Pupil size and quality of vision after LASIK

Comparison of dynamic digital pupillometry and static measurements of pupil size in determining scotopic pupil size before refractive surgery

PURPOSE

To compare 2 digital infrared pupillometers.

SETTING

Anterior Segment Service, Moorfields Eye Hospital, London, England.

METHODS

Eighty-eight eyes of 44 healthy subjects were recruited into the study. The scotopic pupil size was measured with 2 instruments, a digital pupillometer (Procyon) and a Hartman-Shack wavefront aberrometer (Visx WaveScan). Agreement between the instruments was assessed.

RESULTS

There were 21 men and 23 women with a mean age 38.1 years +/- 9.2 (SD) (range 23 to 62 years). The mean scotopic pupil diameter was significantly larger with the WaveScan (6.61 +/- 0.92 mm) than with the Procyon pupillometer (6.40 +/- 0.90 mm), P<.001.

CONCLUSIONS

There was good agreement in measurement of scotopic pupil size between the two instruments. The larger pupil diameter found with the Visx WaveScan than with the Procyon digital pupillometer probably represents the different illumination level used by each instrument, the effects of accommodation, and target fogging.

Cornea-sparing laser in situ keratomileusis: Ablation on the flap

PURPOSE

To evaluate the safety and efficacy of laser ablation on the flap as a treatment for a refractive error.

SETTING

Laser Sight Centres, Sydney, Australia.

METHODS

In this noncomparative case series, 142 treatments were performed in 98 patients using cornea-sparing laser in situ keratomileusis (LASIK) with ablation of the corneal flap and, in some cases, also the stromal bed for spherical equivalent (SE) refractive errors from -0.50 diopter (D) to -12.38 D. The procedure was performed as a primary treatment in 104 eyes, an initial enhancement in 32 eyes, and a second enhancement in 6 eyes. Data were extracted for analysis by retrospective review of patients' charts.

RESULTS

After LASIK, the mean SE was -0.20 D +/- 0.47 (SD) (range +0.87 to -2.35 D) excluding eyes with monovision. The 6 eyes with monovision had a mean SE of -1.90 D with myopia of -1.70 D (range -1.00 to -3.00 D) and mean astigmatism of -0.37 D (range 0 to -0.75 D). Excluding eyes with monovision, 97% of eyes achieved an uncorrected visual acuity of 6/12 or better and 64% of eyes, better than or equal to 6/6. Ninety-six percent were within +/-1.0 D of the intended correction (SE). The safety index was 1.02 and the efficacy index, 0.8.

CONCLUSIONS

Laser ablation of the corneal flap achieved good visual results and enabled preservation of the posterior corneal stroma. This technique may aid the prevention of corneal keratectasia following LASIK.

Correlation of infrared pupillometers and CCD-camera imaging from aberrometry and videokeratography for determining scotopic pupil size

PURPOSE

To compare 2 infrared pupillometers with a videokeratographer and 2 aberrometers for the determination of scotopic pupil size.

SETTING

Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

METHODS

The pupil diameter was measured in 100 eyes of 51 patients after 2 minutes of dark adaptation using the following devices: digital infrared pupillometer (Procyon Instruments Ltd.), handheld infrared pupillometer (Colvard) (Oasis Medical), Zywave aberrometer (Bausch & Lomb), Wasca aberrometer (Asclepion-Meditec-Zeiss), and Orbscan II topography system (Bausch & Lomb Surgical). Measurements taken with the Procyon pupillometer were considered reference values for comparison with the other devices. Statistical evaluation was performed using the Bland-Altmann method for comparison of measurement techniques.

RESULTS

The mean pupil size was 6.10 mm +/- 0.86 (SD) with the Procyon pupillometer, 5.68 +/- 1.07 mm with the Colvard pupillometer, 5.91 +/- 1.01 mm with the Zywave aberrometer with the fixating target turned off, 5.09 +/- 1.14 mm with the Zywave aberrometer with the fixating target turned on, 5.59 +/- 0.99 mm with the Wasca aberrometer, and 3.75 +/- 0.67 mm with the Orbscan topographer. The limits of agreement were smallest for measurements between Procyon and Colvard and largest for measurements between Procyon and Orbscan. The sign test revealed statistically significant differences for all devices compared with the Procyon pupillometer (P<.001 in all cases) except the Zywave aberrometer with the fixating target turned off (P=.13).

CONCLUSIONS

The Zywave wavefront sensor with the fixating target turned off using the study settings and light conditions provided measurements of scotopic pupil diameter that were closest to the reference values (Procyon). With the other devices (Colvard pupillometer, Zywave aberrometer with the fixating target switched on, Wasca aberrometer, and Orbscan topographer), the difference was statistically significant.

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.