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M P Snead

Publications and source records attributed to M P Snead.

At least 19 recordsLinked to original sources
PubMed2006

Scleral buckling combined with vitrectomy for the management of rhegmatogenous retinal detachment associated with inferior retinal breaks.

AIM: The use of adjunctive scleral buckling during vitrectomy for retinal detachment associated with inferior breaks has been the recent focus of some debate. It has been suggested that any benefit might be outweighed by potential complications associated with buckling surgery. The purpose of this study was to compare the success rate of vitrectomy, gas, and supplementary scleral buckling with the results of two recently published case series suggesting that acceptable results in inferior break detachments can be achieved with vitrectomy and gas alone. METHODS: A retrospective analysis of 60 consecutive patients with inferior break retinal detachments was conducted. All patients underwent vitrectomy, gas, and scleral buckling. In all cases, fellow eyes were examined under anaesthesia for retinal breaks if posterior vitreous detachment (PVD) had occurred at the time of presentation. Demographics, preoperative, and postoperative complications and outcome were recorded. RESULTS: Primary retinal attachment at 3 months was achieved in 95% of patients. This exceeds success rates of published data of patients who underwent vitrectomy and gas without buckling (81-89%). In patients with PVD in the fellow eye, 53% had horseshoe tears and all were treated with cryopexy. No sight-threatening complications occurred, but five patients developed minor buckle-related complications postoperatively. CONCLUSION: Supplementary scleral buckling is a safe procedure that improves and enhances primary success rates in inferior break detachments over vitrectomy and gas without buckling. There is a high rate of PVD-related breaks requiring treatment in the fellow eyes.

Female↗
PubMed2006

A rationale for membrane peeling in the repair of stage 4 macular holes.

AIM: To examine the histological and immunocytochemical characteristics of epiretinal membranes (ERM) associated with stage 4 macular holes (MH) so as to establish a vitreoretinal rationale for surgery in stage 4 MH. METHOD: Consecutive patients with stage 4 MH undergoing vitrectomy and membrane peeling were recruited. Preoperatively, the eyes were examined for ERM formation over the macula and completeness of posterior hyaloid membrane (PHM) separation from the retina. ERM peel specimens obtained during surgery were sent for histological and immunocytochemical studies and were compared with the PHM specimens taken from a previous post-mortem study of eyes with physiological posterior vitreous detachment but without macular holes. RESULT: A total of 13 patients with stage 4 MH fulfilled the inclusion criteria and were recruited. Preoperatively, all eyes had an ERM over the macula and incomplete separation of the PHM seen as a defect in the PHM on specular biomicroscopy. Histologically, the ERM specimens had very similar morphological characteristics to PHM, consisting of an eosinophilic membrane of varying thickness with scattered spindle-shaped cells. The membranes stained positively for type IV collagen while the cells were glial fibrillary acidic protein positive. Postoperatively, successful closure of MH was achieved in all cases. CONCLUSION: Stage 4 MH is characterised by incomplete separation of the PHM from the retina with remnants overlying the macula manifesting as ERM. Removal of the ERM is required during vitrectomy in order to relieve the tangential forces involved in the development of MH.

Aged↗
PubMed2005

Type 1 Stickler syndrome: a histological and ultrastructural study of an untreated globe.

AIMS: To present a histological and ultrastructural study of an untreated globe in a patient with genetically confirmed type 1 Stickler syndrome. METHODS: Histological and electron microscopic examinations were performed on the enucleated globe from the proband of a pedigree with type 1 Stickler syndrome. Linkage analysis was carried out using polymorphic markers flanking the COL2A1 gene and the mutation was identified by direct sequencing. RESULTS: The significant retinal abnormality was incarceration of vitreous collagen within glial strands on the inner surface of an atrophic and gliotic detached retina. The incarcerated collagenous layers contained glial cells and extended from the retina to form strands, some of which contributed to a retrolental membrane. Mutation screening detected a C to T mutation in exon 47 that inserted a premature termination codon into the reading frame of the mRNA. Sequence analysis of three of the four affected children confirmed that they were also heterozygous for the base change. The youngest child's DNA was not analysed. CONCLUSIONS: The study represents the first evidence of abnormal interactions between pathological vitreous collagen and the inner retina in a patient with type 1 Stickler syndrome with a confirmed mutation in the COL2A1 gene.

Adult↗
PubMed2005

Clinical features and surgical management of retinal detachment secondary to round retinal holes.

AIMS: The majority of rhegmatogenous retinal detachments result from pathological posterior vitreous detachment (PVD) and secondary horseshoe or giant retinal tears. Retinal detachment without PVD is usually associated with either retinal dialysis or round retinal holes. This study characterises the features, surgical outcome, and incidence of bilateral involvement of detachment associated with round retinal holes. METHODS: In all, 110 retinal detachments from 96 consecutive patients with retinal detachment secondary to round retinal holes were studied. Analysis of patient age, sex, refraction, preoperative visual acuity, presented symptoms, position and extent of detachment, number and distribution of holes present, posterior hyaloid membrane status, surgical management, outcome of surgery, and postoperative visual acuity were studied. RESULTS: The mean age for patients was 34 years with a marked female preponderance (64%) and myopia (83%). The posterior hyaloid membrane remained attached in 95 eyes (86%). In all, 45% patients had bilateral pathology, of which 33% had 'mirror image' distribution. Detachments were predominantly shallow (93%) and slow in progression (17%). A total of 100 detachments were repaired with cryotherapy and scleral buckling, eight with cryotherapy alone, and one with laser retinopexy. In all, 99% detachments were successfully reattached with a single procedure. The mean follow-up period was 2 years. There were no instances of redetachment. CONCLUSIONS: Round hole detachments are slowly evolving detachments with attached vitreous gel in young, predominantly female myopes. Examination of the fellow eye should be mandatory as there is a high incidence of bilateral pathology. Scleral buckling procedures remained highly effective in this selected group of patients.

Adolescent↗
PubMed2004

Hyperconvolution of the inner limiting membrane in vitreomaculopathies.

BACKGROUND: This study investigates the similarities and differences between epiretinal membranes in four clinically distinct types of vitreomaculopathy. We propose a hypothesis on the origin of the predominant cell type and its potential role in causing these conditions. METHODS: Epiretinal membranes (ERMs) surgically removed from a prospective, consecutive series of vitrectomies for macular pucker associated with an untreated peripheral horseshoe tear (MP), cellophane maculopathy (CM), stage 4 macular hole (MH) and vitreomacular traction syndrome (VMT) were examined by light microscopy and by immunocytochemistry (ICC) using antibodies marking type IV collagen, type II collagen, glial fibrillary acidic protein (GFAP), and low- and high-molecular-weight cytokeratin (MNF116). These specimens were compared with post-mortem control eyes with and without physiological posterior vitreous detachment (PVD). Light microscopy was carried out on 5-microm-thick sections cut from formalin-fixed, paraffin-embedded tissue blocks. Appropriate autoclave or enzyme pre-digestion steps were deployed to retrieve antigens for ICC. No patient had undergone previous vitreoretinal surgery or peripheral retinopexy. RESULTS: From a series of 38 patients, (13 CM, 8 MP, 16 MH and 1 VMT) a total of 20 specimens contained sufficient tissue for histology and immunocytochemistry. All specimens contained portions of inner limiting membrane (ILM) coated by GFAP-positive cells. Specimens from patients with MP and CM exhibited hyperconvolution of the ILM, which was not found in the specimens from patients with MH or VMT or in the control eyes. Hyperconvolution was associated with increased glial cell density, GFAP staining intensity and duplication of ILM basement membrane. Three cases of ERMs from the MP group contained, in addition, cytokeratin-positive cells. In the control group; post-mortem eyes with PVDs showed patchy staining of the posterior hyaloid membrane for GFAP and type 4 collagen. Post-mortem eyes with attached gel showed weak positivity of the ILM for type 4 collagen, and a monolayer of GFAP-positive cells lined the vitreous aspect of the ILM. CONCLUSIONS: These results indicate that glial cells are fundamentally important in the formation of ERMs found in this group of vitreomaculopathies. The hyperconvolution and duplication of the ILM in CM and MP were striking and distinctive features and suggest a mechanism by which these membranes exert tractional forces on the retina. Post-mortem control eyes contained a similar (but more dispersed) population of GFAP-positive cells in the region of the ILM, suggesting the primary aetiology for CM and MP may originate within the ILM. ERMs from MP cases may, in addition, contain cytokeratin-positive cells, of probable RPE origin.

Basement Membrane↗
PubMed2004

Intraocular surgery for optic nerve disorders.

This article discusses two current indications for intraocular surgery for optic nerve conditions. The first topic is macular detachment in association with congenital optic disc pit, and includes a review of the theories of pathogenesis and management options including our own experience of treatment with vitrectomy and gas tamponade. In addition, the histopathological findings of a new case of optic disc pit with serous macular detachment are presented, adding to the rare examples previously reported. The second subject is a radial optic neurotomy, a recently advocated treatment for central retinal vein occlusion, which, despite its controversial nature, is gaining in popularity.

Adolescent↗
PubMed2002

Molecular genetics of rhegmatogenous retinal detachment.

Rhegmatogenous retinal detachment (RRD) most commonly occurs as a spontaneous event resulting from posterior vitreous detachment, typically between the ages of 40-70 yrs. It is also a feature in some inherited disorders, most commonly Stickler syndrome. The relationship between these inherited disorders and the spontaneous cases is unclear. Here in particular we review Stickler syndrome, and discuss the differential diagnosis of Stickler, Wagner and Marshall syndromes. Other rare inherited disorders associated with RRD are also briefly reviewed.

Adult↗
PubMed2002

Clinical, histological and ultrastructural studies of the posterior hyaloid membrane.

AIMS: To investigate the histological, immunohistochemical and ultrastructural features of the posterior hyaloid membrane (PHM) in its naturally separated state in patients without previous surgery and slit-lamp documentation of antemortem posterior vitreous detachment (PVD). METHODS: A prospective study was commenced in 1992 to recruit patients with physiological PVD from an unselected group of general medical inpatients and ascertain the prevalence of PVD. Postmortem specimens subsequently available were studied to analyse the clinicopathological correlation and processed using standard techniques for histology, immunohistochemistry and electron microscopy. RESULTS: Eighty-five patients were examined with ages ranging from 68 to 98 yrs (mean 83.4 yrs). The posterior hyaloid membrane had clearly separated from the retina in 66% of eyes. Twenty-nine eyes from 15 patients were subsequently studied pathologically. The posterior hyaloid membrane exhibited a uniform cellular component, most densely populated around the Weiss' ring. The cells were characterised by oval or round nuclei, indistinct cytoplasm and were only seen within, or abutting, the weakly eosinophilic posterior hyaloid membrane. The posterior aspect of the posterior hyaloid membrane showed a convoluted appearance staining lightly with haematoxylin and eosin. The detached posterior hyaloid membrane exhibited focal positivity for GFAP and type IV collagen. Electron microscopy demonstrates both fibres and basement membrane associated with the cellular component including hemi-desmosome attachment plaques between the cells and basement membrane. CONCLUSIONS: This study illustrates some of the structural differences between the posterior hyaloid membrane and the cortical vitreous gel it envelopes and demonstrates the presence of cells intimately associated with the posterior hyaloid membrane in its naturally separated state. We propose the cellular population integral to the PHM to be designated as laminocytes in order to emphasise their type IV collagen/basement membrane association and planar array within the membrane which separates at posterior vitreous detachment.

Aged↗
PubMed2002

National audit of the outcome of primary surgery for rhegmatogenous retinal detachment. I. Sample and methods.

PURPOSE: This national study was designed to audit anatomical outcome and complications relating to primary surgery for rhegmatogenous retinal detachments. This paper presents survey methods, characteristics of participating consultants and the demographic and clinical characteristics of the patient sample. METHODS: Two surveys were undertaken. The first identified consultants who at the time performed retinal detachment surgery in the National Health Service. These surgeons formed the sampling frame for a nationwide cross-sectional clinical study that audited the outcomes of primary surgery for rhegmatogenous retinal detachments. Consultants selected patients according to the study eligibility criteria and data were collected by self-administered postal questionnaires. A validation exercise was carried out to examine selection bias and reporting accuracy. RESULTS: Only 256/671 (38%) of UK consultants, who responded to the first survey, indicated that they performed retinal detachment surgery on NHS patients. Annual activity varied between 0 and 400 primary procedures for rhegmatogenous retinal detachments. Seven hundred and sixty-eight eligible patients from 167 consultants were recruited for the clinical study. Twenty per cent of patients had a single retinal break with less than one quadrant of associated detachment and 45% had single or multiple breaks within the same quadrant and/or less than two quadrants of associated retinal detachment. Over 50% patients had single or multiple horseshoe tears. Validation studies suggested that there was no significant bias from the selection of patients or inaccuracy in reporting outcomes. CONCLUSIONS: This large unselected group of primary rhegmatogenous retinal detachments provides a representative sample for considering variations in re-attachment rates.

Adolescent↗
PubMed2002

National audit of the outcome of primary surgery for rhegmatogenous retinal detachment. II. Clinical outcomes.

PURPOSE: This national study was designed to audit anatomical outcome and complications relating to primary surgery for rhegmatogenous retinal detachments. This paper presents success and complication rates, and examines variations in outcome. METHODS: Sampling and recruitment details of this nationwide cross-sectional survey of 768 patients of 167 consultant ophthalmologists having their first operation for rhegmatogenous retinal detachment have been described. The main clinical outcomes detailed here are anatomical reattachment at 3 months after surgery and complications related to surgery. Consultants with a declared special interest in retinal surgery and able to perform pars plana vitrectomy were designated specialists for the analyses. RESULTS: Overall reattachment rate with a single procedure was 77% (95% CI 73.9-80.2). There were significant differences in reattachment rates between specialists and non-specialists. Without allowing for case-mix, specialists had a reattachment rate of 82% (95% CI 77.9-85.7) with a single procedure and non-specialists 71% (95% CI 65.9-76.0). Allowing for case-mix, there was a significant difference between specialists and non-specialists for grade 2 detachments of 87% and 70% respectively (P < 0.0001). Analysing detachments by break type, the largest difference between specialists and non-specialists was observed for retinal detachments secondary to horseshoe tears, 80% and 68% respectively (P < 0.003). Specialists met the standards set for primary reattachment rates, while non-specialists did not. Over a third of patients had at least one complication reported at some point during the audit period. CONCLUSIONS: Significant differences were seen in reattachment rates between specialists and non-specialists, overall and for specific subgroups of patients. This study provides relevant, robust and valid standards to enable all surgeons to audit their own surgical outcomes for primary retinal detachment repair in rhegmatogenous retinal detachments, identify common categories of failure and aim to improve results.

Adolescent↗
PubMed2002

Vitreoretinopathy with phalangeal epiphyseal dysplasia, a type II collagenopathy resulting from a novel mutation in the C-propeptide region of the molecule.

A large family with dominantly inherited rhegmatogenous retinal detachment, premature arthropathy, and development of phalangeal epiphyseal dysplasia, resulting in brachydactyly was linked to COL2A1, the gene encoding proalpha1(II) collagen. Mutational analysis of the gene by exon sequencing identified a novel mutation in the C-propeptide region of the molecule. The glycine to aspartic acid change occurred in a region that is highly conserved in all fibrillar collagen molecules. The resulting phenotype does not fit easily into pre-existing subgroups of the type II collagenopathies, which includes spondyloepiphyseal dysplasia, and the Kniest, Strudwick, and Stickler dysplasias.

Adult↗
PubMed2001

Pupil block glaucoma in phakic and pseudophakic patients after vitrectomy with silicone oil injection.

PURPOSE: To describe pupil block glaucoma in phakic and pseudophakic patients after vitrectomy with silicone oil injection. DESIGN: Interventional case series. METHODS: Cases were collected from January 1997 to July 2000 from three tertiary referral centers. RESULTS: Seven phakic patients (seven eyes) and one pseudophakic patient (one eye) presented 1 to 90 days after vitrectomy and silicone oil injection with intraocular pressures of 36 to 70 mm Hg. Five patients had an observed or potential weakness of the iris-lens diaphragm. Treatment with Nd:YAG-laser peripheral iridotomy or inferior iridectomy provided a temporary reduction in intraocular pressure for some patients, but all eventually required removal of silicone oil. CONCLUSION: Pupil block glaucoma after silicone oil injection is well recognized in aphakic patients, but ophthalmologists should be aware that it can occur in phakic and pseudophakic patients, particularly in complicated cases and patients with a weakness of the iris-lens diaphragm.

Adult↗