23.1 Introduction

Purkinje images are reflections from light source formed on the surfaces of the ocular structures. In total there are four, named as Purkinje 1 to 4. P1 is the first corneal reflection and it reflects from the outer surface of the cornea. P2 reflects off the inner surface of the cornea, and P3 reflects off the outer surface of the lens. P4 reflects off the inner surface of the lens. Of the four images, P4 is the only inverted image, while the others are erect images due to how it reflects from the inner surface of the lens. Purkinje Sanson images have distinctive clinical applications like the clinical Hirschberg test, the keratometer, the videokeratography, the dual Purkinje tracker, and the biometric analysis. ^{1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11} Purkinje images have been utilized in IOL position and tilt determination as well. The technological advancements in managing the complicated ocular conditions with newer IOL designs have demanded the understanding of the possible effects of IOL oscillations in relation to their position in vivo and their effect on optical performance. The oscillations of the IOL implant after saccadic eye movements have been rarely quantified by Purkinje images in the literature. ^{12 , 13 , 14}

23.2 Detection of Pseudophacodonesis Using Purkinje Images

Purkinje images were observed through the digital slit lamp photography and video recorder (Topcon, DC-3, Tokyo, Japan) by a single examiner (DAK). Purkinje image 1 (PI) and image 2 (PII) were seen overlapped, defined, and bright. Purkinje image 4 (PIV) from the IOL was less intense, inverted, and diffuse. The motion of Purkinje image was recorded continuously at fixed frames per second while focusing on the target illumination for about 30 seconds on fixing at a fixed target and also following a horizontal saccade (▶Video 23.1).

The video was then streamed in the video editor software (Pinnacle, Studio 15, Corel Corporation) in Windows XP and the image frames showing PIV and PI were grabbed (▶Fig. 23.1). The JPEG file format was followed and evaluated by ImageJ analysis (http://rsb.info.nih.gov.easyaccess2.lib.cuhk.edu.hk/ij/) software for the difference in the position of PIV in relation to PI. After correction of geometric distortion and the preliminary edge detection, the grabbed three randomized image frames of the overall 30 seconds were included (▶Fig. 23.2). Scaling has been performed as 1 mm to be equivalent to 200 pixels using the set scale option (▶Fig. 23.3). Following this, the files for the patient were selected and the difference in positions of PIV in relation to P1 was calculated using the line tool. Measurement of the distance between PI and PIV was determined for each eye at all the three time frames (TF). The time taken for the dampening of the oscillations after the abduction saccade in seconds were also determined.

23.3 Pseudophacodonesis among Various Intraocular Lens

Out of 127 eyes included in the trial, there were capsule-fixed posterior chamber (PC) IOL, anterior chamber (AC) IOL, retropupillary iris-fixated IOL, glued trans-scleral-fixated IOL, and sutured scleral-fixated (SF) IOL. There was no statistically significant difference in PIV positions at various time points in PC IOL, AC IOL, SF IOL, and glued IOL. Iris claw lens showed a statistically significant difference in the position of Purkinje PIV at various time frames, F(2,38) = 3.80 and p = 0.0418 (▶Fig. 23.4).

The median difference in the range of movements of PIV was noted to be higher for the iris claw IOL and least for the PC IOL (▶Fig. 23.5). In comparison, of the range of difference in the PIV movements between the five groups, there was a statistically significant difference in median PIV position between the five groups, chi-square = 25.863, p = 0.0001. In subsequent comparison of post hoc analysis (Dunne test with Bonferroni correction) between the individual groups, there was a significant difference between the PC IOL and the iris claw IOL (p = 0.0001), the glued IOL and the iris claw IOL (p = 0.0020), and the AC IOL and the iris claw IOL (p = 0.0302) (▶Fig. 23.6). On comparison of the difference in the movement of PIV at rest and motion, there was a significant exaggeration of the position of PIV noted in iris claw IOL (p = 0.0395). However, there were no differences noted among PC IOL, glued IOL, AC IOL, or SF IOL. There was spontaneous suppression of oscillations noted in PC IOL, glued IOL, and AC IOL; iris claw and SF IOL showed mild delay in (1–2 seconds) after motion saccade. On dividing the IOL oscillations in relation to the movement of PIV difference as < 0.5 mm (low frequency), 0.5 to 1 mm (moderate), and ≥1 mm (severe), PC IOL about 68% (n = 34) had movement < 0.5 mm and only 2% (n = 1) had ≥1 mm. Iris claw IOL recorded the difference ≥1 mm in 55% (n = 11) and 0.5 to 1 mm in 30% (n = 6) eyes.