Refractive complications of cataract surgery after radial keratotomy

Navigating Retinal Complications and Refractive Outcomes in High Myopia: A Case Report With Multi-surgical Interventions

Refraction through the ocular system is the process of bending light rays within the eye's optical system, which includes the cornea, anterior chamber, lens, and vitreous body. These structures work together to ensure precise focusing of light on the retina, enabling clear vision. Dysfunction or pathology at any level of the optical system can significantly affect the quality of vision, leading to changes in refractive status and visual acuity disturbances. A 58-year-old female patient presented to the Ophthalmology Clinic for a follow-up evaluation of her visual system after multiple previous surgeries, including radial keratotomy, multiple pars plana vitrectomies (PPV) due to recurrent retinal detachments, cataract phacoemulsification with intraocular lens implantation, and bilateral YAG-capsulotomy. Visual acuity was 0.004 in the right eye (OD) and 0.01 in the left eye (OS), with intraocular pressure of 20 mmHg in the OD and 18 mmHg in the OS. Autorefractor measurements were OD: +1.25/-4.0 ax 110° and OS: +1.25/-4.75 ax 130°. Pachymetry showed a central corneal thickness of 532μm in the OD and 518μm in the OS. Refraction measured by the WASCA (Wavefront Aberration Supported Cornea Ablation; (Carl Zeiss Meditec, Oberkochen, Germany)) wavefront aberrometer was +5.36/-2.43 ax 129° in the OD and +1.34/-4.08 ax 110° in the OS. Biometry results were 31.02 mm for the OD and 31.87 mm for the OS. High myopia presents complications that contemporary ophthalmology is capable of managing, even in its most severe stages. Advances in modern treatment methods often enable specialists to maintain functional visual acuity, ensuring patients can achieve a meaningful level of vision despite the challenges posed by advanced myopic conditions.

Clinical Outcomes of Modified Manual Deep Anterior Lamellar Keratoplasty for Eyes with Previous Radial Keratotomy

Background: The aim of this study was to evaluate the intraoperative complications and visual outcomes of manual deep anterior lamellar keratoplasty (mDALK) in patients who underwent previous radial keratotomy (RK) for myopia. Methods: The notes of patients who underwent mDALK after RK at three different hospitals-San Giovanni Addolorata Hospital (Rome, Italy), Mount Saint Joseph Hospital (Vancouver, Canada), and Tor Vergata University Hospital (Rome, Italy)-were retrospectively reviewed. We analyzed the manual dissection success rate and conversion to penetrating keratoplasty (PK), the residual recipient stromal thickness, the postoperative corrected distance visual acuity (CDVA), postoperative refraction, and topographic astigmatism. Results: Thirteen eyes of eleven patients were included in the analysis (male 7/11, 63.6%). Preoperatively, mean topographic astigmatism was 5.4 ± 3.5 D (range 1.6-14.8 D), and mean CDVA was 0.47 ± 0.2 logMAR (range 0.3-1.0 logMAR) [Snellen equivalent 20/50]. Manual dissection was performed in all cases. None of the examined eyes were converted to PK. An improvement in both topographic astigmatism (2.8 ± 0.9 D, p = 0.0135) and CDVA (0.23 ± 0.2 LogMAR, p = 0.0122) was recorded at 12-month follow-up. Conclusions: mDALK is a safe and effective surgical technique when applied to eyes previously treated with RK, with an observed improvement in CDVA and topographic astigmatism.

Bilateral Light-Adjustable Lens Implantation in a Patient With 50-Cut Radial Keratotomy

Purpose

To report a case of Light Adjustable Lens™ (LAL, RxSight, Aliso Viejo, CA) implantation in a patient with bilateral 50-cut radial keratotomy (RK) and discuss related preoperative, intraoperative, and postoperative considerations.

Methods

A 78-year-old patient with history of bilateral 50-cut RK underwent phacoemulsification with implantation of LALs in both eyes one month apart. Although LAL technology was not approved specifically for addressing limitations in intraocular lens calculation post-RK due to corneal topography irregularity, the patient opted for this lens due to its ability to make post-operative adjustments to its refractive power. At postoperative month one following the second eye surgery, YAG capsulotomy was performed in both eyes. At postoperative month two following the second eye surgery, the patient began LAL adjustments spaced 1-2 weeks apart for a total of 2 LAL adjustments and 2 lock-in sessions.

Results

Our patient achieved a final refraction of -0.25 +0.25 × 110 with an UDVA of 20/20-2 in the right eye and -0.25 +0.50 × 135 with an UDVA 20/25-1 in the left eye.

Conclusions

The LAL may be a promising option for patients undergoing cataract surgery after RK, although further studies are needed to understand long-term changes in eyes with RK and the inability of LAL to address all aspects of corneal aberration.

Comparison of intraocular lens power prediction by American Society of Cataract and Refractive Surgery formulas and Barrett True-K TK in eyes with prior laser refractive surgery

PURPOSE

To evaluate the prediction accuracy of various intraocular lens (IOL) power calculation formulas on American Society of Cataract and Refractive Surgery (ASCRS) calculator and Barrett True-K total keratometry (TK) in eyes with previous laser refractive surgery for myopia.

METHODS

This retrospective study included eyes with history of myopic laser refractive surgery, which have undergone clear or cataractous lens extraction by phacoemulsification followed by IOL implantation. Those who underwent uneventful crystalline lens extraction were included. Eyes with any complication of refractive surgery or those with eventful lens extraction procedure and those who were lost to follow-up were excluded. Formulas compared were Wang-Koch-Maloney, Shammas, Haigis-L, Barrett True-K no-history formula, ASCRS average power, ASCRS maximum power on the ASCRS post-refractive calculator and the IOLMaster 700 Barrett True-K TK. Prediction error was calculated as the difference between the implanted IOL power and the predicted power by various formulae available on ASCRS online calculator.

RESULTS

Forty post-myopic laser-refractive surgery eyes of 26 patients were included. Friedman's test revealed that Shammas formula, Barrett True-K, and ASCRS maximum power were significantly different from all other formulas (P < 0.00001 for each). Median absolute error (MedAE) was the least for Shammas and Barrett True-K TK formulas (0.28 [0.14, 0.36] and 0.28 [0.21, 0.39], respectively) and the highest for Wang-Koch-Maloney (1.29 [0.97, 1.61]). Shammas formula had the least variance (0.14), while Wang-Koch-Maloney formula had the maximum variance (2.66).

CONCLUSION

In post-myopic laser refractive surgery eyes, Shammas formula and Barrett True-K TK no-history formula on ASCRS calculator are more accurate in predicting IOL powers.

Refractive Outcomes With New Generation Formulas for Intraocular Lens Power Calculation in Radial Keratotomy Patients

PURPOSE

Radial keratotomies (RKs) are responsible for corneal irregularities resulting in biometric errors and lower best-corrected visual acuity (BCVA) due to lower-order and higher-order optical aberrations. The aim of the study was to compare performances of new and old generation formulas in a population of RK patients.

METHODS

RK patients who underwent phacoemulsification with intraocular lens (IOL) implantation were retrospectively recruited. Inclusion criteria were availability of preoperative and 6-month postoperative BCVA assessment, topography, and tomography. Documented refraction instability, corneal ectasia, and previous ocular surgery except for RK were exclusion criteria. Mean prediction error (ME), mean absolute prediction error (MAE), and incidence of MAE > 0.25D were calculated for SRK-T, Barrett True K, EVO 2.0, Kane, and PEARL-DGS.

RESULTS

Twenty-seven patients with a mean baseline BCVA of 0.32 ± 0.18 logMAR and a mean corneal root mean square (RMS) value of 1.59 ± 0.91 μm were included. EVO 2.0, Kane, and PEARL-DGS showed a significantly lower MAE and lower ME compared with all other formulas ( P < 0.001 and P < 0.001) and a significant lower incidence of MAE >0.25D ( P < 0.001). Significant differences were still detected when using 3-mm mean keratometry for IOL calculation.

CONCLUSIONS

PEARL-DGS, Kane, and EVO 2.0 formulas show superior accuracy in IOL power calculation compared with SRK-T and Barrett True K in RK patients, with no significant differences between the 3.

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 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.

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).

Intraocular lens power calculation after radical keratotomy and photorefractive keratectomy: A case report

RATIONALE

To report a rare case of calculating the IOL power in a cataract patient who underwent both radial keratotomy (RK) and photorefractive keratectomy (PRK).

PATIENT CONCERNS

A 48-year-old woman underwent bilateral RK at age 22 and bilateral PRK at age 46. She developed bilateral corneal haze and corneal endothelial inflammation and received steroids therapy for long time after PRK. Then she was referred to our hospital due to decreased vision in the both eyes.

DIAGNOSES

The patient was diagnosed with binocular complicated cataract, corneal haze, high myopia and post corneal refractive surgery (RK and PRK).

INTERVENTIONS

The patient underwent bilateral phacoemulsification. The IOL power was calculated using SRK/T formula for RK and Haigis-L formula for PRK, respectively. We finally selected the Haigis-L formula and the intraocular lens (SN60WF) was implanted within the capsular bag.

OUTCOMES

After the surgery, both eyes showed myopia drift, and the right eye continuously fluctuated in refractive results. However, by nearly 1 year later, refractive results in both eyes had stabilized, and no other complications had occurred.

LESSONS

IOL power in patients who undergo both RK and PRK can be reliably calculated using the Shammas-PL, Average of multiple formulas, or Barret True-K No History formulas. Haigis-L formula is not suitable. Such patients require at least three months after surgery to attain refractive stability in both eyes.

Influence of Posterior Corneal Asphericity On Power Calculation Error After Laser In Situ Keratomileusis or Photorefractive Keratectomy for Myopia

OBJECTIVES

To assess the impact of posterior corneal asphericity on postoperative calculation error using the Haigis-L and the Barrett formulas for eyes after laser in situ keratomileusis or photorefractive keratectomy (PRK).

METHODS

We assessed the mean absolute error (MAE) of two power calculation formulas, Barrett true-K and Haigis-L formulas, in a retrospective analysis of 34 eyes of 34 patients who underwent cataract surgery. We performed a regression analysis between corneal parameters (anterior and posterior Q values, Kmax, K1, and K2) and the MAE of each formula.

RESULTS

In the cohort, 11 eyes were of women and 23 of men. The average age of the study population was 66.5±8.6 years. The mean axial length was 24±4.7 mm, the mean anterior chamber depth was 3.27±0.7 mm, and the mean posterior Q-value was -0.15±0.28. The MAE of Haigis-L and Barrett true-K formulas were 0.72 and 0.68, respectively (P=0.54). The regression analysis showed a statistically significant relationship only between the error in refraction prediction and the posterior Q-value regardless of the formula used. The coefficient of determination was higher for the Barrett true-K formula (r=0.52; R2=0.28; P<0.05), compared with the Haigis-L (r=0.49; R2=0.25; P<0.05).

CONCLUSIONS

Posterior corneal surface asphericity influences the refractive error of calculation using both Haigis-L and Barrett true-K formulas for eyes after a myopic PRK or laser-assisted in situ keratomileusis surgery.

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.

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.

Intraocular Lens Power Calculations in Eyes with Previous Corneal Refractive Surgery: Review and Expert Opinion

Intraocular lens (IOL) power calculations are less accurate in eyes that have undergone corneal refractive surgery. A wide range of methods have been proposed. We reviewed the methods and outcomes of IOL power calculations in eyes with previous LASIK, excimer laser photorefractive keratectomy (PRK), or radial keratotomy (RK). The PubMed database was searched for articles that (1) discuss methods and outcomes of IOL power calculation in eyes with previous corneal refractive surgery and (2) evaluate the outcomes of toric, multifocal, or extended depth-of-focus (EDOF) IOLs in these eyes. We excluded review articles, case reports or case studies, and non-English reports. Seventy full-text articles were included in this review. Three categories of methods exist based on whether and how they use historical data acquired before the corneal refractive surgery. The American Society of Cataract and Refractive Surgery (ASCRS) postrefractive IOL calculator incorporates many commonly used methods. In eyes with previous myopic LASIK or PRK, hyperopic LASIK or PRK, and RK, 0% to 85%, 38.1% to 71.9%, and 29% to 87.5% of eyes, respectively, showed refractive prediction errors within ±0.5 diopter (D); in eyes with toric IOL implantation that met certain inclusion criteria, 80%, 84%, and 69% of eyes, respectively, achieved postoperative astigmatism of 0.50 D or less. Intraocular lenses with negative spherical aberration (SA) will reduce the positive corneal spherical aberration induced in eyes by myopic LASIK or PRK or by RK. Intraocular lenses with 0 SA on average best match corneal SA in eyes with prior hyperopic LASIK or PRK. Studies have reported excellent outcomes of postrefractive eyes implanted with multifocal or EDOF IOLs; however, corneal topographic enrollment criteria were not specified. Despite availability of new measurement technologies and development of new IOL calculation formulas, further advances are needed to improve outcomes of cataract surgery in eyes that have undergone corneal refractive surgery. Tools like the ASCRS postrefractive IOL calculator are useful for the clinician by incorporating a variety of formulas. Toric, EDOF, and multifocal IOLs may provide excellent outcomes in selected cases that meet certain corneal topographic criteria.

Accuracy of Astigmatism Correction with Toric Intraocular Lens Implantation in Eyes with Prior Radial Keratotomy

PURPOSE

To evaluate refractive outcomes of toric intraocular lens (IOL) implantation in eyes with previous radial keratotomy (RK).

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

DESIGN

Retrospective case series.

METHODS

Consecutive cases with previous RK and had undergone cataract surgery with Toric IOL implantation and met these criteria were retrospectively reviewed: (1) regular bowtie corneal astigmatism within the central 3.0-mm zone, (2) difference in corneal regular astigmatism magnitude between the IOL Master and Lenstar of ≤ 0.75 D, and (3) difference in the regular astigmatism meridians from the 2 biometers of ≤ 15 degrees, and (3) available postoperative manifest refraction at ≥ 8 weeks with corrected distance visual acuity of 20/30 or better. Vector analysis was used to assess the preoperative corneal and postoperative refractive astigmatism.

RESULTS

In 40 eyes of 31 patients with previous RK, preoperatively the mean magnitude of corneal regular astigmatism was 2.10 ± 0.98 diopters (D), 1 (3%) and 2 (10%) eyes had anterior corneal regular astigmatism ≤0.5 D and ≤1.0 D respectively, and the centroid value was 1.14 D @ 179° ± 2.05D. Postoperatively, the mean magnitude of refractive regular astigmatism was 0.46 ± 0.44D (D), 29 (73%) and 35 (88%) of eyes had refractive regular astigmatism ≤0.5 D and ≤1.0 D respectively, (P<0.05), and the centroid value was 0.12 D @ 173° ± 0.63 D (P<0.05).

CONCLUSIONS

Toric IOLs can be used successfully to treat corneal regular astigmatism in eyes with previous RK.

Outcomes of Femtosecond Laser-Assisted Cataract and Refractive Lens Surgery in Patients with Prior Radial Keratotomy

PURPOSE

To investigate outcomes of femtosecond laser (FL-) assisted cataract surgery (FLACS) and refractive lens exchange (RLE) in patients with prior radial keratotomy (RK).

SETTING

Single clinical practice.

DESIGN

Retrospective observational case series.

METHODS

All patients with prior RK undergoing FLACS- or FL-assisted RLE surgeries over a 6-year period were reviewed. Inclusion criteria were diurnal stability and stable manifest refraction. Exclusion criteria included any other incisional corneal surgery, macular or glaucomatous pathology, or vision loss from any other cause. Data collected included demographics, visual acuity, laser settings, and complications. Main outcome measures were intra- and postoperative complications and visual outcomes. Safety and efficacy indices were evaluated.

RESULTS

Sixteen eyes of 9 patients were included. Average age and follow-up time were 59.9 ± 9.9 years (range 44-75 years) and 3.3 ± 2.5 months, respectively. Average number of RK cuts was 11.8 ± 5.3 (range 8-20). Mean preoperative UDVA and CDVA were 0.9 ± 0.4 logMAR (Snellen 20/160) and 0.2 ± 0.3 logMAR (Snellen 20/30), respectively. Two intraoperative anterior capsule (AC) tears were identified. One postoperative IOL dislocation occurred. Postoperatively, the mean UDVA and CDVA were 0.2 ± 0.2 logMAR (20/30) and 0.1 ± 0.1 logMAR (20/25), respectively. Safety index was 1.6 and efficacy index was 1.2.

CONCLUSIONS

FLACS- or FL-assisted RLE surgery in RK patients has a high risk of anterior capsule tear and should be avoided. Thickened incisional scars are potential sources of incomplete laser penetrance. Toric lens implantation in RK eyes provide unpredictable astigmatic correction and should also be avoided.

Method for IOL Power Calculation in the Second Eye of Patients With Previous Keratorefractive Surgery

PURPOSE

To describe and evaluate a method for calculating intraocular lens (IOL) power in the second operative eye of patients with a history of keratorefractive surgery.

METHODS

All eyes had undergone cataract surgery by a single surgeon from 2015 to 2018. Postoperative outcomes on the first eye (eg, IOL power implanted and postoperative refractive error) were used to back calculate a "Real K" for the first eye. The difference (delta) between the second and first eye topographic simulated keratometry values was then added to the first eye Real K to calculate the second eye Real K. This Real K value was inputted into the Holladay IOL Consultant software as an "alternate K" to derive an accurate IOL power for the second eye. Mean absolute error, mean error, and percentage of eyes on target using the Delta K method were compared with results obtained with intraoperative abserrometry and the Haigis-L and Barrett True-K No History formulas.

RESULTS

The mean error for the Delta K method was significantly better than the Haigis-L (P = .00001) and Barrett True-K No History (P = .027) formulas, and on par with intra-operative aberrometry (P = .25). The mean absolute error of the Delta K method was significantly better than the Haigis-L formula (P = .03). The Delta K mean absolute error was on par with intraoperative aberrometry (P = .81) and the Barrett True-K No History formula (P = .56).

CONCLUSIONS

The Delta K mean absolute error is comparable to the Barrett True-K No History formula. The mean error is lower than that calculated with the Barrett True-K No History formula and comparable to intraoperative aberrometry. [J Refract Surg. 2020;36(12):826-831.].

IOL Power Calculation After Radial Keratotomy Using the Haigis and Barrett True-K Formulas

PURPOSE

To compare the accuracy of intraocular lens (IOL) power calculation in patients with previous radial keratotomy using the Haigis and Barrett True-K formulas.

METHODS

In a retrospective cases series of patients with previous radial keratotomy and minimum follow-up of 1.2 months, preoperative data from an IOLMaster 500 or 700 (Carl Zeiss Meditec AG), the IOL power implanted, and the postoperative refraction were used to calculate the refractive prediction error. The primary outcomes were the mean absolute and arithmetic refractive prediction errors and the percentage of eyes with a refractive prediction error within ±0.50 and ±1.00 diopters (D).

RESULTS

One hundred eight eyes were evaluated with a mean follow-up of 6.9 ± 4.9 months. The Haigis formula yielded a mean arithmetic refractive prediction error of -0.29 ± 1.00 D, which was significantly different than that of the Barrett True-K formula, which was -0.03 ± 0.96 D (P < .001). The mean absolute refractive prediction error was 0.80 ± 0.67 for the Haigis formula and 0.74 ± 0.60 for the Barrett True-K formula (P > .05). The percentages of eyes with a refractive prediction error within ±0.50 and ±1.00 D were 43.5% and 65.7% for the Haigis formula and 42.6% and 75.9% for the Barrett True-K formula, respectively (all P > .05). The subgroup analysis revealed that for flat corneas (K1 < 38.00 D), the Barrett True-K formula resulted in more hyperopic results than the Haigis formula.

CONCLUSIONS

The Barrett True-K formula exhibited better arithmetic predictability than the Haigis formula; however, it showed a tendency for hyperopic results in very flat corneas. [J Refract Surg. 2020;36(12):832-837.].

Innovative trifocal (quadrifocal) presbyopia-correcting IOLs: 1-year outcomes from an international multicenter study

Trifocal IOLs provided an excellent safety profile with satisfactory patient outcomes for UDVA, DCIVA, and UNVA. Defocus curve demonstrated 20/25 Snellen or better visual acuity at near to intermediate distance.

Purpose:

To evaluate visual acuity (VA) and safety of the new AcrySof IQ PanOptix presbyopia-correcting IOL at 12 months postimplantation.

Setting:

Seventeen sites in Europe, Australia, and South America.

Design:

Prospective, single-arm, nonmasked, nonrandomized study.

Methods:

Of 167 patients enrolled, 149 received study IOLs in both eyes; 145 completed the study. Binocular uncorrected distance VA (UDVA; 4 m), monocular corrected distance VA (CDVA), binocular distance-corrected intermediate VA (DCIVA; 60 cm and 80 cm), binocular uncorrected near VA (UNVA; 40 cm), and binocular defocus curves were evaluated. Safety was assessed by monitoring adverse events (AEs).

Results:

Of 149 patients, 92 patients (62%) were women and 139 patients (93%) were white; mean ± SD age was 68.9 ± 9.3 years. At 12 months, mean binocular UDVA was 0.02 ± 0.11 logarithm of the minimum angle of resolution (logMAR); monocular CDVA was 0.01 ± 0.13 logMAR (first eye) and 0.01 ± 0.10 logMAR (second eye); binocular DCIVA was 0.04 ± 0.12 logMAR and 0.08 ± 0.14 logMAR at 60 cm and 80 cm, respectively; and binocular UNVA was 0.07 ± 0.11 logMAR. At 6 months, mean binocular defocus curve VA (0.00 diopter [D] to −3.00 D) ranged from −0.04 to 0.13 logMAR. Binocular VA at distance (0.00 D), intermediate (−1.50 D), and near (−2.50 D) was −0.04 ± 0.11 logMAR, 0.07 ± 0.13 logMAR, and 0.07 ± 0.13 logMAR, respectively. Serious ocular AE rates were 1.4% or less in first and second eyes. Posterior capsulotomy rates were 3.4% (first eye) and 2.7% (second eye).

Conclusions:

The study IOL provided good VA outcomes. Defocus curve showed VA of 20/25 Snellen or better from near to intermediate distance. Rates of serious and nonserious AEs were low.

Comparative clinical accuracy analysis of the newly developed ZZ IOL and four existing IOL formulas for post-corneal refractive surgery eyes

BACKGROUND

Intraocular lens (IOL) calculation using traditional formulas for post-corneal refractive surgery eyes can yield inaccurate results. This study aimed to compare the clinical accuracy of the newly developed Zhang & Zheng (ZZ) formula with previously reported IOL formulas.

STUDY DESIGN

Retrospective study.

METHODS

Post-corneal refractive surgery eyes were assessed for IOL power using the ZZ, Haigis-L, Shammas, Barrett True-K (no history), and ray tracing (C.S.O Sirius) IOL formulas, and their accuracy was compared. No pre-refractive surgery information was used in the calculations.

RESULTS

This study included 38 eyes in 26 patients. ZZ IOL yielded a lower arithmetic IOL prediction error (PE) compared with ray tracing (P = 0.04), whereas the other formulas had values like that of ZZ IOL (P > 0.05). The arithmetic IOL PE for the ZZ IOL formula was not significantly different from zero (P = 0.96). ZZ IOL yielded a lower absolute IOL PE compared with Shammas (P < 0.01), Haigis-L (P = 0.02), Barrett true K (P = 0.03), and ray tracing (P < 0.01). The variance of the mean arithmetic IOL PE for ZZ IOL was significantly smaller than those of Shammas (P < 0.01), Haigis-L (P = 0.03), Barrett True K (P = 0.02), and ray tracing (P < 0.01). The percentages of eyes within ± 0.5 D of the target refraction with the ZZ IOL, Shammas, Haigis-L, Barrett True-K, and ray-tracing formulas were 86.8 %, 45.5 %, 66.7 %, 73.7 %, and 50.0 %, respectively (P < 0.05 for Shammas and ray tracing vs. ZZ IOL).

CONCLUSIONS

The ZZ IOL formula might offer superior outcomes for IOL power calculation for post-corneal refractive surgery eyes without prior refractive data.

Assessing the validity of corneal power estimation using conventional keratometry for intraocular lens power calculation in eyes with Fuch's dystrophy undergoing Descemet membrane endothelial keratoplasty

PURPOSE

The present retrospective study was designed to test the hypothesis that the postoperative posterior to preoperative anterior corneal curvature radii (PPPA) ratio in eyes with Fuch's dystrophy undergoing Descemet membrane endothelial keratoplasty (DMEK) is significantly different to the posterior to anterior corneal curvature radii (PA) ratio in virgin eyes and therefore renders conventional keratometry (K) and the corneal power derived by it invalid for intraocular lens (IOL) power calculation.

METHODS

Measurement of corneal parameters was performed using Scheimpflug imaging (Pentacam HR, Oculus, Germany). In 125 eyes with Fuch's dystrophy undergoing DMEK, a fictitious keratometer index was calculated based on the PPPA ratio. The preoperative and postoperative keratometer indices and PA ratios were also determined. Results were compared to those obtained in a control group consisting of 125 eyes without corneal pathologies. Calculated mean ratios and keratometer indices were then used to convert the anterior corneal radius in each eye before DMEK to postoperative posterior and total corneal power. To assess the most appropriate ratio and keratometer index, predicted and measured powers were compared using Bland-Altman plots.

RESULTS

The PPPA ratio determined in eyes with Fuch's dystrophy undergoing DMEK was significantly different (P < 0.001) to the PA ratio in eyes without corneal pathologies. Using the mean PA ratio (0.822) and keratometer index (1.3283), calculated with the control group data to convert the anterior corneal radius before DMEK to power, leads to a significant (P < 0.001) underestimation of postoperative posterior negative corneal power (mean difference (∆ = - 0.14D ± 0.30) and overestimation of total corneal power (∆ = - 0.45D ± 1.08). The lowest prediction errors were found using the geometric mean PPPA ratio (0.806) and corresponding keratometer index (1.3273) to predict the postoperative posterior (∆ = - 0.01 ± 0.30) and total corneal powers (∆ = - 0.32D ± 1.08).

CONCLUSIONS

Corneal power estimation using conventional K for IOL power calculation is invalid in eyes with Fuch's dystrophy undergoing DMEK. To avoid an overestimation of corneal power and minimize the risk of a postoperative hyperopic shift, conventional K for IOL power calculation should be adjusted in eyes with Fuch's dystrophy undergoing cataract surgery combined with DMEK. The fictitious PPPA ratio and keratometer index may guide further IOL power calculation methods to achieve this.

Comparison of intraocular lens calculation methods after myopic laser-assisted in situ keratomileusis and radial keratotomy without prior refractive data

AIM

To compare intraocular lens (IOL) calculation methods not requiring refraction data prior to myopic laser-assisted in situ keratomileusis (LASIK) and radial keratotomy (RK).

METHODS

In post-LASIK eyes, the methods not requiring prior refraction data were Hagis-L; Shammas; Barrett True-K no-history; Wang-Koch-Maloney; 'average', 'minimum' and 'maximum' IOL power on the American Society of Cataract and Refractive Surgeons (ASCRS) IOL calculator. Double-K method and Barrett True-K no-history, 'average', 'minimum' and 'maximum' IOL power on ASCRS IOL calculator were evaluated in post-RK eyes. The predicted IOL power was calculated with each method using the manifest postoperative refraction. Arithmetic and absolute IOL prediction errors (PE) (implanted-predicted IOL powers), variances in arithmetic IOL PE and percentage of eyes within ±0.50 and ±1.00 D of refractive PE were calculated.

RESULTS

Arithmetic or absolute IOL PE were not significantly different between the methods in post-LASIK and post-RK eyes. In post-LASIK eyes, 'average' showed the highest and 'minimum' showed the least variance, whereas 'average' and 'minimum' had highest percentage of eyes within ±0.5 D and 'minimum' had the highest percentage of eyes within ±1.0 D. In the post-RK eyes, 'minimum' had highest variance, and 'average' had the least variance and highest percentage of eyes within ±0.5 D and ±1.0 D.

CONCLUSION

In post-LASIK and post-RK eyes, there are no significant differences in IOL PE between the methods not requiring prior refraction data. 'Minimum' showed least variance in PEs and more chances of eyes to be within ±1.0 D postoperatively in post-LASIK eyes. 'Average' had least variance and more chance of eyes within ±1.0 D in post-RK eyes.

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.

Intraocular lens power calculations in eyes with previous hyperopic laser in situ keratomileusis or photorefractive keratectomy

PURPOSE

To evaluate the accuracy of 7 intraocular lens (IOL) calculation formulas in patients with previous hyperopic laser in situ keratomileusis (LASIK) or excimer laser photorefractive keratectomy (PRK).

DESIGN

Retrospective case series.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA.

METHODS

The 7 formulas evaluated were the adjusted Atlas 0-3, Masket, Modified Masket, Haigis-L, Shammas-PL, Barrett True-K, and Barrett True-K No-History. The Masket and Modified Masket were calculated using the single-K version of Holladay 1 and Hoffer Q formulas; the adjusted Atlas 0-3 was calculated using the double-K version of Holladay 1 and Hoffer Q. The IOL power predicted by each formula was calculated by targeting the postoperative manifest refraction. The IOL prediction error was obtained by subtracting the predicted IOL power from the implanted IOL power. The mean IOL prediction error, median absolute refractive prediction error, and percentages of eyes within ±0.50 diopter (D) and ±1.00 D of the predicted refraction were calculated.

RESULTS

Twenty-one eyes of 21 patients were evaluated. There were no significant differences in the median absolute refractive prediction error or percentages of eyes within ±0.50 D or ±1.00 D of the predicted refraction between formulas or methods. The IOL mean prediction errors were comparable between the Holladay 1 and Hoffer Q calculations for all formulas except for a greater error for the double-K version of the Hoffer Q of the adjusted Atlas 0-3.

CONCLUSION

In eyes that had hyperopic LASIK or PRK, there were no significant differences in the accuracy between the 7 IOL calculation formulas.

Methods for Intraocular Lens Power Calculation in Cataract Surgery after Radial Keratotomy

PURPOSE

To compare methods of calculating the required intraocular lens (IOL) power for patients undergoing cataract surgery after radial keratotomy (RK), including the 2016 update of the True K formula.

DESIGN

Retrospective case series.

PARTICIPANTS

A total of 52 eyes of 34 patients who had sequential RK and cataract surgery performed in the same institution by 1 of 2 surgeons.

METHODS

Seven IOL calculation formulae were evaluated: True K [History], True K [Partial History], True K [No History], Double-K Holladay 1 (DK-Holladay-IOLM), Potvin-Hill, Haigis, and Haigis with a -0.50 diopter (D) offset. Biometry was obtained with the IOLMaster 500 (Carl Zeiss Meditec AG, Jena, Germany) and Pentacam (OCULUS Inc, Arlington, WA) devices. Subjective refraction was performed at 4 to 6 weeks postoperatively. The achieved spherical equivalent outcome was compared with the target outcome to calculate the absolute error for each eye with each formula.

MAIN OUTCOME MEASURES

Median absolute error (MedAE) and mean absolute error (MAE), and percentage of patients within ±0.50 D, ±0.75 D, and ±1.00 D of refractive target. Mean error (ME) was also calculated to demonstrate whether a formula tended toward more myopic or hyperopic outcomes.

RESULTS

Best results were achieved with the True K [History]. The MedAE was higher (0.382 vs. 0.275) with the True K [Partial History], but a similar percentage of patients (75.0%-76.6%) achieved within ±0.50 D of target. Of the methods that do not require refractive history, the True K [No History] and unadjusted Haigis were most accurate (69.2% within ±0.50 D of target), with the True K [No History] returning the lowest MedAE but also more of a tendency toward hyperopia (ME +0.269 vs. -0.006 for Haigis). The DK-Holladay-IOLM and Potvin-Hill methods were the least accurate.

CONCLUSIONS

Knowledge of the refractive history significantly improves the accuracy of IOL calculations in patients undergoing cataract surgery after previous RK. The post-RK refraction appears to be the most important parameter, with inclusion of the pre-RK refraction offering a further slight improvement in MedAE. When no refractive history is available, the True K [No History] and Haigis formulae both perform well, with the added advantage of not requiring data from separate biometric devices.

Evaluation of total keratometry and its accuracy for intraocular lens power calculation in eyes after corneal refractive surgery

PURPOSE

To compare the accuracy of total keratometry (TK) and standard keratometry (K) from a swept-source optical coherence tomography biometer for intraocular lens (IOL) power calculation in eyes with previous corneal refractive surgery.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

DESIGN

Retrospective case series.

METHODS

The differences between the TK and K and their association with K were assessed. For IOL power calculation, combinations of 1) K with Haigis, Haigis-L, and Barrett True-K, and 2) TK with Haigis (Haigis-TK) were used. The mean absolute error (MAE) and the percentages of eyes within prediction errors of ± 0.50 diopters (D), ± 1.00 D, and ± 2.00 D were calculated.

RESULTS

The study comprised 129 eyes. For Haigis, Haigis-L, Barrett True-K, and Haigis-TK, respectively, the MAEs were 0.72 D, 0.61 D, 0.54 D, and 0.50 D in the myopic laser in situ keratomileusis (LASIK)/photorefractive keratectomy (PRK) group, and 0.74 D, 0.68 D, 0.71 D, and 0.70 D in hyperopic LASIK/PRK group. For the radial keratotomy (RK) eyes, the MAEs were 0.66 D, 0.71 D, and 0.72 D for the Haigis, Barrett True-K, and Haigis-TK formulas, respectively. In the myopic LASIK/PRK group, the Barrett True-K and Haigis-TK produced significantly lower MAEs than did Haigis (P < .05). In the hyperopic LASIK/PRK and RK groups, there were no significant differences between the formulas in MAEs and percentages of eyes within the above prediction errors.

CONCLUSIONS

The performance of the combination of Haigis and TK in refractive prediction was comparable with Haigis-L and Barrett True-K in eyes with previous corneal refractive surgery.

Extended depth of focus lens implantation after radial keratotomy

Purpose

To identify the visual performance of radial keratotomy (RK) patients that have undergone cataract surgery with implantation of an extended depth of focus (EDOF) intraocular lens (IOL).

Design

Retrospective chart review with questionnaire.

Methods

Medical charts of patients with a history of RK that had undergone phacoemulsification with implantation of the Tecnis Symfony IOL (J&J Vision) were reviewed. Data collected included preoperative demographics, number of RK incisions, pupil size, and preoperative visual acuity and manifest refraction. Primary outcome measures of the study included postoperative uncorrected distance visual acuity (UCVA) and manifest refraction spherical equivalent (SE) at each follow-up visit. Secondary outcomes included results from a telephone questionnaire assessing visual performance and satisfaction.

Results

Twenty-four eyes of 12 patients were included. UCVA improved from an average Snellen equivalent 20/73 preoperatively to 20/33 at an average final follow-up of 6 months (P=0.0011), while average manifest SE improved from +1.68 D to −0.18 D (P<0.0001). At final follow-up, 15 of 24 eyes (62.5%) were at or within 0.5 D of target refraction, while 20 of 24 eyes (83.3%) were at or within 1.0 D. In total, 79% of eyes (19 of 24) had UCVA of 20/40 or better at distance. In the survey, 78% of patients reported satisfaction with their vision after surgery and 44% of patients reported being spectacle free for all tasks.

Conclusions

An EDOF lens implant can produce good visual outcomes and satisfaction in patients with a history of RK.

[Photorefractive Keratectomy (PRK) as a Procedure for Correction of Residual Refractive Errors after Radial Keratotomy]

BACKGROUND

A large number of myopic patients were treated by radial keratotomy (RK) in recent years. Despite being effective in many cases, the refractive results of this surgical intervention proved to be of limited predictability, and it frequently resulted in over- or under-correction in the long term. In this study, we discuss the intermediate and long-term results of a topography-guided photorefractive keratotomy (PRK) in a consecutive series of patients who were previously treated for myopia by radial keratotomy.

MATERIALS AND METHODS

In this retrospective case series, we examined the refraction and visual acuity in a consecutive series of patients-16 eyes-who were treated by PRK for residual refractive errors after radial keratotomy in the past. Mean follow up was 41 months (min. 9, max. 96).

RESULTS

All treated eyes showed an improvement in uncorrected visual acuity, and 56% had an improvement in corrected visual acuity. No serious or sight-threatening complications were recorded. Refraction was stable throughout the study period in all patients.

CONCLUSIONS

In this case series, photorefractive keratotomy was shown to be an effective treatment method for secondary ametropia after radial keratotomy. Apart from the correct planning and execution of the PRK, it is of critical importance to inform the patients about the limitations and the anticipated refractive result of the procedure.

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.

Refractive correction with multifocal intraocular lenses after radial keratotomy

PURPOSE

To assess visual and refractive results of multifocal intraocular lens (IOLs) implantation for refractive correction after radial keratotomy (RK).

METHODS

In a retrospective non-comparative interventional case series, we analyzed the outcomes of multifocal IOL implantation performed in the context of cataract or refractive lens exchange surgery following RK. A total of 17 eyes from nine patients were included in the study. IOL power calculation was done using the Double-K formula. Refractive error was used to assess predictability, and distance-corrected visual acuity (DCVA) and uncorrected distance visual acuity (UDVA) values were used to assess the surgical procedure's efficacy and safety. Distance-corrected near visual acuity (DCNVA) was also determined.

RESULTS

Phacoemulsification and multifocal IOL implantation was successful in all cases, with neither complications nor adverse events. At 6 months postoperatively, monocular UDVA, DCVA, and DCNVA were 0.51 ± 0.39, 0.20 ± 0.30, and 0.11 ± 0.11, respectively (logMAR scale). More specifically, 35.29% of the eyes had DCVA ≥20/20 and 52.94% showed DCVA ≥20/25. Regarding pre- vs. post-operative changes, 52.94% had lost one line of DCVA, 23.53% showed no changes, 11.76% had gained one line of DCVA, 5.88% had gained two lines, and 5.88% had gained three or more lines. The efficacy and safety indexes were 0.56 and 0.98, respectively. As for near vision surgical outcomes, 29.41% of the eyes had DCNVA ≥20/20 and 64.71% had DCNVA ≥20/25. As for surgical accuracy, 29% of the eyes were within ±0.50 D of the target refraction, whereas 65% were within ±1.00 D.

CONCLUSIONS

Multifocal IOL implantation following radial keratotomy (RK) does not result in good distance visual performance, at least after 6 months of follow-up. Thus, this surgical approach has to be considered with only limited expectations.

Intraocular lens power calculation in eyes with previous corneal refractive surgery

Background

This review aims to explain the reasons why intraocular lens (IOL) power calculation is challenging in eyes with previous corneal refractive surgery and what solutions are currently available to obtain more accurate results.

Review

After IOL implantation in eyes with previous LASIK, PRK or RK, a refractive surprise can occur because i) the altered ratio between the anterior and posterior corneal surface makes the keratometric index invalid; ii) the corneal curvature radius is measured out of the optical zone; and iii) the effective lens position is erroneously predicted if such a prediction is based on the post-refractive surgery corneal curvature. Different methods are currently available to obtain the best refractive outcomes in these eyes, even when the perioperative data (i.e. preoperative corneal power and surgically induced refractive change) are not known. In this review, we describe the most accurate methods based on our clinical studies.

Conclusions

IOL power calculation after myopic corneal refractive surgery can be calculated with a variety of methods that lead to relatively accurate outcomes, with 60 to 70% of eyes showing a prediction error within 0.50 diopters.

Intraocular Lens Power Calculation in Eyes After Laser In Situ Keratomileusis or Photorefractive Keratectomy for Myopia

Intraocular power calculation is challenging for patients who have previously undergone corneal refractive surgery. The sources of prediction errors for these eyes are well known; however, the numerous formulas and methods available for calculating intraocular lens power in these cases are eloquent testimony to the absence of a definitive solution. This review discusses some of the available methods for improving the accuracy for predicting the refractive outcome for these patients. It focuses mainly on the methods available on the American Society of Cataract and Refractive Surgery (ASCRS) online calculator and provides some practical guidelines for cataract surgeons who encounter these challenging cases.

Comparison of Newer IOL Power Calculation Methods for Eyes With Previous Radial Keratotomy

Purpose

To evaluate the accuracy of the optical coherence tomography–based (OCT formula) and Barrett True K (True K) intraocular lens (IOL) calculation formulas in eyes with previous radial keratotomy (RK).

Methods

In 95 eyes of 65 patients, using the actual refraction following cataract surgery as target refraction, the predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the implanted IOL power. The arithmetic IOL PE and median refractive PE were calculated and compared.

Results

All formulas except the True K produced hyperopic IOL PEs at 1 month, which decreased at ≥4 months (all P < 0.05). For the double-K Holladay 1, OCT formula, True K, and average of these three formulas (Average), the median absolute refractive PEs were, respectively, 0.78 diopters (D), 0.74 D, 0.60 D, and 0.59 D at 1 month; 0.69 D, 0.77 D, 0.77 D, and 0.61 D at 2 to 3 months; and 0.34 D, 0.65 D, 0.69 D, and 0.46 D at ≥4 months. The Average produced significantly smaller refractive PE than did the double-K Holladay 1 at 1 month (P < 0.05). There were no significant differences in refractive PEs among formulas at 4 months.

Conclusions

The OCT formula and True K were comparable to the double-K Holladay 1 method on the ASCRS (American Society of Cataract and Refractive Surgery) calculator. The Average IOL power on the ASCRS calculator may be considered when selecting the IOL power. Further improvements in the accuracy of IOL power calculation in RK eyes are desirable.

Modification of the wound construction to prevent dehiscence of radial keratotomy incision in cataract surgery: Wave-shaped scleral incision

We describe a modified scleral tunnel incision to provide adequate fracture resistance and maneuverability during manipulations in cataract surgery after radial keratotomy (RK) surgery. In cases without sufficient space between the RK incisions to create a corneal incision, the modified incision can be performed. A scleral groove of one-half scleral thickness is made 3.0 mm posterior to the limbus. The groove circumvents the end of the preexisting RK incision at the limbus. To prevent the incisional edge from sagging, the ends of the external incision are swept up slightly, forming a wave-shaped edge. After horizontal lamellar dissection, the wound construction is completed with a steel keratome. The modified incision was performed in 3 cases after RK surgery. The method prevented dehiscence of the RK incision and provided fracture resistance and maneuverability.

The Enigmatic Cornea and Intraocular Lens Calculations: The LXXIII Edward Jackson Memorial Lecture

PURPOSE

To review the progress and challenges in obtaining accurate corneal power measurements for intraocular lens (IOL) calculations.

DESIGN

Personal perspective, review of literature, case presentations, and personal data.

METHODS

Through literature review findings, case presentations, and data from the author's center, the types of corneal measurement errors that can occur in IOL calculation are categorized and described, along with discussion of future options to improve accuracy.

RESULTS

Advances in IOL calculation technology and formulas have greatly increased the accuracy of IOL calculations. Recent reports suggest that over 90% of normal eyes implanted with IOLs may achieve accuracy to within 0.5 diopter (D) of the refractive target. Though errors in estimation of corneal power can cause IOL calculation errors in eyes with normal corneas, greater difficulties in measuring corneal power are encountered in eyes with diseased, scarred, and postsurgical corneas. For these corneas, problematic issues are quantifying anterior corneal power and measuring posterior corneal power and astigmatism. Results in these eyes are improving, but 2 examples illustrate current limitations: (1) spherical accuracy within 0.5 D is achieved in only 70% of eyes with post-refractive surgery corneas, and (2) astigmatism accuracy within 0.5 D is achieved in only 80% of eyes implanted with toric IOLs.

CONCLUSION

Corneal power measurements are a major source of error in IOL calculations. New corneal imaging technology and IOL calculation formulas have improved outcomes and hold the promise of ongoing progress.

Comparison of Newer Intraocular Lens Power Calculation Methods for Eyes after Corneal Refractive Surgery

PURPOSE

To compare the newer formulae, the optical coherence tomography (OCT)-based intraocular lens (IOL) power formula (OCT formula) and the Barrett True-K formula (True-K), with the methods on the American Society of Cataract and Refractive Surgery (ASCRS) calculator in eyes with previous myopic LASIK/photorefractive keratectomy (PRK).

DESIGN

Prospective case series.

PARTICIPANTS

A total of 104 eyes of 80 patients who had previous myopic LASIK/PRK and subsequent cataract surgery and IOL implantation.

METHODS

By using the actual refraction after cataract surgery as target refraction, predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the power of the IOL implanted.

MAIN OUTCOME MEASURES

Arithmetic IOL PEs, variances of mean arithmetic IOL PE, median refractive PE, and percent of eyes within 0.5 diopters (D) and 1.0 D of refractive PE.

RESULTS

Optical coherence tomography produced smaller variance of IOL PE than did Wang-Koch-Maloney (WKM) and Shammas (P < 0.05). With the OCT, True-K No History, WKM, Shammas, Haigis-L, and Average of these 5 formulas, the median refractive PEs were 0.35 D, 0.42 D, 0.51 D, 0.48 D, 0.39 D, and 0.35 D, respectively, the percentage of eyes within 0.5 D of refractive PE were 68.3%, 58.7%, 50.0%, 52.9%, 55.8%, and 67.3%, respectively, and the percentage of eyes within 1.0 D of refractive PE were 92.3%, 90.4%, 86.9%, 88.5%, 90.4%, and 94.2%, respectively. The OCT formula had smaller refractive PE compared with the WKM and Shammas, and the Average approach produced significantly smaller refractive PE than all methods except OCT (all P < 0.05).

CONCLUSIONS

The OCT and True-K No History are promising formulas. The ASCRS IOL calculator has been updated to include the OCT and Barrett True K formulas.

TRIAL REGISTRATION

Intraocular Lens Power Calculation After Laser Refractive Surgery Based on Optical Coherence Tomography (OCT IOL); Identifier: NCT00532051; www.ClinicalTrials.gov.

Intraocular Lens Power Selection after Radial Keratotomy: Topography, Manual, and IOLMaster Keratometry Results Using Haigis Formulas

PURPOSE

To compare final spherical equivalent (SE) refractions in patients who previously underwent radial keratotomy (RK) undergoing routine cataract surgery using keratometry (K) values from the Tomey (Topographic Modeling System [TMS]; Tomey Corp., Phoenix, AZ) Placido topographer, manual keratometer, and IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) keratometer using the Haigis formulas.

DESIGN

Retrospective case series.

SUBJECTS

A total of 26 RK eyes (20 patients) with a minimum of 3 months postoperative follow-up.

METHODS

The following K values were evaluated: TMS topography (flattest K within first 9 rings, average K, minimum K), manual K, IOLMaster K. The final refractive goal was -0.50 diopters (D) for all eyes. The Haigis formula with target refraction -0.50 D was used. In addition, because of observed hyperopic overcorrections, IOLMaster K with the Haigis formula set to -1.00 D but with a final refractive goal of -0.50 D was also tested. The Haigis-L formula using IOLMaster K values was separately evaluated.

MAIN OUTCOME MEASURES

Mean final SE refraction, percent final SE within ideal (-0.12 to -1.00 D), acceptable (0.25 to -1.50 D), or unacceptable (<-1.50 or >0.25 D) range and within ±0.50 D and ±1.00 D of the intended result.

RESULTS

Best results with minimal overcorrections were achieved with TMS flattest K (mean -0.68±0.60 D, 73% within ±0.50 D, and 88% within ±1.00 D of the surgical goal) and IOLMaster K set for target -1.00 D (mean -0.66±0.61 D, 69% within ±0.50 D, and 88% within ±1.00 D of the surgical goal). Other values produced more hyperopic (manual, IOLMaster K set for target -0.50 D, average topography) or higher myopic (minimum topography, Haigis-L) results.

CONCLUSIONS

For simplicity, using the IOLMaster K values combined with the Haigis formula set for target refraction -1.00 D produces acceptable results aiming for -0.50 D final SE refractions in former RK patients undergoing routine cataract surgery.

Spectacle Independence after Cataract Extraction in Post-Radial Keratotomy Patients Using Hybrid Monovision with ReSTOR(®) Multifocal and TECNIS(®) Monofocal Intraocular Lenses

Background

We report 2 patients who have undergone radial keratotomy (RK) preceding ReSTOR^® multifocal intraocular lens (IOL; Alcon, Fort Worth, Tex., USA) implantation in their nondominant eyes and TECNIS^® monofocal IOL (Abbott Medical Optics, Abbott Park, Ill., USA) in their dominant eyes.

Methods

Retrospective review of 2 patients who underwent hybrid monovision with ReSTOR^® multifocal and TECHNIS^® monofocal IOLs at the time of cataract surgery after a remote history of RK.

Results

Implantation of the ReSTOR^® multifocal and the TECHNIS^® monofocal IOLs was successful, with no reported adverse events. The patients were able to achieve spectacle freedom.

Conclusion

We report a novel technique for the management of post-RK patients to optimize their chances for spectacle independence.

A new central-peripheral corneal curvature method for intraocular lens power calculation after excimer laser refractive surgery

PURPOSE

To propose the central-peripheral (C-P) method, which requires no data history to calculate intraocular lens (IOL) powers for eyes that underwent laser in situ keratomileusis (LASIK), and compare the accuracy of the C-P method with other IOL formulas for eyes after LASIK.

METHODS

Sixteen patients with cataract (25 eyes) who underwent myopic LASIK were analysed retrospectively. The C-P method is a modified double-K method using the SRK/T formula, in which the estimated pre-LASIK keratometric power calculated from the post-LASIK peripheral anterior sagittal power (also called the axial power) is used for the Kpre in the double-K method using the SRK/T formula, and the post-LASIK anterior sagittal power is used for the Kpost. We compared the accuracy of the C-P method with other popular IOL calculation formulas for use in eyes after LASIK.

RESULTS

The median values of the arithmetic and absolute prediction errors with the C-P method were 0.11 diopter (D) (range, -1.67 to 1.97 D) and 0.55 D (range, 0.02-1.97 D), respectively. The prediction error using the C-P method was within ±0.5 D in 48% of eyes, within -1.0 to +0.5 D in 60% of eyes, and within ±1.0 D in 68% of eyes. The C-P method resulted in a significantly higher percentage of eyes within ±0.5 D than the BESSt formula, Shammas-PL formula, true net power method, double-K method using 43.5 D for Kpre, and Feiz-Mannis method.

CONCLUSION

The C-P method may be a good option for calculating IOL powers in eyes undergoing cataract surgery after LASIK when the preoperative LASIK data are unavailable.

New algorithm for post-radial keratotomy intraocular lens power calculations based on rotating Scheimpflug camera data

PURPOSE

To provide an algorithm to calculate intraocular lens (IOL) power for post-radial keratometry (RK) eyes based on data extracted from the Pentacam Scheimpflug camera and to compare calculations with those from an existing standard.

SETTING

Private practice, Mesa, Arizona.

DESIGN

Case series.

METHODS

Relevant IOL calculation and postoperative refractive data were obtained for eyes that had previous RK but no additional keratorefractive procedures or subsequent cataract surgery. Various Scheimpflug measurements from examinations before cataract surgery over a range of zone diameters were used to calculate IOL power using an Aramberri double-K-modified Holladay 1 formula. Results were compared with actual postsurgical data and IOL calculations based on the mean of the 1.0 mm to 4.0 mm rings from the Atlas topography system.

RESULTS

Data were obtained for 83 eyes of 57 patients, including more than 120 different measures per eye from the Scheimpflug system. The mean pupil-centered sagittal front power over the central 4.0 mm zone provided the best results after adjustment for central corneal thickness (CCT). Results were similar to those obtained when the IOL power was calculated using the topography system; 42% of eyes were within ± 0.50 diopter (D) of the target, and 76% of eyes were within ± 1.00 D.

CONCLUSION

In this large series of eyes, the calculation of IOL power after RK using sagittal front-surface power and CCT from the Scheimpflug system produced results equivalent to the multizone approach with the topography system.

Orbscan II and double-K method for IOL calculation after refractive surgery

BACKGROUND

Precise IOL calculation in post-refractive surgery patients is still a challenge for the cataract surgeon. The purpose of this study is to test whether adding Orbscan II values into the double-K method improves IOL calculation in this group of patients.

METHODS

A prospective study with 43 eyes previously submitted to refractive surgery that underwent cataract extraction. IOL calculation was performed with double-K method. Post-K value was derived from Orbscan total-mean power map. The average corneal curvature of the general population (43.8D) was used as the pre-K value. Refraction results 30 days after surgery were compared with refraction that would be obtained if we used: (1) post-K values from keratometry, (2) post-K values from topography, and (3) pre-K values from Orbscan total-mean power. Anterior chamber depth measures obtained with the IOL Master and Orbscan II were compared.

RESULTS

Mean postoperative spherical equivalent (SE) was -0.25 ± 1.10 D in eyes submitted to radial keratotomy , -1.04 ± 1.42 D in eyes previously submitted to myopic Lasik, and +0.05 ± 1.76 D in those submitted to hyperopic surgeries. Had we inputted post-K values derived from keratometer and from topography, we would have obtained significantly higher postoperative refractive errors in eyes previously submitted to myopic refractive surgery (p < 0.05). Refractions using pre-K derived from the central 8 mm Orbscan instead of 43.8 D were similar in all studied groups (p > 0.05). Anterior chamber depth measured with IOL Master or Orbscan were similar.

CONCLUSIONS

Orbscan measurements used as the post-K values into the double-K method provide a precise IOL calculation, especially in post myopic refractive surgery patients.