Comparison of formulas and methods for high myopia patients requiring intraocular lens powers less than six diopters.

PURPOSE: To determine the best method to minimize postoperative hyperopia and achieve mild myopia in patients requiring low-powered (<6.00 D) MN60MA intraocular lenses (IOLs). METHODS: This retrospective non-comparative case series consists of 32 eyes (20 patients). Postoperative spherical equivalent (SE) refractions were compared using four methods: standard formulas with varying target refractions (Haigis -1.00 D, Hoffer Q -1.75 D, Holladay 1 -1.50 D and SRK/T -1.00 and -1.25 D), axial length adjustment methods for standard formulas targeted for both plano and -0.50 D, Barrett Universal II formula and the Haigis formula using separate constants for plus and minus IOLs (Haigis +/-). SE (mean, standard deviation, median, range), median absolute error (MedAE), prediction errors, percentage SE less than 0.25 D and greater than -1.00 D, percentage SE within ±0.50 and ±1.00 D of the targeted refraction were calculated. RESULTS: All methods and formulas gave acceptable mean SE refractions ranging from -0.04 to -0.68 D. The Barrett Universal II, Haigis +/-, standard Haigis formula targeted for -1.00 D and the Holladay 1 formula targeted for -1.50 D met stricter criteria of final SE between 0.25 and -1.00 D in 94-100% of eyes and MedAE between 0.37 and 0.51 D. Other methods had more myopic or hyperopic outliers. CONCLUSIONS: For these eyes with high myopia, the Barrett Universal II, Haigis +/-, standard Haigis targeted for -1.00 D and the standard Holladay 1 targeted for -1.50 D formulas produce the best results exceeding established benchmark criteria and minimizing hyperopic surprises.

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.

Intraocular lens power adjustment after myopic excimer laser surgery: validation studies for Geggel ratio and consensus group.

PURPOSE: To validate the Geggel ratio (GR) and consensus group in myopic excimer laser patients undergoing cataract surgery. METHODS: Two separate consecutively collected case series (group 1, 32 eyes; group 2, 34 eyes) were retrospectively analyzed. Data from group 1 was used to generate a new linear regression formula for the GR based on the Haigis formula. Predicted implant powers based on the Shammas, Latkany, Savini, Seitz, Haigis-L, and GR based on either SRK/T or Haigis formulas and combined consensus methods were computed. Mean error, range, percent within ± 0.5 D, ± 1.0 D and -1.0/+0.5 D were calculated. RESULTS: In group 1, the original GR (SRK/T) formula produced higher mean values (-0.44 D) and lower percentage within ± 0.5 D (41%) compared with the other 5 formulas (-0.03 to -0.33 D; 65%-82%). A linear regression formula (-0.142*ΔSE +0.2) for the GR was derived as a correction factor added to the Haigis formula. Group 2 validated the 5 formulas again plus the GR (Haigis). All group 2 formulas gave excellent results with means ranging from -0.18 to -0.37 D, percentages with ± 0.5 D ranging from 55% to 78%, and percentages within -1.0/+0.5 D ranging from 85% to 100%. Consensus formulas produced mean error -0.30 D, 70% ± 0.5 D, 93% -1.0/+0.5 D with only 2 outliers at 0.6 D and -1.1 D. CONCLUSIONS: These six methods achieve high levels of IOL accuracy. The GR method works better based on the Haigis formula. Consensus calculations minimize both under- and overcorrections.

Pachymetric ratio no-history method for intraocular lens power adjustment after excimer laser refractive surgery.

OBJECTIVE: To evaluate a new pachymetric method not requiring pre-refractive surgical data for adjusting the intraocular lens (IOL) power in eyes undergoing cataract surgery after excimer laser refractive surgery and comparing final refractive results with previously published formulas or methods. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Thirty-six eyes from 23 patients who had uneventful phacoemulsification cataract surgery after previous myopic (35) or mixed astigmatism (1) excimer laser photoablation. METHODS: A new corneal ratio (Geggel ratio) method was developed to estimate the diopters (D) of previous excimer treatment or change in spherical equivalent (SE) at the corneal plane. A regression formula, 0.40 (|DeltaSE|-1), predicted the correction factor to be added to the SRK/T (Sanders, Retzlaff, Kraff) formula. The IOL results from the Geggel and Geggel-real (modified for mild myopia) method were compared with the Masket, Koch double K table, Ladas, Walter, modified Maloney, clinical history, Feiz standardized and nomogram, Latkany average and flat, Ferrara, Rosa, Savini, Jin, Shammas no-history and regression formula, Seitz, and Awwad methods. The SRK/T, Hoffer, and Holladay formulas were tested in appropriate formulas. All IOL powers were converted to refractive results using IOL(exact) equations. MAIN OUTCOME MEASURES: Mean +/- standard deviation (SD), range, absolute mean +/- SD, and percent within +/-0.5 D, +/-1.0 D, and -1.0/+0.5 D. RESULTS: The pachymetric technique minimizes hyperopic surprises with 92% of eyes within -1.0/+0.5 D and no overcorrections >0.5 D with the Geggel-real modification. Final refractive results with the Geggel, Geggel-real, Masket, Koch double K tables, Latkany average and flat, Savini, Shammas no-history, Seitz Holladay, Seitz Hoffer, and Awwad Hoffer all had >55% SE +/-0.5 D and >85% SE +/-1.0 D of the surgical goal. The best results with fewer hyperopic overcorrections were found in 5 methods that comprise a new consensus group: Geggel-real, Shammas no-history, Savini, Latkany flat, and Seitz Hoffer. The consensus group had 96% of eyes within -1.0/+0.5 D of the surgical goal. CONCLUSIONS: The Geggel-real method is a new approach requiring no historical data to determine IOL power in this ever-enlarging and challenging group of former refractive surgery patients undergoing routine cataract surgery. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Arcuate relaxing incisions guided by corneal topography for postkeratoplasty astigmatism: vector and topographic analysis.

PURPOSE: To determine if using corneal topography for planning arcuate relaxing incision placement for postkeratoplasty astigmatism improves clinical results. METHODS: Twenty-six eyes with high levels (> 5 diopters [D]) of postkeratoplasty astigmatism were studied in a nonrandomized, retrospective, observational case series. Relaxing incisions were placed in the peripheral graft in each steep topographic hemimeridian. The following data were measured: keratometric, topographic, and refractive vector analysis; nonvector astigmatism reduction; surface regularity and asymmetry (surface regularity index and surface asymmetry index); topography patterns; surgical design; and visual acuity. RESULTS: Topographic analysis changed some aspect of the surgery in 51/52 incisions with a 15.7 degrees mean change in incision location. The mean vector correction index (CI) was 0.89 to 0.92 for keratometric, topographic, and refractive indices. Sixty-five percent of eyes had surgically induced astigmatism (SIA) values within 2 D of the surgical goal. Eighty-one percent of eyes had at least a 50% reduction in net astigmatism and 85% had < or = 3-D residual refractive cylinder. The mean logMAR visual acuity increased 2 lines. The preoperative and postoperative spherical equivalent showed a high correlation (rho = 0.914, P = 0.000). The correlation between SIA and targeted induced astigmatism (TIA) was 0.56 (P = 0.003). There was a significant improvement in surface regularity index (P = 0.000) and surface asymmetry index (P = 0.05) values. No statistically significant correlations were found between total incision length and SIA or TIA, or between TIA and correction index. All patients had symmetric (58%) or asymmetric (42%) bowtie topographic patterns preoperatively with 35% achieving round/oval patterns postoperatively. CONCLUSIONS: Topography-guided relaxing incision offers an easy method to plan surgery and has some limited advantages over conventional techniques.

Technique to minimize asymmetric suture placement during penetrating keratoplasty.

PURPOSE: Surgeons must mark the donor and recipient tissues precisely during penetrating keratoplasty, and verify the correct position of these marks in the actual donor button and trephine sites to minimize asymmetric placement of the graft within the host wound. METHODS: A unique surgical reticule has been developed that simplifies proper marking of both the donor and recipient tissues with gentian violet. The reticule is placed within the oculars of the operating microscope. The circumference of the donor tissue and partial-thickness trephined host wound are aligned with a 5 mm inscribed circle. Eight equidistant lines, separated by 45 degrees around the circle, are used to place marks on the donor tissue and confirm the correct peripheral placement of limbal lines on the host tissue. The surgeon uses these landmarks for cardinal suture placement. RESULTS: The reticule is easy to use with any size of trephine, and does not interfere with other surgical maneuvers during surgery. CONCLUSIONS: Correct suturing of the first eight cardinal sutures can occur only if the donor button is marked after it has been prepared, and the location of the recipient marks are verified after the actual trephination impression has been made. This reticule should minimize the role of asymmetric suturing on final graft astigmatism.