Influence of pupil and optical zone diameter on higher-order aberrations...

After wavefront-guided myopic LASIK

 

J Cataract Refract Surg. 2005; 31(12):2272-80 (ISSN: 0886-3350)

Bühren J; Kühne C; Kohnen T

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

 

 

PURPOSE: To investigate the influence of pupil and optical zone (OZ) diameter on higher-order aberrations (HOAs) after myopic wavefront-guided laser in situ keratomileusis (LASIK).

 

METHODS: Twenty-seven myopic eyes of 19 patients were included. The mean preoperative spherical equivalent was -6.86 diopters (D) +/- 1.24 (SD) (range -4.25 to -9.5 D); the mean planned OZ diameter was 6.26 +/- 0.45 mm (range 5.7 to 7.1 mm). All patients had uneventful wavefront-guided LASIK (Zyoptix version 3.1, Bausch & Lomb) and an uncomplicated follow-up of 12 months. Wavefront measurements were performed with a Hartmann-Shack sensor in maximum mydriasis preoperatively and 12 months after LASIK. Wavefront errors were computed for pupil diameters (PDs) of 3.0, 3.5, 4.0, 5.0, 6.0, and 7.0 mm for the individual OZ diameter and for the individual mydriatic PD (7.93 +/- 0.46 mm). The impact of the relationship between pupil diameter and OZ diameter (fractional clearance [FC]) on HOA was described and quantified using curvilinear regression with a 4th-order polynomial fit.

 

RESULTS: There was a reproducible relationship between FC and the amount of induced HOA. The change in HOA root mean square and primary spherical aberration (Z(4)0) was significantly correlated with FC. If the OZ was 16.5% larger than the pupil (FC = 1.17), only half the amount of HOA was expected to be induced than if the OZ equaled the pupil. In contrast, an OZ that was 9% smaller than the pupil (FC = 0.91) resulted in an HOA induction 50% higher than at FC = 1.

 

CONCLUSION: The OZ zone to pupil ratio (fractional clearance) had a significant impact on HOA induction after wavefront-guided LASIK.

Effect of pupil size on visual function under monocular and binocular conditions in LASIK

And non LASIK patients

J Cataract Refract Surg 2003; 29:275–278

Brian S. Boxer Wachler, MD 

Purpose: To compare binocular and monocular vision in patients treated with laser in situ keratomileusis (LASIK) and in non-LASIK patients.  

Setting: Jules Stein Eye Institute, Los Angeles, California, USA.  

Methods: This comparative cross-sectional study comprised 20 postoperative LASIK patients and 20 non-LASIK ametropic patients. LogMAR visual acuity, contrast sensitivity, and infrared pupillometry were tested. Outcome measures were better-eye monocular acuity, binocular acuity, better-eye contrast sensitivity, binocular contrast sensitivity, and pupil diameter under monocular and binocular conditions.  

Results: Binocular visual acuity and contrast sensitivity were statistically significantly better than the visual acuity in the better eye (P = .0047 to <.0001) in both patient groups. Pupil diameter was statistically significantly smaller under the binocular condition than the monocular condition (P <.0001) in both groups.  

Conclusions: Monocular testing induced larger pupil diameters, which was associated with reduced vision compared to binocular measurements in LASIK and non-LASIK patients.

Pupil measurement using the Colvard pupillometer...

...and a standard pupil card with a cobalt blue filter penlight. 


 

J Cataract Refract Surg. 2006 Feb;32(2):255-60.

Chaglasian EL, Akbar S, Probst LE.

Illinois Eye Institute, Illinois College of Optometry, Chicago, TLC Vision, Westchester, Illinois 60616, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.

PURPOSE: To compare scotopic pupil measurements obtained with a Colvard pupillometer with measurements taken with a printed pupil gauge and penlight with a cobalt blue filter attachment in mesopic and scotopic luminance.

 

SETTING: The Illinois Eye Institute, Chicago, Illinois, USA.

 

METHODS: Pupil measurements were taken of both eyes of 38 patients (76 eyes). Any subject presenting with anterior segment disease, fixed or dilated pupils, iris abnormalities, or a history of eye disease or eye trauma was excluded. At a mesopic luminance of 2.11 foot-candles, pupil measurements were taken with a Bernell pupil card and penlight with a cobalt blue filter attachment. At a scotopic luminance of less than 2.00 foot-candles, pupil measurements were taken with the Bernell card system and the Colvard pupillometer.

 

RESULTS: In mesopic luminance, the mean pupil diameter was 5.17 mm (range 3.0 to 7.5 mm) with the Bernell card method. The mean difference between the Colvard in scotopic luminance and the Bernell card system in mesopic luminance was -0.04 mm (P = .0831). In scotopic luminance, the mean pupil diameter was 6.32 mm (range 4.0 to 8.0 mm) with the Bernell card method and 5.13 mm (range 3.0 to 7.5 mm) with the Colvard pupillometer, with a mean difference of -1.18 mm (P<.0001). The limits of agreement between the mesopic Bernell card system and the Colvard pupillometer were small (-0.32 to 0.24), whereas the limits of agreement between the scotopic measurements of both techniques were large (-2.18 to -0.18).

 

CONCLUSIONS: Under both illuminance conditions, the Bernell card system with the cobalt filter measured a larger pupil size than the Colvard pupillometer. The measurement differences between the techniques were most pronounced at the lower illumination. The limits of agreement were larger under the lower illumination, indicating more variation between techniques. This study suggests that the Bernell card system with cobalt illumination provides a generous measurement of the pupil size compared with the Colvard pupillometer, which makes it an appropriate and cost-effective screening tool for refractive surgery evaluation.

Pupillary dilation from 3 to 7 mm in post-refractive surgery patients

 found to cause 28 to 46 fold increase in aberrations!

 

http://www.ncbi.nlm.nih.gov/entrez/...st_uids=9932992

American Journal of Ophthalmology

Volume 127, Issue 1 , January 1999, Pages 1-7

Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis.

Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury MA.

Department of Ophthalmology, University of Tokyo School of Medicine, Japan. This email address is being protected from spambots. You need JavaScript enabled to view it.

 

PURPOSE: To compare changes in the corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis.

 

METHODS: In a prospective randomized study, 22 patients with bilateral myopia received photorefractive keratectomy on one eye and laser in situ keratomileusis on the other eye. The procedure assigned to each eye and the sequence of surgery for each patient were randomized. Corneal topography measurements were performed preoperatively, 2 and 6 weeks, 3, 6, and 12 months after surgery. The data were used to calculate the wavefront aberrations of the cornea for both small (3-mm) and large (7-mm) pupils.

 

RESULTS: Both photorefractive keratectomy and laser in situ keratomileusis significantly increased the total wavefront aberrations for 3- and 7-mm pupils, and values did not return to the preoperative level throughout the 12-month follow-up period. For a 3-mm pupil, there was no statistically significant difference between photorefractive keratectomy and laser in situ keratomileusis at any postoperative point. For a 7-mm pupil, the post-laser in situ keratomileusis eyes exhibited significantly larger total aberrations than the post-photorefractive keratectomy eyes, where a significant intergroup difference was observed for spherical-like aberration, but not for coma-like aberration. This discrepancy seemed to be attributable to the smaller transition zone of the laser ablation in the laser in situ keratomileusis procedure. Before surgery, simulated pupillary dilation from 3 to 7 mm caused a five- to six-fold increase in the total aberrations. After surgery, the same dilation resulted in a 25- to 32-fold increase in the photorefractive keratectomy group and a 28- to 46-fold increase in the laser in situ keratomileusis group. For a 3-mm pupil, the proportion of coma-like aberration increased after both photorefractive keratectomy and laser in situ keratomileusis. For a 7-mm pupil, coma-like aberration was dominant before surgery, but spherical-like aberration became dominant postoperatively.

 

CONCLUSIONS: Both photorefractive keratectomy and laser in situ keratomileusis increase the wavefront aberrations of the cornea and change the relative contribution of coma- and spherical-like aberrations. For a large pupil, laser in situ keratomileusis induces more spherical aberrations than photorefractive keratectomy. This finding could be attributable to the smaller transition zone of the laser ablation in the laser in situ keratomileusis procedure.

Pupillary dilation from 3 to 7 mm in post - PRK patients

 found to cause 25-to 32-fold increase in aberrations!

 

 

http://www.ncbi.nlm.nih.gov/entrez/...st_uids=9932992

 

American Journal of Ophthalmology

 

Volume 127, Issue 1 , January 1999, Pages 1-7

Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis.

Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury MA.

Department of Ophthalmology, University of Tokyo School of Medicine, Japan. This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Excerpt: Before surgery, simulated pupillary dilation from 3 to 7 mm caused a five- to six-fold increase in the total aberrations. After surgery, the same dilation resulted in a 25- to 32-fold increase in the photorefractive keratectomy group and a 28- to 46-fold increase in the laser in situ keratomileusis group.

Pupil size and night vision disturbances after LASIK for myopia

 
Acta Ophthalmol Scand. 2004 Aug;82(4):454-60.
Helgesen A, Hjortdal J, Ehlers N.

Department of Ophthalmology, Arhus University Hospital, Arhus, Denmark.

 
 
PURPOSE: To examine whether standardized, preoperative evaluation of pupil sizes can predict the risk of night vision visual disturbances after bilateral laser in situ keratomileusis (LASIK) for myopia.
 
 
METHODS: A prospective study was carried out involving 46 patients who underwent bilateral LASIK for myopia. Pupil sizes were measured before surgery using an infrared pupillometer under standardized settings. Pre- and postoperative refraction and best spectacle-corrected visual acuity (BSCVA) were registered. At the 3-month follow-up visit, the patients completed a questionnaire regarding night vision pre- and postoperatively.
 
 
RESULTS: The mean bilateral, spherical equivalent refraction (SE) was - 8.76 D (range 6.32 to - 12.0 D) preoperatively, and - 1.69 D (range 0 to - 4.38 D) postoperatively. The mean bilateral BSCVA was not changed by the operations. We found a significant correlation between large scotopic pupil sizes and the impression of worsened night vision (p < 0.01). A significant correlation between gender (males) and subjectively reduced night vision postoperatively was also found (p < 0.05).
 
 
CONCLUSION: Large pupil size measured preoperatively is correlated with an increased frequency of subjectively experienced post-LASIK visual disturbances during scotopic conditions. We recommend preoperative evaluation of pupil size in all patients prior to LASIK surgery.