Ординатура / Офтальмология / Английские материалы / Hyperopia and Presbyopia_Tsubota, Boxer Wachler, Azar_2003
.pdf
230 |
Phillips and Yee |
Figure 14 (A and B) The dimensions of the segment.
sometimes necessary to pass the segment upside down and then rotate the segment into place using the injector and heavy needle holder. Rotation of the segment will stretch the belt loop, but a slightly stretched belt loop will produce a greater effect than a thin belt loop. If it is still not possible to pass the segment, the segment may be getting caught in a blind pocket. Reapply the scleral fixator at the opposite end of the tunnel and try passing the segment in reverse by beginning at the exit side of the scleral belt loop.
If the patient suddenly moves or complains of eye pain, immediately stop advancing the segment. This may indicate that the vitreous, subchoroidal space, or ciliary body has been entered. This can be confirmed by the presence of vitreous or fluid containing black pigment exiting one or both ends of the scleral belt loop. At this point, the segment should be removed and the eye examined. If the surgeon feels it is safe, it may still be possible to pass the segment upside down from the other direction.
If the scleral belt loop is torn or severed, remove the segment and close the sclera. The operation may be completed after the sclera is healed in 2 or 3 months.
Figure 15 Placement of the segment.
The Scleral Expansion Procedure |
231 |
I. CONJUNCTIVAL CLOSURE
Sutures are placed at the 12:00 and 6:00 o’clock meridians by passing the suture through the conjunctiva and back out through the sclera and burying the knot. The corners of the conjunctival incision should be overlapped. Finally, administer 20% mannitol (1 g/kg) intravenously over 30 min to avoid malignant glaucoma.
J. CHECK THE PUPILS THE NEXT POSTOPERATIVE DAY
The pupils should be checked for reactivity and pupil size. An irregular or dilated pupil may suggest AIS or sector AIS. If a pupillary abnormality is noted, place one drop of 0.5% pilocarpine in each eye. Pupillary constriction provides evidence that adequate anterior segment blood flow is present. The sine qua non for AIS is a dilated nonreactive pupil or a nonreactive pupillary sector. Other signs of AIS are nausea, an intraocular pressure (IOP) less than 10 mmHg, corneal edema and folds, and anterior chamber cell and flair (Fig. 16). At this point some recommend that the segment or segments causing AIS be immediately removed. Others recommend giving the patient an additional dose of intravenous manitol and 2 to 4% pilocarpine every 5 min for a total of six times in addition to oral or intravenous steroids and aspirin if not contraindicated (21). If the pupil does not respond in 2 h, repeat the manitol and six doses of pilocarpine (21). If there is still no response after another 2 h, the segments should be removed.
Artificial tears, topical antibiotics, and topical anti-inflammatory or nonsteroidal agents should be administered postoperatively. It is recommended that topical antibiotics and anti-inflammatory eye drops be used for 2 weeks. Any remaining sutures should be removed after 10 to 14 days. Artificial tears should be used frequently and a bland ointment administered at night for at least 3 months.
Some patients complain of a mild to severe brow ache beginning about 30 min after surgery and lasting 2 to 6 h. It may be necessary to treat these patients with analgesics.
K. EYE EXERCISES
Following the procedure, it is important that patients perform accommodation eye exercises for rehabilitation of the ciliary muscle (22). Patients are asked to exercise from near to
Figure 16 Characteristic photograph of a dilated pupil and corneal folds consistent with anterior ischemic syndrome.
232 |
Phillips and Yee |
far rather than far to near. Patients should hold an eye chart 4 in. (10 cm) from their eye and look at the smallest line they can see. Patients are then asked to concentrate until they can see any letter on the next smaller line. Next they should hold fixation on the letter on the smaller line and slowly move it away from the eye until it is at full arm’s length. The eye chart can then be brought slowly back toward the eye while continuously holding fixation on the smaller line until the eye chart is back at 10 cm from the eye. Once they can read all the letters on that smaller line, have them move to the next smaller line and again move the eye chart to arm’s length while maintaining fixation on the smaller line, and so on. Patients should repeat this exercise as frequently as possible, but for at least 10 repetitions, four times a day, each time trying to fixate on a smaller line beginning at the close distance of 10 cm from the eye. It is much better to do frequent exercise sessions throughout the day than one long session. Following the exercises, patients will notice that they can read better. Patients will usually experience ciliary pain during the exercises for the first 2 weeks after surgery. The patients can be told that this pain is a good sign and that the exercise is strengthening their ciliary muscles. Patients should avoid the use of a near vision optical aid during their daily reading tasks. Additionally, patients should squint as little as possible during the eye exercise; if they initially have difficulty performing their daily reading tasks, encourage them to use a bright light or, only if absolutely necessary, to squint in order to avoid the use of a near optical aid. As they continue the eye exercise, the requirement to squint or use a bright light during their daily reading tasks will decrease.
L. COMPLICATIONS
Only one case of AIS has been reported using the latest 5.5-mm scleral expansion segments (23). This complication may have resulted from improper positioning of the segments (23). One case of endophthalmitis has also been reported (23). This case was thought to result from a break in sterile technique (23). Additionally, one case of scleral thinning similar to that observed with scleral buckles has been reported and may have been a result of scleral expansion (24). To date, no cases of malignant glaucoma have been reported using the new scleral expansion segments. Theoretically, this is a possibility, as the segments may increase posterior pressure, blocking outflow and resulting in aqueous misdirection. Intravenous manitol is given to dehydrate the vitreous decreasing the likelihood of this complication. Other minor complications include conjunctival hyperemia, subconjunctival hemorrhage, transient ptosis, rotation or subluxation, of the scleral expansion segments, photophobia due to tear film instability, conjunctival erosion, accommodative fatigue, temporary keratoconjunctivitis, swollen or irregular conjunctiva, and astigmatism, which may last for 2 to 3 months and but subsides with intense treatment with artificial tears.
M. CLINICAL RESULTS
Increases in accommodation after this technique have ranged from 1.00 to 10.00 D (13). Two different studies (20) of 29 and 7 patients have reported an increased range of accommodation in all patients, with an average of 3.02 and 3.13 D respectively. Similar to our findings, an increased range of near vision was also noted in the unoperated eye. This increase approached 20 to 50% of the increase measured in the operated eye.
The Scleral Expansion Procedure |
233 |
N. SCLERAL EXPANSION AND OTHER REFRACTIVE PROCEDURES
Scleral expansion has been successfully performed after LASIK, PRK, and RK. With regard to LASIK, however, it is easier to perform LASIK before scleral expansion due to difficulties that may be encountered while applying the suction ring. Scleral expansion has been performed as early as 6 weeks post-LASIK. Obviously, PRK and laser epithelial keratomileusis (LASEK) are good alternatives for patients who have had previous scleral expansion procedures.
O. OTHER SCLERAL EXPANSION PROCEDURES
Several other methods have been used to expand the sclera. Some surgeons have made simple scleral incisions with a diamond knife to expand the sclera. The scleral incisions are limited to an accommodative range of only about 1.50 D, and, as the incisions heal, the effect declines (R. Schachar, personal communication, 2001). In order to prevent the incisions from healing, Fukasaku has inserted silicone plugs into the scleral incisions (24a). The infrared laser has also been used to make deep scleral incisions (25). The average correction is also limited to an accommodative range of about 1.50 D and will likely regress with time (R. Schachar, personal communication, 2001). In contrast to the above, Lin has described no regression after scleral expansion using infrared laser (J. Lin, personal communication, 2001). A major concern with the infrared laser is that it can coagulate blood vessels and lead to anterior segment ischemia. There have been two phthisical eyes as a result of making scleral incisions with the infrared laser for the treatment of presbyopia (R. Schachar, personal communication, 2001). Last, as a result of the deeper tissue ablation, the potential for rupture after blunt trauma is also a concern.
P. SCLERAL EXPANSION AND GLAUCOMA
While chronic open-angle glaucoma is a genetic disease, predisposed patients may benefit from scleral expansion due to anatomical modifications produced by the procedures in the ciliary muscle and trabecular meshwork (26,27). International clinical trials evaluating scleral expansion for the treatment of ocular hypertension and primary open-angle glaucoma in Canada and Mexico have demonstrated excellent preliminary results (27,28). The median decrease in IOP after scleral expansion was 7 mmHg, and the postoperative decrease in IOP appears to be equivalent to the IOP-lowering effect of the preop, physicianprescribed topical glaucoma medications (27).
Q. SUMMARY
Scleral expansion is a new procedure designed to treat presbyopia surgically. While the theory on which it is based continues to be a subject of intense debate, it must be noted that patients report an improved ability to read at near after scleral expansion. Given the immense impact of presbyopia, surgical reversal of presbyopia will likely continue to be an area of significant interest. In addition, scleral expansion may offer a new modality for the treatment and prevention of ocular hypertension and primary open-angle glaucoma. If scleral expansion is found to effectively decrease IOP, the adverse reactions and systemic side effects commonly observed with glaucoma medications could be avoided and potential surgical filtering and shunt procedures could be delayed or eliminated.
234 |
Phillips and Yee |
ACKNOWLEDGMENT
The authors would like to thank Presby Corp for their assistance in writing this chapter and the illustrations they provided. Additionally, we would like to thank Dr. Adrian Glasser and Dr. Ronald Schachar for their comments.
REFERENCES
1.Donders FC. On the Anomalies of Accommodation and Refraction of the Eye. London: The New Sydenham Society, 1864:204–214.
2.May CH, Perera CA. Manual of the Diseases of the Eye for Students and General Practitioners, 17th ed. Baltimore: William Wood and Company, 1941:365–366.
3.von Helmholtz H. U¨ ber die Akkommodation des Auges. Graefes Arch Klin Exp Ophthalmol 1855; 1:1–89.
4.Rohen JW. Scanning electron microscopic studies of the zonular apparatus in human and monkey eyes. Invest Ophthalmol Vis Sci 1979; 18:133–144.
5.Fisher RF. Presbyopia and the changes with age in the human crystalline lens. J Physiol (Br) 1973; 228:765–779.
6.Coleman DJ. Unified model for accommodative mechanism. Am J Ophthalmol 1970; 69: 1063–1079.
7.Fincham EF. The mechanism of accommodation. Br J Ophthalmol 1937; 8(suppl):5–80.
8.Stuhlman O. An Introduction to Biophysics. New York: Wiley, 1948:106–107.
9.Schachar RA. The mechanism of accommodation. Int Ophthalmol Clin 2001; 41:17–32.
10.Schachar RA. Histology of the ciliary muscle-zonular connections. Ann Ophthalmol 1996; 28:70–79.
11.Schachar RA, Tello C, Cudmore DP, Liebmann JM, Black TD, Ritch R. In vivo increase of the human lens equator diameter during accommodation. Am J Physiol (Regul Integr Comp Physiol 40) 1996; 271:R670–R676.
12.Schachar RA, Anderson DA. The mechanism of ciliary muscle function. Ann Ophthalmol 1995; 27:126–132.
13.Schachar RA, Black TD, Kash RL, Cudmore DP, Schanzlin DJ. The mechanism of accommodation and presbyopia in the primate. Ann Ophthalmol 1995; 27:58–67.
14.Schachar RA. Zonular function: a new hypothesis with clinical implications. Ann Ophthalmol 1994; 26:36–38.
15.Schachar RA, Cudmore DP, Black TD. Experimental support for Schachar’s hypothesis of accommodation. Ann Ophthalmol 1993; 25:404–409.
16.Schachar RA. Cause and treatment of presbyopia with a method for increasing the amplitude of accommodation. Ann Ophthalmol 1992; 24:445–452.
17.Yang GS, Yee RW, Cross WD, Chuang AZ, Ruiz RS. Scleral expansion: a new surgical technique to correct presbyopia. Invest Ophthalmol Vis Sci 1997; 38(suppl):S497.
18.De Smet MD, Carruthers J, Lepawsky M. Anterior segment ischemia treated with hyperbaric oxygen. Can J Ophthalmol 1987; 22:381–383.
19.Jampol LM. Oxygen therapy and intraocular oxygenation. Trans Am Ophthalmol Soc 1987; 85:407–437.
20.Cross WD, Zdenek GW. Surgical reversal of presbyopia. In: Agarwal S et al, eds. Refractive Surgery. New Delhi: Jaypee Brothers Medical Publishers, 2000:592–608.
21.Cross WD. Scleral expansion band technique treats presbyopia. Ocul Surg News 2001; 19: 28–34.
22.Ruelas V. Optometric postoperative care. In: Schachar RA, Roy FH, eds. Presbyopia: Cause and Treatment. The Hague, The Netherlands: Kugler, 2000: 105–107.
23.Zdenek G. Complications in surgical reversal of presbyopia can be avoided, managed. Ocul Surg News 2001; 19:39–44.
The Scleral Expansion Procedure |
235 |
24. Singh G, Chalfin S. A complication of scleral expansion surgery for treatment of presbyopia. Am J Ophthalmol 2000; 130:521–523.
24a. Fukasaku H, Marron JA. Anterior ciliary sclerotomy with silicone expansion plug implantation: effect on presbyopia and intraocular pressure. Int Ophthalmol Clin 2001; 41:133–141.
25.Johannes L. Is the end of reading glasses in sight? The Wall Street Journal. March 28, 2001, P B1.
26.Schachar RA. The scleral expansion band procedure: Therapy for ocular hypertension and primary open angle glaucoma. Ann Ophthalmol 2000; 32:87–89.
27.Rifkind AW, Yablonski ME, Shuster JJ. Effect of scleral expansion band (SEB) on ocular hypertension Canada phase 1 study. Compr Ther 2001; 27:333–340.
28.Cross WD, Marmer RH, Shuster JJ. A pilot study to determine the effect of the scleral expansion band (SEB) procedure on ocular hypertension. Submitted.
22
Multifocal IOLs for Presbyopia
HIROKO BISSEN-MIYAJIMA
Tokyo Dental College, Suidobash Hospital, Tokyo, Japan
A. BACKGROUND
With recent advancements in refractive surgery, we can achieve sufficient results in the treatment of myopia, hyperopia, and astigmatism. Patients are able to appreciate good uncorrected visual acuity (VA), and their quality of life can also be improved. The next interest goes to how we can treat presbyopia. Several methods have been introduced. Implantation of multifocal intraocular lenses (IOLs) instead of original crystalline lenses is familiar to the ophthalmic surgeon, since we are performing this technique for cataract patients for many years. We could learn most results of multifocal IOLs from our cataract patients.
1. Cataract Surgery as Refractive Surgery
When the IOL was introduced, both patients and the surgeons were impressed by the resulting relatively good vision without spectacles or contact lenses. Recently, cataract surgery has been accepted as refractive surgery, since we can correct preoperative myopia or hyperopia at the time of surgery. Even clear lens extraction following IOL implantation is accepted for the treatment of extreme myopia or hyperopia. An ideal IOL would be one that would replace the original crystalline lens at younger age. We can correct not only preoperative refractive error but also age-related presbyopia.
2. Impression of the Multifocal IOL
When the multifocal IOL was first introduced, we expected it to act like bifocal spectacles, so that the patient would have clear vision at far and near. The results with first-generation multifocal IOLs were somewhat disappointing, however, since the distance visual acuity
237
238 |
Bissen-Miyajima |
was dependent on pupil size and sometimes inferior to that with monofocal IOLs. Another concern is the loss of contrast sensitivity. Because of these unpleasant drawbacks, many surgeons went back to implanting conventional monofocal IOLs. The results of recent multifocal IOLs are more promising and the interest in this type of IOL has increased again.
B. THEORETICAL BENEFITS AND CAVEATS
Before describing theoretical benefits and caveats, one should understand the different designs of IOL.
1. Different Types of Multifocal IOLs
a. Refractive Type
The initial refractive type was two zones with a central 2-mm button for near, and this IOL was called “bull’s eye” (Fig. 1A). The center part had additional 4 D, which would be equivalent to 2.5 D in spectacles. If the pupil size was too small, the patient had insufficient visual acuity and this lens was abandoned. Then other types of refractive IOLs were introduced (Fig. 1B and C). Some are far-dominant and others are near-dominant.
Recently, the zonal progressive type of AMO ARRAY (Fig. 1D) became a standard multifocal IOL in several countries. The center part is for far vision and patients usually get good distance visual acuity (VA).
b. Diffractive Type
Another type is the diffractive type, which is not affected by pupil size. This IOL has a 0.6-mm central zone and some 30 annular diffracting zones on its posterior surface (Fig. 1E). The light can be diffracted toward two foci; 41% for near and 41% for distance. Thus, 18% of the light would be lost, and the loss of contrast sensitivity became the biggest concern.
2. Theoretical Benefit
a. Less Dependence on Spectacles
Theoretical benefits of multifocal IOLs are based on their depth of focus. Figure 2 shows the results of distance visual acuity with defocus of the patient from emmetropia following AMO ARRAY. There are two spikes, which means that the patient can focus both far and near. Another interesting thing about this particular IOL is that the valley between two spikes is not deep and patients have a chance to see things at middle distance. Thus, the potential of not depending on spectacles is high.
3. Theoretical Caveat
a. Decreased Contrast Sensitivity
The caveat of multifocal IOLs in general is the loss of contrast sensitivity due to their design. By in a randomized study of multifocal IOLs, a significant decrease of visual acuity was reported at 11% contrast with multifocal IOLs compared to the monofocal IOLs (1). Although this problem can be detected by examination of contrast visual acuity, most patients do not have the problem in daily life.
Multifocal IOLs for Presbyopia |
239 |
Figure 1 (A) IOLAB two-zone refractive type with a central 2-mm button for near. (B) IOPTEX.
(C) Pharmacia. (D) AMO ARRAY. (E) Diffractive IOL (3M). This IOL has a 0.6-mm central zone and some 30 annular diffracting zones on its back surface.