[Femtosecond laser-assisted keratoplasties]. / Kératoplasties assistées par laser femtoseconde.

Femtosecond laser technology in ophthalmology is not only used for refractive surgery (LASIK flaps), but also now for lamellar and penetrating keratoplasties. This is not surprising when one knows that femtosecond lasers can cut corneal tissue in all directions with micrometric accuracy. Lamellar dissection of the cornea is very facilitated with femtosecond laser because it is quicker and more reproducible. However, predescemet dissection is not yet possible, and although the interfaces are smooth, the visual benefits of this technology has still to be proven. Another field of application of femtosecond lasers is their use to perform the cut for penetrating keratoplasties. Different shapes of non vertical cuts are currently assessed in order to reduce the incidence of complications such as induced astigmatism and wound dehiscence, and to improve the visual outcome.

[Correlation between corneal topography and subjective refraction in idiopathic and surgery-induced astigmatism]. / Corrélation entre la réfraction et la topographie cornéenne dans les astigmatismes idiopathiques et post-chirurgicaux.

PURPOSE: To study the correlation between subjective refraction and corneal topography. To compare the topographic analysis of surgically induced astigmatism (cataract and penetrating keratoplasty) with that of idiopathic astigmatism. METHODS: Subjective astigmatism, subjective spherical equivalent, best spectacle-corrected visual acuity (LogMAR units), and videokeratoscopy using the EyeSys 2000((R)) device (axial, tangential, and refractive power) were recorded in 100 eyes with idiopathic astigmatism, 100 eyes after cataract surgery, and 100 eyes after penetrating keratoplasty. Topographies were classified according to pattern (Bogan classification) and asphericity (shape factor: prolate or oblate). RESULTS: The asphericity shape distribution was significantly different between the 3 groups (p<0.001). The shape of idiopathic astigmatism was almost always prolate (90%) whereas the oblate shape was more frequent in the penetrating keratoplasty group (75%). There was no significant difference in topographic pattern distribution between the 3 groups (p=0.11). The asymmetric bow tie pattern was the most common topographic pattern. Topography pattern classification was significantly correlated with the subjective astigmatic cylinder. (r(s)=0.60, p<0.001). Unlike the round and oval patterns, the bow tie pattern was associated with the high subjective cylinder. Correlation between the subjective cylinder, the refractive power cylinder, and the axial power cylinder was strong (r(s)=0.92 p<0.001), but it was weak for the tangential power cylinder (r(s)=0.72 p<0.001). The correlation between the subjective spherical equivalent and central cornea power was poor (r(s)<0.37, p<0.001). Subjective astigmatic cylinder showed the strongest correlation with best spectacle-corrected visual acuity (r(s)=0.70, p<0.001), whereas the predicted corneal acuity, corneal uniformity index, asphericity, and refractive power symmetry index were poorly correlated with it (r(s)<0.54, p<0.001). CONCLUSION: Despite the difference in the asphericity shape, the topographic pattern was similar in the 3 groups. The pattern type was significantly correlated with the subjective astigmatic cylinder. Topographic indices failed to predict visual acuity, while the subjective cylinder showed a strong correlation with visual acuity.

Automated keratoconus detection using the EyeSys videokeratoscope.

PURPOSE: To evaluate the effectiveness of indices derived from the EyeSys System 2000 in detecting keratoconic corneas. SETTING: Department of Ophthalmology, Hôpital Saint Antoine, Paris VI University, Paris, France. METHODS: Topographies of 208 corneas were evaluated. The corneas were from 8 groups of patients classified by the following diagnoses: normal, regular astigmatism, cataract, radial keratotomy, photorefractive keratectomy, myopic keratomileusis, penetrating keratoplasty (PKP), and keratoconus. Nine statistical indices derived from EyeSys data, 2 Holladay Diagnosis Summary indices (coefficient of uniformity and coefficient of asphericity [Asph]), and our refractive power symmetry index were studied. A training set of 104 corneas was used to determine the most efficient threshold value of each index based on sensitivity and specificity curves. Decision trees combining 2 indices were generated. Sensitivity and specificity were calculated in a validation set composed of the remaining 104 corneas. RESULTS: Based on the results of the training set, the optimum indices were SDSD (standard deviation of the standard deviations of the radii of curvature of each ring) and Asph. In the validation set, the decision tree using these indices featured 88.5% sensitivity and 94.9% specificity; the 4 false-positive cases were in corneas in the PKP group of patients. CONCLUSIONS: Clinically apparent keratoconus can be detected among normal corneas and irregular corneal shape patterns using the EyeSys System 2000 data and a decision tree combining 2 indices.

[Comparison of EyeSys videokeratoscope algorithms in the evaluation of idiopathic and postoperative astigmatism]. / Comparaison des algorithmes du vidéokératoscope EyeSys pour l'évaluation de l'astigmatisme idiopathique et post-chirurgical.

PURPOSE: To compare the accuracy and reproducibility of the Eye Sys videokeratoscope algorithms for analyzing idiopathic and surgery-induced astigmatism analysis. METHODS: Refractive astigmatism, videokeratoscopy (axial, tangential and refractive power), autorefractometry, autokeratometry, and keratometry were recorded in 20 patients with idiopathic astigmatism, 40 patients who had undergone cataract surgery and 40 patients who had undergone penetrating keratoplasty. For each eye, 2 successive videokeratoscopy were recorded. RESULTS: Both cylinder and axis provided by the tangential algorithm are significantly less reproducible than the cylinder and axis provided by the axial and refractive algorithms (P < 0.001). Cylinders provided by the axial and refractive algorithms showed a stronger correlation with subjective cylinder (rs > 0.89; p < 0.001) than the cylinder provided by the tangential algorithm (rs = 0.66; p < 0.001). Both keratometric axis and autokeratometric axis showed the strongest correlation with subjective axis (rs > 0.92; p < 0.001). The accuracy and reproducibility were higher for the topographic "bow tie" patterns than for the other topographic patterns. CONCLUSION: The axial and refractive algorithms of the Eye Sys videokeratoscope are more accurate and reproducible than the tangential algorithm for analyzing idiopathic or surgery-induced astigmatism.

Prediction of spectacle-corrected visual acuity using videokeratography.

PURPOSE: Our aim was to improve prediction of spectacle-corrected visual acuity (SCVA) using indices derived from the EyeSys System 2000 data (version 3.1). METHODS: We studied corneal topography in 182 eyes from 8 groups of patients. Holladay Diagnostic Summary indices were recorded. Nine statistical indices calculated with the first 8-ring data and refractive power symmetry index were also studied. Correlation with SCVA (LogMAR units) was studied by means of Pearson's regression. Multiple linear regression was used to obtain linear equations combining several indices. RESULTS: At a univariate level, total astigmatism cylinder showed the strongest correlation with SCVA (r = .63, P = .0001). At a multivariate level, the predicted visual acuity obtained by linear equation combining the asphericity coefficient, the predicted corneal acuity, the mean of the means, and the total astigmatism cylinder was closely associated with SCVA (r = .72, P = .0001). It was identical to SCVA in 58.2% of the cases, within one line in 75.8%, and within two lines in 91.2%. CONCLUSION: Multiple linear regression resulted in the best prediction of spectacle-corrected visual acuity, giving notable improvement in prediction of spectacle-corrected visual acuity as compared to the predicted corneal acuity available in the EyeSys System 2000.

Surgical correction of postkeratoplasty astigmatism with the Hanna arcitome.

PURPOSE: To report the results of arcuate keratotomy performed with the Hanna arcitome in patients with postkeratoplasty astigmatism. SETTING: Department of Ophthalmology, Saint-Antoine Hospital, Paris VI University, Paris, France. METHODS: This retrospective study comprised 22 eyes (22 patients) with postkeratoplasty astigmatism. Paired symmetrical arcuate keratotomy was performed with the Hanna arcitome. Outcome measures included refraction, videokeratography, and keratometry. RESULTS: At 6.6 months +/- 8.9 (SD) after surgery, the mean increase in best spectacle-corrected visual acuity (BSCVA) was 2.1 +/- 2.4 lines. Thirteen eyes gained 2 lines or more of BSCVA, and 15 gained 3 lines or more of uncorrected visual acuity. Two patients had a decrease in BSCVA: 1 had lens opacification unrelated to arcuate keratotomy and 1, increased corneal irregularity. Mean refractive astigmatism was 6.94 +/- 2.11 diopters (D) preoperatively and 3.85 +/- 1.95 D postoperatively (P < .01). Mean change in keratometric astigmatism was -51 +/- 36%. Astigmatism decreased in 21 eyes as measured by manifest refraction, keratometry, and videokeratography; it increased in 1 cornea with a microperforation. CONCLUSIONS: The results of arcuate keratotomy performed with the Hanna arcitome were comparable to those with freehand relaxing incisions. The instrument made safer and more uniform arcuate incisions than a freehand technique.

[Surgical treatment of astigmatism caused by penetrating keratoplasty using the Hanna arcuate keratome]. / Correction chirurgicale de l'astigmatisme induit par la kératoplastie transfixiante a l'aide du kératome arciforme de Hanna.

PURPOSE: High postkeratoplasty astigmatism is a common postoperative complication which can limit the final functional result. Arcuate incisions are a possible surgical treatment. They can be performed with the arcuate keratome which provides regular incisions. The aim of this study was to evaluate the results obtained with this device in the correction of high postkeratoplasty astigmatism. METHODS: We retrospectively studied ten eyes operated for high postkeratoplasty astigmatism with the Hanna arcuate keratome. Arcuate keratomy procedures were performed on the graft button in all. Before surgery, mean uncorrected visual acuity was 0.07 +/- 0.05. Best spectacle-corrected visual acuity was 0.33 +/- 0.20 and mean subjective cylinder was 6.1 +/- 1.71 D. RESULTS: After one month postoperatively, the mean best spectacle-corrected visual acuity (0.45 +/- 0.20) was significantly improved (p < 5%) and mean subjective cylinder (2.85 +/- 1.29 D) was significantly decreased (p < 5%). Vector analysis showed a 5.59 D (+/- 3.63) mean astigmatism correction. Modifications of the spherical equivalent were not statistically significant. Astigmatism irregularity was not modified. CONCLUSION: Arcuate keratotomy carried out with the Hanna arcuate keratome is effective in reducing high postkeratoplasty astigmatism. It is easier to perform than the standard manual technique. However, astigmatism correction predictibility should be improved.