Use of the Three-dimensional Viewing System and Microscope Tilting to Extend the Peripheral Retinal View.

PURPOSE: To describe and evaluate the effectiveness of the microscope and lens tilting technique associated with the three-dimensional viewing system for improving the peripheral retinal view in noncontact lens vitreoretinal surgeries. METHODS: Prospective, single-center, single-surgeon, consecutive case series of 25 patients undergoing vitrectomy for macular surgeries with three-dimensional visualization system. At the end of each surgery, the microscope and the noncontact lens were rotated by 20° in a direction opposite to the rotation of the eye to extend the peripheral visual field. RESULTS: Microscope and lens tilting technique extended the edge of the peripheral viewing field relative to its position with the microscope untilted, by 1.72 mm (±0.37) for the superior retina and 1.93 mm (±0.42) for the inferior retina (P < 0.0001). The ora serrata was visualized in 33% and 0% of cases for the superior retina and 91% and 36% of cases for the inferior retina, in tilted and nontilted microscope positions, respectively (P < 0.01). CONCLUSION: Microscope and lens tilting could be useful to extend the peripheral visual field of view in retinal surgery. The three-dimensional system allowed to maintain surgeon comfort and posture during surgery.

Decreased Corneal Sensation and Subbasal Nerve Density, and Thinned Corneal Epithelium as a Result of 360-Degree Laser Retinopexy.

PURPOSE: To assess the effects of 360-degree laser retinopexy on human corneal subbasal nerve plexus and to investigate correlations among corneal subbasal nerve plexus density, corneal epithelial thickness, and corneal sensitivity. DESIGN: Prospective, observational, nonrandomized study. PARTICIPANTS: A total of 15 eyes of 15 patients who underwent pars plana vitrectomy (PPV) with 360-degree laser retinopexy for retinal detachment (RD) and 15 eyes of 15 patients who underwent PPV for macular hole (MH) without laser treatment. METHODS: Corneal sensation, corneal epithelial thickness, and corneal subbasal nerve plexus density were assessed before surgery and 6 months after surgery via in vivo confocal microscopy, anterior segment optical coherence tomography (AS-OCT), and Cochet-Bonnet esthesiometry (Luneau Ophthalmologie, Paris, France). MAIN OUTCOME MEASURES: Corneal subbasal nerve plexus density, corneal epithelium thickness, and central corneal sensitivity. RESULTS: Compared with baselines values, the mean subbasal nerve density (P < 0.001), mean corneal epithelium thickness (P = 0.006), and mean corneal sensitivity (P < 0.001) in the RD group were significantly decreased 6 months after surgery by 74.3%, 4.7%, and 56.6%, respectively. Conversely, in the MH group there were no significant differences in the mean subbasal nerve density (P = 0.34), mean corneal epithelial thickness (P = 0.19), and mean corneal sensitivity (P = 0.42) between preoperative and 6-month postoperative values (0.7%, 0.4%, and 0.8%, respectively). The postoperative decrease in corneal subbasal nerve density after laser retinopexy was associated with a decrease in corneal epithelium thickness (r(2) = 0.42; P = 0.006) and a decrease in corneal sensitivity (r(2) = 0.48; P = 0.004). The postoperative decrease in corneal sensitivity poorly correlated with the decrease in corneal epithelial thickness (r(2) = 0.24; P = 0.045). Postoperative corneal nerve density decreased as total laser energy increased (r(2) = 0.51; P = 0.002). CONCLUSIONS: Subbasal corneal nerve plexus density decreases after 360-degree laser retinopexy and is accompanied by epithelium thinning and decreased corneal sensation. Surgeons should eschew heavy confluent retinal laser treatment, and corneal sensitivity should be assessed postoperatively to determine whether significant anesthesia has occurred. In such instances, prophylactic measures may be warranted against the development of neurotrophic ulcers.

Anatomic Predictive Factors of Acute Corneal Hydrops in Keratoconus: An Optical Coherence Tomography Study.

PURPOSE: To define the optical coherence tomography (OCT) corneal changes predisposing to acute corneal hydrops among patients with advanced keratoconus. DESIGN: Retrospective cohort study. PARTICIPANTS: A total of 191 advanced keratoconic eyes from 191 patients with advanced keratoconus cases were studied. METHODS: Data collected from patients with advanced keratoconus cases were studied during a minimum period of 24 months of follow-up. High-resolution Fourier-domain corneal OCT (5 µm of axial resolution) and corneal topography were performed every 4 months during the follow-up. Several anatomic features at the keratoconus cone were analyzed with OCT, including epithelial and stromal thicknesses, the aspect of Bowman's layer, the presence of Vogt's striae, and stromal opacities. A comparative analysis between anatomic corneal features in eyes that developed corneal hydrops and those that did not develop this complication during the follow-up was performed. MAIN OUTCOME MEASURES: Evaluation of anatomic corneal changes at risk of developing a corneal hydrops on the basis of OCT findings. RESULTS: Eleven cases of corneal hydrops (5.8%) occurred in our series during a mean follow-up of 30 months (24-36 months). All of these patients were male and younger (23.7±5.9 years) than patients with no acute keratoconus (32.7±11.3 years). Increased epithelial thickening with stromal thinning at the conus and the presence of anterior hyperreflectives at the Bowman's layer level were significantly associated with corneal hydrops, whereas the presence of corneal scarring was a preventive factor. At the healing stage, a pan-stromal scar occurs, with a significant stromal thickening and cornea flattening. CONCLUSIONS: Increased epithelial thickening, stromal thinning at the keratoconus cone, anterior hyperreflectives at the Bowman's layer level, and the absence of stromal scarring are associated with a high risk of developing corneal hydrops. These aspects should be taken into account by the clinician in the evaluation of keratoconus eyes and in the planning of corneal keratoplasty.

VITRECTOMY WITH INTERNAL LIMITING MEMBRANE PEELING FOR TRACTIONAL AND NONTRACTIONAL DIABETIC MACULAR EDEMA: Long-term Results of a Comparative Study.

PURPOSE: To compare the long-term outcomes of vitreomacular surgery in eyes with nontractional diabetic macular edema (DME) with those from eyes with tractional DME. METHODS: Retrospective comparative study from 55 consecutive patients (73 eyes). Twenty eyes were operated on for tractional DME and 53 eyes for nontractional DME unresponsive to laser photocoagulation or triamcinolone intravitreal injections. The best-corrected visual acuity, the central macular thickness, and the surgical complications were analyzed. RESULTS: The mean follow-up duration was 5.3 ± 2.4 years for the group with traction and 4.4 ± 1.7 years for the group without traction (P = 0.13). At 3 years, the mean logarithm of the minimum angle of resolution best-corrected visual acuity had improved significantly from 0.78 to 0.58 for the group without traction and from 0.75 to 0.45 for the group with traction (P < 0.001). At the final visit, there was no significant difference between the 2 groups in regard to visual or central macular thickness improvement (P = 0.447 and P = 0.742, respectively). The incidence of surgical complications was not significant between the two groups. The preoperative best-corrected visual acuity was the only predictive factor for the final best-corrected visual acuity. CONCLUSION: The results of vitrectomy were not different in terms of anatomical and visual outcomes and surgical complications between eyes without tractional DME and eyes with tractional DME.

Fourier-domain optical coherence tomography imaging in keratoconus: a corneal structural classification.

OBJECTIVE: To study corneal morphologic changes in a large keratoconic population and to establish a structural optical coherence tomography (OCT) classification. DESIGN: Cross-sectional, observational study. PARTICIPANTS: A total of 218 keratoconic eyes from 218 patients and 34 eyes from 34 normal subjects. METHODS: A Fourier-domain OCT system with 5-µm axial resolution was used. For each patient, 3 high-resolution scans were made across the keratoconus cone. All scans were analyzed by keratoconus specialists who were not given access to patients' clinical and topographic data, and who established an OCT classification. The reproducibility of the classification and its correlation with clinical and paraclinical characteristics of patients with keratoconus were evaluated. The OCT examinations were performed every 4 months to follow up structural corneal changes. MAIN OUTCOME MEASURES: Evaluation of the structural corneal changes occurring in keratoconus cases with various stages of severity based on OCT findings. RESULTS: Fourier-domain OCT classification containing 5 distinct keratoconus stages is proposed. Stage 1 demonstrates thinning of apparently normal epithelial and stromal layers at the conus. Stage 2 demonstrates hyperreflective anomalies occurring at the Bowman's layer level with epithelial thickening at the conus. Stage 3 demonstrates posterior displacement of the hyperreflective structures occurring at the Bowman's layer level with increased epithelial thickening and stromal thinning. Stage 4 demonstrates pan-stromal scar. Stage 5 demonstrates hydrops; 5a, acute onset: Descemet's membrane rupture and dilaceration of collagen lamellae with large fluid-filled intrastromal cysts; 5b, healing stage: pan-stromal scarring with a remaining aspect of Descemet's membrane rupture. The reproducibility of the classification was very high between the corneal specialist observers. Clinical and paraclinical characteristics of keratoconus, including visual acuity, corneal epithelium and stromal thickness changes, corneal topography, biomechanical corneal characteristics, and microstructural changes observed on confocal microscopy, were concordant with our OCT grading. CONCLUSIONS: Optical coherence tomography provides an accurate assessment of structural changes occurring in keratoconus eyes. These changes were correlated with clinical and paraclinical characteristics of patients. The established classification not only allows structural follow-up of patients with keratoconus but also provides insight into the pathogenesis of keratoconus and treatment strategies for future research.

Epiretinal membrane recurrence: incidence, characteristics, evolution, and preventive and risk factors.

BACKGROUND: To evaluate the incidence, evolution, clinical characteristics, possible risk factors or preventive factors, and visual outcomes of epiretinal membrane (ERM) recurrence. METHODS: Retrospective study of 440 consecutive patients (440 eyes) who underwent pars plana vitrectomy for ERM. The internal limiting membrane (ILM) was peeled in 266 cases, with the help of indocyanine green in 27 cases and brilliant blue in 45 cases. Cases of symptomatic ERM recurrence were reoperated. RESULTS: The incidence of ERM recurrence was 5% (22/440), and 2% of the patients were reoperated (9/440). Epiretinal membrane recurrence was symptomatic in 9 cases (41%) and asymptomatic in 13 cases (59%). ILM peeling was the only factor preventing ERM recurrence (adjusted odds ratio = 0.33, P = 0.026). The use of staining dyes did not prevent recurrence (adjusted odds ratio = 0.35, P = 0.338). In the case of ERM reproliferation, the absence of ILM peeling, the existence of ERM on the fellow eye, and poor visual acuity before surgery seemed to be associated with a high risk of symptomatic recurrence and reoperation. The mean duration for follow-up was 3.5 ± 1.7 years. CONCLUSION: ILM peeling not only reduces the likelihood of reproliferation of ERM but also seems to improve the visual prognosis of recurrent ERMs. The use of dyes did not reduce the rate of recurrence compared with when ILM was peeled without dyes.

Long-term outcomes of deep anterior lamellar versus penetrating keratoplasty for keratoconus.

AIMS: To compare the long-term outcomes of deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in keratoconus. METHODS: Retrospective comparative case series (228 DALKs and 274 PKs). A biphasic linear model was used to describe the postoperative outcome of the endothelial cell density (ECD). Visual acuity, specular microscopy, corneal topography and optical coherence tomography findings were recorded. RESULTS: Graft survival of the 502 keratoconus eyes was 96.7 at 10 years and 95.6% at 20 years. Visual acuity improved from 20/378±5.1 lines preoperatively to 20/32±2.1 lines at 30 months. The corneal ECD decreased from 2494±382 cells/mm2 to 1521±659 cells/mm2 at 10 years. The mean simulated keratometry increased from 44.88±2.54 D at 1 year to 46.60±3.0 D at 3 years. The mean follow-up was 103.4 months for DALKs and 106.1 months for PKs. The cumulated incidence of postoperative ocular hypertension requiring treatment was significantly higher in PKs than in DALKs. The early- and late-phase rates of ECD loss were significantly lower in DALKs than in PKs. These figures in DALKs were 50% of those observed in PKs. The simulated mean keratometry was significantly higher in DALKs than in PKs in the mid but not in the long term. No significant differences in visual acuity were observed between both groups. Manual dissection-DALK featured slower visual recovery than PK and big bubble-DALK, whereas big bubble-DALK and PK featured similar visual recovery. CONCLUSIONS: DALK featuring higher endothelial survival and lower risk of postoperative ocular hypertension may be superior to PK when indicated for keratoconus.

Comprehensive Assessment of Corvis ST Biomechanical Indices in Normal and Keratoconus Corneas with Reference to Corneal Enantiomorphism.

The aim of this study was to assess Corvis ST biomechanical indices in reference to corneal enantiomorphism. In a prospective observational cohort study, 117 eyes from 63 patients with normal or keratoconus corneas were assessed by three independent observers. In the control group (n = 62), no significant differences were observed between the three observers for all indices. The best reproducibility was obtained with pachymetry and the weakest with CBI. All indices but CBI and arc length featured COV < 10%. All indices except the PD and SSI correlated with pachymetry; all but Rad correlated with IOP. The comparison of the thinnest with the thickest corneas showed no significant differences for any index except pachymetry. In the keratoconus group (n = 55), loss of corneal enantiomorphism was confirmed for all indices except the arc length, velocity, and PD. Significant differences between both groups were found for all indices, even after adjustment for pachymetry and intraocular pressure. The CBI featured the best accuracy (92%), sensitivity (91%), and graphical relevance for keratoconus diagnosis. However, its reproducibility was weak in normal corneas and was strongly dependent on corneal thickness. The SSI was independent of corneal thickness, highly reproducible, and provided the expected enantiomorphism characteristics in both groups, making it a relevant biomarker of biomechanical corneal behavior.

Operative Digital Enhancement of Macular Pigment during Macular Surgery.

PURPOSE: To describe the feasibility of intraoperative digital visualization and its contribution to the enhancement of macular pigmentation visualization in a prospective series of macular surgery interventions. MATERIALS AND METHODS: A prospective, single-center, single-surgeon study was performed on a series of 21 consecutive cases of vitrectomy for various types of macular surgery using a 3D visualization system. Two optimized filters were applied to enhance the visualization of the macular pigment (MP). For filter 1, cyan, yellow, and magenta color saturations were increased. Filter 2 differed from filter 1 only in having a lower level of magenta saturation for the green-magenta color channel. RESULTS: Optimized digital filters enhanced the visualization of the MP and the pigmented epiretinal tissue associated with the lamellar and macular holes. In vitreomacular traction surgery, the filters facilitated the assessment of MP integrity at the end of surgery. Filter 1 enhanced MP visualization most strongly, with the MP appearing green and slightly fluorescent. Filter 2 enhanced MP visualization less effectively but gave a clearer image of the retinal surface, facilitating safe macular peeling. CONCLUSION: Optimized digital filters could be used to enhance MP and pigmented epiretinal tissue visualization during macular surgery. These filters open new horizons for future research and should be evaluated in larger series and correlated with intraoperative OCT.

Use of Digital Methods to Optimize Visualization during Surgical Gonioscopy.

Purpose: The aim of this study was to evaluate the efficacy of digital visualization for enhancing the visualization of iridocorneal structures during surgical gonioscopy. Methods: This was a prospective, single-center study on a series of 26 cases of trabecular stent implantation performed by the same surgeon. Images were recorded during surgical gonioscopy, and before stent implantation, with standard colors and with the optimization of various settings, principally color saturation and temperature and the use of the cyan color filter. Subjective analyses were performed by two glaucoma surgeons, and objective contrast measurements were made on iridocorneal structure images. Results: The surgeons evaluating the images considered the optimized digital settings to produce enhanced tissue visibility for both trabecular meshwork pigmentation and Schlemm's canal in more than 65% of cases. The mean difference in the standard deviation of the pixel intensity values was 37.87 (±4.61) for the optimized filter images and 32.37 (±3.51) for the standard-color images (p < 0.001). The use of a cyan filter provided a good level of contrast for the visualization of trabecular meshwork pigmentation. Increasing the color temperature highlighted the red appearance of Schlemm's canal. Conclusions: We report here the utility of optimized digital settings including the cyan filter and a warmer color for enhancing the visualization of iridocorneal structures during surgical gonioscopy. These settings could be used in surgical practice to enhance the visualization of the trabecular meshwork and Schlemm's canal during minimally invasive glaucoma surgery.

Long-term results of deep anterior lamellar versus penetrating keratoplasty.

OBJECTIVE: To compare deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in eyes with corneal diseases not involving the corneal endothelium (keratoconus, scars after infectious keratitis, stromal dystrophies, and trauma). DESIGN: Retrospective, comparative case series. PARTICIPANTS: One hundred forty-two consecutive DALK (DALK group; big-bubble technique or manual lamellar dissection using a slitlamp) and 142 matched PK (PK group). METHODS: Three models were used to describe the postoperative outcomes of the endothelial cell density. A joint regression model was used to predict long-term graft survival. Visual acuity, ultrasound pachymetry, specular microscopy, and optical coherence tomography (OCT) findings were recorded. MAIN OUTCOME MEASURES: Postoperative endothelial cell loss and long-term predicted graft survival. RESULTS: The average 5-year postoperative endothelial cell loss was -22.3% in the DALK group and -50.1% in the PK group (P<0.0001). The early- and late-phase annual rates of endothelial cell loss were -8.3% and -3.9% per year, respectively, in the DALK group and -15.2% and -7.8% per year in the PK group (P<0.001; biphasic linear model). The median predicted graft survival was 49.0 years in the DALK group and 17.3 years in the PK group (P<0.0001). The average visual acuity was lower in the manual dissection subgroup compared with the PK group (average difference, 1.0 to 1.8 line) and with the big-bubble subgroup (average difference, 2.2 to 2.5 lines). The average central corneal thickness at 12 months was 536 µm in the PK group, 523 µm in the big-bubble subgroup, and 562 µm in the manual dissection subgroup (P<0.001). The average thickness of the residual recipient stroma measured by OCT was 87±26 µm in the manual dissection subgroup. No correlation was found between this figure and logarithm of the minimal angle of resolution at any postoperative time point (P>0.05). CONCLUSIONS: Long-term, model-predicted graft survival and endothelial densities are higher after DALK than after PK. The big-bubble technique gives better results than manual dissection and PK. Compared with PK, manual dissection provides higher survival of both the corneal endothelium and graft, but lower visual acuity.

Paracentral retinal holes occurring after macular surgery: incidence, clinical features, and evolution.

AIM: To describe the incidence, clinical features, and evolution of paracentral retinal holes occurring after macular surgery. METHODS: A retrospective non-randomized study of 909 patients operated on for either a macular hole (MH, n = 400 patients) or an epiretinal membrane (ERM, n = 509 patients) between 2004 and 2009. Six patients (0.6%) developed a paracentral macular hole after surgery. Their clinical, auto-fluorescence, and optical coherence tomography (OCT) characteristics as well as their visual outcomes were studied. RESULTS: The mean age of patients was 70 years. Paracentral holes occurred approximately 5 weeks after surgery (with a range of 2-12 weeks). All patients were asymptomatic. Five patients underwent ILM peeling during initial surgery. Paracentral retinal holes were located superiorly to the fovea in three cases and temporally in the other three cases. Mean pre-operative BCVA was 20/200 and mean post-operative BCVA was 20/40. The eye where the eccentric MHs were closest to the fovea (inferior to 1 optic disc area) had the poorest final visual acuity. Autofluorescence imaging showed a bright fluorescence in paramacular holes. On OCT images, they were shown to be flat full-thickness holes. No treatment was attempted. No rhegmatogenous complications or choroidal neovascularization occurred in any of the patients. Mean follow-up was 2 years. CONCLUSIONS: In summary, paracentral MHs are uncommon complications which can occur at the site where ILM peeling has been initiated or completed. Except for the closest holes to fovea, they have good visual prognosis and do not require any treatment underlining the importance of initiating the ILM peeling as far as possible from the fovea.

Facilitating Role of the 3D Viewing System in Tilted Microscope Positions for Cataract Surgery in Patients Unable to Lie Flat.

PURPOSE: To assess the utility of the 3D viewing system in tilted microscope positions for the performance of cataract surgery in challenging positions, for patients with difficulty remaining supine. METHODS: Prospective, single-center, single-surgeon, consecutive case series of patients undergoing surgery in an inclined position. RESULTS: 21 eyes of 15 patients who had undergone surgery at inclined positions at angles of 20° to 80°, with a mean angle of 47.62°. Surgeon comfort was considered to be globally good. The surgeon rated red reflex perception and the impression of depth as good and stable in all cases. The operating time was slightly longer for patients inclined at angles of more than 50°. On the first day after surgery, BSCVA was 20/25 or better in all cases. No ocular complications occurred in any of the interventions. CONCLUSIONS: Due to the ocular-free design of the 3D system, the surgical procedure and the positioning of the surgeon remained almost identical to that for patients undergoing surgery in a supine position, maintaining the safety of the standard surgical approach.

Use of Black-and-White Digital Filters to Optimize Visualization in Cataract Surgery.

PURPOSE: To evaluate the effect of a black-and-white (BW) filter on the optimization of visualization at each stage of cataract surgery. METHODS: Prospective, single-center, single-surgeon, consecutive case series of 40 patients undergoing cataract surgery with BW filter. Surgical images and videos were recorded with and without the BW filter at each stage of cataract surgery. Contrast measurements of surgical images and subjective analysis of video sequences were performed. RESULTS: The surgeons assessed the BW filter to optimize the tissue visibility of capsulorhexis contours, hydrodissection fluid wave perception, the contrast of instruments through a nucleus during phaco-chop, and subincisional cortex contrast through the corneal edema. Despite the higher contrasts' value obtained with BW filter images during nucleus removal, posterior capsular polishing and viscous removal, the surgeons subjectively reported no significant advantage of using a BW filter. Standard color images were found to be better for localizing the limbal area during incision and for nucleus sculpture to assess groove depth. CONCLUSIONS: In conclusion, we describe here the potential indications for BW filter use at particular stages in cataract surgery. A BW filter could be used, with caution, in cases of poor visualization.

Early corneal pachymetry maps after cataract surgery and influence of 3D digital visualization system in minimizing corneal oedema.

PURPOSE: To describe the early topography of corneal swelling occurring after cataract surgery and to evaluate the impact of the three-dimensional (3D) digital visualization system in minimizing corneal oedema. METHODS: Prospective observational, single-centre, consecutive case series of 134 patients undergoing cataract surgery performed by the same surgeon, with either 3D or conventional visualization systems. Eyes were assigned to two groups based on their anterior chamber depth (group ACD ≤3 mm and group ACD >3 mm). Optical coherence tomography was performed to evaluate postoperative corneal swelling. RESULTS: Three corneal swelling profiles were identified on the first postoperative day type 1, limited corneal oedema near peripheral corneal incisions; type 2, dome-shaped corneal swelling spreading from the principal corneal incision and reaching the paracentral cornea; type 3, continuous oedema spreading from the principal incision to central cornea, with a generalized oedema predominating in the upper part of the cornea. On the first day after surgery, in group ACD ≤3 mm, visual acuity was significantly better in patients undergoing surgery with 3D visualization (0.023 vs 0.072 logMar, p = 0.014) with reduced central corneal thickening 17.3 µm (±3.2) in comparison with conventional visualization 44.0 µm (±9.3) (p = 0.0082). In group ACD >3 mm, no significant association was found between the use of the 3D system and pachymetry changes and early visual rehabilitation. On day 21 after surgery, no significant differences in corneal pachymetry values were observed between the two surgical approaches in both groups. CONCLUSIONS: We describe early postoperative corneal map profiles providing insight into the pathogenesis of postoperative corneal swelling and possible prevention strategies. By improving visualization of the narrow surgical space in patients with shallow anterior chambers, the 3D system could help to minimize postoperative corneal oedema.

25-, 23-, and 20-gauge vitrectomy in epiretinal membrane surgery: a comparative study of 553 cases.

PURPOSE: To compare the safety and functional outcomes of 25-gauge and 23-gauge (G) micro-incision vitrectomy surgery (MIVS) instrumentation with the standard 20-G vitrectomy system in the treatment of epiretinal membranes (ERM). METHODS: A retrospective comparative study of 553 consecutive cases with epiretinal membrane who underwent pars plana vitrectomy. Twenty-gauge, 25-gauge and 23-gauge vitrectomy was performed respectively in 347, 91, and 115 eyes. Surgery duration, visual acuity improvement, intraocular pressure variation, intraoperative and postoperative complications were analyzed. RESULTS: The mean surgical time in the 23-G group and in the 25-G group was shorter than in the 20-G group (P < 0.001). Visual improvement was higher 8 days postoperatively in the 25-G group than in the 20-G and 23-G groups (P = 0.035), but not at 6 weeks postoperatively (P = 0.186). In the 20-G group, the IOP increased significantly on the first day postoperatively (P < 0.001), while in the 23-G group, the IOP decreased on the first day postoperatively (P = 0.073). In the 25-G group, the IOP did not change significantly (P = 0.807). The incidence of complications was not statistically significant between the three groups. Retinal breaks were significantly related to the induction of posterior vitreous detachment, independent of the system gauge. CONCLUSION: In ERM surgery, 23-G and 25-G (MIVS) systems are as safe and effective as the 20-G system, and significantly reduce surgical time. Although the 25-G system provides an earlier visual improvement, the 23- and 25- gauge systems are comparable, and the selection will depend on the surgeon's preference.

Corneal and Epithelial Thickness Mapping: Comparison of Swept-Source- and Spectral-Domain-Optical Coherence Tomography.

OBJECTIVE: To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes. METHODS: 30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT. RESULTS: The central and minimum ET obtained with both devices were correlated: central ET, r = 0.86, p < 0.05; minimum ET, r = 0.72, p < 0.05. Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 µm on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, r = 0.994, p < 0.05; minimum CT, r = 0.995, p < 0.05. SS-OCT tended to overestimate these figures by 11 and 14 µm on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT. CONCLUSION: SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.

Contribution of Fourier-domain optical coherence tomography to the diagnosis of keratoconus progression.

PURPOSE: To determine the anatomic criteria for diagnosing keratoconus progression by corneal optical coherence tomography (OCT). SETTING: Quinze-Vingts National Ophthalmology Hospital, Paris, France. DESIGN: Prospective case series. METHODS: Scanning-slit corneal topography (Orbscan II) and Fourier-domain corneal OCT (RTVue) were performed in eyes with mild to moderate keratoconus (progressive or nonprogressive [stable] ectasia) at each examination to assess the keratoconus. Disease progression was defined as an increase of at least 1.0 diopter (D) in the steepest keratometry (K) measurement over 6 months. RESULTS: Of the 134 eyes of 134 patients with mild to moderate keratoconus, 98 had had progressive ectasia and 36 nonprogressive ectasia. The mean maximum K increased significantly in the progressive group (2.1 D ± 1.2 [SD], P < .0001) and remained constant in the stable group (-0.03 ± 0.39 D, P = .31). The mean thinnest corneal thickness increased significantly in the progressive group (-7.98 ± 9.3 µm, P < .0001) and remained constant in the stable group (-0.52 ± 4.21 µm, P = .22). The change in maximum K was significantly correlated with changes in the thinnest corneal thickness (r = -0.61, P < .0001). A cutoff value of -5 µm for the change in thinnest corneal thickness was identified on receiver operating characteristic curves as a threshold separating cases of progressive and stable keratoconus (area under the curve, 0.79; sensitivity, 68%; specificity, 89%). CONCLUSIONS: Topographic data partly reflected the structural changes occurring during the progression of corneal ectasia. Based on the pachymetric parameters provided by OCT, corneal and epithelial thinning was correlated with corneal deformation. The use of corneal OCT might therefore improve the diagnostic sensitivity for keratoconus progression.