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.

Hexagonal keratotomy--should we still be trying?

BACKGROUND: I present my limited but positive experience with hexagonal keratotomy for hyperopia. METHODS: Eighteen consecutive eyes of 12 patients underwent hexagonal keratotomy during 1993. In addition to the primary procedures, 14 enhancements were required in seven eyes for both astigmatism and undercorrection. Surgical planning was based on refractive data only. All surgeries were performed by one surgeon using the open hexagonal keratotomy pattern. RESULTS: The patients' average age was 56 years (range, 38 to 67 years). Fourteen eyes were corrected for emmetropia. They had an average preoperative refraction of +2.22 +/- 0.64 diopters (D) and an average postoperative refraction of +0.11 +/- 0.49 D. Four eyes were corrected for near vision (-2.00 D). They had an average preoperative refraction of -0.53 +/- 0.83 D, and postoperatively their average refraction was -1.78 +/- 0.50 D. All four could read J1 without correction postoperatively. No eye lost more than one line of spectacle-corrected visual acuity; none had a major sight-threatening complication. CONCLUSIONS: Hexagonal keratotomy can correct 3.50 D or less of hyperopia. Conservative surgery with one major reoperation procedure is suggested. Because of the highly variable results noted in the literature and several reports of significant complications, I no longer perform or recommend hexagonal keratotomy.

Multicomponent intraocular lens.

BACKGROUND: Refractive surgery for any form of ametropia, including postoperative cataract rehabilitation, should have as its refractive goal an accuracy comparable to non-surgical modalities such as contact lenses and spectacles. To date, all refractive procedures fall significantly short of this goal because of poor predictability, significant instability, and annoying optical side effects. The multicomponent intraocular lens is being developed to further refine the accuracy of conventional IOL surgery by making the initial refractive result adjustable. METHODS: The multicomponent intraocular lens has three optical elements. The spherical base lens looks much like an ordinary PC-IOL. Attached to it are two exchangeable optical elements-a toric sandwich lens and a spherical or multifocal cap lens. The exchangeable elements allow the surgeon to refine the initial refractive result during a second, optional operative procedure. RESULTS: To date, prototype lenses have been fabricated from polymethylmethacrylate. These lenses have been assembled and disassembled both in vitro and in cat eyes to demonstrate the feasibility of this new concept. CONCLUSION: The multicomponent intraocular lens concept is a major departure from conventional IOL technology because it allows enhancement, or fine tuning, of an already fairly accurate refractive procedure, IOL surgery.

Do three-piece PMMA IOLs rotate after implantation in the capsular bag?

BACKGROUND: With the current interest in toric intraocular lenses (IOLs), it is critical to establish whether these implants rotate following cataract surgery. If there is continual rotation of the implant with capsular bag contraction, then the orientation of the astigmatic correction would be unstable and thus not clinically useful. METHODS: Twenty-eight eyes were followed for up to 6 months postoperatively. These consecutive eyes were selected on the basis of demonstrating adequate dilation following surgery, such that the points of haptic to optic insertion could be visualized with the slit-lamp microscope. Sequential photographs and comparisons of the orientation of the lenses postoperatively were performed. RESULTS: With the exception of one lens implant, none of the 28 IOLs demonstrated significant rotation. Of the 16 eyes followed for 6 months, none demonstrated rotation of greater than 4 degrees, which was within experimental error. CONCLUSIONS: Continued rotation of PMMA IOLs following implantation in the capsular bag seldom occurs. Thus, the concept of toric IOLs appears to be quite usable.

Refractive stability after cataract extraction using a 6.5-millimeter scleral pocket incision with horizontal or radial sutures.

BACKGROUND: Radial suturing of 6.5-millimeter scleral tunnel incisions following cataract surgery can create significant with-the-rule astigmatism in the immediate postoperative period. Because of the significant visual distortion and slow visual recovery seen with radial suturing, this study was undertaken to compare two other suturing techniques which induce lesser amounts of with-the-rule astigmatism in the immediate postoperative period. METHODS: The refractive behavior of eyes closed with loose radial sutures and with horizontal sutures was compared to the behavior of eyes closed with the more traditional "tight" radial sutures following phacoemulsification surgery. RESULTS: Eyes sutured with loosely tied radial sutures demonstrated minimal with-the-rule cylinder immediately following surgery (1.25 D) and showed a more rapid stabilization of astigmatism than did the eyes tied with tight radial sutures, 2 months versus up to 6 months. However, the eyes tied with horizontal sutures, which showed no induced with-the-rule astigmatism at the time of surgery, showed even more rapid stabilization between 5 days and 1 month from the time of surgery. CONCLUSION: To get the most rapid visual rehabilitation following cataract surgery, a wound closure which generates no induced with-the-rule cylinder such as horizontal sutures would be required.

The Casebeer system for predictable keratorefractive surgery. One-year evaluation of 205 consecutive eyes.

PURPOSE: This study documents the results of current radial keratotomy (RK) surgical technology, using the Casebeer keratorefractive system. These results are contrasted to those of the Prospective Evaluation of Radial Keratotomy (PERK) keratorefractive system, developed approximately 12 years ago. METHODS: Two hundred five consecutive surgical procedures were examined, which was the first year of experience with RK for one of the authors (TPW). All procedures fit within the Casebeer nomograms. Enhancement procedures were performed following the Casebeer system nomograms. RESULTS: Follow-up for 100% of patients was achieved. Postoperative cycloplegic refractions yielded an average of +0.27 +/- 0.58 diopters (D) of residual refractive correction (range, -0.88 to +2.50 D). One year postoperatively, 20/25 or better uncorrected visual acuity was achieved in 86% of patients and 20/40 or better uncorrected visual acuity was achieved in 99% of patients. Bothersome but not incapacitating side effects, such as glare, starbursting, and fluctuating vision, have been commonly observed with RK. CONCLUSION: The Casebeer system for keratorefractive surgery, which is easy to learn, can yield an extremely accurate surgical result. The major reason for increased accuracy compared with the PERK system is the surgeon's ability to titrate the primary surgical procedure with enhancement operations. Although RK is by no means a perfect surgical technique, side effects tend to be relatively minimal, and patient satisfaction tends to be extremely high.

Long-term endothelial cell loss following phacoemulsification: model for evaluating endothelial damage after intraocular surgery.

BACKGROUND: Newer concepts of phakic intraocular lens (IOL) surgery present concerns as to their long-term deleterious effect on the endothelium. We examine the behavior of the endothelium for up to 6 years following uneventful phacoemulsification surgery, to establish a baseline for what might be an acceptable level of endothelial cell loss due to intraocular surgical trauma. METHODS: Ninety-three eyes undergoing phacoemulsification surgery who had multiple endothelial specular microscopy examinations for up to 6 years were examined. Central endothelial specular photomicrographs were analyzed in all cases and the percent of endothelial cell loss as a function of time was calculated. Cell density calculations were corrected for the normal endothelial cell loss as a function of age. RESULTS: Routine uncomplicated phacoemulsification surgery demonstrated a 9% endothelial cell loss 1 year postoperatively. This is in marked contrast to the 16% average endothelial cell loss cited in the literature after phakic AC-IOL surgery. In general, anterior chamber IOL surgery following cataract removal compares unfavorably to posterior chamber IOL insertion long term (20% cell loss versus 12% cell loss). CONCLUSIONS: A model is proposed to look at the rate of endothelial cell loss that would be significant enough to create the threat for corneal edema long term following refractive intraocular surgery in young patients. Suggestions for critical comparisons between the observed endothelial aging seen with phakic IOLs and values for more routine IOL surgery are proposed to predict the long-term threat for endothelial cell loss and corneal decompensation, which might result many years after phakic refractive IOL surgery.

Astigmatism after cataract extraction: 6-year follow up of 6.5- and 12- millimeter incisions.

BACKGROUND: Cataract surgery and cataract surgeons have long realized that the surgical wound induces a significant change in the astigmatic properties of the eye postoperatively. In efforts to avoid or minimize these changes, there has been a progressive shift toward smaller incision sizes. However, that incision size which renders the eye astigmatically neutral has yet to be completely defined. This article will examine the long-term behavior of planned extracapsular surgical wounds (chord length 12 mm) and phacoemulsification wounds (chord length 6.5 mm), as well as look at potential animal models for defining how smaller incisions behave. METHODS: One hundred thirty-eight eyes of patients whose average age was 75 years have been followed for up to 6 years. Both vector and scalar analyses of the induced postoperative cylinder were evaluated. Additionally, the astigmatic properties of 10 nonhuman primate eyes which had phacoemulsification surgery were followed for 1 year. Finally, incisions of smaller chord lengths, as small as 2.5 mm, were examined in the nonhuman primate model. RESULTS: We demonstrated that with vector analysis, the induced cylindrical change with phacoemulsification wounds (6.5 mm) was 1.20 +/- 0.60 diopters and with planned extracapsular wounds was 2.20 +/- 1.30 D. In all cases, a significant against-the-rule shift was observed which was independent of the amount of surgically induced with-the-rule astigmatism at the time of surgery. Vector analysis was more appropriate because it demonstrated the against-the-rule shift for both patients whose preoperative cylinder was "with-the-rule" as well as those who were preoperatively "against-the-rule." In humans with 6.50-millimeter scleral incisions, these changes were completely stable 2 to 6 months postoperatively depending on the cylinder induced at the time of surgery. Experiments were also carried out in monkeys demonstrating that similar types of surgical wounds induced roughly the same amount of induced against-the-rule cylindrical shift (1.40 +/- 1.00 D), suggesting that this model is appropriate for looking at the behavior of cataract wounds in general. Smaller wounds in the nonhuman primate showed that 3.5- and 2.5-millimeter wounds were astigmatically neutral whereas 4.5-millimeter wounds and larger were not. Although the later study was performed with corneal incisions, whereas the studies mentioned earlier were all performed with scleral incisions, it is felt that this model could define that incision size which is neutral and that further work utilizing this model with other wound locations might be clinically helpful. CONCLUSIONS: Although the long-term behavior of 6.5-millimeter phacoemulsification wounds was generally stable, a small clinically insignificant shift did occur several years after the initial surgical procedure (0.30 D). Animal modeling, although difficult and costly, could provide relevant data in defining the specific size and placement of surgical wounds for cataract surgery.

Initial human experience with Permalens myopic hydrogel intracorneal lens implants.

BACKGROUND: Previous nonhuman primate experimentation has demonstrated the successful use of Permalens hydrogel intracorneal lens implants for the correction of hyperopic and myopic refractive errors. This article documents the first human experience with myopic Permalens hydrogel intracorneal lens implants. METHODS: In this article, we report an 18-month follow up on five patients implanted with minus power hydrogel intracorneal lenses. All surgery and follow-up examinations were performed in Bogota, Columbia. The mean preoperative spherical refraction was -14.00 +/- 5.00 diopters (range, -9.5 to -19.00 D). RESULTS: Corrections of up to 13.00 D were achieved. Corrections deviated from the predicted correction by a mean of -5.00 +/- 2.10 D (range, -2.80 to -8.00 D). No significant surgical or postoperative complications were noted. Visual recovery was rapid, usually achieving maximum acuity within 1 month. CONCLUSIONS: Successful myopic refractive changes were accomplished in all five human subjects. The major problem with the study to date has been a significant undercorrection of the preoperative refraction. We anticipate that further empirically derived relationships between hydrogel lens power and refractive change will allow a more accurate prediction of refractive result. Also, the ability to surgically interchange myopic hydrogel inlays should allow correction of any residual refractive errors.

Eight years experience with Permalens intracorneal lenses in nonhuman primates.

BACKGROUND: For the past 8 years, three independent laboratories have been researching the biocompatibility and performance of Permalens intracorneal lens implants in the corneas of nonhuman primates. Both myopic and hyperopic corrections have been achieved. This article describes the evolution of the intracorneal lens design and manufacturing process. METHODS: During this time period, 63 surgeries were performed on various species of nonhuman primates. Follow-up examination extended between 30 months and 8.2 years. Objective measures of refractive performance, as well as biocompatibility were made using slit lamp, retinoscopy, autorefractor, specular microscope, etc. Additionally, histopathology was performed on many of the specimens, both acute and chronic. RESULTS: Surgically successful implants were achieved in between 60% and 100% of eyes in the various series of lens implants outlined in the article. Levels of contamination in the preparation of hydrogels were felt to be responsible for many of the surgical failures. The removal of silicone and other contaminants seems to have significantly improved the biocompatibility of these materials within the cornea. The major histopathological finding was that there appeared to be some epithelial thinning over the implants, but in general excellent biocompatibility was obtained over the 8-year period outlined in this paper. CONCLUSIONS: Although extensive studies of biocompatibility have been completed, the future of the performance of these materials remains to be proven in the human subject. Additionally, empirical relationships between lens implant power and refractive results will have to be determined in humans, prior to their general clinical usage.

Lans lecture. Lamellar refractive surgery: where have we been and where are we going?

In summary, the greatest challenge for lamellar refractive surgery is in the treatment of myopia. There are and always will be patients who are satisfied with a partial correction of myopia. Many of these patients can be served quite adequately by currently available refractive techniques, but a technique in which level of accuracy is adequate for the treatment of myopia in general is not yet available. Lamellar refractive surgery--where have we been and where are we going? We have seen the evolution of the epikeratoplasty procedure for almost a decade and continue to see procedural changes which may increase the accuracy and stability of the procedure, such as alternative modalities for tissue preservation and alternative methods for surgical attachment. It remains potentially useful in several areas of refractive surgery, but its inaccuracy in the treatment of myopia remains a significant problem. Will the epithelial healing problems and postoperative care be too cumbersome for the general ophthalmologist? Will the excimer laser fill the needs of myopic refractive surgery? Personally, I do not feel that any biological lens, be it a cornea which has had incisions as with radial keratotomy, or a cornea which is remolded in one way or another as with the excimer laser, will produce predictable refractive results to the extent that is required to satisfy the general needs of the myopic population. Hydrogel keratophakia is in its infancy, but it holds the potential of being a far more accurate procedure because of the ability to interchange lenses to further refine the refractive result. Refractive surgery will in the next decade achieve a level of sophistication far greater than what we have seen to date. Lans could not have dreamed of the remarkable evolution in refractive surgical innovation in the past century. It is hoped that we will not have to wait that long to create a readily available solution to the problem of refractive surgery for myopia.