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Biomedical subjects

W Williamson

Publications and source records attributed to W Williamson.

34 records · Page 2Linked to original sources
PubMed1993

[The Schocket tube. A retrospective study of 36 cases].

Thirty-six eyes with refractory glaucoma were operated using a Schocket technique (anterior chamber shunt to an encircling band). The follow-up was more than one year in all cases with a two-year maximum follow up. The intraocular pressure was < or = 25 mmHg in 87.5% to 95% of cases, and < 21 mmHg in 75.8% to 81.5% of cases. The results were analysed for each etiology and compared with those of other series and those of other surgical techniques used in the treatment of this type of glaucoma. (Molteno drainage tube, cyclodiathermy, ultrasonic treatment and yag laser transcleral contact cyclophotocoagulation).

Adolescent↗
PubMed1993

[Values and complications of peripheral deepenings in radial keratotomies].

Single and double peripheral deepenings were used to increase the refractive effect of radial keratotomy (RK). The objective of this study was to statistically evaluate the effect and the complications of these surgical techniques. Simple and double peripheral deepenings were performed in 36 patients (52 eyes) and 14 patients (19 eyes) respectively. The functional results and the complications in these two groups were statistically compared with those of a control group which was comparable according to criteria of size, age, sex and preoperative myopia. The standard RK surgical technique was used in this control group. The difference of mean gain between the control group, and the single and double peripheral deepening groups, was 0.53 and 0.47 diopter, respectively. This difference was statistically significant. On the other hand there was no significant difference diopter gain between the single and the double peripheral deepening groups. There was a significant difference concerning spherical equivalent. The non corrected visual acuity was significantly higher in the peripheral deepenings groups, probably due to corneal topographic alterations generating multifocal corneas. The complication rate (micro-perforations, induced astigmatism, loss of best corrected visual acuity) was higher in the peripheral deepenings groups. The limited diopter gain (about 0.50 diopter) compared with the standard radial keratotomy surgical technique, the lack of decreased, reoperation rate and the increased rate complication justified peripheral deepenings surgery technique discussed by the authors.

Adult↗
PubMed1993

[Results of reoperation for under correction of radial keratotomies. Apropos of 25 cases].

Twenty-two under corrected patients (25 eyes) after radial keratotomy, were reoperated according to the Stan Franks surgical technique. The results and the possible factors of predictability of this method of reoperation were evaluated. The residual myopia was less than one diopter in 88% of cases (20% before reoperation). The non corrected visual acuity was superior or equal to 20/40 in 88% of cases (32% before reoperation). The mean dioptrie gain after reoperation was 1.30 diopters. Statistical analysis showed that the refractive gain significantly increased with: the initial residual myopia, the delay between the first radial keratotomy and the reoperation, the number of incisions concerned. Age, sex, corneal thickness, initial protocol and presumed cause of undercorrection were not correlated to the refractive gain. (concerning the mean dioptrie gain). The comparison between data derived from different studies, showed no significant differences between the techniques of reoperation. Induced astigmatism with loss of best corrected visual acuity in 12% of cases was the main complication. The causes of under correction after radial keratotomy, and the effectiveness of the Stan Franks method of reoperation are discussed. The authors emphasize the interindividual corneal reaction to radial keratotomy.

Adult↗
PubMed1992

[Multifocal and monofocal implant. Comparative functional results (contrast sensitivity and dynamic visual acuity)].

The functional results (contrast sensitivity and dynamic visual acuity) of 19 multifocal (3 M design) and 14 monofocal intraocular (IOL) were compared. Best corrected visual acuity was > or = 8/10 P 2. Major differences of functional performance in favour of monofocal IOL's were found under standard conditions of vision (low contrast and illumination levels). Dynamic visual acuity allowed accurate evaluation of the difference of performance between these two models of implant. The indications for multifocal IOLs were reconsidered in the light of these results.

Aged↗
PubMed1992

[Diagnosis of ocular chlamydiosis by gene amplification (polymerase chain reaction or P.C.R.)].

Identification of conjunctival chlamydioses could be very difficult since this disease is extremely latent. Moreover previous instillation of topical antibiotic provokes a negativation of D.I.F. and of cultures. P.C.R. is very useful, it was demonstrative in 41 cases out of 47 cases; D.I.F. was positive only in 18 cases. P.C.R. is a very promising method to recognize chlamydiae; identification of different serovars is processing.

Chlamydia Infections↗
PubMed1991

[Cataract in Senegal].

1000 cataracts were cured thanks to surgery at the Ophthalmological Centre of BOPP in Dakar. The authors analyzed them according to several aspects (age, sex, aetiology and anatomical shape of the cataracts), according to the therapeutical results and complications. When having compared extracapsular and intracapsular, they stress the double problem of prevention and treatment of endophthalmia and of optical correction of aphakia at a health centre.

Adolescent↗
PubMed1990

[Bilateral corneal neovascularization and floppy eyelid syndrome. A case report].

The conjunctival and corneal lesions usually observed in the floppy eyelid syndrome are benign and reversible as soon as the specific treatment of superior palpebral hyperlaxity is performed. A case of bilateral corneal vascularization, a rare but severe complication of floppy eyelid syndrome is reported. The floppy eyelid syndrome was identified late because keratoconjunctivitis was clinically predominant and palpebral tonicity was not initially considered. The treatment of palpebral hyperlaxity was the prerequisite for good results with keratoplasty.

Aged↗
PubMed1978

Microbodies of the pig liver. A morphologic and morphometric study.

The ultrastructure of hepatic microbodies of pigs was studied in liver samples fixed in phosphate-buffered 2% glutaraldehyde (pH 7.4) and postfixed in 2% osmium tetroxide. The microbodies were rounded or ovoid in shape and contained a granular matrix enclosed with a single limiting membrane. The matrix, in many of the organelles, contained an amorphous or an organized (crystalloid) area. The crystalloids were organized as fine, alternating electron-opaque and electron-lucent lines, or as groups of tubules arranged in more than one plane. Profiles of smooth endoplasmic reticulum were usually found near the microbodies. 34 microbodies were approximately 0.67 +/- 0.02 micrometer (mean +/- standard error) in length and were approximately 0.56 micrometer (+/- 0.02 micrometer) wide. The marginal plates consisted of strata which exhibited a periodicity. The average length and width of 17 plates was approximately 0.34 +/- 0.03 micrometer and 0.002 micrometer, respectively. This study clearly establishes the occurrence of marginal plates in microbodies of porcine liver.

Animals↗
PubMedDate not supplied

Energy fluctuations in an excimer laser during photorefractive keratectomy.

We performed an experiment with the MEL 60 excimer laser (Aesculap Meditec Technology) to demonstrate the variations of energy of the laser beam that could happen during a refractive surgical procedure. In order to quantify such variations, we measured the whitening of a photographic paper after a series of exposures to the laser beam with the X rite 400 B/W reflection densitometer. The energy fluctuations noted between two series of pulses averaged 11.02% (minimum 0; maximum 46). These fluctuations tended to decrease progressively during the procedure. The energy of the laser beam decreased with time. At the end of the experiment, the total loss of energy was 45.16%. These results suggest that clinically meaningful energy variations could happen during the photorefractive keratectomy and reduce refractive predictability.

Cornea↗
PubMedDate not supplied

Effect of peripheral deepening of radial keratotomy incisions.

BACKGROUND: Single and double deepening of the peripheral part of radial keratotomy incisions are used to increase the refractive effect. METHODS: Single peripheral deepening was performed in 52 eyes of 36 patients and double peripheral deepening in 19 eyes of 14 patients who received radial keratotomy. RESULTS: In the single peripheral deepening group, the mean change in refractive power was 4.01 diopters (D); 53.8% of eyes were within +/- 1.00 D of emmetropia; residual myopia was greater than -1.00 D in 46.2% of eyes; 65.4% of eyes achieved an uncorrected visual acuity greater than or equal to 20/40. In the double peripheral deepening group, the mean change in refractive power was 5.07 D; 52.6% of eyes wee within +/- 1.00 D of emmetropia; residual myopia was greater than -1.00 D in 47.4% of eyes; 89.4% of eyes achieved an uncorrected visual acuity greater than 20/40. The difference in mean dioptric change between the standard radial keratotomy groups and the single and double peripheral deepening groups was 0.53 D and 0.47 D, respectively. CONCLUSIONS: Considering the limited additional dioptric change compared with the standard radial keratotomy surgical technique and the increased rate of complications, we think that peripheral deepening in radial keratotomy should be avoided.

Adult↗