Morphological Features Among Gaussian, Sagittal, and Tangential Curvature Maps in Normal and Keratoconus Eyes Using Anterior Segment Optical Coherence Tomography.

PURPOSE: To investigate and compare the morphological features and differences among Gaussian, Sagittal, and Tangential anterior corneal curvature maps obtained with an anterior segment optical coherence tomographer combined with a Placido disc MS-39 device in keratoconus (KC) and normal eyes. METHODS: Prospective, cross-sectional study including 37 KC and 51 healthy eyes. The pattern of astigmatism and maximum keratometry (Kmax), keratometry at the thinnest point (Ktp) and 2 mm diameter (K 2mm ), and inferior-superior dioptric asymmetry values were obtained and calculated from Gaussian, Tangential, and Sagittal curvature maps using the MS-39 (CSO). RESULTS: In KC eyes, an asymmetric bowtie pattern was observed in 64.86% (24/37), 64.86% (24/37), and 0% in the Sagittal, Tangential, and Gaussian maps, respectively. In normal eyes, 51.0% (26/51), 51.0% (26/51), and 0% showed a symmetric bowtie pattern in the Sagittal, Tangential, and Gaussian maps, respectively. There was a significant difference for the variables Kmax, Ktp, and K 2mm inferior among the Gaussian, Tangential, and Sagittal maps in both normal and KC groups. Sensitivity discriminating between normal and KC eyes was 100%, 97.3%, and 90.9% and specificity was 94.1%, 100%, and 100% for Kmax coming from the Tangential, Gaussian, and Sagittal maps, respectively. CONCLUSIONS: Gaussian maps displayed significantly different morphological features when compared with Sagittal and Tangential maps in normal and KC eyes. Anterior curvature maps from Gaussian maps do not show the morphological pattern of symmetric bowtie in normal eyes nor asymmetric bowtie in KC eyes. Kmax from Gaussian maps are more specific, however less sensitive than Tangential maps in discriminating KC from normal eyes.

Repeatability of Corneal Deformation Response Parameters by Dynamic Ultra High-speed Scheimpflug Imaging in Normal and Keratoconus Eyes.

PURPOSE: To assess the repeatability of corneal dynamic response (CDR) parameters in normal and keratoconus (KC) eyes using ultra high-speed Scheimpflug imaging. METHODS: Prospective, comparative, observational study, including eyes of 112 patients that underwent high-speed Scheimpflug imaging analysis (Corvis ST, OCULUS). Twenty-one CDR parameters were evaluated to asses repeatability using: coefficient of repeatability (CR), coefficient of variation, intraclass correlation coefficient (ICC) and within-subject SD. Three consecutive measurements by the same operator were performed for each eye. RESULTS: There were no significant differences between the three consecutive measurements for all parameters in both normal and KC eyes. 71.42% (15 of the 21 parameters evaluated) and 85.71% (18 of the 21 parameters) were highly repeatable in the normal and KC group, respectively. The tomographic biomechanical index (TBI), corneal biomechanical index (CBI), and stiffness parameter (SPA1) showed an ICC of 0.978, 0.954, and 0.958 in normal and 0.982, 0.892, and 0.978 in KC eyes, respectively. The CR in normal eyes for TBI, CBI, and SPA1 were 0.169, 0.242, and 14.12, respectively, and for KC eyes 0.06, 0.23, and 13.64, respectively. CONCLUSIONS: Most of the corneal dynamic response parameters were highly repeatable in normal and KC eyes.

Histopathology of Failed Descemet Membrane Endothelial Transfer.

OBJECTIVES: To describe the postmortem histologic features after an unsuccessful Descemet membrane endothelial transfer (DMET) and assess any potential clinical implications. METHODS: Postmortem, an eye from a patient who previously underwent unsuccessful DMET for pseudophakic bullous keratopathy (PPBK) was harvested and processed for morphologic evaluation. RESULTS: Clinically and histologically, the host cornea showed evidence of diffuse stromal edema. Although the edges of the surgical descemetorhexis were well visualized, there was no evidence of endothelial migration or repopulation of the posterior stroma from any direction. A multilayered, retrocorneal membrane was present that appeared to originate from the trabecular meshwork. CONCLUSIONS: Descemet membrane endothelial transfer and "descemetorhexis alone" may be insufficient treatment for eyes operated on for PPBK, that is, eyes with a significantly depleted or dysfunctional endothelium.

Intracorneal Inlays for the Correction of Presbyopia.

The current nonsurgical approaches for the correction of presbyopia are spectacles or contact lenses or the use of pharmaceuticals to create an artificial pupil and/or to stimulate residual accommodation. Refractive surgical procedures use a monovision approach and/or a multifocal corneal laser ablation with or without the induction of negative spherical aberration to improve near vision. More recently, new surgical approaches include intracorneal inlays. Inlay approaches include increasing corneal curvature alone, implanting a multifocal inlay, or by implanting a small aperture device that functions as a pinhole to restore unaided near and intermediate visual acuity. This review presents an analysis of the history and development of the various inlay approaches designed to improve presbyopia. Unlike other refractive surgical approaches, these newer techniques are removable. Each has its advantages and disadvantages.

Leak-Free Clear Corneal Incisions in Human Cadaver Tissue: Femtosecond Laser-Created Multiplanar Incisions.

OBJECTIVES: To evaluate femtosecond (FS) laser-assisted leak-free clear corneal incisions (CCI) and paracentesis (P) in human eyes of deceased donors. METHODS: Multiplanar CCI and P were created using an FS laser on human eyes of deceased donors (whole globe and corneal rims). Laser settings were programmed to multiplanar for CCI and single plane for P. Corneas were imaged by optical coherence tomography (OCT) and evaluated for leak by Seidel testing at various intraocular pressure (IOP) levels, and the wound was manipulated to mimic cataract surgery. Corneal endothelium cell damage and histological architecture were evaluated by microscopy. RESULTS: The corneal incision software of the FS laser was used to create homogeneous CCI and P incisions. Morphological changes assessed by OCT and light microscopy/scanning electron microscopy showed consistent true multiplanar incisions with predefined intersecting planes. All Seidel testing was negative, indicating that FS laser-assisted incisions did not leak. Trypan blue stain of the endothelial surface showed limited cell damage from the FS laser incisions. CONCLUSIONS: The FS laser-created incisions corresponded well with the treatment plans, as evidenced by true multiplanar architecture. Incisions were sharply demarcated and demonstrated limited cell damage. No postprocedure leaking at extreme IOP or postcataract surgery-simulated conditions was noted. The FS laser may potentially reduce postoperative complications, such as infections that may be associated with CCI.

Histopathologic Features of Descemet Membrane Endothelial Keratoplasty Graft Remnants, Folds, and Detachments.

PURPOSE: To describe the histologic features of postmortem eyes after Descemet membrane endothelial keratoplasty (DMEK) and their potential clinical implications. DESIGN: Histopathologic study. PARTICIPANTS: Eleven postmortem DMEK corneas of 8 patients who underwent surgery for Fuchs endothelial dystrophy, with an average postoperative time of 4±1.9 years (range, 7 months-6.5 years). METHODS: Eleven corneas transplanted with a DMEK graft were procured after death and processed for light microscopy evaluation. MAIN OUTCOME MEASURES: Histologic findings at the donor-host interface and at the host edge. RESULTS: Of the 11 corneas available for analysis, 9 showed normal anatomic features in the corneal center; that is, the donor-host interface resembled that of a virgin eye. One eye also had an anatomically normal periphery, but the remaining 10 eyes showed specific abnormalities in the periphery. Nine demonstrated overlapping of the DMEK graft onto the host edge of the descemetorhexis (and in 6 of these, the overlapping tissue showed a contracted inward fold at its peripheral edge with scar tissue); 1 eye showed a dense, acellular scar overlying a portion of the DMEK graft that clinically had shown a detachment followed by spontaneous adherence; 3 eyes showed subtle graft folds with scar tissue anteriorly; in 2 eyes (of the same patient), the anterior banded layer of the host Descemet membrane (DM) was still in situ across the cornea (both of these eyes had required rebubbling); and 2 eyes showed host DM remnants within the corneolimbal tunnel incision that may have interfered with incisional wound healing. CONCLUSION: Incomplete host DM removal may relate to postoperative DMEK graft detachment and wound instability. Graft detachments may reattach with interface scarring. Rebubbling procedures may be performed within 4 to 6 weeks, before portions of the detached graft scar. Subtle DMEK graft folds may explain subjective reports of monocular diplopia.

Penetrating and Intrastromal Corneal Arcuate Incisions in Rabbit and Human Cadaver Eyes: Manual Diamond Blade and Femtosecond Laser-Created Incisions.

OBJECTIVES: To compare morphologic differences between freehand diamond or femtosecond laser-assisted penetrating and intrastromal arcuate incisions. METHODS: Freehand diamond blade, corneal arcuate incisions (180° apart, 60° arc lengths) and 150 kHz femtosecond laser (80% scheimpflug pachymetry depth corneal thickness) arcuate incisions were performed in rabbits. Intrastromal arcuate incisions (100 µm above Descemet's membrane, 100 µm below epithelium) were performed in rabbit corneas (energy 1.2 µJ, spot line separation 3 × 3 µm, 90° side cut angle). Eyes were examined by slit lamp and light microscopy up to 47 days post-procedure. Freehand diamond blade penetrating incisions, and femtosecond laser penetrating and intrastromal arcuate incisions (energy 1.8 µJ, spot line separation 2 × 2 µm) were performed in cadaver eyes. Optical coherence tomography was performed immediately after surgery and the corneas were fixed for light scanning and transmission electron microscopy. RESULTS: The rabbit model showed anterior stromal inflammation with epithelial hyperplasia in penetrating blade and laser penetrating wounds. The laser intrastromal and penetrating incisions showed localized constriction of the stromal layers of the cornea near the wound. In cadaver eyes, penetrating wound morphology was similar between blade and laser whereas intrastromal wounds did not affect the cornea above or below incisions. CONCLUSION: Penetrating femtosecond laser arcuate incisions have more predictable and controlled outcomes shown by less post-operative scarring than incisions performed with a diamond blade. Intrastromal incisions do not affect uncut corneal layers as demonstrated by histopathology. The femtosecond laser has significant advantages in its ability to make intrastromal incisions which are not achievable by traditional freehand or mechanical diamond blades.

Intracorneal Inlays for the Correction of Ametropias.

Various materials have been placed in the corneal stroma to modify a spherical refractive error (usually hyperopic). As the surgical procedures evolved to simplify the insertion process so has the quality and biocompatibility of the implanted materials. Failures have been due to excessive inlay dimensions, bioincompatibility of the materials used, poor choice of test model, or combinations of the above. We present a thorough analysis of the history of the intracorneal inlay and the materials and techniques used up to and including the current materials and techniques available for the correction of spherical refractive errors.

Moderate keratoconus with thick corneas.

PURPOSE: To describe two patients with moderate keratoconus and a corneal thickness exceeding 600 µm at the thinnest point. METHODS: Case report. RESULTS: In the first case, the steepest keratometric power was 51.50 diopters (D) in the right eye and 53.4 in the left eye and the thickness at the thinnest point was 658 and 625 µm, respectively. In the second case, the steepest keratometric power was 46.70 D in the right eye and 49.60 D in the left eye and the thickness at the thinnest point was 618 and 608 µm, respectively. CONCLUSIONS: Keratoconus may develop despite a very thick cornea, reinforcing the idea that biomechanical changes can signify an important factor in the development and progression of this pathology.

Visual acuity outcomes in eyes with flat corneas after PRK.

PURPOSE: To evaluate the impact of corneal curvatures less than 35 diopters (D) after photorefractive keratectomy (PRK) on visual acuity outcomes. METHODS: Visual acuity outcomes of 5,410 eyes that underwent PRK from January 2006 to November 2010 were retrospectively analyzed for the impact of postoperative corneal curvatures on visual outcomes. All procedures were performed on a single platform (Allegretto 200Hz excimer laser; Alcon Laboratories, Inc., Irvine, CA). Main outcome measures were postoperative corrected distance visual acuity (CDVA) and loss of CDVA. RESULTS: Corneas with a measured or a calculated postoperative flat meridian less than 35 D and those with a measured postoperative steep meridian less than 35 D had worse postoperative CDVA than corneas with meridians of either 35 D or more (P ≤ .021). However, the preoperative CDVA was worse in the flatter curvatures in all comparisons performed (P ≤ .024). Consequently, the measured or calculated meridian curvature had no effect on CDVA loss (P ≥ .074). CONCLUSION: Postoperative corneal keratometry values (flat and steep meridians) less than 35 D did not have a predictive effect on the risk of losing visual acuity following myopic PRK performed on the Allegretto 200Hz excimer laser.

Short-term cell death and inflammation after intracorneal inlay implantation in rabbits.

PURPOSE: To investigate the cell death and inflammatory response to insertion of the KAMRA inlay (AcuFocus Inc) for presbyopia. METHODS: Twenty-four rabbits were included in the study. Each rabbit had pockets generated in both corneas with a femtosecond laser. One eye of each rabbit had an inlay inserted into the pocket and the opposite control eye had the pocket dissected. Eight rabbits were studied at 24 hours, 48 hours, or 6 weeks after surgery. Tissue sections were analyzed with TUNEL assay to detect cell death and immunohistochemistry for CD11b to detect monocytes as a marker of inflammation. RESULTS: The inlay group had significantly more stromal cell death than the control group at 48 hours after surgery (P=.038). At 24 hours and 6 weeks after surgery, no significant difference was noted in stromal cell death between the inlay and control groups. Significantly more CD11b+ cells were noted in the stroma in the inlay group compared to the control group at 24 and 48 hours after surgery (P=.025 and P=.001, respectively). However, at 6 weeks after surgery, no significant difference in CD11b+ cells was observed between the control and inlay groups (P=.05). CONCLUSIONS: Although an early increase in stromal cell death and inflammation occurred in eyes that underwent femtosecond laser pocket creation and KAMRA inlay insertion compared to a control group with the pocket only, no significant difference was noted between the inlay and control groups in stromal cell death or inflammation at 6 weeks after surgery.

The false positive rates for detecting keratoconus and potential ectatic corneal conditions when evaluating astigmatic eyes with Scheimpflug Technology.

PURPOSE: To quantify the false positive rates for keratoconus (KC) and potential ectatic corneal conditions in highly astigmatism eyes when using published parameters/indices obtained from the Pentacam and Galilei units. SETTING: Oftalmosalud Instituto de Ojos, Lima, Peru. DESIGN: Prospective cohort study. METHODS: 67 consecutive eyes with corneal astigmatism > 1.5 D, with a minimum follow ups of 36 months after an uneventful LASIK procedure were included. Indices for KC and other potential ectatic corneal conditions (subclinical KC, forme fruste KC, suspect KC) were obtained using the Pentacam and Galilei Scheimpflug cameras. MAIN OUTCOME MEASURES: The false positive rates for KC and potential ectatic corneal conditions were measured. Cut off values provided by previous studies and company-based parameters were used to assess the rate of false positivity. RESULTS: The range of false positive rates for a KC diagnosis depending on the lowest and highest cutoff values were: index of height decentration (61% - 1%), index of surface variance (76% - 0%), Posterior elevation (55% - 0%), maximum Ambrosio Relational thickness (100% - 13%), Belin Ambrosio enhanced ectasia display total deviation value (100% - 4%), Average pachymetric progression index (69% - 3%), Pachymetry at the thinnest point (58% - 1%), CSI Center Surround Index (100%), Differential sector index (51%). CONCLUSION: The false positive rates for KC and ectatic corneal conditions vary dramatically depending on the cut-off values used. Some indexes used for diagnosis of potential ectatic corneal conditions are inaccurate in normal, highly astigmatic eyes.

Acute Hydrops After Bowman Layer Transplantation for Keratoconus May Indicate that Descemet Membrane Rupture Is Secondary to Hydrops.

PURPOSE: The aim of this study was to review the postoperative course and imaging features of 7 eyes that presented with corneal hydrops after Bowman layer (BL) transplantation was performed for advanced keratoconus to determine the potential mechanisms of hydrops formation. METHODS: A retrospective analysis was performed of 7 eyes of 5 patients with advanced keratoconus that underwent midstromal BL transplantation at 2 tertiary referral centers and developed acute corneal hydrops on average 64 (±30) months (range 14-104 months) postoperatively. Corneal tomography and anterior segment optical coherence tomography (AS-OCT) images were reviewed to document the postoperative and posthydrops course. RESULTS: For all eyes, the post-BL transplantation course was uneventful until hydrops development. Despite stable postoperative topographies in 5 of 7 eyes, eyes developed hydrops with typical hypodense areas on AS-OCT that were limited to the stromal layers posterior to the BL graft. With AS-OCT (6/7 eyes), 2 eyes showed a break in Descemet membrane, whereas Descemet membrane was intact across the cornea in 2 eyes; in 2 eyes, the images were inconclusive. All patients admitted to continued eye rubbing, and all but 1 had a clinically significant allergy and/or atopic constitution. Most eyes (5/7) showed a relatively quick (visual) recovery within 1 to 4 months after hydrops. CONCLUSIONS: Hydrops formation in keratoconic corneas after midstromal BL transplantation may indicate that a break in Descemet membrane is secondary to hydrops development (and not vice versa). With a midstromal BL graft in situ limiting hydrops dimensions, resolution of the hydrops seemed relatively quick with recovery to prehydrops visual acuity in most eyes.

Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the athens protocol.

PURPOSE: To evaluate a series of patients with corneal ectasia after LASIK that underwent the Athens Protocol: combined topography-guided photorefractive keratectomy (PRK) to reduce or eliminate induced myopia and astigmatism followed by sequential, same-day ultraviolet A (UVA) corneal collagen cross-linking (CXL). METHODS: Thirty-two consecutive corneal ectasia cases underwent transepithelial PRK (WaveLight ALLEGRETTO) immediately followed by CXL (3 mW/cm(2)) for 30 minutes using 0.1% topical riboflavin sodium phosphate. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, keratometry, central ultrasonic pachymetry, corneal tomography (Oculus Pentacam), and endothelial cell counts were analyzed. Mean follow-up was 27 months (range: 6 to 59 months). RESULTS: Twenty-seven of 32 eyes had an improvement in UDVA and CDVA of 20/45 or better (2.25 logMAR) at last follow-up. Four eyes showed some topographic improvement but no improvement in CDVA. One of the treated eyes required a subsequent penetrating keratoplasty. Corneal haze grade 2 was present in 2 eyes. CONCLUSIONS: Combined, same-day, topography-guided PRK and CXL appeared to offer tomographic stability, even after long-term follow-up. Only 2 of 32 eyes had corneal ectasia progression after the intervention. Seventeen of 32 eyes appeared to have improvement in UDVA and CDVA with follow-up >1.5 years. This technique may offer an alternative in the management of iatrogenic corneal ectasia.

Interface fluid syndrome after bioptics.

PURPOSE: To report an unusual case of interface fluid syndrome after refractive surgery. METHODS: A 37-year-old man with high myopia underwent a planned bioptics procedure including creation of a corneal flap using a mechanical microkeratome and concurrent anterior chamber phakic intraocular lens implantation; excimer laser ablation was not performed at this time. RESULTS: Postoperatively, the patient developed corneal edema and was referred to our department. Interface fluid syndrome was confirmed using optical coherence tomography; the mechanism was due to endothelial cell pump dysfunction. CONCLUSIONS: This is the first report to document interface fluid syndrome following a planned bioptics procedure.

Evaluation of a risk factor scoring system for corneal ectasia after LASIK in eyes with normal topography.

PURPOSE: To assess a previously published risk score system for predicting postoperative LASIK ectasia in eyes with normal preoperative topography. METHODS: A retrospective review of one surgeon's LASIK database was performed for eyes with Randleman ectasia risk scores based on patient age <30 years, preoperative central corneal thickness <510 microm, residual stromal bed thickness <300 microm, and/or a preoperative manifest refraction spherical equivalent >-8.00 diopters that had a minimum follow-up of 1 year. RESULTS Of 1702 eyes with myopic errors and normal topographies, 35 (2.0%) eyes had a combined risk score between 5 and 9 points, 92 (5.4%) eyes had a combined risk score of 4 or higher, and 208 (12.2%) eyes had a combined score of 3 or higher. None of these eyes developed ectasia, whereas 3 eyes with preoperative topographic keratoconus with no other risk factors developed ectasia. CONCLUSIONS: The current risk score system would have eliminated 5.4% of eyes with 4 or more points from LASIK surgery, and would have also required the surgeon to advise an additional 6.8% of eyes with a score of 3 that they were at "moderate risk" and should "proceed with caution." In eyes with normal preoperative topographies, the scoring system may not accurately predict whether patients are at increased risk for developing postoperative LASIK ectasia.

Femtosecond applications for anterior segment surgery.

PURPOSE: To review the currently available femtosecond lasers that are used for anterior segment surgery and to compare those lasers with mechanical microkeratomes. METHODS: The author reviewed the literature and websites of the manufacturers of femtosecond lasers to compare the hardware and software features of each system. A further review of the mechanical microkeratome literature and how these instruments compare with femtosecond lasers was performed. RESULTS: The known and published outcomes and risks of using a mechanical microkeratome are compared in tabular format with femtosecond lasers. The many applications of femtosecond laser technology for anterior segment surgery are summarized. New risks and complications associated with femtosecond lasers not found with mechanical microkeratomes are discussed. CONCLUSIONS: Femtosecond laser technology has greatly improved on the ability to perform numerous anterior segment procedures that cannot be performed with mechanical microkeratomes. The increased predictability and safety of femtosecond laser in situ keratomileusis flap creation over mechanical microkeratomes are now well accepted.

Correlation between lens thickness and lens density in patients with mild to moderate cataracts.

PURPOSE: To determine the relationships between lens thickness (LT), lens density and anterior segment parameters in patients with mild to moderate cataracts. SETTING: Oftalmosalud Instituto de Ojos, Lima, Perú. DESIGN: Prospective, single-centre, cross-sectional study. METHODS: 169 eyes with age-related mild to moderate cataracts had lens density assessed using the Lens Opacification Classification System III, the built-in Pentacam HR Nucleus Staging software and ImageJ software. LT and axial length (AL) were measured with the IOLMaster 700, and angle parameters were measured using anterior segment optical coherence tomography. Pearson correlation coefficients and Kruskal-Wallis tests were used for statistical analyses. RESULTS: Nuclear colour score was the only clinical parameter with a weak significant correlation with LT (r=0.24, p=0.003) after accounting for age, AL, gender and anterior chamber depth (ACD). The maximum value of average lens density and the mean nuclear density were significantly correlated with LT (r=0.24, p=0.003 and -0.17, p=0.03, respectively) after controlling for the same factors. Central LT greater than 4.48 mm was present in 54.5% of the eyes with a nuclear opalescence grade 1. CONCLUSIONS: LT is independent of lens density in mild to moderate cataracts after accounting for age, AL, ACD and gender contrary to previous studies.

A prospective, contralateral eye study comparing thin-flap LASIK (sub-Bowman keratomileusis) with photorefractive keratectomy.

PURPOSE: To determine the differences in the visual results, pain response, biomechanical effect, quality of vision, and higher-order aberrations, among other parameters, in eyes undergoing either photorefractive keratectomy (PRK) or thin-flap LASIK/sub-Bowman keratomileusis (SBK; intended flap thickness of +/-100 microm and 8.5-mm diameter) at 1, 3, and 6 months after surgery. DESIGN: A contralateral eye pilot study. PARTICIPANTS: Fifty patients (100 eyes) were enrolled at 2 sites. METHODS: The mean preoperative spherical refraction was -3.66 diopters (D) and the mean cylinder was -0.66 D for all eyes. Eyes in the PRK group underwent 8.5-mm ethanol-assisted PRK, whereas in eyes in the SBK group, an 8.5-mm, (intended) 100-microm flap was created with a 60-kHz IntraLase femtosecond laser (Advanced Medical Optics, Santa Ana, CA). All eyes underwent a customized laser ablation using an Alcon LADARVision 4000 CustomCornea excimer laser (Alcon Laboratories, Fort Worth, TX). MAIN OUTCOME MEASURES: Preoperative and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity (UCVA), corneal topography, wavefront aberrometry, retinal image quality, and contrast sensitivity. Patients completed subjective questionnaires at each visit. RESULTS: One- and 3-month UCVA results showed a statistically significant difference: SBK, 88% 20/20 or better vs. 48% 20/20 or better for PRK. At 6 months, UCVA was 94% 20/20 or better for PRK and 92% for SBK. At 1 and 3 months, the SBK group had lower higher-order aberrations (coma and spherical aberration; P