Management of Congenital Cataract in Sub-Saharan Africa



Fig. 11.1
(a) Red Reflex examination in a child. (b) Child with Cataract in the left eye



Evidence from Asia has shown that the opportunity is either not taken or when taken the child is not referred for proper surgical management, thus causing long delays before presentation for surgery [8]. Another study from Tanzania indicated quite limited knowledge about childhood blindness among public health workers; only 50 % realizing that pediatric cataract needed urgent surgery [9]. Another approach, used very successfully in Bangladesh [10], uses lay people (termed key informants) in the community who volunteer to take responsibility for identifying blind children and receive a short training. This has been replicated in SSA with variable success [2, 1113]. Screening programs (see Fig. 11.1a) looking for leucocoria (see Fig. 11.1b) may also pick up retinoblastoma and hence save lives



11.3 Etiology


The etiology/causation of most congenital cataract seen in SSA is unclear/idiopathic. One series suggested a family history in about 20 % similar to western populations [14]. There is also some clinical evidence for the importance of congenital rubella [1517]. There are no rubella vaccination programs in SSA or any facilities for serological testing for evidence of congenital rubella. Rubella has also been reported as a common cause (15–20 %) in other developing countries [18].

Congenital cataracts that occur in both eyes are associated with a systemic disease approximately 5–10 % of the time [19]. For bilateral cataracts, it is important to determine if there is a systemic association that may need to be treated and that may increase anesthetic risk.


11.4 Clinical Assessment


History and examination are performed as anywhere in the world and include questions about family history, age of onset, any infections during pregnancy and questions about general health and development.


11.4.1 Examining the Eye


Although B-scan ultrasonography is increasing available, if there is dense leukocoria with calcific anterior capsule changes plus or minus partial resorption of the lens, a differential diagnosis of retinoblastoma may need to be considered. Evidence of traction on the ciliary processes, present in persistent fetal vasculature associated with cataract, and not seen in retinoblastoma can be helpful here. If portable slit lamps are not available an indirect ophthalmoscope (see Fig. 11.2) can be used with the condensing lens head close to the eye for a reasonably good anterior segment examination

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Fig. 11.2
Dr. Furahini Godfrey Mndeme examining 1 year old with bilateral cataract


11.4.2 Visual Assessment


Visual assessment in milder cataracts is essential in determining whether surgery is needed and doctors and other health professionals need to be trained in the basics of visual acuity assessment in preverbal children such as preferential looking. For older children, logMAR, Snellen, Allen, Lea, HOTV, numbers, tumbling E have all been used. Kay’s pictures are acuity tests that depend on the child recognition and naming, which may depend on previous cultural and educational exposure. Pictures tests such as LEA symbols, have been found to be culturally relevant to most cultures and can be used for older illiterate children. Smartphone apps to test visual acuity have been utilised successfully in adults and children (both recognition and detection acuity tests) in rural African settings also aiding data collection and geographic monitoring of patient location using linked GPS facilities [20]


11.4.3 Examining the Child


General examination should include assessment of hydration status, nutritional status, posture and gait, color of mucous membranes, lymph node assessment, pattern of breathing, temperature, presence of finger clubbing and any other obvious clinical abnormality. Children suspected of an underlying systemic disorder should be assessed by a pediatrician. All children must be assessed by an anesthetist. Most generally healthy children require only a full blood count (to look for malaria related anemia). Otherwise only clinically indicated investigations are needed with appropriate treatment provided where necessary. Specific investigations for suspected systemic diseases should be taken by the pediatrician/anesthetist carrying out this assessment.


11.5 Surgical Treatment


The same principles of management apply as elsewhere: early surgery, early optical rehabilitation, and maintenance of a clear visual axis. However these can be more difficult to achieve in SSA. Problems caused by late presentation have already been discussed. In addition contact lenses are not a feasible option for optical rehabilitation leaving a choice of intraocular lenses or glasses. Sometimes, because of geographic remoteness, surgery is carried out by adult cataract surgeons who do not have access to foldable lenses, vitrectomy machines or children’s glasses, making early optical rehabilitation and maintenance of a clear visual axis (for which primary posterior capsulotomy and anterior vitrectomy is essential) impossible. The World Health Organization has encouraged referral of children with cataract to specialist centers which they term Childhood Eye Health Tertiary Facilities (CEHTFs) [21] but the scarcity of these centers throughout the continent means that this is not often possible.

The following are technique modifications that the authors have found helpful in a setting of restricted financial resources and limited follow up.


Wound Construction and Closure

Use a scleral tunnel instead of a clear corneal incision. This enables the use of non-absorbable sutures, which are cheaper and more widely available. These can then be covered by the conjunctiva to avoid exposure. Corneal paracenteses can be sealed with hydro-inflation. In this way repeated anaesthetic exposure to remove exposed corneal sutures or the alternative risk of infectious keratitis and endophthalmitis from suture abscesses is reduced. The scleral tunnel and pars plana/plicata incision for anterior vitrectomy (if this approach is used) can be closed with a single cross suture.


Capsulorhexis

Creation of a continuous curvilinear capsulorhexis (CCC) is ideal but can be difficult in the absence of high quality viscoelastics, capsule dyes and squeeze handle rhexis forceps. If these are not available and CCC proves challenging, vitrectorhexis is a useful alternative. The quality/consistency of the anterior capsule in late presenting mature pediatric cataracts can also be an obstacle to CCC and again vitrectorhexis can be helpful.

The anterior capsule is breached with an MVR blade and then the vitrector is used at low cut rate and aspiration rate, either from above the capsule (with the port downwards) or from below the anterior capsule (with the port upwards) and a near circular capsulotomy is slowly nibbled outwards. Sometimes with mature cataracts this technique is not possible because the anterior capsule which can be under some tension splits out peripherally in a linear fashion as soon as it is punctured with an MVR blade. However this split usually provides an adequate capsulotomy itself – when the IOL is inserted the leaves of the anterior capsule retract backwards leaving an adequate gap. This can then be enlarged with the vitrector if necessary.


Use an IOL Wherever Possible

Long term use of contact lenses is not feasible and glasses quickly lost or broken, therefore IOLs represent the best chance of optical rehabilitation in this setting. A study in Tanzania showed that the use of foldable lenses was associated with less post-operative astigmatism [4].


Primary Posterior Capsulotomy and Anterior Vitrectomy

Because return for followup is usually uncertain, we are more aggressive and perform this on all children under age 10 years (unless they live locally, are likely to attend for follow-up and would be compliant with a table mounted YAG capsulotomy). Surgical capsulotomy and anterior vitrectomy can be performed, as anywhere else, before or after IOL implantation and via an anterior or posterior approach. Vitrectomy machines are not as readily available or as well maintained as in more developed settings, but this situation is improving. Pediatric cataract surgery should not be performed without a functioning vitrector. The authors have successfully used a budget vitrector made by Geuder (Vitron 2020), which has a manual syringe driven suction mechanism when conducting pediatric cataract surgery in an outreach setting.

The placement of the sclerotomy site for pars plana posterior capsulotomies is shown here.

Sclerotomy sites for par plana vitrectomy port (measured in mm from the limbus) [22].



Table 11.1





















Less than 6 months

1.5

6–12 months

2

1–2 years

2.5

2–6 years

3

>6 years

3.5


11.6 Biometry


Several options can be used to calculate the dioptric strength of the intraocular implant required. The most accurate involves keratometry and A-scan ultrasound. If keratometry is not available, the Ks can be estimated using either the axial length measurements or the child’s age. Alternatively an average K can be used (see Tables). It is possible to use the axial length measurements alone and if all else fails the age of the child, but this should only be as a last resort. It is important to under-correct the child to allow for growth of the eye. The following are taken from the paediatric ophthalmology fellowship handbook [22] at CCBRT.

Intraocular lens calculation by age alone (least favoured method)





Table 11.2































Age

Power

3 months

27

6 months

26

1 year

24

2 year

22

3 year

22

4 year

22

5 year

21

Intraocular lens calculation using axial length





Table 11.3

























AL

IOL power

17

+28

18

+27

19

+26

20

+24

21

+22

Intraocular lens power calculation using biometry and SRK formula





Table 11.4








Age

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Nov 21, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Management of Congenital Cataract in Sub-Saharan Africa

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