Precision in IOL Calculation for Cataract Patients with Prior History of Combined RK and LASIK Histories.

Purpose: This study aimed to evaluate the accuracy of 12 intraocular lens (IOL) power calculation formulae for eyes that have undergone both radial keratotomy (RK) and laser assisted in situ keratomileusis (LASIK) surgery to determine the efficacy of various IOL calculations for this unique patient group. Currently, research on this surgical topic is limited. Methods: In this retrospective study, 11 eyes from 7 individuals with a history of RK and LASIK who underwent cataract surgery at Hoopes Vision were analyzed. Preoperative biometric and corneal topographic measurements were performed. Subjective refraction was obtained postoperatively. Twelve different intraocular lens (IOL) power calculations were used: Barrett True K No History, Barrett True K (prior LASIK, Prior RK history), Barrett Universal 2, Camellin-Calossi-Camellin (3C), Double K-Modified Holladay, Haigis-L, Galilei, OCT, PEARL-DGS, Potvin-Hill, Panacea, and Shammas. Results: The rankings of mean arithmetic error (MAE), from least to greatest, were as follows: 3C (0.088), Haigis-L-L (-0.508), Shammas (-0.516), OCT Average (-0.538), Barrett True K (-0.557), OCT RK (-0.563), Galilei (-0.570), IOL Master (-0.571), OCT LASIK (-0.583), Barrett True K No History (-0.597), Pearl-DGS (-0.606), Potvin-Hill SF (-0.770), Potvin-Hill TNP (-0.778), Panacea (-0.876), and Barrett Universal 2 (-1.522). The 3C formula achieved the greatest percentage of eyes within ±0.25 D of target range (91%), while Haigis-L, Shammas, Galilei, Potvin Hill, Barrett True K, IOL Master, PEARL-DGS, and OCT formulae performed similarly, achieving 45% of eyes within ±0.75D of target refraction. Conclusion: This study demonstrates the accuracy of the lesser known 3C formula in IOL calculation, particularly for patients who have undergone both RK and LASIK. Well-known formulae, such as Haigis-L, Shammas, and Galilei, which are used by the American Society of Cataract and Refractive Surgery (ASCRS), are viable options, although 3C formulae should be considered in this patient population. Furthermore, larger studies can confirm the best IOL power formulas for post-RK and LASIK cataract patients.

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.

Accuracy of Traditional and Modern Formulas for Intraocular Lens Power Calculation After Radial Keratotomy Using Standard Keratometry.

Purpose: To compare the accuracy of multiple traditional and modern intraocular lens (IOL) power calculation formulas in post-radial keratotomy (RK) patients undergoing cataract surgery. Methods: This retrospective case series included 50 eyes with prior RK who underwent routine phacoemulsification surgery with single-piece acrylic IOL implantation (A constant = 118.8). Outcomes of multiple formulas were calculated. Included formulas were SRK/T, Holladay 1, Holladay 2, Haigis, Barrett True-K, Haigis and Barrett True-K (target refraction of 0.50 D), Barrett Universal II, Kane, PEARL-DGS, Shammas no history, DK SRK/T, DK SRK/T (target refraction of 0.50 D), Double K (DK) Holladay 1, and DK Holladay 1 (target refraction of 0.50 D). Averages of multiple combinations of best-performing single formulas were calculated. Primary outcome is mean absolute error (MAE). Results: Haigis (with -0.50 D target refraction) and DK SRK/T showed the lowest mean and median absolute errors (MedAE) followed by Haigis, Barrett True-K, and Barrett True-K (with -0.50 D target refraction). Combinations of 3, 4, or 5 of best performing single formulas yielded good results with >60% of cases within +0.50 D of intended refraction and MAE around 0.50 D. The best performing formulas with flatter K readings were PEARL-DGS and Haigis (with additional -0.50 D target refraction) with MAE of 0.72 + 0.71 D and 0.70 + 0.70 D, respectively, followed by Barrett True-K (with intended -0.50 D target refraction) with MAE of 0.75 + 0.63 D. Conclusion: Using an average of three or more Haigis (with -0.50 D target refraction), the Barrett True-K, DK Holladay 1, and DK SRK/T formulas showed better outcomes than using a single formula for IOLMaster 700 standard K readings. The PEARL-DGS formula showed better accuracy in eyes with flatter K readings (<38 D).

Comparison of intraocular lens power prediction accuracy of formulas in American Society of Cataract and Refractive Surgery post-refractive surgery calculator in eyes with prior radial keratotomy.

Purpose: To evaluate the accuracy of intraocular lens (IOL) power prediction of the formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) post-refractive calculator in eyes with prior radial keratotomy (RK) for myopia. Methods: This retrospective study included 25 eyes of 18 patients whose status was post-RK for treatment of myopia, which had undergone cataract extraction with IOL implantation. Prediction error was calculated as the difference between implanted IOL power and predicted power by various formulae available on ASCRS post-refractive calculator. The formulas compared were Humphrey Atlas method, IOLMaster/Lenstar method, Barrett True-K no-history formula, ASCRS Average power, and ASCRS Maximum power on ASCRS post-refractive calculator. Results: Median absolute errors were the least for Barrett True-K and ASCRS Maximum power, that is, 0.56 (0.25, 1.04) and 0.56 (0.25, 1.06) D, respectively, and that of Atlas method was 1.60 (0.85, 2.28) D. Median arithmetic errors were positive for Atlas, Barrett True-K, ASCRS Average (0.86 [-0.17, 1.61], 0.14 [-0.22 to 0.54], and 0.23 [-0.054, 0.76] D, respectively) and negative for IOLMaster/Lenstar method and ASCRS Maximum power (-0.02 [-0.46 to 0.38] and - 0.48 [-1.06 to - 0.22] D, respectively). Multiple comparison analysis of Friedman's test revealed that Atlas formula was significantly different from IOLMaster/Lenstar, Barrett True-K, and ASCRS Maximum power; ASCRS Maximum power was significantly different from all others (P < 0.00001). Conclusion: In post-RK eyes, Barrett True-K no-history formula and ASCRS Maximum power given by the ASCRS calculator were more accurate than other available formulas, with ASCRS Maximum leading to more myopic outcomes when compared to others.

FLACS combined with IOLI is comparable to Phaco combined with IOLI in cataract patients after refractive surgery.

OBJECTIVE: To characterize the clinical features of cataract surgery performed after refractive surgery. METHODS: In this study, 23 patients with cataracts (38 eyes) who underwent cataract surgery following refractive surgery at the Shenzhen Aier Eye Hospital between the years 2017 and 2021 were retrospectively included for analysis. The patients had either femtosecond laser-assisted cataract surgery (FLACS) combined with intraocular lens implantation (IOLI), or conventional phacoemulsification (Phaco) combined with IOLI. The type and power of an intraocular lens (IOL) were selected based on the ocular condition, needs, and living habits of patients. Intraoperative complications, postoperative intraocular pressure (IOP), uncorrected visual acuity (UCVA), and postoperative refractive status were all recorded and analyzed. RESULTS: The patients had a postoperative UCVA that was significantly better than the baseline (prior to operation), a postoperative IOP and diopter (D) similar to the baseline and a high level of postoperative satisfaction. The postoperative visual acuity, D and complication rate of FLACS+IOLI group were not significantly different from those of Phaco+IOLI group, and the IOP of the former was statistically lower than that of the latter. CONCLUSIONS: FLACS with IOLI or conventional Phaco with IOLI is feasible for cataract patients who have undergone refractive surgery. In terms of IOL selection, multifocal, extended range of vision (ERV), or trifocal types can be selected to achieve the goal of lens removal after surgery, but the decision should be made based on the patient's specific eye condition, living needs, and economic circumstances. To achieve satisfactory curative effects, it is necessary to have a comprehensive understanding of the characteristics of the condition of such patients, to master the pre- and post-operative diagnosis and treatment methods, to accurately calculate the IOLP, to fully communicate with patients about their surgical expectations, and to develop feasible surgical plans.

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.

Ray tracing biometry in post radial keratotomy eye.

OBJECTIVE: To report a case of post radial keratotomy (RK) cataract in a 55-year-old lady wherein biometry was done by ray-tracing method incorporated in scheimpflug topographer (Sirius + Scheimpflug Analyzer, CSO, Italy). METHOD: In our case, we performed intraocular lens (IOL) power calculation using a recent concept of ray tracing with scheimpflug topographer and compared with traditional methods available at American Society of Cataract and Refractive Surgery(ASCRS) website (www.ascrs.org) for eyes with prior RK. Phacoemulsification was performed and a monofocal + 24.5D IOL implanted in the capsular bag. RESULT: Manifest refraction at six weeks postoperative period was + 1.0DS/-2.0DC × 75° with spherical equivalence of 0. On comparison of all the methods used to calculate IOL power, the absolute errors of ray tracing and Barrett true K were found to be the least, 0.14 and 0.18 respectively. CONCLUSION: Ray tracing biometry with scheimpflug topographer seems to provide accurate IOL power in post RK eyes.

Comparison of accuracy of intraocular lens calculation formulas in cataract eyes with prior radial keratotomy and axial length longer than 28mm / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the accuracy of different intraocular lens(IOL)calculation formulas in cataract patients with axial length longer than 28mm and a history of radial keratotomy(RK).METHODS: Retrospective study. The medical records of 19 cataract patients(29 eyes)after RK and with axial length longer than 28mm who underwent cataract surgery from January 2011 to July 2020 in Beijing Tongren Hospital were analyzed. The absolute error(AE)of the difference among three different formulas was calculated. AE refers to the absolute value between the actual spherical equivalent after cataract surgery and the spherical equivalent predicted by the IOL formula. The AE values of the three formulas and the percentages of eyes with AE≤0.5, 0.75, 1.0, and 2.0D were calculated and compared.RESULTS: The AE values of the three formulas were significantly different(χ2=8.759, P=0.013). The Barrett True-K formula had the smallest median AE, which was only 0.62(0.20, 1.15)D, followed by the Haigis formula 0.76(0.34, 1.26)D, and the Holladay 1(D-K)formula had the largest 1.01(0.49, 1.62)D. The percentages of affected eyes with AE ≤0.5, 0.75, 1.0, and 2.0D for the Barrett True-K formula were 48%, 59%, 69%, and 93%, which were equal to or higher than the other two formulas.CONCLUSION: The Barrett True-K formula is more recommended among the three formulas for cataract patients after RK and with axial length longer than 28 mm.

Vision Quality Questionnaire Assessment in Patients After Topography-Guided Photorefractive Keratectomy for Irregular Astigmatism Secondary to Radial Keratotomy.

Aim: To evaluate the vision-related quality of life with the National Eye Institute Refractive Error Quality of Life (NEI-RQL) questionnaire in patients with astigmatism secondary to radial keratotomy surgery who underwent topography-guided photorefractive keratectomy. Methods: Prospective non-randomized clinical trial. This study included 15 patients (30 eyes) aged > 21 years, mean age 55.1 (SD, 3.5) years, 53.3% female, with astigmatism ≤ - 6.00 D resulting from radial keratotomy, which could have been associated with hyperopia ≤ + 6.00 D. Photorefractive keratectomy with topography-guided custom ablation treatment was used in all cases. The patients answered the NEI-RQL questionnaire preoperatively and at 4 and 48 months after topography-guided photorefractive keratectomy. The following data were collected: age, sex and education level, pre-operative refraction data, visual acuity with or without correction, pachymetry, and keratometry. Results: There was a significant difference between pre-and postoperative NEI-RQL scores for the domains clarity of vision, near vision, far vision, diurnal fluctuation, activity limitations, glare, symptoms, correction dependence, appearance, and satisfaction with correction (p < 0.001). Conclusion: Topography-guided photorefractive keratectomy improved vision-related quality of life in patients with a history of irregular astigmatism secondary to radial keratotomy.

Radiofrequency diathermy as a treatment of lipid keratopathy in a radial keratotomy incision.

Purpose: We report a case of lipid keratopathy in a radial keratotomy incision that was successfully managed with radiofrequency diathermy of the neovascular pedicle responsible for the lipid deposition. Observations: No perioperative or postoperative complications were noted. Following the procedure, the lesion showed significant decrease in lipid deposits and opacification along with disappearance of the neovascular pedicle. Conclusions and importance: Radiofrequency diathermy of neovascular pedicle may represent an effective and safe alternative treatment option for treating lipid keratopathy. This is a first ever report of lipid keratopathy inside a radial keratotomy incision that was successfully managed by radiofrequency diathermy.

Cataract Surgery after Radial Keratotomy with Non-Diffractive Extended Depth of Focus Lens Implantation.

Radial keratotomy was a popular surgical procedure used to treat myopia. Patients who underwent radial keratotomy several years ago, are currently reporting to the ophthalmologist due to worsening of vision associated with age-related cataracts. In this case report we present a case of a 60-year-old woman who underwent radial keratotomy with 16 incisions in the right eye and 12 incisions in the left eye. The patient reported to an ophthalmologist due to a deterioration of vision caused by a cataract. We described, in detail, the difficulties encountered during the diagnostic procedures, differences in the calculation of intraocular lens, and intraoperative difficulties as compared to patients who had not undergone radial keratotomy. We also present the obtained postoperative results.

Intraocular lens power calculation after two different successive corneal refractive surgeries.

Purpose: To report two challenging intraocular lens power calculation cases with patients each underwent different successive corneal refractive surgeries, respectively. Observations: Biometry data, including the Back to Front corneal radii ratio (B/F ratio), were collected by Lenstar, IOL Master, and Pentacam AXL for Case 1 (received radial keratotomy (RK) and photorefractive keratectomy (PRK)) and Case 2 (received RK and laser-assisted in situ keratomileusis (LASIK)). The IOL power calculation was determined by several methods, including Shammas, Haigis-L, and Barrett True-K, which are available in the American Society of Cataract and Refractive Surgery online calculator and Pentacam AXL. The Barrett True-K (no history, post-RK) was more accurate in Case 1 (increased B/F ratio), whereas the Shammas, Haigis-L, and Barrett True-K (no history, post-LASIK/PRK) were more accurate in Case 2 (decreased B/F ratio). Conclusion and importance: The B/F ratio may be a factor to be considered when selecting the IOL power calculation formula for patients who undergo two different corneal refractive surgeries. The further study focusing on this issue should be performed to clarify the results in the future.

"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.

Intraocular lens power calculations in eyes with previous corneal refractive surgery: Challenges, approaches, and outcomes.

In eyes with previous corneal refractive surgery, difficulties in accurately determining corneal refractive power and in predicting the effective lens position create challenges in intraocular lens (IOL) power calculations. There are three categories of methods proposed based on the use of historical data acquired prior to the corneal refractive surgery. The American Society of Cataract and Refractive Surgery postrefractive IOL calculator incorporates many commonly used methods. Accuracy of refractive prediction errors within ± 0.5 D is achieved in 0% to 85% of eyes with previous myopic LASIK/photorefractive keratectomy (PRK), 38.1% to 71.9% of eyes with prior hyperopic LASIK/PRK, and 29% to 87.5% of eyes with previous radial keratotomy. IOLs with negative spherical aberration (SA) may reduce the positive corneal SA induced by myopic correction, and IOLs with zero SA best match corneal SA in eyes with prior hyperopic correction. Toric, extended-depth-of-focus, and multifocal IOLs may provide excellent outcomes in selected cases that meet certain corneal topographic criteria. Further advances are needed to improve the accuracy of IOL power calculation in eyes with previous corneal refractive surgery.

Treatment of Corneal Irregularity in Radial/Astigmatic Keratotomy Patients Utilizing WaveLight Contoura.

PURPOSE: To demonstrate the treatment of radial keratotomy-induced corneal irregularity with topographic-guided ablation (WaveLight Contoura). METHODS: Thirty-two eyes of 18 patients were treated for corneal irregularity post-radial keratotomy with WaveLight Contoura topographic-guided ablation utilizing LASIK and PRK and the San Diego Protocol for reconstructing corneas. These eyes were followed for six-months. Outcomes included: measurements of vision, refraction, residual higher-order aberrations, residual lower-order and higher-order aberrations, as well as loss or gains of lines of best-corrected visual acuity. RESULTS: All eyes had decreased corneal irregularity as evidenced by topographic analysis and reduction in manifest astigmatism, Contoura-measured astigmatism, higher-order aberrations, and higher-order aberrations grouped with lower-order aberrations excluding tilt (Grouped). The eyes of 5 sample patients are included in this manuscript to demonstrate the procedure, protocol, and outcomes. CONCLUSION: Treatment with WaveLight Contoura whether as LASIK or PRK appears to be an effective treatment for corneal irregularity associated with radial/astigmatic keratotomy.

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.

Accuracy and safety of partial thickness femtosecond laser radial and arcuate keratotomy incisions in porcine eyes.

BACKGROUND: To evaluate the accuracy and safety of micro radial and arcuate keratotomy incisions constructed by a femtosecond laser system with a curved contact patient interface in porcine eyes. METHODS: Partial thickness micro radial and arcuate keratotomy incisions were constructed in porcine eyes with a femtosecond laser system and evaluated for precision of depth, quality, and consistency. Optical coherence tomography was used to determine the accuracy and precision of incision depth. Corneal endothelial safety was assessed by a fluorescent live/dead cell viability assay to demonstrate laser-induced endothelial cell loss. Quality was evaluated by ease of opening and examination of interfaces. RESULTS: In two micro radial incision groups, intended incision depths of 50% and 80% resulted in mean achieved depths of 50.01% and 77.69%, respectively. In three arcuate incision groups, intended incision depths of 80%, 600 µm or 100 µm residual uncut bed thickness resulted in mean achieved depths of 80.16%, 603.03 µm and residual bed of 115 µm, respectively. No loss of endothelial cell density occurred when the residual corneal bed was maintained at a minimum of 85-116 µm. The incisions were easy to open, and interfaces were smooth. CONCLUSIONS: A femtosecond laser system with curved contact interface created precise and reproducible micro radial and arcuate keratotomy incisions. Accuracy and precision of the incision depth and preservation of endothelial cell density demonstrated the effectiveness and safety of the system.

[Radial keratotomy: history and current state]. / Radial'naya keratotomiya: istoriya i real'nost'.

Results of clinical use of the radial keratotomy (RK) surgery are presented in the format of a lecture and a summary. The analysis encompasses the mechanism of changes in corneal refraction, immediate intra- and postoperative complications, so-called secondary symptoms and long-term effects (addition of various pathological processes, influence of corneal changes on the results of diagnostic tests and treatment methods) of the surgery.