Noncontact holmium:YAG laser thermal keratoplasty for hyperopia

Noncontact holmium:YAG laser thermal keratoplasty for hyperopia

Noncontact holmium:YAG laser thermal keratoplasty for hyperopia Hugo D. Nano, MD, Sergio Muzzin, MD ABSTRACT Purpose: To describe our experience with...

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Noncontact holmium:YAG laser thermal keratoplasty for hyperopia Hugo D. Nano, MD, Sergio Muzzin, MD

ABSTRACT Purpose: To describe our experience with noncontact holmium:YAG laser thermal keratoplasty (Ho:YAG LTK). Setting: Refractive Surgery and Cornea Department, Clinica de Ojos Dr. Nano, Buenos Aires, Argentina. Methods: In this retrospective study, 182 hyperopic eyes from 116 patients were treated with noncontact Ho:YAG LTK. Mean age was 50 years :t 7 (SO), and the spherical equivalent (SE) of the subjective mean refraction (SMR) was +2.50 :t 0.87 diopters (D). Eyes with corneal power of more than 45 D, corneal pachymetry thicker than 550 ~m. and previous corneal surgery or disease were excluded. Holmium:YAG laser parameters include one to three rings of eight spots arranged in a radial and symmetrical array. Pulse energy was 240 mJ, with five pulses per spot. Patients were followed for 12 months. Results: The mean uncorrected visual acuity from 3 to 12 months was 20/40 (20/200 to 20/25), improving an average of three Snellen lines. Mean best spectaclecorrected visual acuity was 20/25 at all postoperative examinations, the same as preoperatively. Mean SE of the SMR was + 1.50 :t 0.98 D (range - 0.75 to +4.50 D) at 6 months and + 1.25 :t 0.96 D ( + 0.25 to + 3.25 D) at 1 year. After 9 months, 17% of operated eyes were retreated. Conclusion: In this study, Ho:YAG LTK was safe and effective, provided satisfactory correction of low hyperopia, and had a low complication rate. Good patient selection is the key to obtaining good results. J Cataract Refract Surg 1998;



urgical techniques formerly used to correct hyperopia include epikeratophakia and hexagonal keratotomy.1·2 Another method used to change the refractive power of the cornea was based on the property of corneal tissue to shrink to 30 to 50% of its original length when exposed to temperatures of 60 to 65°C. 3·4 These techniques were based on the work ofLans, 5 who in 1898 described thermal keratoplasty. Insertion of a hot cautery tip into the corneal stroma was a technique Reprint requests to Hugo D. Nano, MD, Clinica de Ojos Dr. Nano, Sarmiento 1431, (1663) San Miguel, Buenos Aires, Argentina.

used by Fyodoro0 and by Neumann and coauthors.7·8 Other techniques based on this method aimed to modifY corneal curvature, 9- 11 and while substantial changes were achieved, they have been abandoned because of complications. 12·13 At present, many ophthalmologists have been applying laser thermal keratoplasty (LTK), 14- 18 especially noncontact holmium:YAG (Ho:YAG) LTK, with satisfactory initial clinical results. 19-21 This paper describes our experience with 182 hyperopic eyes treated with noncontact Ho:YAG LTK after a 1 year follow-up and demonstrates the safety and effectiveness of this method.




Patients and Methods Holmium:YAG LTK was performed on 182 eyes of 116 patients. Mean age of the 70 women and 46 men was 50 years ± 7 (SO) (range 40 to 72 years). In 92 cases (50.5%) the right eye was operated on and in 90 cases (49.5%), the left eye. The inclusion criteria are shown in Table 1. The mean preoperative uncorrected visual acuity (UCVA) was 20/80 (20/400 to 20/25) and the best spectacle-corrected visual acuity (BSCVA), 20/25 (20/50 to 20/20). The mean spherical equivalent (SE) of the subjective mean refraction (SMR) preoperatively was +2.50 ± 0.87 diopters (D) (range +0.75 to +4.75 D). Preoperative evaluation included automated refractometry (Topcon KR 3000) measurements with and without cycloplegia, subjective measurement of visual acuity, intraocular pressure (lOP), slitlamp biomicroscopic evaluation, binocular ophthalmoscopy for fundus examination, ultrasonic corneal pachymetry (Alcon corneal pachymeter), and computerized corneal topography (EyeSys Corneal Analysis System). All patients were told that the treatment would not modifY the evolution of presbyopia and therefore during the postoperative period they should continue wearing spectacles for near vision correction. They were advised about the possibility of regression and retreatment after surgery. All patients provided written consent. The Ho:YAG laser has a wavelength of 2.13 J.Lm and a pulse duration of 250 ).IS. The pulse repetition frequency was 5 Hz and the repetition rate, 5 pulses per spot. The pulse energy was adjustable (100 to 300 mJ) but we used 240 mJ in all cases. The Corneal Shaping System (Sunrise Technologies, Inc.) was used in the surgery. The laser beam pattern consisted of eight spots arranged in a symmetrical ring, with an adjustable

Table 1. Selection criteria for Ho:YAG LTK treatment. 40 years of age or older Up to +4.00 D sphere Corneal pachymetry thinner than 550 J.lm No ocular pathology No previous anterior segment surgery No connective disease




Figure 1. (Nano) One-ring treatment pattern for spherical correction.

treatment diameter between 5.0 and 7.5 mm; the number of rings was adjustable from one to three (Figure 1). The number depended on the hyperopia to be treated, based on our nomogram. The diameter of each spot was approximately 590 J.Lm. Spot energy was measured with a joulemeter (Molectron Model 200) calibrated before each procedure. All treatments were performed with a radial spot pattern to treat the spherical component. During the procedure, the patient fixated on a red light emitting diode. The surgeon focused on the corneal surface with a green heliumneon laser (wavelength 543 nm) and centered with a red helium-neon tracer beam (wavelength 633 nm). Topical anesthesia consisted of three drops of proparacaine 0.5% with 8 minutes between the first and the third drop. At the same time, a lid speculum was inserted and the tear film was left to dry for 3 minutes before the laser treatment. Immediately after treatment, several drops of tobramycin 0.3% solution were applied and the eye was occluded for 24 hours. If the patient required an analgesic, lysine clonixinate pills (125 mg) (Dorixina®) were administered every 8 hours. From the day after surgery, tobramycin 0.3% drops (Tobrex®) were instilled four times a day together with artificial tears (Cellufresh®) for 1 week. Follow-up examinations were performed at 1, 3, 7, and 14 days and 1, 3, 6, 9, and 12 months postoperatively. The number of eyes checked at each follow-up was as follows: 1 month, 182; 3 months, 178; 6 months, 164; 9 months, 146; 12 months, 140. In each case, visual acuity with and without correction was measured and the patient was asked about pain, foreign-body sensation, and symptoms of visual discomfort (photo-




Figure 2. (Nano) Mean UCVA and BSCVA postoperatively.


3 N=182


6 N=164

9 N=146


12 N=140

phobia, halos, glare). These were classified as none, mild, moderate, and severe. At each postoperative visit, thorough slidamp examination was performed and the corneal opacities in the treated sites were graded: 0 = none visible; 1 = mild; 2 = moderate; 3 = severe. Postoperative corneal topographies were done at 1 week, and 6, 9, and 12 months. The surgical procedure, postoperative treatment, and follow-up were performed by the five experienced surgeons who make up the Refractive Surgery Department. Statistically significant differences were determined by Student's t-test; P < .05 was considered significant.

gained an average of three Snellen lines of UCVA. Figure 3 shows the percentage of eyes with UCVA of 20/30 or better at each follow-up. Mean BSCVA was 20/25 at all follow-up examinations (Figure 2). Mean SE of the SMR is shown in Figure 4. It indicates that after 1 year, the mean correction of the subjective SE was -1.25 D. The proportion of eyes within ::!:: 1.00 D of emmetropia preoperatively was 3.25%. At 6 months postoperatively, 56.00% of eyes were within ::!:: 1.00 D of emmetropia, and at 12 months, 46.00%. Corneal topography demonstrated satisfactory centration and an important change in the central refractive power and curvature radius without induced astigmatism. Five millimeters of central cornea were left untouched (Figure 5).

Results Mean UCVA at follow-up examinations is shown m Figure 2. One year postoperatively, patients had

100 90 80 70 %of 60 eyes 50 40 30 20 10 0

Figure 3. (Nano) Percentage of eyes with UCVA of 20/30 or better postoperatively.













+2.00 +1.50 Figure 4. (Nano) Mean SE of SMR postoperatively.

+1.00 +0.50



1 N=182







No patient experienced sight-threatening complications. Twenty-four (20%) manifested slight pain and 50 (43%) mild epiphora; 39 (33%) complained of mild photophobia, and almost half (63, 54%) reported foreign-body sensation. All these subjective symptoms were reported during the first 48 to 72 hours postopera-


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1 48


Figure 5. (Nano) Corneal topography before (top) and after (bottom) treatment

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Po st-Op


tively and coincided with the epithelialization time of the cornea at the spot sites. No significant anterior chamber inflammation was observed in any patient. In one case, the treatment ring was decentered 1.0 mm nasally because (according to corneal topography) of involuntary patient movement during the treatment.

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with noncontact Ho:YAG LTK.


This decentration had no effect on the correction obtained, and the patient did not report significant diplopia or glare. Induced astigmatism occurred in a female patient with a preoperative SE of SMR of +2.25 D. Mter 1 month, it was + 1.00 +2.75 X 70, and after 3 months, + 1.00 +2.00 X 70. After 8 months, the SMR was + 1.00 + 1.00 X 65 and the UCVA was 20/70. No patient lost one or more lines of BSCVA. Regression in SMR was observed in 45%. Mean SE of SMR in all eyes was +0.75 ± 1.00 D at 1 month and + 1.25 ± 0.96 D at 12 months. Nine months postoperatively, 17% of the operated eyes were retreated (31 eyes). Eighteen (56%) were retreated with Ho:YAG LTK and 14 (44%) with excimer laser photorefractive keratectomy for hyperopia. For the 14 patients, a more aggressive procedure was selected because the regression was significant (SE of SMR +3.50 or +4.00). Descemet's membrane folds were seen between the spots in some patients in the early postoperative period, but after 4 weeks these were not observed in any patient. Signs of visible haze on the shot sites ranged from moderate to severe (grades 2 to 3) during the first 72 hours postoperatively, diminished over time, and at 12 months were only visible under the slitlamp (mild, grade 1). In some cases, they were detectable with cycloplegia, which increases visibility. The conical-shaped opacities in the treated patients ranged from 60 to 70% of corneal thickness under slitlamp examination. No significant changes in lOP were detected during the 12 months of follow-up. Intraocular pressure measurements below 19 mm Hg were considered normal. The degree of satisfaction of the nonretreated patients was high; most were well satisfied with the results obtained with the UCVA at distance. Furthermore, they subjectively noticed an improvement in the near and middle distance visual acuity and some presbyopic patients achieved good visual acuity for reading.

Discussion The prevalence of hyperopia in general populations has been reported, 22 especially the prevalence of low hyperopia in older populations. 23 Laser thermal keratoplasty has proved to be an efficient technique to correct this by modifYing the central curvature of the cornea. With this technique, the heat from the laser is absorbed

by the cornea and alters the properties and structure of stromal collagen (shrinkage), thus modifYing the anterior corneal curvature. The noncontact Ho:YAG has a wavelength of 2.12 J.lffi, providing a precise, controlled, and simultaneous dispersion of energy over the corneal surface. Previous research has demonstrated that the Ho:YAG noncontact method is safe, stable, and effective. Significant corrections in the corneal curvature with mild complications have been reported after 2 years of follow-up.' 9- 21 '24 Several advantages of this technique for the surgeon and the patient should be considered when choosing a surgical procedure for low hyperopic patients. It is fast and simple and requires no patient cooperation (except for centration). It is well tolerated and provides quick rehabilitation with minimal patient discomfort. The solid-state laser is of low cost and maintenance. In this clinical, retrospective study, we obtained encouraging results in hyperopic patients 12 months after noncontact Ho:YAG LTK treatment. Our results confirm the safety of this method since complications have not been severe. Furthermore, there have been no changes in lOP, and postoperative visual acuity and the visual axis remained untouched. No patient lost a line of BSCVA. We saw only one case of mild decentration and another of induced astigmatism that decreased over time (more than 50%). There were no postoperative complications related to visual quality such as glare and halos. The mean UCVA at 12 month follow-up was 20/40 from a preoperative mean value of 20/80. The mean SE of SMR at 12 months ( + 1.25 D) was a considerable improvement over the preoperative value ( + 2.50 D). The technique's effectiveness relies on the proper selection of patient and type of hyperopia. Good results were obtained in distance visual acuity without correction and SMR after 1 year follow-up. Many patients achieved an improvement in near subjective visual acuity (which was not objectively evaluated in this study) and also in middle distance, an aspect highly appreciated by hyperopic patients. The multifocal effect of this procedure explains the patients' high degree of satisfaction; even those who experienced some regression accepted retreatment by the same technique. The stability achieved by this group of patients has been satisfactory, even though regression occurred between the immediate postoperative period and 6 months




later. There was considerable stability at 6, 9, and 12 months postoperatively. The mean SE of SMR was + 1.52 D at the 6 month follow-up, + 1.30 D at 9 months, and + 1.25 D at 1 year. This implies that there was less than 1.00 D of change in the SMR between the three follow-ups. Longer follow-up is required to evaluate long-term stability. Postoperative regression is the main limitation of this procedure not only in our series of patients but also in previous reports. 25 Between 1 and 12 months postoperatively, we noted 45% of the regression comparing the mean SE of SMR. Nine months after the procedure, it was necessary to retreat 17% of the patients. The amount of regression and retreatment required by this series of patients may be because highly hyperopic patients were enrolled. Our goal is to select patients better to reduce this index and to analyze factors related to the patient and the hyperopia so we can increase the efficacy, predictability, and stability of the procedure. In the future, we will evaluate whether regression develops or whether it follows the stability observed between 6 and 12 months. This evaluation should enable us to modifY treatment parameters such as pulse energy, number of rings, number of pulses, and diameter of treatment to achieve stable long-term results. In summary, we believe noncontact Ho:YAG LTK is an important technique to consider in patients older than 40 years with low hyperopia. It was a fast and safe surgical procedure without serious complications and provided encouraging improvements in refraction. Longer follow-up and thorough investigation of regression factors are needed before it can be considered the "ideal" technique.

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22. Gordon A. Refractive error in a Puerto Rican rural population. J Am Optom Assoc 1990; 61:870-874 23. Leibowitz HM, Krueger DE, Maunder LR, et al. The Framingham Eye Study Monograph. Surv Ophthalmol 1980; 24(suppl):472-479 24. Kohnen T, Husain SE, Koch DD. Corneal topographic

changes after noncontact holmium:YAG laser thermal keratoplasty to correct hyperopia. J Cataract Refract Surg 1996; 22:427-435 25. Ali6 JL, Ismail MM, Sanchez Pego LL. Correction of hyperopia with noncontact Ho:YAG laser thermal keratoplasty. J Refract Surg 1997; 13:17-22