corneal topography – Using the Allegro Topolyser which uses Placido’s disc to optain a high resolution image og the corneal curvatures
it is used in some cases of custom LASIK specially with high astigmatism or irregular corneal surface.
Corneal topography and tomography is most commonly used for the following purposes
- Refractive surgery: To screen candidates for normal corneal shape, patterns and ruling out suspicious or keratoconic patterns . Post operatively , imaging can help to assess the dioptric change created at corneal level ( thus the effective change in the cornea) , ruling out de-centered or incomplete ablation , post excimer ectasia or other changes.
- Keratoconus : Early screening of keratoconus suspects is one of the most useful roles of corneal imaging. Early keratoconus and suspects look normal on slit lamp examination ,and the central keratometry (3 mm) gives only a limited assessment. Therefore imaging has become the gold standard in screening keratoconus suspects. In cases with established keratoconus, the role of topography and tomography is paramount for monitoring progression and doing a timely collagen cross linking , and in hard contact lens fittings.
- 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 corneal astigmatism : Limbal relaxing incisions and other methods of topography guided incision placement are used by surgeons to reduce post operative astigmatism.
- Effect of corneal and ocular surface disorders: Disorders such as pterygium , limbal dermoids, corneal scars, or degenerations can cause changes in the corneal curvature and irregular astigmatism.
- Other uses : Contact lens fitting , incision placement and intrastromal ring placement in keratoconus , monitoring of ocular vs corneal wavefront.