PMID- 8753983
OWN - NLM
STAT- MEDLINE
DCOM- 19960917
LR  - 20081121
IS  - 0941-293X (Print)
IS  - 0941-293X (Linking)
VI  - 93
IP  - 3
DP  - 1996 Jun
TI  - [Decrease of retinal image contrast after photorefractive keratectomy, 
      improvement within the scope of surface restitution].
PG  - 232-6
AB  - Photorefractive keratectomy (PRK) with the ArF excimer lasers in current use 
      usually approximates the intended corneal curvature by a mean of a delicate 
      step-type pattern that is smooth off afterwards by reepithelialization and tear 
      film. The present study was based on a model eye with axial myopia of -6 D but 
      otherwise the optical and geometric properties of the Gullstrand model eye and 
      was designed to investigate to what extent. (1) corneal step patterns can reduce 
      retinal image contrast and (2) smoothing effects can restore such a loss. 
      METHODS. The corneal surface resulting from PRK in the case of a myopia of -6 D 
      (optical zone diameter 6 mm) is calculated for the parameters of the model eye. 
      The retinal image contrasts of bar patterns are calculated by PSF (point spread 
      function) analysis: varying size of pupil, wavelength, bar width, ablation step 
      height and degree of smoothing. RESULTS. Step height influences retinal image 
      contrast crucially. With step heights above 0.4 micron a massive loss of retinal 
      image contrast must be expected, which can, however, be corrected to a useful 
      extent by surface-smoothing effects. CONCLUSION. This study indicates that PRK 
      with excimer lasers should be performed with low fluence and correspondingly low 
      corneal step heights.
FAU - Ludwig, K
AU  - Ludwig K
AD  - Augenklinik der Universitat Munchen.
FAU - Schaffer, P
AU  - Schaffer P
FAU - Gross, H
AU  - Gross H
FAU - Lasser, T
AU  - Lasser T
FAU - Kampik, A
AU  - Kampik A
LA  - ger
PT  - English Abstract
PT  - Journal Article
TT  - Abnahme des retinalen Bildkontrasts nach photorefraktiver Keratektomie, Besserung 
      im Rahmen der Oberflachenrestitution.
PL  - Germany
TA  - Ophthalmologe
JT  - Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
JID - 9206148
SB  - IM
MH  - Computer Simulation
MH  - Contrast Sensitivity/*physiology
MH  - Cornea/physiopathology/surgery
MH  - Fourier Analysis
MH  - Humans
MH  - Lasers, Excimer
MH  - Models, Anatomic
MH  - Myopia/physiopathology/*surgery
MH  - *Photorefractive Keratectomy
MH  - Postoperative Complications/*physiopathology
MH  - Retina/*physiopathology
EDAT- 1996/06/01 00:00
MHDA- 1996/06/01 00:01
CRDT- 1996/06/01 00:00
PHST- 1996/06/01 00:00 [pubmed]
PHST- 1996/06/01 00:01 [medline]
PHST- 1996/06/01 00:00 [entrez]
PST - ppublish
SO  - Ophthalmologe. 1996 Jun;93(3):232-6.