Sensitivity and specificity measure inherent validity of a diagnostic test against a gold standard. Researchers develop new diagnostic methods to reduce the cost, risk, invasiveness, and time. Adequate sample size is a must to precisely estimate the validity of a diagnostic test. In practice, researchers generally decide about the sample size arbitrarily either at their convenience, or from the previous literature. We have devised a simple nomogram that yields statistically valid sample size for anticipated sensitivity or anticipated specificity. MS Excel version 2007 was used to derive the values required to plot the nomogram using varying absolute precision, known prevalence of disease, and 95% confidence level using the formula already available in the literature. The nomogram plot was obtained by suitably arranging the lines and distances to conform to this formula. This nomogram could be easily used to determine the sample size for estimating the sensitivity or specificity of a diagnostic test with required precision and 95% confidence level. Sample size at 90% and 99% confidence level, respectively, can also be obtained by just multiplying 0.70 and 1.75 with the number obtained for the 95% confidence level. A nomogram instantly provides the required number of subjects by just moving the ruler and can be repeatedly used without redoing the calculations. This can also be applied for reverse calculations. This nomogram is not applicable for testing of the hypothesis set-up and is applicable only when both diagnostic test and gold standard results have a dichotomous category.

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Retinopathy of prematurity (ROP) is a significant cause of childhood blindness. The criteria for laser therapy have been revised from threshold ROP to include the earlier stage of high-risk prethreshold ROP. Laser photocoagulation is an established technique for the treatment of ROP. However, the detailed procedure and techniques for laser photocoagulation have not yet been published. Adequate and appropriate laser photocoagulation for ROP is different from the application of lasers in adult retinal vascular diseases, and many ophthalmologists need to be trained in this technique if the outreach of ROP treatment programs is to improve. Laser under topical anesthesia has been practiced in India as a preferred modality especially due to logistics and risks of general anesthesia in these pre-term babies. We discuss the details of the technique as practiced at tertiary care ophthalmic hospitals in India, so that the nuances in treatment parameters and clinical decision-making can be usefully applied to ophthalmic practice. This will ultimately lead to safe and effective treatment delivery in ROP.

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In most areas in life, it is difficult to work with populations and hence researchers work with samples. The calculation of the sample size needed depends on the data type and distribution. Elements include consideration of the alpha error, beta error, clinically meaningful difference, and the variability or standard deviation. The final number arrived at should be increased to include a safety margin and the dropout rate. Over and above this, sample size calculations must take into account all available data, funding, support facilities, and ethics of subjecting patients to research.

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Aims: To identify the etiology, incidence and prevalence of ocular bacterial infections, and to assess the in vitro susceptibility of these ocular bacterial isolates to commonly used antibiotics. Materials and Methods: Retrospective analysis of consecutive samples submitted for microbiological evaluation from patients who were clinically diagnosed with ocular infections and were treated at a tertiary eye care referral center in South India between January 2002 and December 2007. Results: A total of 4417 ocular samples was submitted for microbiological evaluation, of which 2599 (58.8%) had bacterial growth, 456 (10.3%) had fungal growth, 15 (0.34%) had acanthamoebic growth, 14 (0.32%) had mixed microbial growth and the remaining 1333 (30.2%) had negative growth. The rate of culture-positivity was found to be 88% (P < 0.001) in eyelids' infection, 70% in conjunctival, 69% in lacrimal apparatus, 67.4% in corneal, 51.6% in intraocular tissues, 42.9% in orbital and 39.2% in scleral infections. The most common bacterial species isolated were Staphylococcus aureus (26.69%) followed by Streptococcus pneumoniae (22.14%). Sta. aureus was more prevalent more in eyelid infections (51.22%; P = 0.001) coagulase-negative staphylococci in endophthalmitis (53.1%; P = 0.001), Str. pneumoniae in lacrimal apparatus and corneal infections (64.19%; P = 0.001), Corynebacterium species in blepharitis and conjunctivitis (71%; P = 0.001), Pseudomonas aeruginosa in keratitis and dacryocystitis (66.5%; P = 0.001), Haemophilus species in dacryocystitis and conjunctivitis (66.7%; P = 0.001), Moraxella lacunata in blepharitis (54.17%; P = 0.001) and Moraxella catarrhalis in dacryocystitis (63.83%; P = 0.001). The largest number of gram-positive isolates was susceptible to moxifloxacin (98.7%) and vancomycin (97.9%), and gram-negative isolates to amikacin (93.5%) and gatifloxacin (92.7%). Conclusions: Gram-positive cocci were the most frequent bacteria isolated from ocular infections and were sensitive to moxifloxacin and vancomycin, while gram-negative isolates were more sensitive to amikacin and gatifloxacin.

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A prospective comparative study was undertaken to compare the patients' pain experience, surgical outcome and surgeon's experience in phacoemulsification and manual small incision cataract surgery (MSICS) under topical anesthesia supplemented with intracameral lignocaine (TASIL). In Group 1 (n=88) phacoemulsification was done and in Group 2 (n=92) MSICS was done. Pain scores were marked by the patients on a Visual analog scale (VAS) after the surgery. The surgical experience was noted on a questionnaire by the operating surgeon. Descriptive analysis and one-tailed Mann-Whitney test were used to draw results. The average VAS score in Group 1 was 0.65 (SD 1.31) and in Group 2 it was 0.90 (SD 1.22). This difference in the average was not statistically significant with P=0.09. The study demonstrates that MSICS and phacoemulsification both can be done safely under TASIL with acceptable patient comfort, and the pain experienced by the patients during the procedures is comparable.

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Background: Stimuli-sensitive hydrogels are three-dimensional, hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluids on stimulation, such as pH, temperature and ionic change. Aim: To develop hydrogels that are sensitive to stimuli, i.e. pH, in the cul-de-sac of the eye for providing a prolonged effect and increased bioavailability with reduction in frequency of administration. Materials and Methods: Hydrogels were formulated by using timolol maleate as the model drug, polyacrylic acid as the gelling agents, hydroxyl ethyl cellulose as the viscolizer and sodium chloride as the isotonic agent. Stirring of ingredients in pH 4 phosphate buffer at high speed was carried out. The dynamic dialysis technique was used for drug release studies. In vivo study for reduction in intraocular pressure was carried out by using albino rabbits. Statistical Analysis: Drug release studies data were used for statistical analysis in first-order plots, Higuchi plots and Peppas exponential plots. Student t-test was performed for in vivo study. Results: Viscosity of the hydrogel increases from 3.84 cps to 9.54 cps due to change in pH 4 to pH 7.4. The slope value of the Peppas equation was found to be 0.3081, 0.3743 and 0.2964. Up to 80% of drug was released in an 8 h drug release study. Sterile hydrogels with no ocular irritation were obtained. Conclusions: Hydrogels show increase in viscosity due to change in pH. Hydrogels were therapeutically effacious, stable, non-irritant and showed Fickian diffusion. In vivo results clearly show a prolonged reduction in intraocular pressure, which was helpful for reduction in the frequency of administration.

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Incidence of preoperative rise in blood pressure (BP) in cataract surgery among hypertensive and normotensive patients. Objective: To study the incidence of preoperative rise in BP in cataract surgery among normotensive individuals and hypertensive patients with historic good BP control in a population without other major chronic diseases. Settings: Ophthalmology Service of a University Hospital. Materials and Methods: A prospective study with 822 patients older than 40 years of age, with cataract surgery indication, and without major chronic diseases other than hypertension. The patients were divided in two groups: hypertensive and normotensive. Preoperative data, physical exams and medical adverse events were recorded in an evaluation questionnaire. Results: The sample included 427 normotensive (52%) and 395 hypertensive patients (48%). The two groups had similar proportions of operations that were cancelled and not subsequently rescheduled, 2% (eight patients) in each group. The incidence of preoperative rise in BP was 3.7% in the normotensive group and 10.9% in the hypertensive group (P < 0.001). Conclusion: Hypertensive patients with historic good BP control and without other major co-morbidities present a larger incidence of preoperative rise in BP than normotensive individuals in cataract surgery.

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We report a rare instance of favorable outcome in orbital apex syndrome secondary to herpes zoster ophthalmicus (HZO) in a human immunodeficiency virus (HIV)-positive patient. The patient complained of pain and decrease in vision in one eye (20/640) for 2 weeks accompanied with swelling, inability to open eye, and rashes around the periocular area and forehead. The presence of complete ophthalmoplegia, ptosis, relative afferent pupillary defect, and anterior uveitis with decreased corneal sensation prompted a diagnosis of HZO with orbital apex syndrome. The enzyme-linked immunosorbent assay test and a low CD4 count confirmed HIV. Highly active antiretroviral therapy (HAART), systemic acyclovir, and systemic steroids were started. Visual acuity and uveitis improved within 10 days. By the end of the fourth week, ocular motility also recovered and the final visual acuity was 20/25. We highlight the role of HAART, used in conjunction with systemic steroid and acyclovir therapy, in improving the outcome.

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We are reporting a case of bilateral Fuchs' heterochromic iridocyclitis with chikungunya virus infection in the left eye. A 20-year-old female was presented with a past history of fever suggestive of chikungunya with bilateral Fuchs' heterochromic iridocyclitis and complicated cataract. She had a tripod dendritic pattern of keratic precipitates by confocal microscopy in the left eye with a stippled pattern of keratic precipitates in both eyes. The real-time polymerase chain reaction (RT-PCR) assay in the aqueous humor detected 98 copies/ml of chikungunya virus RNA. The patient underwent clear corneal phacoemulsification with in-the-bag intraocular lens implantation in the left eye with a good visual outcome. This is the first report where the presence of chikungunya virus RNA has been associated with a case of bilateral Fuchs' heterochromic iridocyclitis.

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Partial optic nerve avulsion (ONA) secondary to finger gouging is an uncommon but devastating injury. A 21-year-old man who had an acute vision loss after accidentally getting poked by himself in his right eye when he fell down during jogging is reported. The patient was diagnosed with partial ONA. Magnetic resonance imaging revealed intact optic nerve. Optical coherence tomography (OCT) revealed deep cavity at the inferior-temporal half of the optic disc. Retinal nerve fiber layer thickness was also thin at the inferior quadrant with circumpapillary OCT scan. Visual field test and electrophysiological tests showed functional abnormality compatible with optic nerve lesion. Diagnostic tools for anatomical and functional evaluation may reveal the course of this injury.

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An 82-year-old female presented with sudden painless decrease in vision in the right eye after awakening. She could see the "superior half" of her vision from the right eye only. On examination, best-corrected vision was 20/300 in the right eye and 20/30 in the left eye. The fundus in the right eye revealed recent superotemporal branch retinal artery occlusion (BRAO) with calcified plaque at the disc. Spectral domain optical coherence tomography (OCT) (OTI Ophthalmic Technologies, Inc.), revealed hyperreflectivity and increased thickness of the inner retinal layers of the superior compared to the inferior retina. Imaging at the optic disc revealed the blocked artery containing a highly reflective material. The high reflectivity of the material and underlying optical shadowing could be characterized as calcific emboli.

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We report risk factors associated with intraocular penetration of caterpillar hair seen at our institute from January 2005 to December 2007. Records of all patients with caterpillar hair induced ophthalmitis (CHIO) were retrospectively reviewed for clinical characteristics, anatomic location of lodgment of the caterpillar hair, treatment methods, and outcomes. Out of a total of 544 cases of CHIO, 19 eyes (seven in the anterior chamber and 12 in the posterior segment) experienced intraocular penetration (3.5%). The presence of deep intracorneal hair (80 cases, 14.7%) was found to be the only risk factor for intraocular penetration ( P < 0.001). The removal of intracorneal hair was possible in only 29 out of 80 eyes (36%) and this was associated with a significantly reduced risk of intraocular penetration ( P = 0.022). Patients with retained intracorneal hairs should be counseled regarding risk of intraocular penetration and closely followed up for at least six months.

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Background: Diabetes is one of the major causes of cataract. Some drugs prescribed for the treatment of diabetes are the modulators of CYP450, which may alter the risk of cataract. Objective: To study the effect of CYP450 modulation in galactosemic cataract. Materials and Methods: Male Sprague-Dawley suckling rats were allotted to four groups (n = 6), as follows: Group 1: Normal control, Group 2: Galactose control, Group 3: CYP450 inhibitor pretreated and Group 4: CYP450 inducer pretreated. Cataract was induced in animals of all groups except group 1 by feeding them galactose (50%), 21 days after parturition. From the eighteenth day of life, CYP450 inhibitor (nifedipine; 8.1 mg/kg) and CYP450 inducer (pioglitazone; 3.8 mg/kg) were given orally to groups 3 and 4, respectively. The maturation pattern of the cataract was observed by an operating microscope, every third day. Biochemical changes in the lenses of all groups, for example, CYP450 activity expressed as ΅M NADPH oxidized / unit time, alterations in the levels of total proteins, soluble proteins, and reduced glutathione (GSH) following the induction of cataract, were estimated. Results: The microscopic examination of the lenses indicated that CYP450 inhibitor pre-treatment delayed (fourteenth day) the occurrence of cataract, while CYP450 inducer pretreatment demonstrated an early (ninth day) cataract as compared to galactose control rats (twelfth day). A significant decrease and increase in CYP450 activity was observed with the CYP450 inhibitor and inducer pre-treatment, respectively. There was no alteration in the GSH level, but a significant increase in total and soluble protein was found in groups 3 and 4 as compared to group 2. Conclusion: CYP450 may have a role in the initiation of cataract without any effect on the maturation pattern, as revealed by the delayed occurrence of cataract with the CYP450 inhibitor and an early onset of cataract with the CYP450 inducer.

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Pyomyositis is a primary acute bacterial infection usually caused by Staphylococcus aureus. Any skeletal muscle can be involved, but the thigh and trunk muscles are commonly affected. Only three cases of extraocular muscle (EOM) pyomyositis have been reported. We herein present four cases of isolated EOM pyomyositis. Three of our cases presented with acute onset of proptosis, pain, swelling and redness. One patient presented with mass in the inferior orbit for 4 months. One patient had central retinal artery occlusion on presentation. None of them had marked systemic symptoms. Computed tomography scan of all patients showed a typical hypodense rim enhancing lesion of the muscle involved. Three patients were started on intravenous antibiotics immediately on diagnosis and the pus was drained externally. Two patients underwent exploratory orbitotomy. In conclusion, it should be considered in any patient presenting with acute onset of orbital inflammation. Management consists of incision and drainage coupled with antibiotic therapy.

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Aim: To study the relationship between ocular parameters and amplitude of accommodation (AA) in the peri-presbyopic age group (35-50 years). Materials and Methods: Three hundred and sixteen right eyes of consecutive patients in the age group 35-50 years, who attended our outpatient clinic, were studied. Emmetropes, hypermetropes and myopes with best-corrected visual acuity of 20/20, J1 in both eyes were included. The AA was calculated by measuring the near point of accommodation. The axial length (AL), central anterior chamber depth (CACD) and lens thickness (LT) were also measured. Results: There was moderate correlation (Pearson's correlation coefficient r = 0.56) between AL and AA as well as between CACD and AA (r = 0.53) in myopes in the age group 35-39 years. In the other age groups and the groups taken as a whole, there was no correlation. In hypermetropes and emmetropes, there was no correlation between AA and the above ocular parameters. No significant correlation existed between LT and AA across different age groups and refractive errors. Conclusion: There was no significant correlation between AA and ocular parameters like anterior chamber depth, AL and LT.

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Purpose: To compare the diagnostic performance of the Heidelberg retinal tomograph (HRT) glaucoma probability score (GPS) with that of Moorfield's regression analysis (MRA). Materials and Methods: The study included 50 eyes of normal subjects and 50 eyes of subjects with early-to-moderate primary open angle glaucoma. Images were obtained by using HRT version 3.0. Results: The agreement coefficient (weighted k) for the overall MRA and GPS classification was 0.216 (95% CI: 0.119 - 0.315). The sensitivity and specificity were evaluated using the most specific (borderline results included as test negatives) and least specific criteria (borderline results included as test positives). The MRA sensitivity and specificity were 30.61 and 98% (most specific) and 57.14 and 98% (least specific). The GPS sensitivity and specificity were 81.63 and 73.47% (most specific) and 95.92 and 34.69% (least specific). The MRA gave a higher positive likelihood ratio (28.57 vs. 3.08) and the GPS gave a higher negative likelihood ratio (0.25 vs. 0.44).The sensitivity increased with increasing disc size for both MRA and GPS. Conclusions: There was a poor agreement between the overall MRA and GPS classifications. GPS tended to have higher sensitivities, lower specificities, and lower likelihood ratios than the MRA. The disc size should be taken into consideration when interpreting the results of HRT, as both the GPS and MRA showed decreased sensitivity for smaller discs and the GPS showed decreased specificity for larger discs.

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Perforating injuries of the orbit involving the paranasal sinuses are uncommon. We report a case in which a large wooden foreign body lodged in the posterior orbit and maxillary sinus was surgically removed by a combined approach by ophthalmologists and ear, nose and throat surgeons.

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We experienced two cases of the influx of the sclerotomy site bleeding into the anterior chamber during 23-gauge sutureless vitrectomy for pseudophakic rhegmatogenous retinal detachment. Soon after the removal of a 23-gauge microcannula at the end of the surgery, presumed sclerotomy site hemorrhage was rapidly fluxed into the anterior chamber. The anterior chamber bleeding might come from the sclerotomies rather than from episcleral vessels. The posterior pressure in the gas-filled pseudophakic eye might have pushed the sclerotomy site bleeding into the anterior chamber. We could not find any vitreous hemorrhages. The hemorrhage within the anterior chamber spontaneously absorbed within 14 days.

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We report the use of DNA chip technology in the identification of Toxoplasma gondii as the etiological agent in two patients with recurrent intermediate uveitis (IU). Both patients had recurrent episodes of vitritis (with no focal retinochoroidal lesion) over varying time intervals and were diagnosed to have IU. The tuberculin test was negative in both. Blood counts, erythrocyte sedimentation rate, and serum angiotensin convertase enzyme levels were normal. In both cases, the vitreous fluid tested positive for the T. gondii DNA sequence by using a uveitis DNA chip (XCyton Pvt. Ltd., Bangalore, India). It contained complimentary sequences to "signature genes" of T. gondii, Mycobacterium tuberculosis, M. chelonae, and M. fortuitum. The enzyme-linked immunosorbent assay (ELISA) detected elevated serum antitoxoplasma IgG levels in both. They responded to the antitoxoplasma therapy with oral co-trimoxazole (and additional intravitreal clindamycin in patient 1), with no recurrence during follow-ups of 6 and 8 months, respectively.

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