Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

Optical coherence tomography (OCT) is being employed more and more often to image pathologies and surgical anatomy within the anterior segment, specifically in anterior chamber biometry, corneal pachymetric mapping, angle evaluation and high-resolution cross-sectional imaging The cross-sectional imaging capability of OCT is similar to ultrasound, but its higher resolution allows OCT to measure and visualize very fine anatomic structures No contact is required In this review, we describe the utility and limitations of anterior segment OCT

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1442-9071.2008.01823.x

Clinical and research applications of anterior segment optical coherence tomography – a review

Purpose of reviewCorneal measurement uses Placido-disc topographers and tomographers, creating three-dimensional corneal models from cross-sectional images. Technology includes slit scanning, Scheimpflug imaging, very high frequency ultrasound, and high-speed anterior segment optical coherence tomog

Measuring the cornea: the latest developments in corneal topography.

Keratoconus Diagnosis with Optical Coherence Tomography Pachymetry Mapping

BACKGROUND
INTACS are two, arc like, PMMA segments which were designed to be surgically inserted into the deep corneal stroma to flatten the central cornea. Their original application was for the refractive correction of mild myopia (−1 to −3D). However, because of the superior accuracy and familiarity with the excimer laser by refractive surgeons, they are rarely used for this indication, except in patients with forme fruste keratoconus or extremely thin corneas with less than 3D of Myopia (1,2).

Dr. Joseph Colin in France first conceived of the concept of using INTACS to treat patients with keratoconus and published his first report on the safety and efficacy for this indication in 2001(3). At 1 year, all 10 patients he operated became contact lens tolerant and demonstrated an improvement in both uncorrected and best-corrected acuity (4).

Since his pioneering work, corneal surgeons throughout the word have adopted this technology to treat patients with mild to moderate keratoconus who are contact lens intolerant and/or who desire a modest improvement in uncorrected and best-corrected visual acuity (5-14).

In the United States 0.25mm, 0.275mm, 0.30mm, 0.325mm and 0.35mm segments are available for use. They are approved in the United States by the FDA under an Human Devise Exemption for compassionate therapeutic use. Outside of the United States .40mm and 0.45mm sized segments are also available. Competitive devices the Ferrara ring and the Keraring are also sold and marketed outside of the United States since they do not have FDA approval in the USA. The main difference between these two devices is that with INTACS the optical zone is approximately 7mm while the Ferrara and Kerarings have an optical zone of the order of 4.5 to 5mm.

Recently Intacs SK was introduced outside of the United States. They have an optical zone of 6 mm and have a round design to minimize glare. They may be used to correct larger myopic and astigmatic refractive errors than INTACS because of their design and closer proximity to the visual axis(15)

INTACS for keratoconus.

High-speed optical coherence tomography of corneal opacities

Purpose To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system. Setting Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. Methods A prospective observational case series comprised 4 eyes of 4 patients receiving Intacs intrastromal corneal ring segments (Addition Technology, Inc.) for keratoconus. Optical coherence tomography (OCT) was performed between 7 days and 43 days after implantation. Results The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements ( r 2 = 0.68). The fractional implantation depth was correlated with several surgical variables using a stepwise multivariate regression model, and 2 statistically significant correlations were found. The position of the distal portions of the ring segments was shallower than that of the portion closer to the insertion site ( P = .003). Segments placed in the inferior cornea ( P  = .008) experienced more distal shallowing. Shallower depth was associated with greater fractional anterior stromal compression ( P = .04). Conclusions Shallower placement of intrastromal corneal ring segments may result in more complications, such as epithelial–stromal breakdown and extrusion, because of the greater anterior stromal tensile strain. The distal and inferior portions of intrastromal corneal ring segments tended to be placed at a shallower depth. Optical coherence tomography provided precise measurement of ring segment depth and may help identify implants that pose a greater risk for depth-related complications.

/pdf/optical-coherence-tomography-to-assess-intrastromal-corneal-cezyn6wrte.pdf

Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes

Keloids are usually formed in individuals after skin trauma and are thought to be the result of altered wound healing with excessive scar tissue formation.1 We describe a bulbar conjunctival keloid confirmed by immunohistochemical analysis and scanning electron microscopy.

A 48-year-old Hispanic man presented with a medial conjunctival lesion in his left eye. The patient had underwent pterygium surgery in the same location 2 years previously. At 6 months after surgery, he noted progressive growth of a conjunctival mass that persisted over the next year. On examination, his vision was 20/25 in the right eye and 20/30 in the left …

/pdf/keloid-of-the-conjunctiva-simulating-a-conjunctival-35wbji1vv6.pdf

Michael M. Lai

Papers

High-speed optical coherence tomography of corneal opacities

Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes

Keloid of the conjunctiva simulating a conjunctival malignancy