Also, many refractive surgeons now prefer intraocular refractive procedures such as phakic IOL implantation and refractive lens exchange (RLE) for the correction of high myopia, which may provide better visual outcomes and greater refractive stability after surgery.

Among the results of the 2009 International Society of Refractive Surgery (ISRS) survey of refractive surgeons, when asked their procedure of choice for a 30-year-old patient with –10 D of myopia, 43 percent of surgeons identified phakic IOL implantation as their preferred procedure, compared with 40 percent who said they prefer laser vision correction.

Recently, researchers in Spain conducted a retrospective study of 192 highly myopic eyes that underwent PRK (51 eyes) or LASIK (141 eyes) for vision correction. The degree of pre-operative myopia in all eyes in the study ranged from –10.00 to –18.00 D.

All PRK and LASIK procedures were performed between 1992 and 1995 at Instituto Oftalmologico de Alicante (Alicante, Spain). PRK patients had a mean age of 33.96 years, and LASIK patients had a mean age of 32.44 years.

Ten years after surgery, 31.2 percent of eyes in the PRK group and 45.5 percent of eyes in the LASIK group achieved uncorrected visual acuity (UCVA) of 20/40 or better.

Among eyes treated with PRK, 41 percent were within +/–1.00 D of the desired refractive endpoint 10 years after surgery. Among LASIK-treated eyes, this figure was 42.5 percent.

A total of six eyes (14 percent) in the PRK group and seven eyes (6 percent) in the LASIK group lost two or more lines of best spectacle-corrected visual acuity 10 years after the laser eye surgery.

Eyes in both treatment groups showed statistically similar mean regression of myopia over the 10-year study period: –1.28 D in the PRK group and –1.49 D in the LASIK group.

Corneal haze was a significant long-term problem for PRK-treated eyes in the study, according to the researchers.

The study authors said that, based on the results of this and other studies, the use of LASIK for the correction of myopia equal to or greater than –10 D is no longer “routinely advocated,” and that they no longer recommend PRK for the correction of high myopia.

SOURCE: Comparison of LASIK and photorefractive keratectomy for myopia from –10.00 to –18.00 diopters 10 years after surgery. Journal of Refractive Surgery. March 2010.

Researchers in Singapore evaluated the safety, effectiveness and predictability of LASIK for the treatment of varying degrees of nearsightedness among an Asian population.

A total of 37,932 eyes of 19,753 patients were included in the 10-year study. All patients underwent LASIK at the Singapore National Eye Centre between 1998 and 2007.

The mean age of participants in the study was 33 years (range: 21 to 40 years). More than 90 percent of the participants were ethnic Chinese.

Mean pre-LASIK myopia was -5.90 diopters (D), with a range of -3.33 to -8.47 D. The average follow-up time after LASIK was 69 days.

Data gathered at the final follow-up visits revealed:

• More than 90 percent of participants who had LASIK since 2000 achieved uncorrected visual acuity (UCVA) of 20/40 or better.
• 72.8 percent of participants undergoing LASIK since 2000 achieved UCVA of 20/20 or better.
• More than 93 percent of participants who underwent LASIK in the last four years of the study had refractive outcomes that were within 1.00 D of the intended endpoint.
• An improvement in safety was observed over the course of the 10-year study period, with fewest complications occurring in the final year (2007).
• The overall LASIK retreatment rate to improve visual outcomes was 3.8 percent.
• 91 percent of retreated eyes achieved UCVA of 20/30 or better.

The researchers also observed a significant improvement in post-LASIK UCVA and best-corrected visual acuity (BCVA) over the course of the 10-year study.

Regarding LASIK risks and complications, 2.4 percent of eyes lost one line of BCVA on a standard eye chart, and 0.1 percent lost two lines of BCVA.

The authors of the study concluded that LASIK is safe, effective and predictable for the treatment of myopia in Asian eyes.

They also said improvements in LASIK technology over the course of the 10-year study led to more accurate results toward the end of the study period, with an increasing percentage of patients achieving uncorrected visual acuity of 20/15 or better after the procedure.

SOURCE: A 10-year prospective audit of LASIK outcomes for myopia in 37,932 eyes at a single institution in Asia. Ophthalmology. Published online February 15, 2010.

Researchers in Spain recently conducted a 10-year follow-up study of patients who underwent either PRK or LASIK for the correction of -6.00 to -10.00 diopters (D) of nearsightedness.

All procedures were performed with a VISX 20/20 excimer laser at a single surgical center between April 1992 and December 1995.

The study evaluated 34 eyes of 33 patents treated with PRK and 34 eyes of 32 patients treated with LASIK. The two groups were matched for patient age and degree of nearsightedness and astigmatism.

All patients in the study returned to the center for follow-up visits at 3 months, 1 year, 2 years, 5 years and 10 years after surgery for an evaluation their vision and any PRK or LASIK complications.

At 10 years after surgery, the study data revealed:

• 71 percent of the PRK-treated eyes and 88 percent of the LASIK-treated eyes were within 1.00 D of the intended correction.
• Re-treatments were performed on 35 percent of the PRK-treated eyes and 18 percent of the LASIK-treated eyes to achieve satisfactory visual acuity.
• 62 percent of the PRK-treated eyes and 50 percent of the LASIK-treated eyes demonstrated an increase in best spectacle-corrected visual acuity (BSCVA), compared with BSCVA prior to surgery.
• No eye in either group lost more than two lines of BSCVA after surgery.

The most common complication among PRK-treated eyes was mild corneal haze, which was present in one (2.9 percent) of the 34 treated eyes at the end of the study.

The most common complications among LASIK-treated eyes were fine wrinkles (striae) in the corneal flap (2.9 percent) and necrosis or “melting” of the corneal flap edge (2.9 percent). Neither of these problems affected visual acuity at the end of the study.

No eye in either group showed clinical signs of corneal ectasia over the 10-year period of the study.

The researchers concluded that both PRK and LASIK were safe for the correction of -6.00 to -10.00 D of myopia in this group of patients. LASIK demonstrated slightly better predictability and a lower rate of re-treatment than PRK.

They also said that technical improvements in both PRK and LASIK should be taken into account when comparing the results of this study with results of other studies evaluating laser vision correction performed more recently.

Source: Ten years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for moderate to high myopia (control-matched study). British Journal of Ophthalmology. October 2009.

The retrospective study followed 455 eyes that underwent photorefractive keratectomy (PRK) for a period of up to nine years after surgery.

Carole Liernur, MD, presented the results of the study at the annual meeting of the European Society of Cataract and Refractive Surgeons (ESCRS) held last week in Barcelona, Spain.

Prior to PRK, all eyes were myopic, ranging from -1.00 to -10.00 diopters (D) of nearsightedness. In all cases, the PRK procedure was performed with a Nidek 5000 excimer laser.

No patients experienced a detached retina during the follow-up period, and only one patient complained of floaters in one eye. This single case of vitreous floaters was most likely related to the natural history of myopia in this patient rather than the PRK procedure, Dr. Liernur said.

PRK eliminates one LASIK risk

Some clinical studies have reported retinal detachment as an infrequent complication of LASIK eye surgery, especially in patients with high myopia. This study set out to determine if PRK has the same LASIK risks for vitreo-retinal complications (affecting the vitreous and/or retina in the back of the eye).

Since no LASIK-style corneal flap is created during PRK, no suction device is attached to the eye to hold it still for this step. The suction device used in LASIK increases the pressure inside the eye, and when the device is removed after the flap has been created, the internal eye pressure quickly returns to normal.

This significant and sudden change in internal eye pressure may weaken the retina in susceptible individuals, increasing the risk for a retinal detachment during or after LASIK.

This study appears to support the belief that PRK does not pose the same risk of vitreo-retinal complications.

Dr. Liernur also said that risks associated with PRK surgery — specifically, corneal haze and post-operative discomfort — can be alleviated with new surgical techniques and topical pain medications.

SOURCE:  No vitreoretinal complications reported after PRK in long-term case series. Ocular Surgery News website (OSNsupersite.com). September 21, 2009.

The results of the study were published in an educational supplement to the July 2009 issue of Journal of Refractive Surgery sponsored by Optical Express.

LASIK complications: Study design and methods

Data were gathered from the electronic records of 22,900 patients (42,143 eyes) who underwent wavefront-guided LASIK at Optical Express refractive surgery centers in 2008. Of this total, 17,713 patients (32,569 eyes) returned for their scheduled one-month post-operative visit, representing a follow-up rate of 77.3 percent.

All patients had low to moderate myopia with or without astigmatism prior to surgery. The mean spherical equivalent amount of pre-operative myopia was -2.97 diopters (range: -0.37 to -6.00 D).

The average age of the patients was 35.6 years (range: 18 to 69 years).

All LASIK procedures were performed using the STAR S4 IR excimer laser system (Abbott Medical Optics, Santa Ana, Calif.) using a wavefront-guided ablation profile (Advanced CustomVue, AMO). The procedures were performed by 30 LASIK surgeons at 40 Optical Express centers.

Method of flap creation was chosen by the patients after consultation with their doctor. More than 75 percent of patients chose to have flaps created with an IntraLase FS-60 femtosecond laser (AMO). The others chose to have their flaps created with a Moria Evo3 One Use-Plus microkeratome (Moria SA).

Optical Express is Europe’s largest provider of laser vision correction and operates refractive surgery centers in the United Kingdom, Ireland, the Netherlands, Germany, France, Croatia and the United States, according to the company.

Intra-operative LASIK complications

LASIK complications were categorized as either intra-operative (occurring during surgery) or post-operative (occurring some time after surgery).

Of 42,143 nearsighted eyes undergoing wavefront-guided LASIK, the following intra-operative complications were noted:

• Flap creation complications: 22 eyes (1 in 1,916)
• Incorrect treatment: 2 eyes (1 in 21,072)
• Decentered laser ablation: 1 eye (1 in 42,143)

The total number of intra-operative LASIK complications was 25 (0.06 percent).

The most frequent of these complications were related to flap creation and included corneal abrasions, incomplete flaps, buttonhole flaps and “free caps” (a flap without an intact hinge to keep it attached to the cornea).

Flap-related complications appeared to be significantly more common in eyes for which flaps were created with a microkeratome rather than a femtosecond laser, the researchers said.

LASIK complications at one month

Among the 17,713 patients (32,569 eyes) who returned for their scheduled one-month post-operative visit, the following post-operative LASIK complications were noted:

• Dry eyes: 58 eyes (1 in 562)
• Mild diffuse lamellar keratitis (DLK): 58 eyes (1 in 562)
• Glare or halos: 19 eyes (1 in 1,714)
• Flap striae (microscopic folds): 13 eyes (1 in 2,505)
• Delayed healing: 9 eyes (1 in 3,619)
• Moderate or severe DLK: 8 eyes (1 in 4,071)
• Corneal infiltrates: 8 eyes (1 in 4,071)
• Astigmatism greater than 2.00 D: 7 eyes (1 in 4,653)
• Transient light sensitivity: 6 eyes (1 in 5,428)
• Microbial keratitis: 6 eyes (1 in 5,428)
• Significant haze: 5 eyes (1 in 6,514)
• Elevated intraocular pressure (IOP): 4 eyes (1 in 8,142)

Other post-operative complications included: recurrent corneal erosions (3 eyes), epithelial ingrowth (2 eyes), lens changes (2 eyes), corneal ectasia (1 eye) and retinal detachment (1 eye).

The researchers noted that many of the post-operative complications were transient and resolved over time.

Conclusions

The researchers concluded that wavefront-guided LASIK is a safe and effective procedure for the correction of low to moderate myopia and produces a very low rate of complications.

They caution, however, that a limitation of their study is that a large number of patients (22.7 percent) did not attend their scheduled one-month follow-up visit.

Therefore, the actual post-operative LASIK complication rates for the entire cohort of 22,900 patients (42,143 eyes) could be higher or lower than that noted for the 17,713 patients (32,569 eyes) from which these data were gathered.

If you would like to improve your vision through laser eye surgery, perform careful research before committing to any LASIK surgeon and/or procedure. Ask several doctors about the benefits and risks of various laser refractive procedures, such as LASIK, PRK and Presby-LASIK. In addition, inquire about LASIK eye surgery cost, possible insurance coverage and available financing plans.

SOURCE:  One-month outcomes of wavefront-guided LASIK for low to moderate myopia with the VISX STAR S4 laser in 32,569 eyes. Journal of Refractive Surgery. July 2009. (Supplement: Clinical Outcomes and Quality of Care in Refractive Surgery, sponsored by Optical Express.)

Researchers in Italy followed 31 patients who underwent either unilateral or bilateral PRK in 1991 to 1993. A total of 49 nearsighted eyes were included in the study, and check-ups were performed every two years over a period of 14 years.

Patients were divided into two groups — a “low myopia” group of subjects with less than -6.00 diopters (D) of myopia (range: -1.50 to -5.75 D) prior to surgery, and a “high myopia” group of subjects with at least -6.00 D of pre-operative myopia (range: -6.00 to -13.00 D).

PRK study: Results

Results at the final post-operative visit 14 years after surgery included the following:

Low myopia group:

• Mean residual refractive error was -0.17 D of myopia.
• Mean uncorrected visual acuity (UCVA) was between 20/20 and 20/25.
• Mean best spectacle-corrected visual acuity (BSCVA) was 20/20.
• 84 percent of subjects said they were satisfied with the results.

High myopia group:

• Mean residual refractive error was -0.67 D of myopia.
• Mean UCVA was nearly 20/25.
• Mean BSCVA was nearly 20/20.
• 75 percent of subjects said they were satisfied with the results.

In both groups, some degree of corneal haze increased three to six months after surgery, then declined over the subsequent six months.

Complications included minor corneal haze (two eyes), transient unequal pupil size (nine eyes), and iron-containing deposits in the corneal epithelium (four eyes).

No occurrences of ectasia or irregular astigmatism were noted, and no eyes had abnormal endothelial cell count or changes in endothelial cell shape (changes in the inner cell layer of the cornea that could lead to corneal clouding and vision loss). Three patients (9.7 percent) reported night vision problems.

Results achieved six months after surgery were maintained for up to 14 years with no evidence of regression of myopia in eyes in either group.

PRK study: Conclusions

The researchers concluded that PRK is a safe and effective procedure for the correction of myopia.

They noted, however, that results are less predictable for correction of high amounts of myopia.

Editor’s note: The PRK procedures in this study were performed with laser technology and techniques used in 1991 to 1993. It is possible that patients undergoing PRK with today’s modern laser technology may experience fewer night vision problems.

SOURCE:  A 14-year follow-up of photorefractive keratectomy. Journal of Refractive Surgery. June 2009.