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Ocular rigidity in living human eyes.

Ξενόγλωσσα συγγράμματαΣε περιοδικά του SCI
1. Pallikaris Ι, Kymionis GD, Ginis H, Kounis G, Tsilimbaris M.
Invest Ophthalmol Vis Sci. 2005; 46(2):409-14.

PURPOSE: To measure the rigidity coefficient of a large number of subjects at clinically encountered intraocular pressures (IOPs) and to examine the possible correlation of ocular rigidity with other factors, such as the age of the patients, ocular parameters (axial length and corneal thickness), and pathologic conditions affecting the eye.

METHODS: The pressure-volume relationship and the ocular rigidity coefficient (K) were determined in 79 eyes undergoing cataract surgery, by injecting 200 microL of saline solution (in steps of 4.5 microL) through the limbus into the anterior chamber, while continually monitoring the IOP with a transducer, up to the limit of 60 mm Hg. Data within an IOP range of 10 to 35 mm Hg were used to calculate the scleral rigidity coefficient. All measurements were taken at the same time of day, to eliminate any possible diurnal variation.

RESULTS: The mean ocular rigidity coefficient was 0.0126 mm Hg/microL (95% confidence interval [CI], 0.0112-0.0149). A statistically significant positive correlation between the rigidity coefficient and age of the patient was found (P = 0.02), whereas similar findings were not observed for the examined ocular parameters (axial length, P = 0.09; and corneal thickness, P = 0.12). No correlation was found for patients with diabetes mellitus (P = 0.39), age-related macular degeneration (P = 0.55), and hypertension (P = 0.45).

CONCLUSIONS: The present study provides quantitative data on the ocular rigidity coefficient based on measurements in a large series of living human eyes. A positive correlation between the ocular rigidity coefficient and the patient’s age was documented.

Femtosecond assisted sutureless Anterior Lamellar keratoplasty.

Ξενόγλωσσα συγγράμματαΣε περιοδικά του SCI
1. Yoo S, Kymionis GD, Koreishi A, Ide T, Goldman D , Karp C , O’Brien T. , Cubertson W ,Alfonso E.
Ophthalmology. 2008; 115(8):1303-7
PURPOSE: To report the technique and small case series results of femtosecond laser-assisted sutureless anterior lamellar keratoplasty (FALK) for anterior corneal pathology.
DESIGN: Retrospective, noncomparative, interventional case series.
PARTICIPANTS: Twelve consecutive eyes from 12 patients with anterior corneal scarring.
INTERVENTION: Femtosecond laser-assisted sutureless anterior lamellar keratoplasty.
MAIN OUTCOME MEASURES: Measured parameters included femtosecond laser settings, technique, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and complications.
RESULTS: Mean follow-up was 12.7 months (range, 6-24). No intraoperative complications were found. Uncorrected visual acuity (VA) improved in 7 eyes (58.3%) compared with preoperative VA. The mean difference between preoperative and postoperative UCVAs was a gain of 2.5 lines (range, unchanged-7 lines). Best-corrected VA was unchanged or improved in all eyes compared with preoperative levels. The mean difference between preoperative and postoperative BCVAs was a gain of 3.8 lines (range, unchanged-8 lines). In 2 eyes, adjuvant surgical procedures were performed (one treated with phototherapeutic keratectomy and the other with photorefractive keratectomy). Six patients (50%) developed dry eye after FALK, which improved during the follow-up period. No graft rejection, infection, or epithelial ingrowth was found in this series of patients.
CONCLUSIONS: Femtosecond laser-assisted sutureless anterior lamellar keratoplasty could improve UCVA and BCVA in patients with anterior corneal pathology.

Intraoperative pachymetric measurements during corneal collagen cross-linking with riboflavin and ultraviolet A irradiation.

Ξενόγλωσσα συγγράμματαΠεριοδικά εκτός SCI
Kymionis GD, Kounis GA, Portaliou DM, Grentzelos MA , Karavitaki AE, Coskunseven E, Jankov MR , Pallikaris IG.
Ophthalmology. 2009; 116(12):2336-9.

OBJECTIVE: To study central corneal pachymetric variations during corneal collagen cross-linking (CXL) treatment with the use of riboflavin and ultraviolet A irradiation (UVA).

DESIGN: Prospective, noncomparative, interventional clinical study.

PARTICIPANTS: Fifteen keratoconic patients (19 eyes) were enrolled.

METHODS: All patients underwent riboflavin-UVA-induced corneal CXL. Intraoperative central corneal thickness (CCT) measurements using ultrasound pachymetry were performed during the procedure. Measurements were obtained after epithelial removal, after riboflavin drop instillation, and every 5 minutes (6 interval times) during UVA irradiation (30 minutes).

MAIN OUTCOME MEASURES: Central corneal thickness measurements.

RESULTS: Mean patient age was 26.9+/-6.5 years (range, 17-40 years). Ten were male and 5 were female. Mean preoperative CCT was 458.5+/-21.5 microm (range, 427-494 microm; 95% confidence interval [CI], 448-467 microm) and 415.7+/-20.6 microm (range, 400-468 microm; 95% CI, 406-426 microm) before and after epithelial removal, respectively. There was a statistically significant decrease (mean, 75 microm) of CCT between the epithelial removal interval (415.7+/-20.6 microm; range, 400-468 microm) and at the end of riboflavin solution instillation (340.7+/-22.9 microm; range, 292-386 microm; P<0.001). There was no statistically significant change in CCT during irradiation (P>0.05). There was no statistically significant difference between preoperative and 1-month postoperative endothelial cell count (preoperative, 2780+/-197 to 1-month postoperative, 2713+/-116; P = 0.14). No intraoperative, early postoperative, or late postoperative complications were observed in this patient series.

CONCLUSIONS: During corneal CXL with the use of riboflavin and UVA irradiation, a statistically significant decrease of CCT was demonstrated.

Corneal Collagen Cross-linking With Riboflavin and Ultraviolet-A Irradiation in Patients With Thin Corneas.

Ξενόγλωσσα συγγράμματαΠεριοδικά εκτός SCI
1. Kymionis GD, Portaliou D, Diakonis V, Kounis G, Panagopoulou S, Grentzelos M.
Am J Ophthalmol 2012; 153(1):24-8.

PURPOSE: To report the outcomes after corneal collagen cross-linking (CXL) treatment with riboflavin and ultraviolet-A (UVA) irradiation in patients with thin corneas (minimum corneal thickness less than 400 μm after epithelial removal and before riboflavin instillation).

DESIGN: Prospective case series.

METHODS: Twelve patients (14 eyes, with minimum corneal thickness less than 400 μm after epithelial removal) were included in the study. All patients underwent riboflavin-UVA-induced CXL using the standard CXL (Dresden) protocol. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) (decimal scale), manifest refraction (diopters, D), and topography were evaluated at baseline and at 1, 3, 6, and 12 months follow-up. Images of the endothelium were acquired with a modified confocal scanning laser ophthalmoscope.

RESULTS: No intraoperative or postoperative complications were observed in this patient series. Mean minimum preoperative corneal thickness at the apex of the cone after epithelial removal and before riboflavin instillation was 373.92 ± 22.92 μm (range 340-399 μm). UDVA and CDVA improved from 0.25 ± 0.15 and 0.40 ± 0.20 to 0.27 ± 0.17 and 0.49 ± 0.20 respectively at the last follow-up examination. There was a reduction of the mean keratometry readings from 51.99 ± 5.57 D to 49.33 ± 4.82 D at the last follow-up. A significant decrease of endothelial cell density was observed (preoperative: 2733 ± 180 cells/mm(2) [range 2467-3016], last follow-up visit: 2441 ± 400 cells/mm(2) [range 1448-2920], P < .01).

CONCLUSIONS: CXL in thin corneas with minimum corneal thickness less than 400 μm after epithelial removal seems to result in a significant endothelial cell density decrease postoperatively. This finding was not related to other intraoperative or postoperative complications.

Topical application of autologous adipose-derived mesenchymal stem cells (MSCs) for persistent sterile corneal epithelial defect.

Ξενόγλωσσα συγγράμματα
Agorogiannis G, Alexaki V, Castana O, Kymionis GD.
Graefes Arch Clin Exp Ophthalmol. 2012; 250(3):455-7.

Topical application of autologous adipose-derived mesenchymal stem cells (MSCs) in a patient with post-traumatic persistent sterile corneal epithelial defect.

Combined Transepithelial Phototherapeutic Keratectomy and Corneal Collagen Cross-Linking for Progressive Keratoconus.

Ξενόγλωσσα συγγράμματα
Kymionis GD, Grentzelos M, Kounis G, Diakonis V, Limnopoulou A, Panagopoulou S.
Ophthalmology. 2012; 119(9):1777-84.

PURPOSE: To compare the outcomes of corneal collagen cross-linking (CXL) for the treatment of progressive keratoconus using 2 different techniques for epithelial removal: transepithelial phototherapeutic keratectomy (t-PTK) versus mechanical epithelial debridement.

DESIGN: Prospective, comparative, interventional case series.

PARTICIPANTS: Thirty-four patients (38 eyes) with progressive keratoconus were enrolled.

METHODS: All patients underwent uneventful CXL treatment. Sixteen patients (19 eyes) underwent epithelial removal using t-PTK (group 1) and 18 patients (19 eyes) underwent mechanical epithelial debridement using a rotating brush (group 2) during CXL treatment. Visual and refractive outcomes were evaluated along with corneal confocal microscopy findings preoperatively and at 1, 3, 6, and 12 months postoperatively.

MAIN OUTCOME MEASURES: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and keratometry readings.

RESULTS: No intraoperative or postoperative complications were observed in any of the patients. In group 1, logarithm of the minimum angle of resolution mean UDVA and mean CDVA improved from 0.99 ± 0.71 and 0.30 ± 0.26 preoperatively to 0.63 ± 0.42 (P = 0.02) and 0.19 ± 0.18 (P = 0.008) at 12 months postoperatively, respectively. In group 2, neither mean UDVA nor mean CDVA demonstrated a significant improvement at 12 months postoperatively (P>0.05). In group 1, mean corneal astigmatism improved from -5.84 ± 3.80 diopters (D) preoperatively to -4.31 ± 2.90 D (P = 0.015) at the last follow-up, whereas in group 2 there was no significant difference at the same postoperative interval (P>0.05). No endothelial cell density alterations were observed throughout the follow-up period for both groups (P>0.05).

CONCLUSIONS: Epithelial removal using t-PTK during CXL results in better visual and refractive outcomes in comparison with mechanical epithelial debridement.

Correlation of the Corneal Collagen Cross-Linking Demarcation Line Using Confocal Microscopy and Anterior Segment Optical Coherence Tomography in Keratoconic Patients.

Ξενόγλωσσα συγγράμματα
Kymionis GD, Grentzelos M, Plaka A, Tsoulnaras K, Diakonis V, Liakopoulos D, Kankariya V, Pallikaris A.
Am J Ophthalmol. 2014 Jan;157(1):110-115.e1.

PURPOSE: To evaluate and compare the depth of the corneal stromal demarcation line after corneal collagen cross-linking (CXL) using 2 different methods: confocal microscopy and anterior segment optical coherence tomography (AS OCT).

DESIGN: Prospective, comparative, interventional case series.

METHODS: Seventeen patients (18 eyes) with progressive keratoconus were enrolled. All patients underwent uneventful CXL treatment according to the Dresden protocol. One month after surgery, corneal stromal demarcation line depth was measured in all patients by 2 independent observers using confocal microscopy and AS OCT.

RESULTS: Mean corneal stromal demarcation line depth measured using confocal microscopy by the first observer was 306.22 ± 51.54 μm (range, 245 to 417 μm) and that measured by the second observer was 303.5 ± 46.98 μm (range, 240 to 390 μm). The same measurements using AS OCT were 300.67 ± 41.56 μm (range, 240 to 385 μm) and 295.72 ± 41.01 μm (range, 228 to 380 μm) for the first and second observer, respectively. Pairwise comparisons did not reveal any statistically significant difference between confocal microscopy and AS OCT measurements for both observers (P = .3219 for the first observer and P = .1731 for the second observer).

CONCLUSIONS: Both confocal microscopy and AS OCT have similar results in evaluating the depth of the corneal stromal demarcation line after CXL.

High-Resolution Optical Coherence Tomography-Guided Donor Tissue Preparation for Descemet Membrane Endothelial Keratoplasty Using the Reverse Big Bubble Technique.

Ξενόγλωσσα συγγράμματα
Cabot F, Kankariya VP, Ruggeri M, Yoo SH, Vaddavalli PK, Parel JM, Kymionis GD
Cornea. 2014 Apr;33(4):428-31.

PURPOSE: The aim of this study was to assess the feasibility of high-resolution spectral domain optical coherence tomography (HR-SDOCT) to guide donor tissue preparation in Descemet membrane endothelial keratoplasty using the reverse big bubble technique.

METHODS: Three corneoscleral discs were included in this ex vivo experimental study. A 27-G cannula was introduced into each cornea at the periphery by 3 different surgeons. Each surgeon attempted to achieve the ideal depth (pre-Descemetic plane) of the tip of the cannula for air injection to produce the reverse big bubble to separate the Descemet membrane (DM) from the posterior stroma. A supine optical coherence tomography system built at the Ophthalmic Biophysics Center of the Bascom Palmer Eye Institute was used to estimate in real-time the depth reached by the tip of the cannula in the posterior stroma during tissue preparation.

RESULTS: After air injection, 1 successful big bubble was obtained, while each of the other corneoscleral discs had intrastromal emphysema and DM perforation. On HR-SDOCT evaluations, artifacts were noticed at the tip of the cannula. The successful big bubble demonstrated the separation of the DM and the stroma without intrastromal hyperreflectivity. Emphysema was visualized on the HR-SDOCT as a hyperdense intrastromal area shadowing the posterior structures of the anterior chamber.

CONCLUSIONS: The HR-SDOCT-guided reverse big bubble technique may be a useful method to prepare donor tissue in Descemet membrane endothelial keratoplasty. Further improvements in high-resolution optical coherence tomography technology are needed this promising technique.

Femtosecond Laser-Assisted Intracorneal Biopolymer Insertion for the Symptomatic Treatment of BullousKeratopathy.

Ξενόγλωσσα συγγράμματα
Kymionis GD, Diakonis VF, Kankariya VP, Plaka AD, Panagopoulou SI, Kontadakis GA, Grentzelos MA, Tsilimbaris MK, Pallikaris IG.
Cornea. 2014 May;33(5):540-3.

PURPOSE: To describe a new minimally invasive surgical technique for the symptomatic management of bullous keratopathy in blind eyes.

METHODS: Four patients with severe corneal edema due to endothelial decompensation and no visual function in the affected eye presented for the relief of their ocular symptoms (pain and tearing). Femtosecond laser technology was used to create a deep corneal pocket into which silicone oil was inserted.

RESULTS: After the procedure, all patients demonstrated immediate relief of their symptoms, along with restoration of a normal corneal surface 7 days after the procedure (no bullae and no epithelial defects). All patients remained free of symptoms during the entire follow-up period (from 24 to 31 months). Anterior to the inserted implant, the corneal lamellae remained compact, transparent, and without bullae; whereas the posterior corneal stroma under the implant was edematous. No intraoperative or postoperative complications were noted.

CONCLUSIONS: Intracorneal insertion of silicone oil is a feasible new technique for the symptomatic treatment of bullous keratopathy in blind eyes.

Factors Affecting DSAEK Graft Lenticle Adhesion: An In Vitro Experimental Study.

Ξενόγλωσσα συγγράμματα
Vaddavalli PK, Diakonis VF, Canto AP, Kankariya VP, Pappuru RR, Ruggeri M, Banitt MR, Kymionis GD, Yoo SH.
Cornea. 2014 Jun; 33(6):551-4

PURPOSE: The aim of this study was to evaluate different factors that affect Descemet stripping automated endothelial keratoplasty (DSAEK) donor graft lenticle adhesion to the recipient cornea.

METHODS: This experimental study included 10 eye bank recipient corneas and 10 donor DSAEK lenticles. Recipient corneas were mounted on an artificial anterior chamber (AC), whereas donor lenticles were placed beneath the host cornea. Using optical coherence tomography and imaging software, the interface gap (IG) between the donor and recipient cornea was quantified to evaluate the effect of variations in AC air fill pressure, AC air fill duration, corneal massage, and corneal venting incisions on DSAEK donor graft lenticle adhesion.

RESULTS: Different intraocular pressures (IOP) under air for the same time intervals, do not significantly correlate with the IG; nevertheless, it was noticed that the IG decreases as the IOP increases. With respect to the magnitude of AC IOP, there was no statistically significant difference when comparing 10 mm Hg with 30 mm Hg and assessing IG (P = 0.4). Complete air-fluid exchange resulted in significantly higher IG when compared with AC air bubble of 10 and 30 mm Hg that was sustained for 1 hour (P < 0.05). Furthermore, corneal surface massage did not facilitate DSAEK graft adhesion (P = 0.59). Finally, paracentral venting incisions followed by interface fluid aspiration seemed to significantly decrease the IG (P = 0.014).

CONCLUSIONS: Corneal venting incisions and higher AC IOP values seem to facilitate DSAEK donor graft lenticle adhesion to the recipient cornea.

Long-term results of combined transepithelial phototherapeutic keratectomy and corneal collagen cross-linking for keratoconus - the Cretan protocol.

Ξενόγλωσσα συγγράμματα
Kymionis GD, Grentzelos MA, Kankariya VP, Liakopoulos DA, Karavitaki AE, Portaliou DM, Tsoulnaras KI, Pallikaris IG
J Cataract Refract Surg. 2014 Sep; 40(9):1439-45

PURPOSE: To present the long-term results of combined transepithelial phototherapeutic keratectomy (PTK) and corneal collagen crosslinking (CXL) for keratoconus.

SETTING: Vardinoyiannion Eye Institute of Crete, University of Crete, Heraklion, Crete, Greece.

DESIGN: Prospective case series.

METHODS: Patients with progressive keratoconus had combined transepithelial PTK and CXL (Cretan protocol). Visual and refractive outcomes and the endothelial cell density (ECD) were evaluated preoperatively and postoperatively.

RESULTS: Twenty patients (23 eyes) were enrolled; postoperatively 23 eyes were evaluated at 1 and 2 years, 11 at 3 years, and 7 at 4 years. The mean follow-up was 33.83 months±10.82 (SD) (range 24 to 56 months). No intraoperative or postoperative complications occurred. The mean uncorrected distance visual acuity improved significantly from 0.99±0.57 logMAR preoperatively to 0.61±0.36 logMAR at the last follow-up (P<.001) and the mean corrected distance visual acuity, from 0.27±0.24 logMAR to 0.17±0.14 logMAR (P=.018), respectively. The mean steep and mean flat keratometry readings decreased significantly from 53.39±7.14 diopters (D) and 47.17±4.87 D, respectively, preoperatively to 49.99±4.36 D (P<.001) and 45.47±2.95 D (P=.002), respectively, at the last follow-up. The mean corneal astigmatism improved significantly from -6.27±4.19 D preoperatively to -4.52±2.80 D (P<.001) at the last follow-up. No significant ECD alterations occurred (P>.05).

CONCLUSION: Combined transepithelial PTK and CXL was effective and safe in keratoconic patients over a long-term follow-up.

Long-term follow up of corneal collagen cross linking for keratoconus-the Cretan study

Σε περιοδικά του SCI
Kymionis GD, Grentzelos MA, Liakopoulos DA, Paraskevopoulos TA, Klados N, Tsoulnaras KI, V Kankaryia, I Pallikaris
Cornea 2014;33(10):1071-9

PURPOSE: The aim of this study was to present the long-term results of corneal collagen cross-linking (CXL) in patients with keratoconus.

METHODS: In this prospective, interventional case series, patients with progressive keratoconus underwent CXL treatment according to the Dresden protocol. Visual, refractive, and topographic outcomes along with endothelial cell density were evaluated preoperatively and at 1, 2, 3, 4, and 5 years postoperatively.

RESULTS: Twenty-one patients (25 eyes) were enrolled. The mean follow-up was 43.7 ± 12.2 (range, 24-60) months. Logarithm of the minimum angle of resolution (logMAR) mean uncorrected visual acuity and the mean best spectacle-corrected visual acuity improved significantly from 0.92 ± 0.54 and 0.29 ± 0.21 preoperatively to 0.63 ± 0.41 (P = 0.010) and 0.18 ± 0.18 (P = 0.011), respectively, at the last follow-up. Mean steep and mean flat keratometry readings reduced significantly from 52.53 ± 6.95 diopters (D) and 48.11 ± 5.98 D preoperatively to 49.10 ± 4.50 D (P < 0.001) and 45.58 ± 3.81 D (P = 0.001), respectively, at the last follow-up. The mean endothelial cell density was 2708 ± 302 cells per square millimeter preoperatively and did not change significantly (P > 0.05) at any postoperative interval (2593 ± 258 cells/mm at the last follow-up; P = 0.149).

CONCLUSIONS: CXL seems to be effective and safe in halting progression of keratoconus over a long-term follow-up period up to 5 years postoperatively.

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