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Biomedical subjects

D S Siganos

Publications and source records attributed to D S Siganos.

At least 19 recordsLinked to original sources
PubMed2000

Clear lens extraction and intraocular lens implantation in Marfan's syndrome.

Intracapsular clear crystalline lens extraction and intraocular lens (IOL) implantation were performed in 4 highly myopic eyes of 2 patients with Marfan's syndrome. One eye of each patient received an anterior chamber IOL and the other, a scleral-fixated posterior chamber IOL. The preoperative spherical equivalent ranged between -14.50 and -28.00 diopters (D) and axial length range, between 25.32 and 36.02 mm. The SRK II formula was used. Mean uncorrected visual acuity improved from counting fingers to 20/80. Postoperative spherical equivalent correction ranged from -0.75 to +2.75 D. One eye had vitreous loss that was managed by anterior vitrectomy. Modern surgery for cataract and management of its complications suggest that clear crystalline lens extraction and IOL implantation can be attempted in selected cases with Marfan's syndrome.

Adult↗
PubMed2000

Tear secretion following spherical and astigmatic excimer laser photorefractive keratectomy.

PURPOSE: To evaluate the effect of spherical and astigmatic excimer laser photorefractive keratectomy (PRK and PARK, respectively) on tear secretion. SETTING: The Vlemma Eye Center, Athens, Greece. METHODS: Forty-eight eyes of 48 patients had PRK (28 eyes) or PARK (20 eyes) for the correction of myopia and combined myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent was -3.96 diopters (D) +/- 1.00 (SD) in the PRK eyes (range -2.00 to -6.50 D) and -3.45 +/- 0.50 D in the PARK eyes (range -1.75 to -6.00 D). Attempted correction aimed at emmetropia. Schirmer I and II and tear film breakup time (BUT) tests were performed preoperatively and 1, 3, and 6 months postoperatively. All tests were correlated to the amount of attempted correction. RESULTS: In the PRK group, the preoperative mean values were Schirmer I, 16.20 mm; Schirmer II, 12.73 mm; and BUT, 16.46 sec. At 1 month, they were 12.23 mm, 8.46 mm, and 13.33 sec, respectively; at 3 months, 13.86 mm, 10.64 mm, and 14.42 sec, respectively; at 6 months, 14.32 mm, 11.32 mm, and 15.36 sec, respectively. In the PARK group, the mean Schirmer I, II, and BUT values were preoperatively 18.52 mm, 14.86 mm, and 17.42 sec, respectively; at 1 month, 14.5 mm, 10.4 mm, and 14.36 sec, respectively; at 3 months, 15.36 mm, 11.81 mm, and 14.72 sec, respectively; and at 6 months, 16.5 mm, 12.15 mm, 16.5 sec, respectively. No correlation to the amount of attempted correction was found. Fellow-eye tests were not affected at any interval. CONCLUSIONS: In the first 6 months after PRK and PARK, tear secretion test values decreased.

Adult↗
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

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↗
PubMed1999

Seven years experience with LASIK for myopia.

PURPOSE: This paper presents the results of the last seven years with LASIK for the treatment of myopia. METHODS: 4170 eyes of 3163 patients with a mean preoperative spherical equivalent--9.66 diopters were submitted to LASIK. The eyes were divided in three groups according to the preoperative refraction: Group A (-5 to 10D), group B (-10 to 16D) and group C (over -16 D). RESULTS: At one year the percentage of eyes within +/- 1D of emmetropia was the following: group A: 84.4%, group B: 70.8%, and group C: 42.8%. CONCLUSIONS: The method is safe, effective, and predictable especially in the range of myopia between -5 and -15 D of myopia. Predictability could be further improved by secondary procedures.

Follow-Up Studies↗
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↗
PubMed1996

Photorefractive keratectomy with a transition zone for myopia from -7 to -14 diopters.

PURPOSE: To study transition zone excimer laser photorefractive keratectomy (PRK) in moderate and high myopia defined as a spherical equivalent of -7.00 diopters (D) or more. The follow-up period was 18 months. METHODS: Forty eyes of 40 patients with myopia of 7.00 to -13.50 D (mean +/- SD, -921 +/- 1.98) underwent transition zone (5.0 to 7.0 mm transition zone) PRK using the Aesculap Meditec Mel 60 excimer laser. The mean attempted correction was 8.3 +/- 1.64 D (range: -6.50 to -12.00 D). RESULTS: At 18 months, 83% achieved an unaided visual acuity of 20/50 or better and HOW 12% 20/25 or better. Eighty-eight percent were within +/-2 D of emmetropia. the mean spherical equivalent was -1.1 D (+3.00 to -9.00 D). CONCLUSIONS: Transition zone PRK is useful in moderate to high myopia. Regression, as well as overcorrection are issues for further investigation.

Adult↗
PubMed1996

Excimer laser phototherapeutic keratectomy for corneal opacities and recurrent erosion.

BACKGROUND: Phototherapeutic keratectomy (PTK) has been used to treat superficial corneal opacities, as well as the recurrent corneal erosion syndrome. METHODS: We performed PTK 6 eyes of 6 patients to treat corneal opacities, and in one eye of another patient to treat recurrent corneal erosion syndrome. Opacities were caused by a healed corneal ulcer, herpetic keratitis, band keratopathy, corneal burn, corneal dystrophy, and an excised pterygium. The follow-up period ranged from 2 to 6 months. RESULTS: Corneal clarity improved to variable degrees in all eyes with corneal opacities. There was no recurrence in the Recurrent Corneal Erosion Syndrome. A hyperopic shift was observed in 2 eyes. CONCLUSIONS: PTK appears to be an effective alternative to penetrating keratoplasty in patients with selected anterior stromal opacities can treat the Recurrent Corneal Erosion Syndrome.

Adult↗
PubMed1996

Arcuate transverse keratotomy with a mechanical arcutome based on videokeratography.

Corneal topographic hardware was used to develop software analysis for configuration and localization of relaxing astigmatic arcuate incisions. The software is based on the assessment of the results of corneal topographic measurements, performed by the EyeSys Corneal Analysis System. Data assessment includes: A) plotting the dioptric power curves along the circular zones that may be considered appropriate for the placement of arcuate cuts; B) determination of the astigmatic axes position in each selected arc; and C) finding the position of points with the mean dioptric power value between the neighboring astigmatic axes which determine the proposed placement of the arcuate incisions. The new instrument developed for arcuate astigmatic keratotomy includes the algorithm for incision(s) disposition, the software, and the arcutome.

Algorithms↗
PubMed1992

Paraformaldehyde-induced keratitis after photorefractive keratectomy.

We examined three patients who developed keratitis after myopic photorefractive keratectomy. All patients were treated on the same day and in all three cases paraformaldehyde tablets were used for disinfection of the excimer laser iris cone. All patients developed an intense postoperative corneal inflammation that resulted in corneal opacities. In the first patient, the opacities were central and persisted for at least 4 1/2 months postoperatively. He became more myopic than before the operation. His best spectacle-corrected visual acuity worsened by four Snellen lines. In the other two patients, the corneal opacities were paracentral and of less density. Six months postoperatively, these opacities were barely seen. In these two patients the postoperative best spectacle-corrected visual acuity remained unchanged or improved one Snellen line compared to the preoperative level. In all three patients, astigmatism increased postoperatively. These observations suggest that paraformaldehyde tablets are not safe for the disinfection of the excimer laser iris cone.

Adult↗
PubMed1991

A corneal flap technique for laser in situ keratomileusis. Human studies.

Using a modified microkeratome, nasally based central corneal flaps were created on six human blind eyes at a depth of 300 microns. The flaps were allowed to heal with a bandage soft contact lens, using neither sutures nor bioadhesives. The optical quality of the corneas was evaluated with biomicroscopic examination, computer-assisted topography, and optical pachometry during a 3-month follow-up period. The maintenance of transparency and lack of distortion of the corneal surface 3 months after surgery support the concept that the flap technique may be useful in laser in situ keratomileusis.

Cornea↗
PubMedDate not supplied

Laser in situ keratomileusis to treat myopia: early experience.

PURPOSE: To present our early experience in methodology and results of laser in situ keratomileusis (LASIK) in treating moderate and high myopia. SETTING: Vardinoyannion Eye Institute of Crete and the Cornea and Refractive Surgery Service, Department of Ophthalmology, Heraklion University Hospital, Crete, Greece. METHODS: Forty-three moderately to highly myopic eyes has LASIK. Follow-up was between 12 and 24 months. The Draeger's rotor microkeratome was used to create a 150 microns thick 8.5 x 9.5 mm corneal flap, and the stromal bed was ablated for the myopic correction using the Munnerlynn photorefractive keratectomy algorithm. The preoperative spherical equivalent ranged from -8.50 to -25.87 diopters (D). Attempted correction ranged from 8.00 to 16.00 D. Four eyes developed complications (i.e., anterior chamber perforation and keratoconus, intrastromal epithelial cells, macular lacquer cracks, and transient endothelial decompensation) and were excluded from the study. The remaining 39 eyes were retrospectively divided into two groups--A (21 eyes) and B (18 eyes)--according to the preoperative spherical equivalent (higher or lower than -14.00 D, respectively). RESULTS: Refraction and corneal topography stabilized between 4 and 12 weeks postoperatively. Best spectacle-corrected visual acuity was within one Snellen line in all eyes. At 24 months, 19 eyes (79.2%) were within 2.00 D of intended correction. Attempted correction (12.20 D +/- 2.30 [SD]) was very close to mean achieved correction at 12 and 24 months (11.60 +/- 2.65 D). Mean postoperative astigmatism at 24 months (1.41 +/- 0.87 D; range 0 to 3.50 D) was close to the mean preoperative value (1.52 +/- 1.08 D; range 0 to 4.00 D). An average 2.43% endothelial cell loss was observed at 24 months. CONCLUSION: With limitations, LASIK could be considered as a treatment for moderate and high myopia.

Adult↗
PubMedDate not supplied

Clear lensectomy and intraocular lens implantation for hyperopia from +7 to +14 diopters.

BACKGROUND: Our results of clear lens extraction and intraocular lens implantation to correct hyperopia from +6.75 to +13.75 D are presented, as well as evaluation of two intraocular lens calculation formulae. METHODS: Clear lens extraction and posterior chamber intraocular lens implantation was performed in 35 normally sighted eyes of 21 patients with a mean baseline hyperopic spherical equivalent refraction of +9.19 +/- 0.34 D (range +6.75 to +13.75 D). The refractive goal was -1.50 D, using the SRK II formula in 17 eyes and the SRK-T formula in 18 eyes. Follow-up was up to 5 years. RESULTS: Mean uncorrected visual acuity after surgery was 0.8 (range 0.5 to 1.0). Stability of refraction was noted from the second month after surgery. No eyes lost any lines of spectacle-corrected visual acuity. Using the SRK II formula, 100% of eyes were within +/-1.00 D of emmetropia and with the SRK-T formula, 83.3% for a combined 91.4% of eyes within +/-1.00 D of emmetropia. One eye required intraocular lens exchange and another eye required photorefractive keratectomy for myopia. Both procedures were necessitated by an intraocular lens miscalculation of more than +/-2.00 D. Nineteen eyes (54.2%) developed posterior capsular opacification and were treated with Nd:YAG laser capsulotomy. CONCLUSION: Clear lens extraction is a safe, effective, and predictable procedure for the treatment of hyperopia from +6.75 to +13.75 D. The SRK II formula proved slightly superior to the SRK-T in intraocular lens calculation when using the "-1.50 D rule."

Adult↗
PubMedDate not supplied

Microbiological examination of bandage soft contact lenses used in laser refractive surgery.

BACKGROUND: Disposable soft contact lenses are known to be colonized by bacteria and play a key role in bacterial keratitis pathogenesis. Such lenses, commonly used after laser refractive surgery procedures in which postoperative corneal infiltrations are sometimes observed, are potentially a substrate for bacterial inoculation. This study evaluates the extent of such a contamination. METHODS: Sixty disposable lenses collected from 60 eyes of patients who underwent photorefractive keratectomy (PRK), photoastigmatic refractive keratectomy (PARK), or laser in situ keratomileusis (LASIK) for the treatment of myopia or hyperopia were collected under sterile conditions over 4 months and cultured in various media. Results were statistically analyzed and the correlation with clinical and epidemiological data was examined. RESULTS: Eleven (18.3%) of the examined lenses were contaminated with Staphylococcus epidermidis. No other bacteria or fungi were found. Contamination was significantly more common among female patients (P = .036). Correlation with the other clinical or operative parameters examined was statistically insignificant. CONCLUSIONS: Contamination was independent of the surgical procedure and females who were frequent users of eyelid cosmetics displayed higher contamination frequencies, suggesting that bacteria possibly originate from eyelid flora. The isolation of Staphylococcus epidermidis requires close postoperative surveillance, since it is a known cause of keratitis. Prophylactic postoperative treatment with tobramycin, gentamycin, or sulphonamides could be indicated.

Adolescent↗
PubMedDate not supplied

Photorefractive keratectomy in eyes with congenital nystagmus.

BACKGROUND: We report 2 eyes of 2 patients with nystagmus and myopia who underwent photorefractive keratectomy (PRK) to correct myopia. METHODS: A 32-year old male patient with a baseline spectacle-corrected visual acuity of 20/40 had PRK with an Aesculap Meditec MEL 60 excimer laser with a suction ring system for correction of a spherical equivalent of -8.25 diopters (D). A 19-year old male patient with baseline spectacle-corrected visual acuity of 20/50 had PRK with an Autonomous Technologies T-PRK flying spot and tracking excimer laser to correct a spherical equivalent of -5.00 D. RESULTS: Twenty-seven months after PRK, the operated eye of the 32-year old patient had an uncorrected visual acuity of 20/32 and a spectacle-corrected visual acuity of 20/25. Six months postoperatively, the operated eye of the 19-year old patient had uncorrected and spectacle-corrected visual acuity of 20/50. CONCLUSION: Patients with nystagmus are eligible for PRK to correct their refractive error with these two laser systems.

Adult↗