J Huazhong Univ Sci Technolog Med Sci. 2006;26(3):372-3, 377.

Liu L, Lei C, Li X, Dong J.

Refract Surgery Center Tongji Hospital, Tongji Medical College, Huazhong university of Science and Technology, Wuhan 430030, China.

Changes of corneal properties induced by laser in situ keratomileusis (LASIK) results in low inaccurate intraocular pressure (IOP) readings by Goldmann applanation tonometry (GAT). Before and after LASIK, the applied value of IOP, measured by dynamic contour tonometry (DCT) in comparison to GAT, was evaluated. Before and 1, 4 weeks after LASIK, the IOP in 30 cases (60 eyes) was measured by GAT and DCT respectively. The obtained results were statistically processed by SPSS11.5 statistical software. The results showed that central corneal thickness (CCT) could affect GAT measurements but not DCT measurements. The comparison of IOP one and 4 weeks after LASIK revealed that the readings from GAT was separately decreased by 5.00 +/- 1.12 and 5.45 +/- 1.13 mmHg as compared with those before LASIK, while those from DCT had no significant difference. It was concluded that LASIK-induced changes of CCT could influence the accuracy of GAT measurements, but had no influence on those from DCT. DCT was more beneficial to the measurements of IOP in normal eyes and those subject to LASIK surgery.

http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijovs/vol3n1/lasik.xml
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Excerpts: follow link to see full text for tables.

Citation:

Maurício Flank, Niro Kasahara, Maurício Della Paolera, Ralph Cohen, Jorge Mitre, Fernando Maluf, Carmo Mandia, Geraldo Vicente de Almeida: Retinal Nerve Fiber Layer Thickness Change after Photorefractive Surgery. The Internet Journal of Ophthalmology and Visual Science. 2004. Volume 3 Number 1.
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Abstract

Purpose: to analyze the retinal nerve fiber layer (RNFL) change after photorefractive surgery.
Methods: Forty-four eyes of 29 patients had RNFL measured by scanning laser polarimetry (SLP) before and after photorefractive surgery. Patients were divided in 3 groups: PRK group (10 eyes), low myopic LASIK group (17 eyes) and moderate myopic LASIK group (17 eyes). Pre and postoperative mean RNFL thickness (total and per quadrant) and 14 SLP parameters were compared with the Wilcoxon and Mann-Whitney tests.

Results: In the PRK group, total mean and inferior mean thickness decreased after surgery. Five parameters were changed after the procedure. In the low myopic LASIK group all mean RNFL thickness decreased and 4 parameters changed after surgery. In the moderate myopic LASIK group all mean RNFL thickness decreased and 5 parameters were changed after surgery. The mean decrease in the RNFL thickness seen in both LASIK groups were statistically different from PRK group (P<0.01).

Conclusion: Our results show that RNFL thickness decreases after photorefractive surgery as measured by SLP.

Introduction
Subtle anatomic changes in the neural rim and the retinal nerve fiber layer (RNFL) are believed to precede visual field changes in glaucoma patients. In order to objectively evaluate changes in the RNFL, new methods have been developed. Scanning laser polarimetry (SLP) is one of these new technologies and it has been used in the diagnosis and follow-up of glaucomatous patients and suspects. 1 , 2 , 3 , 4 , 5 SLP works based on the principle that polarized light passing through the RNFL (a birefringent medium) undergo a measurable phase shift proportional to the thickness of the tissue.

Recent reports suggest that laser-assisted in situ keratomileusis (LASIK) can interfere with SLP measurements by affecting corneal birefringence, an intrinsic tissue property. 6 , 7 , 8 , 9 .

The purpose of this study is to analyze the RNFL changes after photorefractive surgery and to compare proportional changes between LASIK and photorefractive keratectomy (PRK).

Material and Methods
Forty-four eyes of 29 patients scheduled for refractive surgery at the Sao Paulo Eye Hospital were enrolled. All surgeries were performed by 2 surgeons (JM and FM) from January to June, 2001. Patients were informed about the risks of the procedure and signed informed consent. The procedures followed were in accordance with the Helsinki Declaration of 1075, as revised in 1983. All patients were white, 16 (55.1 percent) were male and 13 (44.9 percent) female. They were divided in 3 groups, according to the surgical technique and degree of myopia in PRK, LASIK I (low myopic) and LASIK II (moderate myopic).

The PRK group comprised 10 eyes of 5 patients. The mean age group was 38.8 +/- 8.8 years (range, 26 to 48 ), mean preoperative spherical equivalent was -1.9 +/-0.4 diopters (range, -1.00 to -2.75), and the mean tissue ablation was 32.2 +/- 16.0 µm (range, 9 to 59). The low myopic group comprised 17 eyes (10 patients) with mean preoperative spherical equivalent up to - 4.00 diopters ( - 2.53 +/- 0.9, range - 0.75 to - 4.00). The mean age was 32.9 +/- 6.8 years (range, 24 to 50), and the mean tissue ablation was 49.7 +/- 11.0 µm (range, 28 to 58 ). The moderate myopic group comprised 17 eyes (14 patients) with preoperative spherical equivalent from - 4.25 diopters and up (- 7.19 +/- 1.88, range, - 5.00 to -10.00). The mean age was 33.2 +/-7.7 years (range, 21 to 47), and the mean tissue ablation was 90.5 +/- 20.0 µm (range, 66 to 133).

Preoperatively all patients underwent a complete ophthalmologic examination including, refractometry, biomicroscopy, aplanation tonometry, indirect ophthalmoscopy, pachimetry, corneal topography, and retinal nerve fiber layer analysis with the scanning laser polarimeter (GDx ® version 2.0.08, Laser Diagnostic Technology, San Diego, CA, USA).

Briefly, the surgical technique for LASIK involved the creation of a corneal flap (160 µm or 180 µm, at the surgeon discretion) with the Hansatome® (Bausch & Lomb Surgical, Claremont, CA, USA). A flying-spot ablation was performed on corneal stroma with the Technolas Keracor 117 C excimer laser (Bausch & Lomb Surgical, Claremont, CA, USA), using a variable optical zone (4.5 mm to 6.0 mm) individualized for each eye. The corneal flap was then repositioned, the interface irrigated with balanced saline solution and let it air dry for at least 3 minutes. A bandage contact lens was placed in the operated eye for at least 12 h and the patient was instructed to use tobramicin 0.3 percent and dexamethasone 0.1 percent (Tobradex®, Alcon Laboratories, INC., Fort Worth, TX, USA) q.i.d. for 1 week.

The PRK procedure started with a removal of the previously demarcated corneal epithelium to a diameter of 7.0 mm. A flying-spot laser ablation was done with the Technolas Keracor 117 C excimer laser (Bausch & Lomb Surgical, Claremont, CA, USA) and a bandage contact lens was placed. Postoperatively, patients were instructed to take tobramicin 0.3% and dexamethasone 0.1 percent (Tobradex®, Alcon Laboratories, INC., Fort Worth, TX, USA) q.i.d. for 3 days and diclofenac 0.1 percent (Voltaren®, Novartis Ophthalmics, Duluth, GA, USA) q.i.d. for 24 h. On postoperative day 3, the bandage contact lens was removed and patients started using fluoromethasone 0.1% (Florate®, Alcon Laboratories, INC., Fort Worth, TX, USA) q.i.d. for one month.

SLP was repeated from one to 10 weeks after the surgical procedure. Three good quality pictures were taken from each eye by the same operator and the mean of the 3 was used for analysis. In the mean image, a ellipse set at 1.75 times the disk diameter was drawn concentric to the disk margin. The preoperative image was set as reference.

Pre and postoperative values of mean RNFL thickness (total and per each of the 4 quadrants) and SLP parameters included in the GDx® software version 2.0.08 (symmetry, superior ratio, inferior ratio, superior/nasal, maximum modulation, average thickness, ellipse modulation, ellipse average, superior average, inferior average and superior integral) were compared. Definition of each parameter has been described elsewhere. 10 Wilcoxon test was used to compare pre and postoperative data within the groups and Mann-Whitney test was used to compared the Δ% values of each group (Δ% = pre - postoperative / pre X 100). A P value of less than 0.05 was considered to be statistically significant.

Results
Table 1 shows the mean pre and mean RNFL thickness difference among PRK group, LASIK I (low myopic) group and LASIK II (moderate myopic) group. All quadrants showed statistically significant difference for LASIK I and LASIK II groups, whereas, for the PRK group, mean total and mean inferior quadrant showed significant difference.

Discussion
This study is the only that compared PRK and LASIK changes in SLP results. The results of this study concur with previous publish studies. Gürses-Özden et al. found that total mean RNFL and superior, inferior, temporal and nasal mean RNFL were thinner after LASIK in 13 eyes. 6 Tsai et al., evaluating 35 eyes, noted the postoperative integrals and averages of RNFL thickness were statistically significantly lower than preoperative values in all quadrants, except in the temporal one. 8 Roberts et al. noted that six of 12 retinal nerve fiber layer thickness measurements showed significant change in 30 eyes, one week after LASIK. 9 However, there was no correlation with corneal ablation depth for all parameters. In a larger series of patients, Kook et al. found the mean postoperative retardation values of all sectors and of the superior, temporal, inferior and nasal sectors showed reduced RNFL thickness. 7

Most authors agree that RNFL thickness changes after LASIK is caused by the structural changes determined by ablation of tissue from the anterior stroma in central cornea. 6 , 7 , 8 , 9 Such ablation affects the form-birefringent properties of the cornea to a point to change RNFL thickness measurements by SLP. It is unlikely that the transient elevated IOP during the microkeratome pass caused true nerve fiber loss. Although reaching values over 50 mmHg, the IOP elevation lasts less than 30 seconds. Besides, the time period between the surgery and the second SLP measurement, which was one or two weeks in some patients, seems too short to allow apoptosis of the retinal ganglion cell take place causing axon loss and be noticed by means of SLP. Nevertheless, Bushley et al. report a case of visual field defect associated with LASIK. 12 The near superior altitudinal defect correlated with an infero-temporal notch. They believe that increased IOP associated with the microkeratome ring used during LASIK may have precipitated optic nerve head ischemia and visual field defect. This case is an exception to the rule and highlights the importance of discussing this unusual complication in glaucomatous patients.

Choplin et al. found no significant effect of excimer laser PRK on RNFL thickness measurements in a group of 13 patients with moderate myopia. 13 In their study, the pre and postoperative RNFL thickness measurements were not compared. Conversely, in our study, we found total mean and inferior RNFL thinning in the PRK group and 5 parameters changed after the procedure. The SLP measurements changes in PRK patients suggests that RNFL thinning does not represent true loss.

In our study we decided to compare the RNFL changes seen after refractive surgery according to the surgical technique. LASIK seemed to cause more thinning in the RNFL and SLP parameters changes than PRK. When comparing low and moderate myopic groups only one parameter (superior integral) was different between groups, whereas no difference was found in the RNFL thickness measures suggesting that the amount of corneal tissue ablation does not influence the retardation measurements. This is in agreement with Roberts et al. that found no correlation with corneal ablation depth for all parameters. 9

A new version of SLP with variable corneal polarization compensation (VCC) is now available. Weinreb et al. compared the ability of SLP to discriminate between healthy and glaucomatous eyes with fixed corneal polarization magnitude and VCC. 14 The authors noticed that VCC can improve the ability to discriminate between healthy and glaucomatous eyes. Even though the correction for corneal polarization compensation with VCC looks promising, whether these measurements can be influenced by photorefractive surgery, or not, is yet to be determined.

In conclusion, our study shows that both PRK and LASIK can influence SPL measurements. This effect is most probably caused by structural changes in the corneal stroma as a result of excimer laser ablation.

Address for correspondence
Mauricio Flank, MD
Rua Dr. Homem de Melo, 1186, suite 112
São Paulo – SP
05007-002
Brazil
FAX: (55-11-6979-3588)

References
1. Weinreb RN, Shakiba S, Zangwill L. Scanning laser polarimetry to measure the nerve fiber layer of normal and glaucomatous eyes. Am J Ophthalmol 1995; 119: 627-636.

2. Niessen AGJE, van den Berg TJTP, Langerhorst CT, Greve EL. Retinal nerve fober layer assessment by scanning laser polarimetry and standardized photography. Am J Ophthalmol 1996; 121: 484-492.

3. Weinreb RN, Zangwill L, Berry CC, Bathija R, Sample PA. Detection of glaucoma with scanning laser polarimetry. Arch Ophthalmol 1998; 116: 1583-1589.

4. Choplin NT, Lundy DC, Dreher AW. Differentiating patients with glaucoma from glaucoma suspects and normal subjects by nerve fiber layer assessment with scanning laser polarimetry. Ophthalmol 1998: 105: 2068-2076.

5. Lee VW, Mok KH. Retinal nerve fiber layer measurement by nerve fiber analyzer in normal subjects and patients with glaucoma. Ophthalmol 1999: 106: 1006-1008.

6. Gürses-Özden R, Pons ME, Barbieri C, Ishikawa H, Buxton DF, Liebmann JM, et al. Scanning laser polarimetry measurements after laser-assisted in situ keratomileusis. Am J Ophthalmol 2000; 129: 461-464.

7. Tsai YY, Lin JM. Effect of laser-assisted in situ keratomileusis on the retinal nerve fiber layer. Retina 2000; 20: 342-5.

8. Kook MS, Lee S, Tchah H, Sung K, Park R, Kim K. Effect of laser in situ keratomileusis on retinal nerve fiber layer thickness measurements by scanning laser polarimetry. J Cataract Refract Surg 2002: 28: 670-675.

9. Roberts TV, Lawless MA, Rogers CM, Sutton GL, Domniz Y. The Effect of Laser-Assisted In Situ Keratomileusis on Retinal Nerve Fiber Layer Measurements Obtained with Scanning Laser Polarimetry. J Glaucoma 2002; 11:173-176.

10. Nerve Fiber Analyzer System Manual. Laser Diagnostic Technilogies, Inc., San Diego, CA, USA, 1996.

11. Greenfield DS, Knighton RW, Huang XR. Effect of corneal polarization axis on assessment of retinal nerve fiber layer by scanning laser polarimetry. Am J Ophthalmol 2000; 129: 715-722.

12. Bushley DM, Parmley VC, Paglen P. Visual field defect associated with laser in situ keratomileusis. Am J Ophthalmol 2000; 129: 668-671.

13. Choplin NT, Schallhorn SC. The effect of excimer laser photorefractive keratectomy for myopia on nerve fiber layer thickness measurements as determined by scanning laser polarimetry. Ophthalmol 1999: 106: 1019-1023.

14. Wienreb RN, Bowd C, Zangwill LM. Glaucoma detection using scanning laser polarimetry with variable corneal polarization compensation. Arch Ophthalmol 2002; 120: 218-224.

J Cataract Refract Surg 2002; 28:2117-2122

Michele Iester, MD, Patrick Tizte, MD, André Mermoud, MD 

Purpose: To determine whether the increase in intraocular pressure (IOP) for 45 seconds during laser in situ keratomileusis (LASIK) suction can induce a decrease in retinal nerve fiber layer thickness (RNFLT) assessed by a confocal scanning laser polarimeter.  

Setting: Jules Gonin Hospital, University of Lausanne, Lausanne, Switzerland.  

Methods: Eleven normal volunteers were enrolled in the study. The optic disc of each eye was analyzed by the GDx® Nerve Fiber Analyzer (Laser Diagnostic Technologies, Inc.), version 1.0.14. Using the standard circle that appears as a 10-pixel green circle on the GDx display, the system assessed the RNFLT at 1.75 disc diameter from the outer edge of the optic nerve head. To further evaluate the possible retinal nerve fiber layer (RNFL) loss, the 360-degree circumference was divided into 36 segments measuring 10 degrees each and the RNFLT was calculated for each sector. All subjects had a GDx assessment before 100 mm Hg ocular compression of 1 eye for 45 seconds and then 2 minutes and 1 month after compression.  

Results: Before compression, the mean RNFLT was 69.09 μm ± 10.96 (SD); it was 69.27 ± 10.98 μm after 2 minutes and 67.00 ± 10.58 μm after 1 month. No statistically significant difference was found between the before and after measurements.  

Conclusion: A 45-second acute increase in IOP, such as during LASIK suction, did not decrease the RNFLT in normal eyes.

Am J Ophthalmol. 2004 Oct;138(4):657-9.

Principe AH, Lin DY, Small KW, Aldave AJ.

Cornea Service, Jules Stein Eye Institute, University of California Los Angeles Medical Center, Los Angeles, California 90095, USA.

PURPOSE: To report the first case of macular hemorrhage following laser in situ keratomileusis (LASIK) with femtosecond laser flap creation.

DESIGN: Observational case report.

METHODS: A 36-year-old woman underwent uncomplicated, bilateral, simultaneous LASIK procedures for correction of moderate myopia (-5.00 diopters OD and -6.00 diopters OS). LASIK flap creation was performed using the IntraLase femtosecond laser.

RESULTS: On postoperative day 1, the patient's uncorrected and best-corrected visual acuities were 20/20 OD and 20/40 OS. A dilated fundoscopic examination revealed a one-third disk diameter macular hemorrhage OS. An intravenous fluorescein angoiogram ruled out the presence of predisposing macular pathology. Two months after LASIK, the macular hemorrhage had cleared, and 6 months later, the BCVA improved to 20/25 OS.

CONCLUSIONS: Macular hemorrhage may occur after LASIK, even in the absence of previously identified risk factors, such as high myopia, pre-existing choroidal neovasculaization, lacquer cracks, and sudden changes in intraocular pressure associated with microkeratome-assisted flap creation.

This is from the Handbook of Ocular Disease Management

http://www.revoptom.com/handbook/sect5e.htm

And illustrates an important point that lattice degeneration is quite common, occuring in 8-11 percent of the population. Since this condition predisposes the retina to weakening tearing and detaching yet is simple to diagnose, it is straightforward that patients with this condition should not be exposed to the ocular trauma associated with the suction ring during LASIK.  

SIGNS AND SYMPTOMS - The patient is usually over age 20 and is nearly always asymptomatic, except for possible complaints of flashing lights (photopsia). There appears to be a higher incidence of myopia in patients with lattice degeneration. There is no racial or sexual predilection.  Lattice degeneration occurs in eight to 11 percent of the general population. It presents as a linear trail of fibrosed vessels within atrophied retina in a "lattice" pattern. It nearly always runs circumferentially between the equator and the ora serrata. The individual lesions are usually from one-half to six disc diameters and may run 360 degrees around the eye in a discontinuous pattern. There may be associated RPE hyperplasia, giving the lesion a pigmented appearance. Atrophic holes are often present in the lesion, occasionally large enough to encompass the entire lattice lesion. The incidence of atrophic holes in lattice degeneration ranges from 18 to 42 percent. A tractional linear tear will occur on the posterior edge of lattice lesions in 1.9 percent of lesions. Lattice degeneration is typically bilateral.  

PATHOPHYSIOLOGY - The etiology of lattice is questionable. It appears to be due to dropout of peripheral retinal capillaries with resulting ischemia, which induces thinning of all retinal layers. There is sclerosis of the larger vessels, with their lumen being filled with extracellular glial tissue, giving lattice degeneration its characteristic fibrotic appearance.  The retinal thinning has several effects:

(1) the overlying vitreous will be disturbed, resulting in a pocket of liquefaction overlying the lattice lesion known as a lacuna;

(2) the vitreous along the edges of the lattice lesion will undergo strong adhesion to the retina; and

(3) the ischemia and retinal thinning will disturb the retinal pigment epithelium, resulting in RPE hyperplasia and a pigmented appearance.  

Often the thinning becomes so profound that a full-thickness hole atrophies through the retina at the lattice lesion. The overlying liquefied vitreous has the ability to pass through the hole into the subretinal space and possibly lead to rhegmatogenous retinal detachment. This will occur in approximately two percent of cases of holes within lattice degeneration. Due to the liquefaction of the overlying vitreous, there is no vitreoretinal traction on the edges of a hole in lattice degeneration. If a posterior vitreous detachment occurs, the vitreoretinal traction along the posterior edge of a lattice lesion may result in a linear tear, with an ensuing progression to rhegmatogenous retinal detachment in 37 percent of cases.  

MANAGEMENT - The main concern with lattice degeneration is the chance of progression to rhegmatogenous retinal detachment. With many types of retinal breaks, the area is often prophylactically sealed with laser photocoagulation or cryoretinopexy to prevent this. In lattice degeneration alone, prophylactic treatment is not practical in that the risk of detachment is only 0.1 to 0.7 percent in the phakic eye. Atrophic holes in phakic eyes with lattice degeneration also do not require prophylactic treatment, as the risk of progression to detachment is two percent or less.  Furthermore, prophylactic treatment of lattice lesions in eyes with greater than 6.00D of myopia yields no benefit. These lesions need only routine, yearly monitoring with the patient educated about signs and symptoms of retinal detachment. However, a linear tractional tear forming at the posterior border of a lattice lesion has about a 37 percent risk of progression to retinal detachment and therefore should receive prophylactic therapy.  

CLINICAL PEARLS  - Lattice degeneration both with and without atrophic holes is generally benign and does not require prophylactic treatment, as the complications of treatment are more severe than the natural history of the untreated condition.  The ominous tractional tear at the posterior border of a lattice lesion is very difficult to see ophthalmoscopically. These tears will usually only become apparent upon scleral indentation. Perform scleral indentation, whenever possible, on every lattice lesion to look for an occult tractional tear.

J Refract Surg. 2005 Sep-Oct;21(5):501-4.

Lin JM, Tsai YY.  Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan.  

PURPOSE: To report a case of retinal phlebitis with cystoid macular edema in both eyes 8 weeks after LASIK.  

METHODS: A 30-year-old woman underwent bilateral myopic LASIK. Eight weeks postoperatively, the patient experienced blurred vision in the left and right eyes. Fundus examination showed focal whitish patches in the parafoveal and juxtafoveal areas and lack of foveal reflex in both eyes. A diagnosis of retinal phlebitis with cystoid macular edema was made, which was treated with oral corticosteroids with tapering dose.  

RESULTS: Visual acuity returned to normal and the whitish fundus patches decreased in number and size in both eyes.  

CONCLUSIONS: Surgeons should be aware of potential risks and retinal complications associated with LASIK.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15506491&query_hl=1&itool=pubmed_docsum

Nippon Ganka Gakkai Zasshi. 2004 Sep;108(9):566-71.

Bilateral retinal detachment after laser in situ keratomileusis

Kohzaki K, Sano Y, Toda K, Mitooka K, Nakamura Y, Kitahara K. Department of Ophthalmology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105 8461, Japan.  

BACKGROUND: We report a case of bilateral retinal detachment after laser in situ keratomileusis(LASIK).  

CASE: A 49-year-old man received multiple laser photocoagulation for retinal lattice degeneration in both eyes and retinal tears in the left eye. He underwent bilateral LASIK in another country about 6 months after the laser photocoagulation. After the LASIK his eyes showed bilateral retinal detachment, 2 weeks later in the right eye and 5 months later in the left eye. We had to perform retinal detachment surgery four times, scleral buckling, vitrectomy, silicone oil tamponade, and removal of the silicone oil for the right eye, and one scleral buckling procedure for the left eye to achieve retinal attachment. Soon after each retinal surgery, we recognized diffuse flap edema and interface haze, three times in the right cornea and one time in the left, although this corneal flap edema subsided without any sequel.  

CONCLUSION: In this case, laser photocoagulation had been done several times to prevent retinal detachment in both eyes. However, retinal detachment occurred 2 weeks after LASIK in the right eye, and therefore, the LASIK procedure was considered to be the main factor influencing the development of the retinal detachment. The left eye showed retinal detachment 5 months after LASIK and we thought it possible that this retinal detachment occurred as a natural consequence of myopia. We believe it is important to hava a thorough funduscopic examination done before LASIK and it is necessary to pay attention to corneal edema and interface haze after retinal detachment surgery for post-LASIK patients.

Nippon Ganka Gakkai Zasshi. 2002 Feb;106(2):103-8.  

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11915370&query_hl=1&itool=pubmed_docsum

Two cases of retinal detachment following laser in Situ keratomileusis repaired by scleral buckling surgery  

Onguchi T, Eshita T, Mita S, Ishida S, Shinoda K, Kitamura S, Kawashima S, Inoue M, Oguchi Y, Toda I, Kato N. Department of Ophthalmology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.  

BACKGROUND: As laser in situ keratomileusis (LASIK) becomes the treatment of choice in the field of refractive surgery, postoperative rhegmatogenous retinal detachment has also begun to occur. However, since it has not been reported yet here in Japan, we report two cases of retinal detachment following LASIK with suggestions based on our experience.  

CASES: A 34-year-old male(Case 1) and a 26-year-old male(Case 2) suffered from retinal detachment one month and eight months after LASIK, respectively. Contributing retinal breaks were a horseshoe tear in Case 1 and atrophic holes in the lattice degeneration in Case 2. Each patient underwent partial scleral buckling with no intraoperative complication, resulting in successful retinal reattachment. Postoperatively, myopic changes developed and persisted one month in Case 1 and several months in Case 2.  

CONCLUSIONS: Great attention should be paid to the possibility of postoperative myopia after a repair of retinal detachment following LASIK. Thus, we stress the necessity of close cooperation between LASIK surgeons and vitreoretinal surgeons to settle the matter.

J Refract Surg. 2000 Nov-Dec;16(6):739-43.  

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11110315&query_hl=1&itool=pubmed_docsum

Comment in: J Refract Surg. 2001 Mar-Apr;17(2):153-4.

Farah ME, Hofling-Lima AL, Nascimento E. Federal University of Sao Paulo, Paulista School of Medicine, Brazil. This email address is being protected from spambots. You need JavaScript enabled to view it.  

PURPOSE: Four eyes had early rhegmatogenous retinal detachment within 3 months of laser in situ keratomileusis (LASIK) for correction of high myopia using the microkeratome, Clear Corneal Molder.  

METHODS: In two eyes, retinal detachment resulted from horseshoe tears, one occurring in an otherwise normal region of the retina and the other at the margin of an area of lattice degeneration detected during preoperative examination. The first eye was treated with retinopexy using a 287 encircling scleral exoplant, drainage of subretinal fluid, and laser photocoagulation by indirect ophthalmoscopy. The other eye was treated with pneumatic retinopexy and cryotherapy. In the other eyes, retinal detachment was the result of giant tears with no evidence of prior retinal degeneration. These eyes were treated with pars plana vitrectomy, fluid-gas exchange with 15% perfluoropropane (C3F8), endolaser photocoagulation, and a 42 encircling scleral exoplant.  

RESULTS: After treatment, the first two eyes achieved spectacle-corrected visual acuity of 20/40. In the last two eyes, final spectacle-corrected visual acuity was 20/400 in one eye and light perception in the other.  

CONCLUSIONS: Although no cause-effect relationship between LASIK and retinal detachment can be stated, these cases suggest that LASIK may be associated with retinal detachment, particularly in highly myopic eyes. Further studies are necessary to determine high-risk patient characteristics.

J Fr Ophtalmol. 2005 May;28(5):509-12.  

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15976718&query_hl=7&itool=pubmed_docsum

Feki J, Trigui A, Chaabouni M, Ben Salah S, Bouacida B, Chechia N, Zayani A, Nouira F, Daghfous F, Ayed S, Kamoun M. CHU, Sfax, Tunisie.  

INTRODUCTION: Refractive surgery by LASIK or photorefractive keratectomy (PRK) generaly aims at a myopic population that has a high probability of developing rhegmatogenous retinal detachment (RD). The authors report a multicenter study with 15 cases of RD appearing after refractive surgery by Excimer laser and discuss the role played by the techniques used.  

MATERIAL AND METHODS: Five centers fitted with nine Excimer laser devices took part in this study. Of 22,700 eyes undergoing refractive myopic surgery during the period 1994-2002, 15 eyes developed rhegmatogenous RD. The average age of the patients with RD was 37 years. The average myopia was 13.5 D. RD occurred a mean of 20 months after refractive laser.  

RESULTS: Fifteen eyes of 13 patients developed a rhegmatogenous RD, two of which were bilateral. Eight of these cases had LASIK surgery and six had photorefractive keratectomy; one of the latter patients was retreated with LASIK because of substantial regression after PRK. RD was total or subtotal in five eyes, partial superior with a temporal tear in six eyes, and nasal in three eyes. One case with inferior RD, two cases with giant retinal tear and one case with posterior tear were also repaired. Fourteen eyes were suitable for operation. The retina was reattached in 12 cases. Mean postoperative visual acuity was 7/10.  

DISCUSSION: The occurrence of rhegmatogenous RD in the myopic population is estimated at 2.2%. It is estimated at 0.1% in the emmetropic population. The Excimer laser, through its thermic effects, shock wave, traumatism undergone by the suction ring at the time of LASIK surgery, could increase this risk in myopic patients. A review of the literature cast doubt on the cause and effect hypothesis. Personal and multicenter studies (including ours) show that the frequency rate of rhegmatogenous RD after Excimer laser is equivalent and even lower than that estimated with an emmetropic population. The low percentage of RD after Excimer surgery found in the literature as well as in our study (<0.1%) may be explained by patient selection, the systematic monitoring of the peripheral fundus, and the prophylactic treatment of degenerative lesions by photocoagulation. In RD surgery, the cornea must be manipulated carefully, a case of flap dehiscence has been reported in the literature.  

CONCLUSION: Refractive surgery by LASIK or PRK for severe myopia increases the risk of RD. Systematically monitoring the peripheral fundus and preventive photocoagulation have mitigated its occurrence, and the risk incurred in the myopic population has fallen to the emmetropic population's rate. Nevertheless, candidates for LASIK or PRK surgery must be informed because severe myopia constitutes a non-negligible risk factor.

Ophthalmology. 2004 Jan;111(1):24-7.  

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14711709&query_hl=11&itool=pubmed_docsum

Comment in: Ophthalmology. 2005 Feb;112(2):359.  

Flaxel CJ, Choi YH, Sheety M, Oeinck SC, Lee JY, McDonnell PJ. Doheny Retina Institute of the Doheny Eye Institute, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.  

OBJECTIVE: To demonstrate axial length changes associated with anterior shift of the lens/iris diaphragm and anterior vitreous base in human cadaver eyes during suction ring application preceding Moria LASIK, and to propose that these changes may be associated with anterior retinal tears.  

DESIGN: Human eye study.  

MATERIALS: Eight human eye bank eyes ranging in age from 65 to 73 years. Two eyes had a history of intraocular surgery involving cataract extraction and intraocular lens implantation.  

INTERVENTION: Measurements of intraocular pressure via internal manometer and Tono-Pen, anterior chamber depth, and axial length before and after application of a Moria LASIK suction ring.  

MAIN OUTCOME MEASURES: Change in anterior chamber depth and axial length after Moria LASIK suction ring application.  

RESULTS: Axial length increases (mean change = 1.125 mm, P = 0.02) after application of the suction ring, whereas anterior chamber depth shows no significant difference (mean change = -0.01 mm, P = 0.9, suggesting anterior movement of the vitreous base resulting in traction on the anterior retina.  

CONCLUSION: Axial length increase with anterior displacement of the vitreous base during suction ring placement might predispose susceptible eyes to anterior retinal tears during and after LASIK.

Graefes Arch Clin Exp Ophthalmol. 2001 Jul;239(6):416-23.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11561789&query_hl=11&itool=pubmed_docsum

Luna JD, Artal MN, Reviglio VE, Pelizzari M, Diaz H, Juarez CP. Fundacion Ver, Cordoba, Argentina  

BACKGROUND: The presence of vitreoretinal changes following laser in situ keratomileusis in myopia is evaluated.  

METHODS: Clinically, 50 patients (100 eyes) with marked anisometropic myopia, 50 low-myopic eyes (<4.00 D) and 50 high-myopic eyes (>7.00 D) were prospectively evaluated pre- and postoperatively for the presence of newly recognized entoptic phenomena (vitreous floaters, light flashes, or both), and for vitreoretinal changes using indirect depressed fundus examination, a +90 D preset lens, Goldman three-mirror contact lens, and kinetic ultrasound (KU) before and after bilateral LASIK. Patients with previous partial or total posterior vitreous cortex detachment (PVD) were excluded. Experimentally, groups of adult pigs underwent KU, retinal fluorescein angiography (FA), and electroretinography (ERG) before and after applying the microkeratome suction ring for 30 s.  

RESULTS: Clinically, 8% (4 eyes) had positive perception of postoperative vitreous floaters in the low myopia group, and 32% (16 eyes) in the high myopia group. Postoperative light flashes were noted only in the high myopia group, in 12% of cases. Partial or total posterior vitreous cortex detachment was detected by biomicroscopy in 2% (1 eye) of the low and in 10% (5 eyes) of the high myopia group and by KU in 4% (2 eyes) of the low and in 24% (12 eyes) of the high myopia group. Experimentally, 2 pig eyes out of 12 developed partial PVD by KU, immediately after microkeratome suction ring application. All pig eyes showed significantly diminished ERG amplitudes during and immediately after suction ring application. No FA changes or delays in retinal circulation time were noted during or immediately after removal of the suction ring.  

CONCLUSIONS: Vitreoretinal alterations after LASIK were demonstrated clinically mainly by KU in high myopes. Experimentally, PVD were also demonstrated. Diminished ERG recordings with normal retinal circulation following suction ring application may suggest some transient choroidal circulation abnormalities.

Am J Ophthalmol. 2006 Mar;141(3):530-536.   

Yang CC, Wang IJ, Chang YC, Lin LL, Chen TH.  Department of Ophthalmology, Taipei County San-Chung Hospital, Taipei, Taiwan.  

PURPOSE: The aim of this study was to develop a predictive model based on preoperative variables for estimating postoperative intraocular pressure (IOP) of those eyes undergoing LASIK surgery, to predict the amount of underestimated IOP after LASIK for myopia and myopic astigmatism.  

DESIGN: Pretest-post-test longitudinal study.  

METHODS: Both eyes of 193 eligible subjects who underwent LASIK procedures at the Department of Ophthalmology, National Taiwan University Hospital, from July 2000 to December 2002 for myopia and myopic astigmatism were identified to build up the predictive models. IOPs were measured with noncontact air-puff tonometry. Information on age, gender, preoperative central corneal thickness (CCT), preoperative central corneal curvature (CCK), preoperative spherical equivalent refractive error, and ablation depth was collected and applied for predicting postoperative IOP after LASIK based on linear mixed model.  

RESULTS: Significant predictors for postoperative IOP after myopic LASIK procedures included age, gender, preoperative IOP, ablation depth, preoperative CCT, and preoperative spherical equivalent refractive errors. The linear mixed model, taking into account these significant preoperative correlates and the correlation of IOPs between both eyes of the same patient, explained 91% of the variation of postoperative IOP.  

CONCLUSIONS: A statistical model was developed for predicting the amount of underestimated IOP after LASIK for myopia and myopic astigmatism, which is of clinical importance to uncover ocular hypertension among patients whose information on postoperative IOP immediately after LASIK is not available.

And 24% of high myopes have posterior vitreous detachment after LASIK!

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15808256&query_hl=4

Ophthalmology. 2005 Apr;112(4):645-9.

Mirshahi A, Kohnen T.
Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am
Main, Germany.

Excerpt: Luna et al. reported the development of PVD after LASIK with an incidence of 2% in a group of 50 patients with low myopia (1.25 to 3.5 D) and 24% in a group of 50 patients with high myopia (6 to 10 D). Considering the data from the 100 eyes, this corresponds to 13%; thus, there is not a great deal
of difference between our results and the data in the literature.

DR. BILL TRATTLER THINKS SO!

We now know that corneal nerve damage from refractive surgery causes dry eye, and that this nerve damage was found to increase between years 2-3 post LASIK to over 40% loss of corneal nerve density, according to a recent study at the Mayo Clinic:

SOURCE

Dr. Trattler is aware of these findings, but claims that certain palliatives can treat “even the worst dry eye patients after LASIK”:

As posted in forum

“We have also shown (in a study I collaborated with Dr. Tseng on) that warm compresses along with other therapies can treat even the worst dry eye patients after LASIK. We took patients from other centers that had failed therapy, and were able to dramatically improve their dry eye state. The study ended 18 months ago, and these patients have done great even since the study end. Part of that is because dry eye is s cycle - so breaking the cycle (with Restasis pre-surgery or other therapies after surgery) can significantly help dry eye after LASIK, and can allow patients to get off Restasis after a number of months.”

Bill Trattler, MD - Miami, FL

Perhaps Dr. Trattler needs to hear from some folks on disability and/or in goggles from their LASIK dry eye.

13% of post-LASIK eyes have posterior vitreous detachment (floaters)!

...And 25% of high myopes have posterior vitreous detachment after LASIK!

SOURCE

2005 Apr;112(4):645-9.

Effect of microkeratome suction during LASIK on ocular structures.

Mirshahi A, Kohnen T.

Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

Excerpt: Luna et al. reported the development of PVD after LASIK with an incidence of 2% in a group of 50 patients with low myopia (1.25 to 3.5 D) and 24% in a group of 50 patients with high myopia (6 to 10 D). Considering the data from the 100 eyes, this corresponds to 13%; thus, there is not a great deal of difference between our results and the data in the literature.

13% of post-LASIK eyes have posterior vitreous detachment!

...And 25% of high myopes have posterior vitreous detachment after LASIK!

Source

2005 Apr;112(4):645-9.

Effect of microkeratome suction during LASIK on ocular structures.

Mirshahi A, Kohnen T. Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

Excerpt:Luna et al. reported the development of PVD after LASIK with an incidence of 2% in a group of 50 patients with low myopia (1.25 to 3.5 D) and 24% in a group of 50 patients with high myopia (6 to 10 D). Considering the data from the 100 eyes, this corresponds to 13%; thus, there is not a great deal of difference between our results and the data in the literature.