PubMed Health⌕ Search

Biomedical subjects

Colin S H Tan

Publications and source records attributed to Colin S H Tan.

At least 19 recordsLinked to original sources
PubMed2006

Visual experiences during different stages of LASIK: Zyoptix XP microkeratome vs Intralase femtosecond laser.

PURPOSE: To describe the loss of light perception and other visual experiences encountered during different stages of laser in situ keratomileusis (LASIK) and to compare patients' experiences between LASIK performed with the Zyoptix XP microkeratome and Intralase laser. DESIGN: Prospective, randomized, self-matched clinical study. METHODS: Forty-one patients (82 eyes) had bilateral LASIK with the corneal flap fashioned by Zyoptix XP microkeratome in one eye and Intralase laser in the other. They were interviewed postoperatively with a standardized questionnaire about their intraoperative visual experiences, including light perception and ability to see the red fixation light. RESULTS: During both vacuum suction and corneal flap fashioning, a higher proportion of eyes in the Zyoptix XP microkeratome group lost light perception compared with the Intralase group (85.4% vs 39.0% and 90.2% vs 61.0%; P < .001 and P = .004, respectively). Patients also saw flashes, various colors, movement, the surgeon's hands or fingers, and the surgeon during surgery, and there was no difference in these visual experiences between the Zyoptix XP microkeratome and Intralase groups. Overall, eight (19.5%) of 41 patients were frightened by their intraoperative visual experiences during LASIK. CONCLUSIONS: Patients retain light perception during most stages of LASIK except during suction and fashioning of the corneal flap, when some are temporarily unable to see. Many also experience various visual sensations intraoperatively, and 19.5% of patients are frightened by their visual experiences.

Adult↗
PubMed2006

Visual hallucinations during visual recovery after central retinal artery occlusion.

BACKGROUND: Charles Bonnet syndrome is characterized by complex, formed visual hallucinations that occur in patients without psychiatric disorders. To the best of our knowledge, it has not been described following central retinal artery occlusion. OBJECTIVE: To describe 2 patients who experienced formed visual hallucinations characteristic of Charles Bonnet syndrome after sudden, severe visual loss precipitated by central retinal artery occlusion. PATIENTS: Two patients, aged 77 and 63 years respectively, experienced sudden deterioration of vision following central retinal artery occlusion. Formed visual hallucinations occurred in patient 1 six days later and in patient 2 two days later. RESULTS: The hallucinations appeared both within and at the borders of the patients' residual intact visual fields. They occurred during periods when the patients experienced partial visual recovery associated with enlargement of their visual fields. The visual recovery and hallucinations both ceased at the same time. CONCLUSIONS: We propose that the hallucinations are likely the result of deafferentation and their occurrence during visual recovery suggests that they are a correlate of visual system plasticity.

Aged↗
PubMed2006

What can patients see during glaucoma filtration surgery under peribulbar anesthesia?

PURPOSE: To describe the visual sensations experienced by patients during glaucoma filtration surgery under peribulbar anesthesia and to determine possible risk factors that may affect the visual sensations experienced. SETTING: King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia. METHODS: In this prospective questionnaire study, 75 consecutive adult patients listed for glaucoma filtration surgery (trabeculectomy or Ahmed tube implantation) under peribulbar anesthesia were interviewed postoperatively about the visual sensations experienced in their operated eye during the surgery. RESULTS: The mean age of the 75 patients was 59.7 years (range, 27 to 83, SD +/-12.1). Sixty-five patients (86.7%) perceived light perception during the surgery and the overall light intensity fluctuated in 45 patients (60.0%). The mean age of the patients who retained light perception intraoperatively was significantly lower compared with those who lost light perception (58.3 y vs. 68.8 y; P=0.009). Forty-six patients (61.3%) were able to perceive colors, 32 patients (42.7%) perceived movement, 31 patients (41.3%) saw surgical instruments, and 33 patients (44.0%) reported seeing the surgeon's hands or fingers. The severity of glaucoma did not affect the proportion of patients who perceived the various visual sensations. One patient (1.3%) was frightened by his intraoperative visual experience. Of the remaining patients, 53 (70.7%) said the visual sensations did not affect them, whereas 21 (28.0%) found them unpleasant. CONCLUSIONS: The majority of patients undergoing glaucoma filtration surgery retained light perception intraoperatively and many also experienced various visual sensations. Only 1.3% of patients were frightened by their visual experience.

Adult↗
PubMed2006

Ophthalmic complications of dengue.

We report 13 cases of ophthalmic complications resulting from dengue infection in Singapore. We performed a retrospective analysis of a series of 13 patients with dengue fever who had visual impairment. Investigations included Humphrey automated visual field analyzer, Amsler charting, fundus fluorescein angiography, and optical coherence tomography. Twenty-two eyes of 13 patients were affected. The mean age of patients was 31.7 years. Visual acuity varied from 20/25 to counting fingers only. Twelve patients (92.3%) noted central vision impairment. Onset of visual impairment coincided with the nadir of serum thrombocytopenia. Ophthalmologic findings include macular edema and blot hemorrhages (10), cotton wool spots (1), retinal vasculitis (4), exudative retinal detachment (2), and anterior uveitis (1). All patients recovered visual acuity to 20/30 or better with residual central scotoma by 12 weeks. These new complications suggest a widening spectrum of ophthalmic complications in dengue infection.

Adult↗
PubMed2006

A nationwide survey on the knowledge and attitudes of Malaysian optometry students on patients' visual experiences during cataract surgery.

INTRODUCTION: During cataract surgery under regional (retrobulbar, peribulbar or sub- Tenon's) or topical anaesthesia, many patients experience a variety of visual sensations in their operated eye intraoperatively. Between 3% and 16.2% of patients are frightened by their intraoperative visual experiences, which may increase the risk of intraoperative complications and affect patients' satisfaction with the surgery. This study aims to determine optometry students' beliefs and knowledge of visual sensations experienced by patients during cataract surgery under regional and topical anaesthesia. MATERIALS AND METHODS: A nationwide survey of all Malaysian optometry students using a standardised, self-administered questionnaire. RESULTS: All 129 optometry students participated in the survey, giving a 100% response rate. Overall, 26.4% and 29.5% of the students believed that patients undergoing cataract surgery under regional and topical anaesthesia, respectively, may experience no light perception, while 78.3% and 72.9%, respectively, thought that patients would experience light perception. Many respondents also believed that patients might experience a variety of other visual sensations. Of all respondents, 70.5% and 74.4% of students believed that patients undergoing cataract surgery under regional and topical anaesthesia, respectively, may be frightened by their visual experience and 93.0% and 85.3%, respectively, felt that preoperative counselling might help to alleviate this fear. CONCLUSION: Many optometry students are aware that patients might encounter a variety of visual sensations during cataract surgery under local anaesthesia. A high proportion of students believe that patients may experience fear as a result of the intraoperative visual sensations and felt that preoperative counselling would be helpful.

Adult↗
PubMed2006

SARS in Singapore--predictors of disease severity.

INTRODUCTION: Severe acute respiratory syndrome (SARS) affected 8096 individuals in 29 countries, with 774 deaths. In Singapore, there were 238 cases of SARS with 33 deaths. A retrospective analysis was performed to identify predictors of poor outcome in patients with SARS locally. MATERIALS AND METHODS: Clinical, laboratory and outcome data of 234 patients admitted to Tan Tock Seng Hospital and Singapore General Hospital were collected and analysed. Only data collected at the time of admission were used in the analysis for predictors of poor outcome. Adverse events were defined as admission to the intensive care unit or death. RESULTS: Clinical (temperature, FiO2) and laboratory [leukocyte, lymphocyte, neutrophil, platelet, lactate dehydrogenase (LDH), albumin] trends in groups with and without an adversarial event were presented. Fifty patients experienced an adverse event. On univariate analysis, male gender, advanced age, presence of comorbidities, neutrophilia, lymphopaenia, hyponatraemia, hypoalbuminaemia, transaminitis and elevated LDH or C-reactive protein were found to be significant predictors. On multivariate analysis, predictors of poor outcome were increased age [odds ratio (OR) 1.73 for every 10-year increase; 95% CI, 1.35 to 2.21], neutrophilia (OR 1.06 for every 1 x 10(9)/L increase; 95% CI, 1.02 to 1.11) and high LDH (OR 1.17 for every 100 U/L increase; 95% CI, 1.02 to 1.34). None of the 12 paediatric patients had an adverse event. CONCLUSION: Advanced age, neutrophilia and high LDH predict poor outcomes in patients with SARS.

Adolescent↗
PubMed2006

Neisseria meningitidis keratitis in adults: a case series.

INTRODUCTION: The aim of this case series is to describe the clinical course of 2 patients with Neisseria meningitidis corneal ulcers. CLINICAL PICTURE: A 49-year-old man (Patient 1) and a 22- year-old man (Patient 2) both experienced eye pain and were found to have corneal ulcers with surrounding infiltrate and ground-glass appearance. Gram-negative diplococci were seen in the first case. N. meningitidis was isolated in culture of corneal scrapings from both patients. TREATMENT: Patient 1 was treated with levofloxacin (0.5%) and cefazolin (50 mg/mL) eye drops hourly and intravenous ceftriaxone and oral rifampicin. Patient 2 was treated with cefazolin (50 mg/mL) and gentamicin (14 mg/mL) eye drops hourly, as well as intravenous ceftriaxone. OUTCOME: The corneal ulcers resolved with anterior stromal scarring and no impairment of vision. CONCLUSIONS: Corneal ulcers caused by N. meningitidis may respond well to treatment without permanent visual sequelae. However, in view of the potential ocular and systemic complications, it is important to investigate and treat patients with N. meningitidis infection aggressively.

Adult↗
PubMed2005

Visual experiences during vitreous surgery under regional anesthesia: a multicenter study.

PURPOSE: To investigate patients' subjective intraoperative visual experiences during vitreous surgery performed under regional anesthesia, to ascertain if patients were frightened by their visual experiences, and to determine the risk factors associated with a frightening visual experience. DESIGN: Multicenter, prospective study. METHODS: Sixty-five patients who had vitreous surgery under regional (retrobulbar or peribulbar) anesthesia in five centers in Ireland, Singapore, and Hong Kong were interviewed within 2 hours of their operation using a standardized questionnaire. RESULTS: Thirty patients (46.2%) perceived light perception throughout the entire operation, 19 patients (29.2%) experienced transient loss of light perception, and 16 patients (24.6%) experienced no light perception throughout the entire duration of the surgery. Nine patients (13.8%) were frightened by their intraoperative visual experiences. Patients who were frightened by their visual experiences were more likely to see color (100%) than those who were not frightened (55.4%) (P = .010). The mean age of the patients who were frightened was lower (51.8 years) compared with those who were not frightened (64.6 years) (P = .003). The mean duration of surgery was longer for patients who were frightened (118.9 minutes) compared with those who were not frightened (91.2 minutes) (P = .047). CONCLUSIONS: Most patients undergoing vitreous surgery under regional anesthesia retained at least light perception intraoperatively. Importantly, 13.8% of patients were frightened by their visual experiences. A younger age, longer duration of surgery, and perception of color were risk factors for a frightening visual experience.

Adult↗
PubMed2005

Visual experiences during cataract surgery: what anaesthesia providers should know.

Recently published literature shows that most patients experience a variety of visual sensations during cataract surgery under local anaesthesia. Most patients (80-100%) retain at least some light perception in the operated eye and many also experience a variety of other visual sensations during cataract surgery under regional ophthalmic anaesthesia (retrobulbar, peribulbar and sub-Tenon's blocks) or topical anaesthesia. The visual sensations experienced include perception of movements, flashes, colours, changes in brightness, or the sight of surgical instruments, the surgeon's hands or fingers, or even the surgeon. These findings are clinically significant because 3-16.2% of patients who had cataract surgery under either regional or topical anaesthesia were frightened by their intraoperative visual experience. Fear and anxiety may cause some patients to become uncooperative during the surgery and may also induce a sympathetic stress response that might cause hypertension, tachycardia with myocardial ischaemia, hyperventilation or an acute panic attack. These effects are especially undesirable as the majority of cataract patients are elderly and have concurrent medical problems. Besides increasing the risk of intraoperative complications, a frightening visual experience may decrease patient satisfaction. Appropriate preoperative counselling has been shown to be effective in reducing the patients' fear. As most patients retain some visual function during cataract surgery under local anaesthesia, anaesthesia providers should be mindful of this phenomenon and offer appropriate preoperative information and counselling to their patients.

Anesthesia, Local↗
PubMed2005

Visual experience during cataract surgery: a nation-wide survey on the knowledge of optometry students.

PURPOSE: Many patients experience a variety of visual sensations during cataract surgery under local anaesthesia. Up to 16.2% of patients are frightened by their intraoperative visual experience. This study aimed to determine the knowledge and beliefs of optometry students on this subject. METHODS: A nationwide survey using a standardised, self-administered questionnaire was conducted on all optometry students in Singapore. RESULTS: For cataract surgery under regional anaesthesia, 38.9% of the respondents believed that patients might experience no light perception while 68.5% felt that patients were likely to be able to perceive light. Overall, 70.4% felt that patients might be frightened by their visual experiences and 88.0% believed that preoperative counselling of patients would serve to reduce the fear experienced during the surgery. For cataract surgery under topical anaesthesia, 37.0% of the respondents believed that patients would perceive no light and 74.1% believed that patients would retain light perception. Overall, 67.6% believed that patients may be frightened and 86.1% felt that preoperative counselling would help. CONCLUSION: Many optometry students correctly believed that patients might experience a variety of visual sensations during cataract surgery under local anaesthesia. The majority were also aware that patients might be frightened by this and felt that preoperative counselling would be helpful.

Adolescent↗