Effect Of Implantation Of Intrastromal Rings For Treating Keratoconus On Mesopic Visual Function

Abstract

Purpose: : To evaluate the changes after surgery for treating keratoconus with intrastromal rings in mesopic contrast sensitivity and visual acuity and its relationship with the pupil diameter, before and three months after surgery

Methods: : 45 eyes of 35 patients, ranging between 15 and 45 years and a pupil diameter in mesopic conditions equal to or greater than 5mm, who had completed 3 months of follow-up were evaluated. All cases were diagnosed with keratoconus and implanted with intracorneal segments to 5 mm from the visual axis by manual system by following the manufacturer's standards from each nomogram. Differences between preoperative and postoperative logMAR uncorrected visual acuity (UCVA), photopic and mesopic (0.1 to 0.2 cd/m2) visual acuity with best correction in spectacles (BSCVA) using high (96%) and low contrast (10%) charts, photopic and mesopic contrast sensitivity (CS) with the Pelli-Robson Test, were statistically assessed

Results: : No significant differences were found between preoperative and postoperative mesopic values: high contrast visual acuity change (Mean -0.1 ± 0.4), low contrast visual acuity change (Mean 0.1 ± 0.5) and contrast sensitivity change (Mean 0.1 ± 0.4). A worsened of mesopic high contrast VA change correlated significantly with increased pupil diameter. Photopic values showed significant decrease in spherical equivalent change (Mean 3.1 ± 4.2), and improved values in high contrast BSCVA (Mean -0.1 ± 0.3), low contrast BSCVA (Mean-0.1 ± 0.3), SC (Mean 0.1 ± 0.3) and UCVA (Mean -0.4 ± 0.1)

Conclusions: : Contrary to what might be thought given that the rings were implanted to 5 mm from the visual axis, overlapping the midriatic pupil, the changes in the mesopic high and low contrast visual acuity and contrast sensitivity were not statistically significant. Postoperative photopic values (pupil diameter less than 4 mm) were significantly better than preoperative

Keywords: keratoconus • contrast sensitivity