Measuring the biomechanics of the cornea
The correct measurement of the cornea’s biomechanical properties can have significant clinical applications
The correct measurement of the cornea’s biomechanical properties can have significant clinical applications, from the measurement of intraocular pressure to the evaluation of progression in glaucoma and keratoconus. Cynthia Roberts, Ohio, USA, discussed the details of these properties at the 21st ESCRS Winter Meeting in Maastricht, The Netherlands.
The goal is to distinguish the effects of corneal biomechanic variables from the actual measurements sought, such as IOP.
After explaining the differences between elasticity, viscoscity and viscoelasticity, Dr Roberts focused on another property, hysteresis, a viscoelastic parameter with a time-dependent component that describes the difference in response during loading and unloading of a force on a tissue. This is of particular importance for pneumotonometry, which relies on analysis of the corneal biomechanical response to an air puff. The variables encountered can be complex, particularly in pathologic conditions, such as keratoconus, and in eyes that have undergone refractive surgery. Both conditions result in a lower level of hysteresis. Conversely, corneal cross-linking causes a stiffening of the cornea, as well as a corresponding increase in hysteresis.
Two commercial pneumotonometry devices have been designed to analyse these responses: the Ocular Respons Analyzer (ORA; Reichert) and the Corvis ST (Oculus). The ORA can produce several different measurements, including the corneal-compensated IOP (IOPcc) and the Goldmann-correlated IOP. “The IOPcc is less affected by corneal thickness and properties,” said Dr Roberts, which means that IOP measurements should more accurately reflect the actual pressure inside the eye.
The goal is to distinguish the effects of corneal biomechanic variables from the actual measurements sought, such as IOP.EUROTIMES Measuring the biomechanics of the cornea LATEST
Intraocular Implant and Refractive Society of India (IIRSI) 2017Wednesday, August 16, 2017
The annual conference of the Intraocular Implant and Refractive Society of India (IIRSI) 2017 was held on 8th and 9th of July at the ITC Grand Chola Hotel, Chennai. More than 3,000 Indian and international ophthalmologists assembled at the meeting. The conference was inaugurated by the Honorable Minister for Health and Family Welfare, Dr. K. […]
Ophthalmoscopy still the key to glaucoma diagnosisMonday, July 3, 2017
George Spaeth MD Baseline optic disc photographs remain an essential tool in the diagnosis of glaucoma, said George Spaeth MD, Wills Eye Hospital, Philadelphia, Pennsylvania, USA. “The ideal diagnostic test is that it to be valid and relevant diagnosis allows staging and provide a permanent baseline against which future tests can be compared. It should […]
Portable brain-computer interface provides objective visual function test for glaucomaMonday, July 3, 2017
A new portable electroretinography device that can be used in conjunction with an iPhone can provide good objective measurements of visual field loss on a par with standard automated perimetry (SAP) and other types of visual field testing, said C Gustavo De Moraes, MD, MPH, Columbia University, New York, New York, USA. “This portable […]
Atropine halts myopia progressionTuesday, June 13, 2017
A low-dose formulation of atropine slowed the progression of myopia for a majority of treated children over a two-year period with no adverse side effects, according to a study presented at the European Society of Ophthalmology (SOE) 2017 Congress in Barcelona. “Our experience in this small study shows that atropine seems to be safe […]
Ophthalmic effects of long-term spaceflightMonday, May 8, 2017
Retired astronaut and US Navy Captain Scott Kelly was one of the keynote speakers at the 2017 ASCRS/ASAO Congress. Among the topics he discussed in a wide-ranging speech looking back on his career, was the ophthalmic effects of long-term spaceflight, including increased cerebral fluid pressure, optic nerve swelling and retinal folds. Captain Kelly lived […]
Accelerated corneal crosslinking worksMonday, May 8, 2017
An accelerated corneal crosslinking (CXL) approach appears to be safe for treating patients with progressive keratoconus, and delivers comparable visual and corneal biomechanical results to the standard Dresden protocol while reducing treatment time 60 minutes to 18 minutes, Thomas Kohnen MD, PhD, told the 2017 ASCRS•ASOA Symposium & Congress in Los Angeles, USA. In a retrospective […]
Better visual acuity with FLACSSunday, May 7, 2017
Karl Stonecipher MD Patients treated with femtosecond laser-assisted cataract surgery (FLACS) had significantly better uncorrected visual acuity (UCVA) three hours after surgery than those treated with conventional phaco cataract surgery, Karl Stonecipher MD told the 2017 ASCRS•ASOA Symposium & Congress in Los Angeles, USA. Mean UCVA for 1,015 FLACS patients was 20/32 compared with 20/50 […]
Which MIGS device to use in a patient with glaucoma?Tuesday, February 21, 2017
In general, MIGS devices should be restricted to patients with mild-to moderate glaucoma controlled by medication.
Handling complicationsFriday, February 17, 2017
Catarina Pedrosa MD Catarina Pedrosa MD, Lisbon, Portugal, advised delegates attending the 21st ESCRS Winter Meeting in Maastricht, The Netherlands, on how to avoid problems when performing cataract surgery in posterior polar cataract, and how to solve them once they occur. Dr Pedrosa was speaking during a session entitled ‘The Usual Suspects: How to Handle Your […]
Diagnosis and medical treatment of fungal keratitisThursday, February 16, 2017
Matthew Burton PhD, London, UK, gave the keynote speech on infectious keratitis at the annual Cornea Day, during the 21st ESCRS Winter Meeting in Maastricht, The Netherlands. “A significant trend is a move away from yeast infections and toward filamentous fungal keratitis over the past decade, which currently cause 70% of fungal infections in our hospital,” […]