Fourier series harmonic analysis of corneal topography following suture removal after penetrating keratoplasty

PURPOSE: To evaluate quantitatively the influence of suture removal after penetrating keratoplasty on corneal refraction including irregular astigmatism. METHODS: Subjects were 42 eyes of 39 patients with clear corneal grafts who underwent suture removal after penetrating keratoplasty. Videokeratography data taken before and after suture removal were decomposed using Fourier harmonic analysis into spherical power, regular astigmatism, and irregular astigmatism (asymmetry and higher order irregularity). RESULTS: On average, spherical power significantly increased after suture removal (p < 0.0001, paired t test), and regular astigmatism did not change significantly (p = 0.247). Suture removal significantly decreased asymmetry (p < 0.0001) and higher order irregularity (p < 0.0001). CONCLUSIONS: Suture removal after penetrating keratoplasty induces myopic shift and reduction in irregular astigmatism of the cornea.     

Classification of corneal topography after penetrating keratoplasty

Background: Semiquantitative classification of corneal topography after penetrating keratoplasty has the potential for focusing information about the areal dioptric power of the cornea. The purpose of this study was to objectify the procedure of manual semiquantitative classification using a Fourier transform of corneal topography power data and to correlate both methods. Patients and methods: Fifty patients each (30 keratoconus, 20 Fuchs dystrophy) underwent nonmechanical trephination (excimer laser MEL60, Aesculap-Meditec, Jena) in penetrating keratoplasty. All procedures (7.5-mm trephination diameter in Fuchs, 8.0 mm in keratoconus, double-running 10–0 nylon suture) were done by one surgeon. Pre-, intra- and postoperative treatment were identical. At the follow-up examinations, the keratometric astigmatism, qualitative and quantitative criteria of the automatic videokeratography, visual acuity and refraction were assessed. Corneal topography was classified both manually and based on Fourier coefficients. Results: After a mean follow-up of 24 ± 5 months, keratometric net astigmatism was 3.0 and 2.7 D with keratoconus and Fuchs dystrophy. Corneal topography analysis showed a higher orthogonality of the bow-tie shape and less asymmetry between opposite hemimeridians with increasing follow-up after keratoplasty. The semiquantitative classification showed a statistically significant correlation with the classification based on Fourier coefficients, especially with higher astigmatism and after suture removal (P = 0.04/0.01 before/after suture removal). Discussion: After nonmechanical trephination, the semiquantitative classification of corneal topography can be synthetized using Fourier analysis of corneal dioptric power data. In the future, this method may be favored for prediction of potential best-corrected visual acuity after penetrating keratoplasty.      

Effect of disagreement between refractive, keratometric, and topographic determination of astigmatic axis on suture removal after penetrating keratoplasty

BACKGROUND/AIMS: Post-keratoplasty astigmatism can be managed by selective suture removal in the steep axis. Corneal topography, keratometry, and refraction are used to determine the steep axis for suture removal. However, often there is a disagreement between the topographically determined steep axis and sutures to be removed and that determined by keratometry and refraction. The purpose of this study was to evaluate any difference in the effect of suture removal, on visual acuity and astigmatism, in patients where such a disagreement existed. METHODS: 37 cases (from 37 patients) of selective suture removal after penetrating keratoplasty, were included. In the first group "the disagreement group" (n=15) there was disagreement between corneal topography, keratometry, and refraction regarding the axis of astigmatism and sutures to be removed. In the second group "the agreement group" (n=22) there was agreement between corneal topography, keratometry, and refraction in the determination of the astigmatic axis and sutures to be removed. Sutures were removed according to the corneal topography, at least 5 months postoperatively. Vector analysis for change in astigmatism and visual acuity after suture removal was compared between groups. RESULTS: In the disagreement group, the amount of vector corrected change in refractive, keratometric, and topographic astigmatism after suture removal was 3.45 (SD 2.34), 3.57 (1.63), and 2.83 (1. 68) dioptres, respectively. In the agreement group, the amount of vector corrected change in refractive, keratometric, and topographic astigmatism was 5.95 (3.52), 5.37 (3.29), and 4.71 (2.69) dioptres respectively. This difference in the vector corrected change in astigmatism between groups was statistically significant, p values of 0.02, 0.03, and 0.03 respectively. Visual acuity changes were more favourable in the agreement group. Improvement or no change in visual acuity occurred in 90.9% in the agreement group compared with 73.3% of the disagreement group. CONCLUSIONS: Agreement between refraction, keratometry, and topography was associated with greater change in vector corrected astigmatism and was an indicator of good prognosis. Disagreement between refraction, keratometry, and topography was associated with less vector corrected change in astigmatism, a greater probability of decrease in visual acuity, and a relatively poor outcome following suture removal. However, patients in the disagreement group still have a greater chance of improvement than worsening, following suture removal.     

Changes in post-keratoplasty astigmatism after suture removal: refraction vs tomography vs aberrometry

AIM: To analyse the changes in magnitude and orientation of astigmatism after suture removal (SR) in keratoplasty eyes as measured by refraction, tomography, and aberrometry. METHODS: Twenty-six eyes of 25 patients after optical keratoplasty requiring SR to reduce the astigmatism during the follow-up period were prospectively included. Eyes with poor quality topography scans or if there were no sutures in the steepest semi meridian were excluded. Corrected distance visual acuity (CDVA), manifest refraction, corneal tomography and aberrometry were performed on all patients before and after SR. RESULTS: The mean age of the patients was 40.8±14.4y. Penetrating keratoplasty was performed in 23 eyes (89%) and deep anterior lamellar keratoplasty was done in 3 eyes (11%). There was a statistically significant reduction in the magnitude of refractive, tomographic and aberrometry astigmatism after SR (P<0.001) at 2h after suture removal. The mean net reduction of the astigmatism was greater as measured by corneal tomography compared to refractive astigmatism (P<0.05). There was no statistically significant change in refractive astigmatism between 2h and 2mo after SR (P=0.55). Vector calculations demonstrated a greater amount of undercorrection in the tomography group and the rotational error was more towards counterclockwise direction. Mean monocular logMAR CDVA improved from 0.57 D to 0.49 D after SR (P=0.002). CONCLUSION: The net reduction in the magnitude of astigmatism after SR is greater in the tomography and aberrometry groups. With one episode of SR, there is no difference in the aberration profile.     

穿透性角膜移植手术散光的控制

目的 探讨如何有效控制穿透性角膜移植术后散光。方法 对穿透性角膜移植术后随访8个月以上的34例(37只眼)患者的散光状况进行分析，比较不同缝合方式对散光的影响，观察术后选择性拆线及连续缝线调整技术降低散光的作用。结果 不同缝合方式对术后远期散光的影响无显著性差异。选择性拆线及术后连续缝线调整能有效降低散光，4只眼术后调整缝线，3只眼散光下降，平均下降2．21D。结论 精确的手术操作及良好的缝合技术对减少术后散光极为重要，术后选择性拆线及调整连续缝线能有效降低散光。     

Conoidal fitting of corneal topography height data after excimer laser penetrating keratoplasty

PURPOSE: To demonstrate a mathematical method for approximation of discrete corneal topography height data with a biconic model surface for better appreciation of the optical performance of the graft after penetrating keratoplasty. METHODS: In this retrospective study we included 50 eyes of 50 patients (30 keratoconus; 20 Fuchs' dystrophy) undergoing nonmechanical excimer laser penetrating keratoplasty. Conventional keratometry, corneal topography (TMS-1), subjective refraction, and best spectacle-corrected visual acuity (BSCVA) were assessed preoperatively, 3 and 6 months postoperatively, and before/after suture removal. A biconic model surface was fitted to the topographic raw data (8.0-mm region of interest) minimizing the root mean square error and a set of parameters (meridional power, axis, conic constant, and approximation error) was determined. The refractive cylinder was correlated with keratometric power readings, the Simulated Keratometry (SimK) of the topography system, and the respective parameters of the model surface. RESULTS: Keratometric/SimK astigmatism increased from preoperatively (3.40/4.30 D) to 3 months (4.30/4.80 D) and decreased to 3.40/3.90 D after suture removal. Refractive cylinder/cylinder of the biconic increased slightly from 2.10/2.60 D preoperatively to 3.20/3.30 D after suture removal. The topographic cylinder SimK yielded the highest and the refractive cylinder the lowest values at each follow-up examination. Central keratometric power readings were stable before suture removal and decreased (about 1 D) due to suture removal. The conic constants in both meridional cross-sections changed from a prolate to a spherical shape in the early time course after penetrating keratoplasty and reconverted to a prolate shape after suture removal. Regarding cylinder axis, there was a significant correlation of the model surface with the refractive cylinder at all examination (P < .05) but only a mild correlation of the keratometric and SimK cylinder axis to the refractive cylinder axis at some examination stages. CONCLUSION: Approximation of corneal topography height data with a biconic model surface renders reconstruction of clinically relevant corneal topography parameters including corneal asphericity with marked data compression. The correlation of amount/axis of refractive cylinder was best represented with the model surface parameters.     

Three-axis ellipsoidal fitting of videokeratoscopic height data after penetrating keratoplasty

PURPOSE: After penetrating keratoplasty corneal topography tends to be irregular and the fitting of spectacle glasses or contact lenses may be difficult. The purpose of this study was to demonstrate a mathematical method for approximation of discrete corneal topography height data with an ellipsoid for better appreciation of the clinical outcome after PK. PATIENTS AND METHODS: In 50 eyes (30 keratoconus, 20 Fuchs' dystrophy) penetrating keratoplasty was performed using nonmechanical trephination with the excimer laser 193 nm. Main outcome measures were objective corneal astigmatism (regular keratometry, corneal topography (TMS-1)), subjective refraction and best-corrected visual acuity (VA) in a fixed postoperative gate 3 and 12 month postoperatively and after suture removal. An approximation algorithm was applied for fitting a general ellipsoidal surface (not rotationally symmetric) to raw corneal topography height data. A set of parameters (meridional power, axis and asphericity) were calculated. The root mean square error (RMS) was determined between raw topography power data and the ellipsoidal model surface within an apical distance of 3 mm. The cylinder of subjective refraction was correlated with the keratometric readings, the Simulated Keratometry (SimK) of the topography system and the respective parameters of the model surface. RESULTS: The amount of the SimK cylinder yielded higher values than keratometry and the ellipsoidal fit; subjective refraction yielded the lowest value at each follow-up interval. The ellipsoidal fit showed the best correlation to the refractive cylinder at all follow-up stages (p = 0.04 at 3, p = 0.01 at 12 months and p = 0.002 after suture removal). The axis of the best ellipsoidal fit showed a significant correlation with the axis of the refractive cylinder at all follow-up intervals (p = 0.02 at 3 months, p = 0.01 before suture removal and p = 0.002 after suture removal). The axis of the keratometric cylinder showed a mild correlation at all follow-up examinations (p = 0.05 at 3 months, p = 0.02 before suture removal and p = 0.04 after suture). The cylinder of the topographic modeling system, however, showed a significant correlation with the refractive cylinder axis only after suture removal (p = 0.04). The paracentral corneal power of SimK (45.9D at 3 months, 44.4D at 12 months and 43.0D after suture removal) exceeded the respective values of conventional keratometry (43.1D at 3 months, 42.9D at 12 months and 41.7D after suture removal) and the ellipsoidal fit (43.3D at 3 months, 43.0D at 12 months and 41.8D after suture removal). The corneal asphericity from the ellipsoidal fit reached an approximately spherical shape in radial direction (A = 1.0) in the initial time period after penetrating keratoplasty, remained stable before suture removal and decreased significantly (p = 0.02) to a final value of A = 0.86 indicating a (normal) prolate shape of the cornea. The approximation error between the raw corneal topography height data and the best ellipsoidal fit model surface was nearly unchanged before suture removal (1.8 +/- 0.7 microm at 3 months and 1.9 +/- 1.1 microm at 12 months, p = 0.30) and decreased significantly to the examination after suture removal (0.9 +/- 0.5 microm, p = 0.01). CONCLUSIONS: The approximation of corneal topography height data with an ellipsoidal model surface renders reconstruction of clinically relevant corneal topography parameters including corneal asphericity. Even in markedly irregular corneal surfaces, such as after PK, the correlation of amount/axis of refractive cylinder with the model surface parameters is more accurate than with respective SimK values of corneal topography analysis.     

Perforierende Keratoplastik mit intrastromalem Hornhautring

BACKGROUND: The purpose of the study was to evaluate the efficacy and safety of Krumeichs' intrastromal corneal ring following penetrating keratoplasty. Postoperative astigmatism and occurrence of complications were the main criteria of this study. MATERIAL AND METHODS: A total of 20 patients were included in this prospectively randomized study (10 patients with and 10 patients without corneal ring). Follow-up examinations were performed 6 weeks, 4, 12, and 18 months postoperatively, including best corrected visual acuity and Orbscan corneal topography. RESULTS: The mean follow-up time is currently 18.9+/-2.8 months. The mean astigmatism (Orbscan) is 3.9 D in the group with ring and 4.0 D in the group without a ring. Spontaneous suture rupture occurred in five patients with corneal ring. CONCLUSIONS: The use of the intrastromal corneal ring following penetrating keratoplasty caused no reduction of postoperative astigmatism. The reason for the spontaneous suture ruptures is unclear.     

Corneal steepening with final suture removal after penetrating keratoplasty

We reviewed 53 patients after they underwent penetrating keratoplasty, comparing the change in average corneal curvature before and after final suture removal 15-18 months postsurgery. In 29 eyes with keratoconus, there was a significant increase in average curvature of 3.48 diopters +/- 3.76 (p less than 0.0005). In 24 eyes with other diagnoses, there was also a significant increase in the average curvature of 3.26 diopters +/- 3.98, (p less than 0.0005). The difference between these groups was not significant. The amount of steepening correlated negatively (-.6494) with the average corneal curvature before suture removal (p less than 0.005). We found no change in the average astigmatism after suture removal; however, large changes in astigmatism occurred unpredictably with some patients. This study shows that corneal curvature after penetrating keratoplasty steepens after suture removal, particularly in flat corneas, and astigmatism may shift unpredictably.     

A comparison of penetrating keratoplasty and lamellar keratoplasty in the surgical management of keratoconus.

A retrospective study of patients who underwent keratoplasty for keratoconus was done in 100 consecutive cases, of which 50 were penetrating keratoplasty procedures, and 50 were lamellar keratoplasty procedures. Each case was done by the same surgeon in both series. Criteria for patient selection were essentially the same. Postoperative care differed primarily in the time before suture removal, being an average of ten months in the penetrating keratoplasty group and three months in the lamellar keratoplasty group. Of those patients who underwent penetrating keratoplasty, the mean best-corrected visual acuity was 6/6 (20/20-) and the average corneal astigmatism was + 5.00 diopters. Of those patients who received lamellar keratoplasty, the mean best-corrected visual acuity was 6/9 (20/30-), and the average corneal astigmatism was +3.25 diopters. The most frequent complications of both techniques were wound separations that responded well to resuturing.     

Intra-individual variability of penetrating keratoplasty outcome after excimer laser versus motorized corneal trephination

PURPOSE: To assess the intra-individual variability of outcomes after penetrating keratoplasty by comparing mechanical and nonmechanical corneal trephination. METHODS: Fifteen patients (30 eyes, 16 with keratoconus and 14 with Fuchs' dystrophy; median age at penetrating keratoplasty 56.3/53.5 years) were assessed whose trephination was performed using a motor trephine in one eye and the 193-nm excimer laser (MEL 60, Carl Zeiss-Meditec) in the other eye by one experienced surgeon. Subjective refractometry, standard keratometry, and corneal topography were used to assess best spectacle-corrected visual acuity (BSCVA); spherical equivalent refraction; keratometric and topographic central corneal power; refractive, keratometric, and topographic astigmatism; surface regularity index; surface asymmetry index; and potential visual acuity preoperatively, before first suture removal (at 1 year), and at last available follow-up after final suture removal but before additional surgery (1.3 and 1.9 years, respectively). RESULTS: Before first suture removal BSCVA was significantly higher (0.7 vs 0.5; P=.008) after excimer laser trephination. At the end of follow-up, refractive/ keratometric/topographic astigmatism (2.20/2.10/2.40 diopters [D] vs 5.00/6.00/7.10 D) and surface regularity index (0.8 vs 1.1) were significantly lower (P=.02, P=.005, P=.01, and P=.03, respectively) and potential visual acuity was significantly higher (0.9/0.6; P=.02) after excimer laser trephination. CONCLUSIONS: During long-term follow-up, all-sutures-out postkeratoplasty astigmatism and surface regularity are superior in the eye where nonmechanical excimer laser was applied in contrast to the fellow eye with motor trephination in the same individual.     

Changes in corneal power and refraction due to sequential suture removal following nonmechanical penetrating keratoplasty in eyes with keratoconus

PURPOSE: To assess the changes in corneal power and refraction due to sequential suture removal after penetrating keratoplasty (PK). DESIGN: Retrospective consecutive case series. METHODS: setting: Clinical practice. study population: We studied 67 phakic keratoconus eyes (central excimer laser trephination, primary keratoplasty, graft/recipient diameter 8.1/8.0 mm; double running suture) in this longitudinal study. main outcome measures: Zeiss keratometry (equivalent power (KEQ), astigmatism (KAST)), corneal topography (equivalent power (TEQ), astigmatism (TAST)) and subjective refractometry (spherical equivalent (SEQ), refractive cylinder (RAST)) were assessed with sutures in place (interval 1), with one suture out (interval 2), and with all sutures out (interval 3). observation procedure: Corneal power and refraction was decomposed into vector components and the changes were derived between time stages. RESULTS: The mean follow-up period was 3.9+/-1.7 years. At interval 1, the axes of KAST/TAST/RAST were almost randomly distributed. At interval 2, the with/against the rule component of KAST/TAST/RAST decreased slightly and the oblique component increased significantly, so that the axes tended to have a preferred oblique direction. At interval 3, the with/against the rule component of KAST/TAST/RAST increased slightly and the oblique component decreased significantly, so that the with/against the rule component exceeded the oblique component by approximately 23%/28%/25%. Median KEQ/TEQ/SEQ changed by 0.64/0.62/-1.11 diopters (interval 1 to interval 2) and by -0.85/-0.90/1.56 diopters (interval 2 to interval 3). CONCLUSIONS: As a result of removal of the first running suture, corneal astigmatism as well as the refractive cylinder tend to oblique axes. As a result of removal of the second running suture, the final corneal astigmatism and refractive cylinder tend to orientation axes with/against the rule.     

Effects of penetrating keratoplasty suture removal on corneal topography and refraction

PURPOSE: To study the refractive and topographic modifications induced by penetrating keratoplasty suture removal. METHODS: We retrospectively studied 50 corneas from 50 patients who had undergone penetrating keratoplasty. All of the eyes were examined before and after all sutures were removed at 10.8+/-4.7 months and 20.3+/-7.9 months after keratoplasty. Subjective refraction, best spectacle-corrected visual acuity (LogMAR units), and corneal topography (EyeSys 2000R device) were recorded. RESULTS: Suture removal decreased the subjective cylinder by an average of 0.91+/-2.32 D (p = 0.004) and modified the corneal topographic pattern (p = 0.03) and shape (p < 0.001) distribution. The change in subjective cylinder correlated with the variation of the steepest meridian power (r(s) = 0.46; p < 0.001). It correlated with the change in topographic pattern (r(s) = 0.59; p < 0.001). The subjective spherical equivalent increased (hyperopization) by an average of 0.61+/-2.24 D (p = 0.01). After suture removal, the prolate shape was less frequent, and the oblate shape was more frequent than before suture removal. Best spectacle-corrected visual acuity increased by an average of 0.8+/-2.0 lines (p = 0.004). The change in subjective cylinder correlated with the change in visual acuity (r(s) = 0.36; p = 0.006). CONCLUSION: Suture removal modifies the corneal topographic pattern and shape. It decreases the subjective cylinder and induces an hyperopization. Visual-acuity improvement after suture removal mainly is explained by the decrease in astigmatism. Suture removal seems particularly helpful in corneas with a bow-tie pattern.     

Photokeratoscopy in fitting contact lens after penetrating keratoplasty.

The formula based on keratometric readings which is generally used is unsatisfactory for fitting contact lenses after penetrating keratoplasty, possibly owing to lack of information on the peripheral corneal toricity. In these studies a photokeratoscope was used to examine the entire graft topography. In all cases the corneal configuration became more normal after suture removal, but a considerable toricity still remained, especially near the graft-host junction. One month after removal of sutures spherical hard contact lenses (polymethylmethacrylate, PMMA) were fitted to 30 patients in accordance with data obtained by computerised analysis of the photokeratograms. Of the 30 patients (contact lens wearers) 27 (90%) obtained a stable vision of better than 20/30 for eight hours daily, and 24 (80%) achieved a stable vision of 20/20 for their full waking hours. After one year the contact lens wearers showed a significant decrease in the extent of astigmatism when compared with the non-contact-lens wearers (10 patients). These results suggest that the photokeratoscope can be more useful than ordinary keratometers in fitting contact lenses after keratoplasty, and that hard contact lenses have moulding effects on the graft topography.     

Influence of suture regularity on corneal astigmatism after penetrating keratoplasty

Purpose: To investigate whether suture regularity affects corneal astigmatism after keratoplasty. Methods: Twenty‐one patients undergoing penetrating keratoplasty for various corneal diseases were included in the study. The grafts were sutured in place using a single‐running Nylon 10‐0 suture, taking 24 bites. Immediately after surgery, standard calibrated images of the grafted eye were captured and stored. Using a dedicated image analysis programme, stitches and needle points were identified, and a number of suture regularity variables were calculated. Corneal topographic images were obtained before suture removal (12 months after surgery) and 3 months after suture removal (18 months after surgery). Topographic measures of astigmatism [surface regularity (SRI), surface asymmetry index (SAI) and simulated keratometric astigmatism] were calculated and correlated with the computed suture regularity variables. Results: The average stitch length was 3.04 ± 0.28 mm and the distance between the outer needle points was 2.53 ± 0.09 mm. The SRI was 1.26 ± 0.36 and the SAI was 1.59 ± 0.67 after 12 months; these decreased to 1.03 ± 0.48 and 0.92 ± 0.46 after 18 months, respectively. Corneal astigmatism was 6.38 ± 2.99 and 5.87 ± 3.13 dioptres after 12 and 18 months, respectively. Suture regularity did not affect SAI, SRI or corneal astigmatism significantly 12 months after surgery. Eighteen months after surgery (3 months after suture removal), the standard deviation on the original stitch length was found to significantly increase corneal astigmatism. In addition, the size of the counter‐clockwise angle between stitch and graft radian was correlated significantly with a lower SRI. Conclusion: The origin of corneal astigmatism after penetrating keratoplasty is multifaceted. Regular stitch length and stitch advancement on the surface appears to improve the optical quality of the graft after suture removal. Factors such as stitch depth, suture tension and variations in wound construction might also be important predictors of corneal astigmatism after penetrating keratoplasty.     

Change in refraction and topography after penetrating keratoplasty suture removal

PURPOSE: To study the refractive and topographic modifications induced by penetrating keratoplasty suture removal. METHODS: We prospectively studied 80 corneas from 80 patients who had undergone penetrating keratoplasty. All of the eyes were examined before and after all sutures were removed, respectively at 10.9 5.1 months and 21.5 9.6 months after keratoplasty. Subjective refraction, best spectacle-corrected visual acuity (LogMAR units), keratometry, and corneal topography using the EyeSys 2000((R)) device (axial tangential and refractive power) were recorded. Topographies were classified according to the pattern (Bogan classification) and the asphericity shape (prolate and oblate). RESULTS: Best spectacle-corrected visual acuity (Log MAR units) increased significantly after suture removal (1.1 1.9 lines, plt; 0.001). Suture removal decreased the subjective cylinder (5.01 D 2.06 with suture, 4.11 2.08 without suture; p=0.009). The change in subjective cylinder correlated with the change in topographic pattern(s)=0.67 p<0.001). Conversely to the "bow tie" patterns, the other topographic patterns were more frequent after suture removal. The change in visual acuity was essentially explained by the change in subjective cylinder(s)=0.40 p=0.002). The average central corneal power decreased significantly after suture removal by 0.83 to 1.81 D (p<0.001), whereas the subjective spherical equivalent increased (hyperopization) (-4.07D 3.73 with suture, -3.48 3.40 without suture; p=0.02). The change in central corneal power significantly correlated with the change in subjective spherical equivalent (r(s)()>0.30 plt; 0.001). The corneal power of the mid-periphery did not significantly change after suture removal. Suture removal significantly modified the asphericity shape distribution. (majority of prolate shape with suture, majority of oblate shape without suture, p<0.001). CONCLUSION: Keratoplasty sutures induce a central bulge in the corneal graft. Suture removal induces a decrease in the subjective cylinder and it increases the subjective spherical equivalent (hyperopization) through a decrease in the central corneal power. Suture removal modifies the corneal topographic pattern and shape. Visual acuity improvement after suture removal is mainly explained by the decrease in subjective astigmatism.     

Central penetrating keratoplasty with peripheral intrastromal tuck

PURPOSE: To report a new technique of central penetrating keratoplasty with peripheral intrastromal tuck in cases of chronic corneal decompensation. METHODS: Central penetrating keratoplasty with peripheral intrastromal tuck was undertaken in 8 eyes with chronic corneal decompensation. An 8-mm donor tissue with a peripheral flange of 2 mm was fashioned and sutured into a 7.5-mm recipient bed having a 2-mm intralamellar pocket. Sixteen full-thickness interrupted sutures were passed. Suture removal was possible as early as 1 month, and all sutures were removed by 4 months. RESULTS: Postoperative BCVA improved to 20/40 to 20/80 in all eyes, and astigmatism was <4 diopters in all cases at the last follow-up, which ranged from 5 to 16 months. CONCLUSIONS: Central penetrating keratoplasty with peripheral intrastromal tuck is a useful technique because it allows early suture removal and visual rehabilitation.     

Surgical treatment of advanced pellucid marginal degeneration

PURPOSE: To determine the efficacy of simultaneous peripheral crescentic lamellar keratoplasty (LK) and central penetrating keratoplasty (PK) for advanced pellucid marginal degeneration (PMD). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Five patients with advanced PMD. METHOD: Simultaneous peripheral crescentic LK and central PK followed by selective suture removal and astigmatic keratotomy in the postoperative period. MAIN OUTCOME MEASURES: These included interval of time required for visual rehabilitation, best spectacle-corrected visual acuity achieved, and amount of corneal astigmatism, as measured by videokeratography. Measuring the change in corneal astigmatism by videokeratography over the subsequent follow-up period after spectacle correction had been prescribed assessed stability of the achieved refraction. RESULTS: Visual acuity results were 20/40 in three eyes, 20/80 in one eye, and 20/400 in one eye. The latter two had decreased acuity from posterior subcapsular cataract formation, which may have been caused by topical steroid use. The time required for visual rehabilitation ranged from 5.13 to 10.93 (mean, 9.92) months, and the amount of corneal astigmatism at the end of this period ranged from 0.3 diopters (D) to 5.3 D. A tendency for an increase in "with the rule astigmatism" after the rehabilitation period was noted. Two patients had elevations of intraocular pressure that responded to reduction in topical steroid dose. CONCLUSIONS: The short-term results with this technique are excellent in that it provides early and stable visual rehabilitation in patients with advanced PMD. Low to moderate levels of postkeratoplasty astigmatism were achieved in all the eyes treated. The usual tendency of an increase in "against the rule astigmatism" that occurs when PK alone is done for PMD was eliminated.     

Management of postkeratoplasty astigmatism.

Many factors have led to the improved success rate for clear corneal grafts after penetrating keratoplasty. Unfortunately, postoperative corneal astigmatism commonly occurs and can produce significant visual impairment. Astigmatic correction may include spectacle correction or contact lenses, but if this fails, then surgical options are considered. Refractive surgical techniques such as suture removal or adjustment, relaxing incisions, wedge resections, and photorefractive keratectomy or laser in situ keratomileusis can dramatically reduce postoperative astigmatism after penetrating keratoplasty and lead to improved, functional vision. However, significant variability between results in individual patients can occur. So although general guidelines are useful, it is important to individualize and modify the planned surgery based on qualitative keratoscopy and corneal topography for the initial and subsequent astigmatic corrections.     

Clinical results of 123 femtosecond laser-assisted penetrating keratoplasties

Background

Postoperative astigmatism following penetrating keratoplasty is a major problem after corneal transplantation. The main goal of new trephination techniques such as femtosecond laser or excimer-laser trephination is to improve refractive and visual outcomes. The femtosecond laser technique makes profiled corneal trephinations such as the top hat or mushroom profile possible. We present the postoperative outcome of femtosecond laser-assisted penetrating keratoplasties.

Methods

We performed 123 femtosecond laser-assisted penetrating keratoplasties in 119 patients. The main outcome measures were intraoperative specifics, astigmatism, and irregularity in Orbscan corneal topography, as well as the occurrence of immune reactions and side-effects.

Results

All sutures have been removed in 49 of these 123 eyes. Their mean follow-up was 13.9?±?4.5 months. Time to complete suture removal (n?=?49) was 12.0?±?3.7 months in the mushroom group and 9.8?±?2.1 months in the top hat group. Mean astigmatism in Orbscan topography was 6.4?±?3.0 diopters in the mushroom and 5.8?±?4.6 diopters in the top hat group (all sutures out).

Conclusions

Femtosecond laser-assisted penetrating keratoplasty is a safe surgical technique. Due to the steps in profiled trephinations, the wound area is larger and theoretically the wound healing is, thus, faster and more stable. Complete suture removal is possible at an earlier time point compared to conventional penetrating keratoplasty. However, refractive results are not superior to those following conventional trephination.