. Radial keratotomy is not indicated in keratoconus. The multiple relapses of kerato-uveitis could not be explained by infection, and we hypothesized that they may be due to a ‘traumatic memory’ of the cornea caused by the several suffered traumatisms, without clinical features of corneal graft rejection. The risks of new penetrating keratoplasty and cataract surgery are high. As the cornea is the tissue with the highest sensitivity in the body, we tried to explain the relapsing kerato-uveitis as a consequence of the disruption of the nervous corneal network.