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Biomedical subjects

G A Lee

Publications and source records attributed to G A Lee.

At least 19 recordsLinked to original sources
PubMed2006

Pig eye trabeculectomy-a wet-lab teaching model.

PURPOSE: A teaching model for trabeculectomy is described using pig eyes prepared in formalin. METHOD: The model enables trainee surgeons to practice various aspects of tissue handling required for successful trabeculectomy including the construction of a fornix-based conjunctival flap, scleral flap with buried releasable sutures, and water-tight conjunctival closure. RESULTS: Exposure to the necessary skills required to perform trabeculectomy surgery can be improved by the use of wet laboratory practice. CONCLUSIONS: Trabeculectomy surgery experience is becoming more limited as fewer procedures are being performed due to the efficacy of recent medications. Wet laboratories will become an increasingly important aspect of a comprehensive ophthalmology training programme.

Animals↗
PubMed2005

Trabeculectomy: a training dilemma.

AIM/PURPOSE: The incidence of trabeculectomy is falling due to more effective medical therapies, resulting in fewer trabeculectomy operations carried out by Ophthalmology trainees. This study audits all primary trabeculectomy procedures performed publicly at the two major teaching hospitals in Brisbane, Australia. METHOD: A retrospective consecutive case review analysing the rates and outcomes of Ophthalmology trainee versus consultant trabeculectomies that were performed during the period May 1996-May 2002. RESULTS: In all, 290 primary trabeculectomies were undertaken during the study period. Ophthalmology trainees performed 95 (33%) of the procedures. This represents a rate of 1.6 trabeculectomy procedures per year per trainee (10 trainees train at the two hospitals per year). Rates of complications postoperatively were similar between the trainee and consultant groups. The percentage of patients achieving an IOP < or =15 mmHg on no medication at their last follow-up was low at 30%. CONCLUSIONS: The results of this study suggests that improvement in trabeculectomy technique is required. In order to acquire skills, wetlab training on artificial or animal eyes may become mandatory within the training programmes, otherwise trabeculectomy will become the realm of sub-specialists with glaucoma fellowship training.

Adult↗
PubMed2003

Effects of lamellar keratotomy on postkeratoplasty astigmatism.

AIM: To determine the changes in postkeratoplasty astigmatism induced by lamellar keratotomy. METHODS: A prospective, non-randomised comparative trial of patients undergoing a hinged lamellar corneal flap for treatment of significant astigmatism after penetrating keratoplasty. Uncorrected visual acuity, best corrected visual acuity, refraction, and corneal topography were assessed at 1 and 3 months after the lamellar keratotomy. RESULTS: 17 eyes in 16 patients (13 M, 3F) were included in the study (mean age 48.2 years; range 20-86 years). Six of 17 eyes (35.3%) changed more than 1 dioptre (D) in spherical equivalent by 3 months. Nine of 17 eyes (52.9%) changed more than 1 D in sphere by 3 months. 12 of 17 eyes (70.6%) changed more than 1 D in refractive cylinder. Seven patients of 15 (46.7%) changed more than 1 D in corneal power as measured topographically. Five of 17 eyes (29.4%) changed in refractive cylinder axis more than 15 degrees and this was similar to the change measured topographically of four of 15 eyes (26.7%). Vector analysis showed 60% of eyes had a surgically induced astigmatism (SIA) vector of more than 1 D, including a net corneal astigmatism decrease of more than 1 D in four eyes and increase of more than 1 D in two eyes at 3 months after surgery. Complications of the lamellar keratotomy included two partial buttonholes and one partial wound dehiscence. CONCLUSIONS: The creation of a lamellar flap alone can have significant effects on the astigmatism following penetrating keratoplasty. LASIK for correction of postkeratoplasty astigmatism may be more accurately performed as a two stage procedure rather than a single stage, after the corneal effects of the lamellar keratotomy have stabilised.

Adult↗
PubMed2001

Cyclodiode photocoagulation for refractory glaucoma after penetrating keratoplasty.

OBJECTIVE: This study analyzes the results of intraocular pressure (IOP) reduction by contact diode cycloablation (cyclodiode) in cases of refractory glaucoma after penetrating keratoplasty. DESIGN: Retrospective noncomparative, interventional case series. PARTICIPANTS: Twenty-eight eyes in 28 patients attending the Moorfields Eye Hospital. INTERVENTION: Cyclodiode (40 applications x 1.5 W x 1.5 seconds over 270-300 degrees ) was used to control the IOP in refractory glaucoma after penetrating keratoplasty. MAIN OUTCOME MEASURES: Postoperative IOP, graft status, visual acuity, and number of antiglaucoma medications were recorded after cyclodiode treatment. RESULTS: Cyclodiode resulted in a reduction of IOP from a median of 33 mmHg (interquartile range [28, 40.5]) to a median of 15 mmHg (interquartile range [12, 20.5]). Most patients had a significant lowering in IOP with a median reduction of 16 mmHg (interquartile range [12, 25]; P < 0.0001). IOPs of 6 to 21 mmHg were achieved in 22 patients (79%). Sixteen patients (57%) required more than one treatment with cyclodiode to control the IOP, with three patients (11%) requiring three treatments and two patients (7%) requiring four treatments. Visual acuity improved (> two Snellen lines of acuity) in three patients (11%) and remained the same (+/- one Snellen line) in 17 patients (61%). The mean number of antiglaucoma medications before cycloablation was 2.6 and was 1.8 after treatment (P < 0.001). Of the 19 patients (68%) with originally clear grafts, three grafts (16%) developed opacification. One patient (4%), with a history of nanophthalmos and recurrent uveal effusion, had delayed hypotony (IOP < 6 mmHg) occurring 46 months after the diode treatment. All patients had at least 6 months follow-up. CONCLUSIONS: These patients have often undergone multiple previous complicated ocular interventions and are often not suitable for filtration surgery. Reduction of IOP with maintenance of visual acuity and a good safety profile was achieved in most patients in this study but may require multiple treatments. We propose cyclodiode as an effective treatment for many patients in the management of refractory glaucoma after penetrating keratoplasty.

Adult↗
PubMed2001

Penetrating keratoplasty for silicone oil keratopathy.

PURPOSE: Penetrating keratoplasty for silicone oil keratopathy is associated with high risks and limited visual prognosis. This study examined the outcomes and factors influencing graft failure. METHODS: A retrospective, non-comparative, interventional case series of patients attending Moorfields Eye Hospital, London. RESULTS: A total of 24 penetrating keratoplasties were performed in 17 patients (13 men and four women) from 1991 to 2000. The mean age of patients undergoing surgery was 43.6 years (range 17-84 years, SD +/- 21.0). Silicone oil was removed before or during the time of initial penetrating keratoplasty in nine patients (52.9%) and left in situ in eight patients (47.1%). Ten out of 24 grafts survived (41.7%). The median duration of graft survival was 21 months (range 2 weeks-98 months) with median duration of follow up 33 months (range 2-100 months). At final follow up, the number of patients with a clear graft who had oil removed before or during the time of penetrating keratoplasty was seven out of 10 (70.0%). Risk factors for graft failure included hypotony, multiple keratoplasty, corneal neovascularization, rejection episode, silicone oil left in situ and postoperative glaucoma. CONCLUSIONS: Management of these complex patients requires a combined approach from anterior segment and vitreoretinal subspecialties. The long-term success of the graft can be improved if silicone oil is removed prior or during the time of penetrating keratoplasty.

Adolescent↗
PubMed2001

Calf muscle strength in humans.

In an effort to measure strength characteristics of the calf muscles, 18 subjects (14 male, 4 female, age =34.3+/-2.4yrs) were tested using a specially designed torque velocity device (TVD). This TVD is a hardware interface with the subject's lower leg which stabilizes the leg for calf muscle strength measurements. Calf muscle strength measurements consisted of 1) isometric force production at ankle angles of 80, 90, and 100 degrees of plantar flexion, 2) peak torque at six isokinetic angular velocities 0.52, 1.05, 2.09, 3.14, 4.19, and 5.24 rad x s(-1), and 3) a fatigue test consisting of 30 maximal contractions at 3.14 rad x s(-1). The greatest force production occurred at 80 degrees of ankle plantar flexion (148.5 +/- 40.2 Nm). Isokinetic force production ranged from 114.1 +/- 24.7 Nm at 0.52 rad x s(-1) to 16.8 +/- 6.5 Nm at 5.24 rad x s(-1). A fatigue test consisting of 30 maximal repetitions at 3.14 rad x s(-1) resulted in a 61 +/- 15% decline in force production. To assess reproducibility and day to day variation, measurements at 1.05 and 2.09 rad x s(-1) were made during five different trials in a single day and one trial per day for three days, respectively. The within subject coefficient of variation was 2.6 to 6.5% for reproducibility and 1.9 to 7.4% for day to day variation. Magnetic resonance imaging (MRI) of the lower limb and muscle biopsy specimens from the gastrocnemius (lateral head) and soleus muscles were obtained to examine the relationship between strength and morphological characteristics of the calf muscles. Cross-sectional area of the primary plantar flexors (gastrocnemius and soleus) was 47.9 +/- 1.3 cm2 while muscle volume was 642 +/- 16 cm3. Muscle fiber composition of the gastrocnemius and soleus averaged 57 +/- 2 and 85 +/- 3% type I fibers, respectively. A poor correlation was found between fiber type and maximal isometric force production (r =0.38; p>0.05). However, calf muscle strength and muscle size was positively correlated (r = 0.76; p < 0.05). These data indicate that using the TVD interface to stabilize the lower leg is a reliable and reproducible procedure for the measurement of calf muscle strength.

Adult↗
PubMed2001

Comparison of a space shuttle flight (STS-78) and bed rest on human muscle function.

The purpose of this investigation was to assess muscle fiber size, composition, and in vivo contractile characteristics of the calf muscle of four male crew members during a 17-day spaceflight (SF; Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission) and eight men during a 17-day bed rest (BR). The protocols and timelines of these two investigations were identical, therefore allowing for direct comparisons between SF and the BR. The subjects' age, height, and weight were 43 +/- 2 yr, 183 +/- 4 cm, and 86 +/- 3 kg for SF and 43 +/- 2 yr, 182 +/- 3 cm, and 82 +/- 4 kg for BR, respectively. Calf muscle strength was examined before SF and BR; on days 2, 8, and 12 during SF and BR; and on days 2 and 8 of recovery. Muscle biopsies were obtained before and within 3 h after SF (gastrocnemius and soleus) and BR (soleus) before reloading. Maximal isometric calf strength and the force-velocity characteristics were unchanged with SF or BR. Additionally, neither SF nor BR had any effect on fiber composition or fiber size of the calf muscles studied. In summary, no changes in calf muscle strength and morphology were observed after the 17-day SF and BR. Because muscle strength is lost during unloading, both during spaceflight and on the ground, these data suggest that the testing sequence employed during the SF and BR may have served as a resistance training countermeasure to attenuate whole muscle strength loss.

Adult↗
PubMed2000

Biomechanical comparison of five different atlantoaxial posterior fixation techniques.

STUDY DESIGN: Five different reconstructions of the atlantoaxial complex were biomechanically compared in vitro in a nondestructive test. OBJECTIVES: To determine whether non-bone graft-dependent one-point fixation affords stability levels equivalent to three-point reconstructions. SUMMARY OF BACKGROUND DATA: Previous investigations have demonstrated that three-point fixation, using bilateral transarticular screws in combination with posterior wiring, provide the most effective resistance to minimize motion around C1-C2. However, placement of transarticular screws is technically demanding. Posterior wiring techniques affording one-point fixation have failure rates of approximately 15%, with failure considered to be secondary to structural bone graft failures. One-point, non-bone graft-dependent fixations have not been tested. METHODS: Eight human cervical specimens, C0-C3 were loaded nondestructively. Unconstrained three-dimensional segmental motion was measured. The reconstructions tested were two one-point fixations, one two-point fixation, and two three-point fixations. RESULTS: Under axial rotation two and three-point reconstructions provided better stiffness than the one-point reconstructions (P < 0.05). During flexion-extension, higher stiffness levels were observed in one- and three-point fixations when compared with the intact spine (P < 0.05). In lateral bending no significant differences were observed among the six groups, although the trend was that reconstructions including transarticular screws provided greater stability than one-point fixations. CONCLUSION: The current findings substantiate the use of three-point fixation as the treatment of choice for C1-C2 instability. [l: atlantoaxial fixation, biomechanics, cervical spine, instability, spinal instrumentation, transarticular screws]

Aged↗
PubMed2000

Biomechanical properties of anterior thoracolumbar multisegmental fixation: an analysis of construct stiffness and screw-rod strain.

STUDY DESIGN: Three types of anterior thoracolumbar multisegmental fixation were biomechanically compared in construct stiffness and rod-screw strain. OBJECTIVES: To investigate the effects of rod diameter and rod number on construct stiffness and rod-screw strain in anterior thoracolumbar multisegmental instrumentation. SUMMARY OF BACKGROUND DATA: No studies have been undertaken to investigate the biomechanical effects of rod diameter and rod number in thoracolumbar anterior instrumentation. METHODS: Ten fresh-frozen calf spines (T13-L5) were used. After intact analysis, a total discectomy and transection of the ALL and PLL were performed at L1-L2, L2-L3, and L3-L4 with intervertebral reconstruction using carbon fiber cages. Three types of anterior fixation were then performed at L1-L4: 1) 4.75-mm diameter single-rod, 2) 4.75-mm dual-rod, and 3) 6.35-mm single-rod systems. Single screws at each vertebra were used for single-rod and two screws for dual-rod fixation. These systems share the same basic design except rod diameter. Nondestructive biomechanical testing was performed and included compression, torsion, flexion-extension, and lateral bending. Construct stiffness and rod-screw strain of the three reconstructions were compared. RESULTS: The 6.35-mm single-rod fixation significantly improved construct stiffness compared with the 4.75-mm single rod fixation only under torsion (P < 0.05). The 4. 75-mm dual rod construct resulted in significantly higher stiffness than did both single-rod fixations (P < 0.05), except under compression. No statistical differences were observed in rod-screw strain between the two types of single rods, whereas dual-rod reconstruction exhibited less rod-screw strain (P < 0.05). CONCLUSIONS: For single-rod fixation, increased rod diameter neither markedly improved construct stiffness nor affected rod-screw strain, indicating the limitations of a single-rod system. In thoracolumbar anterior multisegmental instrumentation, the dual-rod fixation provides higher construct stiffness and less rod-screw strain compared with single-rod fixation.

Animals↗
PubMed1999

Revision strategies for salvaging or improving failed cylindrical cages.

STUDY DESIGN: This is a review of 20 patients who experienced failure of threaded interbody fusion cages and underwent surgical correction. OBJECTIVE: To review the causes and possible treatment strategies for failed cylindrical cages. SUMMARY OF BACKGROUND DATA: Intraoperative complications have been described in the past; however, management of the postoperative patient with failure of interbody fusion devices has not been described. METHODS: In 20 patients with failed threaded titanium fusion cages (18 Bagby and Kuslich Devices [BAK; Sulzer-Spine Tech, Minneapolis, MN], 2 Ray Threaded Fusion Cages [Ray TFC; Surgical Dynamics, Norwalk, CT) who underwent revision surgery, all had failure before successful arthrodesis was achieved. Eight of the original titanium cages had been inserted anteriorly (7 laparoscopically), and 12 had been inserted for posterior interbody lumbar fusion. Before the revision surgery, five of the implants were thought to be solid by the referring surgeon, but pseudarthrosis was clearly present in all. In addition, 14 other explanted BAK devices were subjected to undecalcified histologic preparation, quantitative histomorphometry, and histopathologic analysis. RESULTS: The average length of time before revision surgery (implant duration) was 31.8 weeks (range, 1-156 weeks). The most common revision procedure was posterior exploration of the symptomatic nerve root with foraminotomy for unrecognized lateral recess stenosis (11 cases) or excision of iatrogenically herniated intervertebral disc fragments (4 cases). However, four cages inserted through posterior exposure during an interbody lumbar fusion procedure had to be removed because of migration into the spinal canal. In nine cases posterior pedicle screw instrumentation was necessary in addition to posterolateral fusion using iliac crest bone grafting. CONCLUSIONS: All 20 cages failed because of surgical technique rather than an intrinsic defect in fusion cage technology. The factors associated with failure of the original insertion procedure were failure to achieve adequate distraction of the anulus fibrosis; undersized cages, especially when placed through the posterior interbody lumbar fusion approach; cerebrospinal fluid leakage or pseudomeningocele; Type 2 diabetes mellitus; the use of local bone graft rather than iliac crest inside the cage; anterior insertion in an excessively lateral position resulting in symptoms of a far lateral disc herniation; and failure to identify the spinal midline during an anterior approach.

Adult↗
PubMed1999

Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis.

STUDY DESIGN: For this retrospective study, preoperative and postoperative radiographs of posterior spinal fusions for idiopathic scoliosis were reviewed. OBJECTIVES: To determine the prevalence and possible causes of proximal kyphosis after posterior spinal fusion for idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Proximal kyphosis has been anecdotally noted after the insertion of Harrington rods and after use of the new posterior multisegmented hook/rod systems. In this study no attempt was made to determine whether this condition is painful or an adverse outcome for the patient or just a radiographic abnormality; however, it is suspected that this may be a problem in the long term, and it may be worthwhile to try to avoid it if predictive values can be ascertained. METHODS: Patients with adolescent idiopathic scoliosis who had undergone posterior spinal fusion not extending above T3 with good-quality radiographs of the proximal thoracic spine and a minimum 2-year follow-up were studied. Of the 106 patients who underwent posterior spinal fusion from 1990 through 1994, 69 met the inclusion criteria. Abnormal kyphosis from T2 to the proximal level of the instrumented fusion was defined as kyphosis of more than 5 degrees above the summed normal angular segments. RESULTS: Of 69 patients, 37 (54%) had normal proximal kyphosis, and 32 (46%) of the 69 were defined as having abnormal proximal kyphosis. In the 32 patients with abnormal proximal kyphosis, the measurement from T2 to the fusion was 10.3 degrees before surgery and 21.2 degrees after surgery. The normal group had kyphosis measuring 2.7 degrees from T2 to fusion before surgery and 5.3 degrees after surgery (P < 0.00001). Junctional kyphosis in the kyphosis group measured 6.5 degrees before surgery and 12.6 degrees after surgery, compared with normal kyphosis of 1.7 degrees and 2.6 degrees, respectively (P < 0.00001). When analyzing who would develop proximal kyphosis, preoperative one-level junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae was shown to have the highest sensitivity (78%) and specificity (84%). CONCLUSIONS: In this study, 32 (46%) of 69 patients had abnormal proximal kyphosis after undergoing posterior spinal fusion. A preoperative junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae indicates that extending the fusion to a higher level in the thoracic spine would be beneficial in avoiding this problem.

Adolescent↗
PubMed1999

Clinicopathological report: mucinous carcinoma of the eyelid.

BACKGROUND: Mucinous carcinoma of the skin is a rare tumour that may involve the peri-ocular region. METHODS/RESULTS: A case report is presented of a 73-year-old woman with a right upper lid tumour, initially diagnosed as a basal cell carcinoma. Excisional biopsy of the residual tumour revealed mucinous carcinoma. Re-examination of the original pathology proved to be mucinous carcinoma, originating in the eyelid skin. Further treatment involved wide local resection and reconstruction. Systemic investigations were undertaken to exclude the possibility of metastatic mucinous carcinoma. CONCLUSION: This case is presented to alert ophthalmologists to the occurrence of this tumour in the periocular region, to highlight the importance of surgical excision with wide margins and the need for systemic investigation to exclude a primary malignancy in other sites, in particular the gastrointestinal system and breast.

Adenocarcinoma, Mucinous↗
PubMed1999

Knowledge of sunlight effects on the eyes and protective behaviors in adolescents.

The knowledge of the effects of sunlight on the eyes and protective behaviors were studied in an adolescent population. A group of 652 systematically sampled students aged between 13 and 17 years was surveyed with a standardized questionnaire in Brisbane, Australia in October-November, 1995. Survey data on the knowledge of sunlight effects on the eyes, ultraviolet light, eye and body protection as well as risk factors for ultraviolet (UV) exposure were relatively ranked and totalled to give overall scores. Of the 652 subjects, 330 (51%) were female. Most subjects (568 or 88%) were aged between 15 and 16 years. Overall, this group of subjects demonstrated a moderate level of knowledge with respect to UV, sunlight and the eyes. The knowledge of the effects of sunlight and body protection was higher than the knowledge of the effects of sunlight and eye protection. Almost three-quarters (462 or 71%) of the subjects owned a pair of sunglasses. The mean age at which subjects started to wear sunglasses was 10.4 years. However, most subjects (528 or 81%) only wore sunglasses occasionally or not at all. The reported frequency of wearing sunglasses was significantly related to personal, family and peer attitudes to such use, but not to media advertizing. Assessment of adolescent knowledge is important in the formulation of health promotion strategies designed to prevent excessive UV exposure at this young age.

Adolescent↗