Photorefractive Keratectomy for Compound Myopic Astigmatism With an Eye Cup Erodible Mask Delivery System

Compound Myopic Astigmatism Correction using a Mask In-the-Rail Excimer Laser Delivery System. Preliminary Results

PURPOSE

The latest development in the erodible mask technology is an excimer laser containing the mask in the laser optical pathway. This paper reports the results of the first human series of consecutive treatments performed for the correction of compound myopic astigmatism.

METHODS

We have treated 83 eyes. Spherical equivalent attempted correction ranged between -1.75 and -11.75 D (mean -7.07+/- 2.45 D), astigmatic attempted correction ranged between -1.00 and -5.00 D (mean -2.42+/- 1.02 D). The sphere correction was made by diaphragm using a multi-zone software with three ablation zones: 100% of the total attempted correction for the central 5.0 mm zone, 70% for the second 6.0 mm zone, 30% for the outer 6.5 mm zone. Cylinder correction was made sequentially after myopic correction using the appropriate mask.

RESULTS

One month after treatment, mean refractive error was + 1.07 +/- 1.24 D (range + 4.50/-1.75 D) for spherical equivalent, and -0.49 +/- 0.57 D (range + 0.75/-2.00 D) for astigmatism. Forty-eight eyes (57.8%) had uncorrected visual acuity of 20/40 or better. At six months, mean refractive error was +0.42 +/- 0.97 D (range + 3.75/-1.00 D) for spherical equivalent, and -0.44 +/- 0.51 D (range +0.25/-3.00 D) for astigmatism. Vector analysis showed that 57 eyes (68.7%) had 5 or less degrees rotation. Seventy-two (86.7%) and 54 eyes (65.1%) had uncorrected visual acuity equal or better than 20/40 and 20/25 respectively. One eye (1.2%) showed a best corrected visual acuity loss of more than one line, but 8 eyes (9.6%) had a gain of more than one line. One-year results on a smaller series (33 eyes) overlap with the six-month results.

CONCLUSIONS

The mask in-the-rail excimer laser delivery system appears to be effective and predictable in the correction of compound myopic astigmatism. We observed no significant regression of the astigmatic correction over time. Longer follow-up on larger series is necessary to draw final conclusions.

Hyperopia Correction Using an Erodible Mask Excimer Laser Delivery System Coupled to an Axicon: Preliminary Results

Purpose.

This paper presents the results of the first human trial on the correction of hyperopia using an erodible mask excimer laser delivery system coupled to an axicon.

Methods.

We treated 17 eyes of 17 patients (age range 34–62 years) for the correction of +3.21 ± 1.04 D (range +1.00 to +4.00 D). The hyperopic correction was made using an erodible mask inserted on the laser optical pathway, to produce a circular ablation measuring 6.5 mm in diameter. An axicon was then used to create a blend transition zone from 6.5 mm up to 9.4 mm in diameter. Eyes were evaluated at one, three and six months after surgery.

Results.

Reepithelization was always observed by the fifth postoperative day, despite the large area of deepithelization (diameter 9.5 mm). Mean refractive error one month after treatment was −2.44 ± 1.59 D (range 0.00 to −6.50 D). Five eyes (29.4%) had a best corrected visual acuity loss more than two to three lines; all eyes showed mild annular haze not involving the central part of the cornea. Six months after treatment, mean refractive error was −0.88 ± 0.99 D (range +0.50 to −3.00 D). Compared to preoperative status, 13 eyes (76.5%) showed an improvement in uncorrected distance visual acuity (1–8 lines), and 14 eyes (82.4%) showed an improvement in uncorrected vision at reading distance (3–7 lines). Two eyes (11.7%) showed a best corrected visual acuity loss of two of three lines.

Conclusions.

These preliminary results indicate this approach is effective in reducing hyperopia, while its predictability has still to be proved in a larger treatment group with longer follow-up. A cautious approach to this technique is still advisable, especially for higher hyperopic corrections, in view of the large best corrected visual acuity loss seen in two eyes at six months.

Photorefractive Keratectomy for Hyperopia Using an Erodible Disc and Axicon Lens: 2-Year Results

BACKGROUND

This paper presents the results over a 2-year follow-up of the first human trial of photorefractive keratectomy (PRK) for correction of hyperopia using an erodible disc excimer laser delivery system (Summit) coupled to an axicon lens.

METHODS

We treated 25 eyes of 21 patients for a mean correction of +3.38 +/- 0.97 D (range, +1.00 to +4.00 D). The hyperopic correction was made using an erodible disc inserted on the laser optical pathway; an axicon lens was then used to create a blend transition zone. Eyes were evaluated at 1, 3, 6, and 12 months after surgery. For a smaller series of 11 eyes, we also present 24-month results.

RESULTS

Mean refractive error 1 month after treatment (25 eyes) was -2.35 +/- 1.55 D (range, +1.00 to -6.50 D). Eight eyes (32%) had a spectacle-corrected visual acuity loss greater than 1 line. Twelve months after treatment, mean spherical equivalent refraction was -0.47 +/- 0.80 D (range, +1.25 to -2.25 D). Nineteen eyes showed an improvement (range, 3 to 8 lines) in uncorrected distance visual acuity and 23 showed improvement in uncorrected vision at reading distance (1 to 7 lines).

CONCLUSION

This technique proved effective in reducing hyperopia, but predictability must be demonstrated in a larger treatment group. Safety was confirmed by the absence of delayed reepithelialization and the absence of spectacle-corrected visual acuity loss greater than 1 line at 1 year after surgery.

Excimer laser treatment of myopic astigmatism. A comparison of three ablation programs

OBJECTIVE

The purpose of the study was to evaluate the precision, accuracy, and safety of three different modes of excimer laser surgery for myopic astigmatism.

DESIGN

A prospective interventional case series.

PARTICIPANTS

A total of 150 eyes with compound myopic astigmatism were treated.

INTERVENTION

Ablation programs included the VISX Twenty/Twenty excimer laser using either the sequential mode (58 eyes) or the elliptical mode (54 eyes) and the Technolas-Chiron Keracor 116 hybrid scanning laser (38 eyes).

MAIN OUTCOME MEASURES

Reduction in cylinder and sphere, vector analysis (polar values), uncorrected visual acuity, and best spectacle-corrected visual acuity were evaluated at 1, 6, and 12 months.

RESULTS

By 12 months, sphere was reduced by 95.1%, 87.7%, and 75% in low-astigmatism eyes treated with the VISX sequential, VISX elliptical, and Technolas modes, respectively, and by 92.2%, 98%, and 77.6% in high-astigmatism eyes. By 12 months, cylinder was reduced by 51.5%, 72.2%, and 36.3% in low-astigmatism eyes and by 70%, 78%, and 45.6%, respectively, in high-astigmatism eyes. Vector analysis showed that the elliptical treatment produced more significant reductions in mean polar values than the other two treatments at various timepoints.

CONCLUSION

These results suggest that the ablation approach may influence the clinical result.

Excimer laser correction of astigmatism with multipass/multizone treatment. The Melbourne Excimer Laser Group

PURPOSE

To evaluate the accuracy of excimer laser correction of myopic astigmatism by multipass/multizone photoastigmatic refractive keratectomy (PARK).

SETTING

Tertiary referral ophthalmic hospital with an associated private laser facility.

METHODS

This study comprised a consecutive series of 332 eyes of 289 patients who were followed for 6 months. All patients were 18 years or older, had stable myopic astigmatism (up to a -19.0 diopters [D] spherical equivalent [SE] at the spectacle plane), and had a best corrected visual acuity of at least 20/60 in both eyes. All eyes were treated with a VISX Twenty-Twenty excimer laser. The correction was divided between ablation zones using a multipass/multizone treatment paradigm based on the amount of myopia and astigmatism. Patients were examined 1 week, and 1, 3, and 6 months after surgery.

RESULTS

Analysis of the mean percentage of spherical correction across the range of myopic preoperative SEs treated demonstrated 90% correction for most amounts of myopic astigmatism. Eyes with low myopia (mean preoperative SE < or = -5.0 D) treated with < or = -1.0 diopter cylinder (DC) of astigmatism achieved a mean percentage of spherical correction of 91% versus 93% in eyes with high myopia (> -5.0 D mean preoperative SE). Eyes with low myopia treated with > -1.0 DC of astigmatism achieved a mean percentage spherical correction of 90% versus 89% in eyes with high myopia. The differences between the two groups were not statistically significant. Patients with high relative cylinder (> 80% of total sphere treated) achieved comparable results. Analysis of the astigmatic component of the treatment, independent of the spherical result, showed a trend toward overcorrection in the high myopia group with less than -1.0 DC and a mean astigmatic correction of 89 and 98%, respectively, in the low and high myopic astigmatism groups. The mean angle of error was +2.0 degrees.

CONCLUSION

Multipass/multizone PARK for myopic astigmatism demonstrated a high degree of predictability and stability with desirable results for low and high levels of astigmatism across the range of myopic astigmatism treated by surface ablation.