cryotherapy in ophthalmology

CRYOTHERAPY

CRYOTHERAPYModerator- Dr. Rekha B.K.

Presenter- Devanshu AroraSEMINARSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi1

INTRODUCTIONCRYOTHERAPY(also known as Cryosurgery, cryoabalation, cryocautery & cryogenic surgery)

Is a technique that uses an extreme cold produced by an instrument to freeze and destroy abnormal tissue.

The term "cryotherapy" comes from the GreekCryo- meaning cold, and therapy- meaning cure.

September 09, 2015Department of Ophthalmology, JNMC, Belagavi2

BRIEF HISTORYSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi3

Use of cryotherapy dates back to the 19th century3

September 09, 2015Department of Ophthalmology, JNMC, Belagavi4Other Cryogens are- Nitrous Oxide & Freon

INTRODUCTION OF CRYOTHERAPY IN OPHTHALMOLOGYSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi5

responsible for the advancement of cryoretinopexy surgical techniques & published them In 1964

Application of a cryoprobe to the sclera for 5 seconds was shown to create a white area in the underlying retina and seal retinal tears and holes

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CELLULAR EFFECTS OF CRYOTHERAPYEffects of cryotherapy include:Ischemia caused byvascular stasis andthe destruction of small caliber blood vesselsIce crystal formation inside cells leading to cell wall ruptureDenaturing of lipid- protein complexesOsmotic stressTissue necrosisCellular apoptosis after freezing injury by the buildup of toxic concentrations of solutes inside cells


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The net result is-Cellular dehydrationSolute concentration intracellularly

Simultaneously

This will lead to cellular apoptosis.7

THAW PHASEFor adequate cellular destruction, the thaw phase of cryotherapy is just as crucial.

A slow thaw allows for longer vascular stasis and longer exposure to toxic solute levels within the cell

The effect is enhanced by repeated freeze-thaw cycles, usually performed 2-3 times known as DOUBLE FREEZE THAW TECHNIQUE


SALIENT PRINCIPLES OF CRYO-APPLICATION IN CELLULAR & CLINICAL OPHTHALMOLOGYThe ability of a cryogen to freeze is dependent on its ability to remove heat, which is determined by its boiling point.The ice ball produced by a cryoprobe becomes warmer as distance from the cryoprobe is increased.A rapid freeze and a slow thaw produce the most cell death.The pathologic hallmark of cryotherapy is ischemic necrosis.Large blood vessels are highly resistant to cryoinjury, while microvasculature is susceptible.


In the context of tissue & cellular destruction there are certain-9

VARIOUS CRYOGENSFor Ophthalmological uses the cryogens primarily used for cryotherapy are:Freon (boiling point = 29.8 C to 40.8 C)

Nitrous oxide (boiling point = 88.5 C)

Solid carbon dioxide (melting point = 79 C)

Liquid nitrogen (boiling point = 195.6 C)Boiling point of liquid nitrogen is by far the lowest, making it the most effective in cell destruction.


lower the boiling point, the more freeze destruction will the cryogen be able to cause

Therefore an increasing trend in using liquid nitrogen for cryotherapy in most pathologies.10

EQUIPMENTS FOR CRYOTHERAPYCryoconsole

Appropriately sized cryoprobe for the procedure

Source of electricity to run the cryoconsole


The cryoprobe connects to the cryoconsole with insulated tubing that is part of the probe itself

Equipment used in cryotherapy include:

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Tank of gas(containing the cryogen as liquid form under pressure)It is attached through valves and tubing to the cryoconsole

In all retinal cases, an indirect ophthalmoscope and condensing lens



CRYOPROBEA cryoprobe is a closed system where the cryogen is circulated within a metal probe and the cold probe is applied to the tissue.

Specifically, the probe is supplied with a cryogen from a pressurized source.

For example if the cryogen is liquid nitrogen-It converts to gaseous nitrogen when released & allowed to pass within the probe, cooling the probe to extremely low temperatures.


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Probes with varying tip sizes and angulations have been developed for different applicationsSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi15

However, the appropriate size of tip for cyclocryotherapy has been debetable, because of increased risk of hypotony and phthisis with a large cryoprobe

Many practitioners prefer a 2.5mm tip probe for cyclocryotherapy as it seems to provide a better risk-benefit ratio.15

Cryoprobes for RetinaSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi16


The tip maybe of various shapes image--Different probes may be used depending on the location & size of retinal tear or lesion17

Patient PreparationFor Retinal Cryopexy:Either topical anesthesia or subconjunctival injection of local anesthetic (lignocaine) in the same quadrant as the lesion to be treated.

For conjunctival neoplasms, lid neoplams & trichiasis:Local infiltration of anesthesia is done.

For Peripheral Cryoabalation of the retina or choroid and Cyclocryotherapy for glaucoma:Peribulbar Block should be given.September 09, 2015Department of Ophthalmology, JNMC, Belagavi18

TECHNIQUEBefore beginning, make sure that there is adequate gas in the tank &that connections have been correctly made and tightened.

Proper cooling of the tip should be checked by depressing the foot switch.

After appropriate anesthesia has been instituted, the cryoprobe is applied while still warm to the tissue undergoing treatment.September 09, 2015Department of Ophthalmology, JNMC, Belagavi19

The footswitch is then depressed to allow coolant to flow to the tip.

An ice ball should form at the tissue at the tip.

Once tissue has started adhering to the tip, the probe should not be moved, because of the risk of tearing or breaking the tissue.

The freeze application is limited to the time specified depending on the lesion & then it is allowed to thaw.


Repeat freeze-thaw cyclesDouble freeze-thaw technique for most lesions.20

COMPLICATIONS OF CRYOTHERAPY

Most complications from ocular cryotherapy are related to surgeon inexperience&Prolonged contact of a cryoprobe or cryospray with surface tissue, leading to an over-freeze.


Depending on the tissue undergoing cryotherapy, the most common complications from cryotherapy include:

Transitory uveitis

Temporary chemosis

Subconjunctival hemorrhage

Corneal endothelial damage

Paralysis of extra ocular muscles from cryotherapy over muscle insertion sites

Sector iris atrophy


Although these adverse effects rarely have long-term consequences,Cryosurgery specially with liquid nitrogen should be performed carefully and only after adequate practical experience.


Applications of cryotherapy for specific ocular pathologiesCRYOTHERAPY FOR SURFACE EYE DISEASES:September 09, 2015Department of Ophthalmology, JNMC, Belagavi24

SPECIAL CONSIDERATIONSAs per various studies it was seen that,If the cryoprobe was placed on the surface of the globe for only 2 - 3 seconds, it was a safe amount of time to apply a cold liquid nitrogen cryoprobe without causing undue damage.

A temperature of 25 C at the level of the endothelium will kill these fragile cells, andAn ice ball of 5mm or larger will lead to endothelial cell loss. This would happen if freeze time is kept 5 seconds or more


Therefore, contact time of cryoprobe using liquid nitrogen for treating surface eye neoplasms, should be kept less than 3 secondsPreferably 1-2 secs.25

TRICHIASIS

Cryotherapy may be used as a treatment option for chronic trichiasis.

Cryotherapy is preferred when there are more than one trichiatic lashes together in an area of the eyelid.

Freon or Nitrous oxide is used to destroy the follicles by freezing them.


Treatment modalities for trichiasis include:Manual epilationElectrolysisCryotherapyRadiofrequency epilationArgon Laser photoabalation26

Cryotherapy for trichiasis was first reported in 1997, using a nitrous oxide cryoprobeLocal treatment of eyelids using a double freeze-thaw technique was used with low temperatures reaching -20 C

Success rate is high of more than 90% but complications are common- Eyelid notching & scarring Pigmentary skin changes Destruction of normal eyelashes


BASAL CELL CARCINOMA OF THE EYELIDSIt is a malignant tumor derived from cells of the basal layer of the epidermis.

Up to 50-60% of BCC affect the lower eyelidMedial Canthus is involved 25-30% of times (C/I for cryo)Upper eyelid 15%

Treatment Modalities include:SurgeryRadiotherapyCryotherapySeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi28

Surgical excision with biopsy is the treatment of choice for BCCRadiotherapy is useful in patients who refuse surgery & in the treatment of advanced or recurrent lesions in the medial canthal region.28

Cryotherapy may be used in:Small superficial type of Basal Cell CarcinomaPigmented variety of Basal Cell CarcinomaEyelid notching

Cryotherapy is contraindicated in:Medial canthal lesionsRecurrent Basal Cell Carcinoma

Radiotherapy & Cryotherapy are both contraindicated in:Lesions greater than 1cm in diameterMorphea or Sclerosing type of Basal Cell CarcinomaSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi29

5 types on histopath:Nodular Ulcerative (m/c)Pigmented Morphea or Sclerosing (aggressive & may invade deeply)Superficial typeFibroepithelioma 29

TECHNIQUE FOR BASAL CELL CARCINOMADouble freeze-thaw cycles are used With 45 seconds of freeze for tumors 5mm in size&60 seconds of freeze for tumors >5mm in size followed by slow thaw.

Nitrous oxide probe is used with high flow rate and tip-size 4 x 10 mm of collin type.

Similar technique was used in a study(published in- British Journal of Ophthalmology, 2011Nitrous oxide cryotherapy for Primary Periocular Basal Cell Carcinoma a 5 year follow up)September 09, 2015Department of Ophthalmology, JNMC, Belagavi30

The results suggested that Basal Cell Carcinomas up to 8mm diameter, treated with Nitrous Oxide probe cryotherapy had recurrence rate of 8%30

VERNAL KERATOCONJUNCTIVITIS

The giant papillary changes in VKC are collections of neutrophils, eosinophils, lymphocytes, and other leukocytes surrounding a central vascular core

Cryotherapy aims at killing the central vascular core of giant papillaeSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi31

September 09, 2015Department of Ophthalmology, JNMC, Belagavi32VARIOUS STUDIES FOR CRYOTHERAPY FOR VKCSankarkumar et al. studied 30 eyes of 15 patients with VKC, in 1992 who underwent treatment with carbon dioxide cryogen. Reported recurrence was 3.3% at one year

Jiang et al.(2006) combined resection, cryotherapy, and amniotic membrane transplantation for the treatment of VKC. It was concluded that resection and cryotherapy combined with AMT is an effective & safe treatment for VKC.

Jiang et al slide- 7332

September 09, 2015Department of Ophthalmology, JNMC, Belagavi33Liquid nitrogen cryotherapy (using a cryoprobe) for VKC in 3 eyes was reported in 2008.(F.W. Fraunfelder, Transactions of American ophthalmological Society, Vol 106, 2008.)Giant papillae recurrence was noted after 1 month.Recurrent VKC was noted with a median time of development as 12 months.

Cryotherapy may kill the central vascular core of giant papillae early on (resulting in some positive results after therapy),But the high rate of recurrence may make cryosurgery an ineffective therapy for Vernal kerato-conjunctivitis.

ADJUVANT CRYOTHERAPY WITH PTERYGIUM EXCISSION

Various post-excision, adjuvant treatments have been described in the past, with different recurrence rates: 6% with Conjunctival autograft 13% with Beta-irradiation 29% with Mitomycin-C 53% with excision aloneSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi34

The current definitive therapy for pterygia is surgical removal.Without additional treatment of the surgical bed after excision, pterygia excision is often complicated by recurrence.

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The use of adjuvant liquid nitrogen cryotherapy of the surgical site was studied in both de novo and recurrent pterygia excision by F.W. Fraunfelder (published Cryotherapy for Pterygia, ophthalmology Vol 115, No. 12, 2008)

In this series, after excision of the pterygia, Cryotherapy with a 2mm cryoprobe was performed, with the tip of the cryoprobe in contact with the corneoscleral limbus for approximately 1 second.A double freeze-thaw technique was used. After cryotherapy, the conjunctiva was closed up to the limbus with 6-0 plain gut sutures.September 09, 2015Department of Ophthalmology, JNMC, Belagavi35

In the de novo pterygia group (median follow up of 24.5 months), only 1 out of 15 patients had a recurrent pterygiumResulting in a recurrence rate of 3.3% per year.In the recurrent pterygia group (median follow up of 27 months), 4 out of 6 patients had a recurrent pterygium after treatment,Resulting in a recurrence rate of 29.6% per year.


a) Pterygium before excision and cryotherapy; (b) Appearance of eye 1 year after excision and cryotherapy.

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Thus, liquid nitrogen cryotherapy appears to be an appropriate adjuvant treatment after de-novo pterygia excision to minimize recurrence.

However, recurrent pterygia have NOT been shown to be susceptible to adjuvant liquid nitrogen cryotherapy, with high rates of recurrence despite cryotherapy.


Conjunctival Intraepithelial Neoplasia and Squamous Cell Carcinoma

Conjunctival intraepithelial neoplasia (CIN) is a localized squamous cell neoplasm that is minimally aggressive and confined to the surface epithelium.

If the basement membrane is compromised and invaded by the abnormal cells, then the lesion has progressed to Squamous Cell Carcinoma.


CIN grading is based on the depth of involvement of dysplastic cells:Mild CIN involves 1/3 of the epithelial depthModerate CIN involves 1/2 of the epithelial depthSevere CIN involves full thickness epithelium without invasion beyond the epithelial basement membrane.38

Clinically, CIN and squamous cell carcinoma may present as fleshy, elevated lesion at the limbus.Adjacent corneal epithelium may also be involved.

Early studies using excision followed by nitrous oxide cryoprobes showed relatively good results with a 9% recurrence rate (with 5 years of follow up).

More recently, an optimized technique for excision with No Touch technique and combined cryotherapy with liquid nitrogen has been described.


Squamous cell carcinoma is locally invasive, it rarely metastasizes.

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It includes treatment of the lesion by alcohol epitheliectomy and partial scelroconjunctivectomy using the no-touch technique,

followed by intra-operative double freeze-thaw cryotherapy applied to the edges of the remaining bulbar conjunctiva & the scleral base if there was episcleral adhesion of the tumor.



Start- 1:40End- 5:1041

In a study of 60 patients with CIN and conjunctival squamous cell carcinoma treated with excision and cryotherapy with the same technique, (by M. Tunc, et al.)

After a mean follow up of 56 months, the rate of recurrence was 4.5% for CIN and 5.3% for squamous cell carcinoma


Primary Acquired Melanosis andMelanoma of the Conjunctiva Primary acquired melanosis (PAM) of the conjunctiva is a pre-malignant transformation of melanocytic cells in the conjunctiva.

It usually manifests in the middle age, as a unilateral, superficial, solitary patch or diffuse pigmentation of the bulbar, forniceal and palpebral conjunctiva.

MANAGEMENT Conjunctival PAM is usually managed by simple observation if it is limited in extent and not rapidly progressive.


Prominent or progressive PAM lesions are usually Excised (if small) or Biopsied (if too large to be excised)September 09, 2015Department of Ophthalmology, JNMC, Belagavi44

Presence or absence of Intra-epithelial Melanocytic Hyperplasia & Atypical Melanocytes

As there are high chances of malignant transformation leading to conjunctival Melanoma.44

Double freeze-thaw cycles of cryotherapy are applied.

Excision & Cryotherapy of Primary Acquired Melanoma has proven to be an effective treatment but recurrences can occur.

In a recent report of over 100 cases of PAM treated with excision and cryotherapy after a 3 year follow-up, the reported rate of PAM recurrence was 27%, with 3% progressing to Melanoma.

(J.A. Shields, et al. published- Transactions of the American Ophthalmology society, Vol105, 2007)


CONJUNCTIVAL MELANOMAIt can arise: De novo From a preexisting nevus or From Primary Acquired Melanoma (75% cases)

Conjunctival melanoma appears as a pigmented, fleshy, mass located in the bulbar, forniceal or palpebral conjunctivaand may exhibit a prominent feeder vessel



Para-limbal conjunctival melanoma 47

Treatment of Conjunctival Melanomas varies according to the extent and location of involvement:

Melanomas involving the bulbar conjunctiva & cornea September 09, 2015Department of Ophthalmology, JNMC, Belagavi48

As for squamous cell carcinomaConj lesions extending into the globe- enucleationExtending to the orbit- exenterationDisseminated melanomas/metastatic- systemic chemotherapy.48

September 09, 2015Department of Ophthalmology, JNMC, Belagavi492. CRYOTHERAPY FOR INTRAOCULAR PATHOLOGY:Cryoextraction of CataractCyclocryotherapyCryotherapy for intra-ocular tumorsRetinal Breaks & DetachmentRetinopathy of Prematurity

CRYOEXTRACTION OF CATARACT

Cryotherapy was widely used for cataract extraction in the 1970s when Intra-capsular cataract extraction was the treatment of choice for senile cataracts.

Since now Intracapsular cataract extraction is not performed, cryotherapy for lens extraction is no more required


TECHNIQUE:A 12-14 mm incision used to be given, the surface of the lens was dried and cryoprobe tip was applied to the lens capsule.

The cryogen was then released to pass into the tip causing the tip to cool rapidly and adhere to the lens capsule

Once adhesion is complete, the lens can be removed by pulling gently on the cryoprobeSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi51

** indication for icc/cryoextraction now?51


CYCLOCRYOTHERAPYCyclocryotherapy is a cyclodestructive procedure which aims at destroying the secretory epithelium of the ciliary body.

Indications:Refractory glaucoma with poor vision or poor visual potentialPain relief due to elevated IOP in a painful blind eyeNeovascular GlaucomaIf conventional glaucoma surgery fail to control IOPSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi53

Surgical technique of Cyclocryotherapy:

Performed usually under peribulbar anesthesiaA circular and convex retinal cryoprobe (3mm or 4mm tip) is applied directly on the intact conjunctival surface.The edge of the tip is placed 1-1.5mm from the limbus for 1 minute, thus bringing the center of tip directly over cilliary bodyThe ice-ball is allowed to thaw slowly, rather than using irrigation, to allow maximal effect.September 09, 2015Department of Ophthalmology, JNMC, Belagavi54 Cycloabalation can be achieved by

Cyclocryotherapy Cyclophotocoagulation with laser


Complications include:Reduced visual acuity, uveitis, hemorrhage& phthisis bulbi

To reduce the complication rate (particularly phthisis bulbi), the treatment is usually limited to one application at each clock hour (six in total) over 180

All the complications are less common with Trans-scleral Cyclophotocoagulation(TCP) Laser therapy which is a better alternative to cyclocryotherapy.September 09, 2015Department of Ophthalmology, JNMC, Belagavi56

September 09, 2015Department of Ophthalmology, JNMC, Belagavi57Post-op regimen:Atropine eye drops and an antibiotic-steroid combination are prescribed.All glaucoma medications are continued post-operatively

The full effect of treatment may take 2-4 weeks to become manifest, so a second treatment is not considered until 1 month has passed.

If required, the same area may be retreated, or another quadrant may be included.

INTRA-OCULAR TUMORSThe advantage of cryotherapy to treat intraocular tumors is the ability to treat trans-sclerally.The damage to the sclera is minimal and negligible while the intraocular tumor is destroyed.

Indications:RetinoblastomaRetinal Capillary HemangiomasVasoproliferative tumorsSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi58

RETINOBLASTOMAVery small tumors, not more than 3mm in diameter and 2mm thickness can be treated by cryotherapy alone.

Vitreous seeds are usually not treatable with cryotherapy unless they are lying in the immediate vicinity of the tumor.

Cryotherapy, however in Retinoblastoma is usually used for consolidation of the tumor after chemotherapy.

Tumor recurrences when small can also be treated with cryotherapy.September 09, 2015Department of Ophthalmology, JNMC, Belagavi59

PROCEDURE FOR INTRA-OCULAR TUMORS

Intra-ocular tumors are treated using a 2.5 mm tip retinal cryoprobe.

Lesions located anteriorly are easily treated with cryo since conjunctiva need not be opened.

For tumors located posteriorly, limited conjunctival opening is made to make the probe reach posteriorly.


With the indirect ophthalmoscope view, indentation caused by the probe tip is positioned under the center of the lesion and freezing is commenced.


Freezing is done till the ice ball totally encloses the tumor mass.

The probe is allowed to defreeze completely before freezing again.The cycle is repeated thrice

Topical steroids are given for a few days.

Complications:Retinal edema occurs frequentlyLess frequently Secondary Retinal DetachmentRetinal Hemorrhages


RETINAL CRYOPEXYIt is a procedure employing cryotherapy to induce a chorioretinal scar.

It is used for the treatment of retinal tears & detachments.

Retinal tears may arise from trauma or traction from the overlying vitreous.Retinal tears may then allow fluid influx between the neurosensory retina and the RPE, causing further extension of the separation and leading to a retinal detachment.


PROPHYLACTIC MANAGEMENT OF RETINAL BREAKS3 Modalities: Cryotherapy Laser photocoagulation Scleral Buckling

Retinal tears that should be treated include:Symptomatic tearHigh MyopesAny break with subretinal fluid more than 1DDHistory of RD in fellow eyeHorse-shoe shaped tearsSeptember 09, 2015Department of Ophthalmology, JNMC, Belagavi64

Cryotherapy is preferred over laser photocoagulation in: Hazy ocular media Peripherally located tears near the ora-serrata Small pupils


Cryotherapy may also be used intraoperatively when scleral buckling is done for the treatment of retinal detachment.

In a recent RCT, published 2010 (by RP Lira at al.) patients undergoing scleral buckling for rhegmatogenous retinal detachments along with either intra-op cryotherapy or post-op laser retinopexy (1 month later)The reattachment and post-operative complication rates were similar in both groups


RETINOPATHY OF PREMATURITY ROP is an ischemic retinopathy of premature and low birth weight infants.

The development of retinal vasculature begins during week 16 of gestation and can progress to the final weeks of gestation.

Premature birth, in conjunction with subsequent iatrogenic oxygen supplementation, halts and alters normal retinal vasculature development, leading to the onset of ROP and abnormal neovascularization.


First use of cryotherapy to prevent progression of ROP was reported in 1978.This revolutionized the treatment of ROP

In this technique, trans-scleral cryotherapy is used to ablate areas of avascular retina and thereby prevent further neovascularization.

In 1988, the first multicenter randomized trial of cryotherapy for treatment of ROP (the CRYO-ROP study) was reported.9751 less than 1251gm babies were studied across 23 centers & one eye was randomized for cryotherapy.


Five-year data from the CRYO-ROP study supported the safety and efficacy of cryotherapy treatment of ROP.

Ten-year data from the CRYO-ROP study showed long-term value from cryotherapy in preserving visual acuity in eyes with ROP.

Cryotherapy has been shown to be an effective treatment for ROP stage 3+

Cryotherapy has been employed to achieve peripheral retinal ablation for ROP since the 1970s but now has largely been replaced by laser photocoagulation.September 09, 2015Department of Ophthalmology, JNMC, Belagavi69

In a large randomized comparison of laser photocoagulation with cryotherapy (25 infants followed for at least 4 years), eyes treated with laser were significantly more likely to have visual acuity of 20/50 or better and were significantly less myopic.The advantage of laser is greatest for eyes with zone 1 disease: favorable anatomic results have been reported in 8385% of all eyes, versus only 25% of eyes with zone 1 disease treated with cryopexy. 69

CONCLUSION Cryotherapy in ophthalmology has a rich history and continues to be an important supplement in the treatment of ophthalmic pathology.

The use of cryotherapy in ophthalmology has helped advance maturing fields, while in other instances revolutionized patient care(including ocular surface malignancies).

Further applications of cryotherapy in eye disease continue to emerge.



REFERENCESOphthalmology 4th edition- Yanoff & Duker

Clinical OphthalmologyA Systematic Approach 7th edition (by Jack J Kanski)

American Academy of Ophthalmology(AAO)BSCS section 12

Indian Journal of Ophthalmology Vol.63, Issue-3

Open Journal of Ophthalmology, 2013, 3, 103-117

Internet http://www.medscape.comhttp://www.keelerusa.comFebruary 18, 2015Department of Ophthalmology, JNMC, Belagavi72

Technique- 19

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VKCJiang et al.(2006) combined resection, cryotherapy, and amniotic membrane transplantation for the treatment of VKC.In this study of 16 eyes, fourteen eyes (87.5%) were symptom-free 1 month after surgery with no evidence of VKC on examination.Recurrence of VKC was observed in 2 eyes (12.5%) after cryotherapy. It was concluded that resection and cryotherapy combined with AMT is an effective & safe treatment for VKC.


cryotherapy in ophthalmology

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