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Biomedical subjects

S P Percival

Publications and source records attributed to S P Percival.

At least 19 recordsLinked to original sources
PubMed1991

Comparative analysis of three prospective trials of multifocal implants.

A clinical analysis of best cases four to 12 months postoperatively was made to assess the function of 47 3M multifocal implants, 40 Iolab multifocal implants and 24 AMO multifocal implants. Overall 86 (79%) eyes could see 6/12 and N6 unaided. The multifocal function for each lens worked well for distance, intermediate and near in the majority but an increase in depth of field was at a cost of reduced resolution efficiency. The 3M lens was associated with symptoms of poor optical quality in 29.8% and with an inability to read N5 with correction in 17%. The Iolab lens provided better reading vision but less good distant vision than the other types and was associated with symptoms of poor optical quality in 15%. Many of these had a pupil diameter greater than 3.5 mm. The AMO lens gave a poorer unaided reading vision than the other lens types but had the lowest incidence of optical symptoms.

Humans↗
PubMed1989

Prospective study of the new diffractive bifocal intraocular lens.

The visual results of 55 bifocal lens implantations are compared with 55 matched PMMA monofocal implantations. 84% of the eyes with bifocal implants compared with 20% of the eyes with monofocal implants could read N8 or better with the distance correction (p less than 0.001). 52% of +/- 3.5D bifocal eyes could read N5 with the distance correction. The mean reading addition for a near point of 25 cm was 0.3D in the bifocal group and 2.2D in the monofocal group. 20% of eyes with bifocal implants could not be corrected to N5 at a comfortable distance (p = 0.005). It was found that the clear advantages of this bifocal lens must be countered in a minority by a loss in quality of vision particularly for reading.

Aged↗
PubMed1989

Intraocular lens design and the inhibition of epithelium.

Of 1170 eyes implanted with posterior chamber lenses between 1981 and 1986 and having intact capsules at surgery, 1015 were examined two years after surgery, 741 were examined three years after surgery, and 308 were examined five years after surgery. At three years the capsulotomy rate for epithelium was 25% for 263 'lasergap' lenses, 2.4% for 296 convex posterior lenses, 8.2% for 73 planoposterior lenses with angulated loops. The highly significant difference for lasergap design, whether ridged, meniscus, or bossed, is of immediate interest to surgeons concerned with minimising the need for secondary capsulotomy. The two-year follow-up of soft hydrogel lenses suggested that these lenses also do not significantly retard the ingrowth of epithelium.

Adult↗
PubMed1988

Analysis of the need for secondary capsulotomy during a five-year follow-up.

From 783 consecutive extracapsular cataract extractions with intact posterior capsules at the close of surgery, 655 eyes were available for examination three years after surgery and 447 eyes were available five years after surgery. By five years postoperatively, the need for secondary capsulotomy was 49% of 67 eyes that had not received an implant, 23% of 159 eyes that had received a Binkhorst iridocapsular lens, and 13% of 221 eyes that had received a posterior chamber lens. Among posterior chamber lenses, the surface area of the implant was considered to be a more important factor in inhibiting capsule opacification than posterior vaulting of the lens. Posterior vaulting was associated with a lower incidence of epithelialization but a higher incidence of capsular fibrosis. A small subgroup of 19 glaucoma triple procedures examined at three years showed a significantly higher incidence of capsulotomy (21.0%) than the other 369 posterior chamber lens implantations examined at three years (6.8%).

Adult↗
PubMed1988

Hydrogel intraocular lens experience with endocapsular implantation.

The experience is presented of three independent surgeons using Hydrogel posterior chamber intraocular lenses in a combined series of 157 endocapsular cataract extractions. One hundred and fifty of these eyes were examined after a minimum follow-up period of one year and 92.0% achieved visual acuity of 6/12 or better, and 98.6% achieved this if pre-existing pathology was excluded. Insertion of this lens has proved to be simple, the adaptions of technique required are described and the complications are presented and analysed.

Aged↗
PubMed1988

Radial keratotomy: where did it go wrong?

A prospective study was set up to determine the effectiveness, predictability, stability, safety and feasibility within the National Health Service of radial keratotomy. The methods adopted include a new simplified guide to surgery with a predicted accuracy in 84 of 100 operations. Ninety-six percent of eyes with myopia of -6.0D or less preoperatively were seeing 6/12 or better six months after surgery. Refraction remained stable within a range 0.5D spherical equivalent between the first and sixth postoperative months in 96%, between the first and twelfth postoperative months in 90% and between the first and second years in 100% of eyes examined. There were no cases of progressive hypermetropia. Sixty-four percent of the 61 patients admitted to postoperative symptoms. Three percent of eyes lost best corrected vision. The disappointments were few but were analysed in detail. The least reliable were found to be associated with the higher myopes requiring a 3.0 mm clear optical zone.

Adult↗
PubMed1987

Early experience with soft hydrogel lens implants.

A new material which more closely mimics the properties of living tissue than polymethylmethacrylate is under investigation. Twelve hydrogel lenses were placed into the ciliary sulcus following the standard nucleus extraction technique and 38 were placed into the lens capsule using the endocapsular technique. Six months following surgery 66 per cent of sulcus fixated lenses were found to have both haptics in the sulcus and 76 per cent of capsule fixated lenses were found to have both haptics encapsulated. The hydrogel lens was found to be well tolerated within the eye with 32 per cent of eyes achieving a visual acuity of 6/5 and 94 per cent achieving 6/12 or better.

Aged↗
PubMed1987

Redefinition of high myopia: the relationship of axial length measurement to myopic pathology and its relevance to cataract surgery.

Owing to growing confusion over the true incidence of RD in HM after cataract surgery, a new definition for HM has been formulated based on measurement of axial length. Of 38 noncataractous phakic eyes with treated RD, 45% were found to have axial lengths more than 1 mm longer than would be expected from the eye's refraction. Of 180 moderate to highly myopic eyes examined 2 years after extracapsular extraction with lens implantation, 2 were found to have developed RD. Using the historic definition for HM by refraction (spectacle equivalent of -6.0 dptr or more), the incidence of RD was found to be 1/62 eyes (1.6%) but using the improved definition of axial length 26.5 mm or more, the incidence was found to be 2/49 eyes (4.1%). Both these studies suggested that axial length, in addition to myopic pathology, is a factor associated with RD and that a definition of HM based on axial length is more appropriate than that based on refraction.

Cataract Extraction↗
PubMed1985

Results of a clinical trial of sodium hyaluronate in lens implantation surgery.

The results from a four-year clinical trial on the use of sodium hyaluronate (Healon) are presented. Six hundred three consecutive primary lens implantations were performed: 500 after extracapsular cataract extraction and 103 after intracapsular cataract extraction. The safety and efficacy of Healon were analyzed by examining postoperative ocular hypertension, uveitis, visual acuity, and endothelial cell loss. The results of the trial confirm that Healon is safe and effective and, provided it is not used in excessive quantities, free from serious side effects.

Aged↗
PubMed1985

Glaucoma triple procedure of extracapsular cataract extraction, posterior chamber lens implantation, and trabeculectomy.

Thirty-four consecutive glaucoma triple procedures with a minimum follow up of six months have been shown to be effective and safe. Satisfactory control of the glaucoma was achieved in each case, and 91% of eyes were returned to an acuity of 6/12 or better. 1% sodium hyaluronate was found to be beneficial by preventing scleral or corneal collapse during surgery and ensuring an even filtration postoperatively without hypotony.

Aged↗
PubMed1985

Long term complications from extracapsular cataract surgery.

Long term follow up of extracapsular extraction showed visual results superior to those previously reported for intracapsular extraction. Ninety-six per cent of 197 eyes examined five years after extracapsular extraction with capsule supported lens implantation had a visual acuity of 6/12 or better. Of the 498 cases examined three years after surgery, including eyes without implants, 93 per cent had a visual acuity of 6/12 or better. Complications were rare provided the posterior capsule remained intact. Forty-five per cent of eyes without implants had required secondary capsulotomy within three years of surgery, compared with 11 per cent of eyes in which Binkhorst lenses had been used. Only 27 per cent of the eyes with Binkhorst lenses examined seven years after surgery were found to have required secondary capsulotomy. Opening of the capsule was seen to increase the risk of sight threatening complications, in particular of retinal detachment in high myopes. Implantation of posterior chamber lenses appeared to reduce the need for capsulotomy even further and it is suggested that their use in high myopia may help to lessen the chance of retinal detachment.

Adult↗
PubMed1985

Sodium hyaluronate in perspective: experiences from a four-year clinical trial.

Analysis of the safety from the use of 1 per cent sodium hyaluronate (Healonid) is presented in terms of postoperative ocular hypertension, uveitis, visual acuity and endothelial cell loss. The results of a four-year clinical trial confirm that this product is safe and effective. There was no significant difference in the short term visual results from its use, however on assessment of comparative endothelial cell studies, it was found that incidences of severe cell loss tend to be excluded by the use of Healonid so improving the surgeons confidence in difficult surgical situations.

Adult↗
PubMed1977

Results after intracapsular extraction: the atonic pupil.

Satisfactory visual results are reported in a series of 80 consecutive patients who underwent intracapsular cataract extraction with a four- or three-loop Binkhorst lens replacement. Nearly 50% of patients could see 20/30 or better unaided. However, results in the under 70 age group tend to be marred by macular edema, and in the over 80 age group by corneal edema, the latter occasionally being the result of lens instability because of an atonic pupil.

Aged↗