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Approaches to Ametropia in Cataract Surgery
DISCUSSION SECTION
Approaches to Ametropia in Cataract Surgery Edited by MICHAEL LAVIN
In recent years cataract surgical techniques such as phacoemulsification cataract extraction with implant of a folding lens through a small incision, have resulted in cataract procedures becoming more reproducible, predictable and with a lower risk of serious complications. Cataract surgery is being offered to patients with less advanced cataracts than previously, and may also be combined with refractive surgical procedures such as astigmatic keratotomies. Indeed, there is widespread acceptance of the refractive goals of cataract surgery, seeking not only to remove media opacity, but also to achieve the most suitable final refractive state for the patient. Patients who have both cataract and ametropia may present specific management problems, and we asked a number of leading cataract surgeons with experience in this area for their comments. We asked our contributors to address the following issues in their discussion of the management of ametropia in cataract surgery. 1. What is your target post-operative refraction in patients with: (a) bilateral cataract and high myopia (18 dioptres); (b) unilateral cataract and bilateral high myopia; (c) bilateral cataract and bilateral high hypermetropia (>+8 dioptre); (d) unilateral cataract and bilateral high hypermetropia?
2. Do you modify your standard technique of biometry and intra-ocular lens implant power calculation for these cases, and if so how? 3. What lens powers would you routinely implant? If the desired lens power (e.g. 37 D for hypermetropia-5 D for myopia) is not available, what would you do? 4. What would your desired post-operative refraction be in each case? 5. How would you manage the fellow eye? In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral
cataract, how would you advise the patient and what would you recommend: -for a 25-year-old with no other ocular disease; -for a 55-year-old with no other ocular disease? Would you consider refractive surgery to the noncataractous eye subsequently? How do you think we can improve the care we currently give patients? S.P.B. PERCIVAL
Mr Piers Percival is based at Scarborough Hospital, in England, where he has developed a well-deserved reputation in cataract and refractive surgery. 1. (a) Target post-operative refraction in patients with bilateral cataract and high myopia
My target is for 0 to -2 D myopia postoperatively, preferring to operate on the non-dominant eye first. The dominant eye is then operated on later aiming to emmetropia of the first eye becoming slightly myopic or aiming for low myopia according to the patient's wish. I use SRK II formula and do not modify my standard technique biometry except that if the result of the first eye has appeared inaccurate calculations are repeated before the second eye is operated on. The extent of the cataract will vary with different individuals and for those with only moderate opacities it is important that the patient is informed of and understands the risks. I explain that there is 5% risk of losing the sight (though not necessarily irreparably) from retinal detachment or vitreous haemorrhage during the first 2 years after surgery and that the risk of retinal detachment rises to 8% following posterior capsulotomy and that this is found to be necessary in about a third of all high myopes operated on. One should guard particularly against family or past history of retinal detachment and if examination under full mydriasis reveals evidence of peripheral retinal degeneration, these factors being relative contraindications of cataract sure gery. One should also beware of patients occupation
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if this involves their unaided magnified VISIOn. Jewellers and clocksmiths may be dependent on this and may not thank the surgeon for curing their myopia. 1. (b) Unilateral cataract and bilateral high myopia
I would operate as above provided the patient understands and is informed of the risks. Provided the patient wishes for surgery, a history of partial amblyopia or known macular changes should not be a contraindication, for the sight will almost certainly be better once the cataract and high myopia have been treated. These unilateral cataracts are usually relatively blind eyes so there is little to lose and much to gain. For ametropias over 8 dioptres the improvement in visual field and pleasure in discarding thick glasses with their incapacitating optical defects generally outweighs the advantages of binocular vision and most patients are extremely grateful for the result. For the fellow eye a contact lens may maintain binocular vision but for those who wish to discard the contact lens or are intolerant to contact lenses, there is then a positive indication for clear lens extraction provided the patient asks for this and understands the risks. I do not recommend in these situations any alternative form of refractive surgery. 1. (c) Bilateral cataract and bilateral high hypermetropia (>+8 dioptre)
I would plan consecutive surgery aiming for emmetropia.
implantation vary between plano and +30.0. A +37 D would require a special order from the factory. If the power of 5 D was unavailable for some reason I would implant a 6 or 7 D knowing that this would result in an acceptable low myopic refraction. Any result between 0 and 2.5 D, postoperatively is acceptable (inaccuracies do happen for the first eye) and the aim should be for greater accuracy with the fellow dominant eye at a later date. 3. Bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract
I do not find any difficulty in advising bilateral cataract surgery for a 25-year-old with no other ocular disease who has a cataract already in one eye and wishes for refractive surgery for high ametropia. The treatment is the same as for a 55-year-old. Before a 25-year-old consents to surgery, however, it must be pointed out that the lens implant will be monofocal and that by having surgery the patient will lose the power of focusing (accommodation). For high myopes, one should recommend a single piece lens with loop span 13.5 mm and an optic diameter of 7 mm. The capsulorhexis diameter should be at least 6 mm (wider than usual) and the need for a wide optic implant for clear fundus examination postoperatively should override any surgeon preference for smaller incision surgery. All high myopes should have the retina examined with a slit lamp under extreme mydriasis within a few weeks of surgery for the presence of treatable retinal pathology. In my view there is no place at all for prophylactic retinal surgery, preoperatively. THOMAS NEUHANN
1. (d) Unilateral cataract and bilateral high hypermetropia
In general I would plan the same treatment and for the same reasons as in (2) above. The situation is slightly different in that the risk of vitreous haemorrhage and retinal detachment is negligible. However,. a history of amblyopia must be taken more seriously as this is generally much more denser in a hypermetrope; therefore if there is a history of amblyopia in the cataractous eye, surgery should be delayed until there are early lens changes in the fellow eye. 2. Biometry and intra-ocular lens implant powers
The lens powers which we have in stock for routine
Professor Neuhann is a gifted and energetic cataract surgeon, based in Munich, who regularly contributes new observations or innovations arising from his extensive surgical practice. 1. (a) Target post-operative refraction in patients with bilateral cataract and high myopia
In these patients it is important to first of all distinguish between those who have corrected their ametropia with contact lenses and those who have always worn glasses. Patients who have always worn glasses will generally be very reluctant to lose their ability to see well or even extremely well, including the magnifying effect, without glasses at very close up distances. Eur J Implant Ref Surg, Vol 6, June 1994
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In my experience they will therefore be happiest if left with a residual myopia of -3.0 D (±0.5). This enables them to follow their lifelong 'seeing habit' of near vision without glasses, while wearing corrective glasses for distance. With this refraction, glasses are usually absolutely no problem; a sizeable proportion of patients have even expressed discomfort with the thought of generally no longer wearing glasses postoperatively, since they themselves and their surroundings have been used to their appearance with glasses for such a long time. Others do not wear this distance correction for most of the time, since they feel their vision for most everyday purposes is so excellent that they do not feel a need for it except for special circumstances, e.g. driving, theatre, etc. On the other hand I have previously had high myopes severely complain postoperatively when their refraction was around emmetropia: although their uncorrected distance vision and their corrected near vision was excellent and greatly improved compared to preoperatively, they even called the situation 'worse than before because before I could read without glasses'. Thus, as a general rule, a residual refraction of -3.0 D will give the previously spectacle correct high myope the greatest comfort and satisfaction. For patients who have been generally contact lens corrected preoperatively, especially if they are adapted to the use of reading glasses and finally like their way of seeing, a residual refraction of -1.0 to -0.5 D, as I generally choose it for patients within the normal refractive range, will be most advantageous. It gives the patient a range of excellent uncorrected visual acuity between infinity and around one metre or even slightly below, thus covering most of our daily activities. For near vision the patient is used to additional correction.
1. (b) Unilateral cataract and bilateral high myopia
Generally the same principles as above apply. With satisfied contact lens wearers there are no problems: the criteria and arguments outlined above apply. Previous spectacle wearers are in a more difficult situation. I will generally offer them the available options, namely, the following. 1. Residual refraction of -3.0 in the operated eye and contact lens correction for the unoperated eye until this will have to be operated. One will generally propose a soft contact lens because unilateral hard contact lenses especially in this patient population are usually not tolerated. Any residual astigmatism can be spectacle corrected-especially since glasses will have to be prescribed anyway. If the Eur J Implant Ref Surg, Vol 6, June 1994
patient wishes I offer a preoperative trial of soft contact lens wear to give the patient a chance to judge whether this may be an option for him. 2. If contact lens wear is declined by the patient or if in the later postoperative course becomes intolerable, refractive lens surgery ('clear' lens exchange) is offered. It is clearly beyond the scope of this discussion to raise the entire controversy about this procedure; in any case on the basis of my experience I am convinced that the risklbenefit ratio ofthis approach justifies it in preference to the third and last option. 3. Correcting the operated eye to within 2.5 D of the refraction of the unoperated eye. This is also the sequence of my preferences when counselling the patient. 1. (c, d) Unilateral or bilateral cataract and bilateral high hypermetropia
By and large the same type of arguments applies, mutatis mutandis, to high hypermetropia. The only difference would be that there my preferred postoperative refraction would be -0.5 ±0.5 D for all types of patients. Also in high hypermetropia, refractive lens surgery in the unilateral cataract cases may be considered even more, since there does not appear to be a statistically increased long term postoperative retinal risk. 2. Biometry technique and intra-ocular lens implant power
The standard techniques of biometry are not modified, power-calculation takes the non-linearity in these extreme refractive ranges into consideration (e.g. SRK2, SKRT, Holladay and other theoretical formulas). What lens powers would you routinely implant?
I will implant the powers as indicated by the calculation. For all practical purposes there are no restrictions as to lens powers that can be manufactured. In a given case, I would have a lens custom manufactured. The age of the patient would modify my recommendations as to the desirable postoperative refraction only in one aspect: for a patient who can still accommodate with the fellow eye, I would like to have the operated eye -1.5 D from the refraction of the non-operated eye: this will minimize near aniseikonia sufficiently to enable binocularity with and
Discussion Section
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without a reading correction in place over the operhypermetropia but which maintains binated eye. Isometropia for distance in a unilaterally ocular vision. accommodating patient will in most cases cause (ii) Operate on the cataract and attempt to reach considerable binocular problems for near, with or emmetropia with the intention of performing the without unilateral or bilateral reading correction. same operation on the other eye; this should be done Isometropia for near in these cases will cause simiparticularly in the case where opacity is beginning lar problems at distance although usually less proand/or there is a shallow chamber and/or a tight nounced. ~ngle.
LUCIO BURATTO
Dr Lucio Buratto is based at the Centro Ambrosiano di Microchirurgia Oculare in Milan, where he practices refractive surgery and cataract surgery, and is an active teacher and author of scientific papers and books. 1. (a) Bilateral cataract and high myopia
The visual, cerebral and manual capacities of a high myopic patient with cataract (almost exclusively a person above 50 years of age) should be partially maintained; therefore the postoperative refraction necessary and attempted is about 3-4 myopic dioptres. 1. (b) Unilateral cataract and bilateral high myopia
To obtain 3-4 dioptres of myopia in the eye operated for cataract and (once refraction has stabilized in the operated eye) to apply a contact lens in the other eye which will provide the same myopic refraction.
(iii) Operate on the cataract and attempt to reach emmetropia, and perform corneal surgery for ' the correction of hypermetropia in the other eye. In that case, the choice of operations include: -hypermetropic PRK; -holmium laser; -epikeratophakia; -hypermetropic keratomileusis; naturally taking the degree of hypermetropia, the general conditions of the eye and the age and visual acuity of the patient into consideration.
2. Biometry technique and intraocular lens implant
If the biometric findings are normal, I do not change my usual technique. However, ifthe biometry is riot certain (especially in the cases of myopic staphyloma) numerous measurements are taken and the mean is calculated; sometimes an ultrasonic B scan is done to validate the biometric data.
3. What lens powers would you routinely implant? 1. (c) Bilateral cataract and bilateral high hypermetropia
To obtain distance emmetropia by operating on both eyes at a short interval. 1. (d) Unilateral cataract and bilateral high hypermetropia
This situation is rare; there are several solutions. Prior to surgery, the contact lens for the fellow eye (not to be operated) should be tested. (i)
(a) If it is well tolerated, operate on the eye with the cataract and attempt to reach emmetropia. (b) If it is not tolerated, operate for cataract and insert a lens which reduces existing
Firstly I take into account the preoperative refraction, the patient's age and his personal needs. In a young person (hypermetrope or myope, with or without preoPerative astigmatism) what I aim for is emmetropia. In the elderly patient, what I aim for is a slight to moderate myopia in line with his physical or professional activities or his visual needs.
If the desired lens power (e.g. 37D for hypermetropia-5 D for myopia) is not available, what would you do?
I would order the lens, wait for it to arrive and only then schedule the operation; however in the case of an emergency I would implant a lens whose power was as close as possible to the desired one. Eur J Implant Ref Surg, Vol 6, June 1994
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In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract how wouldyou advise the patient and what would you recommend:
most of them are operated in an out-patients' centre (day hospital); A complete list of the recent improvements would be too long. In the near future we can:
-for a 25-year-old with no other ocular disease Emmetropia. -for a 55-year-old with no other ocular disease Slight or moderate myopia in line with his visual needs in the myopic and emmetrope in the hyperopic.
Would you consider refractive surgery to the noncataractous eye subsequently?
Yes. (A) In myopia. (i) If the difference in the post-operative refraction is slight to moderate (up to 7-8 dioptres;, I would plan a PRK. (ii) If the difference in the post-operative refraction is too high (above 8 dioptres), I would plan an intrastromal keratomileusis with excimer laser. (iii) If there is a slight opacity in the lens, my temporary solution would be a contact lens and subsequently the extraction of the semi-transparent lens; alternatively, I would go directly to lens extraction. (B) In hypermetropia (though only in the case of real intolerance to contact lenses): (i) hypermetropic PRK if the hypermetropia is slight; (ii) Holmium laser if it is moderate; (iii) epikeratophakia or hypermetropic keratomileusis if the difference is great.
How do you think we can improve the care we currently give patients?
We are continually improving. Just think back three years! -we stitched all patients and there was therefore postoperative astigmatism, slow anatomical and functional recovery; -general anaesthesia was done on almost all patients; nowadays with the improvements in surgical techniques, it is possible to operate under parabulbar anaesthesia or even using topical and the results are just as good; -patients had to be admitted to hospital, now Eur J Implant Ref Surg, Vol 6, June 1994
-aim for low power or negative power lenses even for the capsular sac; in fact, the few that do exist were designed for the sulcus; -have lenses with a power exceeding 30 dioptres (even by doing a 2 by 2 D jump) for both the sac and the sulcus; -have a low-power, flexible IOL (which must be able to resist the force of capsular retraction without deforming) and ones for high hypermetropia (which shouldn't be too thick); -improve the formulae used for calculation in high myopia and hypermetropia; -improve the techniques used in refractive surgery so that the ametropia in the eye unaffected by cataract can be corrected precisely and safely, wihout removing the transparent lens. deforming) and ones for high hypermetropia (which shouldn't be too thick); - improve the formulae used for calculation in high myopia and hypermetropia; -improve the techniques used in refractive surgery so that the ametropia in the eye unaffected by cataract can be corrected precisely and safely, wihout removing the transparent lens.
I. HOWARD FINE
Dr Howard Fine is based at the University of Oregon, USA, and is well known for his innovations in cataract surgery, and his unfailing energy and committment to teaching.
Question: Approaches to ametropia in cataract surgery
Patients who have both cataract and ametropia may present specific management problems. What is your target post-operative refraction in patients with: 1. (a) bilateral cataract and high myopia
A plano to a -1.00 correction.
Discussion Section
1. (b) unilateral cataract and bilateral high myopia
I would have the patient try to wear a contact lens in the eye that was not going to undergo surgery and then try to achieve near emmetropia or myopia up to a -1.00 post-operatively. If the patient was unable to wear a contact lens, I would consider refractive surgery for the unoperated eye, anything that I could do, in order to be able to dramatically reduce the myopia in the side in which I was going to do cataract surgery. 1. (c) bilateral cataract and bilateral high hypermetropia
I would shoot for a plano in each eye. 1. (d) unilateral cataract and bilateral high hypermetropia
I would do the cataract, shoot for a plano, and offer the patient clear lensectomy in his fellow eye in order to achieve adequate emmetropia.
Do you modify your standard technique of biometry and intra-ocular lens implant power calculation for these cases, and if so how?
165
In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract how would you advise the patient and what would you recommend:
-for a 25-year-old with no other ocular disease
I would explain the basis of refractive errors, the impact of cataract, and the choices available both for correcting the eye with a cataract as well as for adjusting the refraction of the unoperated eye. -for a 55-year-old with no other ocular disease
I think one would have to do exactly the same thing. Would you consider refractive surgery to the non-cataractous eye subsequently?
I would consider refractive surgery to these cases. How do you think we can improve the care we currently give patients?
We can improve the care we currently give these patients by discussions such as this. Comments
We do modify our standard technique of biometry and intra-ocular lens power calculation for these cases. My chief technologist, Mary Watson, COMT, uses SRK-II and SRK-T formulae as well as fudge factors based on information in our computer and her past experience which is extensive in this regard.
What lens powers would you routinely implant?
We try to get as close to the desired lens power as we can. In most instances, depending on the fellow eye, we will go slightly above or below it. Or, we will change from our lens of routine use to another lens whose A-constant and lens calculation will get us nearest the desired post-operative refraction.
These authors all adopt a different emphasis in the way they manage these difficult combinations of refractive and cataract surgical problems. Nonetheless, current approaches to cataract surgery in these settings reflect an appreciation of the major refractive influences of surgery, and this is apparent in all the contributions. Refractive surgical approaches to ametropia are still evolving, and studies examining outcomes of different techniques of correcting high myopia, and high hypermetropia, will be valuable in refining therapeutic strategies in the management of cataractous patients with ametropia. The availability of a number of refractive surgical solutions to ametropic problems emphasizes the importance of considering a patient's refractive needs when planning the management of cataract in the setting of ametropia.
Eur J Implant Ref Surg, Vol 6, June 1994
Approaches to Ametropia in Cataract Surgery Edited by MICHAEL LAVIN
In recent years cataract surgical techniques such as phacoemulsification cataract extraction with implant of a folding lens through a small incision, have resulted in cataract procedures becoming more reproducible, predictable and with a lower risk of serious complications. Cataract surgery is being offered to patients with less advanced cataracts than previously, and may also be combined with refractive surgical procedures such as astigmatic keratotomies. Indeed, there is widespread acceptance of the refractive goals of cataract surgery, seeking not only to remove media opacity, but also to achieve the most suitable final refractive state for the patient. Patients who have both cataract and ametropia may present specific management problems, and we asked a number of leading cataract surgeons with experience in this area for their comments. We asked our contributors to address the following issues in their discussion of the management of ametropia in cataract surgery. 1. What is your target post-operative refraction in patients with: (a) bilateral cataract and high myopia (18 dioptres); (b) unilateral cataract and bilateral high myopia; (c) bilateral cataract and bilateral high hypermetropia (>+8 dioptre); (d) unilateral cataract and bilateral high hypermetropia?
2. Do you modify your standard technique of biometry and intra-ocular lens implant power calculation for these cases, and if so how? 3. What lens powers would you routinely implant? If the desired lens power (e.g. 37 D for hypermetropia-5 D for myopia) is not available, what would you do? 4. What would your desired post-operative refraction be in each case? 5. How would you manage the fellow eye? In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral
cataract, how would you advise the patient and what would you recommend: -for a 25-year-old with no other ocular disease; -for a 55-year-old with no other ocular disease? Would you consider refractive surgery to the noncataractous eye subsequently? How do you think we can improve the care we currently give patients? S.P.B. PERCIVAL
Mr Piers Percival is based at Scarborough Hospital, in England, where he has developed a well-deserved reputation in cataract and refractive surgery. 1. (a) Target post-operative refraction in patients with bilateral cataract and high myopia
My target is for 0 to -2 D myopia postoperatively, preferring to operate on the non-dominant eye first. The dominant eye is then operated on later aiming to emmetropia of the first eye becoming slightly myopic or aiming for low myopia according to the patient's wish. I use SRK II formula and do not modify my standard technique biometry except that if the result of the first eye has appeared inaccurate calculations are repeated before the second eye is operated on. The extent of the cataract will vary with different individuals and for those with only moderate opacities it is important that the patient is informed of and understands the risks. I explain that there is 5% risk of losing the sight (though not necessarily irreparably) from retinal detachment or vitreous haemorrhage during the first 2 years after surgery and that the risk of retinal detachment rises to 8% following posterior capsulotomy and that this is found to be necessary in about a third of all high myopes operated on. One should guard particularly against family or past history of retinal detachment and if examination under full mydriasis reveals evidence of peripheral retinal degeneration, these factors being relative contraindications of cataract sure gery. One should also beware of patients occupation
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Discussion Section
if this involves their unaided magnified VISIOn. Jewellers and clocksmiths may be dependent on this and may not thank the surgeon for curing their myopia. 1. (b) Unilateral cataract and bilateral high myopia
I would operate as above provided the patient understands and is informed of the risks. Provided the patient wishes for surgery, a history of partial amblyopia or known macular changes should not be a contraindication, for the sight will almost certainly be better once the cataract and high myopia have been treated. These unilateral cataracts are usually relatively blind eyes so there is little to lose and much to gain. For ametropias over 8 dioptres the improvement in visual field and pleasure in discarding thick glasses with their incapacitating optical defects generally outweighs the advantages of binocular vision and most patients are extremely grateful for the result. For the fellow eye a contact lens may maintain binocular vision but for those who wish to discard the contact lens or are intolerant to contact lenses, there is then a positive indication for clear lens extraction provided the patient asks for this and understands the risks. I do not recommend in these situations any alternative form of refractive surgery. 1. (c) Bilateral cataract and bilateral high hypermetropia (>+8 dioptre)
I would plan consecutive surgery aiming for emmetropia.
implantation vary between plano and +30.0. A +37 D would require a special order from the factory. If the power of 5 D was unavailable for some reason I would implant a 6 or 7 D knowing that this would result in an acceptable low myopic refraction. Any result between 0 and 2.5 D, postoperatively is acceptable (inaccuracies do happen for the first eye) and the aim should be for greater accuracy with the fellow dominant eye at a later date. 3. Bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract
I do not find any difficulty in advising bilateral cataract surgery for a 25-year-old with no other ocular disease who has a cataract already in one eye and wishes for refractive surgery for high ametropia. The treatment is the same as for a 55-year-old. Before a 25-year-old consents to surgery, however, it must be pointed out that the lens implant will be monofocal and that by having surgery the patient will lose the power of focusing (accommodation). For high myopes, one should recommend a single piece lens with loop span 13.5 mm and an optic diameter of 7 mm. The capsulorhexis diameter should be at least 6 mm (wider than usual) and the need for a wide optic implant for clear fundus examination postoperatively should override any surgeon preference for smaller incision surgery. All high myopes should have the retina examined with a slit lamp under extreme mydriasis within a few weeks of surgery for the presence of treatable retinal pathology. In my view there is no place at all for prophylactic retinal surgery, preoperatively. THOMAS NEUHANN
1. (d) Unilateral cataract and bilateral high hypermetropia
In general I would plan the same treatment and for the same reasons as in (2) above. The situation is slightly different in that the risk of vitreous haemorrhage and retinal detachment is negligible. However,. a history of amblyopia must be taken more seriously as this is generally much more denser in a hypermetrope; therefore if there is a history of amblyopia in the cataractous eye, surgery should be delayed until there are early lens changes in the fellow eye. 2. Biometry and intra-ocular lens implant powers
The lens powers which we have in stock for routine
Professor Neuhann is a gifted and energetic cataract surgeon, based in Munich, who regularly contributes new observations or innovations arising from his extensive surgical practice. 1. (a) Target post-operative refraction in patients with bilateral cataract and high myopia
In these patients it is important to first of all distinguish between those who have corrected their ametropia with contact lenses and those who have always worn glasses. Patients who have always worn glasses will generally be very reluctant to lose their ability to see well or even extremely well, including the magnifying effect, without glasses at very close up distances. Eur J Implant Ref Surg, Vol 6, June 1994
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In my experience they will therefore be happiest if left with a residual myopia of -3.0 D (±0.5). This enables them to follow their lifelong 'seeing habit' of near vision without glasses, while wearing corrective glasses for distance. With this refraction, glasses are usually absolutely no problem; a sizeable proportion of patients have even expressed discomfort with the thought of generally no longer wearing glasses postoperatively, since they themselves and their surroundings have been used to their appearance with glasses for such a long time. Others do not wear this distance correction for most of the time, since they feel their vision for most everyday purposes is so excellent that they do not feel a need for it except for special circumstances, e.g. driving, theatre, etc. On the other hand I have previously had high myopes severely complain postoperatively when their refraction was around emmetropia: although their uncorrected distance vision and their corrected near vision was excellent and greatly improved compared to preoperatively, they even called the situation 'worse than before because before I could read without glasses'. Thus, as a general rule, a residual refraction of -3.0 D will give the previously spectacle correct high myope the greatest comfort and satisfaction. For patients who have been generally contact lens corrected preoperatively, especially if they are adapted to the use of reading glasses and finally like their way of seeing, a residual refraction of -1.0 to -0.5 D, as I generally choose it for patients within the normal refractive range, will be most advantageous. It gives the patient a range of excellent uncorrected visual acuity between infinity and around one metre or even slightly below, thus covering most of our daily activities. For near vision the patient is used to additional correction.
1. (b) Unilateral cataract and bilateral high myopia
Generally the same principles as above apply. With satisfied contact lens wearers there are no problems: the criteria and arguments outlined above apply. Previous spectacle wearers are in a more difficult situation. I will generally offer them the available options, namely, the following. 1. Residual refraction of -3.0 in the operated eye and contact lens correction for the unoperated eye until this will have to be operated. One will generally propose a soft contact lens because unilateral hard contact lenses especially in this patient population are usually not tolerated. Any residual astigmatism can be spectacle corrected-especially since glasses will have to be prescribed anyway. If the Eur J Implant Ref Surg, Vol 6, June 1994
patient wishes I offer a preoperative trial of soft contact lens wear to give the patient a chance to judge whether this may be an option for him. 2. If contact lens wear is declined by the patient or if in the later postoperative course becomes intolerable, refractive lens surgery ('clear' lens exchange) is offered. It is clearly beyond the scope of this discussion to raise the entire controversy about this procedure; in any case on the basis of my experience I am convinced that the risklbenefit ratio ofthis approach justifies it in preference to the third and last option. 3. Correcting the operated eye to within 2.5 D of the refraction of the unoperated eye. This is also the sequence of my preferences when counselling the patient. 1. (c, d) Unilateral or bilateral cataract and bilateral high hypermetropia
By and large the same type of arguments applies, mutatis mutandis, to high hypermetropia. The only difference would be that there my preferred postoperative refraction would be -0.5 ±0.5 D for all types of patients. Also in high hypermetropia, refractive lens surgery in the unilateral cataract cases may be considered even more, since there does not appear to be a statistically increased long term postoperative retinal risk. 2. Biometry technique and intra-ocular lens implant power
The standard techniques of biometry are not modified, power-calculation takes the non-linearity in these extreme refractive ranges into consideration (e.g. SRK2, SKRT, Holladay and other theoretical formulas). What lens powers would you routinely implant?
I will implant the powers as indicated by the calculation. For all practical purposes there are no restrictions as to lens powers that can be manufactured. In a given case, I would have a lens custom manufactured. The age of the patient would modify my recommendations as to the desirable postoperative refraction only in one aspect: for a patient who can still accommodate with the fellow eye, I would like to have the operated eye -1.5 D from the refraction of the non-operated eye: this will minimize near aniseikonia sufficiently to enable binocularity with and
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without a reading correction in place over the operhypermetropia but which maintains binated eye. Isometropia for distance in a unilaterally ocular vision. accommodating patient will in most cases cause (ii) Operate on the cataract and attempt to reach considerable binocular problems for near, with or emmetropia with the intention of performing the without unilateral or bilateral reading correction. same operation on the other eye; this should be done Isometropia for near in these cases will cause simiparticularly in the case where opacity is beginning lar problems at distance although usually less proand/or there is a shallow chamber and/or a tight nounced. ~ngle.
LUCIO BURATTO
Dr Lucio Buratto is based at the Centro Ambrosiano di Microchirurgia Oculare in Milan, where he practices refractive surgery and cataract surgery, and is an active teacher and author of scientific papers and books. 1. (a) Bilateral cataract and high myopia
The visual, cerebral and manual capacities of a high myopic patient with cataract (almost exclusively a person above 50 years of age) should be partially maintained; therefore the postoperative refraction necessary and attempted is about 3-4 myopic dioptres. 1. (b) Unilateral cataract and bilateral high myopia
To obtain 3-4 dioptres of myopia in the eye operated for cataract and (once refraction has stabilized in the operated eye) to apply a contact lens in the other eye which will provide the same myopic refraction.
(iii) Operate on the cataract and attempt to reach emmetropia, and perform corneal surgery for ' the correction of hypermetropia in the other eye. In that case, the choice of operations include: -hypermetropic PRK; -holmium laser; -epikeratophakia; -hypermetropic keratomileusis; naturally taking the degree of hypermetropia, the general conditions of the eye and the age and visual acuity of the patient into consideration.
2. Biometry technique and intraocular lens implant
If the biometric findings are normal, I do not change my usual technique. However, ifthe biometry is riot certain (especially in the cases of myopic staphyloma) numerous measurements are taken and the mean is calculated; sometimes an ultrasonic B scan is done to validate the biometric data.
3. What lens powers would you routinely implant? 1. (c) Bilateral cataract and bilateral high hypermetropia
To obtain distance emmetropia by operating on both eyes at a short interval. 1. (d) Unilateral cataract and bilateral high hypermetropia
This situation is rare; there are several solutions. Prior to surgery, the contact lens for the fellow eye (not to be operated) should be tested. (i)
(a) If it is well tolerated, operate on the eye with the cataract and attempt to reach emmetropia. (b) If it is not tolerated, operate for cataract and insert a lens which reduces existing
Firstly I take into account the preoperative refraction, the patient's age and his personal needs. In a young person (hypermetrope or myope, with or without preoPerative astigmatism) what I aim for is emmetropia. In the elderly patient, what I aim for is a slight to moderate myopia in line with his physical or professional activities or his visual needs.
If the desired lens power (e.g. 37D for hypermetropia-5 D for myopia) is not available, what would you do?
I would order the lens, wait for it to arrive and only then schedule the operation; however in the case of an emergency I would implant a lens whose power was as close as possible to the desired one. Eur J Implant Ref Surg, Vol 6, June 1994
M. Lavin
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In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract how wouldyou advise the patient and what would you recommend:
most of them are operated in an out-patients' centre (day hospital); A complete list of the recent improvements would be too long. In the near future we can:
-for a 25-year-old with no other ocular disease Emmetropia. -for a 55-year-old with no other ocular disease Slight or moderate myopia in line with his visual needs in the myopic and emmetrope in the hyperopic.
Would you consider refractive surgery to the noncataractous eye subsequently?
Yes. (A) In myopia. (i) If the difference in the post-operative refraction is slight to moderate (up to 7-8 dioptres;, I would plan a PRK. (ii) If the difference in the post-operative refraction is too high (above 8 dioptres), I would plan an intrastromal keratomileusis with excimer laser. (iii) If there is a slight opacity in the lens, my temporary solution would be a contact lens and subsequently the extraction of the semi-transparent lens; alternatively, I would go directly to lens extraction. (B) In hypermetropia (though only in the case of real intolerance to contact lenses): (i) hypermetropic PRK if the hypermetropia is slight; (ii) Holmium laser if it is moderate; (iii) epikeratophakia or hypermetropic keratomileusis if the difference is great.
How do you think we can improve the care we currently give patients?
We are continually improving. Just think back three years! -we stitched all patients and there was therefore postoperative astigmatism, slow anatomical and functional recovery; -general anaesthesia was done on almost all patients; nowadays with the improvements in surgical techniques, it is possible to operate under parabulbar anaesthesia or even using topical and the results are just as good; -patients had to be admitted to hospital, now Eur J Implant Ref Surg, Vol 6, June 1994
-aim for low power or negative power lenses even for the capsular sac; in fact, the few that do exist were designed for the sulcus; -have lenses with a power exceeding 30 dioptres (even by doing a 2 by 2 D jump) for both the sac and the sulcus; -have a low-power, flexible IOL (which must be able to resist the force of capsular retraction without deforming) and ones for high hypermetropia (which shouldn't be too thick); -improve the formulae used for calculation in high myopia and hypermetropia; -improve the techniques used in refractive surgery so that the ametropia in the eye unaffected by cataract can be corrected precisely and safely, wihout removing the transparent lens. deforming) and ones for high hypermetropia (which shouldn't be too thick); - improve the formulae used for calculation in high myopia and hypermetropia; -improve the techniques used in refractive surgery so that the ametropia in the eye unaffected by cataract can be corrected precisely and safely, wihout removing the transparent lens.
I. HOWARD FINE
Dr Howard Fine is based at the University of Oregon, USA, and is well known for his innovations in cataract surgery, and his unfailing energy and committment to teaching.
Question: Approaches to ametropia in cataract surgery
Patients who have both cataract and ametropia may present specific management problems. What is your target post-operative refraction in patients with: 1. (a) bilateral cataract and high myopia
A plano to a -1.00 correction.
Discussion Section
1. (b) unilateral cataract and bilateral high myopia
I would have the patient try to wear a contact lens in the eye that was not going to undergo surgery and then try to achieve near emmetropia or myopia up to a -1.00 post-operatively. If the patient was unable to wear a contact lens, I would consider refractive surgery for the unoperated eye, anything that I could do, in order to be able to dramatically reduce the myopia in the side in which I was going to do cataract surgery. 1. (c) bilateral cataract and bilateral high hypermetropia
I would shoot for a plano in each eye. 1. (d) unilateral cataract and bilateral high hypermetropia
I would do the cataract, shoot for a plano, and offer the patient clear lensectomy in his fellow eye in order to achieve adequate emmetropia.
Do you modify your standard technique of biometry and intra-ocular lens implant power calculation for these cases, and if so how?
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In the setting of bilateral high ametropia (high myopia, or high hypermetropia) and unilateral cataract how would you advise the patient and what would you recommend:
-for a 25-year-old with no other ocular disease
I would explain the basis of refractive errors, the impact of cataract, and the choices available both for correcting the eye with a cataract as well as for adjusting the refraction of the unoperated eye. -for a 55-year-old with no other ocular disease
I think one would have to do exactly the same thing. Would you consider refractive surgery to the non-cataractous eye subsequently?
I would consider refractive surgery to these cases. How do you think we can improve the care we currently give patients?
We can improve the care we currently give these patients by discussions such as this. Comments
We do modify our standard technique of biometry and intra-ocular lens power calculation for these cases. My chief technologist, Mary Watson, COMT, uses SRK-II and SRK-T formulae as well as fudge factors based on information in our computer and her past experience which is extensive in this regard.
What lens powers would you routinely implant?
We try to get as close to the desired lens power as we can. In most instances, depending on the fellow eye, we will go slightly above or below it. Or, we will change from our lens of routine use to another lens whose A-constant and lens calculation will get us nearest the desired post-operative refraction.
These authors all adopt a different emphasis in the way they manage these difficult combinations of refractive and cataract surgical problems. Nonetheless, current approaches to cataract surgery in these settings reflect an appreciation of the major refractive influences of surgery, and this is apparent in all the contributions. Refractive surgical approaches to ametropia are still evolving, and studies examining outcomes of different techniques of correcting high myopia, and high hypermetropia, will be valuable in refining therapeutic strategies in the management of cataractous patients with ametropia. The availability of a number of refractive surgical solutions to ametropic problems emphasizes the importance of considering a patient's refractive needs when planning the management of cataract in the setting of ametropia.
Eur J Implant Ref Surg, Vol 6, June 1994