María A. del Buey

Evaluation of in vitro efficacy of combined riboflavin and ultraviolet a for Acanthamoeba isolates.

PURPOSE To evaluate in vitro the amoebicidal effects of riboflavin and ultraviolet A (UVA) collagen cross-linking. DESIGN Experimental study, laboratory investigation. METHODS Two different strains of Acanthamoeba species were tested identically. Four treatment groups were considered: group 1 consisted of 0.1% riboflavin and 30-minute UVA irradiation; group 2 consisted of 0.1% riboflavin and 60-minute UVA irradiation; group 3 consisted of no riboflavin and no UVA exposure; group 4 consisted of 0.1% riboflavin and no UVA exposure. The application of UVA was performed under the parameters used for in vivo corneal collagen cross-linking. RESULTS In all cases, cysts and trophozoites were detected 24 hours after treatment at a radial distance from the center of the seeding point more than 5 mm, indicating that the amoebae were viable. All treated and untreated groups of amoebae from the 2 strains exhibited growth (radii of 14 to 15 mm in groups 1, 3, and 4; radius of 12 mm in group 2). The final morphologic features of the 2 strains of trophozoites that received treatment were similar to those of the initial seeding group and the untreated control group. CONCLUSIONS The results obtained in our study show that a single dose (30 or 60 minutes) of cross-linking cannot achieve eradication in the 2 different Acanthamoeba strains examined. However, in vitro results do not always indicate in vivo efficacy, so future studies should test the validity of this treatment for Acanthamoeba keratitis.

Assessment of Corneal Biomechanical Properties and Intraocular Pressure in Myopic Spanish Healthy Population

Purpose. To examine biomechanical parameters of the cornea in myopic eyes and their relationship with the degree of myopia in a western healthy population. Methods. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOP), and corneal compensated IOP (IOPcc) were measured using the ocular response analyzer (ORA) in 312 eyes of 177 Spanish subjects aged between 20 and 56 years. Refraction was expressed as spherical equivalent (SE), which ranged from 0 to −16.50 diopters (D) (mean: −3.88 ± 2.90 D). Subjects were divided into four groups according to their refractive status: group 1 or control group: emmetropia (−0.50 ≤ SE < 0.50); group 2: low myopia (−0.75 ≤ SE < 3.00 D); group 3: moderate myopia (−3.00 ≤ SE ≤ −6.00 D); and group 3: high myopia (SE greater than −6.00 D). We analyzed the relationship between corneal biomechanics measured with ORA and SE. Results. CH in the emmetropia, low myopia, moderate myopia, and high myopia groups was 11.13 ± 0.98, 11.49 ± 1.25, 10.52 ± 1.54, and 10.35 ± 1.33 mmHg, respectively. CH in the highly myopic group was significantly lower than that in the emmetropic group (P = 0.07) and low myopic group (P = 0.035); however, there were no differences with the moderate myopic group (P = 0.872). There were no statistically significant differences regarding IOP among the four groups (P > 0.05); nevertheless, IOPcc was significantly higher in the moderately myopic (15.47 ± 2.47 mmHg) and highly myopic (16.14 ± 2.59 mmHg) groups than in the emmetropia (15.15 ± 2.06 mmHg) and low myopia groups (14.53 ± 2.37 mmHg). No correlation between age and the measured parameters was found. CH and IOPcc were weakly but significantly correlated with SE (r = 0.171, P = 0.002 and r = −0.131, P = 0.021, resp.). Conclusions. Present study showed only a very weak, but significant, correlation between CH and refractive error, with CH being lower in both moderately and highly myopic eyes than that in the emmetropic and low myopic eyes. These changes in biomechanical properties of the cornea may have an impact on IOP measurement, increasing the risk of glaucoma.

Multifocal intraocular lenses for unilateral cataract in children

PURPOSE: To evaluate the implantation of apodized diffractive multifocal intraocular lenses (IOLs) in children with unilateral cataract. SETTING: Ophthalmology Service, Hospital Clínico Lozano Blesa, Zaragoza, Spain. DESIGN: Prospective clinical study. METHODS: Five children between 4 and 6 years of age with unilateral cataract had cataract extraction and implantation of an apodized diffractive multifocal IOL (AcrySof Restor SN60D3). Phacoaspiration was accompanied by posterior capsulorhexis followed by an anterior vitrectomy. Uncorrected distance (UDVA), corrected distance (CDVA), and corrected near (CNVA) visual acuities; binocular function using the Worth 4‐dot test and the TNO stereotest; and subjective symptoms such as glare and halos were evaluated over 21 months of follow‐up. RESULTS: At the final follow‐up visit, the mean UDVA was 0.45 ± 0.149 logMAR and the mean CDVA was 0.30 ± 0.06 logMAR with 20/32 in 3 eyes, 20/50 in 1 eye, and 20/63 in 1 eye. The mean CNVA was 0.10 ± 0.05 logMAR (about 20/25) with J1 in 2 eyes, J2 in 1 eye, J3 in 1 eye, and J4 in 1 eye. The stereoacuity was 120 seconds of arc (arcsec) in 2 patients, 240 arcsec in 1 patient, 1980 arcsec in 1 patient, and nonexistent in 1 patient. The Worth 4‐dot test showed that 4 patients had fusion. None of the 5 patients complained about halos or glare. No IOL decentration was observed in any patient. CONCLUSION: Implantation of an apodized multifocal IOL seems to be a satisfactory alternative to monofocal pseudophakia in children with unilateral cataract. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

An unusual case of cocaine-induced maculopathy.

Purpose Cocaine is one of the most common substances of abuse. When used intranasally, cocaine is cut with a variety of agents, which may increase local and systemic toxic reactions. Methods We examined a 34-year-old man who complained of color disturbance. The patient reported a 10-year history of daily intranasal cocaine use, but denied use during the last year. Color vision testing showed a dysregulation of blue–yellow color vision. Electroretinogram revealed significantly reduced blue cone responses. Dilated fundus examination of both eyes revealed a bilateral maculopathy. Fluorescein angiography disclosed an early hyperfluorescence in both foveal areas which maintained in late phase. Optical coherence tomography was normal in both eyes. The patient was diagnosed with an unusual maculopathy related to a long-term intranasal cocaine use. Results All 6 eyes exhibited pigmentary changes located along the border of the staphyloma, and also radially to it, giving a particular T-shaped pattern of pigmentary changes. These changes were visible as either a linear strip or a triangular or oval-shaped area. Three eyes had a documented history of subretinal leakage that mimicked central serous chorioretinopathy, a well-known complication of tilted disk syndrome. Conclusions Ocular complications from topical cocaine abuse are rare. Impaired color vision, as in our patient, has been reported in cocaine-withdrawn patients. To our knowledge, this is the first described case of a bilateral and symmetric maculopathy associated with long-term intranasal cocaine use. To avoid a delay of treatment, ophthalmologists should be aware that a maculopathy with small defects in color vision may be related to adulterants added to cocaine when it is used intranasally. (Eur J Ophthalmol 2009; 19: 880–2)

The Effect of Intraocular Pressure on the Outcome of Myopic Photorefractive Keratectomy: A Numerical Approach

Photorefractive Keratectomy (PRK) is a surgical procedure widely performed to correct myopia. In this work, the effect of the intraocular pressure (IOP) on the refractive correction achieved by the PRK surgery was analyzed using a numerical model. Simulations of PRK surgery at 10, 15 and 21 mmHg of IOP were performed and the post-surgical diopters were estimated. For low and medium values of IOP (10 and 15 mmHg), the computed results were close to those used by clinicians based on experience and defined without considering the IOP, while an undercorrection was predicted for the highest value of IOP (21 mmHg). From these results, we suggest that IOP should be considered in the determination of the depth of ablation, in addition to other factors such as the level of myopia or the corneal central thickness.

Computational Simulation of Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment: On the Effect of the Band Size on the Myopization

A finite element model (FE) of the eye including cornea, sclera, crystalline lens, and ciliary body was created to analyze the influence of the silicone encircling bandwidth and the tightness degree on the myopia induced by scleral buckling (SB) procedure for rhegmatogenous retinal detachment. Intraocular pressure (IOP) was applied to the reference geometry of the FE model and then SB surgery was simulated with encircling bandwidths of 1, 2, and 2.5 mm. Different levels of tightening and three values of IOP were applied. The anterior segment resulted as unaffected by the surgery. The highest value of Cauchy stress appeared in the surroundings of the implant, whereas no increment of stress was observed either in anterior segment or in the optic nerve head. The initial IOP did not appear to play any role in the induced myopia. The wider the band, the greater the induced myopia: 0.44, 0.88, and 1.07 diopters (D) for the 1, 2, and 2.5 mm bandwidth, respectively. Therefore, patients become more myopic with a wider encircling element. The proposed simulations allow determining the effect of the bandwidth or the tightness degree on the axial lengthening, thus predicting the myopic increment caused by the encircling surgery.

Immediate Effect of Ultraviolet-A Collagen Cross-linking Therapy on the Biomechanics and Histology of the Human Cornea

Wollensak et al. introduced corneal collagen crosslinking (CXL) using riboflavin and ultraviolet-A for the treatment of progressive keratoconus.1 Empirical in vitro studies evaluated the stiffening effect of CXL and some used human corneas to assess the stiffness achieved,2,3 but they did not present a histological analysis of the treated human cornea. To learn the immediate mechanical and histological effect induced by CXL in human corneal tissue, we performed tensile stress tests and histological comparative observation of cross-linked and untreated healthy human corneas. The corneas were retrieved from the local tissue bank. They were clear with normal epithelium, endothelium, and corneal thickness. One sample received a standard epithelium–off-riboflavin/ ultraviolet-A CXL treatment and the other was only deepithelialized. The stress-strain test showed a stiffer response of the treated tissue than that of the untreated tissue. The treated cornea resulted in 1.8, 1.6, 1.7, and 1.5 folds stiffer than the untreated sample at the 6%, 8%, 10%, and 12% stretches, respectively. Stiffness of the tissue after treatment was increased by 64% (factor of 1.64). Although Wollensak et al.2 initially found a 350% increase of stiffness in the treated tissue (greater than that of the current study), this value was later corrected and an increase in stiffness by a factor of 1.5 was given by Spoerl in the 7th Cross-linking Congress. The study by Raiskup and Spoerl4 gave a value of 70% increase (factor of 1.7), which matches our result. Besides increasing the biomechanical rigidity of the human cornea, CXL induces secondary effects such as keratocyte apoptosis.1 Therefore, the safety of the procedure must be guaranteed. The cytotoxicity of the riboflavin/ ultraviolet-A treatment on keratocytes and endothelium cells was studied by Wollensak et al.,2 who established a cytotoxic threshold of 5.4 J/cm2. However, the significance of the damage is not yet completely known and, to our knowledge, it has not been reported in in vivo studies with human corneas in the literature. Our histological analysis of the treated sample showed an immediate effect of the outermost stroma compacting with increased fibrillar density and decreased interlamellar space in comparison with the control. Dehydration reached approximately 65% of the thickness. Regarding the cellular population, the treated sample showed absence of keratocyte nuclei in the stroma even at a deep level, whereas the control sample showed intact keratocyte nuclei (Figure 1). Therefore, keratocyte apoptosis happens immediately after treatment in the cross-linked cornea and at a deeper level than expected, possibly due to immediately performing the histological analysis. Wollensak5 observed keratocytes in the posterior stroma 24 hours after CXL. We suppose keratocytes could have repopulated the deeper cornea during these hours. According to our results, CXL has an immediate biomechanical and histological effect. Stiffening of the tissue, stromal compacting, and a keratocyte apoptosis deeper than compacting were observed.

Keratitis Due to Achromobacter xylosoxidans in a Contact Lens User.

Objectives: Ocular infections due to Achromobacter xylosoxidans are extremely uncommon; their diagnosis is a challenge and the optimal treatment remains controversial. We present a case of A. xylosoxidans in a contact lens user and a review of the literature to facilitate diagnostic suspicion and empirical therapeutic management. Methods: Review of the literature in PubMed and MEDLINE. We also document a case diagnosed in our department in January 2016. Setting: Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain. Results: According to the literature, clinical manifestations and antibiotic sensitivity of A. xylosoxidans varied greatly. Our patient with no history of keratopathy presented three risk factors that made the diagnosis suspicious. The infection was resolved with topical moxifloxacin and fluorometholone. Conclusions: A. xylosoxidans is an uncommon cause of infection, but must be suspected in atypical keratitis, reported contact with warm or still waters, use of contact lenses, or previous corneal damage. In these cases, microbiological studies and antibiotic sensitivity testing are particularly important.

Two cases of accidental dislocation of the silicone sleeve of an extrusion cannula into the vitreous cavity.

Background: Fluid-air exchange during vitreoretinal surgery is often used as a tool for subretinal fluid endodrainage. Soft-tipped flexible extrusion cannulas are commonly used to aspirate the posterior subretinal fluid. Methods: This is an observational two-case series describing two patients who underwent 20-G pars plana vitrectomy complicated by the accidental fall of the silicone sleeve of a soft-tipped extrusion cannula into the vitreous cavity. In the first case, the cannula had inadvertently been subjected to sterilization process. Results: While withdrawing the soft-tipped extrusion cannula from the eye, following internal drainage of transvitreal and subretinal fluid, the loose silicone sleeve probably got entangled at the inner lip of the sclerotomy and finally fell on the retinal surface. In both cases, the silicone sleeve was held and removed with an intraocular forceps. Conclusions: This rare complication has been reported in the literature only once previously. Sterilization of disposable subretinal fluid cannulas is not advisable because of the risk of dislocation of the silicone sleeve into the eye. Besides this, it is important to check the integrity of the silicone sleeve before and after surgery.

Fundus autofluorescence: the key in the diagnosis of maternally inherited diabetes and deafness

We report an interesting case of maternally inherited diabetes and deafness (MIDD), in which fundus autofluorescence aided in the diagnosis. MIDD is a rare genetic disorder, maternally transmitted, characterised by a point mutation of the mitochondrial DNA (mtDNA) at position 3243 that disrupts the mitochondrial respiratory chain and thus, affects metabolically active organs such as pancreatic islets, cochlea or retina. It has an average age onset of 34–40 years and accounts for 0.5 to 2.8 per cent of all cases of diabetes. In more than 80 per cent of cases, it is associated with bilateral macular pattern dystrophy.