Corneal Topography and Anterior Segment OCT Imaging techniques for assessing the structure and function of the cornea and Anterior segment of the eye play a key role in diagnosing and treating various corneal and anterior segment disorders. Topography is a routine pre-requisite of Laser removal of glasses as well.
Corneal topography is a non-invasive computer-assisted imaging technique for mapping the cornea, the front lens of the eye. It is a three-dimensional topographical map, which evaluates thousands of specific points across the entire corneal surface. The basic advantage of corneal topography is its ability to detect irregular conditions invisible to most conventional testing.
Corneal topography produces a detailed, depiction of the shape and power of the cornea. This analysis provides your doctor with very fine details regarding the condition of the corneal surface. The details are used to diagnose, monitor, and treat various eye conditions. They are also used in fitting contact lenses and for planning surgery, including laser vision correction. For laser vision correction the corneal topography map is used in conjunction with other tests to determine exactly how much corneal tissue will be removed to correct vision and with what ablation pattern.
Uses of Corneal Topography
Corneal topography is most commonly used for the following purposes:
To screen candidates for normal corneal shape, patterns and ruling out suspicious or keratoconic patterns.
Postoperatively, topography can help to assess the dioptric change created at corneal level ( thus the effective change in the cornea), ruling out decentred or incomplete ablation, post excimer ectasia or other changes.
Keratoconus: Early screening of keratoconus suspects is one of the most useful roles of topography. Early keratoconus and suspects look normal on slit lamp examination, and the central keratometry (3 mm) gives only a limited assessment. Therefore topography has become the gold standard in screening keratoconus suspects. In cases with established keratoconus, the role of topography is paramount for monitoring progression and doing a timely collagen cross-linking, and in contact lens fitting.
Post surgery astigmatism: Post cataract surgery and post keratoplasty corneal astigmatism can be studied with the topographer and selective suture removal or other interventions can be planned.
Surgical planning in cases with astigmatism: Limbal relaxing incisions and other methods of topography-guided incision placement are used by surgeons to reduce postoperative astigmatism. Effect of corneal and ocular surface disorders: Disorders such as pterygium, limbal dermoid, localised corneal scars can cause a change in the corneal topography and thus the monitoring is very useful.
Contact lens fitting, incision placement and intrastromal ring placement in keratoconus, monitoring of ocular vs corneal wavefront.
Anterior Segment Optical Coherence Tomography
Anterior segment optical coherence tomography (AS-OCT) was recently developed and has become a crucial tool in clinical practice. AS-OCT is a non-contact imaging device that provides the detailed structure of the anterior part of the eyes.
Clinical Applications of Anterior Segment
Optical Coherence Tomography
AS-OCT can be widely applicable in various clinical diseases, including tear meniscus evaluation,ocular-surface disease, corneal dystrophies and stromal diseases, tissue change analysis after cataract and glaucoma surgery, and angle assessment. This noncontact-type technology with a high resolution and high reproducibility provide comprehensive and quantitative information.