ASICS: Aberrometry and Straylight Measurements as an Indication for Cataract Surgery

Cataracts are a clouding of the lens of the eye. The symptoms of cataracts depend on where the clouding is in the lens and how extensive it is. Symptoms that patients may experience are blurred vision, poor vision at night, double vision in one eye, glare from backlight (such as from car headlights or a low sun), dulling of colours and a rapid change in refractive error. It is the most common cause of low vision in the world. Treatment for cataracts is surgical replacement of the cloudy lens for a clear artificial lens. The indication for cataract surgery is currently based on the visual impairment experienced by the patient, a measurement of visual acuity and the ophthalmologist's assessment of the extent to which the cloudiness of the lens explains the patient's symptoms.

Despite considering all these factors, it can be difficult for ophthalmologists to determine in advance which patient will benefit from cataract surgery. For example, visual acuity before surgery has been shown to be a poor indicator of cataract surgery outcome. There is also a limited relationship between the severity of clouding in the lens and the outcome of surgery. Questionnaires that assess patient-reported quality of vision (Patient Reported Outcome Measures, PROMs), such as the Catquest-9SF, also have limited predictability with regard to cataract surgery outcome. For example, the quality of vision of a significant number of patients who reported normal visual functioning before cataract surgery improves with surgery anyway.

In contrast, about 10% of all patients report that their visual functioning actually deteriorates with cataract surgery. There is also a limited correlation between how patients rate their change in visual functioning due to surgery in general (i.e., as much better, slightly better, no difference, slightly worse and much worse) and how patients report their visual functioning according to the Catquest-9SF. In other words, patients who report that their visual functioning after surgery felt much better than before sometimes report a worsening of their functioning with the Catquest-9SF questionnaire. It should be noted that the Catquest-9SF PROM is considered both clinically and scientifically the best questionnaire to measure change in visual functioning due to cataract surgery.

There are several reasons why patients may be dissatisfied after cataract surgery. In general, the more severe the discomfort caused by cataracts before surgery, the more satisfied patients are with the result obtained from the surgery. However, even a high percentage of patients with relatively few symptoms before surgery report having gained from the surgery after surgery. On the other hand, there is also a significant percentage of patients who deteriorate in visual function despite many complaints before surgery. The most commonly reported causes of dissatisfaction after cataract surgery with implantation of a standard artificial lens are dry eye and floaters. No research has been done on the extent to which these issues can be identified in advance.

Making the right indication for cataract surgery is important because surgery is irreversible. If the patient is dissatisfied with the result obtained, the old situation cannot be restored. Although the percentage of patients who are not satisfied after cataract surgery is small (10%), it is substantial in absolute numbers. The number of patients that is dissatisfied with the outcome of their cataract surgery corresponds to almost an entire month of cataract operations that, in retrospect, might better not have been performed.