Early post-LASIK macular and peri-optic disc
Observation of Epithelial Changes in the Optic Nerve
Wang Hongge Dong Xiaoguang Zhang Tao Wang Jinliang Tian Jingyi Fu Lijing* Studio Ophthalmology Wang Hongge
【Abstract】Objective To compare the changes in retinal volume in specific areas of the macula and the thickness of the macula and peri-optic disc optic nerve fiber layer in the early postoperative period before and after LASIK using OCT. Methods OCT was performed in 59 eyes of 31 myopic patients before and on the first day after surgery to measure the thickness of the central macular recess, the thickness of the optic nerve fiber layer above, below, nasal and temporal in four directions around the macula and optic disc, and the volume of the retina in the 6-mm diameter area of the macula. The results showed that the thickness of the optic nerve fibres in the centre of the macula and above the optic disc was thinner after LASIK compared with that before surgery, with p-values of 0.003 and 0.016 respectively, which were statistically significant. Conclusion: There was a statistically significant thinning of the thickness of the optic nerve fiber layer in the centre of the macula and above the optic disc in the early postoperative period after LASIK, while there was no statistically significant effect on the retinal volume in specific areas of the macula and the thickness of the optic nerve fiber layer in other areas around the macula and optic disc.
Keywords】Laser in situ keratomileusis, optical coherence tomography, retinal nerve fiber layer thickness
Evaluating the change of peripapillary and perimacular retinal nerve fiber layer (RNFL) in the very early stage after LASIK
WANG Hongge DONG Xiaoguang ZHANG Tao WANG Jinliang FU Lijing*
Shandong Eye Hospital, Jinan,Shandong Province PRC 250021
FU Lijing: Qingdao Municipal Hospital , Shandong Province PRC 266071
ABSTRACTS
Objective: To evaluate the influence of laser in situ keratomileusis (LASIK) on the macular retinal volume, peripapillary and perimacular retinal nerve fiber layer (RNFL) thickness assessed by optical coherence tomography (OCT) preoperatively and 1 day postoperatively.
Methods: 31 myopia patients with 59 eyes were included. The RNFL thickness and macular retinal volume measurements were performed using optical The RNFL thickness and macular retinal volume measurements were performed using optical coherence tomography (OCT) preoperatively and 1 day postoperatively. The RNFL thickness and macular retinal volume parameters were compared using paired-sample T test.
Results: the RNFL thickness of macular fovea and superior area around optic disc significantly decreased postoperatively, P value is 0.003 and 0.016 respectively; inferior average, nasal average around the disc and temporal average around macular 6mm circle increased postoperatively, but the change is not significant. Other area decreased postoperatively , No significant change was observed .
Conclusions: Laser in situ keratomileusis (LASIK) significantly decrease the RNFL thickness of central macular fovea and superior area around the But it did not significantly affect macular retinal volume and the peripapillary & perimacular retinal nerve fiber layer (RNFL) thickness. The LASIK Ophthalmologic Layer (RNFL) thickness postoperatively except the area mentioned above.
[key words】 LASIK OCT RNFLT
Laser in situ keratomileusis (LASIK) has been widely used in the treatment of myopia, but what are the effects on the vitreous retina of the drastic changes in intraocular pressure that occur during flap fabrication? The effect of LASIk on the thickness of the retinal nerve fibre layer has been observed using OCT, but no definitive conclusions have been made. In this study, we used OCT to perform preoperative and postoperative retinal optic nerve layer thickness and macular retinal volume measurements on a more comprehensive area of the retina to observe the effect of LASIK surgery on nerve fibre thickness in the optic disc and macular region.
Materials and Methods
I. Data
Thirty-one patients underwent LASIK surgery in our hospital, 17 males and 14 females; ages 18 to 36 years, mean age 21.16 years; 3 monocular, 28 binocular, total 59 eyes; spherical lens diopters -0.75 to -8.25D, mean -3.96D, of which All patients underwent LASIK surgery with the excimer laser TECHNOL S217 from Bausch & Lomb by the same surgeon, with an attraction time of 20-50 seconds, with an average of 32 seconds.
II. Methods
In addition to the usual LASIK examination, the OCT Stratus Model 3000 from Zeiss and its accompanying Version 4.0.4 (0073) software were used to measure the thickness of the retinal optic nerve layer and the volume of the retina in the macular region at specific areas, including the central macular recess, 3mm and 6mm diameters centred on the macula and 4mm diameters centred on the optic disc. The thickness of the nerve fiber layer was measured at 13 sites in four directions: above, below, temporal and nasal, and the volume of the retina in the macula was measured at 6 mm diameter. The OCT was performed on the first postoperative day by the same experienced examiner, in addition to the usual examination.
III. Statistical treatment
The data obtained preoperatively and postoperatively were analysed using paired t-tests. Statistical calculations were done using SPSS 11.5 software. p < 0.05 was considered a significant difference.
Results
Data measured using OCT, including the central macular recess, the thickness of the nerve fibre layer at a total of 13 sites in four directions, above, below, temporal and nasal to the macula at 3 mm and 6 mm diameters and at the optic disc at 4 mm diameters, and the retinal volume in the macula at 6 mm diameters, were analysed by paired t-tests. The preoperative and postoperative changes in nerve fiber layer thickness at the central macular recess (MF) were statistically significant (t=3.144, P=0.003<0.05); the preoperative and postoperative changes in nerve fiber layer thickness at the 4-mm-diameter circle above the optic disc (OD-S) were statistically significant (t=2.488, P=0.016<0.05); the changes at the remaining sites were statistically significant. There were no statistically significant pre- and post-operative changes in nerve fibre layer thickness and retinal volume in the macula within 6 mm diameter (see Table 1).
Discussion
Laser in situ keratomileusis (LASIK) has been widely used in the treatment of myopia and although its safety has been recognised by ophthalmologists and myopic patients, some minor and major complications can still occur. Of these, ocular complications have been widely studied and understood, while less research has been done on the effects on the vitreous and retina. There are reports in the literature of postoperative placental macular detachment [1], temporary macular oedema [2] and visual field damage [3], thus the effects of LASIK surgery on the vitreous and retina remain to be further investigated.
During LASIK surgery, the intraocular pressure (IOP) during flap creation can be as high as 60 mmHg or more, about 40 mmHg or more above the normal IOP, for about 20-50 seconds, with an average of 30 seconds. Previously, OCT has been used to observe the effect of LASIk on retinal nerve fiber thickness, and the postoperative observation time was usually chosen to be 1 week, 2 weeks or even 1 month after surgery [2] or 3 months [4], and the results were mostly an increase in retinal nerve fiber layer thickness after surgery than before surgery, but not statistically significant [5,7]; the observation site was mostly chosen to be in one part of the macula. What about the changes in retinal nerve fibre layer thickness in the early postoperative period? Is there any effect on the thickness of the retinal nerve fibre layer at sites other than the macula? What are the changes in retinal volume within a specific area of the macula? We therefore measured retinal nerve fibre thickness and retinal volume at several sites, including the macula and optic disc, on the first postoperative day. The results showed that retinal optic nerve fiber thickness was generally thinner on the first postoperative day than before surgery, and the degree of thinning was statistically significant at both the central macula and the superior optic disc, consistent with the reports of Tsai YY and Lin JM [6]. Due to the effect of transient ultra-high IOP, the intraocular tissues appear to change in volume and shape to adapt to the high IOP environment, while the retina adapts to the increased IOP by thinning, but the degree of change is not consistent at each site. Increases in optic nerve fibre thickness compared to preoperative levels at one week, two weeks or even one month postoperatively have been reported abroad [7] and in China [5], but are not statistically significant. In the present study and the previous results, it seems possible to speculate that different parts of the optic nerve fiber layer showed different degrees of thinning in the early postoperative period compared to the preoperative period, and that after a certain period of time, the optic nerve fiber layer gradually thickened to different degrees in response to short-term high intraocular pressure, and then returned to its preoperative thickness by a sufficient time after surgery. This change, although present, did not have a significant impact on the anatomy or function of the eye. The results of this study are therefore important for our overall understanding of the effects of transient high intraocular pressure on the retina during LASIK surgery.
References
1. Singhvi A, Dutta M, Sharma N, Bilateral serous macular detachment following laser in situ keratomileusis. Am J Ophthalmol. 2004 Dec;138(6):1069-71.
2. Yang B, Wang Z, Huang G, Transient macular edema after laser in-situ keratomileusis. Yan Ke Xue Bao. 2003 Mar;19(1):20-4.
3. Bushley DM, Parmley VC, Paglen P. Visual field defect associated with laser in situ keratomileusis[J].Am J .ophthalmol,2000,129;668-671
4. Dementyev DD, Kourenkov VV, Rodin AS, Retinal nerve fiber layer changes after LASIK evaluated with optical coherence tomography. J Refract Surg. 2005 Sep-Oct;21(5 Suppl):S623-7.
5. Chen XG, Zhao J, He Shouz et al. OCT measurement of retinal nerve fiber layer thickness before and after LASIK. Chinese Journal of Laser Medicine. 2004-11;13(4): 205-207.
6. Tsai YY, Lin JM. Effect of laser-assisted in situ keratomileusis on the retinal nerve fiber layer. Retina. 2000; 20(4):342-5.
7. Sharma N, Sony P, Gupta A, Effect of laser in situ keratomileusis and laser-assisted subepithelial keratectomy on retinal nerve fiber layer thickness . J Cataract Refract Surg. 2006 Mar;32(3):446-50.
Table 1 Comparison of OCT measurement parameters before and after LASIK surgery in 59 eyes
Department Preoperative mean (um) Postoperative mean (um) T-value P-value
MF 193.0847 189.1186 t=3.144 P=0.003
MRV 6.7620 6.7510 t=0.602 P=0.549
M3-S 273.9661 273.7457 t=0.309 P=0.759
M3-N 270.7797 269.6271 t=0.792 P=0.432
M3-I 257.5932 266.5423 t=0.092 P=0.927
M3-T 257.5932 256.3728 t=1.007 P=0.318
M6-S 253.6780 235.8475 t=1.824 P=0.073
M6-N 253.6780 253.4237 t=0.221 P=0.826
m6-i 222.8644 221.8305 t=0.524 p=0.602
M6-T 214.5593 215.2203 t=-0.617 P=0.540
OD-S 139.25 135.229 t=2.488 P=0.016
OD-N 69.42 70.65 t=-0.677 P=0.502
OD-I 135.17 136.92 t=-1.143 P=0.259
OD-T 93.5 93.35 t=-1.384 P=0.173
Note: MF: macular centre MRV: macula 6mm diameter retinal volume M3-S: macula 3mm circle above M3-N: macula 3mm circle nasal M3-I: macula 3mm circle below M3-T: macula 3mm circle temporal M6-S: macula 6mm circle above M6-N: macula 6mm circle nasal M6-I: macula 6mm circle below M6-T: macula 6mm circle temporal OD-S : optic disc 4mm round above OD-N : optic disc 4mm round nasal OD-I : optic disc 4mm round below OD-T : optic disc 4mm round temporal MVR in um3.