Biomedical subjects

I G Pallikaris

Publications and source records attributed to I G Pallikaris.

At least 19 recordsLinked to original sources

PubMed2006

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.

Accidents, Traffic↗

PubMed2003

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.

Animals↗

PubMed2002

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.

Aged↗

PubMed2001

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.

Adult↗

PubMed2001

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.

Chronic Disease↗

PubMed2000

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.

Adult↗

PubMed2000

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.

Animals↗

PubMed2000

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.

Adult↗

PubMed2000

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.

Aluminum↗

PubMed1999

Correlation between age-related macular degeneration and pseudoexfoliation syndrome in the population of Crete (Greece).

OBJECTIVE: To evaluate the epidemiological correlation between age-related macular degeneration and pseudoexfoliation syndrome in the inhabitants of the island of Crete (Greece). SUBJECTS AND METHODS: A total of 777 persons (315 men and 462 women, aged 40-99 years), representing a randomized sample (1.43%) of the Cretan population, underwent slitlamp and fundus examinations according to protocol. The results were statistically analyzed. RESULTS: The prevalence of pseudoexfoliation was 16.1% (21.3% in men and 12.6% in women) and that of maculopathy, 7.9% (11.7% in men and 5.2% in women). The conditions were significantly correlated with each other (P = .002). Also, both displayed a significant direct correlation with age and altitude (for pseudoexfoliation, P<.001 and P = .002 for age and altitude, respectively; for age-related macular degeneration, P<.001 for age and for altitude) and an increase in bilateral incidence with progressing age. CONCLUSIONS: The observed prevalences of pseudoexfoliation and maculopathy were lower than those reported in the mainland of Greece and other Mediterranean regions. The correlation between age-related macular degeneration and pseudoexfoliation syndrome may be explained by the relationship of each disease with age and altitude.

Adult↗

PubMed1999

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.

Aged↗

PubMed1999

Loss of heterozygosity in pseudoexfoliation syndrome.

PURPOSE: Pseudoexfoliation (PEX) syndrome is characterized by the accumulation of a material of unknown origin in the anterior structures of the eye. Loss of heterozygosity (LOH) in a genetic locus indicates the presence of a gene located in the same region that could be implicated in the development or the progression of a disease. In this study, the occurrence of LOH in tissues involved in PEX and the possible correlation of LOH incidence with clinical parameters were evaluated. METHODS: Twelve iris specimens, 12 anterior capsule specimens, and respective blood samples were obtained from 17 patients with PEX (13 men), who were undergoing glaucoma and cataract surgery. Sixteen anterior capsule specimens and four iris specimens were obtained from 16 patients without PEX. Polymerase chain reaction was used to amplify 10 highly polymorphic microsatellite markers located on chromosomes 1, 7, 9, and 13. RESULTS: Overall, 83.3% (20/24) of PEX specimens and 94.11% (16/17) of patients with PEX had LOH. The highest incidence of LOH was observed in marker D13S175 (41.6%) followed by D7S478 and D7S479 (37.5%). Only three non-PEX specimens displayed LOH. The number of loci lost was directly related to the altitude of the patients' present residence, but the number lost did not differ significantly between the iris and capsule samples. CONCLUSIONS: The occurrence of LOH in tissues involved in PEX implies a genetic role in PEX pathogenesis at a cellu lar level. The correlation of LOH incidence with the altitude of the patient's residence, could indicate an increased susceptibility to UV radiation of the chromosomal regions examined.

Aged↗

PubMed1999

Corneal epithelial wound healing after excimer laser photorefractive and photoastigmatic keratectomy (PRK and PARK).

PURPOSE: This study compared the duration of corneal reepithelialization between photorefractive (PRK) and photoastigmatic (PARK) keratectomy and evaluated the possible correlation of the epithelial healing rate with clinical parameters as well as the refractive outcome. METHODS: The duration until complete reepithelialization was examined in 33 eyes of 33 patients (14 men), not suffering from any known disease, who underwent PRK or PARK surgery. In all cases, a +0.5 diopters (D) therapeutic contact lens (Acuvue Vistakon) was used postoperatively. Clinical parameters such as age, sex, preoperative spherical equivalent, attempted correction, corneal curvature, and surgical plan were recorded in the patient file. All patients received standard medication and were followed up for 12 months postoperatively. Results were statistically analyzed by using the package SPSS 6.0. RESULTS: The duration of reepithelialization was significantly correlated to age and was longer in PARK than in PRK cases and in eyes with an average K reading >43.5D. A shorter reepithelialization period correlated to myopic regression, 1 month postoperatively, but the correlation was annulled thereafter. CONCLUSION: The longer reepithelialization period in older patients and in PARK surgery could be attributed to the age-related decrease in the healing response and to differences in the profile of the ablation area, respectively. Epithelial healing was shorter in eyes with steeper K readings, perhaps because of better contact lens mobility. Understanding the role of factors involved in epithelial healing could allow better postoperative surveillance and treatment.

Adolescent↗

PubMed1998

Topical use of zinc desferrioxamine for corneal alkali injury in a rabbit model.

PURPOSE: To evaluate the efficacy of topical zinc desferrioxamine in acute corneal alkali injury in rabbits. METHODS: Twenty rabbits were anesthetized and a standardized alkali burn (1N NaOH) was performed in the center of the cornea (7.5-mm diameter). The animals were randomly divided into two groups and treated (double-masked) with topical zinc desferrioxamine, 220 microM, (group 1) or its vehicle (group 2). Drops were applied 7 times/day for 28 days. Topical gentamicin, 0.3%, was instilled twice a day. Animals were evaluated twice a week. At each examination (using the slit-lamp), the depth of corneal ulcer was graded as follows: 0, no ulcer; 1, tissue loss less than one third of corneal thickness; 2, one third to two thirds tissue loss; 3, more than two thirds tissue loss; 4, descemetocele; or 5, perforation. Ulceration area, vascularization, and epithelial defects also were measured. RESULTS: During the study period, the grading of mean corneal ulcerations in group 1 ranged from 0.2 to 1.00, whereas in group 2, it ranged from 1.4 to 2.7. The mean grade and area of ulceration in group 2 were greater than those in group 1 (p < 0.05). CONCLUSION: Topical zinc desferrioxamine may be an adjunctive treatment in protecting the cornea against induced alkali injury.

Administration, Topical↗

PubMed1998

Needle entrance into the maxillary sinus during retrobulbar anesthesia.

Three patients are presented to whom an accidental needle entrance into the maxillary sinus occurred during retrobulbar anesthesia. In all cases air was aspirated during the aspiration check at the end of needle advancement, and the patients reported a bitter taste after the injection of a small quantity of anesthetic. After withdrawal and careful reinsertion of the needle, maxillary sinus entrance was avoided and a successful retrobulbar block was achieved. Two of the patients had no history of previous facial trauma or surgery, whereas the third had suffered a recent blowout fracture of the orbital floor. The authors suggest that air aspiration or anesthetic passage into the pharynx during retrobulbar anesthesia should raise the suspicion of maxillary sinus entrance, even in patients without any history of facial trauma or surgery. The early recognition of sinus entrance can prevent retrobulbar block failure and reinjection of a second anesthetic dose.

Aged↗

PubMed1998

Endothelial corneal damage after neodymium:YAG laser treatment: pupillary membranectomies, iridotomies, capsulotomies.

BACKGROUND AND OBJECTIVES: To evaluate the corneal changes after Nd:YAG laser pupillary membranectomies (group A), iridotomies (group B), and capsulotomies (group C) in a follow-up period of 6 months. PATIENTS AND METHODS: The Nd:YAG laser was applied to 3 different groups of patients. Specular microscopy, including the counting of corneal thickness and cell density, the percentage of hexagonal cells, and the cell area, was performed preoperatively and postoperatively. RESULTS: Some dark areas were recorded in the corneal endothelium in groups A and B. A nonstatistically significant decrease of cell density was recorded by the end of the first month. A significant loss of endothelial cells during the sixth month was recorded in groups A and C. CONCLUSION: The appearance of dark areas in the corneal endothelium is mainly related to the total energy delivered. The YAG laser treatments do not provoke an immediate and conspicuous loss of the endothelial cells, but may act as a stimulus for an accelerated loss of endothelial cells.

Aged↗

PubMed1997

Nd:YAG laser removal of pupillary membranes developed after ECCE with PC-IOL implantation.

PURPOSE: To define the frequency of development of pupillary membranes after ECCE with PC-IOL implantation, and to remove the pupillary membranes using the Nd:YAG laser. METHODS: From 400 patients who had undergone ECCE and were free from local or systemic illness affecting the blood-ocular barrier, 20 eyes developed pupillary membranes Nd:YAG laser was used to remove these pupillary membranes. RESULTS: The frequency of pupillary membranes was found to be 5% (9.8% in pex eyes and 3.3% to the non-pex eyes). Visual acuity improved in 17 eyes by 2 to 5 Snellen lines. No serious complications were observed, endothelium inclusive. CONCLUSION: Pseudoexfoliation might play a significant role in the development of postoperative pupillary membranes which could be successfully treated with the use of Nd:YAG laser. The safety of the procedure has to be evaluated in relation to the corneal endothelium damage in long-term.

Aged↗

PubMed1997

Epidemiology of pseudoexfoliation in the island of Crete (Greece).

PURPOSE: To evaluate the pseudoexfoliation (PEX) prevalence in the island of Crete (Greece). METHOD: Organized visits to various villages, to examine a predetermined number of people born and living in these villages, in collaboration with the local birth register offices. RESULTS: PEX prevalence in Crete, in people aged 40 years and more, was found to be 16.1% (men: 21.3%, women: 12.6% - Prefecture of: Heraklion 11.5%, Chania 13.4%, Lasithi 16.9%, Rethymnon 27%). 28.8% of PEX-patients presented IOP > 21 mmHg. In unilateral PEX-patients, mean IOP of PEX-eyes was found to be 17.82 mmHg versus 15.6 mmHg in fellow eyes. CONCLUSION: PEX prevalence was higher in men than in women and increases with age, as does bilaterality. A correlation between increased PEX prevalence and high altitude may exist. PEX is a risk factor for the development of IOP disturbances which seem to appear earlier in women.

Adult↗