ICO第26回シンガポール国際眼科学会 RK後7年の角膜内皮細胞:お知らせ

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1990年3月18日

ICO第26回シンガポール国際眼科学会 RK後7年の角膜内皮細胞

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RK後7年の角膜内皮細胞ICO第26回シンガポール国際眼科学会 シンガポール RK後7年の角膜内皮細胞

ENDOTHELIAL CELL IN ARK PRACTICE
UP TO 7 YEARS
DIRECTOR M.D.
KODO OKUYAMA
SANGUBASHI EYE CLINIC GOTANDA
Institute of Refractive Keratoplasty

Summary: In l983 I Iecived Anterior Radial Keratotomy to both eyes at the moscow Research Institute of Eye Mierosurgery from Professor S.N. Fyodorov. 1)

I want to report on the excellent results achieved over the past 7 years using ARK on patients in Japan. Also I would like to show the complete safty of this procedure. Using a speculer microscope and putting the data through corneal endothelial cell computer norphologic analyzer.
I will present the histories of 17 eyes in 9 patients. One eye was uemotropic and didn’t need correction. These 9 patients were all members of my family or my friend’s families. All these patients gave informed consent.

method : ARK was performed on l7 eyes of 9 patients. The ages of all the subjects at the time of completion of this study are over 25 years old (average 32.5 years) and all of them had more then -2.50 diopters myopia.
Three out of the nine wore contact lenses regulary. (2RL,5RL and 9RL)
All cases except 3R had no previous history of disease. Case 3R had keratitis, while wearing a hard contact lense at the age of 22. All of the patients had naked vision less than 0.3 and a corrected visual acuity of more than1.0. Before ARK a video and written matter were used to explain the procedure to the patients. All patients are given corneometry as well as the standard examinations. The standard procedure developed by Prof. Fyodorov4) usd for ARK seven years ago and photographs were obtained of corneal endothelial cells using a Konan specular microscope and a morphometric cell analyzer, used to obtain cell counted the degree of polimegethism and pleomrphism. Case 2R,5RL and 9R were reoperatet and one case 9L was reoperated twice with the purpose of increasing the effect.
The magnification is calibrated with a micrometer scale. Thirty cells are outlined. The cells are digitized by touching the cell apices with a graphic tablet pen. These coordinates are entered on to a digitizer table and analyzed by computer for cell density, standard deviation (SD), coefficient variation (CV), average of cell area (AVE), maximum of cell area (MAX), minimum of cell area (MIN), and a histogram is made. .
Cell density is calculated by dividing one milion by the mean cell area.
CV is calculated by dividing the SD of cell area by the mean cell area.
Polimegethism is assessed indipendently of cell size using a dimentionlless index for CV. ‘Normal endothelial cells are about 300 microns square in size and hexagonal. Inflamation or injury can reduce cell count, hexagonality and uniformity of size. Eyes with exessive deviation in any of the above are not considered as candidates for ARK.

Result: Visual acuity in all eyes having had ARK had stabilized after four months. (Fig.2,3 and4) Tables 3 and 4show change in corneal refraction and visual acuity before and 7 years after. According to the size of the optical zone and the number of cuts, the resulting corneal refractive power can be decreased from 1 to 8 diopters. Out of 17 cases, one case (6L) of superficial keratotitis occured. It was treated with a two week course of gentamycin subconjunctive injection and a wide-spectrum antibiotic. After 7 years there are no complications and the cornea remains transparent. (Fig. 5)
Specular microscopic analysis shows mean cell densities of 2,347 cells per square mm between the incisions, standard deviation 122, coefficient variation 3l, average of cell area 426, maxmum of cell area 658, minimum of cell area l73 microns square. (Fig.6)
Slight increases in nonhexagonal cell (pleomorphism), and a variation in cell size (polimorphism) are observed. Case 3R had a history of keratitis.(Fig.7)
Specular microscopic analysis shows mean cell densities of 1,869 cells per square mm between the incisions, standard deviation 151, coefficient variation 28, average of cell 635, maxmum of cell area 818, minimum of cell area 162 microns square.(Fig.8) As the specular microscope only became available in 1986, preoperative data is not available for l7 cases, including this case. We can keep record of yearly rates of cell loss.
For 121 eyes in 61 patients from l987 to l988 the immediate cell loss a result of operating is 5.9%.

Discussion : Since the first pioneering work done by Professor Fyodorov and others in 1974, over 327,000 people have recived ARK.3) There have been, however, only limited reports of long term effects and sporadic reports on safty and effectiveness of ARK. Because of high satisfaction and lack of complications and the subsequent non-return of patients to the clinic, ther.e is limited statistical information available. There is in the case of Japan a certain resistance in the old establishment to ARK, because of the unfortunate experience with Professor Sato’s posterior radial ke.atotomy (PRK) in 1936. Therefore I make this report.
The result of ARK remains constant between 4 months and 7 years after operating. The changing refraction is limited to 8 diopters. The patient must be informed of this prior to operating. In six cases with previous
mild myopia aged 35 to 40 years, none wore glasses or contact lenses after seven years. (3RL,4RL,5L,6R,7L and 8RL) .
In previously moderate or severe cases of myopia, low grade glasses are worn when driving, at theatre or in some cases constantly, which doesn’t affect the field of vision as those wore previously. So nine cases discontinued use of contact lenses after ARK. Those that required lenses, were first examined at eight to twelve months with a specular microscope as a precautionar.y check.
Sometimes temporary glare and or starburst effect are noted.
Post-operative astigmatism not requiring corrective lenses was noted in cases 3R, 4R and 5RL. In cases 3R and 4R are 0.75 diopters, 5R is 1.00 diopter and in 5L is 1.50 diopters.
I’d like to make one final point about endothelial cell dynamics over the long term after ARE. Bullous keratopathy is not a possible result postoperatie endothelial cell loss of 5.9% , thereafter continuing at a
normal rate coinciding with Dr.Murphy’s 0.35 to 0.71% per year.(Fig.7)
Also cases reoperated showed a similar cell loss. At this rate of endothelial cell loss, a person would have to live to the age of 166 years before the critical level of 500 cells per square mm would be reached.
So specular microscopic examination is done before operation in order to facilitate obtaining informed consent as well as obtaining data to follow up post-operative cell loss and also the yearly rate of cell loss.
In the case of finding unusualy high levels of polymegethisn or polimozphism, these people are rejected for ARK. We find as did Dr.Scott, a higher incidence of such conditions among long term contact lens wearers. (Fig.6)
This could be a result of previous histories of infection.
We mesured endothelial cell loss and plotted the information for 121 eyes in 61 patients on a graph similar to Dr.Myer’s endothelial cell depletion graph.(Fig.2) On his graph a 35 year old person will have 2700 endothelial cells per square mm. If such a person loses 5.9% as an immediate result of ARK and we calculate natural aging cell loss of 0.35 to 0.71% ( according to Dr. Murphy ), then at the age of forty-two he should have 2,457 endothelial cells per square mm. But in practice our forty-two year old patient has 2,816 endothelial cells per square mm in his right eyes and 3,355 cells in his left eye.(Fig.9,10)  In the other seven cases we recorded a similar high result. (Fig.11) One case 3R was lower and should continue to be observed over the long term.
Up till now 1,500 patients have received ARK at our clinic. (Fig.l2)

References :
i) K.Okuyama : myopia is possible to operate within 15 minutes.
Tokyo, Kobunsha p92-150, 1985
2) D.J.Mayer : Clinical wide-field specular microscopy.
Bailliere Tindall, London p52-53, 1984
3) S.N.Fyodorov, A.I.Ivashina : Microsurgery of the eye- Main aspects.
Mir. Publihers. Moscow p68-70, 1987
4) S.N.Fyodorov, V.V.Durnev : Operation of dorsaged dissection of corneal
circular ligament in cases of myopia of mild degree.
Annals of Ophthalmology p1986-1989, l979 Dec.
5) T.Yamaguchi et al. : Bullous keratopathy after anterior-posterior radial
keratotomy for myopia and myopic astigmatism.
Am. J. Opthalmol. 93:600. 1982
6) Scott M Mac Rae et al. : The effects of hard and soft contact lenses
on the corneal endothelium.
Am. J. Ophthalmol. p50-57, July 1986
7) Scott M. Mac Rae et al. : The effect of radial keratotomy on the corneal
endothelium.
Am. J. Ophthalmol. p538-542, October, l985

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