Cataract Surgery with a Refractive Corneal Inlay in Place.

Purpose. To present a case of cataract surgery performed in a patient with a refractive corneal inlay in place. Methods. A 48-year-old female patient presented to our institute with bilateral cataract. The patient had undergone refractive corneal inlay implantation three years ago in her right, nondominant eye for presbyopia correction. Biometry and intraocular lens (IOL) power calculation were performed without removing the inlay. Phacoemulsification and IOL insertion were carried out in both eyes in a usual manner. Results. On day one postoperatively, the patient achieved binocular uncorrected distance visual acuity 20/20 and uncorrected near visual acuity J1. The vision remained stable during the one-year follow-up period. Conclusion. Cataract surgery was performed in a standard manner in a patient with Presbia Microlens corneal inlay in place. Visual outcomes for both near and distance vision were satisfactory.

Efficacy of two silicone-hydrogel contact lenses for bandage use after photorefractive keratectomy.

PURPOSE: To evaluate the efficacy of two silicone hydrogel (SiH) contact lenses, approved for continuous wear for one week, following photorefractive keratectomy (PRK). METHODS: Forty seven myopic patients (94 eyes) undergone bilateral PRK were enrolled in this prospective, double-masked, comparative study. One eye of each patient was fitted with a Lotrafilcon B lens (Ciba Vision, Duluth, US; 30-day recommended replacement) whereas the fellow eye was fitted with an Asmofilcon A lens (Menicon, Nagoya, Japan; 14-day recommended replacement). Epithelial defect size was assessed using slit lamp biomicroscopy on the day of surgery and at days 1-4 post-operatively. Uncorrected and best-corrected visual acuity and retinal straylight (C-Quant, Oculus Optigerate, Germany) were evaluated pre-operatively and one month post-operatively. RESULTS: Average epithelial defect size for Asmofilcon A and Lotrafilcon B was 25.5±11.0mm(2) vs. 27.1±9.9mm(2) at day 1 (p=0.007) and 6.3±7.0mm(2) vs. 9.2±9.5mm(2) at day 2 (p=0.012) post-operatively. Re-epithelialization at day 3 was completed in 87.2% of the eyes fitted with Asmofilcon A lenses, compared to 74.5% with Lotrafilcon B lenses (p=0.012). At the 3rd post-operative day 29.8% of re-epithelialized eyes showed irregular suture with Lotrafilcon B, compared to 12.8% eyes with Asmofilcon A lenses (p<0.001). Finally, no statistically significant differences were found post-operatively between the two lenses retinal straylight (p=0.98) and best-corrected visual acuity (p=0.68). CONCLUSIONS: SiH lenses can be used as an effective bandage after PRK due to the limited time requested for achieving complete corneal re-epithelialization. Faster and smoother epithelial healing is provided with Asmofilcon A over Lotrafilcon B lenses.

Threat and anxiety affect visual contrast perception.

Threat cues activate the visual cortex and are detected faster than neutral cues as evidenced by functional brain imaging during viewing of visual threat and neutral stimuli. The functional visual processes underlying these phenomena have not been determined. Pattern visual evoked potentials were elicited in a baseline and a verbal threat condition with two stimulus contrasts in subjects with high and low trait anxiety. Threat reduced the latency of the early P100 wave in the low but not the high anxious group. The reduction was greater with increasing stimulus contrasts. The dependence of the P100 latency on trait anxiety is reminiscent of the Yerkes-Dodson inverted U-shape curve, which relates anxiety to behavioural responses. These results show that threat affects perceptual processes and suggest that data based on the effects of threat in visual search studies should be reappraised to include acceleration of contrast perception.

Endophthalmitis after cataract extraction: incidence, treatment, and outcome in Crete, Greece, during period 2000-2008.

PURPOSE: To report the incidence, microbial spectrum, and outcome of cataract operation related endophthalmitis cases from 2000 to 2008 in the Department of Ophthalmology, University Hospital of Heraklion, Crete. METHODS: Retrospective, observational case series collected from the files of the University Eye Clinic of Heraklion. RESULTS: From 2000 to 2008, 23 eyes of 23 patients with endophthalmitis after cataract surgery were reported. Vitreous specimens were obtained in all cases. Twelve were cultured positive, 8 with gram-positive bacteria, and 4 with gram-negative bacteria. Ten patients were treated medically, 13 surgically, and 2 finally underwent enucleation of the affected globe. Fourteen (60.8%) eyes of the total 23 managed in our hospital, achieved a final visual acuity of 1/10 or better and 9 lower than 1/10. Five eyes ended up with no light perception. CONCLUSIONS: We provide an overview of cataract operation related endophthalmitis cases managed in our clinic during the past 9 years.

Comparison of the ocular wavefront aberration between pharmacologically-induced and stimulus-driven accommodation.

PURPOSE: To compare the ocular wavefront aberration between pharmacologically- and stimulus-driven accommodation in phakic eyes of young subjects. METHODS: The aberration structure of the tested eye when accommodating was measured using the Complete Ophthalmic Analysis System (COAS; AMO WaveFront Sciences, Albuquerque, NM, USA). It was used in conjunction with a purposely-modified Badal optometer to allow blur-driven accommodation to be stimulated by a high contrast letter E with a vergence range between +0.84 D and -8.00 D. Pharmacological accommodation was induced with one drop of pilocarpine 4%. Data from six subjects (age range: 23-36 years) with dark irides were collected. RESULTS: No correlation was found between the maximal levels of accommodative response achieved with an 8 D blur-driven stimulus and pharmacological stimulation. Pharmacological accommodation varied considerably among subjects: maximum accommodation, achieved within 38-85 min following application of pilocarpine, ranged from 2.7 D to 10.0 D. Furthermore, although the changes of spherical aberration and coma as a function of accommodation were indistinguishable between the two methods for low levels of response, a characteristic break in the pattern of aberration occurred at higher levels of pilocarpine-induced accommodation. This probably resulted from differences in the time course of biometric changes occurring with the two methods. CONCLUSION: Measuring the pilocarpine-induced accommodative response at only one time point after its application may lead to misleading results. The considerable inter-individual differences in the time course of drug-induced accommodative response and its magnitude may lead to overestimation or underestimation of the corresponding amplitude of normal, blur-driven accommodation. Stimulating accommodation by topical application of pilocarpine is inappropriate for evaluating the efficacy of 'accommodating' IOLs.

Road traffic casualties: understanding the night-time death toll.

A disproportionate number of fatal injuries occur after dark. The paper presents some statistics of road traffic injuries in a novel way which suggests that low luminance plays a major role in this effect. A sound physiological explanation for this is advanced based on the poor temporal characteristics of rod photoreceptors. It is argued that processing information based on low luminance, low contrast targets is much slower than that for high contrast bright targets. To test the idea, simple visual reaction times were measured under typical low visibility conditions encountered on non-lit roads and were found to be substantially longer than under optimal conditions. It is shown that longer reaction times translate into significantly increased stopping distances. This important point has received insufficient attention in the road safety literature, by the Highways Agency, the police, injury prevention officials, and the UK Highway Code.

Observation of the posterior endothelial surface of the rabbit cornea using atomic force microscopy.

PURPOSE: To study the surface of normal corneal endothelium by means of atomic force microscopy (AFM). METHODS: The central corneal endothelial posterior surface of New Zealand white rabbits was examined. Specimens were observed in Balanced Salt Solution using the contact mode of the AFM either fresh or after fixation in cacodylate-buffered glutaraldehyde solution. Removal of sialic acid residues and hyaluronic acid was achieved by means of enzymatic treatment with neuraminidase and hyaluronidase. RESULTS: Observation of the fresh specimens revealed the presence of an apical endothelial surface coating material (glycocalyx). Removal of sialic acid residues and hyaluronic acid after enzymatic treatment using neuraminidase and hyaluronidase, respectively, permitted the elucidation of the structure of the nondigested coating material. Fixation of the samples resulted in removal of the surface coating material. The imaging of the fixed endothelium surface revealed the mosaic of polygonal cells with the apical flaps of cell junctions emerging over the cell surface. The cell shape and the other characteristics of the posterior surface fixed endothelium were comparable to those described in the literature using scanning electron microscopy. The scanning of very small ranges has provided high-resolution images at the nanometer level in fixed and fresh corneal endothelial surfaces. CONCLUSION: The atomic force microscope represents a new powerful imaging tool permitting high-resolution observation of corneal endothelium surface in fresh and minimally prepared fixed specimens.

Detection of herpes simplex virus in pseudoexfoliation syndrome and exfoliation glaucoma.

PURPOSE: The pathogenesis of pseudoexfoliation syndrome (PEX) remains unknown. An infection, possibly viral, is one of the proposed pathogenetic mechanisms. This study examines the presence of herpes simplex virus (HSV) and varicella-zoster virus (VZV) in iris and anterior capsule specimens of PEX and non-PEX patients. METHODS: Iris and anterior capsule specimens were obtained from 64 patients with PEX (study group, SG) and 61 patients without PEX (control group, CG). The presence of HSV and VZV DNA was evaluated with a polymerase chain reaction (PCR). RESULTS: Herpes simplex virus type I was detected significantly more often in iris specimens from the SG (13.79%), compared to those from the CG (1.75%). Varicella-zoster virus DNA was not detected in any of the examined specimens. CONCLUSION: Results imply a possible relationship between HSV type I and PEX, although no aetiological role of HSV infection in PEX pathogenesis can be established. Results also advocate against any association between VZV and PEX.

Hemorrhagic Descemet's membrane detachment as a complication of deep sclerectomy: a case report.

PURPOSE: To report a case that developed hemorrhagic Descemet's membrane detachment after deep sclerectomy. PATIENT AND METHODS: Case report. A 63-year-old diabetic patient suffering from uncontrolled chronic open-angle glaucoma with full medication, underwent an uneventful deep sclerectomy operation combined with intraoperative Mitomycin-C. RESULTS: On the second postoperative day, a hemorrhagic Descemet's membrane detachment (HDDM) was observed. The hemorrhage showed rapid absorption rate during the first two weeks along with reduction of the HDDM. After this period of time the rate of blood absorption was decreased. The Descemet's membrane reattached completely six months after surgery without any intervention but a paracentral corneal scar was present. The bleb was not functionally impaired during the whole postoperative period, and intraocular pressure remained stable at the level between 12 and 15 mmHg without medication. CONCLUSION: Hemorrhagic Descemet's membrane detachment should be considered as a potential complication of deep sclerectomy.

Corneal ectasia induced by laser in situ keratomileusis.

PURPOSE: To identify factors that can lead to corneal ectasia after laser in situ keratomileusis (LASIK). SETTING: University refractive surgery center. METHODS: In this retrospective study, the charts of all patients (2873 eyes) who had LASIK between May 1995 and November 1999 were reviewed. Fourteen patients (19 eyes, 0.66%) developed post-LASIK ectasia. The mean follow-up was 16.32 months (range 6 to 42 months). RESULTS: No patient with an attempted correction less than 8.00 diopters or a residual corneal bed thickness greater than 325 microm experienced post-LASIK ectasia. There was a statistically significant positive correlation between corneal residual bed thickness and increasing patient age. CONCLUSION: Despite the limitations of the small sample size, the study's results suggest that parameters besides residual corneal bed thickness (eg, age, attempted correction) may have to be considered to avoid post-LASIK ectasia.

Wavefront customized ablations with the WASCA Asclepion workstation.

PURPOSE: WASCA (Wavefront Aberration Supported Cornea Ablation) is a method for wavefront-guided ablation. This new method records all existing eye aberrations with the Asclepion Wavefront Aberrometer and calculates the customized pattern for laser correction. We measured the low and high order aberrations of eyes before and after PRK and LASIK, as well as before and after flap creation. METHODS: The Asclepion Shack-Hartmann aberrometer was used to measure wavefront aberrations. Preoperative and postoperative measurements were made following both PRK and LASIK performed with conventional software, modified Aberration-free Profile (AFA) software, and specially designed WASCA software. Surgery was performed with the Meditec MEL-70 G-scan excimer laser. Additionally, measurements were made before and after flap creation only (10 eyes). RESULTS: There was a significant difference between preoperative and 1-month postoperative high order aberrations, with notable increases following conventional PRK and LASIK and less increase following modified AFA PRK and LASIK. Flap creation only changed the higher order aberrations slightly, and caused a shift toward hyperopia. In the eyes that received WASCA correction with PRK or LASIK, at 3 months postoperative the high order aberrations averaged an increase of 1.3 times for PRK and 1.8 times for LASIK. Both the AFA and WASCA treatments demonstrated improved outcomes in comparison to conventional PRK and LASIK. CONCLUSION: Wavefront mapping of the eye and wavefront-guided ablation with the Asclepion Aberrometer can be used for optimizing the results and fine-tuning visual performance after laser vision correction. WASCA PRK appeared to result in better outcomes than WASCA LASIK.

Principles of ray tracing aberrometry.

PURPOSE: Of all transforms of an eye, aberrations are significant when higher visual acuity is to be achieved. Ray tracing aberrometry developed by the Institute of Biomedical Engineering (Kiev) and first tested at the Vardinoyannion Eye Institute of Crete is a promising technique for eye refraction aberration and refraction mapping. METHODS: The technique uses measurement of the position of a thin laser beam projected onto the retina. The beam is directed into the eye parallel to the visual axis. Each entrance point provides its own projection on the retina. A set of entrance points forms a set of projections. From these data, a refraction map is reconstructed as well as a point spread function of the eye. The total time of scanning over the whole aperture of the eye is within 10 to 20 ms and depends on the number of test points at the eye entrance, as well as on the number of independent measurements in each point. Configuration of the scanning pattern can be chosen by the operator. It may contain 60 to 400 points, each checked 1 to 5 times. RESULTS: Preliminary studies showed high reproducibility of results. Twenty pseudophakic eyes were subjected to 30 consecutive measurements each. Ninety-five percent of all measured values were within +/-0.20 D of declination from the mean. CONCLUSIONS: Ray tracing aberrometry is a flexible technology for eye investigation. It can be adapted to any laser technique of vision correction Its further development should be oriented on laser-linked applications of the refraction driven refractive surgery.

Clinical experience with the Tracey technology wavefront device.

PURPOSE: In refractive surgery, measuring the total ocular profile of refraction gives more vital information than measuring the cornea alone. We report the first clinical experiments with spatially resolved refractometry using ray tracking principles. Tracey technology was developed in Ukraine by the Institute of Biomedical Engineering in cooperation with the Vardinoyannion Eye Institute of Crete. METHODS: The Tracey-1 device was evaluated in comparison with conventional videokeratoscopes. Seven pseudophakic eyes of 7 patients and two phakic eyes were measured thirty (30) consecutive times (consecutively) each to test reproducibility. Measurements were provided in zones 0 to 5 (6) mm. For each zone, parameters of astigmatism were calculated and mean value and standard deviation were derived. RESULTS: Standard deviation on the order of 0.14 D was derived. CONCLUSION: The Tracey Technology wavefront device provides information on the refraction distribution at the first principal plane of the ocular optical system. For the instrument to provide measurements that are directly applicable to clinical practice, the data should be transposed to the corneal plane. The Tracey device can be utilized for the measurement of accommodative amplitude and range. Further development of the instrument is requred to increase its accuracy.

Ciliary body PDT in pigmented rabbit eyes: effect of single and repeated treatment.

PURPOSE: To investigate the morphologic and hypotensive effect of contact transscleral ciliary body PDT in pigmented rabbit eyes. METHODS: The right eyes of 33 pigmented rabbits were irradiated using chloraluminum sulfonated phthalocyanine as photosensitizer and a diode laser (670 nm) as the light source. Twenty-five animals received a single treatment. Eight animals received a second treatment 13 days after the first one. Photosensitizer was administered by means of continuous intravenous infusion. Ciliary body was irradiated transsclerally by means of an optic fiber applied on the corneoscleral limbus. In all cases 14-16 laser applications were performed to cover 360 degrees of the ciliary body. Animals were followed for a maximum of 30 days by means of tonometry and biomicroscopy. Retreatments were performed using the same irradiation protocol. At the end of the follow up time animals were sacrificed and their were eyes prepared for light and electron microscopy. RESULTS: Transscleral ciliary body PDT resulted in significant but temporary reduction of IOP in all cases. The effect lasted about two weeks. Retreatment led to a new significant drop of the IOP, which lasted about two weeks again. In histological examination the initial effect was vascular thrombosis, followed by edema and disintegration of the ciliary epithelial layers. In all cases the appearance of the ciliary body had returned to normal 15 days after irradiation. CONCLUSION: Contact transscleral PDT with the treatment parameters used in this study results in significant but temporary functional and morphological alteration in pigmented rabbits ciliary body.

Contact lens fitting difficulties following refractive surgery for high myopia.

PURPOSE: To describe the clinical and optical problems encountered in contact lens fitting following refractive surgery for high myopia. METHODS: Following refractive surgery for high myopia (greater than -10.00 D) we corrected residual refractive errors with contact lenses in the four eyes of two patients. The first patient had undergone bilateral laser in situ keratomileusis (LASIK),with two subsequent LASIK retreatments in the left eye. Ten months later she was fit with rigid gas permeable (RGP) lenses in both eyes. The second patient had undergone a clear lens extraction in the right eye and radial keratotomy followed by photorefractive keratectomy(PRK) in the left eye. She was fit with toric soft lenses six years postoperatively. RESULTS: Final visual acuity obtained with contact lenses was 20/25-20/20 in all eyes. The first patient required significant minus lens power compensation. Furthermore, the RGP lens in the left eye was slightly decentered due to corneal irregularity induced by LASIK. The second patient had regular corneal surfaces and was successfully fit with daily wear toric soft lenses despite the 2.75 D of residual astigmatism in the left eye. CONCLUSIONS: Following refractive surgery for high myopia a proportion of patients will remain undercorrected. In these patients the alterations in corneal architecture that ensue make contact lens fitting more challenging. Patients with regular astigmatism may be fitted successfully with toric soft lenses. Patients with corneal irregularities should be fit with RGP lenses.

Crete, Greece glaucoma study.

PURPOSE: To investigate the prevalence of primary open-angle glaucoma (POAG) in a randomized sample of the inhabitants of the island of Crete. PATIENTS AND METHODS: In 18 different villages in all four prefectures of the island of Crete, patients were randomly selected from 1993 through 1998, and an in situ study was accomplished. The sampling fraction (covered by the 1991 census) in each village was approximately 5%. Patients were considered to have POAG when the morphologic aspect of a glaucomatous optic disc was present, and/or a nerve fiber layer defect and a visual field defect was present. The presence of Pseudoexfoliation syndrome (PEX) and pseudoexfoliative glaucoma (PEXG) was also investigated. RESULTS: The prevalence of glaucoma in Crete was 2.80%. Of those diagnosed with POAG, 9.67% had an intraocular pressure (IOP) under 21 mm Hg, and 25.80% had PEX. The prevalence of simple ocular hypertension without glaucoma was found in 6.58% of the patients. The ratio of subjects with hypertensive glaucoma to those with simple ocular hypertension was 1:2.6. CONCLUSION: The prevalence of POAG and exfoliation glaucoma appears to be quite high in Crete. Further research will be needed to set more accurate criteria for earlier diagnosis and to enable more efficient organization of the health care system.

The use of atomic force microscopy for the observation of corneal epithelium surface.

PURPOSE: To evaluate the feasibility of imaging normal corneal epithelium by means of atomic force microscopy (AFM). METHODS: Twelve normal corneas from six albino rabbits were examined using a commercial atomic force microscope. Six corneas were examined in balanced salt solution after fixation in glutaraldehyde 2.5% and six without any fixation. Rectangular silicon nitride cantilevers with a spring constant of 10 to 20 mN/m were used. The measured forces after imaging were less than 100 pN. All reported images were made with 512x512-pixel definition with typical scan rates ranging from 1 to 5 Hz. RESULTS: High-quality images of corneal epithelium surface were obtained from fixed and unfixed specimens in magnifications ranging from x2000 to x2,000,000. Imaging of fixed specimens was always easier. In unfixed specimens fuzzy images were very common, probably because of the presence of the cell glycocalyx. AFM revealed the typical polygonal corneal epithelial cells. The cell surface was covered by microprojections; at cell borders the microprojections were arranged in two characteristic parallel rows. Craterlike formations were revealed in several specimens. The microprojections' morphology and their surface details were revealed using magnifications up to x2,000,000. Three-dimensional representation of the images facilitated better understanding of the surface topography. Measurements in horizontal and vertical plane were made using the section analysis tool. CONCLUSIONS: In this work the AFM parameters appropriate for corneal epithelium imaging in physiological medium were defined. AFM represents a new powerful tool for corneal epithelium imaging, and its application in this field warrants further investigation.

Evaluation of tear secretion and tear film stability in pseudoexfoliation syndrome.

PURPOSE: In pseudoexfoliation syndrome, a material of unknown composition is deposited at the anterior structures of the eye and at periorbital tissues such as the conjunctiva, where goblet cells and accessory lacrimal glands are located. In this study, the possible effect of pseudoexfoliation on tear secretion and tear film stability was investigated. METHODS: Tear film break-up time and Schirmer tests were performed on 108 eyes of 57 patients with pseudoexfoliation and 120 eyes of 60 normal subjects. Results were statistically analyzed. RESULTS: Both Schirmer test and break-up time scores were significantly lower in the pseudoexfoliative patients (average values 10.13 mm and 6.91 sec, respectively) compared to the control group (average values 12.75 mm and 12.75 sec, respectively). The difference was more prominent in males. CONCLUSION: The lower scores in Schirmer and break-up time tests in the pseudoexfoliation group could be attributed to conjunctival involvement. Pseudoexfoliative patients could be more prone to developing xerophthalmia, especially if they are treated with beta blockers.