Conductive keratoplasty for the correction of low to moderate hyperopia: 1-year results on the first 54 eyes

Posterior Capsule Opacification With Two Hydrophobic Acrylic Intraocular Lenses: 3-Year Results of a Randomized Trial

PURPOSE

To compare the incidence and intensity of posterior capsule opacification (PCO) and neodymium-yttrium-aluminum-garnet (Nd:YAG) capsulotomy rates between 2 similar open-loop single-piece hydrophobic acrylic intraocular lenses (IOLs) that differ in the proprietary material characteristics and design features, over a period of 3 years.

DESIGN

Randomized, prospective, patient- and examiner-masked clinical trial with intraindividual comparison.

METHODS

Setting: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

PATIENT POPULATION

Eighty patients (160 eyes) had bilateral cataract surgery and received a Vivinex XY1 IOL in 1 eye and an AcrySof SN60WF IOL in the other eye.

OBSERVATION PROCEDURES

Follow-up examinations were performed 3 years after surgery. Digital retroillumination images were taken of each eye. The amount of PCO (score: 0-10) was assessed subjectively at the slit lamp and objectively using automated image analysis software (AQUA).

MAIN OUTCOME MEASURE

PCO score (scale, 0-10).

RESULTS

The mean objective PCO score of the Vivinex XY1 IOLs was 0.9 ± 0.8 compared to the PCO score of 1.4 ± 1.1 for the AcrySof SN60WF IOLs (P < .001). Three years postoperatively, 11.4% of patients had an Nd:YAG capsulotomy in the Vivinex XY1 eye and 18.6% had a capsulotomy in the AcrySof SN60WF eye (P = .23).

CONCLUSION

The new hydrophobic acrylic Vivinex XY1 IOL showed significantly lower PCO rates and lower YAG rates compared to the AcrySof SN60WF IOL. The interaction of various factors such as hydrophobic material, smooth optic surface, and sharp posterior optic edge plays a key role in PCO development.

360-Degree Iris Burns Following Conductive Keratoplasty

PURPOSE

The authors report a case with multiple iris burns after conductive keratoplasty to correct hyperopia.

METHODS

Case report.

RESULTS

A 52-year-old woman with hyperopia had a previous conductive keratoplasty procedure and underwent a conductive keratoplasty re-treatment 6 months later. Postoperatively, she presented with 360-degree iris burns in both eyes that were correlated with the corneal conductive keratoplasty scars. In addition, specular microscopy revealed decreased endothelial cell density for both eyes.

CONCLUSIONS

This is the first reported case of iris burns associated with conductive keratoplasty. [J Refract Surg. 2016;32(11):776-778.].

Corneal Refractive Procedures for the Treatment of Presbyopia

Purpose:

Refractive surgery has been in use for a long time and is evolving at a fast pace with several new corneal procedures being used for the correction of presbyopia. The purpose of this article is to give a comprehensive review of the literature to evaluate the outcome and success of different corneal refractive surgical procedures in presbyopic patients.

Methods:

We performed a comprehensive search on PubMed to identify published reports of the various procedures utilized in the past and present to correct presbyopia. The outcomes of these procedures were recorded.

Results and conclusion:

We found that varying rates of success have been reported with these procedures. The results of our exhaustive search are presented in this report for review.

Comparing the rate of regression after conductive keratoplasty with or without prior laser-assisted in situ keratomileusis or photorefractive keratectomy

Purpose:

To assess the regression rate of conductive keratoplasty (CK) in patients with or without previous laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

Setting:

University of Utah, Medical School, John A. Moran Eye Center, Salt Lake City, Utah.

Materials and Methods:

A retrospective, age-matched chart review identified records of 6 patients who underwent CK after refractive surgery and 12 patients who underwent CK without prior refractive surgery. The main outcome measures were postoperative uncorrected and corrected visual acuities and refraction changes over time.

Results:

Preoperatively, the mean manifest refraction spherical equivalent (MRSE) of the 15 eyes (12 patients) that underwent CK without refractive surgery was 0.83 diopters (D) and the 7 eyes (6 patients) that underwent CK after refractive surgery had an average MRSE of 0.27 D. Postoperatively, the mean MRSE of the refractive surgery patients was -0.86 D at 6 months, regressing to -0.67 D at 12 months. The postoperative MRSE in the eyes without refractive surgery was -0.58 D. at 6 months, regressing to -0.38 D at 12 months. The rate of regression was linear in both groups, calculated at 0.033 D per month in all patients.

Conclusions:

Patients with previous LASIK or PRK showed a greater treatment response to CK but regressed at a similar rate as those eyes without prior LASIK or PRK. Overall CK is a safe procedure that inevitably regresses.

Visual Outcomes of Conductive Keratoplasty to Treat Hyperopia and Astigmatism After Laser in situ Keratomileusis and Photorefractive Keratectomy

Aim:

To determine the effect of conductive keratoplasty (CK) for the treatment of induced hyperopia and astigmatism after complicated myopic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

Materials and Methods:

In this interventional case series, 11 eyes of seven subjects with a history of previous LASIK or PRK with inadequate stromal bed or flaps complications were enrolled. Inclusion criteria included residual spherical hyperopia of 1.00 to 3.00 diopters (D) and cylinder of –0.75 to –3.00 D. The modified Refractec nomogram and the LightTouch technique of CK were performed on all eyes. To treat cylinder, a pair of spots per –0.75 D of cylinder were delivered to the flat meridian. Uncorrected visual acuity at near and far (UCVAN and UCVAF respectively, logMAR), best corrected VA at near and far (BCVAN and BCVAF respectively, logMAR) were measured. Refractive outcome, contrast sensitivity, wave front aberrations were measured preoperatively and postoperatively. Statistical analysis was performed with the Wilcoxon signed rank test and the repeated measures analysis of variance with P<0.05 indicating statistically significant change from preoperatively to 1 year postoperatively.

Results:

The mean preoperative sphere (MS) was 2.57 ± 1.19 D and cylinder (MC) was –1.5 ± 0.49 D. Postoperatively, there was a significant decrease in MS to 0.36±0.98 D (P=0.003) and MC to –1.25 ± 0.76 D at 1 year (P<0.05, both cases). Spherical equivalent (SE) significantly decreased from +2.13 ± 1.09 D to –0.47 ± 1.29 D (P<0.001). The mean UCVAN significantly improved from 0.56 ± 0.32 preoperatively to 0.17 ±0.16 postoperatively (P=0.003). The mean UCVAF was 0.29 preoperatively and 0.22 postoperatively (P=0.353). Mean BCVAN was 0.18 and 0.02 after surgery, and mean BCVAF for far was 0.07 (P>0.05, both cases).

Conclusions:

CK is a predictable and reliable method to correct hyperopia after LASIK and PRK, however cylinder correction may induce irregular and unpredictable outcomes and a modified nomogram is required for further studies.

Topography-guided conductive keratoplasty: treatment for advanced keratoconus

PURPOSE

To evaluate the use of topography-guided conductive keratoplasty in eyes with keratoconus.

DESIGN

Interventional case series.

METHODS

We examined 21 eyes in 21 patients with advanced keratoconus. Topography-guided conductive keratoplasty was performed with intraoperative monitoring of corneal astigmatism using a surgical keratometer. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal topography, manifest refraction, intraocular pressure (IOP), corneal endothelial cell counts, complications, and eventual outcomes were evaluated.

RESULTS

UCVA (logarithm of the minimal angle of resolution [logMAR]), which was 1.65 ± 0.49 preoperatively, improved to 1.04 ± 0.64 at 1 week (P < .001) and 1.12 ± 0.61 at 1 month after surgery (P < .001). BSCVA, which was 1.02 ± 0.56 preoperatively, improved to 0.76 ± 0.65 at 1 week (P = .026) and 0.76 ± 0.60 at 1 month after surgery (P = .003). Manifest refraction, which was -15.13 ± 6.66 diopters (D) before surgery, declined to -9.97 ± 6.71 D at 1 month after surgery (P = .002). Although corneal topography reverted to the preoperative pattern and UCVA and BSCVA also regressed toward preoperative values, 12 of 21 eyes were better able to tolerate and conduct normal daily activities using contact lenses. Five subjects have undergone or are considering corneal transplantation after unsatisfactory postoperative results. No serious perioperative complication was observed.

CONCLUSIONS

Topography-guided conductive keratoplasty may be effective in reshaping corneal configuration in eyes with keratoconus, without serious complications, and possibly contributed to avoiding or delaying corneal transplantation.

Refractive surgery after corneal transplant

PURPOSE OF REVIEW

Ametropia and astigmatism following successful penetrating keratoplasty can seriously impact a patient's quality of vision. Similar limitations can result following anterior lamellar keratoplasty (ALK) and Descemet's stripping endothelial keratoplasty (DSEK). These patients often suffer from aniseikonia and can be intolerant of spectacles and contact lenses. Refractive surgery can correct both ametropia and astigmatism following corneal transplantation and improve a patient's final visual outcome. The same methods used to correct naturally occurring refractive errors are being used with increasing success in patients who have undergone corneal transplants.

RECENT FINDINGS

Many refractive options are available to treat ametropia following penetrating keratoplasty. Incisional keratotomies have been employed to treat high amounts of astigmatism. Photorefractive keratectomy (PRK) and laser in-situ keratomileusis (LASIK) are also used to treat myopia, hyperopia and astigmatism. LASIK has been shown to have an overall better outcome compared to PRK; however, the use of mitomycin-C with PRK has improved results. Phakic and pseudophakic piggyback intraocular lenses are also being used to treat high degrees of ametropia and astigmatism; however, the long-term results are somewhat limited.

SUMMARY

Refractive surgery can improve the final visual outcome of patients who have undergone successful corneal transplantation. Currently available modalities provide many options for patients who are intolerant of spectacles and contact lenses. Continued advances and research will enable surgeons to optimize visual quality in postkeratoplasty patients.

Conductive keratoplasty to treat hyperopic overcorrection after LASIK for myopia

PURPOSE

to investigate the refractive outcomes and stability of conductive keratoplasty (CK) for retreatment of myopic LASIK overcorrection.

METHODS

seven eyes (six patients) that were overcorrected after myopic LASIK by +1.00 to +2.75 diopters (D) manifest refraction spherical equivalent (MRSE) were retreated using CK. All eyes had insufficient stromal thickness for LASIK retreatment. LightTouch CK was performed at least 1 year after LASIK. Either 8 or 16 spots were applied at 7- and/or 8-mm zones on the cornea. Uncorrected distance visual acuity, manifest refraction, corrected distance visual acuity (CDVA), and postoperative complications were analyzed.

RESULTS

mean MRSE after CK at last follow-up was +0.38 ± 0.52 D (range: -0.38 to +1.13 D). The change in MRSE ranged from -0.63 to -2.38 D. Mean MRSE after CK changed from -0.60 ± 2.07 D (range: -3.38 to +1.50 D) at 1 week to +0.45 ± 0.69 D (range: -0.38 to +1.38 D) at 12 months. Two eyes experienced an initial overcorrection of -2.75 D and -3.38 D, respectively, at 1 week after CK. Cylinder ≤0.75 D was induced in four eyes, whereas one eye had a 0.75-D reduction in cylinder. All eyes had CDVA of logMAR 0.10 or better. Two eyes lost one line of CDVA and no eyes lost more than one line.

CONCLUSIONS

lighttouch CK retreatment for over-corrected myopic LASIK can reduce the hyperopia but produces minimal change in cylinder, and may be appropriate for eyes with insufficient stromal tissue for repeated excimer laser surgery. Early regression occurs commonly.

Ex vivo multiphoton analysis of rabbit corneal wound healing following conductive keratoplasty

Ex vivo multiphoton imaging is used to characterize rabbit corneal wound healing after conductive keratoplasty (CK) procedures. CK is performed on the right eyes from eight New Zealand albino rabbits while the left eyes are punctured by a keratoplast tip without energy application. Rabbits are humanely sacrificed 1 day, 1, 2, and 4 weeks after the CK procedure. Eye balls are enucleated and placed on the microscope for multiphoton imaging. Multiphoton imaging reveals damage of corneal epithelium and stroma caused by the CK procedure and the subsequent wound healing process can be followed without histological procedures. Multiphoton excited autofluorescence images demonstrate that re-epithelilialization is accomplished within 1 week in both CK and control groups. However, epithelial hyperplasia is observed in CK corneas. In addition, stromal wounds in the control group become inconspicuous within 1 week while obvious wounds still exist in CK corneas for at least 4 weeks. Postconductive keratoplasty corneal damage and wound healing can be characterized by multiphoton microscopy without histological procedures. Our results suggest that multiphoton microscopy has potential in the clinical evaluation of corneal damage due to refractive surgery, and can be used to study and reduce the unwanted side effects of these procedures.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

Conductive keratoplasty: histological study of human corneas

PURPOSE

To determine the morphologic changes in human corneas over time following radiofrequency-based conductive keratoplasty (CK) treatment.

DESIGN

Prospective, observational case series.

METHODS

In a single-center study six human corneas of six patients with localized peripheral keratoconus underwent CK treatment followed by penetrating keratoplasty. Three spots were applied in the periphery of each cornea (6 mm optical zone). Corneal buttons were examined with light and electron microscopy at different postoperative intervals up to 6 months post-CK.

RESULTS

In samples assessed on day one post-CK, small areas of detachment between the basal layer of epithelial cells and Bowman's layer were observed. At 1 week after the CK procedure, the epithelium appeared almost normal. Endothelium and Descemet's membrane had no alterations. In all samples, thermally induced misconfiguration of collagen fibers, described as "crumpled" changes of collagen layers, was observed reaching 75% to 80% of the stromal depth. The area of alterations had a cylindrical shape with a diameter of 120 mum.

CONCLUSIONS

The conductive keratoplasty procedure produced collagen "crumpling and splitting" changes in human corneas, which were observed during the follow-up of 6 months. Areas adjacent to treatment site were minimally damaged.

Conductive Keratoplasty for the Correction of Residual Hyperopia After LASIK

PURPOSE

To report the 6-month results concerning efficacy, safety, predictability, and stability of conductive keratoplasty for the correction of residual hyperopia after corneal refractive surgery.

METHODS

A total of 35 eyes (26 patients) with residual hyperopia after corneal refractive surgery ranging between +1.00 to +4.75 diopters (D) of spherical equivalent refraction were enrolled in the study and underwent conductive keratoplasty following a modified nomogram.

RESULTS

Variables and data were available for all eyes at 6 months postoperatively. A total of 24 (69%) eyes had uncorrected visual acuity (UCVA) of > or = 20/40, and 10 (29%) eyes had UCVA of 20/20. Manifest refractive spherical equivalent was within +/- 0.50 D in 17 (49%) eyes and within +/- 1.00 D in 25 (71%) eyes in cases of previous hyperopic LASIK; the optical zone was significantly increased.

CONCLUSIONS

Using a modified nomogram, conductive keratoplasty for correction of residual hyperopia was effective, but predictability was not satisfactory and safety needs to be established.

Conductive keratoplasty to treat complications of LASIK and photorefractive keratectomy

PURPOSE

To assess the outcomes of conductive keratoplasty (CK) for patients with complications related to LASIK or photorefractive keratectomy (PRK).

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Sixteen eyes of 15 patients were treated using CK after complications of initial LASIK or PRK surgeries. Five cases are described in detail.

INTERVENTION

Rehabilitative CK was performed.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), refractive error, keratometry, topography analysis, and a subjective assessment of visual quality.

RESULTS

After CK treatment, there was a mean improvement in UCVA of 2 lines; 1 eye lost >1 line of UCVA. Best-corrected visual acuity improved or remained the same in 12 of 15 eyes; no eyes lost >1 line of BSCVA. There was a mean reduction in astigmatism of 54%. Videokeratography generally demonstrated improved quality of the corneal optical surface, and patients reported a reduction in optical symptoms such as glare and halo.

CONCLUSIONS

Conductive keratoplasty may give improved corneal optics and vision in patients with complications of LASIK or PRK. This application of CK offers an alternative in cases in which further flap manipulation or laser treatments are contraindicated.

Refractive surgery after corneal transplantation

PURPOSE OF REVIEW

Many patients who have undergone corneal transplantation are unable to achieve satisfactory visual acuity with spectacle and contact lens correction alone. For these patients, refractive surgery becomes a viable option to reduce the post-keratoplasty ametropia. With the many recent advances in refractive surgery for naturally occurring refractive error, new possibilities arise for application to this complicated set of patients. This review discusses key recent developments in refractive surgery after corneal transplantation.

RECENT FINDINGS

The biomechanical effects of incisional keratotomy on post-keratoplasty corneas continue to be studied, and these techniques remain a common and simple method of reducing astigmatism. Photorefractive keratectomy, previously problematic for regression and haze formation, is gaining new prominence as early experience with the adjunctive use of mitomycin C has demonstrated good results. Long-term studies with laser in-situ keratomileusis (LASIK) have continued to show good safety and efficacy. Modern developments in cataract surgery appear to have lower incidences of graft rejection and failure. Developments in lens implantation technology continue to offer expanding options for intraocular refractive surgery.

SUMMARY

Although visual rehabilitation after corneal transplantation remains a formidable challenge, developments in refractive surgery for naturally occurring ametropias directly translate into an improved ability to help these most challenging refractive cases. Continued research will bring about improved efficacy while maintaining a high level of safety.

Intraocular Pressure Measurements After Conductive Keratoplasty

PURPOSE

To determine the possible impact of conductive keratoplasty (CK) on intraocular pressure (IOP) measurements.

METHODS

A prospective, single-center, noncomparative interventional case series was performed. Baseline and postoperative IOPs were measured by Goldmann applanation tonometry in 32 eyes of 18 patients who underwent CK for hyperopia correction. Mean follow-up was 11.9 months (range: 8 to 18 months).

RESULTS

After CK, a statistically significant decrease in the measured IOP was observed (before CK: 14.22+/-1.64 vs after CK: 12.66+/-2.21, P<.001). The change in IOP readings postoperatively was not correlated with age, sex, keratometric readings, or attempted correction.

CONCLUSIONS

Despite the limitations due to the small number of patients enrolled in this study, the applanation tonometer appears to underestimate the true IOP after CK.

Treatment of Presbyopia With Conductive Keratoplasty??

PURPOSE

To provide 6-month results of a 1-year clinical trial evaluating conductive keratoplasty (CK) for the treatment of presbyopic symptoms in emmetropic and hyperopic eyes.

METHODS

A total of 143 patients with presbyopic symptoms were enrolled in this 1-year United States FDA clinical trial and treated to improve near vision in 1 eye (unilateral treatment). In addition, 33 fellow eyes were treated to improve distance vision (bilateral treatment). For near vision correction, the target refraction was up to -2.0 D in the nondominant eye, and for distance vision correction, 0.0 D. Enrolled patients had a preoperative spherical equivalent of plano to +2.00 D, no more than 0.75 D of refractive astigmatism, and were 40 years of age or older. No retreatments were performed.

RESULTS

Of the eyes treated for near, 77% had uncorrected near vision of J3 or better at 6 months postoperatively. A total of 85% of all patients had binocular distance UCVA of 20/25 or better along with J3 or better near, a combination that represents functional acuity for a presbyope. Sixty-six percent of eyes treated for near had a manifest refractive spherical equivalent (MRSE) within +/- 0.50 D of intended at 6 months. In 89% of eyes, the MRSE changed 0.05 D or less between 3 and 6 months postoperatively. After month 1, the incidence of variables associated with safety was 1% or lower. Seventy-six percent were very satisfied or satisfied with their procedure.

CONCLUSIONS

CK appears to be very safe and effective in producing functional visual acuity in presbyopic eyes up to 6 months following the procedure. Patient satisfaction with the procedure is similar to that of monovision LASIK.

Laser in situ Keratomileusis for Residual Hyperopic Astigmatism After Conductive Keratoplasty

PURPOSE

To report a case of laser in situ keratomileusis (LASIK) in a patient with previous conductive keratoplasty.

METHODS

A 48-year-old man underwent conductive keratoplasty for low hyperopic astigmatism (manifest refraction OD: +2.25 -0.50 x 77 degrees; OS: +2.50 -0.50 x 105 degrees). Three months postoperatively, UCVA was 20/25 and BSCVA was 20/20 in both eyes; manifest refraction OD: -0.25 -0.75 x 110 degrees; OS: +0.75 -0.75 x 50 degrees. Sixteen months after the operation, regression of refractive outcome was (manifest) OD: +1.75 -1.25 x 90 degrees; OS: +2.50 -0.50 x 85 degrees; UCVA was 20/40 in the right eye and 20/63 in the left eye and BSCVA was 20/20 in both eyes. LASIK was performed for hyperopic regression in the left eye using an automated microkeratome (Alcon SKBM, 130-microm plate; Aesculap-Meditec MEL 70 excimer laser).

RESULTS

LASIK was uneventful and no intraoperative or postoperative complications related to the previous conductive keratoplasty procedure or LASIK were observed. Three months after LASIK and 19 months after the initial conductive keratoplasty, the patient's left eye was emmetropic; UCVA was 20/20(-2), BSCVA was 20/20 and manifest refraction was +0.25 -0.25 x 35 degrees. There was a uniform increase in topographical steepening. Visual acuity, refraction and topographic findings remained unchanged at 6 months.

CONCLUSIONS

Even though our experience is limited, treatment of hyperopia with LASIK in an eye with refractive regression following previous conductive keratoplasty resulted in a predicted refractive outcome, with no complications, and improvement in visual acuity at 6 months follow-up.

Conductive Keratoplasty for Low to Moderate Hyperopia: 1-year Results

PURPOSE

To assess the safety, efficacy, and stability of conductive keratoplasty in the treatment of low to moderate hyperopia and evaluate the impact of the procedure on the quality of vision.

METHODS

Thirty-six eyes (25 patients; 13 female and 12 male) were treated for hyperopia up to +3.25 D with a Refractec ViewPoint CK system and followed for 1 year. Mean age was 50.2 +/- 8.7 years (range 31 to 71).

RESULTS

Before surgery, mean spherical equivalent refraction was +1.90 +/- 0.60 D (range +1.00 to +3.25 D), decreasing at 1 year after conductive keratoplasty to -0.06 +/- 0.80 D, and was within +/- 0.50 D of emmetropia in 68% (24 eyes) and within +/- 2.00 D in all eyes. Twelve months after conductive keratoplasty, uncorrected visual acuity was 20/20 or better in 19 eyes (50%) and 20/40 or better in 32 eyes (89%). No eye lost > or = 2 Snellen lines or had induced cylinder > or = 2.00 D. The mean root mean square values for higher order optical aberrations were 0.060 +/- 0.039 before and 0.174 +/- 0.170 at 3 months after surgery. No statistically significant changes in contrast sensitivity were noted.

CONCLUSIONS

Conductive keratoplasty for low to moderate hyperopia provided safe, effective, and stable results both in refraction and quality of vision.

Corneal iron ring after conductive keratoplasty

PURPOSE

To report formation of corneal iron ring deposits after conductive keratoplasty.

DESIGN

Observational case report.

METHODS

Case report.

RESULTS

A 54-year-old woman underwent conductive keratoplasty for hyperopia. One year after conductive keratoplasty, iron ring pattern pigmentation was detected at the corneal epithelium of both eyes.

CONCLUSIONS

This is the first report of the appearance of corneal iron ring deposits following conductive keratoplasty treatment in a patient. It is suggested that alterations in tear film stability, resulting from conductive keratoplasty-induced changes in corneal curvature, constitute the contributory factor for these deposits.

Update on nonexcimer laser refractive surgery technique: conductive keratoplasty

Excimer laser-based refractive surgery techniques have been the most popular forms to correct myopia, hyperopia, and astigmatism. However, development of non-excimer based refractive surgery such as thermal techniques provides a viable alternative to laser vision correction. Earlier forms of thermal techniques showed a lack of predictability and stability, resulting in the abandonment of the further development of these techniques. Recently, conductive keratoplasty, a laserless, radiofrequency-based technique, has been approved by the FDA for the correction of low to moderate hyperopia. Preliminary data showed that conductive keratoplasty seems to be safe, effective, and showed good refractive stability. This review will discuss recent studies on conductive keratoplasty technique in terms of its efficacy, safety, refractive predictability, and stability.

Conductive Keratoplasty to Correct Hyperopic Astigmatism

PURPOSE

To evaluate the efficacy of conductive keratoplasty in the treatment of pre-existing and surgically induced hyperopic astigmatism.

METHODS

In this prospective, noncomparative case series, four eyes of four subjects, two female and two male (age 25 to 47 yr) were treated for hyperopia (up to +5.50 D) and hyperopic astigmatism (up to +5.75 D) with the Refractec ViewPoint conductive keratoplasty system. The follow-up period was 6 months. Uncorrected and spectacle-corrected visual acuity, manifest and cycloplegic refraction, and videokeratographs were obtained before and after surgery. We treated two patients who had already had LASIK, one of them with a decentered ablation and the other with flap striae, one patient after PRK, and one patient with keratoconus.

RESULTS

No complications were observed. No eye lost lines of spectacle-corrected visual acuity. All eyes showed improvement of uncorrected visual acuity of 3 or more lines. Videokeratographs demonstrated improved centration and reduction in keratometric power readings. Each eye was analyzed separately, including a comparative analysis of the proposed nomograms and quality of vision after surgery.

CONCLUSIONS

Conductive keratoplasty may be a minimally invasive solution for patients with irregular hyperopic astigmatism, offering improved quality of vision in instances of flap striae by tightening the central cornea.

Comparison of Videokeratographic Functional Optical Zones in Conductive Keratoplasty and Laser in situ Keratomileusis for Hyperopia

PURPOSE

To compare the videokeratographic functional optical zone of eyes treated with conductive keratoplasty to eyes treated with laser in situ keratomileusis (LASIK) for hyperopia.

METHODS

Sixteen eyes treated with conductive keratoplasty for hyperopia were retrospectively evaluated to determine the size of the videokeratographic functional optical zone. The functional optical zone of these eyes was compared to the functional optical zone of 16 eyes that underwent LASIK for hyperopia with the VISX S2 excimer laser, for comparable amounts of hyperopia. The functional optical zone was measured at the edge of central corneal steepening and paracentral flattening on videokeratography 3 to 6 months after surgery.

RESULTS

The functional optical zone after surgery measured an average of 5.6 mm horizontally and 5.6 mm vertically in the conductive keratoplasty eyes, and 4.7 mm horizontally and 5.1 mm vertically in the hyperopic LASIK eyes (P<.001 and P<.005). The mean functional optical zone area was 31.1 mm2 in the conductive keratoplasty eyes and 24.6 mm2 in the hyperopic LASIK eyes (P<.001). The functional optical zone created by conductive keratoplasty had more uniform central steepening and less peripheral blending than the functional optical zone created by hyperopic LASIK.

CONCLUSION

Conductive keratoplasty was effective at creating central steepening in the cornea. The functional optical zone resulting from conductive keratoplasty was significantly larger than that obtained with hyperopic LASIK using the VISX S2 excimer laser.

Cataract surgery in patients with prior refractive surgery

As the number and types of keratorefractive procedures increase and as the baby boomer population moves into the "cataractous decades," the number of patients requiring cataract surgery following refractive surgery grows larger each year. While technological advances in surgical instrumentation and intraocular lens (IOL) design allow us to perform cleaner, faster, and more reliable cataract extractions, the ultimate postoperative refraction depends primarily on calculations performed before surgery. Third-generation IOL formulas ( Haigis, Hoffer Q, Holladay 2, or SRK/T) provide outstanding accuracy when used for eyes with physiologic, prolate corneas. In addition, most instruments used today for measuring corneal curvature and power were designed before the era of refractive surgery. These formulas and instruments make assumptions about the anatomy and refractive properties of the cornea that are no longer valid following most keratorefractive procedures. These breakdowns in IOL calculation often result in a "refractive surprise" after cataract surgery, which may require subsequent surgical correction. This article examines recent publications of modeling studies of various methods for estimating effective K values for IOL calculation, cataract surgery case series following refractive surgery, new corneal topography technologies and methods for correcting "refractive surprises" postoperatively.

Conductive keratoplasty to correct residual hyperopia after corneal surgery

Conductive keratoplasty (CK) is an electrical-current-based technique for steepening the central cornea to reduce low to moderate hyperopia. We report 4 patients who had CK to correct hyperopia after laser in situ keratomileusis (LASIK) and were followed for at least 6 months. An overcorrection was noted after the CK procedure in all patients, but no sight-threatening complications arose. Conductive keratoplasty appears to be safe and well tolerated after LASIK. However, the algorithms should be modified to increase the predictability of the CK procedure in previously treated eyes.