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Biomedical subjects

R L Johnston

Publications and source records attributed to R L Johnston.

At least 19 recordsLinked to original sources
PubMed2006

National Biometry Audit II.

PURPOSE: To determine the change in compliance with the Royal College of Ophthalmologists biometry guidelines since the last National Audit 2 years ago and in particular to quantify the adoption of modern methods of axial length measurement and customization of A constants. METHOD: A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom. RESULTS: A biometrist was interviewed in 94 of the 178 United Kingdom Ophthalmology departments. Compared with 2 years ago, nurses alone perform biometry more frequently (67 vs 51%) and junior doctors less frequently (9 vs 15%). More biometrists now attend external training courses (45 vs 37%). The Royal College of Ophthalmologists recommended intraocular lens calculation formulae (SRK-T, Hoffer Q, and Holladay) are used more commonly (30 and 15%) and audit of prediction error is being performed more frequently (78 vs 71%). The routine use of a partial coherence laser interferometry has increased from 35 to 61% in United Kingdom Ophthalmology departments. Currently, only one United Kingdom department is routinely using immersion ultrasound biometry. 'A' constants are customized in 47% of departments. CONCLUSION: Over the last 2 years, there has been improved implementation of the Royal College of Ophthalmologists guidelines on biometry. It is essential that the Royal College of Ophthalmologists guidelines are updated to include current best practice of routine use of partial coherence laser interferometry or immersion biometry and customization of A constants. A benchmark standard of 85-90% of patients achieving a final postoperative refraction within 1 dioptre of the predicted should be established.

Biometry↗
PubMed2006

Scleral-fixated posterior chamber intraocular lenses in non-vitrectomized eyes.

OBJECTIVE: To assess the long-term outcome of scleral-fixated sutured posterior chamber intraocular lens (SPCIOL) implantation in non pars plana vitrectomised eyes (1) to evaluate the long-term visual outcome, (2) to identify preoperative risk factors for poor visual outcomes, and (3) to identify the incidence of vitreoretinal complications. METHOD: A retrospective review of 65 eyes, which had not undergone pars plana vitrectomy prior to scleral-fixated SPCIOL implantation. RESULTS: In all, 65 eyes of 61 patients were analysed. The median follow-up period was 16 months (range 1-68 months). At final follow-up, 43 (66%) eyes had unchanged or improved BCVA at final follow-up. A total of 20 (31%) eyes had at least a two line improvement and eight (12%) eyes had at least a two line deterioration in final BCVA. No significant preoperative risk factors for a poor visual outcome were identified. In all, 24 eyes (37%) had per- and postoperative adverse events. These eyes were significantly more likely to have a poor visual outcome. Three eyes (4.6%) had a retinal detachment in the postoperative period, all of which had no perception of light at final follow-up. CONCLUSIONS: This study confirmed that while scleral-fixated SPCIOL intraocular lens implantation might be beneficial, there is a significant risk of per- and postoperative complications leading to loss of best-corrected vision in some eyes.

Adolescent↗
PubMed2005

Pilot National Electronic Cataract Surgery Survey: I. Method, descriptive, and process features.

AIM: The primary aim of this large pilot survey was to demonstrate the use and benefits of electronic data collection with respect to rapidly monitoring the access, delivery, and outcome of cataract surgery in the NHS and to update benchmark standards for these parameters of care. METHOD: Eight NHS departments that currently use specialty-specific electronic clinical systems or Electronic Patient Records (EPR) to collect a minimum preoperative, operative, and anaesthetic data set for cataract surgery agreed to pool their data. RESULTS: A total of 162 surgeons from 50 consultant teams and eight NHS Trusts agreed to submit their data on a total of 16,541 operations for age-related cataract. This report describes the age, sex, and ethnic profiles of the patients, waiting time for surgery, ocular copathology causing a reason for a guarded visual prognosis, visual impairment on admission, visual acuity in the operated eye, and the characteristics of the anaesthetic and surgical procedures. CONCLUSIONS: This survey has raised the benchmark standards established by the last National Survey in 1997. There has been a near universal switch to day case, phacosurgery under local anaesthesia (all used in > or =99.1% of cases compared with 70, 77, and 86%, respectively in 1997). The visual impairment in the operated eye is lower with 45% having 6 / 12 or better compared with 27% in 1997. Waiting times and visual impairment in the fellow eye have probably improved although data collection for these variables was incomplete. All departments require specialty-specific clinical systems to efficiently collect and analyse these data and this survey proves their potential to form the basis for national electronic surveys in the future.

Aged↗
PubMed2004

National biometry audit.

PURPOSE: To determine compliance with the Royal College of Ophthalmologists' (RCOphth) biometry guidelines. METHOD: A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom (UK). RESULTS: A biometrist was interviewed in 107 of the UK's 178 eye departments. Nurses alone run the biometry service in 58% of departments, orthoptists alone in 13%, junior doctors alone in 6%, optometrists alone in 3%, and a combination of staff in 20%. Of the staff interviewed, 37% had been on external biometry training courses. One intraocular lens (IOL) calculation formula was used for all eyes in 61% of departments with 17% using the obsolete SRK II formula, 36% of departments used two or more formulae and only 4% adhered to the RCOphth guidelines to use Hoffer Q in eyes with axial lengths <22.0 mm, an average of all three formulae in eyes between 22.0 and 24.5 mm, Holladay in eyes between 24.6 and 26.0 mm, and SRK/T in eyes >26.0 mm. Audit of refractive results was claimed by 71% of units but in only 17 (16%) did the biometrist know the percentage of eyes with a prediction error <or=1 D. CONCLUSION: This study demonstrates poor awareness and/or implementation of the RCOphth biometry guidelines and indicates that audits are either not highlighting poor results or are not resulting in a change in practice. The guidelines should be updated to emphasise the importance of customising A constants and to set benchmark standards for prediction error.

Biometry↗
PubMed2001

Pars plana vitrectomy and sutured posterior chamber lens implantation.

Transcleral suturing of posterior chamber intraocular lenses (IOLs) was developed to extend the benefits of IOL visual rehabilitation to eyes lacking capsular support and to avoid the complications of closed loop interior chamber IOLs. Although most frequently implanted after complicated cataract surgery or penetrating keratoplasty, they are indicated in several situations following pars plana vitrectomy. The surgical techniques have evolved to minimize the risk of complications, but the surgery remains technically more demanding and time-consuming than insertion of a modern open loop anterior chamber IOL. No randomized trials have compared the relative risks of each lens type, which leaves surgeon preference as the major determinant of what lens is implanted. It is likely, however, that in eyes with extensive anterior chamber angle damage or large iris defects, sutured posterior chamber IOLs will remain the first choice for surgical rehabilitation.

Humans↗
PubMed2000

Combined pars plana vitrectomy and sutured posterior chamber implant.

OBJECTIVE: To describe the surgical technique, visual acuity results, and complications of sutured posterior chamber intraocular lenses with complete pars plana vitrectomy. METHOD: A retrospective review of 63 eyes was combined with a telephone survey of the patients and their ophthalmologists. RESULTS: The preoperative diagnoses were trauma, 25 eyes; ectopia lentis, 24 eyes; aphakia following retinal detachment surgery, 7 eyes; cataract surgery, 6 eyes; and endophthalmitis, 1 eye. Mean follow-up was 20 months. Preoperative best-corrected visual acuity was 20/40 or better in 36% (23 of 63 eyes), 20/60 to 20/120 in 33% (21 of 63 eyes), and 20/200 or worse in 31% (19 of 63 eyes) improving to 20/40 or better in 76% (48 of 63 eyes), 20/60 to 20/120 in 18% (11 of 63 eyes), and 20/200 or worse in 6% (4 of 63 eyes) at final follow-up. Preoperative complications included iatrogenic retinal breaks in 3 cases, difficulty with a fixation suture in 1 case, and mild vitreous hemorrhage in 1 case. Postoperative complications included retinal detachment in 2 cases, choroidal hemorrhage in 1 case, intermittent pupil capture in 9 cases, self-limiting vitreous hemorrhage in 3 cases, and late intraocular lenses dislocation in 1 case. CONCLUSIONS: Suturing a posterior chamber implant concurrently, or following, a complete pars plana vitrectomy is a safe procedure. Complete vitrectomy may reduce the rate of long-term complications. Optimal visual rehabilitation can be achieved without the need for contact lens wear with an acceptable additional risk of surgical complications. Arch Ophthalmol. 2000;118:905-910

Adolescent↗
PubMed1999

Dominant optic atrophy. Refining the clinical diagnostic criteria in light of genetic linkage studies.

OBJECTIVE: To describe the clinical findings and refine the clinical diagnostic criteria for dominant optic atrophy based on eight British families in which the diagnosis was confirmed by linkage analysis. DESIGN AND PARTICIPANTS: Case series; 92 subjects in 8 pedigrees had both eyes examined. INTERVENTION: Family members received a domiciliary examination based on best-corrected visual acuity, color vision using Ishihara and Hardy Richter Rand (HRR) plates, confrontation field testing using a red target, and optic disc evaluation using a direct ophthalmoscope. Genomic DNA was extracted from leukocytes or buccal mucosal cells and genotyped using 12 fluorescently labeled microsatellite markers from the region 3q27-q29. MAIN OUTCOME MEASURES: Subjects were classified clinically as definitely or possibly affected on the basis of the domiciliary examination before genetic analysis, and these results were compared with the haplotype analysis. RESULTS: Clinically, 43 subjects were identified as definitely affected, 4 as possibly affected, and 45 as unaffected. Visual acuity in affected subjects ranged from 6/6 to count fingers and declined with age. On genetic analysis, a haplotype was identified in each family, which was found in all definitely affected members but not in those regarded as unaffected. The four possibly affected individuals also bore the haplotype that segregated with the disease. CONCLUSIONS: Simple clinical tests are highly efficacious in diagnosing dominant optic atrophy. Contrary to accepted criteria, symptoms begin before the age of 10 years in only 58% of affected individuals. Visual acuity in affected subjects is highly variable. A mild degree of temporal or diffuse pallor of the optic disc and minimal color vision defects, in the context of a family with dominant optic atrophy, are highly suggestive of an individual being affected, even if the visual acuity is normal. This widens the generally accepted diagnostic criteria for this disease.

Adolescent↗
PubMed1999

In vitro protein adsorption to 2 intraocular lens materials.

PURPOSE: To study in vitro protein adsorption to poly(methyl methacrylate) (PMMA) and foldable AcrySof intraocular lenses (IOLs). SETTING: Department of Ophthalmology, United Medical and Dental Schools of Guy's and St. Thomas' Hospitals, London, United Kingdom. METHODS: Poly(methyl methacrylate) (Alcon Surgical, model MC60BM) and AcrySof (Alcon Surgical, model MA60BM) IOLs were incubated in physiological concentrations of radiolabeled albumin or fibronectin at 37 degrees C for periods between 5 minutes and 1 week. The IOLs were removed and rinsed in buffered saline, and the amount of adsorbed protein was calculated by measuring the radioactivity with scintillation spectrometry. RESULTS: The adsorption of both proteins occurred rapidly over the first 2 hours; the rate of adsorption was concentration dependent. Quantitative differences were found: PMMA lenses bound significantly greater quantities of albumin. Initial fibronectin adsorption to both materials was similar, but increased adsorption to AcrySof IOLs was found at days 1 and 7. CONCLUSIONS: The differences in protein absorption to PMMA and AcrySof IOLs in vitro may contribute to the differences in the biological response to these IOLs, including the lower rates of posterior capsule opacification associated with acrylic lenses.

Acrylic Resins↗
PubMed1998

Topical versus peribulbar anesthesia, without sedation, for clear corneal phacoemulsification.

PURPOSE: To investigate patient and surgeon acceptance of topical anesthesia as an alternative to peribulbar anesthesia for clear corneal phacoemulsification. SETTING: Department of Ophthalmology, Whipps Cross Hospital, London, England. METHODS: All cataract surgery was performed using a temporal clear corneal approach, bimanual phacoemulsification, and in-the-bag intraocular lens implantation. The results of 51 patients having surgery under topical anesthesia (amethocaine) were compared with those of 30 patients having peribulbar anesthesia (50:50 mixture of lignocaine 2% and bupivacaine 0.5% with hyaluronidase). No sedation was used in either group. Pain perception on administration of the anesthetic, perioperatively (period immediately surrounding and during surgery), and postoperatively was assessed using a visual analog scale from 0 to 10 (0 = no pain: 10 = worst pain imaginable). A questionnaire was used to assess the degree of patient and surgeon satisfaction. RESULTS: Administration of topical amethocaine was significantly less painful than peribulbar bupivacaine (P = .03). Perioperative pain showed a trend toward being worse in the topical anesthesia group but did not reach statistical significance. There was no difference in the postoperative pain scores of the two groups. The surgical experience was rated very satisfactory by 67% in the topical group and 73% in the peribulbar group. The surgeons reported no difficulties or complications. CONCLUSION: Topical anesthesia was safe and effective for clear corneal phacoemulsification and was well tolerated by patients. The slightly greater awareness of ocular discomfort in the topical group perioperatively did not alter patient satisfaction with the surgical experience when compared with the peribulbar group.

Aged↗
PubMed1997

Dominant optic atrophy, Kjer type. Linkage analysis and clinical features in a large British pedigree.

OBJECTIVES: To perform DNA linkage studies in an extensive 5-generation British pedigree with dominant optic atrophy and to validate the efficacy of domiciliary screening for affected members. METHODS: Family members received a domiciliary examination based on corrected visual acuity, color vision, visual field defects, and optic disc appearance; DNA linkage analysis was performed using 7 microsatellite markers on 3q27-qter. RESULTS: Based on the results of the ophthalmic examination, 15 members could be classified as definitely affected, 1 probably affected, and 25 unaffected. Two-point linkage analysis gave significant maximum lod scores at theta [corrected] = 0.00, with the markers D3S3669, D3S3590, and D3S3642. A haplotype segregating with the disease was identified in affected individuals, including the probably affected subject. Informative meioses defined the disease interval between markers D3S1601 and D3S1265. CONCLUSIONS: Domiciliary screening was effective in identifying all 16 affected members of a British family with dominant optic atrophy. The typical clinical features were present. The location of the OPA1 gene in this new British family seems to be in the 3q27-28 region and is the same as that reported in Danish, Cuban, and French families, suggesting no genetic heterogeneity in this disorder.

Adult↗
PubMed1997

Linkage studies in dominant optic atrophy, Kjer type: possible evidence for heterogeneity.

Dominant optic atrophy, Kjer type, is an autosomal dominant disorder causing progressive loss of visual acuity and colour vision from early childhood. The gene (OPA1) has variable expressivity, a penetrance of 0.98, and the locus has been localised to 3q28-29. We have genotyped nine British families with the disease using 12 polymorphic microsatellite markers from this region. Linkage and haplotype analysis shows the OPA1 gene to be located in a 2.3 cM interval between markers D3S1601 and D3S2748. One family showed no evidence of linkage with the chromosome 3 markers, suggesting for the first time that locus heterogeneity for this disease may exist, although exclusion for linkage is based on unaffected subjects. In addition, analysis of recombinants has enabled us to order the 12 markers along chromosome 3.

Adolescent↗
PubMed1994

Co-management of cataract postoperative care.

Cataract extraction is a common ophthalmic surgical procedure. Many, if not most, patients will require it at some point in their lives. Cataract postoperative care is now routinely co-managed by many optometrists and ophthalmic surgeons. Postoperative management of the cataract patient in the optometrist's office is beneficial to the patient, and allows involved providers to practice to the full extent of their training and expertise. This paper sets forth a clinical perspective on co-management of cataract postoperative care. Included are suggested protocols for examination intervals and examination components, as well as expected clinical findings and potential complications.

Cataract↗
PubMed1990

The posterior uveal bleeding syndrome.

Eight patients were observed who suffered varying degrees of visual loss secondary to multiple recurrent hemorrhages or serous fluid beneath the retinal pigment epithelium and neurosensory retina in the posterior fundus. Vitreous hemorrhage occurred in two patients. In all patients, hemorrhages or exudates were associated with orange subretinal lesions of which the clinical and fluorescein angiographic appearances were not previously familiar to the authors. Six of the eight patients were female, and all but one was black. Ages ranged from 40 to 79 years (median, 57 years). Final visual acuities ranged from 20/40 to hand motions. The term "posterior uveal bleeding syndrome" is proposed to describe these findings.

Adult↗
PubMed1988

Cataract removal.

Explore the source record for details and available documents.

Cataract Extraction↗
PubMed1988

Presumed ocular histoplasmosis syndrome.

Presumed ocular histoplasmosis syndrome (POHS) is a commonly observed fungal infection. Ocular findings include peripapillary atrophy, peripheral punched-out lesions, and a macular subretinal neovascular membrane. Laser photocoagulation can be beneficial in reducing visual loss from macular scarring due to subretinal neovascular membranes. Herein we describe a patient with POHS in which laser treatment regressed a parafoveal subretinal neovascular membrane. Her vision improved from 20/70 to 20/20 in the treated eye.

Adult↗