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学会・論文発表 |
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A.D. Semyonov, A.V. Doga, G.F. Kachalina, K. Okuyama,
I.A. Alisov, V.S. Tyurin, V.A. Sugrobov, A.G. Evsyukov
Photoastigmatic Refractive Keratectomy
with the“Profil-500”for Correction
of Compound Myopic Astigmatism
The paper analyses clinical and functional results of
the transepithelial PARK with the excimerlaser device "Profi1−500"
performed in 250 eyes of 131 patients between the ages of 18
and 45 with compound myopic astigmatism to 5.0 D and myopia
to 10.0D.The follow−up was 3years． In 90％ of cases visual acuity
of 0.5−1.0 without correction or with weak myopic correction
not more than −2.0D was achieved by the operation. Complete
correction of astigmatism was obtained in 74％ of cases, residual
astigmatism from -0.5 to -0．75D（physiological) was found in
22.8％ of cases, from -1.0 to -1.5D in only 3.2％ of cases and
only in eyes with initial astigmatism of 4.0−5.0 D. The refractive
result agreed with the calculated data in 96.1％ of cases．
The method of excimerlaser correction of compound myopic astigmatism，i.e.，Photo
astigmatic refractive keratectomy（PARK），acquires the growing
popularity among eye surgeons in Russia and worldwide．
However most specialists dealing with this problem and using
different excimer laser devices agree that the most accurate
and predicted result is achieved in spherical rather than in
cylindric refraction component. From literature, PARK decreases
spherical refraction component by 75-95%, on average, and cylindric
one by 47-81%. After operation, the best visual functions are
recorded, as a rule, in correction of astigmatism to 2.0 D with
myopia to 6.0 D [2-9].
It's should be stressed that from 1986 workers of the Center
of Laser Surgery at the Svyatoslav Fyodorov SI IRTC "Eye microsurgery"
have pioneer inventions of several generations of ophthalmic
laser devices "Profil".
In 1995 the forming optical system of "Profil-400" which worked
on the basis of absorptive gas cell was modified. "Profil-500"
contains basically new laser system* which was created in cooperation
with the Center of Physics lnstrument-making at the Institute
of General Physics of Russian Academy of Sciences headed by
the Nobel Prize winner A.M. Prokhorov. This device allows simultaneous
correction of not only myopia of any value [1] but correction
of compound myopic astigmatism due to formation of ellipsoid
profile of laser ray distribution with the set spatial configuration
and selective reprofiling of the corneal surface.
The objective of the study is the analysis of clinical and functional
results of PARK in correction of compound myopic astigmatism
with the "Profil-500" with the follow-up of 3 years.
* Patent of RF, 24.06.98
Material and methods
Preoperatively, we examined 250 eyes of 131 patients between
the ages of 18 and 45 with compound myopic astigmatism to 5.0
D and myopia to 10.0 D. The first group comprised 54(21.6%)
eyes with initial astigmatism to -1.5 D, the second 135 (54.1%)
eyes with astigmatism from -1.75 to -3.0 D (Fig. 1), the third
61(24.3%) eyes with astigmatism from -3.25 D to -5.0 D.
Direct astigmatism was foundiin 185(74%) eyes and reverse one
in 65(26%) eyes. Spherical refraction component to 3.0 D was
recorded in 31(12.4%) eyes, from 3.25 to6.0 D in 137(54.8%),
and from 6.25 to 10.0 D in 82(32.8%) eyes.
Visual acuity without correction exceeded 0.05 in none of the
cases. Visual acuity with maximal glass correction was 0.1-0.2
in 7 (2.8%) eyes, 0.3-0.4 in 33(13.2%) eyes, 0.5-0.7 in 139
(55.6%), and 0.8-1.0 in 71 (28.4%) eyes. Thus, corrected visual
acuity of 0.5-1.0 was recorded in 210 (84%) eyes preoperatively.
The similar retinal visual acuity was. in 235 (94%) eyes.
In all cases PARK was performed by transepithelial method, i.e.,
with subsequent evapora tion
of epithelium, Bowman's membrane, and superficial layers of
the corneal stroma. Refraction effect was calculated using software
elaborated at the Center of Laser Surgery of the SI IRTC "Eye
microsurgery" in Windows system.
The operation lasted not more than 1.5 min without any intraoperative
complications.
Results and discussion
Complete correction of astigmatism by 6-l2 months and more after
PARK was recorded in 48 (89.2%) eyes from the 1st group, in
98 (72.6%) from the 2nd group, and in 39 (63.9%) eyes from the
3rd group.
Residual astigmatism in groups at the same time postoperatively
was the following: in the 1st group astigmatism to -0.5 D was
found in 6(10.8%) eyes; in the 2nd group astigmatism to -0.5
D was recorded in 22 (16.3%) eyes (Fig. 2), -0.75 D in 15 (11.1%)
eyes, in the 3rd group astigmatism to -0.5 D was found in 6
(9.8%) eyes, -0.75 D in 8 (13.2%), -1.0 D in 5 (8.2%) and -1.5
D in 3 (4.9%) eyes. Data are presented in Table 1.
Thus, from the total number of eyes operated on, by 6-12 months
after PARK full correction of astigmatism was diagnosed in 185
(74%) eyes, residual astigmatism -0.5 and -0.75 D, regarded
as physiological, in 57 (22.8%) eyes, from -1.0 to -1.5D in
only 8 (3.2%) eyes from the third group with the high initial
astigmatism. In none of the cases astigmatism exceeded -1.5
D.
In 65 eyes with residual astigmatism from -0.5 to -1.5 D, its
axis remained stable in 35 (14%) eyes and changed within 5-10ﾟ
in 30 (12%) eyes. In none of the cases deviation of the residual
astigmatism axis exceeded 10ﾟ.
From the total number of eyes operated on complete correction
of the spherical component of refraction was achieved in 124
(49.6%) eyes, residual sphere -0.5 D in 87 (34.8%) eyes, sphere
from -0.6 to 2.0 D in 39 (15.6%) eyes. Notably, weak myopic
refraction found 6 months - 3 years postoperatively coincided
with the calculated, i.e., planned, one in 96.1% of cases. Such
"planned undercorrection" was related to the age of patients,
their social demands and refraction of the fellow eyes. In none
of the cases undercorrection was more than -2.0 D (Table2).
Hypercorrection up to +0.25 D from emmetropia, which did not
affect postoperative visual acuity, was found in only 3 eyes
6-l2 months after PARK and only using refractometry in conditions
of cycloplegia (1.2% of cases). It's should be noted that 1.5-2
years postoperatively, hypercorrection was not already found
in these eyes.
By 6-l2 months postoperatively and during the whole follow-up,
visual acuity 0.5-I.0 without correction or with weak myopic
predicted correction was achieved in 94.4% of cases in the 1st
group, in 94% in the 2nd, and in 77% of cases in the 3rd group.
On the whole, there are 225 (90%) eyes as compared to 210 (84%)
eyes with the same visual acuity in glasses preoperatively (Table
3). The
correspondence of this visual acuity to the analogous retinal
one was recorded in 95.7% of cases. It is because of the fact
that postoperatively, we found increase of visual actlity in
30 eyes by 0.1-0.2 as compared to the analogous visual acuity
with glass correction preoperatively.
Dynamics study showed that the corneal refraction, according
to the data of ophthalmometry, by 6-12 months postoperatively
and during the whole follow-up to 3 yearswas 37.59 ± 0.72 D,
on average. Thickness of the corneain the centerwas not less
than 300 um in any case that showed correct choice of individual
ablation
reglmen.
Clinical and functional results of the study are confirmed by
the data of keratotopographical examinations indicating the
following things: achievement of the smooth ablation profile
of the cornea with the maximal refractive effect in the central
zone and gradual change of the corneal refraction in the each
point of the cornea along the entire zone of the excimer laser
influence in all cases; symmetrical flattening of the cornea
along the axis which has had the greatest refraction preoperatively;
multifocali-zones with smooth over fall of refraction from 1.0
to 3.0 D without sharp intermediate zones both inside each zone
and between them, along the whole zone of influence; absence
of defects in keratotopographic images such as "crescent", "key-hole",
and "central islets"; rear decentrations of ablation zone with
regard to the center of the pupil and the cornea not greater
than 0.75 mm and 0.18-0.32 mm, on average.
The above data of keratotopography which was performed at different
terms after transepithelial PARK using "Profil-500" explain
the fact that most patient did not complain of negative subjective
feelings as lights, crepe, dazzling, and halos and, besides,
many of them did not use glasses for the work at near distance
[1].
Thus, the results obtained show that the developed technology
of transepithelial PARK using "Profil-500" is safe, highly effective
and predictable refractive excimer laser interference which
allows simultaneous complete correction of myopia and compound
myopic astigmatism of different degree.
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