Biomedical subjects

Hemamalini Arvind

Publications and source records attributed to Hemamalini Arvind.

6 recordsLinked to original sources

PubMed2006

Multifocal visual evoked responses to dichoptic stimulation using virtual reality goggles: Multifocal VER to dichoptic stimulation.

Multifocal visual evoked potentials (mfVEPs) have demonstrated good diagnostic capabilities in glaucoma and optic neuritis. This study aimed at evaluating the possibility of simultaneously recording mfVEP for both eyes with dichoptic stimulation using virtual reality goggles and also to determine the stimulus characteristics that yield maximum amplitude. ten healthy volunteers were recruited and temporally sparse pattern pulse stimuli were presented dichoptically using virtual reality goggles. Experiment 1 involved recording responses to dichoptically presented checkerboard stimuli and also confirming true topographic representation by switching off specific segments. Experiment 2 involved monocular stimulation and comparison of amplitude with Experiment 1. In Experiment 3, orthogonally oriented gratings were dichoptically presented. Experiment 4 involved dichoptic presentation of checkerboard stimuli at different levels of sparseness (5.0 times/s, 2.5 times/s, 1.66 times/s and 1.25 times/s), where stimulation of corresponding segments of two eyes were separated by 16.7, 66.7,116.7 & 166.7 ms respectively. Experiment 1 demonstrated good traces in all regions and confirmed topographic representation. However, there was suppression of amplitude of responses to dichoptic stimulation by 17.9+/-5.4% compared to monocular stimulation. Experiment 3 demonstrated similar suppression between orthogonal and checkerboard stimuli (p = 0.08). Experiment 4 demonstrated maximum amplitude and least suppression (4.8%) with stimulation at 1.25 times/s with 166.7 ms separation between eyes. It is possible to record mfVEP for both eyes during dichoptic stimulation using virtual reality goggles, which present binocular simultaneous patterns driven by independent sequences. Interocular suppression can be almost eliminated by using a temporally sparse stimulus of 1.25 times/s with a separation of 166.7 ms between stimulation of corresponding segments of the two eyes.

Adult↗

PubMed2006

Prevalence of angle-closure disease in a rural southern Indian population.

OBJECTIVE: To estimate the prevalence of primary angle-closure glaucoma, primary angle closure (PAC), and primary angle-closure suspect (PACS) and its associated risk factors in a rural population in southern India. METHODS: Three thousand and nine hundred thirty-four (81.95%) of 4800 enumerated subjects aged 40 years or older underwent a complete ophthalmic examination, including compression gonioscopy. Glaucoma was diagnosed using International Society of Geographical and Epidemiological Ophthalmology classification. RESULTS: Data were analyzed for 3924 subjects (81.75%). Primary angle-closure glaucoma was diagnosed in 34 subjects (0.87%; 95% confidence interval [CI], 0.58 to 1.16) (27 women, 7 men). The mean intraocular pressure was 20.71 +/- 9.24 mm Hg. One subject (2.94%) was blind. Twenty-eight subjects (0.71%; 95% CI, 0.45 to 0.98) were diagnosed to have PAC (21 women, 7 men). Eleven subjects (39.3%) had an intraocular pressure greater than 21 mm Hg, 13 subjects (46.43%) had peripheral anterior synechiae, and 4 subjects (14.29%) had both. Two hundred forty-six subjects (6.27%; 95% CI, 5.51 to 7.03) had PACS (168 women, 78 men). Primary angle closure and primary angle-closure glaucoma were more common in women (age-adjusted odds ratio, 3.02; 95% CI, 1.66 to 5.51) with an increasing prevalence with age. Increasing intraocular pressure was associated with the disease (odds ratio, 1.14; 95% CI, 1.09 to 1.19). There was no association with hypertension and hyperopia. Axial length and anterior chamber depth were longer in the normal group than in the 3 groups with angle closure (P<.05). Women had shorter axial lengths than men (P<.001) in the angle closure groups. CONCLUSIONS: The overall prevalence of primary angle closures (PAC and primary angle-closure glaucoma) in a rural population of southern India was 1.58%. There was a female preponderance, and the disease tends to be asymptomatic.

Adult↗

PubMed2005

Effect of cataract surgery with intraocular lens implant on frequency doubling perimetry.

PURPOSE: To study the effect of cataract surgery with intraocular lens (IOL) on frequency doubling perimetry (FDP). METHODS: Patients aged 40 years or above seen at our outpatient clinic with no ocular pathology except for visually significant cataract and visual acuity 6/24 or better were eligible. They underwent FDP before and 4 to 6 weeks after cataract surgery with IOL. RESULTS: Screening test: Mean scores by three different scoring methods were 1.82 (3.21), 2.80 (5.54), 4.18 (9.18) before and 0.22 (0.51), 0.26 (0.63), 0.26 (0.69) after surgery (p = 0.002 0.001, < 0.0001). Threshold test: Mean deviation (MD) and pattern standard deviation (PSD) were -5.23 (3.08) and 5.15 (2.78) before and -2.94 [corrected] (2.49) (p < 0.0001) and 5.21 (1.780) (p = 0.63) after surgery. CONCLUSIONS: The screening test should be interpreted cautiously in the presence of cataract. On threshold testing, cataract surgery causes significant decrease in MD but no change in PSD.

Adult↗

PubMed2005

Prevalence of open-angle glaucoma in a rural south Indian population.

PURPOSE: To determine the prevalence of primary open-angle glaucoma (POAG) and the associated risk factors in a rural population in southern India. METHODS: Subjects aged 40 years or more (n = 3934) underwent a complete ophthalmic examination. Glaucoma was diagnosed according to the International Society of Geographical and Epidemiologic Ophthalmology classification. RESULTS: Complete data were available for 3924 subjects (response rate, 81.75%). In eyes with normal suprathreshold visual fields, the mean intraocular pressure was 14.29 +/- 3.32 mm Hg (97.5th and 99.5th percentiles, 21 and 25 mm Hg, respectively). The mean vertical cup-to-disc ratio was 0.39 +/- 0.17 (97.5th and 99.5th percentiles, 0.7 and 0.8, respectively). Sixty-four subjects had definite POAG (1.62%, 9.5% CI 1.42-1.82); 30 were men and 34 were women. Subjects with POAG (59.85 +/- 10.43 years) were older (P < 0.001) than the study population (53.78 +/- 10.71 years). In only one (1.5%) person was POAG diagnosed before the study. Two (3.12%) subjects were blind due to POAG; 21 (32.81%) subjects had a presenting IOP >21 mm Hg, and 43 (67.19%) had an IOP <21 mm Hg. The mean central corneal thickness in subjects with POAG (502.82 +/- 35.29 microm) was not different from that of the normal study population (505.93 +/- 31.11 microm). No association was found with diabetes mellitus, systemic hypertension, gender, and myopia. Increasing IOP (per mm Hg) was associated with the disease (OR 1.12; 95% CI, 1.08-1.16). The odds for POAG increased with advancing age after adjustment for gender. CONCLUSIONS: The prevalence of POAG in this population was 1.62%. The prevalence increased with age, and 98.5% were not aware of the disease.

Adult↗

PubMed2004

Prevalence of refractive errors in a rural South Indian population.

PURPOSE: To report the prevalence of refractive errors in a rural south Indian population. METHODS: Four thousand eight hundred subjects (age, >39 years) from rural south India were enumerated for a population-based study. All participants underwent complete ophthalmic evaluation. Subjects who were phakic in the right eye with best corrected visual acuity of 20/40 or better were included for analysis. Association of refractive errors with age, sex, cataract, and diabetes mellitus were analyzed. RESULTS: Of the 3924 responders, 2508 were eligible. The unadjusted prevalence of emmetropia (spherical equivalent [SE], -0.50 to +0.50 diopter sphere [DS]), myopia (SE < -0.50 DS), high myopia (SE < -5.00 DS), and hyperopia (SE > 0.50 DS) were 50.60%, 26.99%, 3.71%, and 18.70% and age and gender adjusted for the rural Tamil Nadu population were 46.77%, 30.97%, 4.32%, and 17.94%, respectively. The prevalence of emmetropia decreased significantly with age (P < 0.0001), and the prevalence of myopia and high myopia increased significantly with age (P < 0.001) and were significantly associated with nuclear sclerosis (P < 0.001). The prevalence of hyperopia increased until 60 years of age and then decreased. Hyperopia was more common among women than men (P < 0.001) and was negatively associated with nuclear sclerosis (P < 0.001) and positively with diabetes mellitus (P = 0.008). Of the participants with astigmatism (cylindrical error greater than 0.50 DC), 9.80% had with-the-rule (WTR) and 77.44% against-the-rule (ATR) astigmatism. The prevalence of WTR and ATR astigmatism significantly decreased (P < 0.001) and increased (P = 0.006) with age, respectively. CONCLUSIONS: The pattern of refractive errors in this rural south Indian population is similar to those reported in other tropical regions of the world.

Adult↗

PubMed2003

Methods and design of the Chennai Glaucoma Study.

PURPOSE: To describe the methodology of a population-based study to estimate the prevalence of glaucoma in a rural and urban South Indian population and to study the genetics of glaucoma in this population. METHODS: A sample size of 4758 each for rural and urban populations in the Indian state of Tamil Nadu was calculated. Eligible subjects aged 40 years and above from the rural study area covering 32 contiguous villages and the urban area comprising five random clusters in Chennai city are enumerated. Demographic data are collected in the field. A detailed clinical examination, including glaucoma diagnostic procedures, is conducted at the examination centre. Pedigree ascertainment and genetic studies are performed for subjects with occludable angles or glaucoma. Data are recorded in a computerised database. CONCLUSIONS: This study is expected to result in an estimation of the prevalence and a better understanding of the genetics of glaucoma in this region.

Adult↗