Corneal topographic changes after noncontact holmium:YAG laser thermal keratoplasty to correct hyperopia

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

Non-contact Holmium:YAG Laser Thermal Keratoplasty for Hyperopia: Two-year Follow-up

PURPOSE

We evaluated the safety and efficacy of the non-contact holmium:YAG laser thermal keratoplasty (LTK) for the treatment of mild to moderate hyperopia without astigmatism.

METHODS

A prospective, non-comparative case series included 50 eyes of 28 patients (aged > or =40 years) who had stable refraction and an astigmatic component < +0.50 diopters (D). We applied the non-contact pulsed holmium:YAG laser to treat the hyperopic spherical component using the Hyperion LTK System. All patients had minimum 12-month follow-up and 64% (18 patients) had 24-month follow-up.

RESULTS

The mean age of patients was 48.4 +/- 8.23 years (range: 40 to 62 years). The preoperative hyperopic mean spherical equivalent refraction was +2.32 +/- 0.975 D (range: +1.00 to +4.75 D). Postoperatively, the subjective manifest refraction decreased from the preoperative mean value of +2.32 D to a mean -0.09 D at 1 month after surgery and regressed to +0.315 D at the last follow-up examination, resulting in a mean correction of +2.005 +/- 0.81 D at 24 months after surgery. Preoperatively, mean uncorrected visual acuity in LogMAR units was 0.798 +/- 0.353 and at 12 months after surgery, it was a mean 0.108 +/- 0.136. Keratometric power increased from 42.595 +/- 1.949 D before surgery to 44.605 +/- 1.626 D at 24 months after surgery.

CONCLUSIONS

Holmium:YAG LTK was an acceptable alternative for the correction of mild to moderate hyperopia in this middle-aged population.

Anterior chamber angle biometry with ultrasound biomicroscopy after diode laser thermal keratoplasty

PURPOSE

To evaluate the effect of diode laser thermal keratoplasty (DTK) on the geometry of the anterior chamber angle with ultrasound biomicroscopy (UBM).

SETTING

Department of Ophthalmology and Optometry, Paracelsus Private Medical University, Salzburg, Austria.

METHODS

In 9 eyes, a Rodenstock DTK (ProLaser Medical Systems) was used to correct hyperopia (n = 6) or hyperopic astigmatism (n = 3). Hyperopia was treated with a single- or double-ring pattern and hyperopic astigmatism, with additional spots in each of the flat half meridians. Ultrasound biomicroscopy measurements of the chamber angle were obtained preoperatively and 3 months postoperatively using a Humphrey UBM 840 system with a 50 MHz transducer. Quantitative measurements were performed at 3-, 6-, 9-, and 12-o'clock positions using a standardized method.

RESULTS

No statistically significant differences between the preoperative and postoperative chamber angle measurements were detected.

CONCLUSIONS

The results of the UMB measurements were surprising given the flattening of the corneal periphery found by computerized topography, a finding that suggests narrowing of the chamber angle. Shortening of the corneal tissue may result in centripetal traction that affects the trabecular meshwork and results in a relative opening of the chamber angle structures.

Holmium Laser Thermal Keratoplasty for Hyperopia in Eyes Overcorrected With Laser in situ Keratomileusis for Myopia

PURPOSE

To assess the efficacy and safety of holmium laser thermal keratoplasty (Ho:LTK) for hyperopia in eyes overcorrected after laser in situ keratomileusis (LASIK) for myopia.

METHODS

We performed a prospective evaluation of Ho:LTK in eyes with secondary hyperopia from +1.00 to +5.50 D after LASIK. Thirty-seven eyes of 23 patients received one concentric 8-spot application at the 6-mm-diameter zone. Mean patient age was 41.3 +/- 13.0 years (range 20 to 68 yr). Mean corneal thickness was 455.86 +/- 31.20 microm (range 373 to 506 microm).

RESULTS

Mean spherical equivalent refraction changed from +2.30 +/- 1.08 D to +0.45 +/- 1.00 D at 12 months after Ho:LTK. Thirty-one eyes (84%) were within +/- 1.00 D of emmetropia and 25 eyes (68%) were within +/- 0.50 D at 1 year. Mean change in refraction was 1.84 +/- 0.92 D. No eye lost 2 lines of best spectacle-corrected visual acuity.

CONCLUSIONS

Ho:LTK is a suitable alternative for correcting secondary hyperopia resulting from LASIK for myopia. Parameter adjustments may be necessary for improving the results.

Diode Laser Thermal Keratoplasty for Hyperopia and Hyperopic Astigmatism in Patients Younger Than 40 Years

PURPOSE

We performed a prospective, nonrandomized investigation of contact continuous wave diode laser thermal keratoplasty (DTK) for correction of hyperopia and hyperopic astigmatism. The goal of surgery was not to achieve emmetropia but to investigate the refractive effect in patients younger than 40 years.

METHODS

Twenty eyes with spherical hyperopia (Group A) and 15 eyes with hyperopic astigmatism (Group B) were treated with two rings; treatment zone diameter of the inner ring was 6 or 7 mm. Each ring consisted of eight spots for hyperopia correction; for astigmatism correction four additional pairs of spots were applied around the flat corneal meridian.

RESULTS

Mean change in manifest spherical equivalent refraction 18 months postoperatively in Group A was 2.00 +/- 0.90 D (Group B, 15 mo, 1.80 +/- 0.60 D). Mean increase in keratometric power was 1.20 +/- 0.60 D (1.30 +/- 0.60 D). Mean refractive astigmatism reduction was 0.10 D (1.70 D). Mean paired differences per month for regression between spherical equivalent manifest refraction/keratometric power was 0.12/0.04 D (0.06/0.05 D) from 9 to 12 months, 0.01/0.04 D (0.06/0.06 D) from 12 to 15 mo, and -0.03/ +/- 0 D from 15 to 18 months. Mean uncorrected visual acuity improved from 20/100 to 20/32 (20/63 to 20/32). No eye lost more than 1 line of BSCVA. The amount of correction showed an age dependency.

CONCLUSION

DTK is a minimally invasive, low-risk procedure, and was effective for correction of low hyperopia and low to moderate hyperopic astigmatism in patients less than 40 years.

Two-year follow-up of noncontact holmium laser thermokeratoplasty for the correction of low hyperopia

PURPOSE

To summarize the 2-year results of laser thermal keratoplasty with a holmium:yttrium-aluminum-garnet (Ho:YAG) laser and the Sunrise Corneal Shaping System and assess the procedure's safety, efficacy and predictability in correcting hyperopia in a phase III clinical intervention case series.

METHODS

The Ho:YAG laser was used to correct low hyperopia (manifest spherical equivalent of +0.75 to +2.50 dioptres [D], with manifest cylinder of 1.00 D or less) in 38 eyes of 28 patients 40 years of age or older. Laser pulses were delivered to the cornea in 2 radially placed, concentric, 8-spot rings 6.0 and 7.0 mm in diameter. The last follow-up was at 2 years.

RESULTS

The preoperative uncorrected visual acuity (UCVA) at distance was less than 20/40 in 82% of the eyes and at near was less than 20/32 in 42%. At 2 years the distance UCVA was 20/40 or better in 100% of the eyes and 20/20 or better in 84%, and the near UCVA was 20/32 or better in 97% of the eyes and 20/20 or better in 8%. The difference between the preoperative and postoperative UCVA was statistically significant (p < 0.01). The correction at 2 years was within 0.50 D of that intended in 92% of the eyes and within 1.00 D in 100%. The reduction in mean spherical equivalent at 2 years was statistically significant (p < 0.0001). No loss of 2 lines or more in best-corrected visual acuity occurred after the 1st month of follow-up.

INTERPRETATION

The Ho:YAG Sunrise Corneal Shaping System is safe and effective for the treatment of low hyperopia and astigmatism. It provides a predictable refractive outcome at 2 years of follow-up. However, our results show a tendency towards regression by 2 years.

Influence of temperature and time on thermally induced forces in corneal collagen and the effect on laser thermokeratoplasty

PURPOSE

To investigate thermomechanical aspects of corneal collagen denaturation as a function of temperature and time and the effect of the induced forces on refractive changes with laser thermokeratoplasty (LTK).

SETTING

Medical Laser Center Lübeck, Lübeck, Germany.

METHODS

In a material-test setup, porcine corneal strips were denatured in paraffin oil at various constant temperatures for 10 and 500 seconds, and the temporal course of the contractive forces was studied under isometric conditions. Typical LTK lesions were performed in porcine eyes in vitro with a continuous-wave infrared laser diode at a wavelength of 1.87 microm for 10 and 60 seconds. The laser power was chosen to achieve comparable denatured volumes at both irradiation times. The refractive changes were measured and analyzed by histologic evaluations and temperature calculations.

RESULTS

The time course of the induced forces was characterized by a maximal force, which increased almost linearly with temperature, and a residual lower force. After 500 seconds of heating, the highest force was achieved with a temperature of 75 degrees C. With a limited heating period of only 10 seconds, the forces steadily increased with temperature over the entire observation period. Laser thermokeratoplasty produced less refractive change after 10 seconds of irradiation than after 60 seconds, although the laser power was 25% higher in the short heating period. Polarization light microscopy of LTK lesions revealed different stages of thermal damage.

CONCLUSION

The course of the contractive forces during and after heating is a complicated function of the spatial time/temperature profile. Laser thermokeratoplasty lesions produced with 2 irradiation times showed different stages of denaturation and induced refractive change.

Paracentral photoablations to correct higher grades of naturally occurring astigmatism

PURPOSE

To evaluate the efficacy of paracentral ablations in treating higher degrees of naturally occurring myopic and hyperopic astigmatism.

SETTING

Augenklinik, Kreiskrankenhaus Bad Hersfeld, Germany.

METHODS

Twenty-five eyes (7 with hyperopia, 18 with myopia) with naturally occurring corneal astigmatism greater than 1.75 diopters (D) were treated by excimer laser. The mean refractive cylinder was -4.05 D +/- 1.46 (SD) (range -1.75 to -7.00 D). The intention was to reduce the astigmatism without consideration of the spherical refractive error. Two paracentral ablations were performed by photorefractive keratectomy with treatment zones of 3.5 mm in the flatter meridian of the cornea. Objective refraction, best corrected visual acuity (BCVA), changes in corneal radius, development of haze, and regression were recorded.

RESULTS

The paracentral ablations induced a steepening of the corneal radius in the flatter meridian from 8.12 mm (mean preoperative value) to 7. 84 mm (mean postoperative value) and thus reduced the mean refractive cylinder to -1.12 +/- 0.82 D (range 0.00 to - 3.00 D), corresponding to a mean reduction of 78%. No eye experienced a loss of Snellen lines. The preoperative BCVA (mean 20/25; range 20/50 to 20/20) was unchanged postoperatively

CONCLUSIONS

Paracentral ablations resulted in a stable corneal curvature immediately after epithelial healing, with a moderate regression over time. Paracentral ablations with the excimer laser appear to be a safe and effective method to correct higher grades of corneal astigmatism.

Comparison of changes in manifest refraction and corneal power after photorefractive keratectomy

PURPOSE

To determine which corneal curvature values most closely correlate to change in manifest refraction after excimer laser photorefractive keratectomy.

METHODS

In a prospective study at the Cullen Eye Institute, excimer laser photorefractive keratectomy was performed on 27 eyes of 27 patients (mean age, 38.07+/-6.65 years). Preoperative refractive errors ranged from -2.25 diopters to -8.75 diopters (mean, -5.74+/-2.09 diopters). Preoperatively and 1 month postoperatively, we determined the spherical equivalent of the subjective manifest refraction (corrected for a 12-mm vertex distance) and measured corneal power using standard keratometry (Bausch & Lomb Keratometer; Rochester, New York) and computerized videokeratography (EyeSys Corneal Analysis System; Premier Laser Systems Inc, Houston, Texas). We collected 15 corneal values: standard keratometry and 14 computerized videokeratography values calculated using the axial, instantaneous, and refractive formulas. All calculations were performed with 1.3375 and 1.376 for the refractive index of the cornea. For each of the corneal values, we subtracted the change in corneal power from the change in manifest refraction and calculated for this difference the means, SDs, correlations, and regressions.

RESULTS

Mean differences between change in refraction and change in corneal power were lower when for a refractive index of 1.376 than for 1.3375, were lowest for the most central measurement points, and displayed a high SD. A value of 1.408 for the refractive index would be required to optimize the correlation between change in manifest refraction and effective refractive power of the central 3 mm of the cornea.

CONCLUSIONS

For individual patients who have undergone photorefractive keratectomy, changes in corneal values determined by computerized videokeratography or by standard keratometry do not reliably predict change in manifest refraction.

Corneal topography classification in myopic eyes based on axial, instantaneous, refractive, and profile difference maps

PURPOSE

To refine and develop systems for classifying the topography of myopic corneas using axial, instantaneous, refractive, and profile difference maps.

SETTING

Baylor College of Medicine, Cullen Eye Institute Houston, Texas, USA.

METHODS

Using the EyeSys Corneal Analysis System, computerized videokeratographs of 153 corneas of 78 myopic patients were retrospectively analyzed. Patterns were defined with respect to the mid-dioptric green color. Relationships among pattern types, refractive power, corneal power, corneal uniformity index (CU index), and predicted corneal visual acuity (PC acuity) were calculated.

RESULTS

Six types of patterns for axial, instantaneous, and refractive maps and 3 types of patterns for the profile difference map were defined. For a given cornea, there was a weak correlation among the patterns in the axial, instantaneous, and profile difference maps. The circular with central irregularity pattern in auto-scale refractive maps and the irregular pattern in profile difference maps and axial maps were correlated with lower CU index and PC acuity values. Clinical classification of instantaneous maps did not contribute substantially to the information provided by axial maps.

CONCLUSION

Patterns of computerized videokeratographs varied according to the type of topographic map. The classification systems used provide a baseline for analyzing the response of the cornea to various interventions.

Excimer laser assisted in situ keratomileusis for hyperopia

PURPOSE

To evaluate hyperopic surgical correction with 6.0 mm optical zone hyperopic laser in situ keratomileusis (LASIK) after various refractive procedures.

SETTING

Buzard Eye Institute, Las Vegas, Nevada, USA.

METHODS

This study followed 14 eyes of 14 patients who had hyperopic LASIK with a VISX Star laser. Mean follow-up was 8 months. The patients represented a variety of preoperative situations, including primary radial keratotomy (RK) (5 eyes) primary automated lamellar keratectomy (ALK) (2 eyes), primary LASIK (3 eyes), congenital hyperopia (1 eye), and combinations of ALK, RK, and LASIK. In all patients, a toroidal or "doughnut-shaped" ablation was constructed with the use of a 3.5 mm diameter soft contact lens as a blocking agent centrally with a 6.0 mm outside beam diameter.

RESULTS

Mean preoperative spherical equivalent was +1.33 diopters (D) +/- 0.5 (SD) (range +0.50 to +1.88 D). The mean spherical equivalent was -0.32 +/- 1.20 D (range -1.25 to +2.63 D) at 1 month postoperatively and -0.15 +/- 0.60 D (range -1.13 to +1.25 D) at the last follow-up. Uncorrected visual acuity of 20/40 was obtained by 13 eyes (93%). No eye lost 2 or more lines of best corrected visual acuity at last follow-up. Four eyes required a postoperative LASIK enhancement procedure to correct induced myopia. No significant complications were seen.

CONCLUSION

Hyperopic LASIK with the technique used in this study appeared safe, predictable, and stable. It represents a simple way to add hyperopic correction to existing laser systems.

Continuous-wave diode laser thermokeratoplasty: first clinical experience in blind human eyes

PURPOSE

To evaluate the safety and stability of laser thermokeratoplasty (LTK) with a continuous-wave diode laser in blind human eyes and to optimize parameters for a study in sighted eyes.

SETTING

Department of Ophthalmology, Medical University Lübeck, Germany.

METHODS

A continuous-wave diode laser was set to emit radiation with a wavelength of 1.854 microns (Group 1, n = 4) or 1.870 microns (Group 2, n = 4) and 100 to 150 mW power for 10 seconds. A focusing handpiece was coupled with an application mask and fixed by partial vacuum to the conjunctiva or cornea. The radiation was focused into the corneal stroma between 400 and 600 microns in Group 1 and set to 1000 microns in Group 2. Eight (Group 1, single ring) or 16 (Group 2, double ring) coagulations were applied.

RESULTS

The refractive change increased with higher laser power and smaller ring diameters. Two rings of coagulations provided higher and more stable refractive changes of up to 5.66 diopters (D) than a single ring. The refractive effect stabilized between 3 and 6 months postoperatively. At 1 year, mean refractive change was +0.99 D +/- 0.39 (SD) in Group 1 and +2.32 +/- 2.24 D in Group 2. Extensive endothelial damage occurred in Group 1 but was minimal in Group 2.

CONCLUSIONS

Diode LTK was used to treat hyperopia safely and effectively. Regression occurred mainly in the first 3 postoperative months. With a wavelength of 1.870 microns, corneal endothelial damage was limited.

Axial, instantaneous, and refractive formulas in computerized videokeratography of normal corneas

PURPOSE

To compare the values for corneal power determined by the axial, instantaneous and refractive formulas when imaging normal human corneas using computerized videokeratography.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

METHODS

This prospective clinical trial involved 60 corneas of 30 normal volunteers. Computerized videokeratography was performed to determine corneal power at the center and the 1, 3, 5, and 7 mm zones using the 3 formulas.

RESULTS

Mean central corneal power was 42.86 diopters (D) with each of the formulas. The mean corneal powers for the axial, instantaneous, and refractive formulas were 43.09, 43.21, and 42.98 D at the 1 mm zone; 43.10, 42.92, and 43.46 D at the 3 mm zone; 42.75, 41.63, and 44.02 at the 5 mm zone; 42.21, 40.30, and 44.79 D at the 7 mm zone, respectively. The differences among powers for the 3 formulas at the 3, 5, and 7 mm zones were statistically significant (P < .01).

CONCLUSION

In normal corneas, clinically significant differences exist in the corneal power values calculated by the axial, instantaneous, and refractive formulas.

Noncontact holmium:YAG laser thermal keratoplasty for hyperopia

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 +/- 7 (SD), and the spherical equivalent (SE) of the subjective mean refraction (SMR) was +2.50 +/- 0.87 diopters (D). Eyes with corneal power of more than 45 D, corneal pachymetry thicker than 550 microns, 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 spectacle-corrected visual acuity was 20/25 at all postoperative examinations, the same as preoperatively. Mean SE of the SMR was +1.50 +/- 0.98 D (range -0.75 to +4.50 D) at 6 months and +1.25 +/- 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.

Radial and staggered treatment patterns to correct hyperopia using noncontact holmium:YAG laser thermal keratoplasty

PURPOSE

To compare the effects of two treatment patterns in the correction of hyperopia by noncontact holmium:YAG laser thermal keratoplasty (LTK).

SETTING

Divisione Oculistica, Ospedale S. Gerardo, Monza, Italy.

METHODS

Using two treatment patterns, we performed noncontact LTK in one session in 16 eyes of 8 patients with isometropic hyperopic refractive errors; mean preoperative subjective cycloplegic refraction was +4.90 diopters (D) +/- 1.17 (SD). The treatment consisted of 24 spots in three concentric rings of eight spots each; ring diameters were 6.0, 7.0, and 8.0 mm, respectively. Each spot received seven pulses of laser energy at 30 mJ/pulse. We treated one eye of each patient with a radial pattern (the spots of the three rings aligned on the eight semimeridians) and the fellow eye with a staggered pattern (the spots of the contiguous rings at 22.5 degrees from each other). Follow-up at 1, 15, 30, 90, 180, and 360 days included subjective cycloplegic refraction, uncorrected (UCVA) and spectacle-corrected visual acuity (SCVA), computerized videokeratography (CVK), and Scheimpflug camera examination.

RESULTS

One year postoperatively, the mean subjective cycloplegic refraction was +2.75 +/- 1.6 D in the eyes treated with the radial pattern and +3.40 +/- 1.6 D in those treated with the staggered pattern; the mean change in subjective cycloplegic refraction was 2.15 and 1.50 D, respectively. Mean UCVA improved by five lines in the radial group and by four lines in the staggered group. Mean SCVA returned to preoperative levels by day 15 in the radial group and at 1 year in the staggered group; at 1 year, SCVA improved by one line in the radial group and remained unchanged in the staggered group. No eye lost one or more lines of SCVA. Refractive astigmatism was essentially unchanged in both groups. Scheimpflug photography and CVK indicated larger and more uniform corrected zones in the radial group.

CONCLUSIONS

Radial and staggered patterns effectively corrected low hyperopia, although both were subject to a certain amount of regression. The radial pattern produced faster postoperative recovery of SCVA and demonstrated greater refractive stability.

Iris-claw lens in phakic eyes to correct hyperopia: preliminary study

PURPOSE

To evaluate the results of implanting convex, iris-fixated, anterior chamber intraocular lenses (IOLs) in phakic eyes to correct high hyperopia.

SETTING

Robert Koch Hospital, Hannover-Gehrden, Germany (Center A), and Dr. Daljit Singh Eye Hospital, Amritsar, India (Center B).

METHOD

Two eyes at Center A and 67 at Center B had implantation of an anterior chamber, convex, iris-fixated IOL. Follow-up of the 2 eyes at Center A was 91 months. Mean follow-up at Center B was 78 months +/- 24 (SD) (range 12 to 120 months).

RESULTS

At Center B, all eyes except two in one patient had clear corneas and no iritis or glaucoma at the last follow-up. The patient with complications (glaucoma and corneal degeneration in both eyes) did not return for follow-up until more than 4 years postoperatively and thus did not have adequate postoperative care.

CONCLUSION

Implantation of a convex iris-claw lens into the anterior chamber of phakic eyes to correct high hyperopia was successful from a refractive aspect. The clinical risks appear tolerable. However, life-long observation by endothelial microscopy is mandatory.

Laser in situ keratomileusis for hyperopia

PURPOSE

To examine the initial results of laser in situ keratomileusis (LASIK) for hyperopia.

SETTING

Arzt für Augenheilkunde, Mannheim, and Photoingenieur, Wendelstein, Germany.

METHODS

This retrospective study evaluated 43 eyes having hyperopic LASIK using the Automatic Corneal Shaper (Chiron Vision) and the MEL 60 excimer laser (model 94, Aesculap-Meditec). Patients were divided into two groups. Group 1 consisted of 20 eyes with a refraction from +1.00 to +4.00 diopters (D) and Group 2, 23 eyes from +4.25 to +8.00 D. Objective refraction and visual acuity were measured over 12 months.

RESULTS

One year after LASIK, Group 1 had a mean spherical equivalent of +0.33 D (range -0.79 to +1.45 D) and Group 2, +1.91 D (range -0.08 to +3.71 D). Best corrected visual acuity remained unchanged in 35.0% in Group 1 and 56.5% in Group 2. Five percent in Group 1 and 7.3% in Group 2 lost more than 2 lines of best corrected visual acuity.

CONCLUSIONS

Laser in situ keratomileusis for hyperopia resulted in less regression, minimal haze, and better predictability and stability than surface photorefractive keratectomy. Preoperative corneal radius appeared to be an important factor in eyes with high hyperopia.

Hyperopia correction by noncontact holmium: YAG laser thermal keratoplasty: five-pulse treatments with 1-year follow-up

BACKGROUND

Previous noncontact holmium (Ho): YAG laser thermal keratoplasty (LTK) studies on correction of low to moderate hyperopia have used treatment algorithms based on ten-pulse, variable-pulse-energy treatment parameters. The purpose of this study was to evaluate the safety, effectiveness, and stability of new five-pulse, constant-pulse-energy treatment parameters for noncontact Ho:YAG LTK.

METHODS

Thirty-nine hyperopic patient eyes [up to +4.75 diopters (D) refractive error] were treated using simultaneous noncontact delivery of Ho:YAG laser energy (Sunrise) with two symmetrical octagonal rings of eight spots per ring and radial spot patterns on centerline diameters of 5 and 6 mm (group A), 6 and 7 mm (group B), or 6.5 and 7.5 mm (group C). Each ring of spots received five pulses of laser light at 5 Hz pulse repetition frequency and a fixed pulse energy of 240 mJ. Thirty of the 39 patient eyes (77%) had 1-year follow-up exams.

RESULTS

At 1 year, the mean Snellen uncorrected distance visual acuity lines gained was 3.7 +/- 0.5/6.8 +/- 2.7/5.3 +/- 3.3 for groups A, B, and C. The mean changes in subjective manifest refraction (spherical equivalent) were -2.08 +/- 1.13 D, -1.83 +/- 0.88 D, -1.22 +/- 0.88 D for groups A, B, and C respectively. None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. There were no clinically significant complications in any patient.

CONCLUSION

This clinical study indicates that five-pulse noncontact LTK treatments of low hyperopia are safe and effective. The stability has to be confirmed with longer follow-up.

Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty: U.S. phase IIA clinical study with 2-year follow-up

PURPOSE

This study was performed to determine the long-term efficacy, safety, and stability of noncontact holmium:yttrium aluminum garnet (Ho:YAG) laser thermal keratoplasty (LTK) for correction of low-to-moderate hyperopia.

METHODS

The authors treated 1 eye each of 28 patients for correction of low-to-moderate hyperopia (up to +3.88 diopters [D] refractive error) using the Sun 1000 Corneal Shaping System (Sunrise Technologies, Inc., Fremont, CA). Treatments were performed with one or two rings of eight spots per ring with centerline diameters of 6 mm (one ring) or 6 and 7 mm (two rings), ten pulses of laser light at 5-Hz pulse repetition frequency, and pulse energies ranging from 208 to 242 mJ. Follow-up was 2 years.

RESULTS

At 2 years after surgery, uncorrected distance visual acuity was improved by 1 or more lines of Snellen visual acuity in 19 (73%) of 26 of the treated eyes. The mean lines gained was 2.5 +/- 2.2/3.3 +/- 2.7 for one- and two-ring treatment groups, respectively. The mean change in spherical equivalent of the subjective manifest refraction was -0.53 +/- 0.33 D/-1.48 +/- 0.58 D for one- and two-ring treatment groups. Regression between 1 and 2 years was 0.01 D and 0.16 D, respectively. In the one-ring treatment group (18 eyes), 13 eyes (72%) had refractive corrections (range, -0.38 to -1.13 D), and 5 eyes (29%) were unchanged (within +0.25 D) relative to their preoperative measurements. In the two-ring treatment group, all eight eyes (100%) had reductions in their hyperopia (range of corrections, -0.38 to -2.25 D). None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. There were no sight-threatening complications.

CONCLUSIONS

This initial U.S. clinical study indicates that noncontact laser thermal keratoplasty treatment of low hyperopia is safe and produces modest but persistent corrections with 2-year follow-up. Expanded studies of this treatment method are warranted.

Holmium laser thermokeratoplasty for the reversal of hyperopia after myopic photorefractive keratectomy

BACKGROUND

Overcorrection following myopic photorefractive keratectomy, with a target of emmetropia, leaving a spherical equivalent of more than 1.0 D of hyperopia is of the order of 1%. This study analyses the efficacy, safety, and 1 year stability of outcome of laser thermokeratoplasty (LTK) carried out on eyes with persistent symptomatic hyperopia following photorefractive keratectomy (PRK) for myopia.

METHOD

11 consecutive eyes in 11 patients underwent LTK using the Technomed Holmium 25, contact holmium:YAG laser system. The mean spherical equivalent before LTK was +2.06 D (SD 1.02 D, range +1.00 D to +4.75 D) based on a non-cycloplegic refraction. Between four and 16 burns were used per eye, depending on the error to be corrected.

RESULTS

The mean spherical equivalent was +0.511 D (SD 0.551) at 1 year. Ten of the 11 eyes were seeing 6/12 or greater, unaided (91%) and nine were within 1.0 D of the target sphere equivalent (82%). Recovery of unaided acuity occurred during the first week in four cases and the first month in the rest. One eye lost greater than one line of best corrected vision (9%), going from 6/5 to 6/7.5 and one gained a line (9%), 6/12 to 6/7.5. No complications occurred during the follow up period.

CONCLUSIONS

In this study of a small number of eyes with hyperopia induced by PRK, LTK appears safe, predictable, and stable for low errors followed for 1 year.