XXX Congress of the European Society of Cataract and Refractive Surgeons

Sleep impacted by IOLs

"There needs to be a greater awareness of the effects of cataracts and IOL implantation on the quality of sleep of our patients," asserted Dr G. Ratnarajan (Oxford Eye Hospital, Oxford, UK) during the Best of the Best session at this year's ESCRS meeting.

In his presentation, Dr Ratnarajan revealed the one month data of a comparative study examining the impact of UV-blocking or blue-filtering IOLs on sleep quality. "To give you a bit of background," he said, "the circadian rhythm regulates and coordinates multiple biological events to a specific 24hour cycle, including sleep. It's the change in quality of light particularly at dawn and dusk that is the important regulating factor of circadian rhythm."

The study

"So, we did a comparison of sleep quality in patients with visually significant cataract," said Dr Ratnarajan. The patients were evaluated before surgery and 1 month after surgery, which was the data presented at this session. The study will be continued and the patients will undergo a follow up at 12 months post-op as well.

Two patient groups were formed, one at the Oxford Eye Hospital (Oxford, UK) and the other at the Prince Charles Eye Unit (Windsor, UK). Patients at the first location received the UV-blocking lens, AcrySof SA60AT (Alcon Laboratories, Fort Worth, Texas, USA), and those in the latter location received the blue-filtering lens, AcrySof IQ SN60AT (Alcon Laboratories).

"Demographic information was collected on patients as well as their best-corrected visual acuity (BCVA) in either eye and presence of any co-existent pathology," added Dr Ratnarajan. The team used the Pittsburgh Sleep Quality Index (PSQI) questionnaire to evaluate the patients at each visit. "It's a well-established and validated sleep study questionnaire and is based on seven parameters of sleep function... it also gives a global sleep function and a score of greater than 5 would indicate poor sleep," he said.

Results

The two cohorts were well matched with regards to age, gender and presence of any existing ocular co-morbidities explained Dr Ratnarajan. "The baseline pre-op visual acuity (VA) was slightly better in the UV-blocking IOL group and we deemed good VA to be 6/9 or better," he continued. "In both groups, 49% of patients were reported to have a PSQI of greater than 5 and so were classified as poor sleepers. The mean score was slightly higher in the blue-filtering group compared with the UV-blocking group."

At the postoperative 1month visit Dr Ratnarajan noted that there was a highly statistically significant improvement in the PSQI score for the UV-blocking IOL group, which went from 6.4 to 5.64. However, the bluefiltering IOL group did not perform as well although an improvement between pre-op and 1-month post-op scores was still seen. He went on to reveal that the UV-blocking IOL group experienced statistically significant improvements in sleep quality, sleep latency (time taken to fall asleep) as well as sleep duration whereas the blue-filtering IOL group demonstrated a significant improvement in sleep duration alone.

Performing a sub-analysis based on the pre-op VA, Dr Ratnarajan noted an interesting trend. "In the UV-blocking group those with good pre-op VA did demonstrate a statistically significant improvement in sleep but it was those patients with the poor pre-op VA that benefitted more. Interestingly, in the blue-filtering IOL group this pre-op VA made no difference," he said.

Difference in lens type

"In summary, poor sleep is common, affecting half the patients presenting for cataract surgery," Dr Ratnarajan confirmed. "We saw a statistically significant improvement after 1-month with a UV-blocking IOL, particularly in those with poor pre-op VA, the blue-light filtering IOL did not demonstrate the same improvement and there was no correlation with the pre-op VA." This is the first study to demonstrate a difference between lens types and the results were unexpected in that previously it has been thought that the type of IOL would not have an impact on sleep.

Dr Ratnarajan emphasized the importance of awareness of these findings particularly for patients with known sleep disturbances living in poorly lit environments who may benefit more greatly from a clear lens implantation. "This work is on going, we are looking at the results after 12 months as well as the effect on pupil size, which will hopefully give us more information," he concluded.

Dr Ratnarajan has indicated that travel had been funded (fully or partially) by one of the companies mentioned within this piece.

Measuring LCA of IOLs

According to Professor Susana Marcos, "Aberrometry at different wavelengths allows us objective in vivo measurements of the LCA in eyes implanted with IOLs as well as the impact of longitudinal chromatic aberration (LCA) on image quality." Prof. Marcos (Visual Optics & Biophotonics Lab, Institute of Optics, Madrid, Spain) discussed her study on measuring chromatic aberrations of IOLs in vivo during the second day of this year's ESCRS symposium.