Case series of 12 children with progressive axial myopia following unilateral cataract extraction

Myopia in India

India is a culturally and geographically diverse nation. Its vast demographic nature does not allow a single definition for any of the given medical conditions in its territory. One important clinical condition which has created an uproar in the rest of the world is myopia. Its cause, prevalence, etiopathogenesis and other factors are being explored constantly; however, data with respect to Indian subcontinent are genuinely missing. Hence, in this review, we enumerate the country’s myopia journey from last 4 decades. The epidemiology, genetics, ocular/systemic association, quality of life, imaging, and management in myopia with necessary future directives are discussed to augment the overall management in future.

The relationship between anisometropia and amblyopia

This review aims to disentangle cause and effect in the relationship between anisometropia and amblyopia. Specifically, we examine the literature for evidence to support different possible developmental sequences that could ultimately lead to the presentation of both conditions. The prevalence of anisometropia is around 20% for an inter-ocular difference of 0.5D or greater in spherical equivalent refraction, falling to 2-3%, for an inter-ocular difference of 3D or above. Anisometropia prevalence is relatively high in the weeks following birth, in the teenage years coinciding with the onset of myopia and, most notably, in older adults starting after the onset of presbyopia. It has about one-third the prevalence of bilateral refractive errors of the same magnitude. Importantly, the prevalence of anisometropia is higher in highly ametropic groups, suggesting that emmetropization failures underlying ametropia and anisometropia may be similar. Amblyopia is present in 1-3% of humans and around one-half to two-thirds of amblyopes have anisometropia either alone or in combination with strabismus. The frequent co-existence of amblyopia and anisometropia at a child's first clinical examination promotes the belief that the anisometropia has caused the amblyopia, as has been demonstrated in animal models of the condition. In reviewing the human and monkey literature however it is clear that there are additional paths beyond this classic hypothesis to the co-occurrence of anisometropia and amblyopia. For example, after the emergence of amblyopia secondary to either deprivation or strabismus, anisometropia often follows. In cases of anisometropia with no apparent deprivation or strabismus, questions remain about the failure of the emmetropization mechanism that routinely eliminates infantile anisometropia. Also, the chronology of amblyopia development is poorly documented in cases of 'pure' anisometropic amblyopia. Although indirect, the therapeutic impact of refractive correction on anisometropic amblyopia provides strong support for the hypothesis that the anisometropia caused the amblyopia. Direct evidence for the aetiology of anisometropic amblyopia will require longitudinal tracking of at-risk infants, which poses numerous methodological and ethical challenges. However, if we are to prevent this condition, we must understand the factors that cause it to develop.

Peripheral refraction in pseudophakic eyes measured by infrared scanning photoretinoscopy

PURPOSE

To obtain quantitative data of peripheral refractive errors in pseudophakic eyes including measurements up to ±45 degrees on the retina.

SETTING

University Eye Hospital, Tübingen, Germany.

DESIGN

Population-based cross-sectional study.

METHODS

Pseudophakic and phakic subjects were measured with a purpose-built scanning photorefractor. The instrument was improved over previous versions. It permits measurement of semicontinuous peripheral profiles over the central 90-degree field of the retina at a faster speed (4 s/scan).

RESULTS

Twenty-four pseudophakic and 43 phakic subjects were enrolled. The intraocular lenses (IOLs) induced a mean myopic shift of 2.00 diopters (D) at ±45 degrees of eccentricity in the vertical pupil meridian. Ray-tracing simulations with phakic eye and pseudophakic eye models agreed well with the experimental data. They showed that changes induced by IOLs were a consequence of an increase in astigmatism with eccentricity and a myopic shift in the spherical equivalent.

CONCLUSIONS

The peripheral refractions in pseudophakic eyes were more myopic than in phakic eyes as a consequence of the optical design of the IOLs. Whether a more myopic refraction of approximately 2.00 D at 45 degrees has significant effects on visual performance must be tested. Perhaps there is room for improvement in the peripheral optics of IOLs.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Unilateral axial length elongation with chronic traumatic cataracts in young Kenyans

PURPOSE

To assess whether unilateral axial elongation in chronic traumatic cataract is associated with the time interval from trauma to surgery.

SETTING

PCEA Kikuyu Hospital Eye Unit, Nairobi, Kenya.

METHODS

This retrospective cohort study analyzed patients with traumatic cataract operated on between 1998 and 2007. Study patients (n = 13) had a delay from trauma to surgery of more than 1 year and an interocular axial length (AL) difference greater than 1.0 mm. Randomly selected age-matched control patients (n = 14) had less than 1 year delay between trauma and surgery. The correlation between interocular AL difference and surgical delay was calculated in each group.

RESULTS

The median interval from trauma to surgical treatment in study patients was 8 years (range 1 to 27 years). Study patients had a significantly higher median interocular AL difference (3.09 mm; interquartile range [IQR] 2.45 to 4.13 mm) than control patients (0.24 mm; IQR 0.15 to 0.30 mm) (P = .000). The length of delay from trauma to surgical treatment did not correlate strongly with the interocular AL difference in study or control patients (R(2) = 0.0143 and R(2) = 0.1697, respectively).

CONCLUSIONS

Unilateral AL elongation may occur in young adults with chronic traumatic cataract. Delay of more than 1 year from trauma to surgery was associated with axial elongation, although the degree of elongation did not correlate with duration of delay. Surgeons are advised to implant lower-power intraocular lenses in such patients based on biometry readings to avoid postoperative refractive surprises.

Intraocular lens power calculation in children

With improving surgical technique and equipment, the acceptable age for placing an intraocular lens in infants and children is becoming younger. The tools for predicting intraocular lens power have not necessarily kept up, as current theoretical and regression intraocular lens power prediction formulas are largely based on adult eyes at axial lengths, anterior chamber depth, and keratometric values much different than those seen in infants. In addition, the adult eye has matured and is no longer growing, whereas the eyes of infants and children may continue to note changes in axial length, keratometric values, and possibly optical characteristics. Another source of error in intraocular lens power selection that is more likely to occur in pediatric patients than in adult patients is inaccuracy in measurement of axial length or keratometric power. A review of current tools and considerations for intraocular lens power prediction in infants and children is presented.

Secondary artisan phakic intraocular lens for correction of progressive high myopia in a pseudophakic child

An 8-week-old infant underwent unilateral cataract extraction and posterior chamber intraocular lens implantation for total cataract in the left eye. After surgery, a residual progressive myopic error was observed, ranging from -4.5 diopters (D) 6 months after the operation to -14.0 D at the age of 3 years. Because of parental noncompliance for contact lens and spectacles use, secondary implantation of Artisan phakic IOL of -14.0 D power was performed. No intra- or postoperative complications were observed. Nine months after this second operation, myopia diminished to -3.25 D.

Development of primary axial myopic anisometropia

Assessment of refractive errors is an integral part of the treatment of ophthalmic problems. This is especially important in pediatric patients for early diagnosis of strabismus and amblyopia. In anisometropic amblyopia, careful monitoring of the refractive error is necessary. The following case history describes a patient who developed myopic axial anisometropia at age one. It suggests that the development of myopic axial anisometropia may be different than our present understanding. We reviewed the literature and found no description of the onset of myopic axial anisometropia.