Miguel A. Teus

Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics

PURPOSE: To evaluate the clinical features of keratoconus taking into consideration anterior corneal aberrations, internal astigmatism, and corneal biomechanical properties and to define a new grading system based on visual limitation. SETTING: Vissum Corporation, Alicante, Spain. DESIGN: Retrospective case series. METHODS: This multicenter study comprised consecutive keratoconic eyes with no previous ocular surgery or active ocular disease. Visual, refractive, corneal topography, and pachymetry outcomes were analyzed. Internal astigmatism was calculated by vectorial analysis. Corneal aberrations and corneal biomechanics characterized by the Ocular Response Analyzer were evaluated in some eyes. Correlations between clinical data and a linear multiple regression analysis for characterizing the relationship between visual limitation and objective clinical data were performed. RESULTS: This study comprised 776 eyes of 507 patients (age range 11 to 79 years) The mean keratometry (K) correlated significantly with logMAR corrected distance visual acuity (CDVA) (r = 0.591, P<.01), internal astigmatism (r = 0.497, P<.01), corneal asphericity (r = −0.647, P<.01), and several corneal higher‐order aberrometric coefficients (r≥0.603, P<.01). Significant correlations were found between some corneal aberrometric parameters and CDVA (r≥0.444, P<.01). Multiple regression analysis showed that CDVA was significantly correlated with the mean K, intraocular pressure, corneal resistance factor, and spherical equivalent (r2 = 0.69, P<.01). There were significant differences in mean K, internal astigmatism, and corneal higher‐order aberrations between 4 groups differentiated by visual limitation (P<.01). CONCLUSION: The visual limitation in keratoconus could be explained by different alterations that occur in these corneas and allowed development of a new grading system for this condition. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Mitomycin C in Corneal Refractive Surgery

Mitomycin C has played a deciding role in the current revival of excimer laser surface ablation techniques. We review the literature regarding mechanism of action of mitomycin C, histological effects on the cornea, and indications, dose, exposure time, and toxicity of mitomycin C in corneal refractive surgery. Mitomycin C is an alkylating agent with cytotoxic and antiproliferative effects that reduces the myofibroblast repopulation after laser surface ablation and, therefore, reduces the risk of postoperative corneal haze. It is used prophylactically to avoid haze after primary surface ablation and therapeutically to treat pre-existing haze. There is no definite evidence that establishes an exact diopter limit or ablation depth at which to apply prophylactic mitomycin C. It is usually applied at a concentration of 0.2mg/ml (0.02%) for 12 to 120 seconds over the ablated stroma, although some studies suggest that lower concentrations (0.01%, 0.002%) could also be effective in preventing haze when treating low to moderate myopia. This dose of mitomycin C has not been associated with any clinically relevant epithelial corneal toxicity. Its effect on the endothelium is more controversial: two studies report a decrease in endothelial cell density, but the majority of reports suggest that the endothelium is not altered. Regarding mitomycin Cs effect on keratocyte population, although animal studies report keratocyte depletion after its use, longer follow-up suggested that the initial keratocyte depletion does not persist over time.

Intraocular pressure as a risk factor for visual field loss in pseudoexfoliative and in primary open-angle glaucoma

OBJECTIVE To analyze the relationship between intraocular pressure (IOP) and visual field loss in patients with primary open-angle glaucoma (POAG) and in those with pseudoexfoliative glaucoma (PEXG). DESIGN A cross-sectional, observational study. PARTICIPANTS Thirty-one patients with PEXG and 31 patients with POAG that was newly diagnosed were included in this study. MAIN OUTCOME MEASURES The authors recorded the untreated IOP and the amount of the visual field loss, at presentation, in both study groups. RESULTS The authors found a significant relationship between IOP and visual field mean deviation (MD) index (P = 0.0001, r = 0.68) in PEXG but not in POAG eyes (P = 0.7). CONCLUSION The authors found that untreated IOP levels can explain the amount of visual field loss, as measured by the MD index, much better in patients with PEXG than in comparable patients with POAG. Thus, vulnerability of the optic nerve head to increased IOP appears to be different in these two diagnostic categories.

Outcome Analysis of Intracorneal Ring Segments for the Treatment of Keratoconus Based on Visual, Refractive, and Aberrometric Impairment

PURPOSE To analyze the outcomes of intracorneal ring segment (ICRS) implantation for the treatment of keratoconus based on preoperative visual impairment. DESIGN Multicenter, retrospective, nonrandomized study. METHODS A total of 611 eyes of 361 keratoconic patients were evaluated. Subjects were classified according to their preoperative corrected distance visual acuity (CDVA) into 5 different groups: grade I, CDVA of 0.90 or better; grade II, CDVA equal to or better than 0.60 and worse than 0.90; grade III, CDVA equal to or better than 0.40 and worse than 0.60; grade IV, CDVA equal to or better than 0.20 and worse than 0.40; and grade plus, CDVA worse than 0.20. Success and failure indices were defined based on visual, refractive, corneal topographic, and aberrometric data and evaluated in each group 6 months after ICRS implantation. RESULTS Significant improvement after the procedure was observed regarding uncorrected distance visual acuity in all grades (P < .05). CDVA significantly decreased in grade I (P < .01) but significantly increased in all other grades (P < .05). A total of 37.9% of patients with preoperative CDVA 0.6 or better gained 1 or more lines of CDVA, whereas 82.8% of patients with preoperative CDVA 0.4 or worse gained 1 or more lines of CDVA (P < .01). Spherical equivalent and keratometry readings showed a significant reduction in all grades (P ≤ .02). Corneal higher-order aberrations did not change after the procedure (P ≥ .05). CONCLUSIONS Based on preoperative visual impairment, ICRS implantation provides significantly better results in patients with a severe form of the disease. A notable loss of CDVA lines can be expected in patients with a milder form of keratoconus.

Ten-year Follow-up of Excimer Laser Surface Ablation for Myopia in Thin Corneas

PURPOSE To evaluate the long-term outcomes of excimer laser surface ablation performed on thin corneas. DESIGN Retrospective study. METHODS We included in the study 75 eyes (49 patients) with a preoperative central corneal thickness (CCT) thinner than 500 mum that had undergone surface ablation to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity (VA) and refraction, the predictability, corneal keratometry, safety, efficacy, and postoperative complications at the examinations 3 months and 1, 2, 5, and 10 years after surgery. RESULTS Preoperative CCT was 481.54 +/- 15.7 microm (range, 438 to 499 microm). Preoperative spherical equivalent was -6.12 +/- 2.67 diopters (D) (range, -2 to -14 D). The best spectacle-corrected VA significantly improved (P < .01) during the follow-up. The uncorrected VA showed significant improvement in all visits when compared with the 3-month postoperative visit. Both the sphere and cylinder showed a slight but significant regression (P < .01) only in the comparison between 3 months and 10 years after the surgery. Ten years after the surgery, 30 eyes (40%) were within 0.50 D and 43 eyes (57.33%) were within 1.00 D of emmetropia. The safety index improved over the 10 year period and was always higher than 0.9. The efficacy index remained stable around 0.8. The topography did not show signs of corneal ectasia and the keratometry showed no increase in corneal power. Thirty eyes (40%) needed enhancement. CONCLUSION Surface ablation seems to be safe and effective to correct myopia in corneas thinner than 500 microm, with stable visual and refractive outcomes in a 10-year follow-up.

Effect of mitomycin-C on the corneal endothelium during excimer laser surface ablation

PURPOSE: To study the effects of mitomycin‐C (MMC) on the corneal endothelium after surface ablation. METHODS: This prospective observer‐masked study comprised 40 consecutive patients (80 eyes) scheduled to have laser‐assisted subepithelial keratectomy (LASEK) to correct myopia. The patients were divided into 2 groups. Group 1 included 32 eyes in which the ablation depth was 50 μm or less and that received no MMC. Group 2 included 48 eyes in which the ablation depth exceeded 50 μm and were treated with intraoperative MMC 0.02% for 30 seconds over the ablated zone. Preoperatively and 3 months postoperatively, 3 photographs of the central cornea of each eye were obtained using specular microscopy. A masked observer evaluated the endothelial cell density and compared the results between groups and the preoperative versus the postoperative results within the same group. RESULTS: The mean patient age was 31.5 years ± 4.6 (SD) in Group 1 and 33.2 ± 7.9 years in Group 2 (P = .3). Within‐group comparison between the preoperative and postoperative endothelial cell density values showed a statistically significant increase in both groups. The mean values in Group 1 were 2462.5 ± 226.8 cells/mm2 preoperatively and 2562.5 ± 258.7 cells/mm2 postoperatively (P = .0001). The means in Group 2 were 2466.6 ± 294.1 cells/mm2 and 2525 ± 312.5 cells/mm2, respectively (P = .0008). The differences in endothelial cell counts between Group 1 and Group 2 preoperatively and postoperatively were not statistically significant (P = .9 and P =.5, respectively). CONCLUSION: A single intraoperative application of MMC 0.02% for 30 seconds after laser surface ablation did not seem to cause a substantial change in corneal endothelial cell density.

Causes of intrastromal corneal ring segment explantation: Clinicopathologic correlation analysis

PURPOSE: To determine the main causes of intrastromal corneal ring segment (ICRS) explantation and the relationship with the microscopic findings on the ICRS surface. SETTING: Vissum Corporation–Instituto Oftalmológico de Alicante, Alicante, Spain. METHODS: This study evaluated ICRS that were explanted in centers in Spain from 2000 to 2008. Clinical data (reasons for explantation, date of implantation/explantation, tunnel creation technique, ICRS type) and scanning electron microscopy findings on the ICRS surface (adherent tissue‐like material, cell deposits, protein) were documented. RESULTS: Intrastromal corneal ring segments were explanted from 58 eyes (47 patients). The main cause was extrusion (48.2% of explanted segments), followed by refractive failure (ie, poor refractive outcome) (37.9%), keratitis (6.8%; 3.7% culture positive), and corneal melting and perforation (6.8%). Scanning electron microscopy showed cells and cell debris on the ICRS explanted by extrusion, a clean surface on the ICRS explanted for refractive failure, and bacteria (cocci) in the case of proven infectious keratitis. CONCLUSIONS: The main cause of explantation was extrusion of the ICRS followed by refractive failure. There was a clear correlation between the cause of explantation and the microscopic findings on the ICRS. Extrusion was accompanied by inflammatory cells and cell debris on the ICRS surface. No inflammatory reaction was observed on the ICRS explanted for refractive failure. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Incidence of iris colour change in latanoprost treated eyes

Aims: To determine the incidence of increased iris pigmentation in eyes treated with chronic latanoprost. This is an observational, cohort study. Methods: The anterior segments of both eyes of 43 patients with glaucoma were photographed after unilateral latanoprost therapy. Two independent, masked observers analysed the slides of both eyes of the study participants, and compared the iris pigmentation of both eyes of each patient using a stereo viewer. Results: 30 patients (69.7%) had a definite acquired iridial anisochromia; 15 patients (50%) had increased superficial iris pigmentation with a “granular” appearance (type 1 change), and 15 patients (50%) had an increased “stromal pigmentation”—that is, the affected iris appeared darker than the fellow eye, but without a “granular” appearance (type 2 change). Conclusion: The incidence of increased iris pigmentation induced by latanoprost is much higher than previously reported. The high prevalence of mixed iris colour found in this population and the fact that the patients studied were undergoing unilateral therapy may explain these results.

Femtosecond Laser vs Mechanical Microkeratome for Hyperopic Laser In Situ Keratomileusis

PURPOSE To compare the outcomes of laser in situ keratomileusis (LASIK) performed with a femtosecond laser vs a mechanical microkeratome for the correction of low to moderate hyperopia. DESIGN Retrospective, nonrandomized, interventional, comparative case series. METHODS settings: Vissum Santa Hortensia, Madrid, Spain.study population and procedures: Patients who had undergone LASIK to correct their hyperopia using the 60-kHz IntraLase femtosecond laser were compared to age- and refraction-matched patients in whom the Moria M2 microkeratome was used. Visual and refractive results 3 months postoperatively were compared between both groups. RESULTS A total of 144 eyes were analyzed (72 in each group). Mean preoperative sphere was +3.45 ± 1.0 diopters (D) in the IntraLase group vs +3.18 ± 1.3 D in the M2 group (P = .1). Results 3 months postoperatively were: mean residual sphere, +0.44 ± 0.6D vs +0.72 ± 0.8 D (P = .02), respectively; uncorrected visual acuity (UCVA), 0.89 ± 0.2 vs 0.80 ± 0.2 (P = .04); best spectacle-corrected visual acuity (BSCVA), 0.96 ± 0.2 vs 0.92 ± 0.2 (P = .2); safety index, 0.97 ± 0.1 vs 0.98 ± 0.1 (P = .5); efficacy index, 0.89 ± 0.2 vs 0.84 ± 0.2 (P = .3). CONCLUSIONS Hyperopic LASIK performed with the IntraLase femtosecond laser seems to achieve better refractive results 3 months after the surgery compared to the M2 microkeratome, without significant differences in safety between both procedures.

Visual Outcomes of LASIK-Induced Monovision in Myopic Patients With Presbyopia

PURPOSE To evaluate binocular visual acuity (VA), contrast sensitivity, and stereopsis in myopic patients after laser in situ keratomileusis (LASIK)-induced monovision. DESIGN Prospective, observational study. METHODS We performed a prospective study of 37 consecutive patients older than 45 years who underwent bilateral myopic LASIK with planned monovision. At the 6-month postoperative visit, we evaluated distance and near binocular visual acuity, contrast sensitivity, and stereopsis. Binocular tests were done without spectacles (in monovision condition) and compared with the results obtained by repeating the same binocular tests with the same patients (serving as a control group) after spectacle correction of the residual myopic defect in the nondominant eye for distance tests (reverting monovision) and after spectacle correction of the presbyopia bilaterally for near tests (near best spectacle-corrected VA). RESULTS By inducing a mean residual spherical equivalent defect of -0.97 diopter in the nondominant eye, the patients achieved a mean near binocular uncorrected visual acuity (UCVA) of 0.74, a mean reading test binocular UCVA of 0.88 using an acceptable spontaneous reading distance (48 cm), and a mean distance binocular UCVA of 1.08. A slight decrease in contrast sensitivity and stereopsis was observed in monovision compared to full distance correction. CONCLUSIONS Monovision is a valid option for myopic patients with presbyopia who are considering LASIK. Good distance and near UCVAs can be obtained with this procedure.