RECENT DEVELOPMENTS IN COMPUTERISED ANALYSIS OF THERMOLUMINESCENCE GLOW CURVES: SOFTWARE CODES, MECHANISMS AND DOSIMETRIC APPLICATIONS.

The computerised deconvolution of thermoluminescence glow curves into component glow peaks is discussed in detail with special emphasis on advances of the subject post 2013. A plethora of computer codes have been developed using models based on first-order kinetics, second-orders kinetics, interactive traps and continuous distributions of activation energies. The glow curves of several materials are displayed and discussed along with new and improved dosimetric applications:precision effects of heating rate, heavy charged particles, mixed field α/ϒ dosimetry, fading and dose-response linearity. Finally recommendations are made for future efforts.

[In vivo confocal microscopy evaluation of corneal changes induced after LASIK using the IntraLase femtosecond laser technique]. / Evaluation en microscopie confocale des modifications morphologiques cornéennes induites après LASIK et découpe du volet stromal par laser femtoseconde IntraLase.

PURPOSE: To assess stromal modifications occurring after IntraLase femtosecond laser for laser in situ keratomileusis (LASIK) using the Heidelberg retina tomograph II/Rostock cornea module. MATERIAL AND METHODS: Twelve eyes from six patients were examined using the Heidelberg retina tomograph II cornea module after IntraLase femtosecond laser: ten eyes were examined at 1 week and 2 months after laser surgery, including four eyes examined at day 1, and two eyes examined at day 2. Morphological modifications of the corneal stroma, flap interface, and flap margin were evaluated at these different times and compared with the mechanical microkeratome interfaces of five patients (ten eyes), using the same technique at the same periods after the surgical intervention. RESULTS: Evaluations at days 1 and 7 showed simultaneous depletion and activation of keratocytes on both sides of the interface. We also observed some brightly reflecting particles together with scattered, less bright dots, from day 7 and increasing after 2 months. Some clinically visible deposits at the level of the interface were observed at the periphery of the flap at day 1 and could represent cell-degradation products. With confocal microscopy, they appeared as homogeneous reflective deposits with a larger size than that of particles; they had decreased at month 2. The flap margin appeared microscopically as a very clear-cut edge, including epithelial cells, while those performed with a mechanical microkeratome appeared more like a poorly limited fibrotic scar. We also observed a secondary fibrotic reaction at month 2, adjacent to the still well-defined IntraLase flap edge. CONCLUSION: This study showed substantial morphological similarity between the interfaces obtained with femtosecond laser and mechanical microkeratome. The discovery of brightly reflecting particles in the IntraLase interface goes against the hypothesis of the metallic origin of these deposits. The flap margin microscopically looked extremely well delimited, but seemed to provoke an adjacent secondary fibrotic reaction, both microscopically and macroscopically, greater at 2 months than after a mechanical microkeratome cut.

[Corneal stromal changes after LASIK]. / Aspect en microscopie confocale des modifications morphologiques cornéennes induites par le LASIK.

PURPOSE: To assess stromal modifications after laser in situ keratomileusis (LASIK) for myopia using in vivo confocal microscopy. METHODS: Thirteen eyes from 10 patients were examined before surgery and at days 8 and 30 after surgery using an in vivo confocal microscope coupled with a Z-Scan system. Stromal morphological changes, keratocyte density, flap thickness, and subclinical haze were evaluated and compared at different time points. RESULTS: Microfolds at the Bowman's layer were found in 55%, eyes as well as variable reflectivity particles located at the interface level in all postoperative examined eyes. The mean flap and activated-cell area thicknesses were respectively, 101+/-28 micrometer and 50.5+/-14 micrometer with a significant negative correlation (r=-0.89, p=0.01). The intensity of the added peak (47.3+/-8.6% scattered light), corresponding to the subclinical haze, as measured by Z-Scan, was also negatively correlated with the flap thickness (r=-0.89, p=0.01). CONCLUSION: This study confirms the presence of microfolds and particles at the interface level as subclinical complications. Evaluating the keratocytic activation by confocal microscopy can lead to a better understanding of corneal wound healing after LASIK and can help to improve the techniques. The flap thickness seems to be involved in the cellular activation induced by LASIK.

Evaluation of corneal stromal changes in vivo after laser in situ keratomileusis with confocal microscopy.

PURPOSE: To assess by in vivo confocal microscopy the modifications of the corneal stroma after laser in situ keratomileusis (LASIK) for myopia. DESIGN: Nonrandomized comparative (self-controlled) trial. PARTICIPANTS: Sixteen eyes of 13 patients were examined before surgery and at days 8, 30, and 90, and 9 eyes were examined at 6 months postoperatively using an in vivo confocal microscope. TESTING/INTERVENTION: Stromal morphologic changes, keratocyte density, flap thickness, and subclinical haze were evaluated and compared at different time points. LASIK was performed with a Flapmaker microkeratome (Solan Ophthalmic products, Jacksonville, FL) and a Lasersight LSX excimer laser (LaserSight Technologies Inc., Winter Park, FL). MAIN OUTCOME MEASURE: Confocal microscopy results. RESULTS: Microfolds at the Bowman's layer were found in most eyes, as well as variable reflectivity particles (pa) located at the interface level in all eyes examined postoperatively. The density of these particles significantly decreased with time with, respectively, 504 +/- 101 pa/mm2 at day 8 and 380 +/- 111 pa/mm2 at day 30 (P = 0.003), 332 +/- 100 pa/mm2 at month 3 and 312 +/- 40 pa/mm2 at month 6. The mean flap and the activated-cells area thicknesses were, respectively, 102 +/- 26 microm and 61 +/- 19 microm and showed significant negative correlation (P < 0.0001). The intensity of the added peak (47.3 microm 8.6%), corresponding to the subclinical haze, realized by Z-scan measure, was also negatively correlated with flap thickness (P = 0.01). Keratocyte (k) density quantified in the posterior stroma significantly increased from day 0 (480 +/- 67 k/mm2) to day 8 (701 +/- 41 k/mm2, P < 0.0001 compared with day 0) and day 30 (917 +/- 143 k/mm2, P = 0.0006, compared with day 0) but significantly decreased at 3 months postoperatively (597 +/- 56 k/mm2, P < 0.0001 compared with day 30) to reach the initial level at month 6 (502 +/- 41 k/mm2, nonsignificant compared with day 0). There was no correlation between preoperative or postoperative spherical equivalent and the density of particles, keratocytes, and the haze intensity. CONCLUSIONS: This study confirms the presence of microfolds and particles at the interface level, as well as subclinical impairment. Evaluation of keratocyte density constitutes a major contribution of confocal microscopy toward an understanding of the keratocyte response to corneal wound healing after corneal refractive surgery. Moreover, flap thickness seems to be involved in the postoperative cellular activation with a higher response when thin.

[Clinical outcome after in situ laser keratomileusis (LASIK) for myopia: a series of 390 eyes]. / Résultats cliniques du laser in situ keratomileusis (LASIK) chez le myope: étude sur 390 yeux.

PURPOSE: We report our personal experience with LASIK for myopia to study its efficacy, safety, predictability and stability for low, moderate and high myopia. PATIENTS AND METHODS: Between January 1996 and December 1997, 390 eyes were treated. Follow-up was 6 months for 254 and one year for 136. Initial myopia ranged from -1.5 to -16 diopters with a spherical equivalent of -8.49D. The surgical procedure with topical anesthesia used the Chiron ALK-E automated corneal shaper for the initial flap of 160 microns thick, and the Chiron Excimer Laser Keracor 117 Technolas with an active eye tracking system for the stromal photoablation. Preoperative refraction, uncorrected (UVA) and best corrected visual acuity (BCVA) were compared to postoperative results. RESULTS: They are reported overall and for sub-groups of myopia. (A<=-5 D, -5 D=20/40 at 6 months. Average UVA was 0.65 D at one year and was as better as preoperative myopia was lower (group A 0.65D, group B0.5 at 6 months). Mean spherical equivalent was +0.08 D at J1 and -1.02 D at one year (group A -0.8 D, group B -0.67 D, and group C -3.92 D). Safety was correct and only a few per and postoperative complications were observed with only two patients losing more than two lines of BCVA. Mean BCVA was 0.72 at one year. Predictability demonstrated that 90% of group A eyes were at +/-1 D from emmetropia and 74% in group B at 6 months. More than 95% of eyes were stable at 6 months and 90% at one year. CONCLUSION: LASIK is a safe and efficient surgical treatment for low, moderate and high myopia, and should be improved with new software and new corneal shapers.

Angle-fixated anterior chamber phakic intraocular lens for myopia of -7 to -19 diopters.

PURPOSE: To assess the safety and efficacy of a second generation, anterior chamber phakic intraocular lens (Baikoff Model ZB5M) in patients with high myopia. METHODS: One hundred and twenty-one patients (134 eyes) with myopia of -7.00 to -18.80 D were implanted with the ZB5M lens and followed for 18 to 52 months; the number of eyes evaluated was: 6 months (104 eyes), 1 year (91 eyes), 18 months (78 eyes), 2 years (68 eyes), and 3 years (35 eyes). RESULTS: Postoperative spherical equivalent refraction averaged -1.00 D and the error in refractive correction (achieved minus intended) averaged -0.40 D during the first 2 years, increasing -to -1.30 D refraction and -0.60 D error in refractive correction at 3 years. At 2 years, approximately 40% of eyes had a spherical equivalent refraction within +/-0.50 D, and 65% within +/-1.00 D. The uncorrected distance visual acuity was 0.048 at baseline and 0.5 at 3 years; near visual acuity was 0.21 at baseline and approximately 0.7 over the 3 years of follow-up. Spectacle-corrected distance visual acuity at baseline was 0.54; it improved to 0.7. Near visual acuity was 0.65 at baseline and it improved to approximately 0.75. Endothelial cell counts in the central and peripheral cornea were reduced by an average 3.3% at 6 months, declining an additional 1% to 2% over the remaining follow-up period. Regression analyses indicated that most of the endothelial cell loss was due to surgery. Additional complications included halos/glare in 37 of 133 eyes (27.8%) and iris retraction with pupillary ovalization in 30 of 133 eyes (22.6%). The intraocular lens was exchanged in four of 133 eyes (3.0%) and removed in three of 133 eyes (2.3%), the latter because of halos (one eye) and a flat anterior chamber with severe inflammation (two eyes). CONCLUSIONS: Implantation of the Baikoff ZB5M lens in the anterior chamber of phakic eyes significantly reduced high myopia and produced a stable refractive outcome over the 3 years, accompanied by marked improvement in uncorrected distance visual acuity and minimal, non-progressive damage to the corneal endothelium. Frequent complications included pupillary ovalization and halos/glare. Improvements in accuracy of IOL power calculations are needed.

[Results of treatment of undercorrections of radial keratotomy by Excimer laser]. / Résultats du traitement des sous-corrections de kératotomie radiaire au laser Excimer.

Photorefractive keratectomy (PRK) was performed with Excimer Laser after undercorrected radial keratectomy in 21 eyes of 15 patients (maximum 8 incisions, 3 mm optical zone). There was at least a 6-month interval between the two procedures. At the time of PRK, the mean age of the patients was 31 years and the mean spherical equivalent -2.3 D. Mean follow-up after PRK was 7.5 months; 10 eyes were followed for more than one year. Quite satisfactory results were obtained since PRK was effective in 88% (eyes with uncorrected visual acuity of 20/40 or better); predictability at +/- 1 D was 89%. Stable refractiveness was achieved at 3 months. The procedure is safe: there was no loss of best corrected visual acuity nor haze at one year. Other means of treating for undercorrection after refractive keratectomy were discussed in comparison with this technique.

[Clinical results of photo-refractive keratectomy. Preliminary study with 57 eyes]. / Résultats cliniques de la photo-kératectomie réfractive. Etude préliminaire sur 57 yeux.

The authors report their personal experience of Photo-Refractive Keratectomy (PRK) with an Excimer Laser based on the study of 57 sighted eyes, 24 with more than six months and 11 with more than one year of follow-up. The initial myopia ranged from -1 to -13 D with a spherical average equivalent of -6.36 D. The photo-ablations, performed with the Excimer of the Summit Company, ranged from 3.7 to 5 mm of diameter and 16 to 76 mu in depth. Results are reported overall and for sub-groups of myopia (A < or = -3 D, -3 D < B < or = -7 D, -7 D, < C). They were satisfactory since at one year 45% of eyes obtained a visual acuity without correction > or = 5/10 and 64% of eyes were within one dioptre of emmetropia; stability of refraction from six months to one year is close to 80%; safety was good since no patient has lost a line of best spectacle corrected visual acuity at one year and we only found one case of haze at 1+ without visual loss. These encouraging results lead the authors to pursue their study and to include new patients to obtain larger groups in order to establish statistically significant differences for parameters such as age, sex, myopia, keratometry, depth and optical zone of photo-ablation.