Automated Lamellar Keratoplasty Research Articles

Comparison of Automated Lamellar Keratoplasty and Phototherapeutic Keratectomy for Salzmann Nodular Degeneration

The aim was to compare the outcomes of automated lamellar keratoplasty (ALK) and phototherapeutic keratectomy (PTK) for Salzmann nodular degeneration (SND). The records of patients undergoing PTK and ALK for SND at the Cornea services of our tertiary care center from were evaluated retrospectively. Twenty-one eyes of 21 patients underwent ALK, and 28 eyes of 28 patients underwent PTK. The distribution of age, pachymetry, and pretreatment corrected distance visual acuity (CDVA) was similar in both groups. In the PTK group, the mean ablation was 60.71±14.3 μm, the CDVA improved from 0.09 preoperatively to 0.21 at 6 months. None of the cases demonstrated significant scarring or any evidence of infection. In the ALK group, the mean host cut was 8.5±0.41 mm, and the donor cut was 8.64±0.45 mm, donor thickness 350 μm, and host cut 250 μm. The mean CDVA improved from 0.09 preoperatively to 0.24 at 6 months. At 6 months, 2 patients demonstrated persistently high astigmatism (>8 D), and 2 had graft interface infection. The CDVA at 6 months and the overall change in the CDVA in both the groups was similar (P=0.06 and 0.07, respectively, Mann-Whitney U test). However, the epithelialization time was significantly longer in the ALK group. The PTK for SND achieved equivalent visual results compared with ALK and may have an important keratoplasty sparing role. The incidence of complications was lesser in PTK in our study cohort.

Intraocular Lens Power Calculation After Automated Lamellar Keratoplasty for High Myopia

To report intraocular lens (IOL) power calculation in 2 eyes that were highly undercorrected by previous myopic automated lamellar keratoplasty (ALK). A 35-year-old man underwent bilateral myopic ALK, which caused high residual myopia (-9.0 -4.0 x 171 and -9.5 -4.5 x 74). The patient then underwent cataract surgery with IOL implantation for cataract development. The double-K clinical history method was utilized, and satisfactory IOL power prediction results were obtained. Two no-history IOL power calculation methods (Rosa correcting factor method and Ferrara theoretical variable refractive index method), which involved axial length-dependent modification of the keratometer-measured corneal radius, and 1 no-history IOL power calculation method (Shammas' method), which involved axial length-independent modification of the keratometer-measured corneal power, were tested on these 2 eyes. In both eyes, the double-K SRK-T clinical history method gave small IOL prediction errors (-0.66 and -0.81 D). The Shammas' no-history method gave a slightly higher IOL prediction error in the right eye (-1.67 D) and a small IOL prediction error in the left eye (-0.74 D). Unacceptable IOL power prediction errors would have resulted if Rosa's correcting factor method (-8.07 and -8.35 D) or Ferrara's theoretical variable refractive index method (-17.56 and -18.51 D) had been applied. When we utilized Rosa's method for the IOL power calculation by assuming that the previous ALK had fully corrected the refractive error, the predicted IOL powers were very close to the benchmark IOL powers (IOL power prediction errors: 1.16 and 0.37 D). When we utilized Ferrara's method with the same assumption, the IOL power prediction errors remained high (-6.32 and -7.16 D). For patients who have had previous myopic ALK (and whose eyes are highly undercorrected) and who require cataract surgery and for whom the pre-ALK history is available, the double-K method appears to yield excellent predictive results. However, if the pre-ALK history is not available, the Shammas' no-history method appears to yield better results than the Rosa's or the Ferrara's method. High undercorrection by the previous ALK might have been one of the major reasons why Rosa's method resulted in a high IOL prediction error in these 2 eyes. The cause for the marked IOL prediction error by Ferrara's method in this case, however, remains to be determined.

VHF Digital Ultrasound Three-Dimensional Scanning in the Diagnosis of Myopic Regression After Corneal Refractive Surgery

To perform VHF digital ultrasound scanning and analysis of a case of high-myopic undercorrection in an eye that had undergone multiple surgical interventions for the correction of an initial refraction of -12.00 diopters (D). A 49-year-old woman was evaluated after undergoing three surgical interventions for correction of an initial refraction of -12.00 D in the left eye. Automated lamellar keratoplasty (ALK) was followed by arcuate keratotomy (for induced astigmatism) and surface photorefractive keratectomy (PRK). The residual ametropia on presentation was -6.75 -3.50 x 95 degrees. VHF digital ultrasound scanning and analysis was performed. On ultrasound, the ALK interface was clearly visible. Residual stromal thickness beneath the cap was at least 275 microm. The absence of Bowman's layer indicated the region of PRK. New stroma and nascent stromal layers were differentiated within the flap. Neo stromal deposition and central epithelial hyperplasia were determined to be responsible for the myopic shift, as opposed to biomechanical changes. In this case, refraction, slit-lamp examination, and topography were unable to provide a diagnosis for regression following multiple corneal refractive procedures. By providing layered anatomical mapping, VHF digital ultrasound scanning was able to exclude a diagnosis of ectasia and provide anatomical diagnostic information to explain the clinical observations.

Arcuate keratotomy for asymmetrical steep islands after laser in situ keratomileusis and automated lamellar keratoplasty

Purpose To determine the safety and efficacy of arcuate keratotomy (AK) to reduce or eliminate steep asymmetrical islands after laser in situ keratomileusis (LASIK) and automated lamellar keratoplasty (ALK). Setting Rancho Bernardo Laser and Vision Center, San Diego, California, USA. Methods This retrospective and noncomparative interventional study comprised 8 eyes of 5 patients who received arcuate incisions to reduce topographically defined asymmetrical steep islands after LASIK (n = 7) and ALK for hyperopia (n = 1). The islands occurred unexpectedly after standard excimer laser treatment (VISX Star and S2) for myopic astigmatism that induced irregular astigmatism and unwanted optical effects. Cases occurred consecutively over 16 months, an incidence of less than 1%. Arcuate incisions extended 30 or 45 degrees in LASIK eyes based on the amount of residual refractive astigmatism and were placed at 7.0 mm on the steep axis. Radial incisions were limbal sparing to a 5.0 mm optical zone following the Casebeer nomogram. Outcome measures were uniformity of postenhancement topography, uncorrected visual acuity (UCVA), postenhancement refraction, and reduction in unwanted optical effects. Results The preenhancement mean spherical equivalent (SE) in the LASIK eyes was −0.99 diopters (D) ± 0.48 (SD); the astigmatism ranged from 0.50 to 1.75 D. After incisional keratotomy, the mean SE was −0.21 ± 0.12 D and the net residual astigmatism was reduced to a range of 0 to 0.75 D. All 8 eyes had AK to reduce topographically defined steep islands that were causing visual blurring and unwanted optical effects including ghosting, halos, and polyplopia. After enhancement, there was a marked reduction in the asymmetrical steep islands by topography, fewer unwanted optical effects, less refractive astigmatism, and improved UCVA. Two patients retained small inferior steep areas that may indicate forme fruste keratoconus, although this condition was not detected preoperatively by topographical indices. Conclusions Uncorrected visual acuity improved and unwanted optical effects were reduced after AK on the peripheral axis of asymmetrical steep islands that occurred after uneventful LASIK and hyperopic ALK. This relatively simple incisional approach may be used until more advanced topography-linked ablations with rapid and precise eye tracking are perfected and widely available.

Bilateral Retinal Hemorrhages Following Automated Lamellar Keratoplasty

We describe a case of bilateral multifocal retinal hemorrhages after receiving automated lamellar keratoplasty (ALK) surgery in a 32-year-old male with extremly myopic eyes. Before surgery, there was no retinal hemorrhage in routine fundus examination. This patient visited our clinic and complained of decreased vision in both eyes 2 weeks after the ALK surgery. Upon examination, his best-corrected visual acuity (BCVA) was 0.6 with -8.5-1.5 x 100(0) in the right eye and 0.9 with -4.0-2.50 x 90(0) in the left eye. Fundus examination revealed scattered multiple round focal retinal hemorrhages in both eyes. No evidence of choroidal neovascularization was noted. The retinal hemorrhages resolved 10 weeks later. The BCVA recovered to 1.0 in the right eye and 0.9 in the left eye. This case highlights the relationship between the postoperative bilateral posterior pole hemorrhages and the automated lamellar keratoplasty surgery, in which a microkeratome was used to create a corneal flap and keratectomy. Patients should be informed of this rare complication before surgery.

Making Sense of Refractive Surgery in 2001: Why, When, for Whom, and by Whom?

Making Sense of Refractive Surgery in 2001: Why, When, for Whom, and by Whom?

Wound healing following anterior keratectomy and lamellar keratoplasty in the pig.

To examine corneal wound healing in an animal model of two types of mechanical lamellar keratectomy. One eye from each of 28 pigs was studied. Using a motorized keratome, corneas were subjected to an anterior lamellar keratectomy with removal of anterior stroma and epithelium, or to automated lamellar keratoplasty (ALK) with reapposition of a corneal flap. The exposed stromal surfaces were labeled intraoperatively with a fluorescent dye (DTAF) to assess deposition of stromal components during subsequent wound healing. Examination before surgery and enucleation included measurement of corneal curvature and intraocular pressure, and assessment of corneal haze. Eyes were prepared for histological examination, fluorescence microscopy, and for fibronectin immunohistochemistry. Both keratectomy procedures produced flattening of corneas by up to 3.80 diopters, 28 days after surgery. Corneal haze was more pronounced in eyes from which epithelium was removed (anterior lamellar keratectomy group). The increased haze in this group was associated histologically with appearance of many reactive keratocytes and inflammatory cells, deposition of new stromal material, and more widespread appearance of fibronectin immunoreactivity. In the lamellar keratoplasty group, only the edges of the corneal wound showed significant reactivity, and included keratocyte activation and epithelial ingrowth. The pig provides a useful model for studies of refractive surgical techniques using procedures and instruments designed for use in humans. Mechanized keratectomy procedures that minimize disruption of the epithelium and Bowman's layer produce a less reactive corneal wound than procedures in which an expanse of epithelium and anterior stroma are removed.

Ocular Integrity after Refractive Procedures

The purpose of the study was to determine the integrity of human eyes after refractive procedures. Whole human globes underwent either radial keratotomy (RK) with eight incisions, automated lamellar keratoplasty (ALK), photorefractive keratectomy (PRK), or excimer laser assisted in situ keratomileusis (LASIK). Eyes then were subjected to quantitatively increasing levels of trauma until rupture occurred. All eyes operated on required less energy to rupture as compared with that of control eyes. The mean number of trials required for rupture is as follows (energy doubled with each successive trial): normal, 4.29; LASIK, 3.80; ALK, 3.67; PRK, 3.60; and RK, 2.83. The level of energy required to rupture normal, ALK, PRK, and LASIK eyes was not significantly different. All RK eyes ruptured at incisions. Most ALK, PRK, and LASIK eyes ruptured near the flap edge or limbus. Most normal eyes ruptured with both corneal and scleral involvement. Age of tissue donors at the time of death and time elapsed between death and procedure were not significantly different between groups (P = 0.88 and 0.79, respectively). The energy required to rupture ALK, PRK, and LASIK eyes is not significantly different from that for normal eyes. The RK eyes ruptured with significantly less energy than did normal eyes. All RK eyes ruptured at incision sites.

Analysis of Corneal Topography after Automated Lamellar Keratoplasty

Purpose: The purpose of the study is to evaluate the effects of myopic automated lamellar keratoplasty (ALK) on corneal topography.Methods: The authors performed a retrospective study of computer-assisted topographic maps obtained before surgery and at the last follow-up visit of 9 patients (13 eyes) who underwent ALK without enhancement to correct moderate-to-high myopia during a 12-month period.Results: Follow-up ranged from 3.5 to 13 months (mean, 5.8; standard deviation, 3.1). The mean manifest spherical equivalent changed from -10.5 ± 2.2 diopters (D) before surgery to -1.1 ± 1.8 D at the last follow-up visit. Mean simulated keratometry (Sim K) decreased from 45.6 ± 1.9 D to 38:9 ± 2.7 D. Mean corneal astigmatism increased from 1.3 ± 0.8 D to 2.1 ± 0.9 D. The mean surgically induced cylinder vector (calculated by vector analysis) was 1.1 ± 0.6 D. Mean surface regularity index (SRI) and surface asymmetry index (SAI) increased from 0.37 ± 0.38 and 0.32 ± 0.43 before surgery to 1.00 ± 0.32 (P < 0.001) and 0.75 ± 0.36 (P = 0.01), respectively, at the last visit. A positive correlation was observed between the decrease in mean Sim K and the increase in manifest spherical equivalent (reduction of myopia) (r = 0.77, P = 0.002), increase in SRI (r = 0.73, P = 0.005), and increase in SAI (r = 0.58, P = 0.04). The change in manifest spherical equivalent was significantly less than the change in Sim K (P < 0.001).Conclusions: Myopic ALK significantly flattens the cornea and reduces myopia. However, it induces corneal astigmatism and decreases corneal surface regularity and symmetry. The degree of myopic correction, as well as the surgically induced corneal surface irregularity and asymmetry, is positively correlated with the amount of corneal flattening derived from the surgical procedure.

Automated keratomileusis in situ: Clinical study of 142 eyes

Purpose: To compare a modified automated lamellar keratoplasty (ALK) technique that uses two blades with the original technique, which uses one blade.Setting: Buzard Eye Institute, Las Vegas, Nevada.Methods: This study comprised 142 eyes of 85 patients who had ALK: 107 using the original one-blade technique (Group 1) and 35 eyes using the modified two-blade technique (Group 2). Mean follow-up was 11 months in Group 1 and 3 months in Group 2.Results: Mean preoperative spherical equivalent was −8.93 diopters (D) ± 2.80 (SD) in Group 1 and −8.33 ± 2.80 D in Group 2. No patient had worse than 20/80 best corrected visual acuity preoperatively. Mean spherical equivalent at 1 month was −2.06 ± 2.00 D in Group 1 and −0.79 ± 1.20 D in Group 2 (P < .05). Mean postoperative spherical equivalent at last follow-up was −0.43 ± 0.90 and −0.65 ± 1.10 D, respectively. At last follow-up, 104 eyes (97%) in Group 1 and 34 (97%) in Group 2 had a spherical equivalent between +1.00 and −3.00 D, and 90 eyes (84%) in Group 1 and 27 (77%) in Group 2 had 20/40 uncorrected visual acuity. Seven eyes (7%) in Group 1 and 1 (3%) in Group 2 lost two or more lines of best corrected visual acuity at last follow-up. Three months after ALK (for equal comparison), 25 eyes (23%) in Group 1 and 3 (8%) in Group 2 required radial keratotomy; 20 (19%) and 2 (6%), respectively, needed ALK revision; and 45 eyes (42%) and 17 (47%) needed astigmatic keratotomy.Conclusions: The results suggest that ALK is capable of impressive myopic corrections across a broad range of refractive error. The procedure is not accurate enough with a single microkeratome pass and requires enhancement procedures including recuts of the bed with the microkeratome and astigmatic and radial keratotomies. Using two blades to achieve an even cut gives better spherical equivalent and best corrected visual acuity results and lower enhancement rates.

Initial results of automated lamellar keratoplasty for correction of myopia: One year follow-up

Purpose: To report our initial results with automated lamellar keratoplasty (ALK) to correct myopia and to evaluate the short-term efficacy, safety, and predictability of this procedure.Methods: A prospective series of 128 eyes of 81 consecutive patients who had ALK were reviewed for a mean follow-up of 13.6 months (range 12 to 19 months). Preoperative data, intraoperative parameters, and postoperative visual acuity, refraction, keratometric readings, and complications at 1 day, 1 week, 1, 3, and 6 months, 1 year, and last follow-up visit were used for analysis. The procedure was performed for myopia in 120 eyes (-4.50 to -13.25 diopters [D]) and for residual myopia following radial keratotomy (RK) in eight eyes (-1.75 D to -3.75 D). A hinged-flap technique was used in 17 cases (13%) once this method was introduced.Results: Preoperative mean uncorrected visual acuity was 0.04 ± 0.05 (20/500). Postoperatively (12 to 19 months), overall uncorrected visual acuity was 20/40 or better in 86.4% of eyes with a mean uncorrected acuity of 0.68 ± 0.22 (20/30); 76.2% of eyes were within 1.00 D of emmetropia and 93.6%, within 2.00 D. After the initial ALK procedure, 77% of eyes had RK or astigmatic keratotomy (AK). Among the 29 eyes with ALK alone, 86% had 20/40 or better uncorrected visual acuity, with mean uncorrected acuity and mean corrected acuity of 0.69 ± 0.21 (20/30) and 0.95 ± 0.10 (20/21), respectively; 72% of eyes were within 1.00 D of emmetropia and 90%, within 2.00 D. In 4%, astigmatism increased more than 1.00 D from the preoperative value and 4% of eyes (5/128) had persistent irregular astigmatism. Four percent of eyes (5/128) had overcorrection, with a final spherical equivalent greater than +1.00 D. Epithelial growth in the interface requiring surgical removal occurred in 2% of cases. One eye with residual myopia from a previous RK lost the cap after ALK. A homologous donor graft was performed, which resulted in 20/30 uncorrected visual acuity. Best corrected visual acuity of two lines or more was lost in 6.3% of eyes (8/128). This was caused by irregular astigmatism in 63% of cases.Conclusions: The results of our initial experience indicate that ALK is a reasonably safe, effective, and predictable procedure for correction of high myopia and myopia following previous RK. With additional enhancement with RK/AK, good visual and refractive outcome can be expected.