Three year results of refractive keratotomy using the Casebeer System

Intraocular lens power calculation in eyes with previous corneal refractive surgery

Intraocular lens (IOL) power calculation after corneal refractive surgery (CRS) becomes an expanding challenge for ophthalmologists as more and more cataract surgeries after CRS are required. These patients typically also have high expectations as to visual performance. Conventional IOL power calculation schemes frequently provide inaccurate results in these cases. This review aims to summarize and recommend currently available IOL power calculation methods for eyes with the most common CRS methods: radial keratotomy (RK), photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE). To this end, biometry measuring methods and IOL formulas will be explained and combinations of both are proposed. In synopsis, it is evident that the latest generation of vergence formulas exhibit favorable IOL power prediction accuracy in post-CRS eyes, even though the predictive precision of methods in eyes without CRS is not attained. Ray tracing computation, intraoperative aberrometry, and machine learning–based formulas hold potential to further improve refractive outcomes in post-CRS eyes.

Advances in refractive surgery: 1975 to the present

PURPOSE

To review the major advances in the field of refractive surgery occurring over the past 25 years.

METHODS

Literature review.

RESULTS

The major developments in refractive surgery over the past 25 years are reviewed.

CONCLUSIONS

The past 25 years have witnessed great changes in refractive surgery. As a result of advancements in technology, instrumentation, and technique, we have seen improvements in the treatment of all types of ametropias. In this article, we review some of the successes and failures of the past quarter-century.

Minoxidil-induced alteration of corneal topography after radial keratotomy

PURPOSE

To determine the antiproliferative effect of minoxidil on human corneal epithelium (hCE) proliferation in vitro and to assess whether topical minoxidil can significantly alter corneal topography after radial keratotomy (RK) by inhibiting myofibroblast activity in the keratotomy wound.

SETTING

Corneal Research Laboratory, University of Chicago, Illinois, USA.

METHODS

In the in vitro evaluation, proliferating hCE was exposed to minoxidil (0.1 to 2.0 mM) for 96 hours to determine the minimum inhibitory dose. Human corneal epithelium cell proliferation was assessed by the incorporation of bromodeoxyuridine (BRDU) into DNA. In the in vivo analysis, eight New Zealand albino rabbits had an eight-incision bidirectional RK on one eye and were divided into two groups. The control eyes (n = 3) received tobramycin and dexamethasone (TobraDex), ciprofloxacin hydrochloride (Ciloxan), and balanced salt solution (BSS) drops four times a day for 3 weeks, while the treatment eyes (n = 5) received TobraDex, Ciloxan, and minoxidil 1.0 mM drops four times daily for 3 weeks. The net change in corneal curvature at 3 weeks was analyzed with corneal topography. Myofibroblast activity in the keratotomy wound was assessed using alpha smooth muscle actin staining techniques.

RESULTS

At concentrations of 1.0 mM and above, minoxidil caused a statistically significant, dose-dependent reduction in hCE cellular proliferation ranging from 29 to 44% (P < .05). Minoxidil (1.0 mM) caused a statistically significant central corneal flattening effect of 4.66 diopters (D) after RK in the treatment eyes compared with 1.11 D in the control eyes (P = .05). Histologically, minoxidil-treated keratotomy wounds lacked cells with contractile elements consistent with myofibroblast differentiation. Corneal epithelial wound healing was similar in both groups.

CONCLUSION

At the appropriate dose, topical minoxidil may be a useful adjunctive treatment that can reduce the number of undercorrections after mini-RK without apparent toxicity to the corneal epithelium.

Casebeer System for refractive keratotomy: patient satisfaction

PURPOSE

To evaluate patient satisfaction 3 years after radical keratotomy (RK) using the Casebeer nomograms.

SETTING

The Werblin Center, Princeton, West Virginia.

METHODS

This study assessed the satisfaction of 96 patients who had bilateral distance correction by RK using the Casebeer System. The cases were part of the first 241 consecutive refractive keratotomy procedures (N = 128 patients) performed by one surgeon. Ninety-nine percent of the 96 patients in this study completed a questionnaire on satisfaction and visual symptoms 3 years postoperatively. A separate control population of 105 consecutive patients about to have RK surgery were asked to complete a questionnaire about their preoperative symptoms.

RESULTS

Ninety-eight percent of patients were very to moderately satisfied 3 years after the procedure, 99% said they would have surgery again if given the chance, and 96% said they would recommend it to others. However, 69% stated they had mild to very severe symptoms 3 years postoperatively compared with 28% in the control group.

CONCLUSION

Despite an extremely high degree of patient satisfaction, about 99%, the 1% dissatisfaction rate seen in this study could have be very significant in this young, potentially litigious patient population.

Three year results of refractive keratotomy using the Casebeer System

PURPOSE

To analyze the results of one surgeon's first refractive keratotomy surgeries.

SETTING

The Werblin Center, Princeton, West Virginia.

METHODS

The three year results of 241 consecutive surgical procedures (128 patients) using Casebeer nomograms were examined. The average preoperative myopia was -4.07 +/- 1.89 diopters.(D). Two hundred twenty-two eyes were corrected with a goal of emmetropia. Two hundred of 241 eyes (83%) were followed for 3 years; 35 eyes (15%) were followed for fewer than 3 years after the last enhancement procedure, and 6 eyes (2%) were lost to follow-up.

RESULTS

At 3 years postoperatively (range 30 to 44 months), excluding postoperative suture and ALK procedures, mean residual manifest refractive error (spherical equivalent) was -0.04 +/- 0.67 D (-2.25 to + 3.13 D). Mean residual cycloplegic error was + 0.45 +/- 0.76 D (-1.00 to + 4.13 D). Eighty-seven eyes (36%) required between one and six enhancement procedures. One hundred fifteen eyes (52%) had 20/20 or better visual acuity and 214 eyes (96%), 20/40 or better. One hundred fifty-two eyes (84%) were within +/- 1.0 D and 120 eyes (66%) were within +/- 0.5 D. Ten eyes (4%) lost one or more lines of best corrected acuity.

CONCLUSION

Using the Casebeer system for refractive keratotomy, we obtained 20/40 or better uncorrected visual acuity in 96% of eyes with low to moderate levels of myopia. However, a significant number of enhancement procedures, 36% overall, were required to achieve this level of success. Hyperopic shift remains a significant concern following radial keratotomy procedures.

Hyperopic shift after refractive keratotomy using the Casebeer System

PURPOSE

To determine the degree of hyperopic shift following refractive keratotomy.

SETTING

The Werblin Center, Princeton, West Virginia.

METHODS

The results of 241 consecutive radial/astigmatic keratotomy procedures in 128 patients were studied. All procedures were performed using Casebeer nomograms. Refractive follow-up information was obtained for 78% of patients at 3 months (range 1 to 6 months), 1 year (range 6 to 21 months), and 3 years (range 30 to 44 months).

RESULTS

Overall, the amount of hyperopic change decreased significantly (P < .05) during the 3 year period, from + 0.34 diopters (D) per year to + 0.12 D per year. Eyes with more than 6.0 D of preoperative intended correction were more unstable (+ 0.49 D in the first year and + 0.44 D in the second and third years) than eyes with less than 5.0 D (+ 0.27 D and + 0.05, respectively).

CONCLUSION

Because the average magnitude of the hyperopic shift was + 0.6 D in the first 3 years after surgery, a slight undercorrection, -0.5 D to -0.7 D, should be the refractive endpoint for primary and enhanced refractive keratotomy surgery.