Changes in Macula Lutea Following Nd: YAG Laser Capsulotomy in OCT Imaging

Uncomplicated cataract surgery with intra ocular lens (IOL) implantation cannot guarantee definitive and stable solution for permanent improving of visual acuity (VA). VA can decrease after certain period. Impairment of vision as a late result after cataract surgery can be due to various reasons (Cystoid macular edema (CME)– Irvine-Gass syndrome, retinal detachment, uveitis, TLS toxic lens syndrome). One of the most frequent results of cataract surgery with IOL implantation is posterior capsule opacification (PCO)–secondary cataract.


Introduction
Uncomplicated cataract surgery with intra ocular lens (IOL) implantation cannot guarantee definitive and stable solution for permanent improving of visual acuity (VA). VA can decrease after certain period. Impairment of vision as a late result after cataract surgery can be due to various reasons (Cystoid macular edema (CME)-Irvine-Gass syndrome, retinal detachment, uveitis, TLS -toxic lens syndrome). One of the most frequent results of cataract surgery with IOL implantation is posterior capsule opacification (PCO)-secondary cataract.
Surgical method requires irrigation/aspiration (I/A) system to "clean" posterior capsule. This method is chosen when Elschnig pearls are present on the posterior capsule. Removing of cell aggregations from the posterior capsule will not get rid the patient of the problem completely because cells from periphery are able to return to the centre. Non invasive method is an alternative to surgical procedure Nd:YAG laser capsulotomy (Neodynium-Yttrium-Aluminium-Garnet -Nd:Y 3 Al 5 O 12 ) is a method using emitted energy from a crystal, that is bombed by Neodymium particles. The aim of Nd:YAG laser capsulectomy is to remove the secondary cataract by opening (by transfixion) the posterior capsule in centre. Energy pulses with wavelength of 1064 nm and flashes with duration of nanoseconds create a shockwaves effect (acoustic gradient) as well as a short thermic effect in place of focus. Because of acoustic wave is the posterior lens capsule opened by photo disruption of the tissue [1][2][3]. This effect is called noninvasive trauma with photochemical and ionising effect. The result is opening in the centre of posterior capsule with diameter cca 4 mm. The acoustic energy from the capsule is transmitted with vitreous to the retina trough adhered vitreous cortex. Energy from YAG laser capsulotomy can damage retinal [4] tissue by thermal photocoagulation and especially has influence on central part of retina by changing foveal minimal thickness (FMT) [1,5]. Turkish authors report a paper of long Abstract Objectives: To evaluate functional and anatomical changes in macular region after Nd:YAG capsulotomy.
Background: Optical coherence tomography (OCT) enables to visualize, compare and evaluate macular region of retina.

Conclusion:
Nd:YAG capsulotomy is safe method to remove posterior capsule opacification and improve BCVA. FMT and MV are sensitive parameters that correlate with BCVA. Changes in FMT and MV were nonsignificant.
term follow up after Nd:YAG caplsulotomy without significant changes of foveal thickness [6].
With use of optical coherent tomography (OCT) we are able to measure FMT of the retina, visualize retinal layers, compare dynamic changes in macular region in time. The objective is to evaluate the influence of Nd:YAG laser energy on the central macula regionespecially fovea and the impact on best corrected visual acuity (BCVA) and intra ocular pressure (IOP).

Methods
Our prospective study group included 36 patients, 17 male and 19 female (40 eyes) in average age 78.2 ±13 years with secondary cataract after uncomplicated cataract surgery. Group was treated with Nd:YAG capsulotomy. Inclusion criteria were slit lamp confirmed findings of fibrotic PCO, without presence of other pathological processes in the eye. Examination and procedure were performed on outpatient basis. Patient with dilated pupil were treated by Nd:YAG laser capsulotomy with "X" shaped opening of the posterior capsule. 10-20 pulses were used to create 4 mm opening. After treatment patients administer Diclophenacum natricum eye drops QID for 3 weeks. 30 minutes after treatment stenopeic BCVA and IOP were examined. FMT and macular volume (MV) in 6 mm diameter were analysed with OCT (Stratus III, treatment to 189.63 ± 11 µm. Macular volume values in day one were 6.53 ± 0.5 mm 3 and one month after 6.51 ± 0.44 mm 3 in average. Used average Ng:YAG energy was 72.35 mJ ± 47.04. OCT examination of the posterior pole in day one and one month later showed decrease of average FMT and average MV without statistically significant values in both parameters (p=0.141, p<0.817). BCVA changes did not correlate with changes in FMT and MV. Comparing our results with literature we came to similar results published in medical journals. Total average energy, number of laser shots or mean energy per shot did not affect the foveal thickness or macular volume [6].

Conclusions
Nd:YAG capsulotomy is safe method for treatment of posterior capsule opacification. Foveal minimal thickness and macular volume are sensitive indicators that may correlate with BCVA. Nonsignificant changes in FMT and MV do not correlate with BCVA. In one month follow up in our study were no complications like retinal detachment, CME or increase of IOP in patients [7,8]. Patients continue follow up in our outpatients department.