The nationwide study of epikeratophakia for aphakia in older children

Non-Freeze Epikeratophakia in Children

We describe the use of unfrozen tissue lenses in 42 cases of epikeratophakia in children aged 2-14 years. Fourteen operations were performed in an aphakic eye, 28 in combination with congenital or traumatic cataract extraction. The tissue lenses, made from unfrozen donor cornea according to an original design, healed in 91.5% of cases. The tissue lens was removed when epithelial growth was inadequate on its surface. A five-year follow-up showed that correction within 3.0 D of emmetropia was achieved in 73.7% of the eyes. Preoperatively, mean keratometry readings were 43.5±0.2 D, increasing postoperatively to 53.6±0.8 D. Mean spherical equivalent at the spectacle plane increased by 9.6±0.9 D. Our investigations show the efficacy and safety of non-freeze epikeratophakia in the correction of pediatric aphakia.

Keratoglobus

Keratoglobus is a rare noninflammatory corneal thinning disorder characterised by generalised thinning and globular protrusion of the cornea. It was first described as a separate clinical entity by Verrey in 1947. Both congenital and acquired forms have been shown to occur, and may be associated with various other ocular and systemic syndromes including the connective tissue disorders. Similarities have been found with other noninflammatory thinning disorders like keratoconus that has given rise to hypotheses about the aetiopathogenesis. However, the exact genetics and pathogenesis are still unclear. Clinical presentation is characterised by progressive diminution resulting from irregular corneal topography with increased corneal fragility due to extreme thinning. Conservative and surgical management for visual rehabilitation and improved tectonic stability have been described, but remains challenging. In the absence of a definitive standard procedure for management of this disorder, various surgical procedures have been attempted in order to overcome the difficulties. This article reviews the aetiological factors, differential diagnosis, histopathology, and management options of keratoglobus.

Refractive surgery: through the looking glass

Historically, surgical procedures designed to change the refractive power of the cornea have been controversial at their inception, gaining acceptance only with time and study. From intraocular lenses to corneal remodelling with the excimer laser, and numerous procedures in between, including radial keratotomy, epikeratophakia, incisional keratotomy for astigmatism, and hydrogel and polysulfone implants, ophthalmologists have balanced the risks and benefits for their patients to produce the maximum benefit at the least cost. The present status and future potential of each of these are assessed as they appear today. There is no question that progress will continue, and that our patients will be the beneficiaries of our ongoing interest in improving older procedures and developing new techniques for the correction of refractive errors.

Viability of keratocytes in epikeratophakia lenticules

AIM

To study the influence of cryoprotectant, cooling rate, and warming rate on recovery and viability of keratocytes from corneas for cryolathing.

METHODS

Corneas were frozen at -50 degrees C for 2 minutes either after exposure to 10% dimethyl sulphoxide in Eagle's MEM for 15 minutes at room temperature (about 22 degrees C), or without earlier exposure to the cryoprotectant. Corneas were cooled either rapidly (20 degrees C/min) or slowly (1 degree C/min), and they were warmed either rapidly (> 50 degrees C/min) by direct transfer into medium at 22 degrees C or slowly (< 20 degrees C/min) in air at 22 degrees C. The cryoprotectant was removed by dilution in medium containing 0.5 mol/l sucrose. Recovery of keratocytes was determined by using collagenase digestion to release the cells from the stroma and trypan blue staining. Viability was assessed by the outgrowth of cells from stromal explants in primary tissue culture.

RESULTS

The use of a cryoprotectant before freezing was beneficial, irrespective of the different cooling and warming regimens. Both collagenase digestion and tissue culture revealed that keratocyte survival was improved when corneas were warmed rapidly rather than slowly. The collagenase digestion assay showed an apparently higher recovery of keratocytes after slow cooling (54.3%) than after rapid cooling (34.1%), but no differences in cell viability could be demonstrated by primary tissue culture.

CONCLUSION

Although in these experiments slow cooling apparently provided the best recovery of keratocyte numbers (though not viability), previous work had revealed some disruption of the epithelial basement membrane after slow cooling. If viable keratocytes and good preservation of epithelial basement membrane are considered to be prerequisites for epikeratophakia lenticules then it is suggested that corneas should be prepared for cryolathing by freezing rapidly after exposure to 10% dimethyl sulphoxide and, following cryolathing, they should be warmed rapidly.

Factors affecting visual outcome in children following uniocular traumatic cataract

The correction of paediatric traumatic aphakia remains a controversial topic. This study examines retrospectively the visual outcome in 32 children with uniocular traumatic cataracts. Fifteen received intraocular lens implants following lensectomy, and 17 received aphakic contact lenses. Age range was 2-14 1/2 years at the time of injury. The maximum follow-up time was 13 years. Twenty-four children obtained a good visual result (6/5 to 6/18). These were equally divided between those receiving intraocular lens implants and those with contact lenses. Factors adversely affecting visual outcome are discussed. These include complex trauma, delay in referral for lensectomy, inadequate postoperative correction of aphakia, contact lens difficulties and problems with occlusion therapy. Although aphakic correction with intraocular lens implants may require several subsequent surgical procedures such as capsulotomy, we advise early lensectomy and intraocular lens implantation where possible, particularly in young children with traumatic cataracts. This eliminates contact-lens-associated problems and maximises the chance of good visual outcome and retention of stereoscopic vision.

Visual outcome of childhood anterior perforating eye injuries: prognostic indicators

Ninety-six cases of anterior globe perforation in children less than 16 years old, requiring surgical repair, were reviewed. Seventy-three patients were male and 23 female, with a mean age of 9 years 4 months. Perforation involving just the cornea was associated with a good visual prognosis unless: it involved the visual axis, resulting in corneal scarring and/or significant astigmatism (> 3.0 DS); it involved greater than one-quarter of corneal diameter; or there was non-compliance with spectacles/patching in patients younger than 8 years old. Injuries involving the lens in those younger than 8 years were associated with a far worse prognosis due to the problems of correcting aphakia. Surgical delay and method of injury did not affect prognosis. Some patients fail to re-attend and greater patient/parent education prior to discharge is recommended.

Pediatric aphakic contact lens wear: rates of successful wear

Two hundred thirty-eight consecutive patients with pediatric cataracts were fitted with a variety of aphakic contact lenses after cataract extraction. Thirty-nine patients did not return for follow up. Of the remaining 199 patients, 40 discontinued contact lens wear. None of the 78 patients with unilateral or bilateral acquired cataracts discontinued contact lens wear due to problems wearing their lenses, although nine discontinued contact lens wear due to poor vision or difficulty maintaining amblyopia treatment. Twenty-two of 84 patients with unilateral congenital cataracts discontinued lens wear, six directly due to difficulties wearing lenses. Sixteen had poor vision in their aphakic eye and inability to maintain patching for amblyopia. Eight of 37 patients with bilateral congenital cataracts discontinued lens wear because of problems wearing their lenses, and one other discontinued lens wear because of poor vision. In summary, 26 of 40 patients (out of a total of 199) that discontinued aphakic contact lens wear did so because of poor vision, while only 14 did so because of difficulties wearing the contact lenses. Eleven of these 14 patients were able to wear aphakic spectacles in lieu of contact lenses. This study shows that most pediatric patients with cataracts fail at treatment because of problems related to treatment of amblyopia, and not problems related to the fitting and wearing of contact lenses.

Risk factors for complications following pediatric epikeratoplasty

We studied the prevalence and types of complications that occurred in children treated with epikeratoplasty to identify risk factors. A review of the clinical records of 88 consecutive patients (106 eyes; 114 procedures) revealed that no complications occurred in 58 grafts (54%). Refractive complications (refractive error greater than 3.00 diopters spherical equivalent from emmetropia or astigmatism greater than 3.00 diopters) occurred in 30 eyes (28%). Medical complications occurred in 22 eyes (19%); these included epithelial defects (14 grafts), interface opacities (six grafts), graft vascularization (eight grafts), graft infection (two grafts), graft necrosis (five grafts), graft haziness (four grafts) or opacification (11 grafts), and graft dehiscence (three grafts). Eleven grafts (10%) were removed and five eyes received new grafts. Epikeratoplasty in children will be more successful if risk factors such as patient age less than one year, microcornea, corneal endothelial cell dysfunction, mental retardation, and combining the procedure with cataract surgery are avoided.

Physiologic analysis of corneal healing after epikeratophakia

The evaluation of epithelial permeability, stromal transparency, and endothelial cell density is essential to determine the resumption of normal function in each corneal physiologic unit after refractive surgical procedures. The authors report the results of a prospective study conducted in 55 consecutive patients undergoing epikeratophakia using prelathed, lyophilized tissue lenses. Epithelial permeability was evaluated by means of fluorophotometry preoperatively and 1, 2, 4, 8, 12, 24, and 52 weeks after epikeratophakia. With few exceptions, Scheimpflug photography also was performed at the same examination times to assess stromal optical density. Endothelial cell counts were performed in each patient preoperatively and between 6 and 12 months postoperatively. The epithelial barrier function resumed normal values within 8 weeks after epikeratophakia. The optical density of both donor lenticule and recipient corneas was initially increased but returned to values comparable with those of unoperated corneas by 12 weeks postoperatively. Endothelial cell density was not affected by epikeratophakia. These results confirm the authors' preliminary observation that epikeratophakia allows a relatively quick recovery of normal corneal functions and should prompt investigators to demonstrate the safety of other refractive surgical procedures in a similar way.

Neonatal cataract: aetiology, pathogenesis and management

We review the epidemiology, aetiology, pathogenetic mechanisms and clinical management of neonatal cataract. Visual development and the effects of visual deprivation in the infant with congenital cataract are discussed and related to the timing of surgery. Surgical techniques and the important operative and post-operative complications are discussed. We review post-operative management and compare the different techniques available for aphakic correction, and describe the VEP changes found in patients with monocular cataract.

Visual performance after aphakic epikeratoplasty

While good visual acuity and refractive results after epikeratoplasty for aphakia have been reported, particularly for adults and older children, limited detailed information on the nature of the resulting vision is available. We have evaluated the visual performance of seven aphakic subjects corrected by epikeratoplasty by measuring contrast sensitivity, with and without the presence of glare. These results were compared with those for other aphakic corrections, namely spectacles (n = 5 eyes), contact lenses (n = 5 eyes), or intraocular lens implantation (n = 5 eyes). There were statistically significant differences among these four aphakic correction types (p = 0.0330), with a consistent trend for diminished visual performance after epikeratoplasty. Threshold elevations occurred in the presence of glare, but they were not statistically different between the groups (p = 0.1631). Based on these visual assessments, epikeratoplasty does result in statistically significant visual losses. Despite this, it may still offer an acceptable alternative to other managements of the aphakic patient when those others are contraindicated.

Epikeratoplasty with nonlyophilized tissue in children with aphakia

We studied 75 epikeratoplasty procedures using nonlyophilized tissue performed by eight ophthalmic surgeons in 70 eyes (47 patients) to correct for aphakia in children less than 8 years of age (mean age, 3.4 +/- 2.1 years). Of the 47 patients in the study, 24 were girls and 23 were boys; 23 patients had bilateral surgery. Seven of the epigrafts required removal; two were not replaced, and five underwent successful repeat epikeratoplasty. Overall, the success rate (that is, the percentage of epigrafts that remained optically and functionally clear throughout the course of this study) for the epikeratoplasty procedure was 89% (62 of 70 eyes) for initial surgery and 96% (67 of 70 eyes) for repeat surgery. The average spherical equivalent was +14.4 +/- 3.7 diopters preoperatively and +0.3 +/- 2.9 diopters one year after the operation. One year after the final surgical procedure, 42 of 56 eyes (75%) were within 3 diopters of emmetropia. In the 29 verbal patients, best-corrected visual acuity was 20/100 or better in 25 (86.2%) one year after the operation.

Intraocular lens implantation in children with unilateral traumatic cataract

A group of 23 children with traumatic pseudophakia was evaluated. Intraocular lens (IOL) implantation was performed as a primary procedure, immediately after aspiration of the traumatic lens, in 7 cases and as a secondary procedure in 16 cases. The mean followup was 6.5 years, varying from 1.5 to 11 years. A visual acuity of 0.7 or more was achieved in 3 of the 8 patients under 7 years of age and in 13 of the 15 cases from 7 to 14 years of age. Awaiting longer follow-up results of epikeratophakia in children we advise to perform early IOL implantation in children under 7 years of age, combined with a rigid amblyopia treatment scheme. In children older than 7 years of age we prefer to try the use of contact lenses first and preserve IOL implantation for selected cases.

Bilateral phakic hypermetropic epikeratoplasty for accommodative esotropia

Optical correction of high hypermetropia with glasses is the primary treatment for accommodative esotropia. These glasses are often poorly accepted by adolescents and young adults for they are cosmetically undesirable, heavy, and esotropia occurs with their removal. We report an 11 1/2-year-old, physically mature female with high hypermetropia and accommodative esotropia corrected to orthophoria with glasses who was unable to be weaned from her glasses. She became intolerant to glasses wear, refused contact lenses, and was treated successfully with bilateral phakic hypermetropic epikeratoplasty. Two years postepikeratoplasty her visual acuity is 20/40 and 20/20 uncorrected and the vision in the amblyopic right eye has remained at its maximum preoperative level. She is orthophoric at distance and has a 2 prism diopter monofixational esophoria at near without glasses. Epikeratoplasty is an option in the treatment of accommodative esotropia for patients who are past the amblyopia forming age, have a stable angle of strabismus, and who require their full hypermetropic optical correction to maintain orthophoria.

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.

Intraocular lens implants for uniocular cataracts in childhood

We report the outcome of intraocular lens implantation in 20 children with visually significant cataracts (seven traumatic, 13 non-traumatic). Six patients had anterior and 14 had posterior chamber implants. The mean age of the whole group at the time of surgery was 5.9 years (range 0.3 to 15.1 years), while the mean period of follow-up was 2.4 years (range 0.8 to 5.9 years). Postoperatively 10 patients developed a transient fibrinous uveitis, four required lens repositioning, one needed lens removal, and eight required posterior capsulotomy. Complications warranting secondary surgical procedures occurred predominantly in eyes with posterior chamber implants. Co-operation with conventional amblyopia treatment was satisfactory in eight out of 16 patients. Postoperatively nine out of 18 patients had peripheral fusion, four patients regained visual acuities of better than 6/9, and visual acuity did not improve beyond 3/60 in six cases. In 19 eyes the optical pathway to the retina is clear and the implants are stable with no evidence of persisting inflammation. Contact lenses remain the initial treatment of choice in infancy, but modern intraocular lenses are well tolerated and have a role in the visual rehabilitation of patients with contact lens and probable contact lens failures and older children with uniocular cataracts.