Hyperopia and presbyopia - part 10 doc

296 Glazer and Azar Table 2 Complications of LASIK for Correction of Spherical Primary Hyperopia Mean Loss of best No. of follow-up Technique and corrected visual Study Year eyes (months) microkeratome used Complications acuity (BCVA) (continued) Suarez (25) Ditzen (26) Goker (27) Knorz (28) Esqucnazi (29) Lindstrom (30) 1996 1998 1998 1998 1999 1999 154 43 54 23 100 46 3 12 19 12 12 6 Coherent/Schwind Keratom II Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter MEL 60 Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter Keracor 116 Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter Keracor 117 Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter Keracor 117CT Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter VISX STAR S2 Excimer Laser Hansatome 9.5-mm flap diameter • 1.3% corneal ectasia • Epithelial invasion of the interface • Traumatic flap displacement • Bilateral haze • 15% epithelial ingrowth • 2.3% haze • 7.5% scars • 4.7% vertical decentration • 2.3% central island • 4.7% free cap • 11.6% flap dislocation • 11.6% flap folds • 31.4% epithelial ingrowth • 13% regressed/under- corrected • 9.3% glare at 9 months • 3.7% transient diplopia that resolved entirely • 1.8% irregular flap cut • 1.8% decentration • 3.7% irregular astigmatism • No significant complications noted • 6% epithelial ingrowth into the interface • 4% scars on nasal side • 2% ablation decentration • 2% transient diplopia • 5% flap folds • 6.5% transient epithelial defect • 4.3% diffuse lamellar keratitis • 2% lost 1 line • 1.3% lost 2 lines • 9% lost 1 line • 4.7% lost 3 lines • 5.6% lost 2 lines • 63% of low hyperopes lost 1 line • 50% of high hyperopes lost 1 line • 6% lost 1 line at 1 year follow-up • 6% lost 2 lines at 1 year follow-up • 5% lost 2 lines at 2 year follow-up • 11% lost 1 line • 2.2% lost 2 lines 297Complications of Refractive Surgery Table 2 Continued No. Mean Technique and Loss of best of follow-up microkeratome corrected visual Study Year eyes (months) used Complications acuity (BCVA) Arbelaez (31) Zadok (32) Reviglio (33) Argento (34) El-Agha (9) Choi (35) 1999 2000 2000 2000 2000 2001 192 72 50 147 26 32 12 6 6 12 12 6 Keracor 177C Excimer Laser Automated Corneal Shaper 9.0-mm flap diameter Nidek EC-5000 Excimer Laser Automated Corneal Shaper 8.5-mm flap diameter Lasersight 200 Excimer Laser with 9.0 software Automated Corneal Shaper 9.0- to 9.5-mm flap diameter Keracor 117C Excimer Laser Hansatome 5.9-mm optical zone diameter, flap diameter not reported VISX STAR S2 Excimer Laser Hansatome 9.5-mm flap diameter VISX S2 Smoothscan Excimer Laser Hansatome 9.5-mm flap diameter • 4.3% epithelial cells in the interface • 2.2% haze • 2.2% mild irreg astig • 0.6% had a free cap • 0.6% sterile keratitis, (Note: Complication rates combine the 192 spherical hyperopes with the 164 toric hyperopes.) • No significant complications noted • 2% epithelial ingrowth in the would edges associated with free caps, not requiring surgical removal • 8.2% transient epithelial ulcer • 4.5% stromal infiltrates • No significant complications noted • No significant complications noted • 13% of high hyperopes lost 2 lines or more • 1.4% lost 2 lines or more • No eyes lost BCVA • Less than 5.8% lost 1 line • 19% lost 1 line • 7.7% lost 2 lines • 25% lost 1 line • 9% lost 2 lines a. Flap Complications Intraoperative complications include free flaps, incomplete flaps, buttonholes, small flaps, and thin flaps. Free flaps, thin flaps, or incomplete flaps are more likely to occur in patients with flat (Ͻ41.00-D) and large (Ͼ11.5-mm) corneas. Unusually steep (Ͼ48.00-D) and small (Ͻ11.5-mm) corneas are more conducive to buttonholes or large flaps. The larger ablation areas necessary for H-LASIK require larger flaps. Extra care must be taken with the larger flaps because a large flap may be more prone to wrinkles 298 Glazer and Azar or misalignment, which may lead to irregular astigmatism. When pannus exists, a large flap may cause bleeding, which must be cleared from the bed prior to ablation. Appropriate preoperative examinations can help one identify and discourage patients at greater risk for flap complications. Preplaced surgical landmarks that straddle the flap edge will help with accurate repositioning of the flap in the operative and postoperative period. In addition, the newer microkeratomes and suction rings create fewer flap complica- tions. b. Epithelial Ingrowth To achieve successful H-LASIK results, the diameter of the corneal flap must be large enough. Epithelial ingrowth can result from laser energy to the periphery of the flap, or it may occur secondary to wound edge instability with migration of epithelial cells under the flap (Fig. 3). Epithelial ingrowth can progress to involve the visual axis, creating irregular astigmatism and even melting of the overlying flap (13,36). If epithelial cells under the flap progress toward the visual axis or induce stromal melting, the flap should be lifted, the stromal bed and flap undersurface should be thor- oughly irrigated and scraped, and the flap should then be repositioned (37). With larger flaps of 9 to 10 mm, the risk of epithelial ingrowth is greatly reduced, most likely because this avoids ablation of epithelium beyond the edge of the flap (38). Other measures one may take to prevent epithelial ingrowth include using dedicated instru- ments exclusively for interface manipulation, so that these instruments do not come in contact with the surrounding epithelium. Also, one should be careful to avoid flap folds, as these may provide a conduit for cell infiltration (13). c. Decentration Decentration or small optical zones may lead to irregular astigmatism, causing loss of BCVA, glare, monocular diplopia or halos, and halo effects. The same principles of de- centration described above for PRK apply here. For example, whether with PRK or LASIK, a larger optical zone is more forgiving of a slight decentration. More sophisticated LASIK ablation profiles may also diminish the risk of decentration: a more gradual transition zone between ablated and unablated tissue helps minimize epithelial and stromal regenera- tion, with its subsequent regression. Figure 3 Epithelial ingrowth after LASIK. (A) Stable epithelial ingrowth at the LASIK interface. (B) Retroillumination used to view the same area of epithelial ingrowth. (From Ref. 13.) 299Complications of Refractive Surgery Figure 4 Diffuse lamellar keratitis following LASIK. (A) Diffuse lamellar keratitis 2 days after LASIK. (B) Diffuse lamellar keratitis, 5 days after LASIK, with central coalescence, scarring, and stromal melt. (From Ref. 13.) d. Diffuse Lamellar Keratitis Although diffuse lamellar keratitis (DLK) is a recently described syndrome, not yet docu- mented after H-LASIK, it has been reported in approximately 0.2 to 3.2% of cases of myopic LASIK (13,39–42). DLK is characterized by a proliferation of inflammatory cells at the LASIK interface (Fig. 4). It can lead to loss of BCVA due to irregular astigmatism and may also cause stromal corneal melting with induced hyperopia or hyperopic astigma- tism. The cause of DLK is still unclear; thus, prevention remains a challenge. When present, however, DLK must be treated immediately with hourly topical prednisolone actate 1% and broad-spectrum topical antibiotic coverage. It has been observed that if the DLK is not resolved by the fifth postoperative day, there is typically central coalescence of the inflammatory cells, which may lead to central stromal melting and scarring. Thus, if inflammation progresses despite the steroid/antibiotic treatment, the flap should be lifted, scraped, and irrigated by the fourth postoperative day at the latest (13). The use of topical intrastromal steroid during LASIK has been proposed as a way of reducing the incidence and severity of DLK (43). e. Late Flap Dislocation One rare, potential H-LASIK complication is traumatic flap dislocation, occasionally seen months or years after LASIK (44,45). One might expect a slightly greater risk of flap dislocation in H-LASIK because the flap tends to be wider than that created for myopic LASIK. For this reason, it would be wise to avoid performing H-LASIK on high-risk patients, such as boxers. One should also encourage patients to wear safety glasses when engaging in high-risk sports activities after H-LASIK. f. Corneal Ectasia Corneal ectasia is a rare complication. For example, in one of the largest studies of H- LASIK, Suarez et al. performed LASIK on 154 eyes of patients with simple hyperopia of between ם1.00 and ם8.50 D with astigmatism of less than 0.75 D. Suarez et al. had only two cases of postoperative corneal ectasia, both occurring in patients with high levels of hyperopia. Keratectasia is most likely due to the mechanical uncoupling of the posterior 300 Glazer and Azar from the anterior stroma, with subsequent weakness of the cornea. Denervation of the flap or subclinical epithelial ingrowth may exacerbate this mechanical uncoupling. Other fac- tors that may predispose to corneal ectasia include excessive ablation with less than 250 ␮m of residual stromal bed, a thicker than normal flap with consequent ablation at a deeper than planned level, and irregular corneal thickness (46). One can attempt to prevent corneal ectasia with preoperative pachymetry maps to detect borderline cases. One must also identify patients with keratoconus and prevent them from undergoing H-LASIK because they, of course, would be at great risk for postoperative corneal ectasia. g. Loss of Best Corrected Visual Acuity Loss of BCVA is more likely to occur after H-LASIK performed on high hyperopes. Choi notes that 50% of eyes with attempted corrections greater than5DlosttwolinesofBCVA. These high rates of loss of BCVA in eyes with high hyperopia may be due to induced irregular astigmatism (27–28,30–31,35). Irregular astigmatism can result from poor cen- tration of the ablation. Even small levels of decentration can cause irregular astigmatism, leading to degraded vision quality or monocular diplopia. Knorz performed a pilot study on eyes with hyperopia and hyperopic astigmatism. In eyes with ם5.1Dtoם10 D of hyperopia (15 eyes), 53% had lost one line at 1 month, and 20% had lost two or more lines of BCVA at 1 month. For 12-month follow-up, 6 eyes were available, and 50% of these had lost one line while none had lost two or more lines of BCVA. No significant intraoperative or postoperative complications were noted. However, it was felt that the loss of acuity was due to image degradation by significant optical aberrations caused by the new corneal surface. Knorz concluded his study by suggesting that LASIK should not be used for hyperopia Ͼם5 D.(28) Studies of myopic LASIK procedures have identified other causes of loss of BCVA to include flap folds, epithelial defects, lamellar keratitis, and epithelial ingrowth (30). 3. Conclusion As we gather more experience with hyperopic PRK and LASIK, we can achieve higher rates of predictability and accuracy by creating nomograms adjusted for preoperative re- fraction, keratometry, and age. Also, more sophisticated equipment can decrease complica- tion rates for both PRK and LASIK: more sophisticated ablation profiles and better eye- tracking systems can reduce decentrations. For LASIK, newer, larger microkeratomes that produce flap diameters of at least 9.0 mm should be used. C. COMPLICATIONS OF NONCONTACT LASER THERMAL KERATOPLASTY 1. Background Thermal keratoplasty (TK) was first performed in 1898 by the Dutch ophthalmologist Lendert Jan Lans in an attempt to treat astigmatism (47). Lans demonstrated that thermal energy, applied with a cautery, altered the structure of the corneal stromal collagen and changed the anterior corneal curvature. Unfortunately, using simple cauteries and probes, it was difficult to control the amount of energy applied, and TK resulted in unpredictable results and regression (48,49). Interest in TK was rekindled with the development of lasers that could heat the cornea in a more controlled manner. 301Complications of Refractive Surgery Figure 5 Slit-lamp photograph of a cornea immediately after treatment with noncontact holmium: YAG laser thermal keratoplasty. (From Ref. 55.) In 1990, Seiler first described laser thermal keratoplasty (LTK), which utilizes the holmium:yttrium aluminum garnet (Ho:YAG) laser to correct hyperopia (50). Ho:YAG LTK avoids damage to the corneal epithelium by delivering infrared radiation to the mid- stroma. LTK changes the anterior corneal curvature because corneal collagen shrinks by 30 to 45% of its original length at temperatures of 55 to 60ЊC (51). Local, peripheral flattening causes central steepening, which corrects for hyperopia. Initially, both contact and noncontact LTK were performed. However, contact LTK, performed by directly appla- nating the cornea with a probe, tended to cause irregular astigmatism, regression and undercorrection; this form of LTK was withdrawn from U.S. Food and Drug Administra- tion (FDA) trials (52–54). Noncontact LTK, on the other hand, has been approved by the FDA. It is traditionally performed by projecting one to three concentric rings of eight laser spots each onto the cornea through a slit lamp–mounted, fiberoptic delivery system (Fig. 5). FDA phase IIA clinical trials with 2 years of follow-up showed the uncorrected visual acuity (UCVA) was improved by one or more lines in 19 (73%) of 26 treated eyes (55). 2. Complications While a variety of complications may occur following LTK, the most common is regression of effect (Table 3). Short-term complications include discomfort immediately after LTK treatment or for 1 to 3 days post-LTK; some patients complain of mild pain (18–20%), tearing (41–43%), mild photophobia (33–41%), mild foreign-body sensation (41–54%), and other mild discomfort (29%). These side effects of laser-induced epithelial injury typically resolve within 3 days of treatment (56,58). Corneal opacities and epithelial haze and staining are common in the first week post-LTK treatment. However, by 2 years after treatment, corneal opacities at the treated sites and golden-brown intraepithelial deposits (presumably iron deposits) in or adjacent to inferior treatment spots are typically the only evidence of change to the cornea (56). Long-term damage to the central cornea has not been reported as a complication. Clearly, the principal limitation of noncontact LTK is regression. Reported rates of regression vary from 27 to 45% (55–58). In one study, 70.1% had an UCVA of 20/20 at 302 Glazer and Azar Table 3 Complications of Noncontact LTK for Correction of Spherical, Primary Hyperopia Mean Loss of best No. of follow-up Technique corrected visual Study Year eyes (months) used Complications acuity (BCVA) Koch (56) Koch (55) Alio (57) Nano (58) Vinciguerra (59) 1996 1997 1997 1998 1998 17 28 57 182 16 24 24 15 12 12 Sunrise Technologies delivery system 1 ring of 8 spots per ring Sunrise Technologies delivery system 1–2 rings of 8 spots per ring Sunrise Technologies delivery system 2–3 rings of 8 spots per ring Sunrise Technologies delivery system 1–3 rings of 8 spots per ring Sunrise Technologies delivery system 3 rings of 8 spots per ring • 27% had 0.5 to 1.0 D of induced astigmatism • 27% regression • 29% regression in the 1-ring group • 31.5% had total regression • 45% regression • 0.55% decentered treatment ring • 0.55% with 1 D of induced astigmatism • 25% complained of halos or ghost images at 12-month follow-up • 6% lost 2 lines of BCVA • 7% lost 1 line of spectacle- corrected near visual acuity • No loss of BCVA • No loss of BCVA • No loss of BCVA 3 months, but only 50.8% maintained this level at 15 months. In fact, by 15 months, only 57.8% were within ע1.00 D of the intended refraction (57). In addition to regression of effect, astigmatism may occur as a result of noncontact LTK. 3. Etiology of Regression Some researchers feel that regression is inherent to the current technique for LTK. The Ho:YAG LTK technique delivers pulses of energy to the cornea. The pulses themselves may trigger a mixed shrinkage/relaxation pattern. For example, if the energy pulses are too low, an insufficient amount of collagen shrinkage is achieved, and the initial refractive change may gradually be lost. On the other hand, if the laser heats the collagen fibrils to 65 to 70ЊC, collagen relaxation occurs. Regression after noncontact LTK is more common in younger patients and patients with thicker central corneas (57). Regression may be due to the elasticity of Bowman’s membrane and stromal collagen in younger patients, which causes the cornea to return to its previous shape. Similarly, thicker corneas may be more likely to resume their previous configuration. At least in rabbit models, noncontact LTK provokes procollagen synthesis by fibroblastic keratocytes, causing stromal remodeling which can produce irregularities in the anterior corneal surface leading to epithelial hyperplasia. This in turn, results in an 303Complications of Refractive Surgery altered corneal curvature (60). While the precise wound healing response to noncontact LTK in humans is not known, it is possible that both regression and astigmatism may result from a similar response. 4. Prevention Investigators are speaking optimistically about a new continuous-wave diode laser that can change the shape of the cornea without the peaks and troughs of the pulsed Ho:YAG laser (61,62). The continuous-wave diode laser is expected to avoid tissue overheating, thereby improving long-term refractive stability. In addition, FDA trials are under way on a device that uses radiofrequency energy to the peripheral cornea; this may produce more controlled shrinkage of collagen lamellae (63). 5. Conclusion One point to remember is that while regression and, less frequently, astigmatism may result from noncontact LTK, it is rare for patients to lose even one line of BCVA. No eyes have been reported to have lost two or more lines of BCVA from noncontact LTK (55–58). For risk-averse low hyperopes (ם0.75 to ם2.50 D), noncontact LTK is a proce- dure to consider because it causes very few BCVA-threatening complications. D. COMPLICATIONS OF PHAKIC INTRAOCULAR LENSES AND CLEAR LENS EXTRACTIONS WITH INTRAOCULAR LENS IMPLANTS 1. Background While most types of refractive surgeries alter the cornea, the refractive power of the eye can also be changed by implanting an intraocular lens (IOL) with or without extraction of the crystalline lens. Barraquer implanted the first phakic intraocular lens in the 1950s (64). Unfortunately, many of these anterior chamber lenses were poorly finished and had sharp edges. After Barraquer had implanted almost 500 lenses, significant complications such as corneal edema occurred, and over 300 of the lenses had to be removed (65). After this experience, interest in phakic IOLs waned until labs were better able to guarantee the quality of IOLs. Intraocular lenses being made today are of much better quality than those used in the 1950s. A recent study used a scanning electron microscope to analyze the surface quality of new-generation phakic IOLs; the study showed that these lenses did not have any defects that would contraindicate their use as phakic IOLs (66). This study examined the three major types of lenses currently used as phakic IOLs: anterior chamber lenses (currently used only in myopic eyes), iris-fixated anterior chamber lenses, and posterior chamber lenses. 2. Complications Even when perfectly constructed IOLs with smooth surfaces are placed, there is still a risk of progressive corneal endothelial cell loss secondary to phakic IOLs (67–71). Other 304 Glazer and Azar Table 4 Complications of Phakic Intraocular Lens Implantation for Correction of Hyperopia Mean Loss of best No. of follow-up IOL corrected visual Study Year eyes (months) Implanted Complications acuity (BCVA) Davidorf (76) Rosen (77) Fechner (78) Pesando (79) Sanders (80) Pershin (81) 1998 1998 1998 1999 1999 2000 24 9 69 15 10 33 18 6 120 18 6 12 Staar ICL Staar ICL Iris-Claw IOL Staar ICL Staar ICL Storz Phacoprofile IOL • 12.5% pupillary block glaucoma • 8% IOL decentration of more than 1 mm • 12.5% underwent removal of their IOL • 11% pupillary block glaucoma, requiring surgical iridectomy and removal of IOL • 1.4% lens dislocation secondary to postoperative trauma • 3% uveitis, corneal edema, and glaucoma • 13% pupillary block glaucoma • 6.7% anterior • No complications • 6% anterior subcapsular cataract • 3% lens replacement was required due to calculation error • 9% pigment dispersion without IOP elevation • 4% lost 3 lines • 22% lost 1 line • No loss of BCVA • 6.7% lost 2 lines • No loss of BCVA • No loss of BCVA potential complications of IOL implantation include cataract formation, pupillary-block glaucoma, endophthalmitis, and retinal detachments (Table 4) (72–75). Currently the most popular phakic IOL for the treatment of hyperopia is the Collamer Staar Posterior Chamber IOL, also called the implantable contact lens (ICL) (Fig. 6). A recent phase I trial of silicone plate posterior chamber lenses, implanted in hyperopes, reported that 100% of patients had 20/40 or better UCVA, and 70% had 20/20 or better UCVA (80). In one study of hyperopes with phakic IOLs 1 year after implantation, opacities in the area of lens contact with the capsule developed in two eyes (6%). Pigment dispersion occurred in three eyes (9%), but without intraocular pressure elevation. One eye (3%) required a lens replacement because of a calculation error (81). Another study reported 305Complications of Refractive Surgery Figure 6 The STAAR Collamer posterior chamber phakic intraocular lens implant. (From Ref. 79.) an anterior subcapsular cataract developing immediately after surgery in one eye (6.7%), causing a loss of two lines of BCVA (79). Because hyperopic eyes tend to be shorter, they are more prone to pupillary block after implantation of posterior chamber lenses. One study using the Staar Collamer Im- plantable Contact Lens (ICL) reported 2 of 15 eyes (13%) developing a severe pupillary block despite two iridotomies that had been performed 2 weeks prior to surgery. The increased intraocular pressures due to the pupillary block necessitated removal of the implants (79). Another study of the Staar ICL reported a 12.5% incidence of postoperative pupillary block. In addition, IOL decentration of more than 1 mm occurred in 2 of the 24 eyes (76). Sight-threatening complications such as endophthalmitis have been reported to occur in phakic IOL procedures for myopia and could theoretically occur for hyperopic phakic IOL implantation procedures as well (75). Occasionally, silicone plate phakic intraocular lenses need to be removed due to incorrect sizing of the lens and poor fixation within the sulcus (82). Retinal detachments after phakic IOL implantation have been reported in 4.8% of myopic eyes (74). This complication has not yet been reported in hyperopic eyes. Iris-fixated phakic IOLs for the correction of high hyperopia can be associated with serious complications such as corneal decompensation and glaucoma (Fig. 7) (78). Other risks include cataract formation and glaucoma (pupillary block glaucoma, pigmentary glaucoma, narrow-angle glaucoma, and malignant glaucoma) (76). Peripheral iridotomies can treat or prevent pupillary-block glaucoma. Shallow anterior chambers should be a contraindication to performing an ICL because of the risk of narrow-angle glaucoma. Lens decentration may also occur. 3. Clear Lens Extraction with IOL Implantation Clear lens extraction (CLE) with IOL placement has been studied as a surgical correction of hyperopia. Some of the disadvantages associated with this procedure as a treatment for myopia are not as a relevant when it is considered as a hyperopic treatment. For example, [...]... examinations, 98 hyperopia, 7, 95 105 thermokeratoplasty procedures, 95–96 mechanism, 96–97 patient selection, 97–98 performing, 98 100 postoperative care, 100 procedure, 97–98 radiofrequency-based, 96 for reducing hyperopia, 255 United States multicenter clinical trial, 100 105 corneal topography, 102 efficacy, 101 patients and methods, 100 results, 101 105 safety, 104 105 slit lamp, 104 stability, 103 Index... Intracorneal lens, hyperopia, 8 Intracorneal ring (ICR), myopia, 7 Intracorneal segments (ICS) central steepening, 111 complications, 307–309 hyperopia, 107 –113 complications, 111–113 contraindications, 109 indications, 109 postoperative care, 110 preoperative preparation, 109 surgical technique, 109 visual outcomes, 110 111 postoperative, 108 Intraocular lens (IOL) accommodating and adjustable results,... 1991; 7:282–285 70 Perez-Santonja JJ, Iradier MT, Sanz-Iglesias L, Serrano JM, Zato MA Endothelial changes in phakic eyes with anterior chamber intraocular lenses to correct high myopia J Cataract Refract Surg 1996; 22 :101 7 102 2 71 Menezo JL, Cisneros AL, Rodriguez-Salvador V Endothelial study of iris-claw phakic lens: four-year follow-up J Cataract Refract Surg 1998; 24 :103 9 104 9 72 Trindade F, Pereira... Photorefractive keratectomy for hyperopia: six-month results in 45 eyes Ophthalmology 1997; 104 :1952–1958 4 Jackson WB, Casson E, Hodge WG, Mintsioulis G, Agapitos PJ Laser vision correction for low hyperopia An 18-month assessment of safety and efficacy Ophthalmology 1998; 105 : 1727–1738 5 Williams DK One year results of laser vision correction for low to moderate hyperopia Ophthalmology 2000; 107 :72–75 6 Marshall... the correction of hyperopia and presbyopia In order to broaden the scope of patient acceptance, current and investigative techniques will continue to develop in the future as the clinicians and researchers strive for greater efficacy, safety, and visual quality Each area within refractive surgery will bring improvements specific unto itself A HYPEROPIA 1 LASIK and PRK Hyperopic laser-assisted in situ... 164 Erbium:yttrium-aluminum-garnet (YAG) laser, 10 sclera incision, slit-lamp, 12 Excimer laser surgery, hyperopia, 178 Expansion band, 221, 223 Eye aberrations, 31–32 exercises, scleral expansion procedures, 231–232 increase optical power, 30–31 models, 269–275 implementation issues, 274 predictions using, 274 pros and cons, 273–274 requirements, 269 Far point, 17–18 Fechner iris-claw intraocular... greater numbers of patients are experiencing the increased freedom that comes with treating hyperopia and presbyopia The future is very bright for the surgical correction of hyperopia and presbyopia References 1 Uuzoto H, Guyton DL Centering corneal surgical procedures Am J Ophthalmol 1987; 103 : 264–275 2 Pande M, Hillman JS Optical zone centration in keratorefractive surgery Entrance pupil center,... LASIK for hyperopia and hyperopic astigmatism—results of a pilot study Semin Ophthalmol 1998; 13(2):83–87 29 Esquenazi S, Mendoza A Two year follow-up of last in situ keratomileusis for hyperopia J Refract Surg 1999; 15:648–652 30 Lindstrom RL, Hardten DR, Houtman DM, Witte B, Preschel N, Chu YR, Samuelson TW, Linebarger EJ Six-month results of hyperopic and astigmatic LASIK in eyes with primary and secondary... lens (IOL) finite-element computer simulation, 10 Accommodative mechanism, debate, 34 Accommodative tone, 211 Accommodative triad, 31 ACS (See Anterior ciliary sclerotomy (ACS)) ACS-SEP, 214 Age-related cataract (ARC), 58 Aging crystalline lens, 55–63 size and shape, 56–57 oxidative stress, 58–59 presbyopia, 57–58 refractive error, 57 zonule, 60 AIS, 223–224, 232 ALK, 5, 164 Alternating-vision bifocal... Menefee R, Berry M Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty: U.S Phase IIA clinical study with 2-year followup Ophthalmology 1997; 104 :1938–1947 56 Koch DD, Abarca A, Villarreal R, Menefee R, Kohnen T, Vassiliadids A, Berry M Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty: clinical study with 2-year follow-up Ophthalmology 1996; 103 :731–740 57 . Surg 1996; 22 :101 7 102 2. 71. Menezo JL, Cisneros AL, Rodriguez-Salvador V. Endothelial study of iris-claw phakic lens: four-year follow-up. J Cataract Refract Surg 1998; 24 :103 9 104 9. 72. Trindade. with hyperopia and hyperopic astigmatism. In eyes with ם5.1Dto 10 D of hyperopia (15 eyes), 53% had lost one line at 1 month, and 20% had lost two or more lines of BCVA at 1 month. For 12-month. small flaps, and thin flaps. Free flaps, thin flaps, or incomplete flaps are more likely to occur in patients with flat (Ͻ41.00-D) and large (Ͼ11.5-mm) corneas. Unusually steep (Ͼ48.00-D) and small