Donald R. Sanders

Comparison of the SRK/T formula and other theoretical and regression formulas

ABSTRACT We compared the predictive accuracy of the SRK/T formula to the SRK II, Binkhorst H, Hoffer, and Holladay formulas in seven series of cases totaling 1,050 eyes. In the combined group, the SRK/T and Holladay formulas performed only slightly better than the other formulas. In short eyes (< 22 mm), all formulas performed well, with the SRK/T, SRK II, and Holladay formulas performing marginally better. In moderately long eyes (> 24.5 mm, ≤ 27 mm), the Hoffer and Binkhorst II formulas had a greater proportion of cases with > 2 diopters (D) of error and the SRK/T and Holladay were again marginally better. In the very long eyes (> 27 mm and < 28.4 mm), there were only 11 cases and all formulas performed well since none had > 2 D of prediction error. In an extremely long eye data set (> 28.4 mm), the SRK II formula clearly gave the poorest result. Eyes of this length occurred in only 0.1% of cases in our unselected series. Results support the contention that the present second and third generation IOL power formulas give fairly equivalent accuracy Other factors, such as availability, ease of use, and ability to tailor or individualize, become major considerations.

Improvement of intraocular lens power calculation using empirical data

A simple lens power calculation formula of the form: Predicted implant power = A + B X axial length + C X keratometry, can be produced with different constants (A, B, and C) for each type of lens implant and each manufacturer. We have determined the constants for iris-fixated, anterior chamber and posterior chamber lens implants, based on data from 923 cases. The results have been more accurate than those from presently available theoretical formulas, and the well-known phenomenon of predicting too much dioptric power in eyes with short axial lengths has been avoided. Only 1% of the cases had a predicted lens power more than 3 diopters in error.

Prophylaxis of Pseudophakic Cystoid Macular Edema with Topical Indomethacin

A prospective double-masked study of 500 patients was performed to assess the effect of topical indomethacin on the angiographic incidence of cystoid macular edema (CME) in patients undergoing intraocular lens implant surgery. All patients received either topical indomethacin or placebo before surgery and for nine months after surgery. All patients underwent planned extracapsular extraction (PEC) or posterior chamber phacoemulsification (PC-KPE). Implantation of a posterior chamber lens and a primary capsulotomy were performed in all cases. All cases received postoperative topical corticosteroids. Of the 500 cases, 390 (78%) underwent fluorescein angiography; most were performed between 2 1/2 and 5 months after surgery. The incidence of angiographically confirmed CME was significantly higher in the placebo-treated patients as compared to those treated with indomethacin (18.5% vs 9.6%; P = 0.04). Patients 60 years of age or older had a significantly higher incidence of CME than younger individuals (15% vs. 3.4%; P = 0.03). When corrected for the effects of drug regimen and age, by means of multiple logistic regression, there was no significant correlation between procedure (PEC vs. PC-KPE) and CME rate (P = 0.62). There was no significant difference in postoperative visual acuity between the indomethacin- and placebo-treated patients (P = 0.65).

Implantable contact lens for moderate to high myopia: Phase 1 FDA clinical study with 6 month follow-up

Purpose: To assess the short‐term safety and efficacy of the implantable contact lens (ICL™) to treat, moderate to high myopia, Setting: Phase 1 U.S. Food and Drug Administration clinical study of the ICL conducted at four sites in the United States. Methods: Ten patients with myopia of 7,00 diopters (D) or greater had implantation of a Staar Surgical ICL and were examined preoperatively (baseline) and 1 day, 1 week, and 1, 3, and 6 months postoperatively. Mean preoperative myopia was 7.75 D (range 7.25 to 9.37 D): Results: Six months postoperatively, 5 of 10 eyes (50%) had an uncorrected visual acuity (UCVA) of 20/20 or better, and all eyes had a UCVA of 20/30 or better. All eyes had a best spectacle‐corrected visual acuity (BSCVA), of 20/20 or better and 6 eyes (60%), of 20/15 or better. Six eyes (60%) had an improvement of one or more lines of BSCVA. Mean postoperative spherical equivalent was −0.025 D ± 0.47 (SD). Eight eyes (80%) were within ±0.250 D of emmetropia, and all were within ±1.125 D. No intraoperative or postoperative complications or adverse reactions were observed. Conclusions: The results support the short‐term safety, efficacy; and predictability of ICL implantation to treat moderate to high myopia.

Incidence of lens opacities and clinically significant cataracts with the implantable contact lens: comparison of two lens designs.

PURPOSE To compare the incidence of anterior subcapsular lens opacities, clinically significant cataracts, secondary lens-related surgical reinterventions, and vaulting characteristics of the now discontinued V3 and currently used V4 Staar Surgical Implantable Contact Lens (ICL) phakic intraocular lens designs. METHODS In this non-randomized prospective clinical trial, 87 eyes were implanted with the V3 and 523 eyes with the V4 ICL as part of the U.S. FDA clinical trial for myopia. LOCS III assessment of lens opacities, clinically significant cataract, ICL vaulting (clearance between ICL and crystalline lens), and secondary ICL-related surgeries were the main outcome measures. Mean follow-up in the V3 series was 30.7 +/- 10.0 months (range 10.8 to 49.3 mo) and in the V4 series, 17.3 +/- 6.9 months (range 0.25 to 38.5 mo). RESULTS Incidence of anterior subcapsular opacities was significantly higher with the V3 vs. V4 ICL (12.6% vs. 2.9%, P<.001). The difference was largely due to the higher rate of late-appearing opacities (> or = 1 year after surgery; 9.2% vs. 0.6%, P<.001). The V3 group had a greater proportion of eyes with poor vault (23.6% vs. 4.3%, P<.001) and the presence of poor vault was highly associated with the development of late anterior subcapsular opacities (P<.001). Clinically significant cataract was more frequent in the V3 vs. V4 ICL (9.2% vs. 0.8%, P<.001), as was cataract extraction (6.9% vs. 0.2%, P<.001), and need for ICL replacement (5.7% vs. 1.1%, P<.001). Differences in opacity rate between the V3 and V4 designs were not due to differences in postoperative follow-up. CONCLUSION Implantation of the currently used V4 Staar Surgical model ICL resulted in significantly less anterior subcapsular opacities, clinically significant cataracts, and secondary ICL-related surgery.

Lens opacities after posterior chamber phakic intraocular lens implantation

PURPOSE To describe a case series to determine the incidence of lens opacities after posterior chamber phakic intraocular lens (IOL) implantation (STAAR Surgical, Monrovia, CA) for very high ametropias. DESIGN Retrospective, noncomparative, interventional case series. PARTICIPANTS Fourteen eyes of 170 consecutive eyes with high ametropias in whom lens opacities developed after posterior chamber phakic IOL implant (PCPIOL). INTERVENTION Posterior chamber phakic intraocular lens implant. MAIN OUTCOME MEASURES Lens opacity appearance, localization, and clinical course. RESULTS Fourteen eyes developed lens opacities 125 +/- 116 days after phakic IOL implant. All eyes had anterior subcapsular opacities, and two eyes also developed nuclear sclerosis. The anterior opacities did not extend posteriorly within the lens, and there were no posterior subcapsular cataracts. Seventy-one percent of opacities were first seen </=3 months, and 86% were seen </=7 months postoperatively. Seventy-nine percent of opacities were seen in the first or second implants of surgeons being trained; 19% of the first 16 cases and 0% of the next 43 cases of one surgeon developed opacities. Mean follow-up after opacity diagnosis was 9.1 +/- 6.8 months. Nine of the 14 (64%) opacities were asymptomatic. Two eyes developed nocturnal glare, with no loss of best-corrected visual acuity (BCVA) and one had loss of BCVA. Two additional eyes with both nuclear sclerotic and anterior subcapsular lens opacities had visual symptoms and/or loss of BCVA and underwent phakic IOL explantation, cataract extraction by phacoemulsification, and PCPIOL implant with good visual outcome. In the entire series, 5 of 170 (2.3%) implantations had symptomatic opacities in which 111 implantations were the first or second case of the implanting surgeon. CONCLUSIONS Lens opacities are a potential complication of phakic IOL implantation. Most lens opacities were first seen in the early postoperative period and were most likely due to surgically induced trauma. The anterior subcapsular type was most common and tended not to be rapidly progressive during the follow-up period. The presence of nuclear sclerotic cataract was visually significant and progressive. Long-term follow-up is warranted to evaluate the rate of progression and course of lens opacities after phakic IOL implant surgery.

Use of small incisions to control induced astigmatism and inflammation following cataract surgery

ABSTRACT A series of 55 small incision (3 mm) silicone‐implanted cataract cases closed with horizontal sutures and a concurrent series of 48 6 mm to 7 mm incision poly(methyl methacrylate)‐implanted cases closed with radial incisions were compared retrospectively for surgically induced astigmatism. At two to three weeks after surgery, the mean surgically induced astigmatism in the poly(methyl methacrylate) group was more than twice as high as in the silicone group (2.27 D vs 1.07 D, P < .01). In addition, a series of 41 small incision cases and a concurrent series of 61 cases with 6 mm to 7 mm incisions were compared for inflammation as measured by an FC‐1000 laser flare/cell meter. The larger incision cases had significantly higher average cell counts at one day and one week postoperatively (P = .005 and P = .03, respectively) and had significantly higher average flare measurement at one day (P = .01) than the smaller incision cases.

Comparison of the accuracy of the Binkhorst, Colenbrander, and SRK implant power prediction formulas.

The prediction accuracy of the Binkhorst, Colenbrander, and SRK formulas were compared in five series from different sources totalling 654 cases. The SRK formula was superior to both the other formulas by having a smaller average error per case, a smaller range of error from highest minus to highest plus, and a smaller proportion of cases with greater than 2 diopters (D) of error in all five series studied. In four of the five series, the SRK formula also had the greatest proportion of cases with less than 1 D of error. The Colenbrander formula was superior to the Binkhorst formula in all five series with regard to average error, proportion of cases with less than 1 D of error, and proportion of cases with more than 2 D of error. The range of error from highest minus to highest plus was equivalent with the two formulas. All available published literature on the accuracy of implant power prediction formulas was reviewed and appears to support our findings.

Corneal endothelial assessment after ICL implantation

Purpose: To evaluate the 3‐ to 4‐year effects of the Implantable Contact Lens (ICL) on the corneal endothelium. Setting: Multicenter study. Methods: Noncontact specular microscopy was performed as a subgroup study in a Phase III U.S. Food and Drug Administration clinical trial. Endothelial cell images were collected in the central region of the cornea before surgery and 3, 12, 24, and 36 months after surgery, with a few at 48 months. The images were recorded and analyzed later by a central reading center. The cell density, coefficient of variation, and percentage of hexagonal cells were determined. Results: The cumulative endothelial cell loss was between 8.4% and 8.9% over the first 3 years and between 8.4% and 9.5% over the first 4 years depending on the method of calculation. The cell loss between baseline and 3 months was 2.1%; 3 months and 1 year, 0.9%; 1 year and 2 years, 2.3%; 2 years and 3 years, 3.2%; and 3 years and 4 years, −0.1%. The coefficient of variation decreased over the course of the study, and the proportion of cases with hexagonal cells increased slightly. Conclusions: The cell loss between 1 year and 3 years in the absence of an increase in the coefficient of variation and/or a decrease in the percentage of hexagonal cells is most readily explained by prolonged corneal remodeling following the surgical procedure rather than ongoing cell loss. The cell loss observed between 3 years and 4 years (0.1% gain) was negligible. Regardless of the cause of the change in endothelial cell density over the first 3 years, the available 4‐year data suggest there was no ongoing chronic loss.

Randomized Prospective Comparison of Visian Toric Implantable Collamer Lens and Conventional Photorefractive Keratectomy for Moderate to High Myopic Astigmatism

PURPOSE To compare the Visian Toric Implantable Collamer Lens (TICL), a toric phakic intraocular lens (IOL), and photorefractive keratectomy (PRK) in the correction of moderate to high myopic astigmatism. METHODS This prospective, randomized study consisted of 43 eyes implanted with the TICL (20 bilateral cases) and 45 eyes receiving PRK with mitomycin C (22 bilateral cases) with moderate to high myopia (-6.00 to -20.00 diopters [D] sphere) measured at the spectacle plane and 1.00 to 4.00 D of astigmatism. All patient treatment and follow-up occurred at the Naval Medical Center San Diego. Study follow-up was 1 day, 1 week, 1, 3, 6, and 12 months postoperative. RESULTS Mean best spectacle-corrected visual acuity (BSCVA), change in BSCVA, proportion of cases with improvement of 1 or more lines of BSCVA, proportion of cases with BSCVA and uncorrected visual acuity (UCVA) 20/12.5 or better, proportion of cases with BSCVA and UCVA 20/16 or better (6 months, 88% vs 54%, P=.002), and predictability +/-1.00 D (6 months, 100% vs 67%, P<.001) were all significantly better in the TICL group than the PRK group at all time periods studied postoperatively. Similarly, contrast sensitivity, tested at both the 5% photopic level and the 25% mesopic level, was significantly better at all postoperative time points in the TICL group. Mean spherical equivalent refraction was closer to emmetropia (0.28+/-0.41 vs 0.76+/-0.86, P=.005), and predictability +/-0.50 D and stability of manifest refraction (+/-0.50 D and +/-1.00 D) were significantly better in the TICL group at all postoperative visits through 6 months. Mean astigmatism correction at 6 months was not significantly different between the two groups (0.52+/-0.33 vs 0.46+/-0.35, P=.450). CONCLUSIONS The TICL performed better than PRK in all measures of safety (BSCVA), efficacy (UCVA), predictability, and stability in this comparison, supporting the TICL as a viable alternative to existing refractive surgical treatments.