SURGERY OUTCOMES

Although there are many evidence-based strategies for preventing dissatisfaction in patients who undergo surgery for cataracts, there may remain some causes of dissatisfaction that are as yet not possible to predict or prevent, according to participants in a debate at the 17th ESCRS Winter Meeting. Visual acuity alone is not a complete outcome measure for patients undergoing cataract surgery, since many who have a visual acuity of 20/20 are still unhappy with their vision, said Mats Lundström MD, PhD, EyeNet Sweden, Blekinge Hospital, Karlskrona, Sweden.

“Snellen visual acuity is not the whole picture. We are not operating on eyes that are walking on two legs, we are operating on human beings. They are not only seeking our help to achieve visual acuity, they seek our help so they can see to read, watch TV, recognise faces and so forth. So why not use the patient reported outcome as a measure of success in cataract surgery?†he asked.

He noted that the task of the Swedish cataract registry has been the development of the Catquest- 9SF questionnaire. It asks patients about their activity limitations in daily life that may be related to vision. “This sort of second-generation questionnaire is a valid measure of visual function. So we have to forget the talk about soft data and hard data. This is really hard data. This questionnaire has been evaluated and compared with 15 other cataract surgery outcome questionnaires and in fact it has been found to be highly responsive and easy to use,†Dr Lundström said. He noted that he and his associates have used the CATQUEST-9SF questionnaire to identify risk factors for poor patient-reported outcomes. The risk factors they identified include ocular co-morbidities, surgical and postoperative complications. Another risk factor they identified for postoperative visual dissatisfaction was having satisfactory vision before surgery.

Most recently, Dr Lundström and his associates conducted a study in which they looked at 10,979 patients operated between 2008 and 2011 who completed the Catquest-9SF questionnaire before and after surgery. They found that 857 patients (7.8 per cent) had no benefit meaning they had more problems after surgery than before. Among those patients, 245 had a final distance corrected vision of 20/20 and yet were still unhappy. Or, to look at it another way, among those patients with 20/20 vision, 4,947 had benefit but 245 were without benefit.

A comparison of the 20/20 and unhappy patients with the 20/20 and happy patients showed the unhappy patients were more satisfied with their vision and have fewer symptoms and had better near vision before surgery. One of the major causes of unhappiness after uncomplicated cataract surgery is the presence of dysphotopsias, said Ian Dooley MRCOphth, MSc, Royal Eye and Ear Hospital, Dublin, Ireland. “Dysphotopsias cause significant distress to patients, both physically and mentally. There are no diagnostic signs or tests. They are diagnosed clinically based on patients’ symptoms,†he said.

Dysphotopsias, which are present in about three per cent of patients at one year postoperatively, include any light-related visual phenomenon which produces unwanted patterns on the retina of phakic or pseudophakic patients. There are positive dysphotopsias, which are bright artifacts of arc, streaks and halo and negative dysphotopsias, which have the appearance of a dark shadow, typically arc-shaped in the temporal field. There are devices which detect the amount of stray light hitting the retina. They include C-Quant Nykotest 300. However, in one recently published study (Kinard et al. J Cataract Refract Surg 2013, DOI: 10.1016/j.jcrs.2012.11.023) straylight scatter did not correlate with levels or visual satisfaction measured by the VF 11R questionnaire developed by Dr Konrad Pesudovs' team. (Measuring outcomes of cataract surgery using the Visual Function Index-14. Gothwal VK, Wright TA, Lamoureux EL, Pesudovs K. J Cataract Refract Surg. 2010 Jul;36(7):1181-8. doi: 10.1016/j.jcrs.2010.01.029. PMID: 20610098 [PubMed - indexed for MEDLINE].)

 In the absence of objective measurements, questionnaires like the NEI VF 11R are the best way of detecting patients’ dysphotopsias, he said.

Causes and remedies
Positive dysphotopsia appear to result from the square edge of an IOL, which reflects peripheral light rays toward the retinal periphery. They are more common with hydrophobic acrylic IOLs with higher refractive index. Raytracing studies suggest that rounding the corners should reduce glare by around 90 per cent. A frosted or textured edge should also reduce the internal light scatter. Negative dysphotopsias may result from a reflection of the anterior capsulorhexis edge projected onto nasal peripheral retina or from a discontinuity of nasal retinal illumination related to a square-edged optic. Anatomic factors associated with chronic negative dysphotopsia are a small pupil, more anterior extension of the functional nasal retina and increased distance between the iris and IOL plane.

The spontaneous improvement that occurs in most cases may result from opacification of the nasal anterior capsule, which reduces the intensity of chronic negative dysphotopsia. Neuroadaptation may also play a role, Dr Dooley said. Using a textured edge optic for IOL exchange or as the primary IOL in the second eye lowers the incidence of both positive and negative dysphotopsia. “Patients should be counselled regarding these possible symptoms preoperatively. Patients appreciate knowing that their problem is understood and that remedial options are available,†Dr Dooley concluded.