Refractive and visual results and patient satisfaction after excimer laser photorefractive keratectomy for myopia.

A study of excimer laser photorefractive keratectomy was performed on 108 patients. Variation in individual refractive outcome was noted, particularly for the higher levels of correction. At 12 months, of those with up to 3 dioptres of myopia, 93% were within 1 dioptre of emmetropia, 100% achieved an acuity of 6/12 unaided, 69% were very pleased with their result, and 10% were very disappointed. Of those with between 3.1 and 6 dioptres of myopia, the respective figures were 75%, 73%, 65%, and 11%. For those with over 6 dioptres of myopia the respective figures were 46%, 58%, 38%, and 23%. Some patients were disappointed despite having achieved good unaided visual acuity. Forty seven per cent of patients lost at least one Snellen line of best corrected acuity. Glare was a problem for some of the time in over 60%. Perceived distortion of vision was a problem for all of the time in 11% to 31% of cases depending on the initial level of myopia. In some cases the refraction continued to change between 12 months and 20 months.

Surgical management of essential blepharospasm.

We have reviewed the surgical management of essential blepharospasm over the last 15 years, comparing the results from facial nerve avulsion with those from orbicularis muscle stripping. After facial nerve avulsion 50% of patients remained free of troublesome spasm for 15 months after surgery, but only 25% remained so for more than two years. Following orbicularis oculi myectomy 50% of patients were free of troublesome spasms for 30 months after surgery and 55% of patients had relief from spasm for more than two years. Secondary effects of the two procedures are compared and are found to be fewer after orbicularis myectomy. There were no major complications after either form of surgery. Botulinum toxin is the treatment of first choice for this condition. If this becomes ineffective or inconvenient, surgical treatment is warranted and should not be deferred for fear of severe side effects of treatment, since these are rare. Protractor myectomy gives longer relief from blepharospasm than facial nerve avulsion and has fewer complications. However, it is technically difficult, time consuming, and has greater peroperative morbidity. Facial nerve avulsion may therefore still have a role in selected patients.

Epikeratophakia for aphakia, keratoconus, and myopia.

A series of 67 cases of epikeratophakia is presented with an average time from surgery of 12.2 months. For aphakia there was a delay in the recovery of vision, but by nine months 83% of 57 patients achieved an acuity equal to, or within 1 line of, the preoperative value. 57% were corrected to within 3 dioptres of emmetropia, but in the latter part of the series 75% were within this range. Astigmatism and reduced contrast sensitivity, especially in the presence of glare, were important complications. For keratoconus, 86% of seven patients with over two months of follow-up achieved a spectacle corrected acuity of 6/9 or better. One patient had surgery for myopia and obtained the desired refractive correction.

Epikeratophakia for keratoconus.

Results of the author's first 15 cases of epikeratophakia for keratoconus are presented. All patients were intolerant of contact lens correction and could not achieve satisfactory acuity with spectacle correction due to corneal ectasia and irregular astigmatism. The average follow-up was 13 months. Seventy-three per cent of eyes treated had a pre-operative spectacle acuity of 6/60 or worse. One eye had a preexisting amblyopia that limited final acuity, but every other eye achieved a post-operative spectacle acuity of 6/12 or better and 50% achieved 6/6. One eye had 11 dioptres of post-operative astigmatism and required penetrating keratoplasty; the remaining eyes had an average astigmatism of 1.9 dioptres. Epikeratophakia appears to be a safe alternative to penetrating keratoplasty in selected cases.

Effect of donor parameters on primary graft failure and the recovery of acuity after keratoplasty.

A retrospective evaluation was made of 983 penetrating corneal grafts. Donor corneas stored in either K-Sol or McCarey-Kaufman media had a significantly greater rate of primary graft failure (about 2%) than those kept in moist chamber storage (0%). Selected subgroups of 50 corneas from each storage system were studied to determine the time taken to reach a postoperative acuity of 6/12. No significant correlation was found between this time and either the duration of storage of donor corneas or the age of donor. A significant delay in recovery of visual acuity was found with increasing age of recipient. The increased average time from donor death to surgery for K-Sol (56 hours) and McCarey-Kaufman (40 hours) corneas compared with moist chamber corneas (15 hours) facilitated the scheduling of surgery at the cost of increased chance of primary graft failure.

Simplified formulas for lathing aphakic epikeratophakia lenses.

Geometrically based formulas for lathing aphakic epikeratophakia lenses have been simplified to enable easy calculation of the radii of cut for the optical and the wing zones. The formulas compensate for postoperative thinning of the lens on host cornea and allow for any desired amount of pre-lathing dehydration. Clinical results to date show that over 80% of lenses are made within 3 diopters of the expected power.

Glare and contrast sensitivity in contact lens corrected aphakia, epikeratophakia and pseudophakia.

The effects of glare on contrast sensitivity and high contrast Snellen acuity were investigated in a group of unilaterally aphakic patients with normal fellow eyes. In spite of relatively good visual acuity and apparently satisfactory surgical results, there was a marked reduction in contrast sensitivity in epikeratophakia and contact lens corrected aphakic eyes, relative to fellow normal eyes, especially in the presence of glare (P less than 0.05). Although the results from the pseudophakic patients were more variable, there is some evidence to suggest that epikeratophakia provides inferior visual function to contact lens correction or intraocular lens implantation. The results also suggest that the measurement of visual acuity in the presence of glare fails to identify many patients with a functional visual impairment secondary to glare.

A new surgical head rest.

A surgical head rest is described that gives good wrist support, provides space to place instruments, and allows drainage of irrigation fluid.

Manufacture of epikeratophakia lens.

Epikeratophakia lenses may be manufactured from donor cornea either with a lathe or using devices that make flat cuts on to previously deformed cornea. Details are given of a manufacturing technique using a cryolathe, including the storage and preparation of donor corneas and derivation of the formulae used to determine the radius of lathe cut.

Precarved lyophilized tissue for lamellar keratoplasty in recurrent pterygium.

Thirteen eyes with recurrent pterygia were treated with excision and lamellar keratoplasty using precarved, lyophilized donor cornea. After an average follow-up of 23 months, only one eye (7.7%) required repeat excision. Two eyes (15.4%) had minor recurrences that were asymptomatic and did not progress. Minimal vascularization at the interface between donor and recipient cornea was frequent, but this completely regressed after suture removal and topical corticosteroid treatment. Limitation of movement, when present preoperatively, was improved or eliminated. Best corrected visual acuity was unchanged in eight eyes (61.5%), decreased by one line in two eyes (15.4%), and improved by one or two lines in three eyes (23.1%). Postoperative astigmatism was within 0.5 diopter of the preoperative value in 11 eyes (84.6%); one eye (7.7%) had a postoperative increase of 1 diopter and another eye (7.7%) of 2 diopters.

Calculation of intraocular lens power--results in practice.

There have been many reports describing the use of formulas to derive lens implant power in cataract surgery. Typically over 80 per cent of patients are said to have a final refraction within one dioptre of the desired value. In our clinical practice results are worse. Modification of the formula to suit an individual surgeon and implant style would probably improve results.

Comparison of 2 interferometers for predicting visual acuity in patients with cataract.

Two clinical interferometers generated gratings directly on to the retina in young experienced observers and also in patients about to undergo cataract surgery. Eyes in the patients with no media opacities were used as controls. We agreed with the manufacturers' claims that gratings are seen on the retina independent of refractive state and that gratings can still be seen through most cataracts. However, we did not find that preoperative retinal visual acuity was of any value in predicting postoperative Snellen visual acuity. Reasons for this are discussed.

A forced-choice test improves clinical contrast sensitivity testing.

Decreased contrast sensitivity has been demonstrated in early glaucoma, but the deficit in not regularly observed. We designed a prototype for a forced-choice printed test and evaluated it with several other measures of contrast sensitivity. The results also bear on the pattern of loss and the variables which effect performance. Mildly glaucomatous patients show at 6 db (50%) loss of contrast sensitivity at all spatial frequencies tested compared with age matched controls. Moving gratings give the same information as stationary ones, and practice effects are negligible. Contrast sensitivity at or below 2 cycles/degree is poorly correlated with visual acuity and does not change with age in the forced-choice test. Subjective judgment made the apparent contrast threshold higher, age dependent, and more variable, particularly at higher spatial frequencies. The pattern of variability can explain some reports of insignificant effects and why low spatial frequency contrast sensitivity detects glaucoma better than visual acuity. Methods correlated so poorly, despite high reliabilities, that uncontrolled biases must be suspected in subjective measures. Our new forced-choice format was superior to all other tests on at least one formal criterion and always at least equal to them. Improvements in contrast sensitivity screening tests are thus indicated.