Faculty Bibliography

Purpose : The small-incision lenticule extraction (SMILE) procedure and laser in situ keratomileusis (LASIK) are both safe, effective, and predictable surgical techniques for the correction of myopia. SMILE presents an alternative to LASIK, which currently may be considered the most established form of laser vision correction. The purpose of this study is to evaluate corneal biomechanical changes associated with low and high myopic correction performed with small incision lenticule extraction (SMILE, employing the Visumax laser, Carl Zeiss Meditec, Jena Germany) compared to Femtosecond-laser assisted LASIK (FS200 & EX500 lasers, Alcon Surgical, Ft. Worth, TX) Methods : Thirty human donor corneas were subjected to myopic SMILE or LASIK. These corneas were randomly allocated to one of four investigative groups (n=5 each), subjected to the following treatments: group-A -3.00 diopters (D) SMILE; group-B -8.00D SMILE; group-C -3.00D LASIK; group-D -8.00D LASIK. Additionally, two control groups (n=5 each) were formed, one for each procedure: group-E SMILE and group-F LASIK. The corneas in these control groups were subjected to the corresponding femtosecond-laser lamellar cuts but not to tissue removal. Biomechanical evaluation of tensile strength was conducted by biaxial force application. Primary outcome measures were stress at 10% and 15% strain, and Young's modulus at 10% and 15% strain. Results : In SMILE, the average relative difference (DELTA) of the four metrics evaluated was -35.6% between the -3.00D correction and control and -50.2% between the -8.00D correction and control. In LASIK, average DELTA was -21.2% between the -3.00D correction and control, and -50.4% between the -8.00D correction and control. When evaluating the same degree of myopic correction, SMILE, compared to LASIK, appears to result in greater biomechanical reduction for the -3.00D correction (-25.9%) while the difference at -8.00D correction is not statistically significant. Conclusions : Biomechanical tensile strength is reduced with increasing amounts of myopia corrected in both procedures. LASIK results in less strength reduction in smaller myopes while, in higher myopes, SMILE and LASIK appear to result in similar corneal tensile strength reduction

Purpose: The purpose of this study was to comparative investigate two myopic correction femtosecond laser techniques: femtosecond-assisted LASIK was compared to an all femto-second laser Small Incision refractive Lenticule Extraction (SMILE). Six-month refractive outcomes were comparatively evaluated. Methods: This is a single-center, retrospective analysis of 100 consecutive myopic patients. Group-A was treated with the SMILE (n=48 eyes), while the other eye (group-B) with LASIK (n=52 eyes). The LASIK procedure employed the Alcon Refractive surgery platform (Alcon Surgical, Ft. Worth, TX) comprised of the FS200 femtosecond and the EX500 excimer laser. The SMILE procedure employed the 500 kHz VisuMax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany). All operations were performed by the same surgeon (AJK). Results: LASIK SEQ corrected: -5.12+/-2.74 D(range -1.50 to -12.00). 6-month results: 82% within +/- 0.25D, 87% within +/- 0.50D; 91 % had 20/20 UDVA or better; 54% no change in Snellen lines, 46% gained 1 or more; predictability r^2 = 0.999. SMILE SEQ corrected: -4.63+/-1.90 D (range -2.50 to -9.50). 6-month results: 84 % within +/- 0.25D, 95% within +/- 0.50D; 88% had 20/20 UDVA or better; 45% no change in Snellen lines, 55% gained 1 or more; predictability r^2 = 0.972. Conclusions: FS-assisted LASIK and SMILE appear to have similar refractive results up to 6 months

Purpose: The purpose of this study was to comparative investigate potential impact of inflammation following myopic correction. The established current gold standard of femtosecond-assisted LASIK was compared to an all femto-second laser Small Incision refractive Lenticule Extraction (SMILE). No study has investigated the potential differences between SMILE and LASIK from the stand-point of postoperative inflammation. Methods: This is a contralateral, perspective stud employing 10 consecutive myopic patients, in which one eye (group-A) was treated with the SMILE, while the other eye (group-B) with LASIK. The LASIK procedure employed the Alcon Refractive surgery platform (Alcon Surgical, Ft. Worth, TX) comprised of the FS200 femtosecond and the EX500 excimer laser. The SMILE procedure employed the 500 kHz VisuMax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany). InflammaDry (Rapid Pathogen Screening, Inc., Sarasota, FL) is an in-office test that detects matrix metalloproteinase MMP-9, an inflammatory marker that is consistently elevated in the tears of patients with dry eye disease. Using direct sampling microfiltration technology, InflammaDry identifies elevated levels of MMP-9 protein in tear fluid samples taken from the palpebral conjunctiva. Levels of MMP-9 were tested 1-month, 3-months and 6-months postoperatively, facilitated with the use of InflammaDry solution. Inclusion criteria: 18 years of age or older. Exclusion Criteria: Allergy to cornstarch or Darcon, Allergy to topical anesthetic or fluorescein dye. Results: MMP-9 levels in group-A (LASIK) were 65+/-15 ng/ml, 55+/-12 ng/ml, 45+/-9 ng/ml at 1-, 3-, and 6-months, respectively. MMP-9 levels in group-B (SMILE) were 45+/-13 ng/ml, 42+/-12 ng/ml, 37+/-8 ng/ml at 1-, 3-, and 6-months, respectively. All groups displayed statistically significant differences at the perspective follow-up periods examined. Conclusions: Potential differences between LASIK and SMILE include increased inflammation levels postoperatively up to 6 months

PURPOSE: To evaluate corneal endothelial cell density (ECD) and morphology after cataract surgery using coaxial ultrasound (US) phacoemulsification or a recently introduced coaxial nanosecond laser technique. SETTING: Department of Ophthalmology, Medical University of Sofia, Sofia, Bulgaria. DESIGN: Prospective cohort study. METHODS: Coaxial US phacoemulsification was performed in 1 eye (US group) and coaxial nanosecond laser-assisted cataract surgery in the contralateral eye (laser group) of the same patient. Nuclear sclerosis was graded from nuclear opalescence (NO) 3, nuclear color (NC) 3 to NO4, NC4 using the Lens Opacities Classification System III. The central ECD, coefficient of variation (CoV) in cell size (objective measure of polymegethism), and percentage of hexagonal cells (an index of pleomorphism) were evaluated. RESULTS: Eighty-two eyes (41 patients) had uneventful surgery. The mean ECD was 2517 cells/mm(2) +/- 137 (SD) preoperatively and 2287 +/- 155 cells/mm(2) at 2 years in the US group and 2521 +/- 233 cells/mm(2) and 2420 +/- 292 cells/mm(2), respectively, in the laser group (both P < .001). The mean CoV was 0.27 +/- 2.4 preoperatively and 0.30 +/- 2.4 at 2 years in the US group and 0.27 +/- 2.8 and 0.27 +/- 2.0, respectively, in the laser group (both P < .001). The mean percentage of hexagonal cells was 42.3% +/- 3.6% preoperatively and 37.74% +/- 3.54% at 2 years in the US group and 42.8% +/- 3.2% and 43.00% +/- 2.68%, respectively, in the laser group (both P < .001). CONCLUSION: Nanosecond laser phacoemulsification had advantages over US phacoemulsification in terms of endothelial cell structure preservation. FINANCIAL DISCLOSURES: Dr. Kanellopoulos is consultant to Alcon Surgical, Inc., Allergan, Inc., Avedro, Inc., Keramed, Inc., Optovue, Inc., i-Optics Corp., and Carl Zeiss Meditec AG. Neither of the other authors has a financial or proprietary interest in any material or method mentioned.

PURPOSE: To evaluate ex vivo the possible difference in corneal cross-linking (CXL) biomechanical effect of different ultraviolet-A (UV-A) irradiances. METHODS: The study involved 25 human donor corneas, randomly allocated to 5 groups (n = 5 each). CXL was applied with UV-A irradiances of 3, 9, 18, 30, and 45 mW/cm, maintaining equal cumulative energy dose of 5.4 J/cm. UV-A was delivered on half of the cornea. The nonirradiated halves served as controls. Specimens were subjected to collagenase-A enzymatic digestion. The time to complete dissolution in each specimen was recorded. RESULTS: Time to dissolution in group-A (3 mW/cm for 30 minutes) was 321 +/- 13.4 minutes (range: 300-330) compared with 171 +/- 8.2 (range: 165-180) for their control. In group-B (9 mW/cm for 10 minutes), it was 282 +/- 19.6 minutes (range: 270-315) compared with 177 +/- 6.7 (165-180) for their control. In group-C (18 mW/cm for 5 minutes), it was 267 +/- 19.6 minutes (range: 240-285) compared with 177 +/- 7.7 (range: 165-180) for their control. In group-D (30 mW/cm for 3 minutes), it was 252 +/- 12.5 minutes (range: 240-270) compared with 180 +/- 10.6 minutes (range: 165-195) for their control. In group-E (45 mW/cm for 2 minutes), it was 204 +/- 17.1 minutes (range: 180-225) compared with 186 +/- 8.2 minutes (range: 180-195) for their control. CONCLUSIONS: The data in this ex vivo human corneal study indicate that the biomechanical effect of CXL studied by resistance to enzymatic digestion in human corneas is comparable between irradiances of 9, 18 and 30 mW/cm and seems to be reduced at a fluence of 45 mW/cm.

PURPOSE: To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. SETTING: Private clinical ophthalmology practice. PATIENTS AND METHODS: A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. RESULTS: Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B (P<0.01). The residual percentages in both groups were measured with refractive astigmatism of more than -0.5 diopters. CONCLUSION: Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

BACKGROUND: Femtosecond-laser assisted clear cornea cataract surgery may hold promise in safer and more effective procedures. We decided to perform a comparative study to standard manual incision phacoemulsification surgery. METHODS: This is a single-center, single-intervention, and prospective comparative data evaluation of 133 consecutive cases subjected to cataract surgery. Group-A (Phaco), manual capsulorhexis & ultrasound phacoemulsification (n = 66); Group-B femtosecond-laser assisted capsulorhexis and lens fragmentation (n = 67), employing the LenSx laser (Alcon Surgical, Ft. Worth, TX). All cases were evaluated for refraction, visual acuity, keratometry, tomography, pachymetry, endothelial cell counts, intraocular pressure, and type of intraocular lens (IOL) implanted. The groups were matched for age, gender, pre-operative vision metrics, and cataract grade, and were followed up to 1 year. RESULTS: In group-A post-operative uncorrected distance visual acuity (UDVA) was 20/20 or better in 61.5 % and 20/25 or better in 78.5 % of the eyes. The femtosecond laser group-B had improved outcomes (p = 0.075 and p = 0.042, respectively): post-operative UDVA was 20/20 or better in 62.7 % of the eyes and 20/25 or better in 85.1 %. Linear regression scatterplots of achieved versus attempted spherical equivalent had excellent regression coefficients (r (2) = 0.983 in group-A and 0.979 in group-B). There were 75.2 % cases in group-A and 80.6 % in group-B (p = 0.8732) within +/-0.50 D of targeted refractive equivalent. Slight trend of under-correction was noted in group-A. Average residual manifest cylinder in the toric subgroup-A was -0.50 D (95 % Limit-of-Agreement (LoA) = -0.78 D), and in toric subgroup-B -0.45 D (LoA = -0.45 D). CONCLUSIONS: Mean spherical equivalent refraction and visual acuity are comparable with laser cataract surgery compared with manual capsulorhexis & ultrasound phacoemulsification. Improved astigmatism correction may be among the benefits of femtosecond laser-assisted cataract surgery. Transient corneal edema may be a first day transient disadvantage in femtosecond laser-assisted cataract surgery.

BACKGROUND: To compare intraocular pressure (IOP) changes following topical dexamethasone administration for 1 month in keratoconic versus normal eyes. METHODS: This is a retrospective, single-center, non-randomized case series evaluation of 350 eyes. Two groups were formed: normal/control Group A (nA =73), eyes that underwent excimer laser photorefractive keratectomy; and keratoconic (KCN) Group B (nB =277), eyes that were subjected to partial laser photorefractive keratectomy combined with collagen cross-linking (The Athens Protocol). All eyes received the same post-operative regimen of topical dexamethasone 0.1 % for at least 1 month. Goldmann applanation tonometry IOP readings and central corneal thickness (CCT) measurements were monitored. Cases with induced ocular hypertension (OHT, defined as post-operative IOP higher than 21 mmHg), were identified and correlated to refractive procedure, gender, and corneal thickness. RESULTS: At 4 weeks postoperatively, OHT was noted on 27.4 % (20 /73 eyes) in Group A, and 43.7 % (121 /277 eyes) in KCN Group B, (p <0.01). Six months post-operatively (following 5-months of discontinuing topical dexamethasone treatment and commencing treatment of IOP-lowering medications), OHT rate was 1.8 % in Group A and 3.9 % in the KCN Group B. CONCLUSION: This study demonstrates a potentially significant pre-disposition of keratoconic eyes to the development of steroid-induced OHT.

Dry eye is a multifactorial, progressive, and chronic disease of the tears and ocular surface. The disease is multi-factorial and has intermittent symptoms. Discomfort, visual disturbance, tear film instability with potential damage to the ocular surface, and increased tear film osmolarity are known associates. Dry eye is a common clinical problem for eye-care providers worldwide and there is a large number of clinical investigative techniques for the evaluation of dry eye. Despite this, however, there is no globally accepted guideline for dry eye diagnosis and none of the available tests may hold the title of the 'gold standard'. The majority of the techniques involved in the diagnosis of the disease, particularly for its early stages, has a large degree of subjectivity. The purpose of this article is to review existing dry eye investigative techniques and to present a new objective dry eye screening technique based on optical coherence tomography.