Correlation Between Stereoacuity and Experimentally Induced Graded Monocular and Binocular Astigmatism.

INTRODUCTION: Stereopsis, the highest grade of binocular single vision, is affected by various factors, such as mis-alignment of visual axes, refractive errors especially anisometropia and astigmatism, both of which may result in amblyopia. There are very few studies in literature regarding the relationship between stereoacuity and refractive errors, especially astigmatism. AIM: The present study was conducted to determine the correlation between stereoacuity and experimentally induced graded astigmatism in emmetropes. MATERIALS AND METHODS: A randomized study was conducted on 2000 individuals of either gender, between the ages of 8-35 years, at tertiary care centre attached to a medical college during the period of August 2012 to August 2014, All subjects were emmetropic with normal binocular single vision. Participants were randomly divided into four groups of 500 individuals each. Two groups were subjected to induced myopic astigmatism, either uni-ocularly or binocularly, using + 1.0 D and + 2.0 D cylinders at varying axes i.e., 45(0), 90(0) and 180(0). Similarily, the remaining two groups were subjected to induced hypermetropic astigmatism, using - 1.0 D and - 2.0D cylinders at varying axes i.e. 45(0), 90(0) and 180(0). Near stereoacuity was determined by the Titmus Fly Stereo Test, both before and after induction of astigmatism. Statistical analysis was done using paired t-test and ANOVA. RESULTS: The mean stereoacuity in emmetropes was 28.81±4.97 seconds of arc. There was a decrease in stereoacuity with increase in dioptric power of astigmatism (p<0.001). Oblique astigmatism reduced the stereoacuity maximally, while stereoacuity was least affected at 180(o) axis. Hypermetropic astigmatism caused more deterioration in stereoacuity than myopic astigmatism. A gross reduction in stereoacuity was noted in induced monocular astigmatism as against binocular astigmatism. CONCLUSION: This study suggests that stereoacuity is significantly affected by even minor degrees of monocular or binocular astigmatism.

Bilateral optic nerve aplasia: a rare isolated central nervous system anomaly.

Optic nerve (ON) aplasia is a rare developmental anomaly comprising of absence of the ON, ganglion cells and the central retinal vessels. It is usually accompanied by a variety of central nervous system (CNS) malformations. We report an extremely rare case of bilateral true ON aplasia occurring as an isolated CNS anomaly. A 10-month-old female child was detected with bilateral absence of fixation, associated with multiple ocular findings of microcornea, anterior embryotoxon, pupillary corectopia, partial aniridia and lens coloboma. The optic disc locations were visible as avascular whitish areas. There were no retinal vessels seen in the disc area or elsewhere. There were bilateral multiple chorioretinal atrophic patches present. B-scan ultrasonography showed bilateral absence of ONs. Magnetic resonance imaging showed thinned out bilateral ONs with a hypoplastic optic chiasma and optic tract. There were no other CNS anomalies. Flash visually evoked potential was unrecordable.

A Clinical Study of Subtype-based Prevalence of Dry Eye.

INTRODUCTION: Dry Eye is a multifactorial disease of the tearfilm and the ocular surface which may be due to reduced tear production or excessive tear evaporation resulting in discomfort, visual disturbance, and tear film instability with a potential damage to the ocular surface. Various population-based studies have been done to find out the prevalence and the magnitude of the problem. Women Health Study reported prevalence of 7.8% after screening 36995 subjects above 49 years by interview. The prevalence reported by Blue Mountain Study was 15.3% .The Beaver Dam Study and Shiphai Eye studies are other studies reporting prevalence of 14.5% and 33.7% respectively. McMonnies questionnaire is a widely used screening instrument for Dry-Eye syndromes with sensitivity reportedly varying between 87% and 98% and specificity between 87% and 97%. Prevalence studies use McMonnie's questionnaire for screening individuals for Dry Eye, whereafter tests like Schirmer's test, Tear Film Break Up Time test, Rose Bengal test, Lissamine Green test and Meibomian Gland Dysfunction test are useful for further evaluation. While these tests help to differentiate the subtypes of Dry Eye such as Lipid Anomaly Dry Eye, Aqueous Tear Deficiency and Mucin Layer Deficiency, however, their sensitivity and specificity has not been widely studied. Additionally, very few studies have reported the prevalence of the various subtypes of Dry Eye. AIM AND OBJECTIVES: To determine the subtype-based prevalence of Dry Eye, to study the specificity and sensitivity of clinical tests for Dry Eye and to correlate McMonnies questionnaire with Dry Eye tests results. MATERIAL AND METHODS: A prospective, cross-sectional, observational study, duly approved by the Institutional Ethics Committee, was conducted from October 2010 to April 2012. A total of 4750 subjects above 18 yrs of age were screened by the McMonnies questionnaire. Respondents having a score greater than 14.5 were subjected to clinical Dry Eye tests. The data obtained was analyzed using chi-square test. p value < 0.005 was considered statistically significant.The specificity and sensitivity of each clinical test was calculated using Schirmer's test as gold standard. RESULTS: The prevalence of Dry Eye was 15.4%, with a female preponderance (p = 0.01) and a significant increase with age above 60 years was noted (p<0.0001). Tear Film Break Up Time was the most reliable test with a good sensitivity (68.85%) and specificity (78.32%). Lipid Anomaly Dry Eye was the most prevalent (14.48%) followed by Aqueous Tear Deficiency (13.36%) and Mucin Layer Deficiency (3.51%). A positive correlation between McMonnies score and severity of Dry Eye was seen. CONCLUSION: This study suggests that Lipid Layer Anomaly is the most prevalent subtype in Dry Eye. Tear Film Break Up Time test is the most likely test to diagnose mild Dry Eye. McMonies Questionnaire can be effectively used for screening of a large population. Tear Film Break Up Time was found to have better sensitivity as well as specificity than other tests used for diagnosing Dry Eye.

The assessment of sleep apnoea as a risk factor in glaucoma.

BACKGROUND: The risk of developing open angle glaucoma increases in the presence of associated disorders such as hypertension, Diabetes mellitus and migraine. In recent years, sleep apnoea is also being investigated as a risk factor in the development of open angle glaucoma. AIM: To ascertain the significance of sleep apnoea as a risk factor in patients with glaucoma. Study Setting and Design: A non - randomised, cross sectional study was undertaken at an urban teaching hospital. MATERIAL AND METHOD: A sleep disturbance questionnaire and the Epworth sleepiness scale were used to screen the potential cases of sleep apnoea amongst 40 glaucomatous subjects, with both Primary Open Angle Glaucoma (POAG) and Normotensive Glaucoma (NTG), as well as 40 controls. Those which gave a positive response to the questionnaire were subjected to poly-somnography for the diagnosis of sleep apnoea, with the calculation of the Apnoea Hypopnoea Index. The data was analysed by using the Chi - square test and the odds ratio calculations. RESULTS: Positive responses to the sleep apnoea questionnaire were obtained from a total of twenty participants, 16 (40%) from the glaucoma Group and four (10%) were obtained from the control Group. In the glaucoma Group, ten (37.03%) of the 27 POAG individuals, and six (46.15%) of the 13 NTG cases showed significant positive responses to the questionnaire. Four subjects (10%) (1POAG, 3 NTG) from the glaucoma Group and one (2.5%) from the control Group were diagnosed to have sleep apnoea by polysomnography. The percentage of the sleep apnoea positive cases was higher among the NTG subjects (23.07%) than among the POAG subjects (3.7 %). This study had an odds ratio of 4.333 (>1) and a p value of 0.382. CONCLUSION: Although the odds ratio was significant, this study did not find the association between sleep apnoea and glaucoma to be statistically significant.

Ivermectin treatment for massive orbital myiasis in an empty socket with concomitant scalp pediculosis.

We report a rare case of massive orbital myiasis following recent lid injury, occurring in the empty socket of an elderly lady, who had concurrent scalp pediculosis. The orbital myiasis was effectively treated with the broad-spectrum antiparasitic agent, ivermectin, thus precluding the need for an exploratory surgery. Ivermectin was also effective in managing the concurrent scalp pediculosis.

A rare and an unusually delayed presentation of orbital actinomycosis following avulsion injury of the scalp.

We report a rare case of orbital swelling presenting one year after head trauma. An initial fine needle aspiration cytology revealed it to be an infected organizing hematoma. However, broad-spectrum antibiotics did not resolve the infection and the orbital lesion continued to grow in size, as evaluated by magnetic resonance imaging. Incisional biopsies were done, which were reported as orbital actinomycosis. Patient has responded well to treatment with penicillin. This case is of interest due to the delayed presentation of an orbital complication of head trauma and the rare infection with actinomyces. It also highlights the importance of using appropriate antibiotics, as well as the need for long-term treatment.