ABSTRACT
Purpose: To study the effect of pupil dilation on a biometric iris recognition (BIR) system for personal authentication and identification. Methods: A prospective, non?randomized, single?center cohort study was conducted on patients who reported for a routine eye check?up from November 2017 to November 2019 (2 years). An iris scanning device “IRITECH?MK2120U” was used to initially enroll the undilated eyes. Baseline scans were taken after matching with the enrolled database. All eyes were topically dilated and matched again with the enrolled database. The Hamming distance (a measure of disagreement between two iris codes) and recognition status were recorded from the device output, and eyes were evaluated by slit?lamp ophthalmoscopy with special emphasis on pupil shape, size, and texture. Results: All 321 enrolled eyes matched after topical dilation. The pupil size had a significant effect on Hamming distance with a P value <0.05. There were no false matches. A correct recognition rate of 100% was obtained after dilation. No loss of iris texture or pupil shape was observed after dilation. Conclusion: A BIR system is a reliable method for identification and personal authentication after pupil dilation. Topically dilated pupils are not a cause for non?recognition of iris scans.
ABSTRACT
Purpose: To compare the stereoacuity in patients with anisometropia, isometropia, and emmetropia. Methods: A cross?sectional study was conducted on 1403 subjects (range: 5–45 years) divided into anisometropes (n = 403), isometropes (n = 500), and emmetropes (n = 500). There were 258 amblyopic eyes among anisometropes and 156 amblyopic eyes among isometropes. Stereoacuity was measured using the Titmus stereo test consisting of a combination of contour targets. Results: There were 675 males and 728 females. A significant (P < 0.001) reduction in stereoacuity was found in anisometropes as compared to isometropes and emmetropes. The stereoacuity was even worse in amblyopes as compared to non?amblyopes. Most patients with anisometropia of <3.0 D had fair stereoacuity. However, as the degree of anisometropia increased to >3.0 D, stereoacuity deteriorated gradually. Marked reduction of stereoacuity was observed in severe degree of anisometropia (>6.0 D). Overall, an anisometropia of ?2.12 D was associated with reduced stereoacuity. Among the anisometropes, it was found to be the poorest in myopia, followed by myopia with astigmatism, hypermetropia with astigmatism, and hypermetropia. Conclusion: The level of stereoacuity was worse in anisometropes as compared to isometropes and emmetropes. Amblyopes had a greater reduction in stereoacuity than non?amblyopes. Stereoacuity decreased as the degree of anisometropia increased. Among the anisometropes, myopes had worst stereoacuity than hypermetropes.
ABSTRACT
Purpose: To determine the retinal nerve fiber layer (RNFL) thickness and ganglion cell complex (GCC) thickness in patients having relative afferent pupillary defect (RAPD) measured by optical coherence tomography (OCT). Methods: This cross?sectional study was conducted on 30 patients with posterior segment disease and glaucoma presenting with RAPD. The control group comprised 30 patients with the aforementioned diseases without RAPD. RAPD was graded using neutral density filters placed over the unaffected eye. Peripapillary RNFL thickness and macular GCC were measured using the Cirrus HD?OCT machine. Results: There were 45 males and 15 females. There was a statistically significant (P < 0.05) difference in the mean of average RNFL thickness in patients having RAPD (64.73 ± 15.16 ?m in the affected eyes) as compared to sick control (82.73 ± 11.33 ?m in the affected eyes). It was further observed that there was a decrease in RNFL thickness with advancing grades of RAPD. There was a statistically significant (P < 0.05) difference in the mean of average GCC thickness in patients having RAPD (51.57 ± 14.96 ?m in the affected eyes) as compared to sick control (76.36 ± 8.06 ?m in the affected eyes). Conclusion: Our study suggests that there is a significant reduction in RNFL thickness and GCC thickness in RAPD patients as compared to the sick control group
ABSTRACT
Migration of silicone explants through rectus muscle insertion is a rare complication with very few cases reported. Anterior migration of a solid silicone band may occur if it is tight, placed anterior to the equator or not properly anchored to the sclera. The band slowly erodes through the tendon of one or more recti muscles allowing them to reattach spontaneously with scar tissue behind migrating element. The authors describe a rare case of anterior migration of the buckle following encirclage by a 4mm silicone band resulting in spontaneous disinsertion of medial rectus muscle where muscle disinsertion had not been performed peroperatively. This migration occurred in the absence of any predisposing factors. The muscle disinsertion was so gradual that the muscle got reinserted almost to its original insertion as a result of which there was no heterotropia .
ABSTRACT
PURPOSE: (1) To find out the relationship of the depth of amblyopia with the degree of anisometropia, in untreated cases of anisometropic amblyopia without strabismus, for both myopic and hypermetropic individuals. (2) To find out the relationship between various ocular parameters, such as axial length and corneal curvature, with the degree of anisometropia between the two eyes. MATERIALS AND METHODS: This prospective study was conducted between January 2001 and March 2003, in 85 cases of untreated anisometropic amblyopia, who attended the author's out patient department. All these patients were subjected to a meticulous ocular examination, with special emphasis on (1) refraction under cycloplegia (2) best corrected visual acuity (3) measurement of axial length by A Scan (4) keratometry . The depth of amblyopia was calculated in two ways: (1) By finding out decimal visual acuity for each eye and subsequently calculating their difference. (2) By converting the Snellen acuity into Log MAR units, which was calculated by finding the Logarithm of the reciprocal of the decimal visual acuity for the two eyes, followed by calculating the difference between the two. The difference in refraction between the two eyes as a measure of anisometropia, was determined by the difference in spherical equivalent between the refraction for each eye. RESULTS: On comparing hypermetropic and myopic cases, a significant correlation was found between depth of amblyopia and the degree of anisometropia, in both myopic and hypermetropic patients. The correlation coefficients were however, found to be greater for hypermetropic than myopic individuals. It was observed that the difference between the axial length of the two eyes contributed to a major part of anisometropia, more so in myopic cases. CONCLUSIONS: The depth of amblyopia correlates with the degree of anisometropia in previously untreated anisometropic amblyopia patients.