Hyperopia and presbyopia - part 7 pps

194 Azar et al. The most commonly used approach, however, is determining which eye is the domi- nant eye and correcting that eye for the most commonly used viewing distance (11), which is generally considered to be the far distance. The dominant eye has been shown to be superior for spatial-locomotor tasks such as walking, running, or driving a car (2,20). Blur suppression appears to be greater when the dominant eye is corrected for the most com- monly used distance (i.e., far) (3). Correcting the dominant eye for distance also produces less esophoric shifts (21). The dominant eye is generally identified by use of sighting dominance tests (22). One of the more common tests is the hole test (8), for which the patient is asked to frame an object that lies at an intermediate distance from him or her with a triangle created by his or her outstretched arms while keeping both eyes open. The eye that is in alignment with the object and the hole is considered the dominant eye. I. CROSSED MONOVISION Crossed monovision occurs when the nondominant eye is corrected for distance and the dominant eye for near. This can happen either accidentally or intentionally (1). Crossed monovision may be the intended goal when, for example, a contact lens monovision trial demonstrates better visual function if the nondominant eye is corrected for distance. A patient may also change his or her mind regarding monovision versus full distance correc- tion for both eyes after the nondominant eye has already been treated for distance and the dominant eye has not yet been treated. Patients who wish to have only one eye treated and who are markedly more myopic in the nondominant eye may elect to have the nondomi- nant eye corrected for distance (1,3). Unintentional crossed monovision can occur when correction in the dominant eye is less than expected in patients requesting full distance correction for both eyes. Con- versely, in patients desire equivalent undercorrection in both eyes, an overcorrection in the nondominant eye can produce crossed monovision. Unintentional crossed monovision is a result of the fact that refractive surgery is not a completely predictable procedure (1). J. UNCROSSED MONOVISION VERSUS CROSSED MONOVISION Of our 97 LASIK patients, 69 (71.1%) had uncrossed monovision, and 28 (28.9%) had crossed monovision. The average age was 51.7 ע 0.5 years for patients with uncrossed monovision and 49.7 ע 0.7 years for patients with crossed monovision (pס0.04). The two groups were similar with regard to distribution of gender, dominance, myopia, type of laser used, and type of microkeratome used (␹ 2 סNS). The average anisometropia of uncrossed monovision patients was 1.28 D, and of crossed monovision patients 0.98 D (pס0.03). Of the 69 uncrossed monovision patients 56 (81.2%) were satisfied after LASIK, as were 22 (78.6%) of the 28 crossed monovision patients. Two (33.3%) of the 6 patients dissatisfied with crossed monovision and 2 (15.4%) of the 13 patients dissatisfied with uncrossed monovision were unhappy for reasons unrelated to monovision, such as dry- eye symptoms and floaters. One patient each (16.7%) complained of poor distance vision, poor near vision, imbalance, and poor overall quality of vision in the crossed monovision group. Of the 13 dissatisfied uncrossed monovision patients, 3 (23.1%) complained of poor distance vision, 2 (15.4%) were unhappy with near vision, 5 (38.5%) felt imbalanced, and 1 (7.7%) was unhappy with overall quality of vision. 195Monovision Refractive Surgery for Presbyopia Among minimonovision patients, 19 of the 24 (79.2%) patients with uncrossed monovision were satisfied, as were 10 of the 13 (76.9%) with crossed monovision. Of the monovision patients, 37 of the 45 (82.2%) patients with uncrossed monovision were satisfied, as were 12 of the 15 (80.0%) crossed monovision patients. Of the 3 patients who were monovision failures, 2 had crossed monovision. One patient with crossed monov- ision was retreated to uncrossed monovision, while the other two patients did not have a change in crossed monovision status. The patient with uncrossed monovision before and after retreatment remained dissatisfied. K. VISUAL PERFORMANCE IN MONOVISION 1. Monovision Failures All 13 patients dissatisfied with monovision outcome were offered retreatment, but only 3 (23.1%) elected to undergo a second procedure. Most patients chose to defer retreatment for one of three reasons (1) the patient was unwilling to sacrifice near and intermediate vision for sharper distance vision, (2) symptoms were not bothersome enough to merit risks of additional surgery, and (3) the patient was willing to give additional time to adjust to monovision. Patients were then prescribed glasses for distance vision or reading, depending on the complaint, or were to be re-evaluated for retreatment following some period of adjustment. Many patients were then lost to follow-up. This suggests that the degree of dissatisfaction was relatively mild and that many patients eventually adjust to monovision or wear glasses on occasion for specific activities. Overall patient satisfaction with monovision after LASIK was 80.4%, compared to 80.6% in contact lens wearers after exclusion of contact lens intolerance. Furthermore, the satisfaction among strict monovision, minimonovision, uncrossed monovision, and crossed monovision groups did not differ significantly from satisfaction in contact lens wearers. Due to the retrospective nature of most monovision refractive surgical studies, there was no standardized instrument to measure patient satisfaction. Rather, patient dissatisfac- tion was noted if the patient had any complaints or negative comments about vision at the last follow-up visit. In addition, near vision was not documented in many charts and could not be analyzed as an outcome. It was also difficult to determine from charts whether monovision was intended or whether regression of one or both eyes led to a monovision result. These factors may be better analyzed through a prospective study. 2. Interocular Blur Suppression Two tests used to measure the ability to suppress interocular blur are the anisometropic blur-suppression test and the American Optical vectographic test. The anisometropic blur- suppression test indicates that the interocular suppression of blur is greater for smaller degrees of anisometropia (2). Both testing modalities indicate that blur suppression is greater when the dominant eye is corrected for distance. Monovision success is dependent on interocular blur suppression. In successful wear- ers of monovision lenses, the interocular suppression of blur was found to be approximately two orders of magnitude greater than in unsuccessful wearers of monovision lenses (2). Of note, interocular blur suppression becomes less effective under dim illumination condi- tions (2), which accounts for the well-known poorer visual performance of monovision patients under night driving circumstances. 196 Azar et al. 3. Binocular Visual Acuity Jain and colleagues (1,2) reviewed six articles addressing the effect of monovision on binocular visual acuity and found the effect to be mild. High-contrast and low-contrast visual acuities at standard room illumination were found to be reduced by 0.04 to 0.08 logMAR unit and 0.04 to 0.09 logMAR unit, respectively. This reduction was slightly higher (0.10 logMAR unit) under low illumination conditions. The effect on visual acuity was particularly pronounced when the dominant, distance-corrected eye had a residual astigmatic error at an oblique axis (23). 4. Stereoacuity Reduced stereoacuity is considered to be the major disadvantage associated with monovi- sion (24). Jain and coworkers reviewed twelve articles that examined the effect of monovi- sion on stereoacuity (1,2). When near stereoacuity under monovision conditions was com- pared to stereoacuity under binocular viewing conditions, a mean decrease of 37 arc seconds (from 87 to 124 arc seconds) was found. The average normal value for stereopsis is 20 arc seconds and, for persons over 40 years of age, 58 arc seconds (13,25). A more recent paper by Kirschen and coworkers found that near stereoacuity decreased from a median of 50 arc seconds with bifocal contact lenses to 200 arc seconds with monovision (26). Patients in whom monovision is successful exhibit a lower reduction in stereoacuity than do unsuccessful monovision patients. Patients in whom monovision was unsuccessful were found to have a 50 to 62 arc seconds greater reduction in stereoacuity as compared to successful monovision patients (1). 5. Contrast Sensitivity When two eyes are used instead of one, visual performance, and especially contrast sensi- tivity, greatly improves (binocular summation). Contrast sensitivity increases by a factor of ͙ 2 when the stimulus is viewed binocularly; therefore, binocular contrast sensitivity is 42% greater than monocular contrast sensitivity. With increasing monocular defocus, the binocular contrast sensitivity decreases steadily until it is actually worse than monocular contrast sensitivity (binocular inhibition) (27). If the defocus is increased beyond ם2.50 D the binocular contrast sensitivity reverts back to the monocular level, indicating suppres- sion of the defocused eye. Because monovision results in loss of binocular summation, or may even result in binocular inhibition, monovision results in a significant reduction in contrast sensitivity, especially at higher spatial frequencies (greater than 4 cycles per degree). L. PERIPHERAL VISION AND VISUAL FIELDS Monovision appears to have no significant effect on peripheral visual acuity and only a minimal effect on binocular visual field width (14). 1. Binocular Depth of Focus The binocular depth of focus is the range in which an image may move without noticeable blur under binocular viewing conditions (without changing accommodation). In patients in whom neither eye is clearly dominant (i.e., in whom there is no sighting preference), 197Monovision Refractive Surgery for Presbyopia the binocular depth of focus is approximately equal to the sum of the monocular depths of focus. However, in patients with a strong sighting preference, the image becomes blurred as the object moves from the monocular clear range of the dominant eye to the monocular clear range of the nondominant eye. Therefore, in patients with a strong sighting preference, the depth of focus under monovision conditions is considerably less than the sum of the monocular depths of focus (3). 2. Phorias Patients using monovision tend to exhibit a small-angle esophoric shift. At distance, this manifests as an esophoria. At near, the effect is offset by the fact that presbyopes generally exhibit a moderate to large exophoria at near. The magnitude of the esophoric shift is believed to correlate with the degree of binocular stress created by monovision. The eso- phoric shift at distance in successful monovision contact lens (0 to 0.6 prism diopters) was found to be less than the shift in unsuccessful monovision wearers (2.1 to 2.2 prism diopters) (7,28). Interestingly, the magnitude of esophoric shift is less when the dominant eye is corrected for distance, thus lending support to the generally accepted custom of correcting the dominant eye for distance (21). 3. Task Performance Monovision appears to be associated with adverse effects on, in particular, stereoacuity and contrast sensitivity in particular. The question is whether these effects have clinical significance. The effect of monovision on the performance of various visually oriented near tasks can be assessed by comparing an individual’s performance of these tasks under monovision conditions, under monocular viewing conditions (i.e., with one eye covered), and under binocular viewing conditions (i.e., with full near correction for both eyes). Use of this method revealed that monovision reduced performance of the tasks by 2 to 6% when compared to performance of the tasks under binocular viewing conditions. However, this reduction was quite minimal when compared with the 30% reduction seen under monocular viewing conditions with near tasks requiring high stereopsis (29). M. FACTORS INFLUENCING MONOVISION SUCCESS On the basis of the above-mentioned findings, poor candidates for monovision are patients who exhibit minimal interocular suppression of blur, patients with large esophoric shifts with monovision, and patients with a significant reduction in stereoacuity with monovision. Certain psychological and personality factors also appear to play a role in determining the success of monovision (30). An additional consideration is sighting preference. The inputs from the two eyes are not identical in their relative influence on cortical cells: the dominant eye produces a greater response to a given stimulus than does the input from the other eye. Those individu- als who do not have a strong sighting preference (i.e., who have alternating dominance) appear to have constant interocular blur suppression and therefore tend to be more success- ful with monovision. Furthermore, the choice of eye that is corrected for distance, whether the dominant or the nondominant eye, appears to have an effect on monovision success. In 16 articles reviewed by Jain and coworkers, the average age of successful monovi- sion users ranged from 48 to 55 years (1,2). No articles were found that compared the success rate in younger versus older presbyopes. Two articles examined the difference 198 Azar et al. between the average age of successful versus unsuccessful monovision patients but failed to find any statistically significant difference in age between the two groups (5,31). N. CONCLUSIONS Monovision has been evaluated extensively in contact lens users, but few studies comment on its success in refractive surgery. Furthermore, the impact of the magnitude of anisome- tropia created in monovision patients has not been fully characterized. We have introduced a new term, minimonovision, to characterize monovision patients with a lesser degree of near vision correction than full monovision (7). The inclusion criteria for strict monovision and minimonovision are mutually exclusive. We found that strict monovision and minimo- novision groups had comparable satisfaction rates. We also found that crossed monovision patients overall were as satisfied as uncrossed monovision patients, and that within the minimonovision and monovision subgroups, crossed monovision did not affect satisfac- tion. The rate of satisfaction for monovision after LASIK was similar to the rate in contact lens wearers. Monovision is associated with some compromises of visual function, the extent of which depend on the particular individual and the requirements imposed by different viewing conditions. However, for those refractive surgery patients willing and able to adapt, these compromises constitute reasonable a trade-off for reducing dependence on near-vision correction. Refractive surgery may be used to take advantage of the monovision option in presbyopic refractive surgery patients. However, this option should be pursued only after careful preoperative screening and counseling of the patient. Creating a monovision situa- tion with refractive surgery constitutes a practical alternative to other surgical treatment modalities for presbyopia, such as scleral expansion/relaxation and multifocal corneal treatment. REFERENCES 1. Jain S, Ou R, Azar DT. Monovision outcomes in presbyopic individuals after refractive surgery. Ophthalmology 2001; 108:1430–1433. 2. Jain S, Arora I, Azar DT. Success of monovision in presbyopes: review of the literature and potential applications to refractive surgery. Surv Ophthalmol 1996; 40:491–499. 3. Sippel KC, Jain S, Azar DT. Monovision achieved with excimer laser refractive surgery. Int Ophthalmol Clin 2001; 41:91–101. 4. Schor C, Erickson P. Patterns of binocular suppression and accommodation in monovision. Am J Optom Physiol Opt 1988; 65:853–861. 5. Schor C, Landsman L, Erickson P. Ocular dominance and the interocular suppression of blur in monovision. Am J Optom Physiol Opt 1987; 64:723–730. 6. Fonda G. Presbyopia corrected with single vision spectacles or corneal lenses in preference to bifocal corneal lenses. Trans Ophthalmol Soc Aust 1966; 25:78–80. 7. Chang MA, Kloek CE, Zafar S, Jain S, Azar DT. Analysis of strict monovision and mini- monovision LASIK surgery in presbyopes. Arch Ophthalmol 2002. Submitted. 8. Maguen E, Nesburn AB, Salz JJ. Bilateral photorefractive keratectomy with intentional unilat- eral undercorrection in an aircraft pilot. J Cataract Refract Surg 1997; 23:294–296. 9. Wright KW, Guemes A, Kapadia MS, Wilson SE. Binocular function and patient satisfaction after monovision induced by myopic photorefractive keratectomy. J Cataract Refract Surg 1999; 25:177–182. 199Monovision Refractive Surgery for Presbyopia 10. Wilson SE, Klyce SD, McDonald MB, Liu JC, Kaufman HE. Changes in corneal topography after excimer laser photorefractive keratectomy for myopia. Ophthalmology 1991; 98: 1338–1347. 11. Moreira H, Garbus JJ, Fasano A, Lee M, Clapham TN, McDonnell PJ. Multifocal corneal topographic changes with excimer laser photorefractive keratectomy. Arch Ophthalmol 1992; 110:994–999. 12. Harris MG, Classe JG. Clinicolegal considerations of monovision. J Am Optom Assoc 1988; 5:491–495. 13. Emmes AB. A statistical study of clinical scores obtained in the Wirt steropsis test. Arch Am Acad Optom 1961; 38:398. 14. Collins MJ, Brown B, Verney SJ, Makras M, Bowman KJ. Peripheral visual acuity with monovision and other contact lens corrections for presbyopia. Optom Vis Sci 1989; 66: 370–374. 15. Hom MM. Monovision and LASIK. J Am Optom Assoc 1999; 70:117–122. 16. Bennett ES, Henry VA. Bifocal contact lenses. In: ES Bennett, VA Henry, eds. Clinical Manual of Contact Lenses. Philadelphia: Lippincott, 1994; 362–398. 17. McLendon JH, Burcham JL, Pheiffer CH. Presbyopic patterns and single vision contact lenses II. South J Optom 1968; 10:33–36. 18. Sanchez FJ. Monovision: which eye for near? Contact Lens Forum 1988; 13:57. 19. Lebow K, Goldberg J. Characteristics of binocular vision found for presbyopic patients wearing single vision contact lenses. J Am Optom Assoc 1975; 48:1116–1123. 20. Trevarthan CB. Two mechanisms of vision in primates. Psychol Forsch 1968; 31:299–348. 21. Rigel L. Which modality works best? When monovision makes sense. Rev Optometry 1998; 13:90. 22. Coren S, Kaplan CP. Patterns of ocular dominance. Am j Optom Arch Acad Optom 1973; 50:283–292. 23. Collins M, Goode A, Brown B. Distance visual acuity and monovision. Optom Vis Sci 1993; 70:723–728. 24. Erickson P, Schor C. Visual function with presbyopic contact lens correction. Optom Vis Sci 1990; 67:22–28. 25. Wirt SE. A new near-point stereopsis test. Optom Weekly 1947; 38:647–649. 26. Kirschen DG, Hung CC, Nakano TR. Comparison of suppression, stereoacuity, and interocular differences in visual acuity in monovision and Acuvue bifocal contact lenses. Optom Vis Sci 1999:832–837. 27. Pardhan S, Gilchrist J. The effect of monocular defocus on binocular contrast sensitivity. Ophthal Physiol Opt 1990; 10:33–36. 28. McGill EC, Erickson P. Sighting dominance and monovision distance binocular fusional ranges. J Am Optom Assoc 1991; 62:738–742. 29. Sheedy JE, Harris MG, Busby L, Chan E, Koga I. Monovision contact lens wear and occupa- tional task performance. Am J Optom Physiol Opt 1988; 65:14–18. 30. Du Toit R, Ferreira JT, Nel ZJ. Visual and nonvisual variables implicated in monovision wear. Optom Vis Sci 1998; 75:119–125. 31. Koetting RA. Stereopsis in presbyopes fitted with single vision contact lenses. Am J Optom Arch Am Acad Optom 1970; 47:557–561. 19 Multifocal Corneal Approach to Treat Presbyopia JANIE HO University of California at San Francisco, San Francisco, California, U.S.A. DIMITRI T. AZAR Corneal and Refractive Surgery Service, Massachusetts Eye and Ear Infirmary, Schepens Eye Research Institute, and Harvard Medical School, Boston, Massachusetts, U.S.A. A. INTRODUCTION Refractive surgery to correct presbyopia continues to be at an experimental stage despite a decade of investigation. The dilemma in presbyopia is the need for differing refractive powers of the optical media for near versus distance vision. In this chapter, we review several studies using a multifocal corneal approach to treating presbyopia. The techniques and results of the studies are presented, as well as a discussion of comparative conclusions and areas in need of further investigation. B. HISTORICAL/EXPERIMENTAL For several decades, refractive surgery has been successfully employed in treating patients with myopia and, later, hyperopia. Nevertheless, the presbyope continues to pose a chal- lenge to refractive surgeons, owing to the need for differing optical powers for near and distance vision. In the late 1980s, investigators observed a phenomenon wherein radial keratotomy patients achieved excellent uncorrected visual acuity at near and distance; however, this was inconsistent with the measured change in spherical equivalent (1,2). Further topographical analysis demonstrated an unintended multifocal lens effect of the 201 202 Ho and Azar cornea, enabling optimization of both near and distance vision through a range of optical zones. These studies offered the theoretical basis for refractive surgery to treat presbyopia using a multifocal corneal approach. The multifocal approach espouses the concept of pseudoaccomodation, or the ability to process multiple simultaneous images at the retina (3). Anschutz performed studies with photorefractive keratectomy (PRK) on polymethyl methacrylate (PMMA) lenses and porcine eyes to intentionally create multifocal corneal surfaces. A sectoral near zone as part of a concentric zone for distance was favored. He subsequently applied the models in clinical trials testing the effectiveness of PRK in treating myopia-presbyopia and hyperopia-presbyopia, described below (4). In addition, Moreira et al. investigated several modalities for achieving a multifocal surface (5). Four configurations of ablation were compared: monofocal ablation, two concentric ablations, two ablations with the smaller diameter ablation decentered inferiorly, and a single progres- sive ablation. The group concluded that a corneal surface with multiple refractive powers could be achieved in PMMA hemispheres and blocks, as well as, in rabbit corneas. They believed that the single progressive ablation would be the most effective, created with an iris diaphragm initially fully open to 6 mm and progressively closing until 3 mm, leaving a central zone with the preoperative refractive power (5). This technique would theoretically function in concert with pupillary miosis during near accommodation to decrease the percentage of light rays traversing the flattened zone of the cornea. Thus, degradation of the retinal image as a result of the multifocal lens effect may be reduced. C. TECHNIQUES In March 1999, Anschutz began human clinical trials of multifocal PRK to treat myopia- presbyopia. A 193-nm Aesculap-Meditec laser was used with an iris diaphragm to bifocally sculpt the cornea (4). The investigation involved two techniques for creating zones for near and distance vision: (1) an inferior pie-shaped sectoral near zone within a concentric distance zone and (2) a central near zone within a concentric distance zone. Both techniques involved an initial circular ablation of 2 or 3 D less than the myopic baseline refraction. For technique 1, this was followed by a second ablation to the full myopic correction using a sectoral template. Technique 2 used a central nonrotating template in a similar fashion. Figure 1 demonstrates the two techniques. In treating hyperopia-myopia, Anschutz investigated the technique of an inferior sectoral steepening of the cornea, to create active myopization for near vision (4). For the initial hyperopic PRK ablation, a spiral eye mask (or double-heart mask) was used along with a rotating spiral template to correct for the complete hyperopic refraction. Next, a nonrotating presbyopic template with an oval aperture was inserted for the second ablation, to create an inferior sectoral zone of an additional 2.0 to 3.0 D presbyopic correction (Fig. 2). The hyperopia-myopia study also included a subgroup of emmetropic presbyopes. Their ablations were performed with the hyperopic spiral mask and an oval template, to create an inferior zone of steepening (3.0 D) within a transition zone of 0.5 D (4). The configuration is similar to the inferior sectoral ablation for near vision shown in Figure 1. 203Multifocal Corneal Ablations Figure 1 Multifocal myopia-presbyopia PRK. Left, central near zone; right, sectoral near zone. (Adapted from Ref. 4.) In 1998, Vinciguerra et al. published their study involving zonal PRK for treating presbyopia. The group used a 193-nm Aesculap-Meditec Mel 60 excimer laser with a mask consisting of a mobile diaphragm formed by a blunt concave blade and a blunt convex blade (6). An inferior semilunar region was ablated for a presbyopic correction of 3.00 D. Within this region, the depth of cut was progressively reduced from the corneal center to periphery as the blades of the diaphragm progressively closed upon each other. Figure 2 Multifocal hyperopic-presbyopic PRK. (Adapted from Ref. 4.) [...]... Vis Sci 1984; 25 :77 6 77 8 21 The Scleral Expansion Procedure CHRIS B PHILLIPS and RICHARD W YEE Hermann Eye Center and University of Texas Health Science Center at Houston Medical School, Houston, Texas, U.S.A A INTRODUCTION Presbyopia, or age-related loss of accommodation, becomes noticeable between 40 and 45 years (1) It is one of the first signs of aging and results from the age-related decline... Ϫ0.54Ϯ0.25 17. 3Ϯ2.0 40. 17 28.58 1. 17 1.18 0.58Ϯ0.56 Ϫ0.11Ϯ0.22 20/26 Ϫ0. 47 0.45 20/59 Ϫ1.65Ϯ0.49a 16.4Ϯ1.5 Preop (nϭ6) 1 month (nϭ6) 27. 5Ϯ6.12 1.06Ϯ1.10 0.63Ϯ0.52 Ϫ0.12Ϯ0.24 20/26 Ϫ0.12Ϯ0.21a 20/26 Ϫ1.54Ϯ0.37a 17. 1Ϯ1.8 b a 3 months (nϭ6) Nonoperated eye Significant difference between the preop and the follow-up measurements using paired t-test (pՅ 0.05) SEϭspherical equivalent c Both distance and near... transient ghosting, decentration 20/30 Post-op near VA 206 Ho and Azar Multifocal Corneal Ablations 2 07 The Bauerberg LASIK study for hyperopia- presbyopia involved 16 eyes of 8 patients (8 eyes with centered ablation and 8 eyes with off-center ablation) with maximum followup of 22 months (7) Preoperative refractions ranged from ‫ 0.2ם‬to ‫ 0.6ם‬D At 12 months, the off-centered ablation eyes achieved uncorrected... Bailo G, Nizzola F, Ascari A, Epstein D Excimer laser photorefractive keratectomy for presbyopia: 24-month follow-up in three eyes J Refract Surg 1998; 14(1): 31– 37 7 Bauerberg JM Centered vs inferior off-center ablation to correct hyperopia and presbyopia J Refract Surg 1999; 15(1):66–69 20 Scleral Relaxation to Treat Presbyopia HIDEHARU FUKASAKU Fukasaku Eye Centre, Yokohama, Japan A INTRODUCTION Accommodation... 20/43 Ϫ0.85Ϯ0.16 20/142 Ϫ0.63Ϯ0.14 17. 2Ϯ2 .7 NPA (cm) SEb (diopters) Cylinder Distance VAc 20.83Ϯ5.19 0.81Ϯ1.13 0.63Ϯ0.44 Ϫ0.11Ϯ0.16 20/26 Ϫ0.03Ϯ0.07a 20/21 Ϫ1.95Ϯ1.05 16.2Ϯ0.84 1 month (nϭ6) 20.83Ϯ6.31 1.13Ϯ1.2 0.58Ϯ0.5 Ϫ0.14Ϯ0.19 20/28 Ϫ0.06Ϯ0.07a 20/23 Ϫ2. 67 2.63 13.6Ϯ1.14 a 3 months (nϭ6) 24. 67 5.69 0 .75 Ϯ0.5 0Ϯ0 Ϫ0.06Ϯ0.1 20/23 Ϫ0.03Ϯ0.06a 20/21 Ϫ0. 67 1.66 14Ϯ1 .73 a 6 months (nϭ3) 69Ϯ1.26 1.08Ϯ1.15... Coherent/Schwind Keratom 2 excimer laser with an 8.2-mm-diameter, 16 0- m-thickness corneal flap (7) Ablation depth was calculated by adding 10% to the preoperative spherical equivalent A centrally located ablation was tested as well as an inferiorly decentered ablation (by 1 mm) D RESULTS The myopia -presbyopia PRK study by Anschutz involved 46 eyes of 23 patients with follow-up of 2 1⁄2 to 3 years (4) The preoperative... consecutive nonmyopic patients who underwent scleral expansion using a complete encircling band ( 17) The band was passed through four separate scleral belt loops located at the 12, 3, 6, and 9 o’clock cardinal positions (Fig 3) ( 17) The bands were then ultrasonically fused together at the 1:30, 4:30, 7: 30, and 10:30 o’clock positions (Fig 4) All six patients demonstrated a marked improvement in near... safe, effective, and well accepted by patients Likewise, ACS-SEP promises to become another treatment modality for glaucoma, and we are working on improving its predictability REFERENCES 1 von Helmholtz HL Physiological Optics New York: Dover Press, 1962: 143– 172 , 375 –415 2 Fincham EF The mechanism of accommodation Br J Ophthalmol 19 37; 8(suppl):5–80 Scleral Relaxation to Treat Presbyopia 2 17 3 Schachar... Schachar RA Histology of the ciliary muscle-zonular connection Ann Ophthalmol 1996; 28(2) :70 79 4 Neider MW, Crawford K, Kaufman PL In vivo videography of the rhesus monkey accommodative apparatus Arch Ophthalmol 1990; 69:108 5 Thornton SP, Shear NA Surgery for Hyperopia and Presbyopia Baltimore: Williams & Wilkins, 19 97: 33–36 6 Fukasaku H Surgical Reversal of Presbyopia Highlights of the ’98 ASCRS meeting... possible surgical correction for presbyopia If the space between the lens equator and the ciliary body can be expanded, then the length of pull of the ciliary muscle/zonule apparatus should increase and accommodative tone will be restored Thornton (5) has suggested anterior ciliary sclerotomy (ACS) as a method to safely and effectively expand the globe over the ciliary body and uncrowd the lens (Fig 5) . laser-assisted in situ keratomileusis (LASIK) has also been employed to treat hyperopia- presbyopia. Bauerberg used a 193-nm Coherent/Schwind Keratom 2 exci- mer laser with an 8.2-mm-diameter, 16 0- m-thickness. acuity with monovision and other contact lens corrections for presbyopia. Optom Vis Sci 1989; 66: 370 – 374 . 15. Hom MM. Monovision and LASIK. J Am Optom Assoc 1999; 70 :1 17 122. 16. Bennett ES,. our 97 LASIK patients, 69 (71 .1%) had uncrossed monovision, and 28 (28.9%) had crossed monovision. The average age was 51 .7 ע 0.5 years for patients with uncrossed monovision and 49 .7 ע 0 .7 years