Fabrizio I. Camesasca

Prevention of corneal ectasia in laser in situ keratomileusis.

PURPOSEnEctasia after laser in situ keratomileusis (LASIK) is a rare but serious complication. Prevention includes proper patient selection with detection of those at particular risk. Causes of ectasia include predisposition, excessive ablation with less than 250 microm of residual stromal bed, thicker than normal flap, irregular corneal thickness, and different ablation rates.nnnMETHODSnWe evaluated corneal curvature patterns and their relationship to corneal topography and pachymetry maps.nnnRESULTSnCorneal topography (axial, tangential, and altimetric) and pachymetry map characteristics of normally astigmatic corneas, keratoconus, false-positive and false-negative cases, as well as contact lens-induced warpage are discussed.nnnCONCLUSIONSnPreoperative pachymetry maps for LASIK surgery allow accurate case selection through detection of borderline cases, and provide important documentation of preoperative status, as well as useful information for improving surgical strategy. Another important parameter is the asphericity index.

Butterfly laser epithelial keratomileusis for myopia.

PURPOSEnDecreased epithelial viability is a postoperative complication of standard laser epithelial keratomileusis (LASEK) that hampers rapid recovery, and causes reduced visual acuity as well as discomfort. We present a new LASEK technique that, by increasing epithelial viability, reduces the occurrence of these complications.nnnMETHODSnIn a preliminary series of patients, conventional LASEK was performed in one eye, and Butterfly LASEK in the fellow eye. In Butterfly LASEK, a thin paracentral epithelial line, from 8 to 11 oclock was removed, and 20% alcohol plus BSS solution was placed in contact with the cornea for 5 to 30 seconds. A specially designed spatula allowed separation of epithelium from Bowmans layer, proceeding from center to periphery on both sides. A special retractor was used to move the two flaps of loose epithelium toward the limbus. After drying the surface, excimer laser ablation was performed with the Nidek EC-5000 excimer laser. Smoothing with masking solution was then carried out, followed by flap replacement and overlapping.nnnRESULTSnWe treated 70 eyes of 35 patients with Butterfly LASEK. Preoperative mean spherical equivalent refraction was -5.30 +/- 3.70 D. At 12 months after surgery, mean spherical equivalent refraction was -0.10 +/- 0.40 D, and no lines of BSCVA were lost. Ninety percent of patients preferred Butterfly LASEK to conventional LASEK because of increased comfort. At 12 months, no patient had more than trace haze, and in 96.2%, corneas were completely clear.nnnCONCLUSIONSnButterfly LASEK is aimed at preserving the limbal connection of epithelial stem cells and limbal vascular connections. Improved epithelial viability is thus achieved, with faster postoperative recovery.

Long-term follow-up of ultrathin corneas after surface retreatment with phototherapeutic keratectomy.

Purpose: To evaluate visual acuity and long‐term stability after phototherapeutic keratectomy (PTK) in patients with corneal thickness less than 400 μm and cornea‐related vision problems. Setting: Department of Ophthalmology, Istituto Clinico Humanitas, Rozzano−Milan, Italy. Methods: This retrospective study comprised 48 eyes that had PTK for complications after photorefractive keratectomy that removed more than 200 μm of tissue. Phototherapeutic keratectomy was performed with the Nidek EC‐5000 excimer laser with 10 Hz frequency, intraoperative topography, and masking fluid over an ablation diameter of 10.0 mm. The follow‐up was 5 years. The mean preoperative best spectacle‐corrected visual acuity (BSCVA) was 0.2 ± 0.09 (SD) with −2.53 ± 2.34 diopters (D), and the mean pachymetry was 390 ± 38 μm. The efficacy parameters were pachymetry and visual acuity at 1 year and the stability parameters, optical refraction, corneal curvature (calculated as the mean curvature over the entire 3.0 mm and 5.0 mm central zones), and pachymetry from 1 to 5 years. Results: At 1 year, the mean BSCVA was 0.6 ± 0.72 with −2.15 ± 1.67 D and the mean pachymetry, 341 ± 40 μm. At 5 years, the mean BSCVA was 0.7 ± 0.15 with −2.33 ± 1.12 D and the mean pachymetry, 339 ± 48 μm. In all patients, there was an improvement of 4 or more Snellen lines. Statistical evaluation of refraction and corneal curvature values at 1 and 5 years indicated no statistically significant differences. Conclusions: After PTK in eyes with ultrathin corneas, there was significant improvement in BSCVA and long‐term stability of the optical refraction, corneal curvature, and pachymetry. In selected cases, 10.0 mm ablation zone PTK may be an alternative to penetrating keratoplasty, offering long‐term corneal stability.

The role of amino acids in corneal stromal healing: A method for evaluating cellular density and extracellular matrix distribution

PURPOSEnTo evaluate how amino acid supplementation influences the response of corneal stromal keratocytes and other components of the corneal stroma.nnnMETHODSnWe compared two groups of patients undergoing cataract surgery. Each group included 20 eyes of 20 patients. Patients in Group 1 were treated with amino acids for 15 days before surgery, and patients in Group 2 did not receive amino acids (control). To evaluate differences and change in corneal stroma, we analyzed all of the operated corneas with confocal microscopy. The confocal images were then analyzed with a new method for measurement of corneal structure based on fractal dimension calculation. This led to a numerical value, D index (fractal surface dimension), an objective measurement of corneal stromal characteristics. This index is related to three factors: keratocyte density, stromal distribution pattern, and intercellular matrix structure.nnnRESULTSnPatients in the preoperative amino acid group showed higher keratocyte density values than those in the control group. We observed differences in cell distribution patterns and intercellular matrix structures between groups. Amino acid-treated patients had a corneal stroma with a D index value 10% higher than control group patients.nnnCONCLUSIONSnWe hypothesized that preoperative oral supplements with amino acids may change the corneal stroma structure by increasing keratocyte density and modifying the intercellular matrix. A new method for the measurement of these changes was applied, which provides quantification of the stromal structure complexity with a single numerical value.

Statistical Analysis of Physiological Aberrations of the Cornea

PURPOSEnTo determine corneal aberrometric values in a normal population.nnnMETHODSnCorneal topography from a group of 4340 patients was retrospectively evaluated. Exclusion criteria were applied in order to select a population with good visual acuity, no previous ocular surgery, no contact lens influence, and no corneal disease. Aberrometric analysis of the corneal wavefront derived from the topographical data of the selected population was performed. Topography from 500 patients (1000 eyes) was selected for Zernike analysis of the corneal surface, with coefficients derived up to the tenth order.nnnRESULTSnCorneal surface aberration values related to different pupil diameter were determined.nnnCONCLUSIONnThis preliminary study provided reference values for corneal aberrations in the normal population.

Custom phototherapeutic keratectomy with intraoperative topography.

PURPOSEnTreatment of highly aberrated eyes with opacities or irregularities consequent to previous refractive treatment, ulcers, keratitis, trauma, or corneal dystrophies remains a challenge for refractive surgeons. We evaluated the results of custom phototherapeutic keratectomy (CPK) with intraoperative corneal topography-based aberrometry and custom ablation in highly aberrated eyes.nnnMETHODSnWe prospectively evaluated eyes undergoing custom phototherapeutic keratectomy (CPK) with custom ablation for corneal opacities and/or irregularities due to previous refractive treatment, keratitis, trauma, or dystrophies. Customization was planned according to corneal topography-based aberrometry, performed intraoperatively after removal of corneal epithelium.nnnRESULTSnWe treated 35 eyes of 34 patients. Mean preoperative haze was 1.6 +/- 1.4 in eyes with previous refractive surgery. Mean preoperative pachymetry was 425.7 +/- 119.3 microm. Mean preoperative spherical equivalent refraction was -1.60 +/- 3.65 D ranging from -9.38 to +10.00 D. No eye reached 20/15 best spectacle-corrected visual acuity (BSCVA), and only 63% could see 20/30 BSCVA. At final 6-month examination, mean spherical equivalent refraction was -0.71 +/- 4.01 D, ranging from -11.25 to +5.25 D. All eyes reached 20/30 or better BSCVA, and 19% had 20/15 or better BSCVA.nnnCONCLUSIONSnIntraoperative, epithelium-free topography-based corneal aberrometry proved to be a feasible option for custom ablation in highly aberrated eyes. This approach widens the applications of PTK, providing a new procedure, custom PTK, that can be a successful solution for eyes that would otherwise require penetrating keratoplasty.

One-year Results of Butterfly Laser Epithelial Keratomileusis

PURPOSEnTo evaluate the risks, complications, and refractive results at 1 year after modified laser epithelial keratomileusis (Butterfly LASEK).nnnMETHODSnIn a non-randomized prospective study of 773 eyes (452 patients; mean age 34.3 +/- 16.5 years, mean preoperative spherical equivalent refraction -5.30 +/- 3.70 D; mean sphere -4.80 +/- 3.60 D; mean cylinder -1.00 +/- 1.40 D; range -22.50 to +5.50 D), we used a modified LASEK technique and evaluated complications and refractive results at 1 year. The technique is based on the formation of the epithelial flap utilizing alcohol (20% diluted solution applied on the epithelium for 5 to 30 seconds), paracentral abrasion, blunt dissection of the epithelium from the underlying plane; the epithelium is then separated by means of a specially designed retractor. Ablation was performed with a Nidek EC-5000 excimer laser, followed by smoothing and repositioning of the epithelial flap.nnnRESULTSnAfter 1 year, we analyzed the results of 542 (70.1%) treated eyes with the following outcome: mean postoperative spherical equivalent refraction -0.20 +/- 1.40 D; mean sphere -0.10 +/- 1.30 D; mean cylinder -0.10 +/- 0.60 D; range -2.50 to +0.75 D. In 83.0% of treated eyes, achieved refraction was within +/-0.50 D of planned correction, with uncorrected visual acuity greater than or equal to 1.2 in 19.0% of treated eyes, greater than or equal to 1.0 in 56.0%, and greater than or equal to 0.8 in 19%. Concerning visual acuity, 0.3% of eyes lost 1 line, 49.8% of eyes had no change; 41.8% gained 1 line, 9.8% gained 2 lines, and 1.6% gained more than 2 lines.nnnCONCLUSIONnOne-year results of this preliminary study showed that Butterfly LASEK was easy to perform, safe, and led to excellent long-term refractive results.

Applications of Confocal Microscopy in Refractive Surgery

PURPOSEnTo evaluate applications of the Confoscan 2.0, a computerized confocal optical microscopy system by Nidek, in refractive surgery.nnnMETHODSnWe used the Confoscan 2.0 to evaluate the tissue reparative response after PRK, LASEK, and LASIK in 60 eyes of 40 patients. Confoscan 2.0 provided highly detailed images of the corneal layers, up to the cellular level. Furthermore, it measured corneal thickness as well as precise positioning of each single recorded corneal layer. The Confoscan was also used to analyse the LASIK flap.nnnRESULTSnFindings in the transition zone between epithelium and anterior stroma in PRK and LASEK eyes were divided into two groups: Group 1, with marked hyper-reflectivity, and Group 2, with less hyper-reflectivity, similar to normal eyes. Group 2 eyes belonged to patients that underwent smoothing with a masking solution after ablation. Group 1 eyes received no smoothing. In LASIK eyes, we evaluated the quality of the flap interface. Hyper-reflecting specks could be observed in the interface, showing a tendency to decrease over time. Depth of the LASIK flap was measured, and showed variable thickness with all microkeratomes tested.nnnCONCLUSIONnWe hypothesize that a more regular corneal surface, obtained with smoothing in PRK and LASEK, allows a better reparative response after refractive surgery. In LASIK eyes, the Confoscan provided precise measurement of the residual stromal bed, information particularly valuable for the prevention of ectasia in retreatments.

Use of Amino Acids in Refractive Surgery

PURPOSEnTo assess the influence of amino acid supplements on corneal fibroblast activity during corneal healing in patients with chronic ulcers, as well as after refractive surgery when delayed re-epithelialization had been observed in the fellow eye.nnnMETHODSnStudies were conducted in vitro on eye bank eyes, and in vivo. In vitro cultures of rabbit corneal fibroblasts were enriched with progressively higher concentrations of amino acids. The human eye bank cornea study involved corneal epithelium removal, with corneas kept for 7 days in standard storage medium, either simple or enriched with amino acids. Clinical studies included treatment of two groups: Group 1 included six eyes of six patients with chronic epithelial defects, resistant to usual treatment; Group 2 included 21 eyes of 21 patients with delayed re-epithelialization after PRK in the first eye (12 +/- 3 days). Group 1 was treated for 1 month, and Group 2 received treatment preoperatively and postoperatively after surgery in the fellow eye until re-epithelialization was achieved. All patients received 13 amino acids and Vitamin C in three tablets, three times per day.nnnRESULTSnCultures of rabbit corneal fibroblasts showed that progressively increasing amino acid supplements led to an increase in the percentage of fibroblasts. De-epithelialized human eye bank corneas incubated with amino acids showed thicker and better organized re-epithelialization when compared to corneas incubated in simple standard storage media. In the clinical study, five eyes in Group 1 showed substantial improvement, one eyes remained unchanged. All eyes in Group 2 showed complete re-epithelialization within 60 hours after surgery.nnnCONCLUSIONnResults suggest improvement of re-epithelialization when an increase of serum and tear film amino acids is obtained through oral administration.

Decentration After Refractive Surgery

PURPOSEnTo examine factors useful in evaluation of suspect decentration after refractive surgery.nnnMETHODSnWe evaluated 148 cases (eyes) referred to us for recentering procedures by review of information obtainable by evaluation of pupil position, corneal topography, and corneal curvature gradient.nnnRESULTSnOnly a minority of eyes (n=5, 3.4%) were truly decentered; in the remaining majority a high dioptric gradient with consequent focal scarring was present (n=107, 72.3%). In 28 eyes (18.9%), a drifting of the eye during treatment was responsible, and in eight eyes (5.4%), a central island was observed.nnnCONCLUSIONSnProper corneal topographical diagnosis reduces the risk of improperly suspecting decentration, and for most cases, smoothing of the central cornea is a simple and efficacious solution. Recommendations for the prevention of decentration include proper patient positioning, special care in treating high myopes, preoperative check of pupil displacement nasally, evaluation of preoperative map with detection of high temporal curvature gradient, and use of the cross-cylinder technique in the treatment of astigmatism.