Changes in Focal Macular ERGs after Macular Translocation Surgery with 360° Retinotomy

Abstract

purpose. To evaluate the short- and long-term changes of focal macular electroretinograms (fmERGs) after macular translocation with 360° retinotomy.

methods. This was a retrospective study. fmERGs were recorded in 19 eyes of 19 consecutive patients who underwent macular translocation with 360° retinotomy for choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD; 17 eyes) or polypoidal choroidal vasculopathy (2 eyes). The changes in the fmERGs, recorded before, shortly after (6–12 months; mean 8.3 months), and more than 18 months (18–30 months; mean 22.4 months) after surgery from 12 eyes, were analyzed. A 15° stimulus centered on the fovea was used to elicit the fmERGs.

results. The mean logarithm of minimum angle of resolution (logMAR) was 1.06 ± 0.07 (20/230) before surgery, 0.78 ± 0.08 (20/121) early after surgery (n = 19), and 0.64 ± 0.07 (20/87) late after surgery (n = 12). These improvements in visual acuity were significant (P = 0.0074, P = 0.0050, respectively). Before surgery, the amplitudes of all components of the fmERGs were markedly reduced in all eyes. The mean b-wave amplitude in 17 AMD eyes recorded early after surgery was significantly larger (P = 0.0262), and the mean a-wave amplitude was also increased but not significantly (P = 0.1180). The mean amplitudes of the a- and b-waves in 10 AMD eyes recorded after 18 months were significantly larger than those before the surgery (P = 0.0218, and P = 0.0284). The mean implicit time of the b-wave in 17 AMD eyes decreased early after surgery, and a further decrease was detected at the later testing time.

conclusions. These results indicate that macular function is partially recoverable after macular translocation in some patients.

Age-related macular degeneration (AMD) is the leading cause of legal blindness among the elderly in industrialized countries. ¹ There are two types of AMD: the dry type and the exudative or wet type with subretinal choroidal neovascularization (CNV). In AMD, both eyes are usually affected with very depressed visual acuities. Laser photocoagulation ² or surgical removal of the subfoveal CNV ^{3 4} has been used to treat these eyes, but both procedures damage the underlying retinal pigment epithelium (RPE) and choriocapillaris, which can lead to further loss of reading ability after the atrophy of the RPE. Photodynamic therapy is another newer method to treat AMD; however, the effectiveness of this procedure on visual acuity has been demonstrated in only a limited number of cases. ^{5 6}  

Macular translocation surgery is a surgical procedure that moves the fovea from the underlying diseased RPE to healthier RPE. ^{7 8 9} Currently, this is the only treatment that may offer improvements in visual acuity, and several case series involving macular translocation have been published. ^{10 11 12 13 14 15 16} Two techniques of macular translocation are performed at present, and both techniques involve the creation of a retinal detachment. One technique involves the detachment of the entire retina from the RPE by a subretinal infusion of fluid with a 360° circumferential retinotomy followed by the rotation of the macula. ^{10 11 12 13 14} The other technique includes the creation of a partial retinal detachment followed by the rotation of the retina by head positioning (limited type). ^{15 16}  

We have reported that macular translocation with 360° retinotomy improves visual acuity but reduces the cone and rod components of the full-field ERGs at a relatively early postoperative time. ¹⁷ To date, there has been no objective determination of the changes in macular retinal function after macular translocation, except for one case report with limited macular translocation that showed an improvement of foveal cone ERGs. ¹⁸ Foveal function has also been assessed subjectively (e.g., by microscotometry on myopic patients ¹⁹ and measurements of reading speed on patients with AMD) ¹⁴ in addition to the visual acuity after macular translocation surgery. 

The question arises whether the newly located retina–RPE complex functions as well as the original macula—that is, are the neural components preserved or reorganized, and do they recover function after the acute retinal detachment and relocation to the new site? Another question we asked was whether the recovered function is long lasting. 

To answer these questions, we recorded focal macular electroretinograms (fmERGs) before, early, and late after macular translocation surgery with 360° retinotomy. A 15° stimulus was used to elicit the fmERGs, because this size stimulus would provide information of the function over a larger area of the macula than that obtained by central visual acuity. The stimulus was also designed so that the contributions of the on- and off-bipolar cells could be evaluated. 

Patients and Methods

Patients

Macular translocation surgery was performed on one eye of 17 patients for AMD with subfoveal CNVs (ages, 62–87 years) and on one eye of 2 patients with polypoidal choroidal vasculopathy (PCV; ages, 77 and 64 years) at the Nagoya University Hospital from March 2000 to September 2001. All 17 cases of CNV associated with AMD were new or recurrent and were classified into predominantly the classic that involved the geometric center of the foveal avascular zone. 

The best corrected visual acuity (BCVA) was measured with a standard Japanese visual acuity chart on the day of the preoperative fmERG examination and then was converted to Snellen visual acuity. The preoperative BCVA ranged from 20/800 to 20/100, and the diameter of the CNVs ranged from 0.8 to 2.6 disc diameters (1.4 ± 0.6; mean ± SD). 

Before the macular translocation surgery, one patient with AMD had been treated by the surgical removal of the CNV followed by a photocoagulation of a recurrent CNV. Two other patients with AMD and one with PCV had been treated with radiation therapy of 20 gy for 10 days, and another with AMD had been treated with photocoagulation. 

The follow-up period after treatment ranged from 13 to 38 months (mean, 24.4 ± 5.0). The follow-up period after successful silicone oil removal ranged from 7 to 31 months (mean, 20.2 ± 6.6). 

This research was conducted in accordance with the institutional guidelines of Nagoya University and conformed to the tenets of the World Medical Association Declaration of Helsinki. Informed consent was obtained from each patient for the surgery and for the pre- and postoperative ERGs, after they were provided information on other treatment options including photocoagulation, removal only, and observation alone. 

Surgical Methods

Our technique was a modification of the 360° retinotomy method of Machemer and Steinhorst. ^{7 8} Initially, a lensectomy with preservation of the anterior lens capsule was performed followed by the complete removal of the vitreous by pars plana vitrectomy with infusion of Ca²⁺- and Mg²⁺-free balanced salt solutions (BSS; Alcon Pharmaceuticals, Fort Worth, TX) for 10 minutes (cases 1–6) or with supplemented balanced salt solutions (cases 7–19; BSS-plus, Alcon Pharmaceuticals). Four separate dome-shaped retinal detachments were then created by subretinal infusion of the saline solution. Fluid–air exchange was then performed, which led to the coalescence of the detachments followed by a 360° retinotomy at the ora serrata with automated scissors. This was followed by the injection of heavy perfluorocarbon liquid and the rotation of the whole retina around the axis of the optic disc with further injection of perfluorocarbon liquid during the rotation. The site of the 360° retinotomy and the holes artificially created to detach the retina were sealed by endophotocoagulation. After this procedure, an exchange of perfluorocarbon liquid by silicone oil (1000 centistoke) was performed. The operation time ranged from 134 to 280 minutes (mean, 202 ± 35). 

After 2 to 3 months, the silicone oil was removed, and an intraocular lens was implanted in patients who requested the implantation. 

Focal Macular ERGs

fmERGs were recorded before and 6 to 12 months (mean, 8.3 ± 2.7) after the macular translocation surgery in 19 eyes. fmERGs were recorded again at 18 to 30 months (mean, 22.4 ± 4.0) after the surgery in 12 eyes that were followed for more than 18 months. The system and the techniques for recording fmERGs under direct fundus observation have been described in detail. ^{20 21} Briefly, an infrared fundus camera, equipped with a stimulus light, background illumination, and fixation target, was used. The image from the camera was fed to a monitor, and the examiner used the monitor to maintain the stimulus on the macula. The size of the stimulus spot was adjustable, and we selected a 15° spot stimulus centered on the fovea. In the recordings after surgery, the stimulus was set on the new fovea-RPE complex at approximately the same retinal location as before surgery. The background light was delivered to the eye from the fundus camera at a visual angle of 45°. Additional background illumination outside the central 45° produced a homogeneous background illumination for nearly the entire visual field. 

A Burian Allen bipolar contact lens electrode was used for the ERG recordings and allowed not only an extremely low noise level but also provided a clear view of the fundus displayed on the monitor. The intensities of the white stimulus light and background light were 29.46 and 2.89 cd/m², respectively. 

After the patients’ pupils were fully dilated with 0.5% tropicamide and 0.5% phenylephrine hydrochloride, fmERGs were recorded by stimulating the macula with 5-Hz rectangular stimuli (100 ms light-on and 100 ms light-off). A total of 512 responses were averaged by a signal processor. A time constant of 0.03 seconds with a 100-Hz high-cut filter on the amplifier was used to record the a- and b-waves, and the time constant was reduced to 0.003 seconds for recording the oscillatory potentials (OPs). 

The amplitude of the a-wave was measured from the baseline to the peak of the a-wave. The amplitude of the b-wave was measured from the trough of the a-wave to the peak of the b-wave. The amplitude of each OP wavelet was measured from a baseline drawn, as a first-order approximation, between the troughs of successive wavelets to its peak. 

Results

Surgical Results and Complications

Macular translocation was successfully performed in all patients. The angle of rotation of the retina ranged from 22° to 45° (34 ± 8°). None of the patients had serious postoperative complications such as retinal detachment or proliferative vitreoretinopathy. However, one eye had small particles of perfluorocarbon liquid subretinally in the juxtafoveal area, and another eye had a subretinal bubble of perfluorocarbon liquid near the ora serrata. One eye had an unintentional translocation of retinal pigment epithelium in the inferior quadrant near the equator during the creation of the retinal detachment. A postoperative, temporary increase in the intraocular pressure that lasted for 2 or 3 days was detected in five eyes, and the pressure was controlled with 500 mg oral acetazolamide. Secondary cataract developed in one eye. CNV recurred at the previously affected fovea in one patient with AMD. This and a regrowth of the residual vascular network in a patient with PCV were treated by laser photocoagulation. Eleven of 17 AMD eyes and 1 of the 2 PCV eyes had different grades of fluorescein staining at the macula similar to cystoid macular edema with normal macular configuration by optical coherence tomography (Table 1) . 

Visual Acuity

The preoperative (abscissa) and the postoperative (ordinate) visual acuities at the final follow-up are plotted in Figure 1A . The postoperative BCVA ranged from 20/220 to 20/33 in the 17 eyes with AMD (filled circles) and was 20/29 and 20/667 in the 2 eyes with PCV (filled squares). The mean logarithm of minimum angle of resolution (logMAR) in the patients with AMD was 1.01 ± 0.06 (20/205) before surgery (n = 17) and 0.78 ± 0.07 (20/121) at the early and 0.63 ± 0.05 (20/85) at the late measurement times (n = 10; Table 2 ). At the final follow-up examination, visual acuity was 0.63 ± 0.04 (20/85; n = 17). The improvements in visual acuity at the three postoperative times were significant (P = 0.0186, P = 0.0116, P = 0.0008, respectively; Wilcoxon signed rank test; Fig. 1B ). 

The mean logMAR in the patients with AMD before surgery did not correlate with the visual acuity at the early measurement (r = 0.212, P = 0.4198; n = 17), at the late measurement (r = 0.044, P = 0.8687, n = 10), or at the final follow-up (r = −0.025, P = 0.9468, n = 17). 

Focal Macular ERGs

The waveforms of representative fmERGs recorded from eight eyes before surgery and early (6–12 months) and late (18–30 months) after surgery are shown in Figure 2 . Overall, the preoperative amplitudes of the a- and b-waves were markedly reduced, and the OPs were also noticeably reduced or nearly nonrecordable in all eyes. The implicit times of the a-waves in 15 eyes and b-waves in 19 eyes were all delayed. 

An increase in the a-wave in cases 2, 10, and 14, and in the b-wave in cases 2, 3, 7, and 11 can be seen in the early postoperative recordings. There was a marked increase in the a- and b-waves in cases 1, 7, 10, 11, and 14 at the late postoperative recordings. The amplitudes of the a- and b-waves before surgery and early after surgery are shown in Figure 3 (filled circles for the 17 eyes with AMD; filled squares for the 2 eyes with PCV. Early after surgery, 12 of 17 eyes with AMD had preserved or increased a-wave amplitude, and 2 eyes with PCV had unchanged or slightly increased a-wave amplitude. The b-wave amplitude was preserved or increased in 15 of 17 eyes with AMD, and unchanged or slightly increased in 2 eyes with PCV. 

The amplitudes of the a- and b-waves at the later recording times in 12 eyes are shown by open diamonds. The amplitudes of the a-waves in 6 of 10 eyes with AMD in the 2 eyes with PCV recorded at the later time increased and that of the b-wave in 7 of 10 eyes with AMD and in 1 eye with PCV also increased compared with those recorded in the early postoperative period (Fig. 3) . The a-wave amplitude was decreased in one eye with AMD, and the b-wave was decreased in two eyes with AMD and one eye with PCV compared with those recorded in the early postoperative period. 

The mean amplitudes and implicit times of the a- and b-waves in patients with AMD before surgery and at a mean of 8.6 (early) and 23.0 (late) months after surgery are shown in Table 2 , along with the data from 112 normal subjects (ages, 20–79 years, mean 47) recorded with the same equipment under the same conditions. ²² The mean amplitude of the a-wave in patients with AMD was 0.44 ± 0.08 μV (mean ± SE) before surgery, 0.57 ± 0.06 μV early after surgery (17 eyes), and 0.82 ± 0.16 μV late after surgery (10 eyes). The increase in the a-wave amplitude early after surgery was not significant (P = 0.1180); however, that at the later time was significant (P = 0.0218, Wilcoxon signed rank test; Fig. 4A ). 

The mean amplitude of the b-wave in patients with AMD was 1.17 ± 0.16 μV (mean ± SE) before surgery, 1.34 ± 0.14 μV early after surgery (17 eyes), and 1.80 ± 0.30 μV late after surgery (10 eyes). The increase in the mean b-wave amplitude at the early and late recording times were both significant (P = 0.0262, P = 0.0284, respectively; Wilcoxon signed rank test; Fig. 4B ). 

The mean amplitude of the preoperative a-wave with AMD correlated with that recorded early after surgery (r = 0.507, P = 0.0336, n = 17). The preoperative b-wave amplitude correlated with the b-wave recorded early after surgery (r = 0.654, P = 0.0034, n = 17). The mean amplitude of the preoperative a-wave in AMD did not correlated significantly with the a-wave recorded at the later recording time (r = 0.622, P = 0.0538, n = 10). However, the preoperative b-wave amplitude correlated significantly with that at the later recording time (r = 0.693, P = 0.0240, n = 10). 

The correlations between the preoperative a-wave amplitude and the postoperative visual acuity (logMAR) early after surgery (n = 17), at the late follow-up (n = 10), and at the final follow-up (n = 17) were not significant (r = 0.380, P = 0.1342; r = 0.275, P = 0.4511; and r = 0.445, P = 0.0733; respectively). 

The preoperative b-wave amplitude correlated significantly with the postoperative visual acuity (logMAR) early after surgery (r = 0.607, P = 0.0085, n = 17), but not at the later time (r = 0.223, P = 0.5493, n = 10). The preoperative amplitude correlated significantly with the postoperative visual acuity (logMAR) at the final follow-up examination (r = 0.672, P = 0.0023; n = 17). 

Eleven of 17 eyes with AMD with larger preoperative b-wave amplitude (>0.75 μV) had a final visual acuity of 20/100 or better. In the other six eyes with AMD with smaller preoperative b-wave amplitude (<0.75 μV), four eyes had a final visual acuity of 20/100 or better, and two eyes had a final visual acuity worse than 20/100. The probability of obtaining a visual acuity of 20/100 or better in eyes with larger preoperative b-wave amplitude (>0.75 μV) was statistically significant (P = 0.0415, χ² test). For eyes with a b-wave amplitude larger than 1.5 μV, the probability of obtaining a visual acuity of 20/67 or better was also statistically significant (P = 0.0358, χ² test). There were five eyes with a b-wave amplitude greater than 1.5 μV, and four of them had visual acuity of 20/67 or better. Conversely, 9 of 12 eyes with a b-wave amplitude lower than 1.5 μV had visual acuity of 20/100 or worse. However, the two eyes with the smallest preoperative b-wave amplitude of 0.45 and 0.5 μV had a final visual acuity of 20/100 and 20/33, respectively. 

The preoperative, early, and late postoperative mean b- to a-wave ratios were 2.54 ± 0.23 (14 eyes), 2.63 ± 0.34 (14 eyes), and 2.45 ± 0.28 (10 eyes; mean ± SE), respectively. The differences in the b- to a-wave ratios were not significant. The amplitudes of the OPs were not analyzed because very few eyes had recordable OPs. 

The implicit time of the a-waves was measurable in 15 of 19 eyes before surgery, 18 of 19 eyes early after surgery, and 12 of 12 eyes late after surgery. The differences in the mean implicit times in patients with AMD were not significant in these three groups (Table 2) . The mean implicit time of the b-wave in patients with AMD was measurable in all 17 eyes, and the mean was 55.9 ± 1.2 ms before surgery, 53.5 ± 1.1 ms early after surgery, and 51.9 ± 1.9 ms late after surgery (10 eyes). The implicit time of the b-wave early and late after surgery decreased; however, these differences were not statistically significant (P = 0.1208, P = 0.0924, respectively, Wilcoxon signed rank test). 

Discussion

These results and those from our previous study demonstrated that the preoperative macular function was severely impaired—for example, the fmERG amplitudes were reduced and the implicit times were delayed for all components of the fmERGs in cases of exudative AMD. Early after macular translocation, the amplitude of the b-wave increased and the implicit time decreased, followed by a further increase in amplitude and decrease of implicit time at more than 18 months after surgery. 

The amplitude of the a-wave also increased early after surgery, and the increase became significant in the recordings obtained more than 18 months after surgery. The preoperative a- and b-wave amplitudes of the fmERGs correlated with the postoperative amplitude. In addition, the preoperative b-wave amplitude correlated significantly with the postoperative visual acuity, in both the early and the final follow-up recordings, whereas the preoperative visual acuity did not correlate with the postoperative visual acuity at any examination time. Therefore, fmERGs can provide valuable information as a preoperative assessment for eyes with CNV secondary to AMD. Eyes with better preoperative macular function will have better postoperative macular function and visual acuity. However, 2 eyes with the smallest b-wave amplitude obtained good visual acuities of 20/33 and 20/100 after surgery. Thus, the irreversible level of fmERGs cannot be addressed with the data from this study. 

We have reported fundamental changes in macular function after the removal of CNVs by examining the fmERGs elicited by a 15° stimulus and also in macular thickness by optical coherence tomography. We concluded that the recovery of b-wave amplitude was partially due to the decreased retinal thickness after vitrectomy with the removal of CNV after only a 5-month follow-up period. ²⁴ This faster recovery of the b-wave unaccompanied by an increase in the a-wave resulted in a significant increase in the b- to a-wave ratio. The late changes were not investigated, but if the retina was compatible with the relatively healthy RPE, the photoreceptor function should recover partially, resulting in increased a- and b-wave amplitudes. This may have led to the normalized b- to a-wave ratio. 

In this study, the b- to a-wave ratio did not change significantly at the three recording times; however, only the b-wave increased significantly from the early testing times. The selective recovery of the b-wave suggests that the function of the middle layer of the retina relating to the on-bipolar cells recovers earlier, probably as a result of decreased retinal thickness. ²⁴ A significant recovery of the a-wave was delayed, possibly because it required a longer time for the off-bipolar cells and/or photoreceptors to recover. 

There has been no direct demonstration that the retina, which is translocated away from the macular RPE and choroid, functions as it did on the original foveal choroidal vascular supply, especially after the artificial separation of the retina and RPE during the translocation. The relative morphologic intactness of the foveal area very shortly after experimental retinal detachment has been reported recently. ²⁵ In that study, the morphologic changes in the photoreceptors, protein expression, cell death, and proliferation were investigated, and the reattachment resulted in the halting of the many cellular changes induced by the detachment. However, the outer segments (OS) of the photoreceptors remained shorter, and various other morphologic changes in the photoreceptor OS–RPE interface remained altered. The histologic changes induced by creating the retinal detachment from the scleral side in the animal model of macular translocation has also demonstrated the relative intactness of the retinal structure. ^{8 26} However, the integrity of photoreceptor synaptic circuitry with the middle retinal layer and their functional effect has yet to be determined. 

In addition to the possible adverse effect of the artificial retinal detachment, another factor that probably impairs macular retinal function is the long-standing effect of CNV with or without a serous retinal detachment before the surgery. Histologic studies of eyes with AMD have demonstrated severe loss of photoreceptors. ²⁷ Compared with our surgically removed cases, ²⁴ the sizes of CNV for macular translocation were larger which means that the subretinal pathologic changes had been present for a longer time. Thus, the recovery may take longer and may be incomplete. 

The effects of the different RPE and choroidal circulation at the new location of the macula were not determined. However, our results suggest a relatively well-functioning retina, although its recovery required some time. 

We monitored the location of the stimulus on the fundus during the 2 minutes of recordings through the infrared television fundus camera and tracked the macula manually to stimulate the same locus. ^{20 21} This was essential because some of the patients had eccentric fixation or changed their fixation point after macular translocation. The large artifacts that are caused by eye movements were rejected during the summation of the responses by our recording system. By using these techniques, we were able to obtain focal macular ERG with relatively high degree of precision. However, because there is no accurate tracking system, the exact location could not be stimulated after the surgery—still a limitation of this method. 

In conclusion, the impaired macular retinal function was partially recoverable in the early postoperative period. Later, further improvement was demonstrated after macular translocation. 

 Supported by Grants-in-Aid 13307048 and 14370557 from the Ministry of Education, Science, Sport and Culture, Tokyo, Japan.

 Submitted for publication February 22, 2003; revised September 26, 2003; accepted September 28, 2003.

 Disclosure: H. Terasaki, None; K. Ishikawa, None; Y. Niwa, None; C.-H. Piao, None; T. Niwa, None; M. Kondo, None; Y. Ito, None; Y. Miyake, None

 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

 

Table 1.

 

Patients’ Characteristics

Case	Age/Gender/Eye Side	Diagnosis	Size of Lesion (DD)	Type of Lesion (Predominantly)	Duration of Symptoms (mo)	Best Corrected Visual Acuity											Post-op Follow up (mo)	Complication
												Pre-op	Early Post-op	(mo)	Late Post-op	(mo)		Final		Type	CME	Muscle OP	IOP
1	73/M/R	ARMD	1.33	Classic	6	20/100	20/133	7	20/100	28	20/100	36		+
2	62/M/R	ARMD	1.33	Classic	5	20/667	20/200	6	20/67	30	20/33	38	Juxtafoveal PFCL		+
3	77/M/R	PCV	2.33		8	20/333	20/40	5	20/33	20	20/29	29	Enlarged vascular network (PC)	+
4	79/F/R	ARMD	2.63	Classic	4	20/333	20/200	6	20/67	25	20/100	28		+
5	70/M/R	ARMD	1.13	Classic	2	20/100	20/200	6	20/100	27	20/100	28		+
6	71/F/L	ARMD	1.23	Classic	2	20/200	20/133	7	20/100	21	20/100	27
7	67/F/R	ARMD	1.08	Classic	5	20/200	20/200	11	20/67	21	20/67	26		+	+
8	74/M/L	ARMD	1.00	Classic	3	20/200	20/100	11			20/100	25		+
9	63/M/L	ARMD	1.00	Classic	5	20/100	20/67	6			20/40	25	After cataract (YAG capsulotomy)		+	+
10	72/F/R	ARMD	1.00	Classic	5	20/286	20/100	12	20/100	21	20/50	24		+
11	64/M/R	ARMD	0.89	Classic	3	20/100	20/33	6	20/50	20	20/50	24	Recurrence from the scar (PC)	+
12	71/M/R	ARMD	2.61	Classic	7	20/200	20/500	6	20/200	18	20/222	23		+		+
13	64/M/L	PCV	2.23		1	20/800	20/500	6	20/800	19	20/667	23			+
14	67/M/L	ARMD	1.20	Classic	6	20/100	20/133	6	20/67	19	20/100	22	RPE translocation	+		+
15	68/M/R	ARMD	1.11	Classic	8	20/500	20/67	12			20/100	20		+	+	+
16	78/F/R	ARMD	0.79	Classic	10	20/133	20/50	12			20/50	18
17	80/M/L	ARMD	1.25	Classic	12	20/288	20/250	12			20/133	18		+
18	87/M/L	ARMD	1.69	Classic	2	20/200	20/100	12			20/100	18	Subretinal PFCL			+
19	80/M/L	ARMD	1.33	Classic	3	20/400	20/67	8			20/67	13

 PFCL, liquid perfluorocarbone; PC, treated by photocoagulation; CME, angiographic cystoid macular edema with normal macular configuration, by optical coherence tomography; muscle op, secondary muscle surgery for diplopia; IOP, temporary increase in IOP; DD, disc diameter.

Figure 1.

 

(A) The preoperative (abscissa) and postoperative (ordinate) visual acuities at the final follow-up. The postoperative BCVA in the 17 eyes with AMD (•) and that in the 2 eyes with PCV by (▪) are shown. (B) The mean logMAR increased significantly at the early and late follow-ups after surgery (P = 0.0074, P = 0.0050, respectively; Wilcoxon signed rank test).

Table 2.

 

Pre- and Postoperative Visual Acuity and Focal Macular ERG in AMD

	Pre-op	Post-op (early)	Significance (P)	Post-op (late)	Significance (P)
Visual acuity (LogMAR; Snellen)	1.01 ± 0.06	0.78 ± 0.07	0.0186 (n = 17)	0.63 ± 0.05	0.0116 (n = 10)
	20/205	20/121		20/85
a-Wave amplitude (μV)	0.44 ± 0.08	0.57 ± 0.06	0.1180 (n = 17)	0.82 ± 0.16	0.0218 (n = 10)
b-Wave amplitude (μV)	1.17 ± 0.16	1.34 ± 0.14	0.0262 (n = 17)	1.80 ± 0.30	0.0284 (n = 10)
b/a Ratio	2.54 ± 0.23	2.63 ± 0.34	0.9750 (n = 14)	2.45 ± 0.28	0.9528 (n = 10)
a-Wave implicit time (ms)	26.0 ± 0.9	26.9 ± 0.7	0.2083 (n = 14)	27.4 ± 1.03	0.4413 (n = 10)
b-Wave implicit time (ms)	55.9 ± 1.2	53.5 ± 1.1	0.1208 (n = 17)	51.9 ± 1.9	0.0924 (n = 10)

 Data in bold indicate significant difference.

Figure 2.

 

Waveform of fmERGs in eight representative cases before and early (6–12 months) and late (18–30 months) after macular translocation and that of a normal subject. Note the increased a-wave in cases 2, 10, and 14 and the increased b-wave in cases 2, 3, 7, and 11 early after surgery. At the late recordings, marked increases in the a- and b-waves in cases 1, 7, 10, 11, and 14 can be seen. The case numbers correspond with those in Table 1 .

Figure 3.

 

The (A) a- and (B) b-wave amplitudes before and after surgery. (•) Recordings in 17 AMD eyes, early after surgery; (▪) recordings in 2 PCV eyes, early after surgery; and (⋄) recordings in 12 eyes late after surgery. (↑) Increase in amplitude after repeated recordings; (↓) a decrease in the amplitude.

Figure 4.

 

The mean amplitudes and implicit times of a- and b-waves in patients with AMD, before surgery (17 eyes) and early (17 eyes) and late (10 eyes) after surgery. (A) The increase in a-wave amplitude early after surgery is not significant (P = 0.1180); however, the increase late after surgery is significant (P = 0.0218). The increase in the b-wave amplitude early after surgery and late after surgery are significant (P = 0.0262, P = 0.0284, respectively; Wilcoxon signed rank test). (B) Implicit time of the a-wave in patients with AMD was measurable in 14 of 17 eyes before surgery, 17 of 17 eyes early after surgery, and 10 of 10 eyes late after surgery. The differences between these three were not significant. Implicit time of the b-wave was measurable in all 17 AMD eyes. Implicit time of the b-wave early and late after surgery decreased, but the decrease was not statistically significant (P = 0.1208, P = 0.0924, respectively, Wilcoxon signed rank test).