Unsupervised feature extraction of anterior chamber OCT images for ordering and classification.

We propose an image processing method for ordering anterior chamber optical coherence tomography (OCT) images in a fully unsupervised manner. The method consists of three steps: Firstly we preprocess the images (filtering the noise, aligning and normalizing the resolution); secondly, a distance measure between images is computed for every pair of images; thirdly we apply a machine learning algorithm that exploits the distance measure to order the images in a two-dimensional plane. The method is applied to a large (~1000) database of anterior chamber OCT images of healthy subjects and patients with angle-closure and the resulting unsupervised ordering and classification is validated by two ophthalmologists.

A new methodology for the in vivo estimation of the elastic constants that characterize the patient-specific biomechanical behavior of the human cornea.

This work presents a methodology for the in vivo characterization of the complete biomechanical behavior of the human cornea of each patient. Specifically, the elastic constants of a hyperelastic, second-order Ogden model were estimated for 24 corneas corresponding to 12 patients. The finite element method was applied to simulate the deformation of human corneas due to non-contact tonometry, and an iterative search controlled by a genetic heuristic was used to estimate the elastic parameters that most closely approximates the simulated deformation to the real one. The results from a synthetic experiment showed that these parameters can be estimated with an error of about 5%. The results of 24 in vivo corneas showed an overlap of about 90% between simulation and real deformed cornea and a modified Hausdorff distance of 25 µm, which indicates the great accuracy of the proposed methodology.

Therapeutic sectorial full-thickness sclero-keratoplasty for recurrent fungal keratitis.

OBJECTIVE: To report the management of a severe and recurrent fungal keratitis that required repeated penetrating keratoplasties. Despite multiple topical, intraocular and systemic antifungal treatments, superotemporal hyphal infiltration repeatedly penetrated the corneal transplant causing continuous recurrences. Cultures collected before and during surgery isolated the same organism, Fusarium spp. CONCLUSION: Corneal infection extending to the sclera and internal angle structures is the main cause of recurrence of fungal keratitis after corneal transplantation. Sectorial full-thickness sclero-keratoplasty combined with a central penetrating keratoplasty should be a surgical technique to be considered in cases where these locations are suspected to be the source of recurrence. It enables a definitive elimination of the infection, with excellent final visual acuities. No postoperative complications were reported in this case.

Abnormal activation in the visual cortex after corneal refractive surgery for myopia: demonstration by functional magnetic resonance imaging.

OBJECTIVE: To try to correlate subjective photophobic symptoms with visual pathway modifications (from the retinal image to the visual cortex) after refractive surgery by exploring brain activation on photic stimulation. DESIGN: Noncomparative case series. PARTICIPANTS: Four subjects reporting discomfort produced by luminance (glare, halos, starbursts, or a combination thereof) in one eye after laser in situ keratomileusis (LASIK) were enrolled. The contralateral myopic eye (control) had no visual impairment and had undergone LASIK without complications or had not had previous surgery. METHODS: Functional magnetic resonance imaging was performed during photic stimulation, delivered by an optical fiber, of the affected and unaffected eyes. RESULTS: Functional magnetic resonance imaging provided evidence that most subjective visual symptoms correlated with anatomic flap abnormalities are associated with a higher signal increase in the visual association cortices compared with a nonsymptomatic eye. CONCLUSIONS: Functional magnetic resonance imaging of the visual cortex may help in exploring the mechanisms involved in glare effects after refractive surgery.

Ocular involvement in a case of systemic indeterminate cell histiocytosis: a case report.

PURPOSE: To describe ocular involvement in a case of systemic indeterminate cell histiocytosis, a rare disease characterized by the proliferation of indistinct histiocytes. These histiocytes resemble Langerhans cells but lack Birbeck granules. The disease usually occurs in adults, with no predisposition for either sex. The clinical features include multiple asymptomatic nodules and cutaneous papules. There are no previous reported cases in the literature regarding ocular indeterminate cell histiocytosis and its treatment. METHODS: A patient with skin papules and hyperpigmentation associated with systemic involvement and corneal infiltration was diagnosed with systemic indeterminate cell histiocytosis after a skin biopsy. Immunohistochemical examination showed specific surface proteins of indeterminate cells, and electron microscopy showed Langerhans-like cells without typical Birbeck granules. Progressive and severe photophobia and corneal thickening made bilateral corneal transplant necessary. RESULTS: Visual acuity remained stable because of the use of systemic immunosuppressors, which decrease the recurrence of infiltration after a corneal transplant. CONCLUSION: Indeterminate cell histiocytosis is a rare disease and there is no previous description of ocular involvement. Infiltrating lesions must be treated with corneal transplant and systemic cyclosporin if they decrease visual acuity.

[Screening of myopic LASIK patients with increased epithelial wound healing]. / Screening von myopen LASIK-Patienten mit einer gesteigerten epithelialen Wundheilung. Quantitative Bestimmung von EGF mRNA in den kornealen Epithelzellen.

BACKGROUND: Wound healing of the cornea is critical for the refractive outcome of myopic laser-assisted in situ keratomileusis (LASIK). As epidermal growth factor (EGF) is important for the origin of epithelial hyperplasia, this study examined preoperative EGF mRNA concentrations in the corneal epithelial cells to detect patients with increased epithelial wound healing response. PATIENTS AND METHODS: The epithelium was biopsied before LASIK in 35 eyes with myopia of -10.0 D. The EGF mRNA concentration in the epithelial cells was quantified by polymerase chain reaction and enzyme-linked oligosorbent assay, and the correlation with postoperative refraction at 6 months was assessed. RESULTS: All eyes were around emmetropia 3 weeks after the surgery. At 6 months postoperatively 27 eyes were within +/- 1.0 D of emmetropia while 8 showed regression of 2.0-4.0 D. Higher EGF mRNA levels were found in eyes with regression than in eyes with postoperative emmetropia. CONCLUSIONS: Preoperative EGF mRNA concentration in the corneal epithelial cells may be an indicator of postoperative refractive outcome of myopic LASIK and offers a new possibility for pharmaceutical manipulation.

Adjustable refractive surgery: 6-mm Artisan lens plus laser in situ keratomileusis for the correction of high myopia.

PURPOSE: To evaluate efficacy, predictability, stability and safety of adjustable refractive surgery (ARS) by combining a phakic intraocular lens (IOL) (Artisan lens 6-mm optical zone [OZ]) and laser in situ keratomileusis (LASIK) (6.5 mm OZ) for the correction of myopia greater than -15.00 diopters (D). DESIGN: Noncomparative interventional case series. PARTICIPANTS: Twenty-six eyes of 18 patients with a preoperative spherical equivalent between -16.00 and -23.00 D. METHODS: First surgery: An 8.5/9.5-mm flap was created and a 6-mm optic iris claw phakic IOL of -15.00 D was inserted in the anterior chamber through a posterior corneal incision. The second surgery was performed once refraction and topography were stable, between 3 and 5 months later. Second surgery: LASIK enhancement (6.5-9.2 OZ); the flap was relifted, and the residual refractive error was corrected. MAIN OUTCOME MEASURES: The main parameters in this study were uncorrected visual acuity, best-corrected visual acuity (BCVA), refraction, contrast sensitivity, endothelial cell count (ECC), and subjective response. RESULTS: Twenty-eight months after both surgeries, 80.70% of the eyes were within 0.50 D of emmetropia and 100% within 1.0 D. Twenty-six percent of the eyes gained 3 or more lines from their preoperative BCVA, and 42% gained 2 or more lines. There was no visual loss in any eye from 6 weeks to 24 months after LASIK enhancement (second surgery) and refraction, and visual acuities remained stable. Two subjects (11%) had some subjective disturbances at night. There was a 0.61% mean loss of ECC during the first 12 months and a 0.60% loss during the next 16 months. No serious complications were observed. CONCLUSIONS: ARS with the combination of a 6-mm optic, 15 D Artisan lens, and LASIK appears to be a safe and highly predictable method for the correction of myopia greater than -15.00 D. It is the best approach with the technology currently available.

Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis.

PURPOSE: To evaluate the efficacy, predictability, and stability of a combined procedure, arcuate keratotomy and laser in situ keratomileusis (LASIK), for the correction of high astigmatism. SETTING: Instituto de Microcirugía Ocular (IMO), Barcelona, Spain. METHODS: Fifteen eyes of 11 patients with naturally occurring astigmatism (NOA) (86. 66%) or surgically induced astigmatism (SIA) (13.34%) between -3.00 and -8.00 diopters (D) who had astigmatic keratotomy were studied. The patients had a secondary procedure, LASIK, to correct the residual refractive error. RESULTS: Mean baseline spherical equivalent refraction was -2.47 D +/- 3.69 (SD) and mean refractive cylinder, -4.59 +/- 1.66 D. Twelve months after LASIK, mean spherical equivalent was -0.09 +/- 1.50 D and the mean refractive cylinder, -1. 21 +/- 1.07 D. The mean cylindrical correction attempted in the NOA group was -4.05 +/- 1.19 D and in the SIA group, -7.00 +/- 1.41 D. Postoperatively, the values were -1.50 +/- 1.17 D and -1.62 +/- 0.17 D, respectively. Twelve months after LASIK, the uncorrected visual acuity (UCVA) was 0.5 +/- 0.1. The UCVA in the NOA group (0.50 +/- 0. 08) was better than in the SIA group (0.32 +/- 0.10). The efficacy index was 0.96 overall. Best corrected visual acuity deteriorated by 1 Snellen line in 1 case (6.6%) but improved by 1 and 2 Snellen lines in 4 cases (26.6%) and 2 cases (13.3%), respectively. All procedures were completed without adverse reactions intraoperatively or postoperatively. CONCLUSION: This combined technique was effective in the treatment of high astigmatism, with excellent results compared with the results of each procedure alone. Because of its high predictability, we strongly recommend the technique in cases with astigmatism higher than 3.0 D, particularly in those with astigmatism higher than 5.0 D.

Limbal-conjunctival autograft transplantation for the treatment of recurrent pterygium.

OBJECTIVE: Different investigators have recently emphasized the importance of the limbus and its stem cells in the pathogenesis of the pterygium. In this article we examine the usefulness of limbal-conjunctival autograft transplantation for the treatment of advanced recurrent pterygium. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Seven patients with advanced recurrent pterygium. All had previously been treated a minimum of two times by simple excision (two of them with intraoperative mitomycin C). INTERVENTION: Limbal-conjunctival autograft transplantation after pterygium excision was performed in all cases. MAIN OUTCOME MEASURES: Pterygium recurrences and complications with a minimal follow-up period of 14 months. RESULTS: There were no recurrences of pterygial growth beyond the limbal edge. In addition, no significant complications were noted. Only one case of limited pseudopterygium in the donor site and one case of graft retraction were recorded. No further surgical interventions were needed in any case. CONCLUSIONS: Limbal-conjunctival autograft transplantation is a promising technique for the treatment of advanced recurrent pterygium.

Combined surgery to correct high myopia: iris claw phakic intraocular lens and laser in situ keratomileusis.

PURPOSE: To evaluate the results of combined surgery, implantation of an Artisan phakic iris claw intraocular lens (IOL) followed by laser in situ keratomileusis (LASIK) to correct high myopia. METHODS: A prospective study of 6 patients (8 eyes) with high myopia who had Artisan phakic IOL implantation followed by LASIK was undertaken. The IOL was a standard -15.00-D, 6-mm diameter optical zone. Residual refractive error was corrected by LASIK. Mean follow-up was 16 +/- 4 months (range, 12 to 20 mo). RESULTS: After the second procedure (LASIK), uncorrected visual acuity ranged from 0.4 to 0.63 (mean, 0.5 +/- 0.07) at 1 month and from 0.6 to 0.7 (mean, 0.62 +/- 0.04) at 12 months. Spectacle-corrected visual acuity improved 2 or more lines in 62.5% (5 eyes) from preoperative values. Mean postoperative spherical equivalent refraction was -0.68 +/- 0.23 at 1 month and -0.35 +/- 0.22 at 12 months after LASIK. All eyes were within +/-1.00 D of emmetropia following the LASIK portion of the two-stage procedure and 5 eyes were within +/-0.50 D. We had no major complications. No significant endothelial damage occurred. CONCLUSIONS: The accurate refractive outcome, absence of major complications, stability of results, and most important, improvement in quality of vision (defined as no change in vision when illumination conditions varied, eg, at night) experienced by these highly myopic patients are reasons to continue using and improving this combined technique.

LASIK for the correction of residual refractive errors from previous surgical procedures.

BACKGROUND AND OBJECTIVE: To evaluate laser assisted in situ keratomileusis (LASIK) efficacy in correcting residual refractive errors after corneal or intraocular surgery (penetrating keratoplasty, radial keratotomy, photorefractive keratectomy, phacoemulsification with intraocular lens (IOL) implantation, penetrating ocular trauma and phakic IOL implantation). MATERIAL AND METHODS: We performed LASIK in 87 eyes of 62 patients previously operated by means of other surgical techniques to completely correct the residual refractive error. We report the mean refractive error (in terms of spherical equivalent refraction), uncorrected visual acuity (UCVA) and spectacle corrected visual acuity (SCVA) before and after the surgical procedure. We also analyze safety and stability, in these results with a minimum of 12 months follow-up. RESULTS: Mean preoperative spherical equivalent was -5.25 +/- 2.1 diopters (D). Postoperatively, mean spherical equivalent was -0.70 +/- 0.65 D, 76% of eyes were between plano and -1.00 D and 99% were between plano and -2.25 D. At 12 months follow-up the change in the refractive result was equal or less than 0.5 D in 94% of eyes. Preoperatively SCVA was 1.0 or better in 24.13% of cases, and 0.5 or better in 89.65%. Postoperative SCVA was 1.0 or better in 26.43% and 0.5 or better in 95%. Preoperative UCVA was 0.1 in 2 eyes, 0.05 in 4 eyes and count fingers in the rest of the cases. Postoperative UCVA was 1.0 or better in 1.1% and 0.5 or better in 70.1%. We had an extremely low complication rate in this particular group of patients. CONCLUSIONS: LASIK can be successfully used to correct residual refractive errors after other surgical procedures.

Intraepithelial photorefractive keratectomy for regression after laser in situ keratomileusis.

PURPOSE: To propose a refractive procedure, intraepithelial photorefractive keratectomy (IE-PRK), to treat regression after laser in situ keratomileusis (LASIK). SETTING: IMO Instituto de Microcirugîa Ocular de Barcelona, Cornea and Refractive Surgery Unit, Autonoma University of Barcelona, Barcelona, Spain; Vall d'Hebron Hospital, Department of Ophthalmology, INSERM, University Hospital, Toulouse, France. METHODS: This open but uncontrolled prospective pilot study assessed the efficacy, predictability, and stability of IE-PRK in 21 eyes of 21 patients who had previous LASIK for myopia or myopic astigmatism with a mean spherical equivalent (SE) refraction of -9.80 diopters +/- 2.95 (SD). After LASIK, the eyes regressed to a mean of -1.93 +/- 0.82 D. They were retreated with IE-PRK, in which a photoablation was performed directly in the epithelium without damage to Bowman's membrane. Follow-up was up to 1 year. RESULTS: Eight of the 21 eyes (38%) were emmetropic at 6 months and 11 (52.4%) had a refraction between -0.50 and +0.50 D. Refraction was stable from the second week to the first year, with no significant differences among the mean SEs at 10 days, 6 weeks, and 6 and 12 months. CONCLUSION: The preliminary results of this small series indicate that IE-PRK appears to be safe, especially in selected cases; 1 line of lost best spectacle-corrected visual acuity occurred in 5% of eyes.

Application of the amniotic membrane in ocular surface pathology.

The amnion is a fine semi-transparent membrane that has been used in clinical practice to encourage epithelization in burns, in skin ulcers, or as a skin graft. Application in ocular surface disorders first took place in 1940. We carried out the membrane amniotic implantation on 11 patients with different pathologies: three cases of limbal stem cell deficiency (caustication with failure of prior keratoplasty, congenital aniridia and post-radiotherapy keratopathy), one case with persistent neurotrophic corneal ulcer after prior keratoplasty, four cases with epithelial defect of long evolution, one case of extensive Salzmann's degeneration of the cornea, and two cases after the resection of conjunctival tumour. The follow-up period varied between 2 and 6.5 months (mean = 4 months). Amniotic membrane was obtained by elective Caesarean, and it was preserved at -80 degrees C. In all transplanted patients the reabsorption of the amniotic membrane took place between the third and the fifth week. In the cases of resection of conjunctival tumour the epithelialization was completed between the first and the second post-operative week, with minimal residual scarring. In the other cases, with affliction of the corneal epithelium, the complete epithelialization, together with a marked reduction in the inflammatory response, occurred in all except 2 cases. In conclusion, the implantation of preserved human amniotic membrane can favour the recovery of a normal ocular surface in different pathologies, both in corneal and conjunctival lesions.

Regression after LASIK for the treatment of myopia: the role of the corneal epithelium.

Factors responsible for postoperative regression are still unknown but postoperative epithelial hyperplasia might play an important role. To evaluate the role of the corneal epithelium on regression after laser in situ keratomileusis (LASIK), the thickness of the epithelium was measured in 18 eyes preoperatively and at various postoperative intervals. Measurements of the epithelial thickness were taken using a high-frequency (50 MHz) ultrasound device and measurements were correlated with the postoperative refraction. In all eyes, preoperative epithelial thickness was between 34 and 44 microm. In contrast, after surgery, values were between 35 and 111 microm. In eyes with a refractive outcome of +/-1.0 diopter of that intended, there was an increase of the epithelial thickness of less than 5 microm postoperatively. In contrast, eyes with severe regression showed a significant increase in the thickness in the epithelium after LASIK. In our patient group, regression of the attempted correction was related to postoperative epithelial hyperplasia. Broadly speaking, an increase of 10 microm epithelial thickness resulted in a 1 diopter regression. Mechanical and/or pharmaceutical factors controlling postoperative epithelial hyperplasia would be beneficial.

Clear lens extraction to correct high myopia.

PURPOSE: To assess the refractive outcome and postoperative complications in a single surgeon series of clear lens extraction for high myopia. SETTING: Ophthalmology Department, Cornea and Refractive Surgery Unit, Vall d'Hebrón Hospital, Autónoma University of Barcelona, Spain. METHODS: Forty-six clear lens extraction procedures performed in 37 patients from November 1992 to January 1994 by one surgeon were retrospectively analyzed. Capsule tear and vitreous loss, endothelial cell loss, preoperative and postoperative best corrected visual acuity and cycloplegic refraction, and retinal detachment occurrence were looked at. RESULTS: Capsule tear with vitreous loss occurred in one eye (2.17%). Mean endothelial cell loss was 2.6% during the first postoperative year. Best corrected visual acuity was 6/12 or better in 69.4% of eyes preoperatively and in 88.5% postoperatively. Mean cycloplegic refraction was -16.05 diopters (D) preoperatively; the residual cycloplegic refraction was within 1.00 D in 48.4% of eyes and within 2.00 D in 92.5% postoperatively. CONCLUSION: Because of its high predictability, stability, and low morbidity, we believe clear lens extraction is a reasonable refractive surgery option for middle-aged patients with myopia.

Transverse keratotomy to correct high corneal astigmatism after cataract surgery.

PURPOSE: To assess the outcome of transverse keratotomy to correct high corneal astigmatism after cataract surgery. SETTING: Vall d'Hebron Hospital, Department of Ophthalmology, Cornea and Refractive Surgery Unit, Barcelona Autónoma University, Spain. METHODS: Thirty-two eyes with regular corneal astigmatism between 2.50 and 5.00 diopters (D) after previous cataract surgery had two transverse incisions with an optical zone of 5.0 or 7.0 mm, a depth of 80 or 90%, and a length of 3.0 or 4.0 mm, depending on the amount of astigmatism and based on a personal nomogram we developed. RESULTS: From 80 to 100% of the desired correction was achieved in 38.7% of eyes and from 60 to 80% in 38.9%. At 6 months, only 9.1% had a keratometric change of more than 0.50 D. Best corrected visual acuity was the same or better in 85.2% of patients; no patient lost more than one Snellen line. CONCLUSION: This easy, safe technique had low anatomical and refractive morbidity and high efficacy, making it an excellent option for eyes with high astigmatism after cataract surgery. More research is required in view of the considerable unpredictability of our results and the disparity in methods and results of other published studies.