Why it’s important to test for dry eye syndrome (DES) before cataract surgery
A recent study found that taking care of patients’ dry eye syndrome before cataract surgery provides them with a better external eye environment, better biometry measurements and more comfortable eyes.
Cataract surgery is highly advanced, technology-driven surgery, which promises restoration of vision in the vast majority of patients (around 96%).
We remove the natural lens of the eye, which has become clouded in cataract, using microscopic techniques and replace it with a tiny artificial lens called the intra-ocular lens (IOL).
The outcome of cataract surgery depends not only on the degree of the microscopic and lens technology plus the cataract surgeon’s skills but also on the measurements of the eye for the cataract surgery.
The tear environment at the front of the eye (called the external eye environment), and whether there is dry eye, is important.
Each patient, before cataract surgery, has to have a biometry measurement (eye measure, like a shoe measure to make sure the lens fits you) in order to ascertain the power of intraocular lens that we’re going to put in the eye.
A recent study looked at the effect of dry eye and tear osmolarity on the biometry values, which are based on measurements of the corneal curvature. They found that the drier the eye with a higher tear osmolarity, the greater chance there was of getting sequential different values for astigmatism when two consecutive measurements were taken a month apart was greater.
For patients with more normal tear osmolarity, the more likely biometry values were to be repeatable. The authors recommended that dry eyes be identified prior to cataract surgery by clinical examination and performing tear osmolarity testing at the first visit and then treating the dry eyes if dry eyes are found. The aim of this is for the patient to be more comfortable after surgery and for the biometry measurements to be more accurate.
Cataract lens biometry reading is based on the measurements of the corneal shape. The tear film forms the front layer of the cornea in real life. The surface layer of tears is the interface where light changes direction as it enters the eye to focus on the retina and it is this tear layer that is being examined when the keratometric data is being done with biometry in order to choose the intraocular lens IOL power.
The other tests were done pre-cataract include autorefraction, scanning laser ophthalmoscopy, OCT, and if needed a Pentacam examination. We add to this list testing the tear osmolarity, which can help the biometry readings to be more repeatable. At Clinica London, we do TearLab Tear Osmolarity measurements to assist detecting dry eyes.
In addition to measuring tear osmolarity, an HD analyser can be used to evaluate the optimal quality of the tear film as part of the workup. It looks at the optical scatter caused by the tear film breaking down due to evaporation; for instance where there is a rapid tear break up time and it can indicate that dry eye disease therapy is required prior to cataract surgery.
In summary, tear osmolarity is a useful test to do before cataract surgery to substantiate a clinical diagnosis of dry eye disease and to encourage patients to undergo dry eye treatment before cataract surgery. Taking care of patients’ dry eyes prior to intraocular surgery provides them with a better external eye environment, better biometry measurements and more comfortable eyes.
This blog post was based on the following paper:
Epitropoulos AT et al, Effect of Tear Osmolarity on keratometry for cataract surgery planning. J Cataract Refract Surg 2015 41 (8):1672-7.