Renato Ambrósio

Dry eye associated with laser in situ keratomileusis: Mechanical microkeratome versus femtosecond laser.

PURPOSE: To compare the incidence of laser in situ keratomileusis (LASIK)–associated dry eye and the need for postoperative cyclosporine A treatment after flap creation with a femtosecond laser and a mechanical microkeratome. SETTING: Cole Eye Institute, Cleveland, Ohio, USA. METHODS: Eyes were randomized to flap creation with an IntraLase femtosecond laser (30 or 60 kHz) or a Hansatome microkeratome. No patient had signs, symptoms, or treatment of dry eye preoperatively. Flap thickness was determined by intraoperative ultrasonic pachymetry. Slitlamp assessments of the cornea and need for postoperative dry‐eye treatment were evaluated preoperatively and 1 month postoperatively. RESULTS: The flap was created with the femtosecond laser in 113 eyes and with the microkeratome in 70 eyes. The difference in mean central flap thickness between the femtosecond group (111 μm ± 14 [SD]) and the microkeratome group (131 ± 25 μm) was statistically significant (P<.001). The incidence of LASIK‐associated dry eye was statistically significantly higher in the microkeratome group (46%) than in the femtosecond group (8%) (P<.0001), as was the need for postoperative cyclosporine A treatment (24% and 7%, respectively) (P<.01). In the microkeratome group, there was no correlation between thick flaps and a higher incidence of LASIK‐induced dry eye. CONCLUSIONS: Eyes with femtosecond flaps had a lower incidence of LASIK‐associated dry eye and required less treatment for the disorder. In addition to neurotrophic effects from corneal nerve cutting, other factors may be important because no correlation was found between flap thickness (or ablation depth) and the incidence of LASIK‐induced dry eye.

Analyzing Tomographic Thickness for Detecting Corneal Ectatic Diseases

Keratoconus and other ectatic corneal diseases (ECD) are classically referred as noninflammatory thinning disorders. While ECD are characterized by progressive bulging with steepening and conic protrusion of the cornea, thinning is a hallmark. Clinical diagnosis of moderate to advanced disease is not difficult because of the presence of irregular astigmatism and the development of classic biomicroscopic signs: Fleischer’s corneal epithelial iron ring, Vogt’s striae, Munson’s sign, and Rizzuti’s sign. However, the identification of subclinical mild forms of the disease in patients with normal best spectacle-corrected visual acuity and no other clinical signs is challenging and requires complementary imaging for diagnosis. A comprehensive tomographic evaluation of corneal thickness has become paramount for enhancing the diagnostic accuracy. The goal of this chapter is to present tomographic pachymetric evaluation of corneal architecture and its usefulness for diagnosing keratoconus.

Analyzing Tomographic Corneal Elevation for Detecting Ectasia

Anterior segment tomography offers significant advantages in detecting ectatic disease when compared to traditional Placido-based anterior curvature analysis. Tomography allows for the measurement of both the anterior and posterior surfaces and the creation of a three-dimensional reconstruction of the anterior segment. Changes on the posterior surface frequently predate any observable anterior changes and allows for an earlier detection of early of subclinical disease.

Post Refractive Surgery Ectasia

Progressive “iatrogenic” ectasia or keratectasia is a relatively rare but very severe complication of kerato-refractive procedures. While this has been a very hot topic for research, with significant advances on the recognition of risk factors, there are still mysteries related to the cases that develop ectasia with no identifiable risk factors, and also to the cases of successful surgery that remain stable despite of multiple risk factors (including abnormal topography). Integration of clinical data with advanced ancillary exams (beyond but not over front surface topography) enables an enhanced screening approach that increases the accuracy for detecting susceptible cases. This chapter focuses on ectasia after laser vision correction procedures and also overviews the diagnosis and management options that we have available for managing patients that develop such severe complication. Whereas this is an area of dynamic developments, we present fundamental concepts, along with information on the most recent studies and future prospects.