Visual, refractive, and subjective outcomes after photorefractive keratectomy for myopia of 6 to 10 diopters using the Nidek laser

Wavefront properties of the anterior and posterior corneal surface after photorefractive keratectomy

PURPOSE

The aim of this study was to evaluate the balance and changes of corneal higher order aberrations (HOAs) after photorefractive keratectomy (PRK).

METHODS

Myopic and myopic-astigmatic patients (89 eyes of 48 patients) were enrolled in this study. A PRK was performed using an Asclepion Meditec MEL 80 G flying-spot excimer laser. The mean ablation depth and diameter were 76.78 μm (±19.40 μm) and 6.0 mm (±0.06 mm), respectively. Before and 1 year after the surgery, uncorrected and best spectacle-corrected visual acuities were determined. Wavefront aberrations of the anterior [root mean square (RMS)-HOA anterior], posterior (RMS-HOA posterior), and total cornea (RMS-HOA total) were measured using a Scheimpflug Camera. Linear piecewise regression analysis was used for correlations between the ablation depth and aberration of the anterior corneal surface. The follow-up time was 1 year.

RESULTS

At baseline, RMS-HOA anterior proved to be significantly higher compared with RMS-HOA total (P < 0.001). After the PRK was performed, the RMS-HOA anterior (P < 0.001) and RMS-HOA total values (P < 0.001) increased significantly; however, RMS-HOA posterior values (P = 0.12) remained stable. Above an ablation depth of 76.78 μm, the RMS-HOA anterior increased 2.4-fold. Uncorrected and best spectacle-corrected visual acuities were 1.0 (20/20) in 95.5% and 98.8% of the patients 1 year postoperatively.

CONCLUSIONS

Aberrations of the posterior corneal surface seem to compensate for wavefront alterations of the anterior cornea, decreasing the amount of wavefront error regarding the total cornea in myopic patients. PRK induced increased HOAs with respect to the anterior corneal surface; however, the posterior surface remained stable. The increase in the HOAs was measured to be significantly larger above 76.78 μm photoablation depth.

Correlation of aberrometry, contrast sensitivity, and subjective symptoms with quality of vision after LASIK

PURPOSE

To compare which parameter category (wavefront data, psychophysical data, or subjective symptoms) predicts best subjective quality of vision after LASIK.

METHODS

Twenty-eight eyes (15 patients) were included. Twenty-three eyes (12 patients) underwent uneventful LASIK; 5 eyes (3 patients) were symptomatic eyes treated with myopic LASIK elsewhere. Mean preoperative spherical equivalent refraction was -4.79+/-1.92 diopters (D) (range: -1.63 to -7.13 D); mean patient age was 36.6+/-7.4 years (range: 18 to 48 years). All examinations were performed 1 month postoperatively. The wavefront error was described with Zernike polynomials (6-mm pupil). Psychophysical tests included high-contrast visual acuity and contrast sensitivity with and without glare at 167 cd/m(-2), 1.67 cd/m(-2), and 0.167 cd/m(-2) with best spectacle correction. Correspondingly, overall subjective quality of vision and frequency of visual symptoms (glare, halos, starbursts, ghosting, blur) were assessed for three lighting conditions (photopic, high-mesopic, and low-mesopic) using a questionnaire with a visual analog scale. For each parameter category and each lighting condition, a multiple stepwise backwards regression model with the overall quality of vision item value as dependent was applied.

RESULTS

Under all lighting conditions, subjective symptom scores predicted subjective quality of vision best (adjusted R2=0.83-0.92) with blur as the main predictor throughout all conditions. Psychophysical tests did not significantly predict postoperative subjective quality of vision. The adjusted R2 for the Zernike coefficients was highest for low-mesopic (0.56) and lowest for photopic conditions (0.31).

CONCLUSIONS

Different parameter categories for the description of optical quality did not predict subjective quality of vision after LASIK equally. Subjective symptom scores had the highest predictability, whereas psychophysical tests with spectacle correction had no predictability. The latter probably do not reflect all dimensions of subjective quality of vision.

Plasminogen activator inhibitor in human tears after laser refractive surgery

PURPOSE

To observe levels of plasminogen activator inhibitor (PAI) in human tears after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

University medical center eye clinic.

METHODS

Tear samples were collected from 46 eyes having PRK and 13 eyes having LASIK immediately before and after surgery and on the first (LASIK), third (PRK), and fifth (PRK) postoperative days. Analyses used enzyme-linked immunoassay, yielding 61 PRK PAI-1 determinations and 146 PRK and 35 LASIK PAI-2 determinations.

RESULTS

All determinations of PRK PAI-1 were below the detection limit of 1 ng/mL of the original tear sample. In the PRK eyes, the mean PAI-2 concentration was 19.8 ng/mL +/- 23.4 (SD) in preoperative tears, 112.7 +/- 60.5 ng/mL immediately postoperatively, 12.1 +/- 19.5 ng/mL after 3 days, and 15.5 +/- 20.4 ng/mL after 5 days. In the LASIK eyes, the mean PAI-2 concentration was 19.0 +/- 33.1 ng/mL preoperatively, 111.5 +/- 69.2 ng/mL immediately postoperatively, and 15.7 +/- 18.8 ng/mL after 1 day.

CONCLUSIONS

The similarity in the general time pattern of PAI-2 after PRK and LASIK suggests commonality in the enzymatic control response to corneal surgical wounding. Taken in the context of previous work, the observed levels of PAI-2 concentration in eyes with and without opacification suggest that in the postsurgical period, PAI-2 is not the controlling mechanism for the later development of corneal opacification and haze.

Visual function of police officers who have undergone refractive surgery

INTRODUCTION

The visual acuity and contrast sensitivity of police recruits and officers was evaluated in both normal and dim illumination conditions to determine whether officers who have had refractive surgery have compromised night vision.

METHODS

The control group consisted of 76 officers and recruits who have not had refractive surgery and the refractive surgery group consisted of 22 officers and recruits who had refractive surgery. Visual acuity and contrast sensitivity were measured under both room illumination and dim illumination. The room illumination test series included high contrast acuity, low contrast acuity and Pelli-Robson contrast sensitivity. The dim illumination test series included high contrast acuity, low contrast acuity, Pelli-Robson contrast sensitivity, license plate number acuity (with and without glare) and the Mesotest.

RESULTS

The general findings were that the refractive surgery group had lower acuity scores on low contrast targets in both room and dim light levels along with a reduction in the Mesotest scores with a glare source compared to the control group.

CONCLUSIONS

Although refractive surgery police recruits and officers had reduced performance on some vision tests, these reductions were small and it is unlikely that their performance on vision related tasks would be compromised, on average. The major concern is the small number of refractive surgery candidates whose results were well outside the range of the non-surgical candidates. Their vision may be unacceptable for policing.

Efficacy of Measuring Visual Performance of LASIK Patients under Photopic and Mesopic Conditions

Introduction: The aim of the study was to compare the visual performance of LASIK eyes measured using high-contrast logMAR letter charts under bright (photopic) and dim (mesopic) conditions. Materials and Methods: A total of 46 subjects (35 ± 8 years of age) undergoing LASIK procedures were recruited for the study. The best spectacle-corrected visual acuity (BSCVA) of each subject was measured using the high-contrast ETDRS logMAR chart under photopic and mesopic conditions at 3 visits: preoperative (Pre), 1 month postoperative (Post1) and 3 months postoperative (Post3). The differences in logMAR scores for the right eyes only were analysed for the Pre-Post1 (n = 46), Pre-Post3 (n = 18) and Post1-Post3 (n = 16) comparisons. Results: The logMAR scores of subjects were worse at the 1-month postoperative visit than preoperatively, and improvement in visual performance was seen at the 3-month postoperative visit. These changes in visual performance became more evident under mesopic conditions. The means and standard errors of the differences in logMAR scores for the Pre-Post3 (0.097 ± 0.020) were slightly larger than those of the Pre-Post1 (-0.067 ± 0.019) and Post1-Post3 (0.031 ± 0.012) comparisons. Under mesopic conditions, the visual performance of the subjects was statistically significant for the 3 comparisons, but not under photopic conditions. Conclusion: High-contrast logMAR chart performed under mesopic conditions has the potential to replace visual acuity measured under photopic conditions in providing more reliable representation of postoperative visual outcomes of LASIK eyes. Eye doctors should consider performing this vision test routinely to gauge the success of LASIK surgery. Key words: Contrast sensitivity, logMAR chart, Visual acuity

Functional outcome and patient satisfaction after Artisan phakic intraocular lens implantation for the correction of myopia

PURPOSE

To determine patient satisfaction after Artisan phakic intraocular lens (PIOL) implantation to correct myopia.

DESIGN

Non-comparative prospective case series.

METHODS

One hundred twenty eyes of 60 patients who had undergone Artisan PIOL implantation to correct myopia were analyzed. A validated questionnaire that consisted of 66 satisfaction items were self-administered by patients 12 months after surgery. Clinical parameters (PIOL decentration, the difference between pupil size and PIOL optical zone, and optical aberrations) were measured. Main outcome measures of satisfaction scale scores (global satisfaction, quality of uncorrected and corrected vision, night vision, glare, day and night driving) were analyzed. Correlations with clinical parameters were obtained.

RESULTS

After surgery, 98.3% of patients were satisfied, and 73.3% of patients considered their night vision to be the same or better; 44.1% of patients reported more bothersome glare. The night vision score correlated with spheric aberration (r = -0.303; P = .020). The glare score correlated with the difference between scotopic pupil size and PIOL optical zone (r = -0.280; P = .030) and vertical coma (r = -0.337; P = .009). The night driving score correlated with postoperative spheric equivalent (r = 0.375; P = .009), total root mean square aberrations (r = -0.337; P = .017), higher order root mean square aberrations (r = -0.313; P = .027), and vertical coma (r = -0.297; P = .036).

CONCLUSION

Overall satisfaction after Artisan PIOL implantation for myopia is excellent. The quality of night vision and night driving were related to scotopic pupil size, individual higher order aberrations, and residual refractive error.

Assessing the Value of Laser in situ Keratomileusis by Patient-reported Outcomes Using Quality of Life Assessment

PURPOSE

To assess the value of laser in situ keratomileusis (LASIK) by patient-reported outcomes using quality of life assessment.

METHOD

This study included 288 consecutive patients treated by LASIK between July and December 2001 at two eye clinics. A Myopia-specific Quality of Life Questionnaire was developed in this study. The baseline quality of life corresponding to the situation where refractive error was corrected by glasses or contact lenses before LASIK treatment was evaluated by self-administered questionnaire. The evaluation was repeated at 4 days, and 1, 3, and 6 months after LASIK treatment. All question items were rated on a scale ranging from 1 (maximal dysfunction) to 5 (minimal dysfunction).

RESULTS

Factor analysis identified 34 questions in 4 subscales-visual function, visual symptoms, social role function, and psychological well-being. The Myopia-specific Quality of Life Questionnaire subscales proved to be internally consistent (Cronbach alpha = 0.70-0.95). Criterion validity was assessed by evaluating Spearman correlation between the overall or domain-specific quality of life and traditional measures of patient status. Overall Myopia-specific Quality of Life Questionnaire score changed from 3.21 preoperatively to 3.76, 4.00, 4.07, and 4.11 at 4 days, and 1, 3, and 6 months after surgery, respectively. Social role function showed the biggest improvement (score change: 1.51, P < .05), followed by psychological well-being (0.90, P < .05), visual function (0.72, P < .05), and visual symptoms (0.49, P < .05). Regression analysis results showed that the degree of uncorrected visual acuity, discomfort associated with myopia preoperatively, and location of eye center were significant factors affecting the magnitude of changes in quality of life after LASIK.

CONCLUSIONS

This study confirms that the value of LASIK went beyond the clinical achievement of refractive correction and extended to the improvement of quality of life.

Lasik, photokéractectomie réfractive et qualité de vision : étude des facteurs pronostiques et enquête de satisfaction

PURPOSE

To confirm the clinical interest of pupillary diameter measurement for selecting indications and determining surgical protocols, to look for clinical factors predisposing to night vision symptoms, and to the assess patient satisfaction level for photoablation techniques not based on aberrometry.

METHODS

This retrospective study was conducted on 111 consecutive myopic patients (219 eyes, with a mean spherical equivalent of -4.25+/-1.84 D); they underwent Lasik (91.3% of cases) or photorefractive keratectomy, after having their pupillary diameter measured by the Colvard pupillometer. Clinical data were collected from medical files, and an anonymous questionnaire was sent in order to assess quality of vision and postoperative satisfaction.

RESULTS

Preoperative aims were reached (r=0.41, p<0.0001). The response rate for the questionnaire was 81.1%. Daytime vision was the same or better for 91.1% of the patients, but 25.6% had worse night vision than before. Night vision symptoms were mentioned by 46.7% of the patients, and the most frequent complaint was halos. However, 97.8% of the patients declared themselves as satisfied and would recommend such surgery to their family and friends. A preoperative myopia greater than 4.50D (RR=1.52, p<0.05) and a postoperative keratometry greater than 8.44 mm (RR=1.62, p<0.05) were risk factors for having night vision symptoms, but pupillary diameter was not a risk factor.

CONCLUSION

This survey gives an indirect confirmation of the interest of scotopic pupillary diameter measurement and taking it into account in photoablation protocols. However, night vision symptoms remain frequent but do not influence patient satisfaction. Knowledge of risk factors and technical progress should provide a better quality of vision after Lasik.

Plasminogen activator activity and inhibition in rabbit tears after photorefractive keratectomy

Plasminogen activator is a normal component of tear fluid that plays a role in corneal wound healing processes. This work examines whether inhibitor-induced low levels of plasminogen activator activity (PAA) during corneal re-epithelialization after excimer laser photorefractive keratectomy (PRK) correlates with the eventual occurrence of haze in rabbit eyes. Tear samples were collected with glass capillaries from 16 eyes of eight New Zealand rabbits, using i.m. injection of pilocarpine hydrochloride for stimulation. Tears were collected before and after PRK surgery, and then daily for 5 days, and every fourth day thereafter for 3 months. Both eyes underwent PRK treatment. One eye of each rabbit was treated as a control while the contralateral eye was treated with aprotinin, a serine protease inhibitor, over the first 7 days. PAA in the tear samples was measured by a spectrophotometric method using human plasminogen and chromogenic peptide substrate S-2251. For the eight control eyes after PRK, the PAA values were significantly lower (day 1) and higher (days 2 and 3) than the equilibrium PAA (p<0.001). The corneas remained clear in each of these control eyes. For the eight contralateral aprotinin-treated eyes after PRK, the PAA values on days 1-7 were significantly lower than the equilibrium PAA (p<0.001). All eight of these aprotinin-treated eyes developed corneal haze after 2 months. There was no significant difference (p=0.06) between control and aprotinin-treated eyes for the equilibrium PAA after 19 days. We conclude that a corneal wound healing abnormality (haze) develops in rabbit eyes after PRK when PAA levels are reduced using aprotinin for a week following PRK.

Kersley Lecture

PURPOSE

Media publicity has made patients increasingly aware that surgical vision correction is available. This article gives an overview on refractive surgery and contact lenses.

METHODS

Contact lens and refractive surgery possibilities are highlighted for patients with myopia, hyperopia, astigmatism, presbyopia, aphakia, and keratoconus. Therapeutic, pediatric, and cosmetic indications are discussed.

RESULTS

Refractive surgery is beneficial for low refractive errors. The use of contact lenses is mandatory in cases of monovision and strabismus before refractive surgery and beneficial for therapeutic use postoperatively.

CONCLUSION

Although many patients are always best corrected with contact lenses, only the right synergism of contact lenses and refractive surgery will benefit patients.

Pupil size and quality of vision after LASIK

PURPOSE

To evaluate factors related to the quality of vision after LASIK.

DESIGN

Survey study.

PARTICIPANTS

One hundred consecutive patients.

INTERVENTION

LASIK with a 6.0-mm elliptical ablation pattern without transition zone to treat mild to moderate myopia or astigmatism (preoperative manifest spherical equivalent [MSE], -4.79 +/- 1.33 diopters [D]; range, -2.88 to -9.25 D). The second eye was treated 1 month after the first.

MAIN OUTCOME MEASURES

Completed questionnaires assessing night vision problems (glare, haze, and halo symptoms) before surgery and at 1, 3, and 6 months after surgery in 97, 75, 81, and 66 subjects, respectively. Mesopic pupil size and preoperative and postoperative variables were analyzed with questionnaire data using an analysis of variance (ANOVA) and multivariate regression analysis.

RESULTS

Patients with large mesopic pupils had significantly more reports of glare, haze, and halo than did those with smaller pupils in the treated eye at 1 month after surgery (P=0.02, P=0.03, and P=0.02, respectively ANOVA) and of glare at 3 months (P=0.05). Significant predictors of symptoms at 6 months, identified through multivariate regression analysis, included preoperative MSE (for glare and haze), preoperative contrast acuity (glare), postoperative uncorrected visual acuity (UCVA; haze), and residual cylinder (haze). Together, these factors accounted for only 19% of the overall variability in glare and 37% of the variability in haze responses. No relationship between pupils and symptoms was noted at 6 months after surgery in either the ANOVA or regression analysis group.

CONCLUSIONS

Patients with large pupils had more quality of vision symptoms in the early postoperative period, but no correlation was observed 6 months after surgery. Factors related to long-term symptoms include the level of treatment (preoperative myopia), preoperative contrast acuity, postoperative UCVA, and residual cylinder. Most of the variability in visual quality could not be explained by preoperative or clinical outcome measures, including pupil size.

Visual performance with night vision goggles after photorefractive keratectomy for myopia

OBJECTIVE

To evaluate visual performance and resolution through night vision goggles (NVG) before and after photorefractive keratectomy (PRK).

DESIGN

Nonrandomized, comparative (self-controlled) trial.

PARTICIPANTS

Nineteen patients (38 eyes) of active-duty US Army Special Forces soldiers.

INTERVENTION

PRK for myopia and astigmatism.

MAIN OUTCOME MEASURES

Visual acuity with best optical correction was measured preoperatively and postoperatively (3 months) using acuity charts of various contrast (100%, 10%, 2.5%, 1.25%). Preoperative and postoperative (3 month) uncorrected and best-corrected visual resolutions through NVGs were assessed using a high contrast tribar chart presented at four light levels (3.44 x 10(-3), 1.08 x 10(-3), 1.04 x 10(-4), 1.09 x 10(-5) foot Lamberts) simulating a range of night sky conditions. Subjects were trained before testing.

RESULTS

Uncorrected visual acuity at the 3-month postoperative assessment was greater than or equal to 20/20 in 33 of 38 (86.8%) eyes. No eyes lost 2 or more lines of best spectacle-corrected visual acuity. Preoperative and 3-month postoperative best-corrected low-contrast acuity measurements showed no significant differences at all levels of resolution. Preoperative visual resolution through NVGs decreased systematically with decreasing night sky condition. Visual acuities before PRK were reduced without optical correction. Postoperative visual performance with NVGs (without optical correction) equaled or exceeded performance preoperatively with best correction.

CONCLUSIONS

This prospective case series provides data on the safety and efficacy of PRK with respect to visual performance under night sky conditions using NVGs. There was no significant loss of visual acuity across a range of contrast levels 3 months postoperatively. There was no change in best-corrected NVG visual resolution postoperatively, whereas uncorrected visual resolution was significantly enhanced compared with preoperative levels. This improvement may translate into better function for soldiers who are unable to or choose not to use optical correction in operational environments.

Night vision disturbances after corneal refractive surgery

A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.

Relation between corneal haze and transforming growth factor-beta1 after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE

To investigate the relation between corneal haze formation and transforming growth factor-beta (TGF-beta) after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.

METHODS

White rabbits were divided into 4 groups, with each group receiving 1 of the following surgeries: manual epithelial abrasion, PRK, lamellar keratotomy, or LASIK. The degree of corneal haze was quantitatively analyzed by measuring the light scattering intensity of corneas before and 4 and 12 weeks after surgery. The expression of type IV collagen and TGF-beta1 in the corneas at baseline and at 4 weeks was examined immunohistochemically.

RESULTS

The light scattering intensity was significantly greater 4 and 10 weeks after PRK. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not influence the light scattering intensity of the corneas. Type IV collagen was detected in the basal lamina of the corneal epithelium and in Descement's membrane in the normal cornea. After epithelial abrasion, there was no change in the distribution of type IV collagen. Four weeks after PRK, the expression of type IV collagen was detected in the subepithelial layer of the laser-ablated area. Four weeks after lamellar keratotomy, type IV collagen was linearly and fragmentarily detected in the corneal stroma. Four weeks after LASIK, type IV collagen was linearly and continuously detected in the corneal stroma and was detected slightly in the subepithelial region of the laser-ablated area. In the normal corneas, the expression of TGF-beta1 was not detected in the keratocytes. Four weeks after PRK, the expression of TGF-beta1 increased in the keratocytes that proliferated in the subepithelial fibrous layer. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not change the expression pattern of TGF-beta1 in the keratocytes.

CONCLUSION

The multiplier effect of epithelial abrasion and excimer laser ablation in PRK may increase the expression of TGF-beta1 in keratocytes and induce corneal haze.

Vision-specific quality of life and modes of refractive error correction

PURPOSE

Many studies currently use surveys to assess patients' reports of vision-specific quality of life to determine the impact of the disease or the most appropriate mode of treatment. One such instrument, the National Eye Institute Visual Function Questionnaire (NEI-VFQ), was developed to assess vision-related quality of life with respect to emotional well-being and social function as well as difficulty with tasks and symptoms. We administered the NEI-VFQ to 218 subjects free of eye disease to see if the survey was sensitive enough to detect differences in three modes of refractive error correction: spectacles, soft contact lenses, and rigid contact lenses.

METHODS

Surveys were administered to 117 rigid contact lens wearers, 51 spectacle wearers, and 50 soft contact lens wearers. Kruskal-Wallis one-way analysis of variance was conducted to determine significant differences in each of the subscales.

RESULTS

The Peripheral Vision subscale score (mean +/- SD) was 92.6 +/- 15.2 for the spectacle wearers, 100.0 +/- 0.0 for the soft contact lens wearers, and 98.3 +/- 7.1 for the rigid gas-permeable contact lens wearers; the spectacle wearers' Peripheral Vision score was significantly lower than the other two groups (Wilcoxon rank sum, p < 0.003 for both). The spectacle wearers (96.6 +/- 9.2) also had a significantly lower Dependency subscale score than the rigid contact lens group (99.7 +/- 1.5) (Wilcoxon rank sum, p = 0.001). There were no significant differences between the three groups detected in the mean of any of the other subscale scores. At least 50% of the subjects reported the maximum score for 6 of the 11 subscales. Given our sample size, we have 100% power to detect a difference of 10 points with a SD of 10 at the alpha = 0.05 level.

CONCLUSION

The NEI-VFQ is not appropriate for detecting significant differences in vision-related quality of life among spectacle, soft contact lens, and rigid gas-permeable contact lens wearers, primarily due to maximum ratings by many of the subjects.