| 〔Original Paper〕 |
| Effect of cataract or glaucoma surgery on frequency doubling technology perimetry in patients with glaucoma |
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| Dawei Zhang, Naoya Fujimoto and Shuichi Yamamoto |
| （Received July 12, 2005, Accepted September 7, 2005） |
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SUMMARY
We studied the effect of cataract or glaucoma surgery on visual field determined by frequency doubling technology （FDT） in patients with glaucoma before and after surgery. Patients with glaucoma were examined with FDT before and after 31 cataract surgeries or 31 glaucoma surgeries. Mean deviation significantly improved after cataract surgery in 30 eyes （surgical cataract group） or after glaucoma surgery in 31 eyes （surgical glaucoma group） that underwent surgery, but not in eyes that never underwent surgery （control groups）. Intraocular pressure also decreased postoperatively in both surgical groups. Change of mean deviation （index for diffuse visual field loss） significantly correlated with percent reduction of intraocular pressure in the surgical glaucoma group without hypotony, but not in the surgical cataract group. No significant differences were found in pattern standard deviation in either group. Cataract surgery or glaucoma surgery improved visual field loss, as determined by FDT in patients with glaucoma. Glaucoma surgery improved visual field due to intraocular pressure reduction.
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Key Words
| Cataract surgery, glaucoma surgery, FDP, improvement |
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Ⅰ．Introduction
Frequency doubling technology （FDT, Humphrey-Zeiss and Welch Allyn,
Dublin, CA, USA） has been developed to screen for glaucoma［1］. As determined by FDT, cataract can worsen visual field［2-4］. Cataract surgery improves visual field, especially mean deviation on the Humphrey field analyzer （HFA, Humphrey-Zeiss, Dublin, CA, USA）［4-7］. Reduction of intraocular pressure led to improvement as determined with
FDT［8］. We studied visual field evaluated by FDT in patients with glaucoma before
and after cataract surgery or glaucoma surgery to assess the effect of
cataract removal and intraocular pressure on FDT.
Ⅱ．Materials and Methods
Thirty-one consecutive patients （19 men and 12 women） with glaucoma
and cataract had undergone FDT at least once before this study to remove
the learning effect［9,10］. Their ages ranged from 50 to 87 years （mean: 68.6 years）. Twenty-six
had open angle glaucoma and 5 had primary angle closure glaucoma. Those
with angle closure glaucoma had undergone laser iridotomy before the study.
Thirty-one eyes in 31 patients who underwent cataract surgery （surgical
cataract group） and 22 fellow eyes that never underwent cataract surgery
（control cataract group） were included. Four fellow eyes in the surgical
group were excluded because they could not see the fixation point, and
5 eyes underwent cataract surgery during the same period. The 31 eyes in
the surgical group never received pilocarpine at examination, and the size
of the pupil was more than 3 mm at examination. Cataract surgery was performed
by the same surgeon （NF）; it included a phacoemulsification procedure
with a small incision （less than 4 mm） and implantation of a soft intraocular
lens （acrylic lens with a 5.5-mm optic diameter） in the capsular bag.
Thirty-one eyes of 31 patients （20 men and 11 women） who underwent
glaucoma surgery （surgical glaucoma group） and 22 fellow eyes in the
same patients that never underwent glaucoma surgery in the fellow eyes
（control glaucoma group） were included. Four of 31 fellow eyes in the
surgical group were excluded because they could not see the fixation point
and 5 eyes underwent glaucoma surgery during the same period. Patient ages
ranged from 23 to 75 years （mean: 52 years）. None had previously undergone
glaucoma surgery or laser treatment. All had experienced threshold tests
of FDT at least once. All had 0.5 or better visual acuity. One surgeon
（NF） had performed a trabeculectomy with a mitomycin adjunct in all patients.
The 31 eyes in the surgical group never received pilocarpine at examination,
and the size of the pupil was more than 3 mm at examination.
Patients were examined in both eyes with threshold c-20 of FDT under
far correction within 1 month before and within 3 months after surgery.
Intraocular pressure was measured by applanation tonometry after FDT testing.
Mean deviation （MD）, pattern standard deviation （PSD）, and intraocular
pressure at examination were compared before and after surgery with paired
t test. Visual acuity was compared before and after cataract surgery with
paired t test. The correlation between change of MD and percent reduction
of intraocular pressure was analyzed with simple regression analysis. All
results of less than 20% of fixation loss, 33% of false positive, and 33%
of false negative were adopted. If unreliable, FDT was reexamined. The
research followed institutional guidelines and the tenets of the World
Medical Association Declaration of Helsinki. We obtained written informed
consent from each patient before their entry in this study.
Ⅲ．Results
Thirty-one cataract surgeries were performed without complication. Thirty reliable results in the surgical group and 22 reliable results in the control group were included. Only 1 result in the surgical cataract group was excluded because it exceeded false negative results twice. Postoperative MD significantly （P<0.0001） improved after cataract surgery （from －9.8 dB to －6.9 dB, Fig. 1）. Also visual acuity significantly （P<0.0001） improved after cataract
surgery, and intraocular pressure at examination significantly （P=0.0064）
decreased after cataract surgery. The reduction of intraocular pressure
was 1.8 mmHg （from 16.7 mmHg to 14.9 mmHg）. No significant differences
in terms of PSD （P=0.1804） were found in the surgical cataract group
before and after surgery. Only 2 patients showed a deteriorated MD after
cataract surgery. The change of MD was not significantly correlated with
% intraocular pressure reduction （Fig. 2）. |
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| Fig. 1 Mean deviation （MD） improved after cataract surgery in all but two cases in the surgical cataract group. |
Fig. 2 No significant correlation between mean deviation （MD） change
and reduction of intraocular pressure was found in the surgical cataract
group. |
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| Fig. 3 Mean deviation （MD） improved after glaucoma surgery in all but
four cases in the surgical glaucoma group. |
Fig. 4 Slight significant correlation between mean deviation （MD） change and reduction of intraocular pressure was found in the surgical glaucoma group without hypotony. |
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Thirty-one reliable results in the surgical glaucoma group and 22 reliable
results in the control glaucoma group were included. Postoperative MD significantly
（P<0.0001） improved after cataract surgery （from －11.9 dB to －10.6
dB, Fig. 3）. Also intraocular pressure at examination significantly （P<0.0001） decreased after glaucoma surgery. The reduction was 14.4 mmHg （from 27.9 mmHg to 13.5 mmHg）. No significant differences in terms of PSD （P=0.9558） were found in the surgical group before and after surgery. Four patients showed a deteriorated MD after trabeculectomy. Two of those 4 patients showed low intraocular pressure （3 and 7 mmHg） after filtering surgery. The change of MD was not significantly （P=0.4536） correlated with percent intraocular pressure reduction in 31 patients. When 5 eyes with an intraocular pressure of 8 or less mmHg were excluded, the change of MD was significantly （P=0.0489） correlated with percent reduction of intraocular pressure （Fig. 4）.
No significant differences in terms of MD （P=0.9810）, intraocular pressure
at examination （P=0.3155）, or PSD （P=0.2146） were found in the control
glaucoma group before and after glaucoma surgery.
Ⅳ．Discussion
MD determined with FDT significantly improved after cataract or glaucoma
surgery. This improvement was only found in the surgical groups, while
no change of MD was found in the control groups. Learning effect could
be dismissed in the control groups. FDT threshold was determined, based
on contrast sensitivity and cataract-induced deterioration of contrast
sensitivity［11,12］. Cataract then would deteriorate MD with FDT in patients with cataract
without glaucoma, which meant diffuse loss［3,4］. Kogure et al［2］reported
that the FDT showed a significant decrease in sensitivity with decreasing
retinal illumination, which was induced by neutral density filter or miosis.
Retinal illumination should, therefore, be taken into account when evaluating
FDT results. Glaucoma surgery also improved MD. A possible mechanism might
be reversible change with FDT. We reported 1 case with MD change in response
to intraocular pressure［8］. The reduction of intraocular pressure led
to an improvement of MD. The change of MD correlated with the reduction
of intraocular pressure in the present patients without hypotony after
glaucoma surgery. The patients with hypotony after glaucoma surgery showed
deteriorated MD. Hypotony retinopathy or cataract progression could deteriorate
visual field.
We did not compare the results of HFA with those of FDT in this study.
Similar results would have been obtained from HFA, according to previous
reports［5-7］.
In conclusion, visual field determined by FDT in patients with glaucoma
and cataract improved after cataract surgery or glaucoma surgery. |
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Acknowledgment
| We are grateful to Maxine A Gere for her editorial assistance. |
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要旨
| Frequency doubling technology（FDT）は緑内障スクリーナーとして開発され，緑内障の視野異常を短時間高感度に検出しうる新しい視野計である。今回は白内障手術また緑内障手術の前後でFDTを測定し，それらの手術の影響を検討した。対象は千葉大学病院で通院する緑内障患者62名，そのうちには緑内障手術群31名と白内障手術群30名であり，その反対眼で同時に手術しなかった対照群でわけた。緑内障患者のFDTにおいて白内障手術または緑内障手術後に視野全体が均一に障害されることの指標であるmean
deviation（MD）が改善した。緑内障手術前後の眼圧下降とMDの改善は有意な相関がみられ，眼圧下降によって視野全体が改善することがわかった。しかし，白内障手術前後では眼圧下降とMDは有意な相関がみられなかった。白内障術後の視野改善は視野全体の変化が白内障という混濁の影響を受け，術後混濁の減少によりに網膜へ到達する輝度が増加するとためと考えられた。緑内障術後の視野改善は眼圧下降によるものだと考えられた。 |
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Others
Department of Ophthalmology and Visual Science, Chiba University Graduate School of Medicine, Chiba University, Chiba 260-8670.
張 大威，藤本尚也，山本修一: 緑内障におけるfrequency doubling perimetry への緑内障，白内障手術の影響．
千葉大学大学院医学研究院視覚病態学
TEL. 043-222-7171. FAX. 043-224-4162. e-mail: fujimoto@faculty.chiba-u.jp
2005年7月12日受付，2005年9月7日受理. |
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