ABSTRACT
PURPOSE: To evaluate the efficacy of customized surface ablation in cases of forme fruste keratoconus. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Eleven eyes of 8 contact lens-intolerant patients with forme fruste keratoconus treated at the Institute of Refractive and Ophthalmic Surgery and the University Eye Clinic Zurich. INTERVENTION: Topography-guided customized surface ablation by means of a scanning spot excimer laser. MAIN OUTCOME MEASURES: Visual acuity, refraction, quality of vision (ghosting), corneal topography including the Zernike parameter Z3. RESULTS: Statistically significant reduction of manifest refractive error, corneal irregularity, and ghosting. The spherical equivalent was reduced by -2.8+/-0.62 diopters (D) (P = 0.0007), the cylinder by 1.34 +/- 0.18 D (P = 0.015), Z3 was reduced by 41% (P<0.001), and all patients had less ghosting compared to their preoperative status. No eye lost > or =1 lines in best spectacle-corrected visual acuity; however, 7 of 11 eyes gained > or = 1 line. CONCLUSION: Topography-guided surface ablation is a promising option to rehabilitate vision in contact lens-intolerant patients with forme fruste keratoconus.
Subject(s)
Cornea/surgery , Corneal Topography , Keratectomy, Subepithelial, Laser-Assisted/methods , Keratoconus/surgery , Photorefractive Keratectomy/methods , Adult , Cornea/physiopathology , Humans , Keratoconus/physiopathology , Lasers, Excimer , Middle Aged , Pilot Projects , Prospective Studies , Refraction, Ocular/physiology , Treatment Outcome , Vision Disorders/rehabilitation , Visual Acuity/physiologyABSTRACT
OBJECTIVE: The aim of this study was to determine whether elastography, a sonographically based real-time strain imaging method for registering the elastic properties of tissue, can be used in brain tumor surgery. METHODS: A modification of classic elastography called vibrography was applied in these measurements with static compression replaced by low-frequency axial vibration. Twenty patients were examined with this technique during brain tumor surgery. A conventional sonographic system with a custom-designed radio frequency (RF) interface was used. The RF data were digitized with a 50-MHz, 12-bit peripheral component interconnect analog/digital converter for real-time or offline processing. Sonographic RF data were acquired with a 6.5-MHz endocavity curved array. A special applicator equipped with a stepping motor moved the ultrasonic probe and produced a low-frequency mechanical vibration of approximately 5 to 10 Hz with a vibration amplitude of 0.3 mm. RESULTS: Detection of tumors was possible in 18 of 20 cases. Brain tissue was normally color coded orange or red. Three major groups of tumors with different elastic properties relative to brain tissue could be differentiated. In 3 cases, the stiffness of the tumor was identical to that of brain tissue, but the tumors were surrounded by a thin yellow border. Six tumors displayed higher strain than brain, whereas 7 tumors exhibited lower strain than the surrounding cerebrum. Two patients could not be assigned clearly to either of these groups. CONCLUSIONS: These findings indicate that vibrography is a feasible imaging method for brain tumor surgery and may have numerous potential applications in neurosurgery if further improvements are made.
