Automatic segmentation and quantified analysis of meibomian glands from infrared images

Purpose: An algorithm for automated segmentation of meibomian glands from infrared images obtained using a novel prototype infrared hand?held imager has been proposed in this study. Meibomian gland dysfunction (MGD) is quantified in terms of five clinically relevant metrics. A comparison of these metrics in patients with MGD has been presented against a sample of the normative healthy population. Methods: This is a prospective cross?sectional observational study. Patients presenting to the clinics were enrolled after written informed consent. The everted eyelids of 200 eyes of patients (of which 100 were healthy and 100 were diagnosed with MGD) were imaged using a prototype hand?held camera. The proposed algorithm was used to process the images using enhancement techniques and the glands were automatically segmented. A comparison of glands of normal eyes versus MGD?affected eyes is performed using five metrics presented in this study: (i) drop?out, (ii) length, (iii) width, (iv) the number of glands, and (v) the number of tortuous glands. Results: The 95% confidence interval for the metrics did not show any overlap between the two groups. In MGD patients, the drop?out ratio was higher than normal. The length and number of glands were significantly lesser than normal. A number of tortuous glands were more in the MGD group. The metrics for MGD versus healthy and cut?off ranges were computed in the results. Conclusion: The prototype infrared hand?held meibographer and the proposed automatic algorithm for gland segmentation and quantification are effective aids in MGD diagnosis. We present a set of five metrics, which are clinically relevant for guiding clinicians in the diagnosis of MGD

Repeatability and Agreement of Four Biometers for Measuring Various Anterior Segment Parameters.

Purpose: To assess the repeatability and agreement of a new swept source optical coherence tomography (SS-OCT) biometer (IOL Master® 700, Carl Zeiss Meditec), an optical low coherence reflectometer (Lenstar LS 900®, Haag-Streit AG, Koeniz, Switzerland), a dual scheimpflug ray tracing biometer (Galilei G6®, Ziemer, Switzerland) and a partial coherence interferometer, AL scan® (Nidek Co. Ltd., Japan) to measure the keratometry (K), astigmatism (AST), axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT) and white-to-white (WTW) in cataractous eyes in a Cross-sectional study. Methods: 50 eyes of 50 consecutive patients scheduled for cataract surgery were included. Three consecutive scans were performed using the 4 biometers by a single operator. Within-subject standard deviation (Sw), test-retest repeatability and coefficient of variation for assessing repeatability were assessed. Bland-Altman plots for the agreement between the mean measurements of each machine were examined. Results: The mean age of patients was 60.2 ± 10.6 years. Dropouts for AL measurement were significantly higher in AL scan® and Galilei G6® compared to IOL Master® 700. There was good agreement between IOL Master® 700 and Lenstar LS 900® for AL and keratometry (P < 0.5). High variability was seen between the 4 machines for AST and WTW. Conclusion: The new SS-OCT biometer showed valid measurements, good repeatability and good agreement with the optical low coherence reflectometry biometer. The new long range SS-OCT biometer was better than the other three devices in acquiring AL measurements in denser cataracts due to better penetration.

Systematic Transition to Phaco-Chop.

Phaco surgeons initially train in a four quadrant divide and conquer technique. Subsequently, several surgeons transition to chopping techniques due to the perceived advantages of phaco-chop that include lower ultrasound energy and lesser zonular stress. Stop and chop has conventionally been the technique of choice for making this transition. However, the surgeon has to execute a full-fledged chop after the creation of two hemi-segments by the classical trenching and cracking skills already acquired in divide and conquer techniques. Here we describe a set of intermediate steps during four quadrant divide and conquer that breaks down the skills required for chopping and enables the surgeon to sequentially imbibe the required skill sets to make the transition to chop safer and smoother.

Toric implantable collamer lens for keratoconus.

Keratoconus is a progressive non-inflammatory thinning of the cornea that induces myopia and irregular astigmatism and decreases the quality of vision due to monocular diplopia, halos, or ghost images. Keratoconus patients unfit for corneal procedures and intolerant to refractive correction by spectacles or contact lenses have been implanted toric posterior chamber phakic intraocular lenses (PC pIOLs) alone or combined with other surgical procedures to correct the refractive errors associated with keratoconus as an off label procedure with special informed consent from the patients. Several reports attest to the safety and efficacy of the procedure, though the associated corneal higher order aberrations would have an impact on the final visual quality.

Keratoconus: A biomechanical perspective on loss of corneal stiffness.

Keratoconus (KC) is progressive disease of corneal thinning, steepening and collagen degradation. Biomechanics of the cornea is maintained by the intricate collagen network, which is responsible for its unique shape and function. With the disruption of this collagen network, the cornea loses its shape and function, resulting in progressive visual degradation. While KC is essentially a stromal disease, there is evidence that the epithelium undergoes significant thinning similar to the stroma. Several topographical approaches have been developed to detect KC early. However, it is now hypothesized that biomechanical destabilization of the cornea may precede topographic evidence of KC. Biomechanics of KC has been investigated only to a limited extent due to lack of in vivo measurement techniques and/or devices. In this review, we focus on recent work performed to characterize the biomechanical characteristics of KC.

Safety and efficacy of Intacs in Indian eyes with keratoconus: an initial report.

CONTEXT: In contact lens-intolerant keratoconus patients, intrastromal placement of Intacs is becoming a promising new modality of treatment. AIMS: To study the safety and efficacy of implantation of microthin corneal inserts (Intacs) in Asian-Indian keratoconus patients. SETTINGS AND DESIGN: Retrospective interventional case series, in the cornea and refractive surgery service, at a tertiary care eye hospital in South India, between May 2006 and July 2007. MATERIALS AND METHODS: Intacs (Addition Technology, USA) were successfully implanted by mechanically creating tunnels, in 12 eyes of 12 keratoconus patients, who were contact lens-intolerant. The patients (mean age 25.58 years, nine male and three female) had a minimum follow-up of six months. Five patients had severe keratoconus (mean K > 53 D) and nine had central cones. RESULTS: All patients improved or retained visual acuity. The uncorrected visual acuity (UCVA) improved from a mean value of 0.06, (SD +/- 0.08) to 0.19 postoperatively (SD+/- 0.15) ( P = 0.01). The change in mean best corrected visual acuity (BCVA) was from 0.51, (SD +/- 0.24), to 0.69, (SD +/-0.00) ( P = 0.01) postoperatively. The average central keratometry reading was 52.55 D. The change in mean K from 52.84 to 49.16 and 49.15 at one and six months respectively, was statistically significant. We did not have any major intra- or early postoperative complications. Eight of 12 eyes became contact lens-tolerant post-surgery. CONCLUSION: The procedure of Intacs implantation appears to be safe and effective in a small group of Indian population at an intermediate follow-up.