RESUMO
Background: hysteresis refers to the energy lost during the stress/strain cycle which is the result of viscous damping in the corneal tissue, is an indicator of corneal biomechanical properties. Refractive surgery currently uses corneal thickness as a basic qualification and planning parameter. However, corneal hysteresis may be more useful as a qualification factor for LASIK, a significant decrease in the IOP and biomechanical properties is found in eyes following LASIK surgery
Objective: this study aimed to reveal the variations of corneal hysteresis in patients with normal pentacam findings and to see if a correlation exists between corneal hysteresis, corneal resistance factor, mean keratometric reading, central corneal thickness and anterior chamber depth during the pre-operative assessment of myopic patients going for LASIK
Patients and Methods:in this study we did an analysis of corneal hysteresis in a group of myopic patients with normal pentacam findings undergoing evaluation for refractive surgery. In our study we included 50 eyes of 26 patients aged between 18 and 44
Results: this study included a mean keratometric reading of 44.108 D+/- 1.3243D, the mean central corneal thickness was 522.1um+/-38.416um, the mean anterior chamber depth was 3.2098mm+/-0.249mm the mean corneal hysteresis was 9.582 mmHg+/-1.4702 and the mean corneal resistance factor was 9.64 mmHg +/-1.9838
Conclusion: our data suggested that patients should get their corneal hysteresis tested as a part of their routine investigation portfolio before undergoing refractive surgery as it may play a role in determining patients that are at higher risk of developing ectasia after surgery
RESUMO
Purpose: To evaluate the efficacy, advantages and disadvantages of graded transcutaneous levator muscle recession with mullerectomy for treatment of dysthyroid upper eyelid retraction. Design: Randomized, prospective and interventional case series
Methods: This prospective interventional case series comprised 20 eyes of ten patients. Inclusion criteria included patients with bilateral upper eyelid retraction, with or without other manifestations of thyroid orbitopathy, without diplopia and with stable thyroid state for at least 6 months. All patients were subjected to graded transcutaneous levator muscle recession with mullerectomy after full ophthalmological assessment. All patients included in the study have signed a written consent and the study has been approved by the ethical committee of AL-AZHAR faculty of medicine
Results: Postoperatively the mean decrease of MRD1 was 2.87 mm. Mean improvement of lagophthalmos was 0.78 mm. Mean increase of upper lid crease height was 0.65mm. Good lid contour achieved in 85.9%. Temporal flare persisted in one lid [5%] and nasal ptosis was reported in two eye lids [10%]
Conclusion: According to this study graded transcutaneous mullerectomy with levator muscle recession is a good and a reliable surgical technique for correction of dysthyroid upper lid retraction and is successful as a lengthening procedure for retracted upper eyelid regardless the severity of retraction with significant symptomatic and cosmetic improvement