Ординатура / Офтальмология / Английские материалы / Hyperopia and Presbyopia_Tsubota, Boxer Wachler, Azar_2003

Figure 2 Defocus curve. Two spikes for far and near can be observed.

b. Glare and Halo

Another caveat would be glare and halo, especially at night. When the pupil is dilated in dim light, some patients recognize halo due to its annular design.

c. Incorrect Power

The correct biometry is very important for this particular IOL. Especially when clear lens extraction is planned, this is critical. Patients expect better uncorrected vision at far and near. Even with perfect surgery, the results can be miserable if the IOL power calculation fails.

C. INDICATIONS/CONTRAINDICATIONS

Some indications and contraindications depend on the type of multifocal IOL. Recent refractive-type IOLs are indicated for most patients if they are not included in exclusion criteria (Table 1).

1. Cataract

In case of cataract surgery for a younger patient, this IOL can avoid the loss of accommodation, an undesirable complication. The results in this age group may represent the possibility of treating presbyopia.

Table 1 Exclusion Criteria

Patient with multifocal IOL in the fellow eye

Uncontrolled glaucoma

Progressive diabetic retinopathy

Corneal lesions that may affect visual acuity

Other complications that may affect visual acuity

Preoperative astigmatism greater than 1.5 D

Frequent driving or operation of dangerous machinery at night

2. Expectation of the Patient

The patient who is highly motivated is often a good candidate. The increased number of refractive surgeries has proved that many patients long for life without spectacles and contact lenses. Younger patients underage 45 are also candidates, since the most undesirable complication following cataract surgery at this age is the loss of accommodation. Despite their perfect vision at far, they may suffer from the new experience of not being able to read without spectacles.

3. Occupation

Individuals with occupations that require good far and near vision in which the use of spectacles or contact lenses might be dangerous represent another good candidate group.

D. PREFERRED SURGICAL TECHNIQUES

The preferred surgical techniques should provide predictability of postoperative refraction and stability of IOL position. For this purpose, small incision and continuous curvilinear capsulorhexis (CCC) are recommended.

1. Incision

It is well known that surgically induced astigmatism has recently been diminished by the use of small-incision cataract surgery. For this purpose, a foldable multifocal IOL is preferable. Also, a self-sealing incision should be made so as to avoid suture-induced astigmatisms.

2. IOL Position

Capsular bag implantation of IOLs provides a stable position. IOL tilt or decentration causes severe complications with multifocal IOLs due to their design. Thus, CCC should be completed. If the IOL haptics position is unclear, which may cause unpleasant phenomena such as glare and halo, one should try to implant the IOL symmetrically, either both haptics in the capsular bag or in the sulcus.

3. Posterior CCC

Near vision can easily be decreased by the posterior capsular opacity with multifocal IOLs. In other words, the rate of neodymium:YAG capsulotomy is higher than that of monofocal

IOLs. If the opacity or the fibrosis of the posterior capsule is obvious and cannot be polished during surgery, one may perform posterior CCC. Especially when we implant multifocal IOLs in younger patients, we should consider performing posterior CCC, since a neodymium:YAG capsulotomy may be necessary earlier.

a. Clinical Results

There have been many reports on the results of multifocal IOLs following cataract extraction. The reports on multifocal IOL with clear lensectomy are limited. The desirable results with cataract patients persuade clear lensectomy for the patient who would like to have refractive surgery, including the correction of presbyopia.

b. Visual Acuity (VA)

Table 2 shows the reported results of several multifocal IOLs (2). The time-lapse changes of the mean postoperative VA in a Japanese clinical study are shown in Table 3. The average distance uncorrected VA was 20/25, best corrected VA was better than 20/20. For near, uncorrected VA was 0.39, with distance correction, it was 0.43; and best corrected

Table 3 Time Lapse Changes of the Average VA

VA was 0.77. The VA at the 1 week postoperative visit was as good as the one at 1 year. We can expect early visual recovery with this type of IOL.

c. Contrast Sensitivity

The loss of contrast sensitivity with multifocal IOLs is accepted as a drawback of this design. Despite previous reports, our results are encouraging. The mean contrast sensitivity at 1 year after the operation was above the lowest of normal range (Fig. 3). Contrast VA with variable-contrast charts (VCVAC) showed that the contrast VA of the eye with a multifocal IOL in 15 and 2.5% contrast was comparable to that with a monofocal IOL (Fig. 4).

d. Halo and Glare

Halo and glare are also of concern following multifocal IOL surgery. One year after the operation, patients were asked about halo and confirmed its intensity. At each final followup observation, 22.4% complained mild or moderate halo, which was only a transient symptom in every case against sun in daytime and/or light sources at night. This was not experienced to the extent of causing problems in daily life. Glare values were measured by Miller-Nadler Glaretester and percent glare was 5.6. No percent glare decrease was observed, potentially generating clinical problems.

e. Spectacle Usage

It is not easy to analyze spectacle usage, since some patients use spectacles most of the time and the others use them only when necessary. Approximately 60% were able to function comfortably without spectacles. Figure 5 shows the changes of using spectacles by the follow-up time. Until 1 month after operation, most patients were not using specta-

Figure 3 Contrast sensitivity. The mean contrast sensitivity after the operation was above the lowest of normal range.

Figure 7 Vision simulation system.

cles. Once they get used to read with reading glasses, some prefer the clear letters using the zone for far with additional correction with spectacles. That is why the rate for spectacle usage increases after 3 months or 1 year.

e. Patient’s Satisfaction (Questionnaire)

It is important that patients be satisfied with the results (Fig. 6). Especially if clear lens extraction has been performed, patients expect better reading ability.

f. Patient’s View with Model Eye

a. Vision Simulation System

The concern of implanting multifocal IOL is that the surgeon or patient cannot estimate the view after the surgery. Because of this, it takes a long time to explain to the patient about the results of multifocal IOL. The image through multifocal implantation was recorded using the vision simulation system developed by Ohnuma (Fig. 7) (3).

b. Patient’s View

Using photos taken by the vision simulation system, the view of the patient was examined. First, the view was seen by each eye while the fellow eye was covered. Then the view was compared with each eye. The photo which was most similar to the view with multifocal IOL was chosen.

The results are shown in Figure 8. During the day, the vision is clearer than that with a multifocal IOL and closer to the view with a monofocal IOL. However, for near vision, the photo taken by the model eye was similar to the real view with a multifocal IOL.

E. COMPLICATIONS AND MANAGEMENT

1. IOL Power Miscalculation

When the biometry was not perfect and the patient ends up with myopia or hyperopia, he or she may not receive the advantage of multifocal IOL. It is known that this type of multifocal IOL should be emmetropic to slightly hyperopic (Fig. 9A). If the postoperative refraction is more than 0.5 D, the blur circles become larger at distance and near compared to emmetropia (Fig. 9B)). This will cause potential halos at night. If the postoperative

Figure 8 Patient’s view. (A) Clinic at day. (B) Clinic at night. (C) Clock.

refraction is hyperopic, halo at night should be minimal (Fig. 9C). Thus, postoperative refraction is an important factor. IOL exchange or piggyback implantation should be considered if the patient suffers halo at night or strongly wishes better distance and near vision.

2. IOL Decentration

With the introduction of CCC, clinically obvious decentration of IOL became rare. However, when it occurs, it may cause visual disturbance. Mostly, these are caused by asymmet-

Figure 9 Refractive error and blur circles. (A) Emmetropic to slightly hyperopic (plano to 0.5 D). (B) Myopic refraction ( 0.5). (C) Hyperopic refraction ( 0.5 D).

rical fixation of the IOL. Surgical replacement of the IOL should be considered. If the replacement is not possible due to the defect of posterior capsule, one may consider exchanging the IOL to monofocal IOL.

3. Halo and Glare Vision

Complications are mainly related to IOL design. Most common complaints are halo and glare at night. These are usually relieved by time. From our questionnaire, some patients

have reported being bothered with halo and glare while they were driving at night. However, the readability of traffic signs is about the same as with monofocal IOLs.

4. Insufficient Near Vision

This is caused by incorrect IOL power calculation, small pupil diameter, or opacity in the path from cornea to retina. The former two reasons are most common. If the incorrect IOL power is the main reason, one may consider IOL exchange or piggyback implantation. If the pupil diameter is smaller than the near zone, the patient will not get the advantage of near addition.

F. CONCLUSIONS

Treating presbyopia is still a challenge. However, we already have clinical data of implanting multifocal IOLs for cataract patients. At this time, if the patient will need cataract surgery sooner or later, multifocal IOL is a rather safe way to treat presbyopia. On the other hand, for the patient with a clear lens, this may be a decision to be made by the surgeon. The surgeon must be confident in his or her biometry and surgical technique. If the patient understands the risk of removing the lens and implanting an IOL, a multifocal IOL should always be considered as the best choice for the treatment of presbyopia.

REFERENCES

1.Steinert RF, Post CT Jr, Brint SF, Fritch CD, Hall DL, Wilder LW, Fine IH, Lichtenstein SB, Masket S, Casebeer C. A prospective, randomized, double-masked comparison of a zonalprogressive multifocal intraocular lens and a monofocal intraocular lens. Ophthalmology 1992; 99:853–860.

2.Negishi K, Bissen-Miyajima H, Kato K, Kurosaka D, Nagamoto T. Evaluation of a zonalprogressive multifocal intraocular lens. Am J Ophthalmol 1997; 124:321–330.

3.Ohnuma K. Image focused by a multi-focal intraocular lens and its estimation. J Eye 2001; 18: 395–400.